micronutrient-efficient genotypes for crop yield and nutritional...

Agron Sustain Dev 30 (2010) 83ndash107ccopy INRA EDP Sciences 2009DOI 101051agro2009017

Review article

Available online atwwwagronomy-journalorg

for Sustainable Development

Micronutrient-efficient genotypes for crop yield and nutritional qualityin sustainable agriculture A review

Amir Hossein Khoshgoftarmanesh1 Rainer Schulin2 Rufus L Chaney3 Bahareh Daneshbakhsh1Majid Afyuni1

1 Department of Soil Science Isfahan University of Technology 84154 Isfahan Iran2 Institutes of Terrestrial Ecology ETH Zurich Universitaetstr 16 8092 Zurich Switzerland

3 USDA-Agricultural Research Service Environmental Management and Byproduct Utilization Laboratory Building 007 BARC-WestBeltsville MD 20705 USA

(Accepted 29 April 2009)

Abstract ndash About 4 billion people will be added onto the present population by 2050 To meet further demand for food agricultural productionshould increase on the existing land Since the Green Revolution higher crop production per unit area has resulted in greater depletion ofsoil phytoavailable micronutrients while less attention has been paid to micronutrients fertilization Now micronutrient deficiency has becomea limiting factor for crop productivity in many agricultural lands worldwide Furthermore many food systems in developing countries cannot provide sufficient micronutrient content to meet the demands of their citizens especially low-income families There are several solutionssuch as soil and foliar fertilization crop systems application of organic amendments to correct micronutrients deficiency and to increase theirdensity in edible parts of plants This review article presents (1) agronomic approaches to improve crop yield and micronutrient content of foodcrops and (2) genotypic variation in uptake and accumulation of micronutrients Considering ecological concerns cultivation and breedingof micronutrient-efficient genotypes in combination with proper agronomic management practices appear as the most sustainable and cost-effective solution for alleviating food-chain micronutrient deficiency Micronutrient-efficient genotypes could provide a number of benefitssuch as reductions in the use of fertilizers improvements in seedling vigor and resistance to abiotic and abiotic stresses Using bioavailablemicronutrient-dense staple crop cultivars can also be used to improve the micronutrient nutritional status of human

micronutrients nutrient efficiency biofortification stress-tolerance indicators

1 INTRODUCTION

The worldrsquos population is estimated to increase from 6 bil-lion to about 10 billion by 2050 To meet the food demandof the growing world population a large increase in food pro-duction is required At the same time the increases in worldpopulation will result in serious pressure on the existing agri-cultural land through urbanization and intensive cultivation(Alexandratos 1995 Byrnes and Bumb 1998) It has beenestimated that to supply enough food for the world populationin 2020 annual cereal production needs to increase by 40from 1773 billion tons in 1993 to nearly 2500 billion tons in2020 (Rosegrant et al 1999 2001) About 85 of the increasein total cereal demand will occur in the developing countries

There are two strategies to increase food production (a) toexpand the agricultural area and (b) to enhance crop yields perunit area The expansion of agricultural area is limited due to

Corresponding author amirhkhoshcciutacir

lack of suitable lands urbanization degradation of soils andincreasing water scarcity (Brown 1997) To meet the furtherdemand for food agricultural production must increase on theexisting land This means that more crop food production mustbe achieved per unit of the presently available arable land

Since the ldquoGreen Revolutionrdquo intensive cropping cultiva-tion of high-yield genotypes improved agricultural mecha-nization production of macronutrient fertilizers with low im-purities of trace elements and using modern irrigation systemshas resulted in higher crop production per unit area and greaterdepletion of soil phytoavailable micronutrients

Losses of micronutrients through erosion leaching limingof acid soils decreased proportions of farmyard manure com-pared to chemical fertilizers and use of marginal lands forcrop production are other factors that have increased the inci-dence of micronutrient deficiencies in agricultural soil world-wide (Fageria et al 2002) Micronutrient deficiency prob-lems are also exacerbated by the high demand of modern crop

Article published by EDP Sciences

84 AH Khoshgoftarmanesh et al

cultivars Accordingly low levels of micronutrients have beenreported on many crops grown in different countries (Cakmaket al 1996 Fageria 2000a Galratildeo 1999 Graham et al1992 Grewal and Graham 1999 Martens and Lindsay 1990)Therefore micronutrient deficiency has become a limiting fac-tor for crop productivity in many agricultural soils In orderto obtain the genetic potential yields of crops correcting mi-cronutrients deficiencies is necessary

On the other hand agricultural practices have almost al-ways targeted higher crop yield production while minimizingcosts In addition nutrient output of farming systems has neverbeen a goal of either agriculture or of public policy Thus theincrease in crop yield in many agricultural systems as a resultof chemical fertilizer application has been accompanied withreduced micronutrients concentrations in the edible parts ofdifferent crops So that already many food systems in devel-oping countries can not provide sufficient micronutrients con-centrations to meet the demands of their people especially low-income families (ACCSCN 1992 1997 2000 Combs et al1996 Combs and Welch 1998 McIntyre et al 2001 Welchet al 1997 Welch 1998)

Recently mid 1980s the nutrition community reportedthe global significance of micronutrient malnutrition (Allen2000) In 2001 fighting micronutrient malnutrition was con-sidered an integral component of three of the eight MillenniumDevelopment Goals (MDGs) of the General Assembly of theUN to alleviate the worldrsquos greatest health and poverty issuesby 2015 (United Nations General Assembly 2000) The fo-cus of improving the micronutrient quality of crops notes thedensity of bioavailable micronutrients in crops as consumed inorder to take into account crop factors which increase or de-crease the bioavailability of crop micronutrients (see below)For example phytate in grains is well known to inhibit absorp-tion or utilization of crop Zn by humans and livestock suchthat grain phytate must be considered whenever the quality ofgrain Zn for human use is considered

Deficiencies of iron zinc vitamin A and iodine not onlycompromise the immune system but can irreversibly retarddevelopment in infancy Deficiency of any of these in a preg-nant or lactating woman can result in subclinical mental re-tardation in children Such children may be less fit to controltheir environment and to provide for their own food securityin later life to compete for better education and for higherlevel jobs within their society Vitamin A deficiency can leadto poor night vision eye lesions and in severe cases perma-nent blindness increased illness and death from infectionsIodine deficiency can cause goiter mental retardation braindamage and reproductive failure Iron deficiency can causenutritional anemia problem pregnancies stunted growth andlower resistance to infections long-term impairment in mentalfunction decreased productivity and impaired neural develop-ment Zinc deficiency can cause growth retardation delayedskeletal and sexual maturity dermatitis diarrhoea alopeciaand defects in immune function with resulting increase in sus-ceptibility to infection

Several approaches such as soil and foliar fertilization im-proved crop systems application of soil amendments and or-ganic nutrient sources are possible to correct micronutrients

deficiency and to increase their density in edible parts ofplants Considering ecological concerns sustainable agricul-ture is looking for more environmental-friendly and cost ef-fective approaches with low input of energy and chemicalsAmong different strategies applied for correcting micronutri-ent deficiency in the food chain from plant to human themost sustainable solution particularly for developing coun-tries seems to be cultivation and breeding of micronutrient-efficient genotypes in combination with proper agronomicmanagement practices

Nutrient efficiency and nutrient-efficient genotypes havebeen defined in different ways (Stewart et al 2005 Fageriaet al 2008) Definitions of nutrient efficiency generally canbe divided into those emphasizing crop productivity and thoseemphasizing the internal plant nutrient requirement (Gourleyet al 1994) With regard to yield parameters nutrient ef-ficiency has been defined as the ability to produce a highplant yield in a soil that would otherwise limit the produc-tion of a standard genotype (Marschner 1995) Other defi-nitions of nutrient efficiency also referred to as lsquoagronomicefficiencyrsquo include the amount of shoot production per unitof nutrient applied (Caradus 1990 Sauerbeck and Helal1990) Nutrient efficiency has also defined as yield responseper unit of added nutrient or of nutrient in the crop shoots(Baligar et al 1990 Blair 1993 Thung 1988) This pa-per will briefly discuss some aspects of using and developingmicronutrient-efficient crop plant genotypes as a sustainableand cost-effective method for alleviating food-chain micronu-trient deficiency malnutrition of humans

2 IMPROVING CROP YIELD

Mineral nutrients have played an important role in enhanc-ing crop production since the beginning of the green revolu-tion According to Borlaug and Dowswell (1993) nearly halfof the increase in crop yields during the 20th century was dueto chemical fertilizer application Generally improving the nu-tritional status of plants by applying fertilizers and maintainingsoil fertility has been the critical step in doubling food produc-tion both in developed and developing countries (Loneragan1997) The increase in crop production has been mainly re-sulted from the application of N-P-K fertilizers (Brady andWeil 2002) Since 1950 application of N-P-K fertilizers hasbeen rapidly increased in agricultural lands while less attentionhas been paid to micronutrients fertilization Further highercrop production per unit area depleted greater amount of mi-cronutrients from soils Now micronutrient deficiency is a lim-iting factor for attaining greater crop yields in many cultivatedsoils

Accordingly micronutrient deficiency has been reportedwidely in plant crops grown in different countries For ex-ample Fe deficiency in crops have been reported for vari-ous regions of Europe east India Bangladesh Malta TurkeyZambia and Mexico (Sillanpaa 1982) Indonesia (Katyaland Vlek 1985 Welch et al 1991) several North Centraland South American countries (Leon et al 1985) Australia

Micronutrient-efficient genotypes for crop yield and nutritional quality in sustainable agriculture A review 85

and most Mediterranean and west African countries (Donaldand Prescott 1975)

Zinc-deficient soils are widespread in Mediterranean coun-tries (Cakmak et al 1997b Khoshgoftarmanesh et al 2004a)Australia (Donald and Prescott 1975 Sillanpaa and Vlek1985) China (Takkar and Walker 1993) Africa (Cottenieet al 1981) Asia (Katyal and Vlek 1985 Welch et al 1991)and North and South America (Fageria 2000b Lopes andCox 1977) Some crops (maize rice) are especially suscep-tible to Zn deficiency in most countries where they are grown

Manganese deficiency has also been reported in soils of theUnited States (Reuter et al 1988) Central and South Amer-ica (Leon et al 1985) Europe (Welch et al 1991) semiaridregions of China India southeast and western Australia andmany African countries (Welch et al 1991)

The importance of certain trace elements for optimumgrowth and development of plants has been reported forthe last century (Barker and Pilbeam 2007 Cakmak 2002Marschner 1995) Up to now several trace elements (B BrCl Co Cu F Fe I Mn Mo Ni Na Rb Si V and Zn) areknown to be essential for certain plants Several nutrients havebeen shown necessary only for a few species (Al I Na SiRb Ti V F Br) and others are known to have stimulating ef-fects on plant growth although their functions are not yet rec-ognized (Barker and Pilbeam 2007) The essential micronu-trients are those that their specific biochemical roles cannotbe substituted by other elements In the absence of adequateamounts of these elements inside plant tissues crop growthand metabolic cycles will be impaired

Several studies have reported the significant reduction ingrowth and yield of different plant species in soils deficient inFe Mn Zn Cu B and other micronutrients (Cakmak et al1998 Kalayci et al 1999 Khoshgoftarmanesh et al 2004ab 2006a b 2007 Khoshgoftar and Hajimozaffari 2006)Therefore correcting micronutrient deficiency through appro-priate approaches is necessary to achieve higher crop yields

3 CROP QUALITY AND HUMAN HEALTH

The increase in food production to prevent starvation andmalnutrition was the main goal driving the agricultural ldquoGreenRevolutionrdquo during the latter half of the 20th century (Welchand Graham 1999) In parallel to increase in crop yield inmany agricultural systems as a result of chemical fertilizerapplication and improved agronomic practices micronutrientscontents in the edible parts of different crops were reducedto levels lower than that of the traditional crops Thus manyfood systems in developing countries can not provide suffi-cient micronutrient contents to meet the demands of their peo-ple especially low-income families (ACCSCN 1992 19972000 Combs et al 1996 Combs and Welch 1998 McIntyreet al 2001 Welch et al 1997 Welch 1998) Humans needtrace elements in sufficient levels to sustain life There arealso some dietary substances such as phytate that affect nu-trients bioavailability and as a result human nutritional sta-tus (ACCSCN 1992 1997 2000 Combs et al 1996 Combs

and Welch 1998 McGuire 1993 Welch et al 1997 Welch1998)

Micronutrient malnutrition or hidden hunger now affectsmore than 40 of the worldrsquos population (United NationsAdministrative Committee on Coordination-Subcommittee onNutrition 1992) The consequences of micronutrient deficien-cies are mostly found among women infants and childrenfrom poor families in developing countries (Buyckx 1993Ramalingaswami 1995 World Health Organization 1992Mason and Garcia 1993) However micronutrient malnu-trition is not restricted to developing countries and is alsowidespread in well-developed industrialized countries (Cobiacand Baghurst 1993 US Department of Health and HumanServices 1990)

There has been a huge increase in the number of peoplesuffering from micronutrient malnutrition over the last fourdecades For example Fe deficiency anemia has grown fromabout 30 of the worldrsquos population in the 1960s to over 40during the late 1990s It has been estimated that over 37 and1 billion people are at the risk of iron and iodine deficiencydisorders respectively In addition Zn Se vitamin A vita-min C vitamin D and folic acid deficiencies are widespreadamong populations especially in developing countries (Combset al 1996 World Health Organization 1999) Many zinc nu-trition specialists believe that zinc is as important as iron de-ficiency (Gibson 1994 Gibson et al 2008) Copper boronmanganese chromium and lithium are other micronutrientsthat are needed for nutrient balance

31 Consequences of micronutrient deficiencies

Impaired immune function increased mortality and mor-bidity rates lower worker productivity diminished intellectualperformance lower educational attainment a lower livelihoodhigher birth rates lower standard of living performance andincreased rates of chronic diseases including coronary heartdisease cancer and diabetes are some consequences of mi-cronutrient hidden hunger (Pinstrup-Andersen 1999 Sanghvi1996 Welch and Graham 2000)

Micronutrients malnutrition increase human susceptibilityto infections and is the most important risk factor for the dis-ease in developing countries (Brabin and Coulter 2003 Foodand Agriculture Organization of the United Nations 2004Murray and Lopez 1997 Black 2003) Anemia problempregnancies stunted growth lower resistance to infectionslong term impairment in mental function decreased productiv-ity and impaired neural development are some consequencesof iron deficiency Zinc deficiency may result in growth re-tardation delayed skeletal and sexual maturity dermatitis di-arrhea alopecia and defects in immune function with result-ing increase in susceptibility to infection (Pinstrup-Andersen1999 Welch and Graham 2000)

32 Nutrient bioavailability

The nutritional quality of a diet can be determined based onthe concentration of individual nutrients as well as interactions


of other elements promoters and antinutrients which affectbioavailability of micronutrients In fact the degree to whicha nutrient is absorbed from the diet depends on antinutrientscontents eg phytate tannins and antivitamins (Graham et al2000) High levels of antinutrients including phytate and tan-nins in the diet reduce the bioavailability of micronutrientsincluding Fe and Zn while promoters such as vitamin A orβ-carotene and vitamin C enhance micronutrients bioavailabil-ity in humans (Garcia-Casal et al 1998) Phytate is an impor-tant antinutrient to zinc absorption Phytate is especially highin cereal grains Depending on the plant genotype about 70 to90 of the total phosphorus in whole grain is in the form ofphytate (OrsquoDell et al 1972) Other antinutrients are of lesserimportance in cereals

Another factor affecting the bioavailability of micronutri-ents is interaction with other nutrients For example interac-tions between vitamin A (retinol) and zinc has been found inthe late 20th century (Christian and West 1998 Solomonsand Russell 1980) Synergistic and antagonistic interactionsamong chemically similar metal cations have been character-ized in both plants and animals (Hill and Matrone 1970) Sucha synergistic effect strongly indicates that breeding for staplesthat are dense in both iron and zinc is required in order to ef-fectively address iron-deficiency anemia It has been reportedthat the anemia could be corrected using vitamin A but notiron supplementation (Hodges et al 1978)

Cereal-based foods with low concentrations and reducedbioavailability of micronutrients have been considered a ma-jor reason for the widespread deficiencies of Zn and Fe in de-veloping countries (Graham et al 2001 Welch and Graham1999) Thus it is essential to find sustainable approaches toproduce food supplies adequate in quantity and proper nutri-tional quality

4 CORRECTION OF MICRONUTRIENTDEFICIENCY

41 Fertilizer application

Alleviation of micronutrient deficiencies to improve cropyields is difficult due to large temporal and spatial variation inphytoavailability of soil micronutrients (Brennan and Bolland2006 Shaver et al 2007) The easiest and most straightfor-ward practice to correct micronutrient deficiency is to applymicronutrient fertilizers Soil application of fertilizer is eco-nomically more affordable However in soils with high pHmost of soil-applied micronutrients will become unavailablefor plant uptake within a few years (Martens and Westermann1991) The loss in residual effect of soil-applied nutrient re-quires adding more fertilizer to maintain a sufficient level ofphytoavailable element although total soil element contentsare still high and actually increasing from application to ap-plication Increased total soil metal may create problems ofmicronutrients losses or toxicity in the future especially un-der conditions that mobilize soil metal such as soil acidifica-tion Furthermore soil application of fertilizers is not alwaysa useful approach to increase micronutrients concentrations in

cereal grain Many studies reported minimal or no increases ingrain micronutrient content with increasing soil application ofmicronutrient fertilizers even when yield was increased

Applied soluble micronutrients fertilizers become ineffec-tive rather rapidly as the dissolved metals react with soil min-erals and organic matter In comparison with inorganic fer-tilizers synthetic and natural chelates have the advantage ofkeeping the applied nutrient in solution in a less reactive formChelates are particularly appropriate for applications of Znand Fe to alkaline and calcareous soils Soil application ofinorganic Fe fertilizers to Fe-deficient soils is usually inef-fective because of rapid conversion of soluble Fe into plant-unavailable solid Fe(III) forms In contrast an application ofsynthetic Fe-chelates for correction of Fe deficiency is effec-tive (Wallace and Wallace 1982) for a longer period or actu-ally long enough to support one crop of tree fruits which arecommonly fertilized with Fe-chelates

The effectiveness of various synthetic and natural chelateshas been widely investigated (Alvarez and Gonzalez 2006Gonzalez et al 2007 Prasad and Sinha 1981) Despite theireffectiveness application of chelates is generally expensive(Wallace and Wallace 1982) and is likely to be even more un-economic if the aim is to increase micronutrient concentrationin the grain rather than to increase yield In addition appli-cation of metal chelates may result in potential leaching riskbecause the more mobile the chelate or the less biodegradablethe carrier the greater the risk for leaching (Gonzalez et al2007)

Foliar application can provide a rapid correction of se-vere deficiencies commonly found during the early stages ofgrowth and are temporary solutions to the problem Foliarfertilization is more effective than soil application but too ex-pensive for resource-poor farmers Low penetration rates inthick leaves run-off from hydrophobic surfaces wash off byrainfall rapid drying of spray solution limited translocationwithin the plant and leaf damage are other problems related tofoliar applications (Marschner 1995) Most foliar-applied mi-cronutrients are not efficiently transported toward roots whichmay remain deficient Therefore application of micronutrientsto either soil or foliage may be successful in increasing grainyield only in well-defined circumstances

Another method to apply micronutrients to crop plants isthe treatment of seeds with fertilizers a technique called ldquoseedprimingrdquo The most effective way to prime micronutrients inseeds is to grow the parent crop on a soil with high levels ofphytoavailable Mn or Zn while spraying high levels of Znand Mn fertilizers on the plants during seed filling can alsoincrease seed levels considerably Mixing micronutrients withseeds must be limited to levels which do not harm the germi-nating seeds It has been reported that seed priming with Znsulphate resulted in a stronger increase in the grain yield ofwheat grown on Zn-deficient soil than foliar Zn applicationafter germination but it did not significantly increase grain Znconcentration in contrast to foliar and soil application (Rengeland Graham 1995 Yilmaz et al 1997 1998) lsquoOn-farmrsquo seedpriming with water is an effective way to increase yield inmaize and is important for resource-poor farmers as it is alow- or zero-cost technology and requires few external inputs


(Harris et al 2007) Recently Harris et al (2008) reported thatpriming seeds with ZnSO4 significantly increased the grain Znconcentration and concluded that using ZnSO4 to prime seedswas very cost-effective with net benefit-to-cost ratios of 75 forwheat and 780 for chickpea

Correction of micronutrients deficiency via fertilizationespecially in calcareous soils is not always successful andsustainable due to agronomic and economic factors such asreduced availability of micronutrient element due to topsoildrying subsoil constraints disease interactions and cost offertilizer in developing countries (Graham and Rengel 1993)

Some chemical fertilizers especially Zn and Fe fertilizermanufactured from industrial byproducts or mine wastes con-tain various contaminants such as cadmium and Pb (Afyuniet al 2007) The potential risks to environmental qualityposed by their repeated application to soil require careful eval-uation (Mortvedt 1985 1996) especially for rice production(Chaney et al 2004) Recently preserving the environment isbecoming a more important objective of agriculture to achievesustainable agricultural goals (Cakmak 2002 Tillman 1999)To avoid potential future environmental risks a more sustain-able strategy is required than just adding chemical micronutri-ents fertilizers to the soil Total amounts of some micronutri-ents such as Zn and Fe in agricultural soils are generally ordersof magnitude higher than the crop demand Thus micronutri-ents deficiency in crops is a problem of insufficient phytoavail-ability in almost all cases and not of absolute lacking sufficientquantity of micronutrients

42 Soil amendments

Soil amendments are frequently used by farmers to improvesome physical and chemical properties of soils (eg adjustingsoil pH) in order to enhance plant growth Limestone appli-cation is an effective and common practice to improve cropproductivity of acidic soils (Foy 1984 1992 Kochian 1995)Adding limestone may depress the uptake of Zn Cu Fe andCo and increase the uptake of Se and Mo by plants (Foy1984) The pH largely controls micronutrients solubility insoil and a small change in pH significantly affects solubilityand uptake of metals such as Zn Cu Mn and Fe Consider-ing increased pH of acidic soils by liming micronutrient defi-ciencies become more severe after liming (Verma and Minhas1987) A high soil-pH favors the oxidation of reduced formsof Se such as Seminus2 and SeOminus2

3 to the more soluble and plant-available SeOminus2

4 anionSeveral studies have examined the effects of combined fer-

tilization with lime and P Phosphorus causes changes in theextractability of Zn and in almost all soils further aggravatesZn deficiency in susceptible crops causing decreases in grainZn concentration (Hylander 1995) Thus Zn fertilizers mustoften be applied to ameliorate Zn deficiency associated withlimestone application (Tagwira 1993)

In contrast to limestone gypsum (CaSO4) and elementalS are used to decrease the pH of alkaline soils as well asto amend sodic and saline-sodic soils Application of acid-producing amendments on alkaline and calcareous soils could

decrease soil pH and consequently increase plant-available FeMn Zn Cu and Co Gypsum is used to exchange Ca for Naon the soil cation-exchange complex and to remove bicarbon-ate from the soil solution Removal of bicarbonate from thesoil solution can be highly beneficial for lowering the soil pHand increasing the availability of micronutrients (Singh et al1989) Singh et al (1989) reported that gypsum applicationin a sodic soil increased the mean concentration of Mn Znand Cu in mesquite (Prosopis julitlora) Application of gyp-sum caused significant reductions in pH and electrical con-ductivity (Singh et al 1989) The increase in soil availabilityof micronutrient as a result of gypsum application might be at-tributed to the decrease in soil pH and improved soil physicalproperties Further research is necessary to ascertain whetherbenefits of applying gypsum to alkali sodic soils are signifi-cant in terms of increasing micronutrient density in grain

43 Organic fertilizer sources

Application of different organic materials eg manuresplant residues and waste materials is a recommended strategyto improve soil fertility and enhance nutrient use efficiencyOrganic sources application is known as an effective man-agement strategy to sustain high crop productivity in manycropping systems Using organic sources may affect crop mi-cronutrient nutrition through affecting soil physical and chem-ical properties producing better root growth environment andadding some micronutrients to soil (Rengel et al 1999)

Soil organic matter has a variety of direct and indirect in-fluences on the phytoavailability of micronutrients in soil andtheir uptake by plants (Rengel et al 1999) Binding of somemetals such as Zn to organic matter reduces the concentra-tion of free cation in solution but if the metal-organic com-plexes are dissolved then the increase in total dissolved ionmay actually also increase effective metal phytoavailability atthe root-rhizosphere interface depending on the mobility andthe dissociation kinetics of the metal-DOC complexes Chela-tion of Zn and Fe by organic matter holds these nutrients informs more accessible by roots within the rhizosphere and re-tards formation of insoluble solid forms such as oxides andcarbonates in soil (Schulin et al 2009)

Adding organic resources such as crop residues green ma-nure livestock manure municipal biosolids or their compostsor co-composts to soil has a number of beneficial effects on mi-cronutrient nutrition including additional supply of some nu-trients with the added organic matter increase in ion exchangecapacity and thus of the fractions of easily available nutrientsimproved soil structure increase in water storage capacity im-proved drainage and aeration increased accessibility of soilfor plant roots decreased salinity stimulation of microbial ex-udation of organic ligands and of other microbial activities andas a result accelerated release of nutrients from secondary soilmatter enhanced nutrient supply through mycorrhizae andprotection against root pathogens All these effects promoteplant growth the development of the root system and thus alsoits capacity to acquire micronutrients (Schulin et al 2009)


The formation of metal complexes with organic ligandsin the soil solution is generally found to increase the mobil-ity of soil micronutrients On the other hand chelation cansubstantially reduce cellular metal uptake Because microele-ments bound to the soil surfaces can only reach roots by dif-fusion the mobilization effect of chelation generally seems tocause greater increase in plant uptake In previous studies evenstrong chelates (Zn-EDDS Zn-EDTA) still resulted in a netincrease of Zn uptake (Novack et al 2008) This can be ex-plained by increased rate of movement of the microelementfrom soil surfaces to root uptake surfaces by movement of dis-solved chelated elements (eg Wallace and Meuller 1973) Ithas also to be considered that leaf-applied chelates might notbe helpful for transport of micronutrients into grain (Cakmak2008 Novack et al 2008)

Effects of different organic amendments on correcting mi-cronutrients deficiencies have been widely investigated how-ever very few controlled experiments have been done to de-termine which types of organic matter practices significantlyenhance or depress the levels of micronutrients in edible por-tions of major food crops Therefore more research is neededto understand the impact of various types of organic amend-ments on crop nutritional quality

44 Plant residue

In many countries especially arid and semi-arid regionsvery little or no crop residue is left in the field much is usedfor feeding animals or for fuel (Timsina and Connor 2001) Itis estimated that more than 1000 million tons of cereal residuesare being annually produced in the developing countries (FAO1999) Rice wheat corn soybean barley rapeseed and potatoare the major residue-producing crops that globally produced2956 million tons of residues in 1998 (FAO 1999)

Crop residues are considered as important sources of sev-eral micronutrients Rice and wheat remove 96 777 745 4255 and 4 g haminus1 of Zn Fe Mn Cu B and Mo per ton re-spectively By estimating the total crop residue production of105 million tons in India and based on micronutrient con-tents of the residues the micronutrient potential associatedwith crop residues would be about 35400 tons (Prasad 1999)About 50 to 80 of Zn Cu and Mn taken up by rice and wheatcrops can be recycled through residue incorporation (Prasadand Sinha 1995b) Therefore recycling of crop residues canhelp improve soil availability of micronutrients

Crop residues addition to flooded soils stimulates micro-bial metabolism and thus increases soil solution Fe and Mnconcentrations due to greater redox potential change (Katyal1977 Yodkeaw and De Datta 1989 Atta et al 1996) In cal-careous soils organic acids produced during crop residue de-composition may increase plant Zn uptake by dissolving Znfrom the solid-phase pool to soil solution (Prasad and Sinha1995a) Chelating agents released from decomposing cropresidues increase the concentration of total diffusible Zn andits diffusion coefficient (Singh et al 2005) Rice straw appli-cation has been found to increase the Zn content of rice plants

possibly through its amelioration of soil pH and exchange-able sodium percentage (Singh et al 2005) In contrast cropresidue application has been reported to decrease the labile Znpools in an alkaline soil (Kang 1988) Other researchers (Rajand Gupta 1986) have also reported that application of rice orwheat straw decreased the phytoavailable Zn concentration inboth flooded and upland soils

Crop residues may also negatively affect crop productionin the short term because of N immobilization and phyto-toxic compounds release in allelopathic interactions Plantsmay release chemical compounds which can either stimulateor inhibit the growth and development of another plant Thesecompounds are dispersed into the environment from root ex-udates leaf leachates or from dead and decaying plant parts(Rose et al 1984 Huber and Abney 1986) Nutrient uptakemay be reduced by allelochemicals (Bhowmik and Doll 1984Rice 1984 Barnes and Putnam 1986) It has been suggestedthat sweet potato residues have an allelopathic effect (Walkerand Jenkins 1986) Sweet potato and cowpea indicator plantsgrown in sweet potato crop residues displayed symptoms re-sembling complex nutrient deficiencies Abiotic factors suchas reduced soil pH increased soil osmotic potential reducedoxygen concentrations and low nutrient content of the residuemay also have caused growth inhibition and as a result re-duced plant nutrient uptake Walker et al (1989) reported thatplant uptake of P K Ca Mg S Zn B and Cu were sub-stantially lower in plants grown in soil with amendment bysweet potato root or vine residues than in plants grown in with-out sweet potato residue treatments Successful integration ofcrop residue management strategies into cropping systems re-quires understanding of how crop residues influence cyclingof nutrients from soil and fertilizers as well as their effectson soil chemical physical and biological properties and cropproduction

45 Animal manure

Livestock manure is a good source of plant nutrients and itsapplication in agricultural lands is a traditional nutrient man-agement in many countries worldwide The use of manurescan also change plant-available micronutrients by adding mi-cronutrients or by changing both the physical and biologicalcharacteristics of the soil (Stevenson 1991 1994) Eghballet al (2004) found that applications of manure and compostnot only improved soil physical properties but also providednutrients for growing corn The residual effects of manure onsoil properties remained several years after application Gaoet al (2000) found that manure was a better source of availableFe Mn and Zn compared to synthetic fertilizers but manureaccelerated the depletion of available Cu Manure not onlysupplies large amounts of Zn to the soil but also promotes bi-ological and chemical reactions that result in the dissolution ofnon-available Zn (Wei et al 2006) Wei et al (2006) reportedthat manure application had no significant effect on availableCu This might be attributed to the low amount of Cu in themanure used in this experiment Copper could be bound to or-ganic matter and thus be relatively unavailable to plants


Zinc and Cu may be added to poultry feeds as a preven-tive for scour and to suppress bacterial action in the gutAccordingly Zn and Cu concentrations of some compoundpoultry and swine feeds are several times higher than thatrequired by the animals for healthy development In areaswhere animal manures have been applied for many years andwhere applications are expected to continue high amounts ofheavy metals (particularly Zn and Cu) may accumulate in soil(Nicholson et al 1999) The micronutrient contents of farmmanures largely depend on their concentrations in the feedsconsumed and the efficiency of feed conversion by the ani-mals Fleming and Mordenti (1991) reported mean Zn con-centrations of cattle manures in Belgium of 580 mg kgminus1 DMIn Switzerland cattle manures generally contain lt200 mgZnkg DM (Menzi and Kessler 1998) Webber and Webber(1983) reported cattle manure Zn concentrations in the rangeof 30plusmn225 mg kgminus1 DM The mean Cu concentration in cat-tle manures was reported to be 16plusmn62 mg kgminus1 DM (Flemingand Mordenti 1991 Menzi and Kessler 1998) Sims andWolf (1994) reported Zn concentrations ranging from non-detectable to 660 mg kgminus1 DM in poultry manure and fromnon-detectable to 669 mg kgminus1 DM in poultry litter The max-imum content of Cu in poultry manures and litters were232 mg kgminus1 DM and 1003 mg kgminus1 DM respectively

Farm manures are a valuable source of major plant nutri-ents (N P K) and organic matter However care must be takento ensure that manure applications containing elevated levelsof heavy metals do not cause long-term soil contaminationThen the typical amounts of heavy metals in solid manureshave to be calculated before manure addition to soil Exces-sive cumulative application of manure can cause accumula-tion of phosphate in surface soils which increases the poten-tial for runoff of phosphate which can cause adverse effectsin streams Thus applications of manures are being limited tothe phosphate fertilizer requirement of crops rather than theN fertilizer requirement which applied much higher annualmanure amounts Several groups have developed models forapplication of major and micronutrients with all soil amend-ments for large areas considering livestock manure biosolidsphosphate and other fertilizers These studies illustrate accu-mulation of Zn Cu and Cd in soils when microelement richmanures are applied (Keller and Schulin 2003) These issuesare more important in areas with intensive animal productionbecause feedstuffs are imported from distant farms but thelivestock residues are applied to the local farm of the livestockproducer In developing countries where livestock productionis achieved with local inputs accumulation of Zn and otherelements in the soil is less of a concern

46 Organic amendments

Biosolids and composts are usually effective Zn and Cufertilizers Possibility of correcting micronutrient deficiencyin different plant species by application of biosolids mu-nicipal waste leachates and compost has been reported(Khoshgoftarmanesh and Kalbasi 2002) When soils need Znor Cu fertilization high quality biosolids and composts could

be used to supply the required Zn and Cu Such amendmentsare not normally able to replace B fertilizers but mixing withcoal combustion byproducts can supply adequate B for themixture to serve as B fertilizer (Chaney and Ryan 1993)

Because production of composts will save costs in bothurban and agricultural areas they can be used as inexpen-sive fertilizers Although such benefits are possible from useof composts these products must be safe for sustainable usein horticulture and agriculture for their use to be permitted bygovernments and must reliably supply nutrient and organicmatter benefits to become competitive products in the mar-ket place The potential presence of pathogens heavy met-als xenobiotic compounds and possible element imbalancein composts has caused concern to compost application Somebelieve that because the concentration of Zn or Cu in compostsis higher than found in background soils these materials mustnot be utilized on soils However researchers have used highquality organic mattercompost products for decades withoutadverse effects (Andersson 1983 Chaney and Ryan 1993Woodbury 1992) Composts prepared in developing countriesoften do not receive the contaminants which have caused con-cerns in developed countries Over time boron use in glues andother products has declined such that municipal solid wasteswhich used to commonly contain phytotoxic levels of boronare only a useful B fertilizer today As with biosolids com-posts from off-farm sources should be analyzed for contami-nants and nutrients so that these resources can be wisely man-aged on cropland

47 Crop rotation

Cropping systems practices influence micronutrient avail-ability A preceding crop may influence soil conditionsthat govern soil fertility in general and micronutrientsphytoavailability to the successive crop in particular Thesecan result from residual effects of root litter and exudates onsoil physical and chemical parameters as well as on soil mi-croorganisms generation of root channels and other plant-soilinteractions Legumes may positively affect soil quality by im-proving soil physical properties Improved physical propertiesof the soil provide a better root growth condition and as aresult enhance uptake of immobile micronutrients by rootsCrop rotation systems may also affect some soil chemicalproperties (ie pH) Alvey et al (2001) found that a legumerotation system was more effective in increasing the pH ofthe rhizosphere as compared to continuous sorghum croppingsystem The increase in pH was considered as an importantmechanism of the plant to cope with acidity-induced nutrientdeficiency However in the long term N fixation increasessoil acidity and must be counteracted by alkaline amend-ments Khoshgoftarmanesh and Chaney (2007) reported thatwheat plants grown after sunflower accumulated more Znin their grains as compared to those planted after cottonLiu et al (2002) found that a rice-upland crop rotation pro-moted the reduction of Mn in the surface soil and acceler-ated the oxidation and accumulation of Mn in the subsoilBronick and Lal (2005) reported that crop rotation enhanced


soil organic carbon accumulation Diekow et al (2005) re-ported that higher residue input associated with legume-basedcropping systems significantly increased soil organic carbonMitchell and Entry (1998) found that long-term planting oflegumes as a winter cover crop resulted in higher soil organiccarbon levels compared with treatments that did not include awinter cover crop

Wei et al (2006) found that available Zn and Cu variedwith different cropping systems The amount of phytoavail-able Cu in soil decreased in the order continuous clover gtcropndashlegume rotation gt continuous wheat Differences amongcropping systems could probably be attributed to differences inthe Cu uptake capacity of each crop Long-term cultivation ofleguminous crops may lead to a large increase in available Mndue to changes in the soil microenvironment by leguminouscrops that result in the release of plant available Mn (WilliamsCH and David 1976)

Gunes et al (2007) found that intercropping of wheat andchickpea inoculated with a Rhizobium on a calcareous clayloam soil (pH 79 in water extract 096 organic mattercontent) with a very low DTPA-extractable Zn concentration(011 mg kgminus1) increased the Zn concentrations of shoots andseeds in both species Zuo and Zhang (2008) reported thatFe Zn and Cu concentrations of intercropped grown peanutincreased significantly compared to those in monocroppingboth in the greenhouse and field Systemic mechanisms maybe involved in adaptation to nutrient stresses at the wholeplant level A reasonable intercropping system of nutrient effi-cient species should be considered to prevent or mitigate ironand zinc deficiency of plants in agricultural practice (Zuo andZhang 2009)

The effect of crop rotation on the available and total mi-cronutrient contents in soils is somewhat different (Wei et al2006) Total nutrient content is affected mainly by crop uptakeand therefore the magnitude of the decrease depends on croptype and uptake intensity

5 DEVELOPING MICRONUTRIENT-EFFICIENTGENOTYPES A NEW STRATEGY

51 Definition of nutrient efficiency

According to the Soil Science Society of America (1997)nutrient efficiency is the ability of a plant to absorb translo-cate or utilize more of a specific nutrient than other plantsunder conditions of relatively low nutrient availability in thesoil or growth media This is the agronomic focus rather thanthe food quality focus which will be discussed below Graham(1984) defined plant nutrient efficiency as the ability of a geno-type to produce a high yield under conditions in which a soilnutrient is growth-limiting Blair (1993) defined plant nutrientefficiency as the ability of a plant to acquire nutrient from agrowth medium andor to utilize it in the production of shootand root biomass or grain According to Isfan (1993) effi-cient genotypes are those with high ability to absorb nutri-ents from soil and fertilizer produce high grain yield per unitof absorbed nutrient and store relatively little nutrients in the

straw As defined by Clark (1990) an efficient genotype isone that produces more dry matter or has a greater increasein the harvested parts per unit time area or applied nutrienthas less deficiency symptoms or has greater incremental in-creases and higher concentrations of mineral nutrients thanother genotypes grown under similar conditions Gourley et al(1994) proposed that the nutrient requirement of an efficientgermplasm is less than an inefficient germplasm Fageria et al(2008) defined a nutrient efficient genotype as a genotype thatproduces higher economic yield with a determined quantity ofapplied or absorbed nutrient than other genotypes under simi-lar growing conditions

Nutrient efficiency emphasizing utilization is generally de-fined as total plant biomass produced per unit nutrient ab-sorbed which is equivalent to the reciprocal of the nutrientconcentration of the entire plant (Gourley et al 1994) Thisoften is called the rsquonutrient efficiency ratiorsquo and has been usedextensively to describe the internal nutrient requirement par-ticularly of P in many agronomic plant species (Baligar et al1990 Glass 1989 Godwin and Blair 1991) Using this def-inition P-efficient alfalfa genotypes with higher shoot P con-centration are selected to overcome P nutrition limitations incattle (Miller et al 1987)

The reciprocal of nutrient concentration does not considerthe crop yield Siddiqi and Glass (1981) suggested ldquoutilizationefficiencyrdquo defined as the product of yield times the recipro-cal of nutrient concentration The nutrient uptake per unit rootlength surface area or weight has also been defined as ldquouptakeefficiencyrdquo (Buso and Bliss 1988) In most studies micronu-trient efficiency has been calculated as the ratio of yield (shootdry matter or grain yield) produced under micronutrient defi-ciency (-M) to yield produced with micronutrient fertilization(+M) as follows (Graham 1984)

Micronutrient efficiency = (yield ndash Myield+M) times 100

In this paper the last definition is considered as themain definition of micronutrient-efficiency for separatingmicronutrient-efficient and inefficient genotypes Such an in-dex is used to select improved micronutrient-efficient geno-types in a breeding program or to provide information onqualities of commercial cultivars for growers

52 Micronutrient-efficient genotypes and cropproductivity

Application of fertilizers is not a totally successful strategyin alleviating micronutrient deficiency because of agronomiceconomic and environmental (Mortvedt 1994 Graham andRengel 1993 Hacisalihoglu 2002)

A more efficient and sustainable solution to micronutri-ent deficiency limitations to crop production is the develop-ment and use of micronutrient-efficient plant genotypes thatcan more effectively grow on soil with low phytoavailable mi-cronutrient contents which would reduce fertilizer inputs andprotect the environment as well Selection of plant genotypesthat can tolerate low nutrient supply may increase produc-tivity on low fertility soils and reduce fertilizer requirements(Gourley et al 1994)


One of the most important adaptive responses for cropplants involves their ability to deal with soil-mediated abi-otic stresses involving deficient levels of micronutrients in thesoil Plant species vary significantly in tolerance to micronu-trients deficiency stress some are able to cope with low mi-cronutrients availability and thus grow well even when otherspecies or cultivars suffer reduced yield due to micronutrientdeficiency (Graham and Rengel 1993)

Exploiting genetic diversity of plants for enhanced pro-ductivity in poor fertility soils is a desirable and importantobjective in order to meet food demands for an increasingworld population Variation among plant germplasm in theability to acquire nutrients from the soil has been investi-gated for decades (Godwin and Blair 1991) There are severalkey mechanisms that could be involved in nutrient efficiency(Baligar et al 2001 Fageria and Barbosa Filho 2001 Fageriaand Baligar 2003 Khoshgoftarmanesh et al 2004a 2006a)including root processes that increase the bioavailability of soilnutrient for root uptake enhanced root uptake and transloca-tion of nutrients from the root to the shoot altered subcellularcompartmentation of nutrient in shoot cells and more efficientbiochemical utilization of nutrients in cells of the shoot Manypossible processes for control of nutrient efficiency have beeninvestigated In recent years more attention has been paid tomicronutrient efficiency

Micronutrient efficiency is genetically controlled and thephysiological and molecular mechanisms of micronutrient ef-ficiency of plants are just beginning to be understood Largeranges of genotypic variation in response to micronutrients de-ficiency stress have been reported in different plant speciesparticularly in cereals (Graham et al 1992 Cakmak et al1997a 1998) Such large variation is promising for developingplant genotypes that are more efficient in root uptake translo-cation from root to shoots andor internal utilization of mi-cronutrients Micronutrient-efficient genotypes may provide anumber of other benefits such as reductions in the use of fertil-izers improvements in seedling vigor resistance to pathogensand enhancement of grain nutritional quality (Graham andRengel 1993 Bouis 1996 Graham and Welch 1996)

Selecting and breeding staple food crops which are moreefficient in the uptake of trace minerals from the soil and loadmore trace minerals into their seeds combines benefits both foragricultural productivity and human nutrition This approachmay have important applications for increasing farm produc-tivity in developing countries in an environmental-friendlyway (Cary et al 1994 Kannenberg and Falk 1995) Growingnutrient-efficient genotypes on soils with low nutrient avail-ability would reduce land degradation by reducing the useof machinery (Thongbai et al 1993) and by minimizing ap-plication of chemicals such as fertilizers on agricultural land(Rengel 2001)

Beneficial effects of micronutrient-efficient crop geno-types for agricultural productivity result in extremely highcostbenefit ratios for investing in this type of micronutri-ent intervention Furthermore the adoption and spread ofmicronutrient enriched seeds by farmers can be driven byprofit incentives because micronutrient enriched seeds in-crease crop productivity when planted in micronutrient-poor

Table I Response of five wheat genotypes with different zinc effi-ciency to salinity and zinc application treatments (Khoshgoftamaneshet al 2006a)

NaCl rate (mM)Shoot dry matter yield (g potminus1)

Dur-3 Kavir Falat Rushan CrossWithout Zn

0 691 826 941 929 99660 593 754 631 855 853120 502 553 613 695 804180 306 491 435 681 585

With Zn0 805 1165 986 933 100860 771 921 775 872 896120 763 843 682 796 881180 351 544 431 718 657

soils (Graham et al 2001) The benefits can be disseminatedwidely and they are sustainable once developed unlike cur-rent micronutrient interventions that rely on supplementationor food fortification (Graham et al 2001 2000 Welch et al1997)

Developing plants with a high ability to extract transitionmetal nutrients from soils may be more useful for Fe and MnSoils which cause deficiency contain substantial levels of totalFe or Mn but the minerals are not phytoavailable to traditionalgenotypes Induced iron deficiency chlorosis is widespreadand is a major concern for plants growing on calcareous or al-kaline soils due to their high pH and low availability of iron(Welch et al 1991 Marschner 1995) In calcareous soilsFe and Mn rapidly convert to immobile forms and generallyseveral foliar applications are required to prevent deficienciesthroughout the growing season Selecting or breeding iron ef-ficient genotypes of corn soybean sorghum and rice is con-sidered the best way for correcting Fe deficiency stress on cal-careous soils (Graham 1984 Fageria and Baligar 2003) Soilapplication of Cu Zn and Mo is more efficient than Mn andFe fertilization on most soils but all transition metal nutri-ents are not readily translocated within plants on deficient soil(Nable and Webb 1993 Graham and Webb 1991)

Several studies have been done to select and breed culti-vars with greater abilities to cope with adverse soil condi-tions Micronutrient-efficient genotypes were described thathave the ability to take up and utilize nutrients more effi-ciently under abiotic and biotic stresses (Pessarakli 1999Alam 1999 Baligar et al 2001) or that some micronutrient-efficient genotypes can tolerate abiotic and biotic stresses(Fageria et al 2008 Khoshgoftarmanesh 2004a 2006a bMarschner 1995) Plant crop yield under stress could be en-hanced by selection or breeding of plants that have highmicronutrient efficiency and ability to interact effectivelywith environmental extremes (Fageria et al 2008) For ex-ample Khoshgoftarmanesh et al (2004a b 2006a b) andKhoshgoftar and HajiMozaffari (2006) reported that zinc ap-plication in a severely calcareous saline soil increased the salttolerance of wheat genotypes Zinc-efficient genotypes are re-ported to be more tolerant to salinity than Zn-inefficient geno-types (Tab I) Bagci et al (2007) indicated that sensitivity


to Zn deficiency stress became more pronounced when wheatplants were drought-stressed The effect of irrigation on grainyield was maximized when Zn was adequately supplied Closerelationship between water use efficiency and Zn nutritionalstatus of plants has also been suggested (Bagci et al 2007)

Plant nutrition status may greatly affect predisposition ofplants to attack by or effect of pests and diseases (Fageriaet al 2008) Micronutrient deficiencies reduce the plant toler-ance to diseases and insects (Marschner 1995) The fungicidaleffect of manganese (Mn) copper (Cu) and zinc (Zn) are well-known as they have been common constituents of fungicides(Streeter et al 2001) Copper B and Mn are involved in thesynthesis of lignin and phenolic compounds Silicon plays arole in producing physical barriers against pathogen penetra-tion (Barker and Pilbeam 2007 Graham and Webb 1991)

Streeter et al (2001) reported that Zn-sufficient plants aremore tolerant to the effects of root pruning by the fungus thanZn-deficient plants probably due to fungitoxicity of Zn and therole of Zn in the integrity or stability of the host plantrsquos mem-branes The increased root exudation by Zn-deficient plantsmay accelerate the root-rot disease (Thongbai et al 1993) Arelationship between Zn nutrition and severity of some root-rot diseases has been demonstrated in wheat (Thongbai et al1993) and medic plants (Streeter et al 2001) Streeter et al(2001) suggested that Zn application does not directly inhibitinfection by Rhizoctonia solani nor reduce its pathogenicitybut it does strongly increase root growth Zinc nutrition is ben-eficial in reducing the occurrence of phyllody virus in whiteclover (Carr and Stoddart 1963) take-all in wheat (Brennan1992) and charcoal rot development in maize (Pareek andPareek 1999)

Silicon applications reduce the severity of fungal diseasessuch as blast and sheath blight of rice powdery mildew ofbarley and wheat and vermin damage of rice by the planthopper in the field (Barker and Pilbeam 2007) Plant geno-types with higher ability to absorb andor utilize micronutri-ents seem to be more resistant to disease than micronutrient-inefficient genotypes The relationship between insect attacksand micronutrient-efficiency of plant genotypes needs furtherevaluation (Fageria et al 2008)

Considerable progress has been made in breeding for ZnFe and Mn efficient dicots and monocots and in identifyingthe genes involved (Marschner 1995 Rengel 2001) By com-paring efficient and inefficient cultivars some information onthe genetic control of micronutrients efficiency has been ob-tained (Graham 1984 Rengel 2001) This information willaccelerate development of more nutrient efficient crop plantsby traditional and modern breeding techniques and provideimportant information for genetic engineering

53 Micronutrient-efficient genotypes crop qualityand human health

531 Total concentration of micronutrients in plantbased foods

Different traditional public health interventions have beenused to improve micronutrient nutritional status of the target

population ie supplementation food diversification indus-trial fortification and biofortification Supplementation and in-dustrial fortification have been effective in reducing morbidityand mortality resulting from micronutrient deficiencies world-wide but infrastructure purchasing power or access to mar-kets and healthcare systems is required in these approachesoften not available to poor people particularly in rural areas(Mayer et al 2008)

Supplementation with pharmaceutical micronutrient prepa-rations eg vitamin A and Zn capsules can be a rapid and effec-tive way to alleviate micronutrient-deficiency on an individualbasis However this strategy has generally failed on a popula-tion level in developing countries due to lack of adequate in-frastructure and education (Graham et al 2000 Stein 2006)For example vitamin A supplementation programs coveredup to 58 of target population over the last decades in 103priority countries with a goal of preventing blindness causedby vitamin-A deficiency (UNICEF 2007) Iron supplementa-tion had little effect on the anemia problem in India becauseof mismanagement underfunding logistic problems and poorcompliance (Vijayaraghavan 2002)

Food fortification is a strategy that can be applied ratherrapidly at the national level without changes in the dietaryhabits of people As a public health measure wheat flour iscommonly fortified with iron margarine with vitamin A andD and salt with iodine However Zn interventions with forti-fied foods or supplements are still largely experimental Somecountries also fortify wheat flour with zinc Fortification ofmaize and wheat flours with Fe has been implemented inMexico Indonesia and South Africa but this approach stillneeds further evaluation (Gibson 2006) Ahmed et al (2008)concluded that fortification of whole wheat flour is feasibleto alleviate Fe and Zn deficiency in vulnerable groups A dis-advantage of food fortification is that like supplementationits successful implementation into society requires safe deliv-ery systems stable policies appropriate social infrastructuresand continued financial support (White and Broadley 2005Gibson 2006)

In the case that foods differ widely in available contents ofmicronutrients dietary modification or diversification wouldseem a straightforward and sustainable way to combat mi-cronutrients deficiency But changes in dietary habits requireindividual and societal acceptance as well as the availabilityof alternative foods at affordable prices Poverty is anotherchallenge that makes this strategy less applicable for poorcountries

Due to problems such as inadequate logistics insufficientcompliance political instability and instability of fundingmany of these interventions have failed In particular manyof these programs never reached the majority of low-incomewomen infants and children in developing countries (Welchand Graham 1999)

Using bioavailable micronutrient-dense staple crop cul-tivars is another approach that could be used to improvethe micronutrient nutritional status of human (Bouis 1996Combs et al 1996 Welch and Graham 1999 Frossard et al2000 Welch 2002) Cultivation of micronutrient-efficientcrop genotypes holds great promise for making a significant


Table II Range and mean concentrations of Fe and Zn in the shootand grain of different wheat genotypes in the presence and absenceof added Zn fertilizer (Khoshgoftarmanesh et al 2007)

Concentration (microg gminus1)Zn Fe

Minus Zn Plus Zn Minus Zn Plus ZnShoot

Range 55ndash213 59ndash260 150ndash980 143ndash1010Mean 92 135 571 596

GrainRange 46ndash414 76ndash362 85ndash758 97ndash841Mean 98 118 452 612

low-cost and sustainable contribution to reducing micronutri-ent particularly mineral deficiencies in humans

This strategy for which the term ldquobiofortificationrdquo has beencoined has the potential to be sustainable as well as economi-cal Biofortification is based on the principle that health comesfrom the farm not the pharmacy (Mayer et al 2008) Likefortification in general it does not require people to changetheir dietary habits This approach is attractive for the farmerbecause of increased yields and reduced seedling losses anddoes not require special infrastructure In addition the outputof this program can be distributed to the remote rural areaswhere poor populations are living at low cost (Graham et al2000 Yang et al 2007)

Biofortification can be achieved (i) by breeding or geneticengineering crop plants with improved ability to accumulatetarget micronutrients in potentially bioavailable form in edibleplant parts (Graham et al 2000 Welch and Graham 2004White and Broadley 2005) (ii) by increasing (bioavailable)micronutrient density in food plants by agricultural methodsof crop cultivation for example by fertilizer application orby amendments that increase the elementrsquos bioavailability inthe soil for plant uptake (Frossard et al 2000 Graham et al2001 Welch 2002)

Most modern cultivars of wheat and rice have a lower con-centration of micronutrients in grain than traditional culti-vars because breeders generally focused on increasing yieldwith no attention to the micronutrient concentrations in grainBreeding micronutrient-dense cultivars of staple foods is apowerful tool to combat micronutrient malnutrition Recentfindings show that it is possible to breed for enhanced levelsof iron zinc and provitamin A carotenoids in edible tissues ofrice wheat maize beans and cassava (Graham et al 2001)Recently the international genomes of rice (Oryza sativa L)wheat (Triticum aestivum L and T durum Desf) maize (Zeamays L) beans (Phaseolus vulgaris L) cassava (Manihot es-culenta Crantz) and sweet potato (Ipomoea batatas L) havebeen surveyed for high micronutrient density traits (Grahamet al 2001)

Large variation in the grain micronutrients concentrationeg Fe and Zn in different wheat genotypes has been reported(Cakmak 2002 Graham et al 1999 Kalayci et al 1999Khoshgoftarmanesh et al 2004a 2006a b) As shown in Ta-ble II different wheat genotypes vary greatly in grain Zn and

Fe concentrations ranging from 85 to 84 microg gminus1 for Fe and46 to 414 microg gminus1 for Zn (Khoshgoftarmanesh et al 2007)The large genetic variation found in Fe Zn Mn and Se con-centrations among geotypes in the major germplasm banks issufficient to justify the possibility of developing micronutrient-efficient genotypes Thus it seems feasible for crop breedersto select for high micronutrients density traits in breeding pro-grams

Modern recombinant DNA technology can also be usedto enhance the nutritional quality of food crops such as in-creasing the amount and bioavailability of micronutrients inplants (DellaPenna 1999 Frossard et al 2000 Goto et al1999 2000 Lucca et al 2001) For example recombinantDNA technology was used to improve the provitamin A con-tent of rice-grain endosperm in lsquoGolden ricersquo (Ye et al 2000)Goto et al (1999) transformed rice plants using a phytoferritin(a major protein storage form of Fe in plants) gene from soy-bean and a rice endosperm promoter gene to enrich Fe in therice-grain endosperm Lucca et al (2001) also enriched the Feconcentration in rice-grain endosperm using the phytoferritingene from pea plants

The strategy of breeding for mineral and vitamin enhance-ment of staple foods has several complementary advantagesMicronutrient-dense crop genotypes deploy micronutrients toconsumers through the traditional ways with no necessity forchanges in consumersrsquo behavior (Mayer et al 2008) The con-sistent daily consumption of large amounts of food staples byall family members is another benefit of this approach Never-theless any intervention to improve micronutrient status musttarget women children and adolescents because of their ele-vated needs for minerals and vitamins (Nicklas 1995)

Biofortification programs for β-carotene iron and zinchave been estimated to be cost-effective (Neidecker-Gonzaleset al 2007 Stein et al 2007) Investments in plant-breedingresearch are much less than those in supplementation and forti-fication programs because the increased value persists after de-velopment In addition supplementation and fortification pro-grams must be sustained and thus much more investment isneeded in these programs If investments are not sustainedbenefits disappear Development of iron- and zinc-dense culti-vars of rice or wheat might cost as much as $10 million eachover 10 years including the costs of nutrition efficacy tests thecosts of dissemination in selected regions and the costs of anutrition and economic impact evaluation Moreover benefitsare sustainable at low maintenance costs

However before beginning extensive breeding programsit is essential to confirm that the micronutrient is sufficientlywell absorbed and utilized by human consumers In fact fur-ther research is needed to determine if the edible portions ofmicronutrient dense crop grains still retain enriched levels ofmicronutrients after milling and processing and if enrichedlevels of micronutrients in grain are bioavailable to target hu-man populations

Agronomic biofortification is required for optimizing andensuring the success of genetic biofortification of cereal grainswith Zn and Se (Broadley et al 2006 Cakmak 2008) Incase of greater bioavailability of the grain Zn derived fromfoliar applications than from soil agronomic biofortification


would be a very attractive and useful strategy in solving Zndeficiency-related health problems globally and effectively(Cakmak 2008) In fact agronomic biofortification strategyappears to be essential in keeping sufficient amount of avail-able Zn in soil solution and maintaining adequate Zn transportto the seeds during reproductive growth stage (Cakmak 2008)

532 Bioavailability of micronutrients in food

Although increasing the concentration of micronutrients inplant foods is necessary the absorption and utilization (iebioavailability) of micronutrients in meals containing plantfoods may be also improved (Graham and Welch 1996) Plantfoods contain various substances that interact with micronutri-ents Some called antinutrients reduce whereas others calledpromoters enhance micronutrient bioavailability to humans(Graham et al 2001) These substances can be also manip-ulated by agricultural practices (Graham et al 2001) and bygenetic manipulation (Lucca et al 2001)

The nutritional value of a diet can not be determined solelyfrom the total contents of individual nutrients Concentrationsof antinutrients and promoters as well as interactions betweennutrients affect bioavailability which is the amount of nutri-ent absorbed from the diet (Graham et al 2000) In fact thefraction of micronutrient content in food that is available forabsorption by the human gastro-intestinal tract depends onthe presence of other food ingredients A number of nutri-ent promoters and antinutrients has been found Research onthe potential role of a variety of substances to act as promot-ers or antinutrients of some micronutrients such as Fe and Znbioavailability to humans has been reviewed by House (1999)There is evidence for a promoter function of certain chelatinglow-molecular-weight organic acids as well as amino acidsDrakakaki et al (2005) concluded that the expression of re-combinant ferritin and phytase could help to increase ironavailability and enhance the absorption of iron particularly incereal-based diets that lack other nutritional components Phy-tate tannins and other polyphenols and some heavy metals actas antinutrients (Frossard et al 2000 Graham et al 2001)

Plant crop genotypes differ not only in grain micronutri-ent concentrations but also in the amounts of antinutrientsand promoters in their seeds For example phytate concen-tration strongly depends on the plant genotype (Cakmak andMarschner 1986 Khoshgoftarmanesh et al 2007 Marschner1995 Torun et al 2001) Erdal et al (2002) found differ-ences in phytate content of grain in 20 different wheat cul-tivars grown on a Zn-deficient calcareous soil (010 mg kgminus1

DTPA-extractable Zn) in central Anatolia Zinc fertilization(23 kg haminus1 Zn applied as ZnSO4) increased seed Zn concen-tration in all cultivars and reduced seed phytate in the majorityof the cultivars The average increase in seed Zn was from 88to 167 mg kgminus1 while phytate decreased in average from 107to 100 mg gminus1 grain dry weight Raboy et al (1991) showedthe existence of an important variation in phytate-P amongfour wheat cultivars and their 60 F6 lines Barrier-Guillot et al(1996) reported that phytate-P in seeds of four wheat cul-tivars varied between 092 and 280 g kgminus1 DW The range

Table III The range and mean molar ratio of phytic acid to Zn ingrains of selected wheat genotypes in the absence and presence ofadded Zn (Khoshgoftarmanesh et al 2007)

Phytic acidZn molar ratioWhole grain Bran-less flour

Minus Zn Plus Zn Minus Zn Plus ZnRange 39ndash88 43ndash76 27ndash49 18ndash37Mean 48 31 29 26

and mean concentration of Zn and molar ratio of phytate-to-Zn in selected Iranian wheat genotypes are shown in Ta-ble III The genotypic variability in seed phytate concentra-tion of wheat genotypes indicates that this variation can beexploited for breeding genotypes with low phytate concentra-tions to improve Zn bioavailability in cereal-based foods al-though attention should be paid to the fact that low phytatecontent increases the possibility of cancers In addition phy-tate is required for seed germination

In most cases phytate-to-Zn molar ratios in foods are con-sidered a predictor of Zn bioavailability (Gargari et al 2007)This index has been used widely (Gibson et al 2003 Interna-tional Zinc Nutrition Consultative Group-IZiNCG 2004) andit is considered as a good index for zinc bioavailability by theWorld Health Organization (World Health Organization 1996)and International Zinc Nutrition Consultative Group (Interna-tional Zinc Nutrition Consultative Group-IZiNCG 2004)

54 Combining the benefits of high yield and betternutritional quality

An important question in development of micronutrient-efficient genotypes is the possibility of combining high yieldwith better micronutrient nutritional quality Previous studiesshowed that it is possible to combine micronutrient-rich traitswith high yield Both seedling vigor and nutritional qualitycan be improved through genetically modifying seeds with mi-cronutrient enrichment traits The highest micronutrient densi-ties which are approximately twice as high as those popularmodern cultivars and indicating the existing genetic potentialcan be successfully combined with high yield

The combining of benefits for human nutrition and agricul-tural productivity resulting from breeding staple food cropswhich are more efficient in the uptake of trace minerals fromthe soil and which load more trace minerals into their seedsresults in extremely high benefit-cost ratios for investments inagricultural research in this area This approach would be morevaluable and cost-effective by estimating the costs paid to healmicronutrient malnutrition in developing countries Some ad-verse effects of Zn and Fe deficiency cannot be remediatedby supplying adequate levels of Zn or Fe later in childhoodso prevention needs to be the focus of this seed improvementprogram

High trace mineral density in seeds produces more viableand vigorous seedlings in the next generation and efficiencyin the uptake of trace minerals improves disease resistanceagronomic characteristics which improve plant nutrition and


productivity in micronutrient deficient soils (Welch 1999Yilmaz et al 1998) Adoption and spread of nutritionally-improved varieties by farmers can rely on profit incentiveseither because of agronomic advantages on trace mineral defi-cient soils or incorporation of nutritional improvements in themost profitable varieties being released (Harris et al 2008)

It has been shown that wheat plants grown from seed withhigh Zn content can achieve higher grain yields than thosegrown from the low-Zn seed when Zn was not applied to thesoil (Yilmaz et al 1998) Therefore sowing seeds with higherZn contents can be considered a practical solution to allevi-ate plant Zn deficiency especially under rainfed conditions inspite of it being insufficient to completely overcome the prob-lem (Yilmaz et al 1998)

Mineral-packed seeds sell themselves to farmers becausethese trace minerals are essential in helping plants resist dis-ease More seedlings survive and initial growth is more rapidUltimately yields are higher particularly on trace mineral ldquode-ficientrdquo soils in arid regions Because roots extend more deeplyinto the soil and so can tap more subsoil moisture and nutri-ents the mineral-efficient varieties are more drought-resistantand so require less irrigation And because of their more effi-cient uptake of existing trace minerals these varieties requirelesser chemical inputs Thus the new seeds can be expectedto be environmentally beneficial as well It is conceivable thatseed priming by spraying seed fields with Fe and Zn fertilizersduring grain filling will provide enough additional yield ben-efit to justify additional seed price But this approach is insuf-ficient to improve the density of bioavailable micronutrientsin grain of crops grown with ldquoprimedrdquo seed Several differ-ent commercial practices may be beneficial to improve plantproduction despite low levels of soil micronutrients in manynations

55 Need to limit grain Cd and As while improvinglevels of Zn and Fe in crops

In contrast with the essential nutrients Zn and Fe cadmium(Cd) in soils can be accumulated to levels in rice and someother crops that are dangerous to consumers (Chaney et al2004) In areas of Asia where mine wastes contaminated ricepaddy soils rice accumulated Cd to levels over 04 mg kgminus1the CODEX ALIMENTARIUS maximum recognized levelsafe for lifetime consumption by humans In Japan Chinaand Thailand mine-contaminated paddy soils have caused ad-verse effects in exposed subsistence farm families (Nogawaet al 2004 Cai et al 1998 Swaddiwudhipong et al 2007)The nature of rice production and composition of polishedrice grain contribute to the potential for this effect (1) whenflooded rice is drained at flowering rapid drop in soil pH andtransformation of CdS to more soluble forms allows rapid up-take of Cd to rice grain during grain filling (2) polishing ofrice removes much of the Zn Fe and Ca in brown rice lev-els present in polished grain are insufficient to support humanhealth and (3) subsistence farming individuals may consumehome-grown rice for their lifetime allowing accumulation inthe kidney over time until injury occurs Although other crops

require consideration regarding transfer of soil Cd to humanswestern populations have not been found to suffer Cd diseasesperhaps because few consume home-grown staple foodstuffsgrown in contaminated soils for their lifetime Further mostsoil Cd is accompanied by 200-fold higher Zn so higher Zntends to limit Cd uptake into edible crop tissues (Chaney et al2004)

Two aspects of breeding Fe and Zn improved crops shouldconsider the potential for Cd accumulation First cultivarsvary in Cd accumulation due to genetic variation (Grant et al2008) normal breeding practices can produce higher Cd pro-genies by chance alone In general Cd has been found to en-ter plants on the root Zn-transporters (Hart et al 2002) Thusbreeding to increase Zn uptake may cause increased Cd accu-mulation as well Transport to grain of Cd and Zn are some-what independent so it is possible to achieve both higher Znand Cd uptake but only higher Zn movement to grain Breed-ing programs to improve grain Zn and Fe should check to as-sure that Cd is not being increased along with Zn In the sameway breeding to increase aluminum tolerance to allow produc-tion in strongly acidic soils will tend to increase uptake of Cdand other divalent cations (McLaughlin et al 1999) Breedersof acid tolerant crops need to assure that their new cultivarsare not also increased in Cd

Arsenic (As) is usually independent of grain Fe and Zn butrecent issues of As in irrigation water and rice require similareffort to consider the potential for As accumulation in grainBecause rice is grown in flooded soils and flooding producesarsenite which is more soluble more phytotoxic and more ac-cumulated by rice using high As waters to produce rice mayproduce grain with excessive As for lifetime consumption byhumans (Meharg 2004 Abedin et al 2002) For rice cultivarsto be grown on such As enriched soils breeding lower As ac-cumulating genotypes may be critical to the continued successof agriculture (Williams PN et al 2005)

56 Challenges in programs for selecting or breedingmicronutrient-efficient genotypes

Many different definitions for efficiency make the use ofthe term ambiguous These differences in defining nutrientefficiency makes it difficult to compare results of differentstudies particularly by considering that nutrient efficiency isinfluenced by other factors such as soil fertility status cli-mate crop rotations and management practices (Stewart et al2005) Gerloff and Gabelman (1983) proposed that genotypesdiffering in yield under nutrient stress should only be desig-nated efficient or inefficient if they are normal in appearanceand have similar yields when an optimal amount of the nutrientis available To reduce the confounding effects that other fac-tors have on nutrient efficiency Gourley et al (1994) proposedthat equivalent yields of genotypes be demonstrated wherenutrients are not limiting This advise has not been widelyfollowed by researchers plant species and cultivars with sig-nificantly different genetic potentials have been compared fortheir nutrient efficiency Figure 1 shows models of the responseof three plant varieties with different potential yield to different


0

1

2

3

4

5

6

7

8

9

0 20 50 80 110 140 170 200

Nutrient Concentration (kgha)

Crop yield (tha)

Genotype 3

Genotype 1

Genotype 2

Figure 1 Suggestive response of three different plant varieties to nu-trient concentration in media Genotype 3 produced the highest yieldunder non-stress conditions while its nutrient efficiency determinedas commonly used efficiency definition is less than other genotypesIn contrast the most nutrient-efficient Genotype 1 had the lowestyield when an optimal amount of the nutrient is available

soil nutrient levels These plant varieties have different yieldsin the presence of an optimal amount of the nutrient The plantvariety 3 produced the highest yield under non-stress condi-tions while its nutrient efficiency determined as commonlyused efficiency definition is less than other varieties In con-trast the most nutrient-efficient variety 1 had the lowest yieldwhen an optimal amount of the nutrient is available

One of the major difficulties with breeding for resistanceto nutrient deficiency is that the stress condition is frequentlyassessed based only on plant growth However growth is asa very complex character influenced by different inter-relatedprocesses Therefore growth is not a suitable parameter fordistinguishing causes and effects of micronutrient deficiencystress

Better screening techniques need to be developed by target-ing specific processes that promote micronutrient deficiencyrather than those that appear as a consequence of it It is ex-pected that in the near future molecular methods will domi-nate selection for nutrient efficiency Development of molecu-lar markers for regions of the genome segregating with the traitof a particular nutrient efficiency will be crucial in that respectHowever molecular markers may be population-dependentmaking them unsuitable for use in breeding programs Evenin screening based on molecular methods seed nutrient con-tent may need to be measured to assure the effectiveness of theprogram (Rengel 2001)

Identification of genotypes with differing nutrient efficien-cies by whatever definition generally includes investigationof potential morphological physiological and biochemicalmechanisms involved These mechanisms have been well re-viewed (Caradus 1990 Sauerbeck and Helal 1990) Howeverit is often difficult to separate cause from effect when evaluat-ing potential mechanisms of efficient nutrient uptake and uti-lization Mechanisms conferring micronutrient efficiency arediverse and complex Considering the close relationship be-tween the root and shoot activities differences in yield or nu-trient accumulation by plants may incorrectly be attributed to

differences in root morphology and function (Gourley et al1994)

Another challenge in breeding programs for assessment ofa large number of genotypes is that field testings are time-consuming and expensive Therefore simple fast and inex-pensive techniques rather than expensive field experiments arerequired (Graham 1984 Graham and Rengel 1993) At thisdate valid field screening is still needed before improved cul-tivars can be identified Although genes may be identified inlaboratory and greenhouse programs incorporating micronu-trient efficiency or density in grain with high yield and otheragronomic performance measures will require field screeningusing traditional breeding approaches

In most cases the crop yield has been considered as themain basis for separating micronutrient-efficient and ineffi-cient genotypes (Clark 1990 Stewart et al 2005 Fageriaet al 2008) There is a concern whether or not micronutrient-efficient genotypes with higher tolerance to micronutrient de-ficiency can accumulate more nutrients in their edible partsAlthough micronutrient-efficient genotypes possess higher up-take capacity they do not necessarily have higher micronu-trient concentrations in their leaves or grains (Graham et al1992) Micronutrient-efficient genotypes may even containlower micronutrient concentrations in their edible parts thanmicronutrient-inefficient genotypes (Cakmak et al 1997a b1998) Enhanced micronutrient uptake by efficient genotypesunder micronutrient deficiency stress improves dry matter pro-duction and often results in decreased tissue micronutrientconcentration (dilution effect) to levels similar to those presentin micronutrient-inefficient genotypes (Marschner 1995) Forexample Cakmak et al (1997a) reported that in Zn-deficientsoil the most Zn-efficient rye had lower Zn concentration inits tissues than a Zn-inefficient durum wheat Khoshgoftar-manesh et al (2006a) reported that Zn-efficient wheat geno-types had lower shoot and grain Zn concentrations as com-pared to Zn-inefficient genotypes although the total amount ofZn per shoot or grain was higher in Zn-efficient genotypes dueto more shoot dry matter yield

Two important questions need to be answered in programsfor selecting or breeding micronutrient-efficient cultivars Thefirst question is whether there is stability in response to nu-trient efficiency of plant genotypes in different environmentsor how do the interactions of genotype by environment (GtimesE)affect response of genotypes to nutrient deficiency and fertil-ization condition The second question regards relationshipsbetween crop productivity mineral concentrations and othernutritional quality factors (eg concentrations of promotersand antinutrients) and the way that both crop productivityand grain quality aspects can be combined in developing newmicronutrient-efficient genotypes

Another important aspect that has to be considered in de-veloping micronutrient-dense genotypes is that the bioavail-ability of micronutrients in enriched genotypes must be testedin humans to assure that they are of benefit to people preparingand eating them in traditional ways within normal householdenvironments Consumer acceptance must be tested (taste andcooking quality must be acceptable to household members) toassure maximum benefit to nutritional health


57 Stress tolerance indicators for selectingmicronutrient-efficient genotypes

Micronutrient deficiencies are abiotic stresses for plant pro-duction and most researchers have considered micronutrientefficiency synonymous with plant tolerance to micronutrientdeficiency stress A better understanding of the stress toleranceindicators is required for developing more reliable screeningprocedures to identify and select genotypes with high mi-cronutrient efficiency Breeders have used several yield stabil-ity analyses for identifying tolerant and sensitive genotypesto different environmental stresses (Fernandez et al 1989)A relatively severe deficiency of an essential nutrient can beconsidered as a stress for plants (Fernandez 1991) The fieldstress environment is characterized primarily by low inputssuboptimal levels of irrigation nutrients temperature andplant protection measures (Blum 1988) Selection of geno-types adapted to both stress and non-stress environments havebeen the main objective of several yield trials

Selection criteria are proposed to select genotypes basedon their performance in stress and non-stress environments(Rosielle and Hamblin 1981) who defined stress tolerance(TOL) as the difference in crop yield between the stress (Ys)and non-stress environment (Yp) and mean productivity (MP)as the average yield of Ys and Yp Fischer and Maurer (1978)proposed a stress susceptibility index (SSI) expressed by thefollowing relationship

SSI = [1 minus (YsYp)]SI (1)

where SI is the stress intensity and is estimated as [1 ndash(YsYp)] and where Ysminus and Ypminus are the mean yields overall genotypes evaluated under stress and non-stress conditionsRosielle and Hamblin (1981) evaluated the genotypic selectionbased on mean productivity (MP) and stress tolerance (TOL)and showed that selection of genotypes based on stress toler-ance was efficient in improving yield under stress conditionswhereas the selected genotypes performed poorly under non-stress environments

The heritability for yield is sometimes higher in the non-stress environment compared with the stress environment(Frey 1964) Generally evaluation in the non-stress environ-ment allowed a better expression of genotypic potential withhigher heritability estimate yield and yield components thangenotypes evaluated under the stress environments Genotypeeffect and its interaction with environment are usually higherunder favorable conditions compared to stress environmentsbecause the non-stress environmental conditions allow thegenotypes to express their maximum genetic potential

Genotypes can be categorized based on their performancein stress and non-stress environments into four groups (A)genotypes that are not affected by stress and produce the samein both stress and non-stress environments (B) genotypes thatproduce high yield only in non-stress environments (C) geno-types with high yield in stress condition and low yield innon-stress environment (D) and genotypes with low yield inboth stress and non-stress environments The optimum crite-rion should be separation of Group A from the other three

groups However the stress tolerance indicators mean produc-tivity stress tolerance and SSI failed to distinguish Group Agenotypes from the other three groups Fernandez (1991) pre-sented a new stress tolerance index STI which can be usedto identify genotypes that produce high yields under both non-stress and stress environments

The stress intensity (SI) is defined as

SI = 1 minus (YsminusYpminus) (2)

where Ypminus is the potential yield of a given genotype in a non-stress environment and Ysminus is the yield of a given genotype in astress environment The stress index can take values between0 and 1 The larger value of SI indicates more severe stressconditions Mean productivity (Eq (3)) favors higher yield po-tential and lower stress tolerance Rosielle and Hablin (1981)showed that under most yield trials the correlations betweenmean productivity and Yp as well as between mean productiv-ity and Ys would be positive Thus selections based on meanproductivity generally increase the average yield in both stressand non-stress environments However mean productivity cannot distinguish between Group A and Group B genotypes

MP = (Ys + Yp)2 (3)

The tolerance index (TOL) is calculated by equation (4) Alarger value of the tolerance index represents relatively moresensitivity to stress thus a smaller value of tolerance index isfavored Selection based on tolerance index separates geno-types with low yield potential under non-stress conditions andhigh yield under stress conditions The tolerance index fails todistinguish between Group C and Group A

TOL = Yp minus Ys (4)

The stress susceptibility index (SSI) is another indicator toscreen genotypes Smaller values of SSI indicate greater tol-erance to stress Under most yield trials tolerance index andstress susceptibility index are positively correlated Selectionbased on stress susceptibility index (SSI) favors genotypeswith low yield under non-stress and high yield under stressconditions Thus SSI also fails to distinguish Group A fromGroup C

Geometric mean productivity (GMP) is a better indicatorthan MP to separate Group A and Group C

GMP =radic

(Ys lowast Yp) (5)

Fernandez (1991) proposed stress tolerance index (STI) givenby the following equation

STI = (Yp)(Ys)(Ypminus)2 (6)

A high value of STI indicates great tolerance to stress and highpotential yield The stress intensity value is also incorporatedin the estimation of STI Thus STI is expected to distinguishGroup A from Group B and Group C

Three-dimensional plots of Ys (x-axis) Yp (y-axis) and STI(z-axis) based on grain yield of different bread wheat geno-types grown under severely Zn-deficient soil (stress condition)


Figure 2 The 3-D plot among salt tolerance index (STI) -Ze and +Ze condition for different winter wheat cultivars Group A genotypes thatare not affected by stress and produce the same in both stress and non-stress environments Group B genotypes that produce higher yield onlyin non-stress environments Group C genotypes with higher yield in stress condition and lower yield in non-stress environment and Group Dgenotypes with low yield in both stress and non-stress environments Mahdavi (1) Bezostaya (2) Navid (3) Alamoot (4) Alvand (5) Zarin(6) MV-17 (7) Gaspard (8) Gascogen (9) Sayson (10) Shahriar (11) Toos (12) Sabalan (13) Roshan Winter Back Cross (14) Shahi Cross(15) Shahpasand (16) Omid (17) Azar2 (18) Sardari (19) and C-81-10 (20) (Khoshgoftarmanesh not published)

and Zn fertilized soils (non-stress condition) is shown in Fig-ure 2 The method presented by Fernandez (1991) was usedto show interrelationships among these three variables to sep-arate the Group A genotypes from the other groups (GroupsB C D) To compare with the micronutrient efficiency in-dex commonly used by plant nutritionists a correlation wasmade between the STI and Zn efficiency of wheat genotypesIt seems that STI is a good selection criterion for identifyinghigh-yield and stress-tolerant genotypes The X-Y plane is di-vided into four regions by drawing intersecting lines throughYs and Yp and the four groups are marked as Group A to

Group D (Fig 2) Most of the Group A genotypes showedhigh STI and genotypes in group D showed low STI valuesAnalysis of variance for grain yield and stress tolerance in-dices for wheat grown in zinc stress and non stress conditionsindicates that the STI indicator is less affected by the envi-ronment and its stability is more than other indices (Tab IV)Table V presents the calculated stress tolerance indices andmean grain yield of studied wheat genotypes grown in zincstress and non stress conditions Correlation coefficient be-tween stress tolerance indices and yield in zinc stress andnon stress conditions is also shown in Table VI The values


Table IV Analysis of variance for grain yield and stress tolerance indices in wheat in zinc stress and non stress conditions This table showsthe effect of environment on different stress indices and their relative stability GMP STI SSI MP TOL EF Yp and Ys are geometric meanproductivity stress tolerance index stress susceptibility index mean productivity tolerance index zinc-efficiency grain yield under with addedZn treatment and grain yield under without added Zn treatment respectively

GMP STI SSI MP TOL EF Yp Ys df Source of variationPr gt F

lt 0001 04948 07774 lt 0001 09666 07154 lt 0001 lt 0001 1 Placelt 0001 lt 0001 04551 lt 0001 03119 03153 lt 0001 lt 0001 19 Genotype

Table V Means of yield and stress tolerance indices in zinc stress and non stress conditions in wheat GMP STI SSI MP TOL EF Yp andYs are geometric mean productivity stress tolerance index stress susceptibility index mean productivity tolerance index zinc-efficiency grainyield under with added Zn treatment and grain yield under without added Zn treatment respectively

Cultivar Yp Ys EF TOL MP SSI STI GMPMahdavi 7112 7664 110 ndash552 7388 ndash279 116 7352Bezostaya 5957 5812 995 146 5884 ndash218 0734 5868Navid 7928 7222 92 706 7575 119 120 7533Alamoot 7566 7963 106 ndash397 7764 586 130 7750Alvand 8389 8575 102 ndash186 8482 43 153 8470Zarin 6973 7580 109 ndash607 7277 90 113 7250MV-17 6647 6293 959 354 6470 ndash135 0900 6453Gaspard 8397 7332 88 1034 7850 ndash756 135 7814Gascogen 6611 7131 108 ndash520 6871 ndash126 099 6853Sayson 7703 7617 992 862 7660 ndash505 127 7646Shahriar 7585 8029 107 ndash444 7807 ndash550 131 7786Toos 7712 8054 108 ndash343 7883 66 134 7845Sabalan 5500 5564 106 ndash63 5532 ndash60 0651 5497Roshan WBC 7384 7552 102 ndash168 7468 63 119 7454Shahi Cross 6861 6410 94 451 6636 433 091 6580Shahpasand 4838 3930 86 907 4384 305 0392 4303Omid 4706 4673 106 327 4689 159 0464 4653Azar2 6285 5182 90 1102 5734 ndash29 0674 5646Sardari 5710 4628 84 1083 5169 51 0558 5107C-81-10 7149 7236 103 ndash87 7192 ndash128 112 7163LSD 5 1272 812 215 1505 757 217 021 747

of STI are positively correlated to the grain yield producedboth in the presence and absence of added Zn In additiona very high and positive correlation was found between theSTI and MP indicator while there was no significant relation-ship between the STI values and the amounts of Zn-efficiencycalculated by the common formula (YsYp) used by severalresearchers It has been previously mentioned that some Zn-efficient genotypes have lower potential yields (Kalayci et al1999 Khoshgoftarmanesh et al 2004a)

The same results were achieved where a three-dimensionalplot among Ys (x-axis) Yp (y-axis) and STI (z-axis) wasdrawn based on grain yield of different bread wheat geno-types grown in severely Fe-deficient (stress condition) and Fe-fertilized soils (non-stress condition) (Fig 3) Higher valuesof STI were related to Genotypes in Group A (genotypes withhigher Fe efficiency and greater potential yield both in thepresence and absence of added Fe)

It seems using these stress indicators for separating propermicronutrient-efficient genotypes with higher potential yieldswould be useful in future studies Additionally developingnew stress indicators through including other desirable crite-

ria (ie concentrations of micronutrients as well as antinutri-ents and promoters in grains) is very useful in modern breed-ing programs In this way it would be possible to divide cropgenotypes into different groups based on both qualitative andquantitative aspects

6 CONCLUSION

We reviewed different possible approaches including soiland foliar fertilization crop systems application of soilamendments and organic sources and genetic and agronomicbiofortification to correct micronutrients deficiency and to in-crease their density in edible parts of plants

Soil application of fertilizer is the easiest way to correctmicronutrient deficiency however it is not always success-ful and sustainable due to agronomic and economic factorssuch as reduced availability of micronutrient element due totopsoil drying subsoil constraints disease interactions andcost of fertilizer in developing countries Foliar fertilizationis more effective than soil application but too expensive for


Table VI Coefficient of correlation between stress tolerance indices and yield in zinc stress and non stress conditions in wheat GMP STISSI MP TOL EF Yp and Ys are geometric mean productivity stress tolerance index stress susceptibility index mean productivity toleranceindex zinc-efficiency grain yield under with added Zn treatment and grain yield under without added Zn treatment respectively

Trait Ys Yp EF TOL MP SSI STI GMPYs 1Yp 091lowastlowast 1EF 016ns 055lowast 1MP ndash024ns ndash063lowastlowast ndash097lowastlowast 1TOL 097lowastlowast 098lowastlowast 038ns ndash047lowast 1SSI ndash012ns ndash006ns 009ns ndash007ns ndash008ns 1STI 096lowastlowast 097lowastlowast 038ns ndash046lowast 099lowastlowast ndash007ns 1GMP 097lowastlowast 098lowastlowast 039ns ndash047lowast 100lowastlowast ndash008ns 099lowastlowast 1

and significant at the 5 and 1 level of probability respectively ns non significant

Figure 3 The 3-D plot among stress tolerance index (STI) -Fe and +Fe condition for different winter wheat cultivars Group A genotypes thatare not affected by stress and produce the same in both stress and non-stress environments Group B genotypes that produce higher yield onlyin non-stress environments Group C genotypes with higher yield in stress condition and lower yield in non-stress environment and Group Dgenotypes with low yield in both stress and non-stress environments Mahdavi (1) Bezostaya (2) Navid (3) Alamoot (4) Alvand (5) Zarin(6) MV-17 (7) Gaspard (8) Gascogen (9) Sayson (10) Shahriar (11) Toos (12) Sabalan (13) Roshan Winter Back Cross (14) Shahi Cross(15) Shahpasand (16) Omid (17) Azar2 (18) Sardari (19) and C-81-10 (20) (Khoshgoftarmanesh et al 2007)


resource-poor farmers Seed priming is also an effective wayto increase yield and is important for resource-poor farmers Itseems a reasonable intercropping or rotation system of nutrientefficient species will help to prevent or mitigate micronutrientdeficiency of plants in agricultural practice

Selecting and breeding staple food crops which are moreefficient in the uptake of trace minerals from the soil andwhich load more trace minerals into their seeds combinesbenefits both for agricultural productivity and human nutri-tion Plant crop yield under stress could be enhanced byselection or breeding of plants that have high micronutrientefficiency and ability to interact effectively with environmen-tal extremes Cultivation of micronutrient-efficient crop geno-types may have important applications for increasing farm pro-ductivity in developing countries in an environmental-friendlyway This approach also holds great promise for making a sig-nificant low-cost and sustainable contribution to reducing mi-cronutrient deficiencies in humans

The combining of benefits for human nutrition and agri-cultural productivity resulting from breeding improved staplefood crops results in extremely high benefit-cost ratios for in-vestments in agricultural research in this area This approachwould be more valuable and cost-effective by estimating thecosts paid to heal micronutrient malnutrition in developingcountries

Despite beneficial effects of biofortified genotypes wefound the following major challenges in programs for se-lecting or breeding micronutrient-efficient genotypes (1)The stability in response to nutrient efficiency in differ-ent environments and relationships between crop produc-tivity mineral concentrations and other nutritional qualityfactors (eg concentrations of promoters and antinutrients)has less been considered (2) There is no reliable indica-tor for identifying micronutrient-efficient genotypes with highgrain yield It seems that the stress tolerance index STIcan be used to identify genotypes that produce high yieldsunder both non-stress and stress environments (3) In mostcases the crop yield has been considered as the main ba-sis for separating micronutrient-efficient and inefficient geno-types while micronutrient-efficient genotypes may even con-tain lower micronutrient concentrations in their edible partsthan micronutrient-inefficient genotypes Therefore combin-ing crop productivity and grain quality aspects such as to-tal content and bioavailability of nutrients in developing newmicronutrient-efficient genotypes is necessary (4) Breedingprograms to improve grain micronutrient concentration shouldcheck to assure that a toxic metal such as Cd is not being in-creased along with micronutrients

REFERENCES

Abedin MJ Cotter-Howells J Meharg AA (2002) Arsenic uptake andaccumulation in rice (Oryza sativa L) irrigated with contaminatedwater Plant Soil 240 311ndash319

ACCSCN (1992) Second Report on the World Nutrition Situation Vol IGlobal and Regional Results in Garcia M Mason J (Eds) pp 1ndash80 ACCSCN United Nations Geneva Switzerland

ACCSCN (1997) United Nations Report on World Nutrition The 3rdReport Chapter 2 Micronutrients pp 19ndash52 ACCSCN UnitedNations Geneva Switzerland

ACCSCN (2000) Ending malnutrition by 2020 An agenda for change inthe millennium Commission Report pp 1ndash110 ACCSCN UnitedNations Geneva Switzerland

Afyuni M Khoshgoftarmanesh AH Dorostkar V Moshiri R (2007)Zinc and Cadmium content in fertilizers commonly used in IranInternational Conference of Zinc-Crops May 24ndash28 IstanbulTurkey

Ahmed A Anjum FM Rehman SUr Randhava MA Farooq U(2008) Bioavailability of calcium iron and zinc fortified wholewheat flour Chapatti Plant Food Hum Nutr 63 7ndash13

Alam SM (1999) Nutrient uptake by plants under stress conditions inPessarakli M (Ed) Handbook of plant and crops stress MarcelDekker New York pp 285ndash313

Alexandratos N (1995) World Agriculture Towards 2010 An FAO StudyJohn Wiley and Sons Chichester West Sussex

Allen LH (2000) Ending Hidden Hunger the History of MicronutrientDeficiency Control Background Analysis for the World Bank-UNICEF Nutrition Assessment Project World Bank

Alvarez JM Gonzalez D (2006) Zinc transformations in neutral soiland zinc efficiency in maize fertilization J Agr Food Chem 549488ndash9495

Alvey S Bagayoko M Neumann G Buerkert A (2001) Cereallegumerotations affect chemical properties and biological activities in twoWest African soils Plant Soil 231 45ndash54

Andersson A (1983) Composted municipal refuse as fertilizer and soilconditioner Effects on the contents of heavy metals in soil andplant as compared to sewage sludge manure and commercial fertil-izers in Berglund S Davis RD LrsquoHermite P (Eds) Utilizationof Sewage Sludge on Land Rates of Application and Long-TermEffects of Metals D Reidel Publ Dordrecht pp 146ndash156

Atta SK Mohammed SA van Cleemput O Zayed A (1996)Transformations of iron and manganese under controlled Eh Eh-pH conditions and additions of organic matter Soil Technol 9223ndash237

Bagci SA Ekiz H Yilmaz A Cakmak I (2007) Effects of zinc defi-ciency and drought on grain yield of field-grown wheat cultivars inCentral Anatolia J Agron Crop Sci 193 198ndash206

Baligar VC Duncan RR Fageria NK (1990) Soil-plant interactionson nutrient use efficiency in plants An overview in Baligar VCDuncan RR (Eds) Crops as enhancers of nutrient use AcademicPress San Diego California pp 351ndash373

Baligar VC Fageria NK He ZL (2001) Nutrient use efficiency inplants Commun Soil Sci Plant Anal 32 921ndash950

Barker AV Pilbeam DJ (2007) Handbook of Plant Nutrition Taylorand Francis Group Press Boca Raton FL

Barnes JP Putnam AR (1986) Evidence for allelopathy by residues andaqueous extracts of rye (Secale cereale L) Weed Sci 34 384ndash390

Barrier-Guillot B Casado P Maupetit P Jondreville C Gatel F (1996)Wheat phosphorus availability In vitro Study Factors affectingendogenous phytasic activity and phytic phosphorus content J SciFood Agr 70 62ndash68

Bhowmik PC Doll JD (1984) Allelopathic effects of annual weedresidues on growth and nutrient uptake of corn and soybeansAgron J 76 383ndash388

Black R (2003) Micronutrient deficiency mdash an underlying cause for mor-bidity and mortality B World Health Organ 2003 81ndash79


Blair G (1993) Nutrient efficiency-what do we really mean in RandallPJ Delhaize E Richards RA Munns R (Eds) Genetic aspectsof mineral nutrition Kluwer Academic Publishers Dordrecht TheNetherlands pp 205ndash213

Blum A (1988) Plant Breeding for Stress environments CRC PressFlorida p 212

Borlaug NE Dowswell CR (1993) Fertilizer To nourish infertile soilthat feeds a fertile population that crowds a fragile world FertilNews 387 11ndash20

Bouis H (1996) Enrichment of food staples through plant breeding Anew strategy for fighting micronutrient malnutrition Nutr Rev 54131ndash137

Brabin BJ Coulter JBS (2003) Nutrition-associated disease in CookGC Zumla AI (Eds) Mansonrsquos tropical diseases SaundersLondon pp 561ndash580

Brady NC Weil RR (2002) The nature and properties of soils 13thedition Prentice Hall Upper Saddle River New Jersey

Brennan RF (1992) Effect of zinc fertilizer on take-all and grain yield ofwheat grown on zinc deficient soils of the esperance region WestAust Fer Res 31 215ndash216

Brennan RF Bolland MDA (2006) Residual values of soil-appliedzinc fertiliser for early vegetative growth of six crop species AustJ Exp Agr 46 1341ndash1347

Broadley MR White PJ Bryson RJ Meacham MC Bowen HCJohnson SE Hawkesford MJ McGrath SP Zhao FJ BrewardN Harriman M Tucker M (2006) Biofortification of UK foodcrops with selenium Proc Nutr Soc 65 169ndash181

Bronick CJ Lal R (2005) Manuring and rotation effects on soil organiccarbon concentration for different aggregate size fractions on twosoils in northeastern Ohio USA Soil Till Res 81 239ndash252

Brown LR (1997) Facing the challenge of food scarcity Can we raisegrain yields fast enough in Ando T Fujita K Mae T MatsumotoH Mori S Sekiya J (Eds) Plant nutrition for sustainablefood production and environment Kluwer Academic PublishersDordrecht The Netherlands pp 15ndash24

Buso GSC Bliss FA (1988) Variability among lettuce cultivars grownat two levels of available phosphorus Plant Soil 111 67ndash73

Buyckx M (1993) The international communityrsquos commitment to com-bating micronutrient deficiencies Food Nutr Agr 7 2ndash7

Byrnes BH Bumb BL (1998) Population growth food productionand nutrient requirements in Rengel Z (Ed) Journal of CropProduction The Haworth Press New York pp 1ndash27

Cai S Yue L Jin T Nordberg G (1998) Renal dysfunction from cad-mium contamination of irrigation water Dose-response analysis ina Chinese population B World Health Organ 76 153ndash159

Cakmak I (2002) Plant nutrition research Priorities to meet human needsfor food in sustainable ways Plant Soil 247 3ndash24

Cakmak I (2008) Enrichment of cereal grains with zinc Agronomic orgenetic biofortification Plant Soil 302 1ndash17

Cakmak I Marschner H (1986) Mechanism of phosphate induced zincdeficiency in cotton I Zinc deficiency-enhanced uptake rate ofphosphorus Physiol Plant 68 483ndash490

Cakmak I Sari N Marschner H Ekiz H Kalayci M Yilmaz A BraunHJ (1996) Phytosiderophore release in bread and durum wheatgenotypes differing in zinc efficiency Plant Soil 180 183ndash189

Cakmak I Ekiz H Yilmaz A Torun B Koleli N Gultekin I AlkanA Eker S (1997a) Differential response of rye triticale bread anddurum wheats to zinc deficiency in calcareous soils Plant Soil 1881ndash10

Cakmak I Derici R Torun B Tolay I Braun HJ Schlegel R (1997b)Role of rye chromosomes in improvement of zinc efficiency inwheat and triticale Plant Soil 196 249ndash253

Cakmak I Torun B Erenoglu B Oztuumlrk L Marschner H Kalayci MEkiz H Yilmaz A (1998) Morphological and physiological dif-ferences in cereals in response to zinc deficiency Euphytica 100349ndash357

Caradus JR (1990) Mechanisms improving nutrient use by crop andherbage legumes in Baligar VC Duncan RR (Eds) Crops asenhancers of nutrient use San Diego Academic Press Californiapp 253ndash311

Carr AJH Stoddart JL (1963) The ameliorating effect of zinc on symp-toms of phyllody virus in white clover Ann Appl Biol 51 259ndash268

Cary EE Norvell WA Grunes DL Welch RM Reid WS (1994)Iron and Manganese Accumulation by the brz Pea Mutant Grownin Soils Agron J 86 938ndash41

Chaney RL Ryan JA (1993) Heavy metals and toxic organic pol-lutants in MSW-composts Research results on phytoavailabil-ity bioavailability etc in Hoitink HAJ Keener HM (Eds)Science and Engineering of Composting Design EnvironmentalMicrobiological and Utilization Aspects Ohio State UnivColumbus OH pp 451ndash506

Chaney RL Reeves PG Ryan JA Simmons RW Welch RM AngleJS (2004) An improved understanding of soil Cd risk to humansand low cost methods to remediate soil Cd risks BioMetals 17549ndash553

Christian P West KP Jr (1998) Interactions between zinc vitamin AAn update Am J Clin Nutr 68 (Suppl) S435ndashS441

Clark RB (1990) Physiology of cereals for mineral nutrient uptake useand efficiency in Baligar VC Duncan RR (Eds) Crops as en-hancers of nutrient use Academic Press San Diego Californiapp 131ndash209

Cobiac L Baghurst K (1993) Iron status and dietary iron intakes ofAustralians CSIRO Astralia Adelaide SA

Combs GF Jr Welch RM (1998) Creating Healful Food SystemsLinking Agriculture to Human Needs Cornell InternationalInstitute for Food Agriculture and Development CornellUniversity Ithaca NY pp 1ndash34

Combs GF Jr Welch RM Duxbury JM Uphoff NT Nesheim MC(1996) Food-Based Approaches to Preventing MicronutrientMalnutrition an International Research Agenda CornellInternational Institute for Food Agriculture and DevelopmentCornell University Ithaca NY pp 1ndash68

Cottenie A Kang BT Kieken SL Sajjapongse A (1981)Micronutrient status in Greenland DJ (Ed) Characterization ofSoils Clarendon Oxford UK pp 149ndash163

DellaPenna D (1999) Nutritional genomics manipulating plant micronu-trients to improve human health Science 285 375ndash379

Diekow JJ Mielniczuk J Knicker H Bayer C Dick DPKoumlgel-Knabner I (2005) Soil C and N stocks as affected by crop-ping systems and nitrogen fertilisation in a southern Brazil Acrisolmanaged under no-tillage for 17 years Soil Till Res 81 87ndash95

Donald CM Prescot JA (1975) Trace elements in Australian cropand pasture production in Nicholas DJD Egan RA (Eds)Trace Elements in Soil-Plant-Animal Systems Academic PressNew York pp 7ndash37

Drakakaki G Marcel S Glahn RP Lund EK Pariagh S Fischer FChristou P Stoger E (2005) Endosperm-specific co-expression ofrecombinant soybean ferritin and Aspergillus phytase in maize re-sults in significant increases in the levels of bioavailable iron PlantMol Biol 59 869ndash880


Eghball B Ginting D Gilley JE (2004) Residual effects of manureand compost applications on corn production and soil propertiesAgron J 96 442ndash447

Erdal I Yilmaz A Taban S Eker S Torun B Cakmak I (2002)Phytic acid and phosphorus concentrations in seeds of wheat cul-tivars grown with and without zinc fertilization J Plant Nutr 25113ndash127

Fageria NK (2000a) Adequate and toxic levels of boron for rice com-mon bean corn soybean and wheat production in Cerrado soil RBras Eng Agr Ambiental 4 57ndash62

Fageria NK (2000b) Adequate and toxic levels of zinc for rice commonbean corn soybean and wheat production in Cerrado soil R BrasEng Agr Ambiental 4 390ndash395

Fageria NK Baligar VC (2003) Methodology for evaluation of lowlandrice genotypes for nitrogen use efficiency J Plant Nutr 26 1315ndash1333

Fageria NK Barbosa Filho MP (2001) Nitrogen use efficiency in low-land rice genotypes Commun Soil Sci Plan 32 2079ndash2089

Fageria NK Baligar VC Clark RB (2002) Micronutrients in crop pro-duction Adv Agron 77 185ndash268

Fageria NK Baligar VC Li YC (2008) The role of nutrient efficientplants in improving crop yields in the twenty first Century J PlantNutr 31 1121ndash1157

FAO (Food and Agriculture Organization) (1999) Yearbook of FertilizersFood and Agriculture Organization of the United Nations RomeItaly

Fernandez GCJ (1991) Analysis of cultivar times environment interactionby stability estimates HortScience 26 947ndash950

Fernandez GCJ Chen HK Miller JC Jr (1989) Adaptation andenvironmental sensitivity of mungben genotypes evaluated in theInternational Mungbean Nursery Euphytica 41 253ndash261

Fischer RA Maurer R (1978) Drought resistance in spring wheat culti-vars I Grain yield responses Aust J Agr Res 29 897ndash912

Fleming GA Mordenti A (1991) The Production of Animal WastesEuropean Conference on Environment and Agriculture StockFarming in Europe Mantua Italy

Food and Agriculture Organization of the United Nations (2004)Undernourishment around the world in The state of food insecu-rity in the world 2004 The Organization Rome

Foy CD (1984) Physiological effects of hydrogen aluminum and man-ganese toxicities in acid soils in Adams F (Ed) Soil Acidity andLiming 2nd ed American Society of Agronomy Madison WIpp 57ndash97

Foy CD (1992) Soil chemical factors limiting plant growth Limitationsto Plant Root Growth in Hatfield JL Stewart BA (Eds) AdvSoil Sci 19 97ndash149

Frey KJ (1964) Adaption reaction of oat strains selected under stress andnon-stress environmental condition Crop Sci 4 55ndash58

Frossard E Bucher M Maumlchler F Mozafar A Hurrell R (2000)Potential for increasing the content and bioavailability of Fe Zn andCa in plants for human nutrition J Sci Food Agr 80 861ndash879

Galratildeo EZ (1999) Methods of copper application and evaluation of itsavailability for soybean grown on a Cerrado red-yellow latosol RBras Ci Solo 23 265ndash272

Gao M Che FC Wei CF Xie DT Yang JH (2000) Effect of long-term application of manures on forms of Fe Mn Cu and Zn inpurple paddy soil Plant Nutr Fertil Sci 6 11ndash17

Garcia-Casal MN Layrisse M Solano L Baron MA Arguello FLIovera D Ramirez J Leets I Tropper E (1998) Vitamin A

and beta carotene can improve nonheme iron absorption from ricewheat and corn by humans J Nutr 128 646ndash650

Gargari BP Mahboob S Razavieh SV (2007) Content of phytic acidand its mole ratio to zinc in flour and breads consumed in TabrizIran Food Chem 100 1115ndash1119

Gerloff Gabelman (1983) Genetic basis of inorganic plant nutritionin Lauchli A Bieleski RL (Eds) Inorganic Plant NutritionEncyclopedia and Plant Physiology New Series Springer VerlagNew York NY Vol 15B pp 453ndash480

Gibson RS (1994) Zinc nutrition in developing countries Nutr Res Rev7 151ndash173

Gibson RS (2006) Zinc the missing link in combating micronutrientmalnutrition in developing countries Proc Nutr Soc 65 51ndash60

Gibson RS Sazawal S Peerson JM (2003) Design and quality con-trol issues related to dietary assessment randomized clinical trialsand meta-analysis of field-based studies in developing countries JNutr 133 (5 Suppl 1) 1569sndash1573s

Gibson RS Hess SY Hotz C Brown KH (2008) Indicators of zincstatus at the population level a review of the evidence Brit J Nutr99 (Suppl 3) S14ndashS23

Glass ADM (1989) Physiological mechanisms involved with genotypicdifferences in ion adsorption and utilization HortScience 24 559ndash564

Godwin DC Blair GJ (1991) Phosphorus efficiency in pasture speciesV A comparison of white clover accessions Aust J Agr Res 42531ndash540

Gonzalez D Obrador A Alvarez JM (2007) Behavior of zinc from sixorganic fertilizers applied to a navy bean crop grown in a calcareoussoil J Agr Food Chem 55 7084ndash7092

Goto F Yoshihara T Shigemoto N Toki S Takaiwa F (1999) Iron for-tification of rice seed by the soybean ferritin gene Nat Biotechnol17 282ndash286

Goto K Tanimoto Y Tamura T Mochida K Arai D Asahara MSuzuki M Tanaka H Inagaki K (2002) Identification of ther-moacidophilic bacteria and a new Alicyclobacillus genomic speciesisolated from acidic environments in Japan Extremophiles 6 333ndash340

Gourley CJP Allan DL Russelle MP (1994) Plant nutrient efficiencyA comparison of definitions and suggested improvement Plant Soil158 29ndash37

Graham RD (1984) Breeding for nutritional characteristics in cereals inTinker PB Lauchi A (Eds) Advances in plant nutrition Vol 1Praeger Publisher New York pp 57ndash102

Graham RD Webb MJ (1991) Micronutirents and disease resistanceand tolerance in plants in Mortvadt JJ Cox FR Shuman LMWelch RM (Eds) Micronutrients in Agriculture 2nd ed SoilScienc Society American Book series No 4 Madison WI pp 329ndash370

Graham RD Rengel Z (1993) Genotypic variation in zinc uptake andutilization by plants in Robson AD (Ed) Zinc in Soils andPlants Kluwer Academic Publishers Dordrecht pp 107ndash118

Graham RD Welch RM (1996) Breeding for staple-food cropswith high micronutrient density Agricultural Strategies forMicronutrients Working Paper No 3 International Food PolicyResearch Institute Washington DC

Graham RD Ascher JS Hynes SC (1992) Selecting zinc efficient ce-real genotypes for soils of low zinc status Plant Soil 146 241ndash250

Graham RD Senadhira D Beebe SE Iglesias C Ortiz-MonasterioI (1999) Breeding for micronutrients density in edible portions ofstaple food crops conventional approaches Field Crop Res 6057ndash80


Graham RD Humphries JM Kitchen JL (2000) Nutritionally en-hanced cereals A sustainable foundation for a balanced diet AsiaPac J Clin Nutr 9 (Suppl) S91ndashS96

Graham RD Welch RM Bouis HE (2001) Addressing micronutri-ent malnutrition through enhancing the nutritional quality of staplefoods Principles perspectives and knowledge gaps Adv Agron70 77ndash142

Grant CA Clarke JM Duguid S Chaney RL (2008) Selection andbreeding of plant cultivars to minimize cadmium accumulation SciTotal Environ 390 301ndash310

Grewal HS Graham RD (1999) Residual effects of subsoil zinc andoilseed rape genotype on the grain yield and distribution of zinc inwheat Plant Soil 207 29ndash36

Gunes A Inal A Adak MS Alpaslan M Bagci EG Erol TPilbeam DG (2007) Mineral nutrition of wheat chickpea andlentil as affected by mixed cropping and soil moisture Nutr CyclAgroecosys 78 83ndash96

Hacisalihoglu G (2002) Physiological and biochemical mechanisms un-derlying zinc efficiency in monocot and dicot crop plants PhDThesis Cornell University Ithaca New York USA

Harris D Rashid A Miraj Gh Arif M Yunas M (2008) rsquoOn-farmrsquoseed priming with zinc in chickpea and wheat in Pakistan PlantSoil 306 3ndash10

Harris D Rashid A Miraj Gh Arif M Shah H (2007) rsquoOn-farmrsquo seedpriming with zinc in chickpea and wheat in Pakistan Plant Soil 3063ndash10

Hart JJ Welch RM Norvell WA Kochian LV (2002) Transport in-teractions between cadmium and zinc in roots of bread and durumwheat seedlings Physiol Plantarum 116 73ndash78

Hill CH Matrone G (1970) Chemical parameters in the study of in vivoand in vitro interactions of transition elements Fed Proc 29 1474ndash1481

Hodges RE Saurberlich HE Canham JE Wallace DL Rucker RBMejia LA Mohanram M (1978) Hematopoietic studies in vitaminA deficiency Am J Clin Nutr 31 876ndash885

House WA (1999) Trace element bioavailability as exemplified by ironand zinc Field Crop Res 60 115ndash141

Huber DM Abney TS (1986) Soybean allelopathy and subsequentcropping J Agron Crop Sci 157 73ndash78

Hylander LD (1995) Effects of lime phosphorus manganese copperand zinc on plant mineral composition yield of barley and levelof extractable nutrients for an acid Swedish mineral soil CommunSoil Sci Plan 26 2913ndash2928

International Zinc Nutrition Consultative Group (IZiNCG) (2004)Assessment of the risk of zinc deficiency in populations and optionsfor its control in Hotz C Brown KH (Eds) Food and nutritionbulletin Vol 25 No 1 Suppl 2 pp S113ndashS118

Isfan D (1993) Genotypic variability for physiological efficiency indexof nitrogen in oats Plant Soil 154 53ndash59

Kalayci M Torun B Eker S Aydin M Ozturk L Cakmak I (1999)Grain yield zinc efficiency and zinc concentration of wheat culti-vars grown in a zinc-deficient calcareous soil in field and green-house Field Crop Res 63 87ndash98

Kang YL (1988) Effects of organic matter and its anaerobic decomposi-tion products on the growth and zinc uptake by Oryza sativa DisserAbst Int B (Sci Eng) 49 953B

Kannenberg LW Falk DE (1995) Models for activation of plant geneticresources for crop breeding programs Can J Plant Sci 75 45ndash53

Katyal JC (1977) Influence of organic matter on the chemical and elec-trochemical properties of some flooded soils Soil Biol Biochem9 259ndash266

Katyal JC Vlek PLG (1985) Micronutrient problems in tropical AsiaFert Res 7 69ndash94

Keller A Schulin R (2003) Modelling heavy metal and phosphorus bal-ances for farming systems Nutr Cycl Agroecosys 66 271ndash284

Khoshgoftarmanesh AH M Kalbasi (2002) Effect of Municipal wasteLeachate on soil properties and growth and yield of rice CommunSoil Sci Plan 33 2011ndash2020

Khoshgoftar AH HajiMozaffari E (2006) Approaches to enhance ironconcentration in wheat grain produced in Qom province Iran 2ndCentral Asian Cereals Conference June 13ndash16 2006 Cholpon-AtaIssyk Kul Lake Kyrgyz Republic

Khoshgoftar AH Chaney RL (2007) Preceding crop affects grain cad-mium and zinc of wheat grown in saline soils of central Iran JEnviron Qual 36 1132ndash1136

Khoshgoftarmanesh AH Shariatmadari H Kalbasi M Karimian N(2004a) Zinc efficiency of wheat cultivars grown on a saline cal-careous soil J Plant Nutr 27 1953ndash1962

Khoshgoftar AH Shariatmadari H Karimian N Kalbasi Mvan der Zee SEATM Parker DR (2004b) Salinity and Zn ap-plication effects on phytoavailability of Cd and Zn Soil Sci SocAm J 68 1885ndash1889

Khoshgoftar AH Shariatmadari H Karimian N and van der ZeeSEATM (2006a) Cadmium and zinc in saline soil solutions andtheir concentrations in wheat Soil Sci Soc Am J 70 582ndash589

Khoshgoftar AH Shariatmadari H Karimian N (2006b) Responses ofwheat genotypes to zinc fertilization under saline soil conditions JPlant Nutr 27 1ndash14

Khoshgoftarmanesh AH Sharifi HR Mirzapour MH Schulin R(2007) Plant genotype and Zn fertilization effects on nutritionalquality of wheat grain produced in saline soils 9th InternationalConference of the Biochemistry of Trace Elements (ICOBTE) July2007 Beijing China

Kochian LV (1995) Cellular mechanisms of aluminum toxicity and re-sistance in plants Annu Rev Plant Phys 46 237ndash260

Leon LA Lopez AS Vlek PLG (1985) Micronutrient problems intropical Latin America Fert Res 7 95ndash129

Liu XJ Liao XY Zhang YZ Huang YX (2002) Effects of ricebasedcropping system on the distribution of manganese in the profile ofpaddy soil derived from red earth Acta Ecol Sin 22 1440ndash1445

Loneragen JP (1997) Plant nutrition in 20th and perspectives for the 21stcentury Plant Soil 196 163ndash174

Lopes AS Cox FR (1977) A survey of the fertility status of surfacesoils under lsquoCerradorsquo vegetation in Brazil Soil Sci Soc Am J 41742ndash747

Lucca P Hurrell RF Potrykus I (2001) Genetic engineering approachesto improve the bioavailability and the level of iron in rice grainsTheor Appl Genet 102 392ndash397

Marschner H (1995) Mineral Nutrition of Higher Plants 2nd edAcademic Press London

Mason JB Garcia M (1993) Micronutrient deficiency ndash the global situ-ation SCN News 9 11ndash16

Martens DC Westerman DT (1991) Fertilizer applications for correct-ing micronutrient deficiencies in Mortvedt JJ Cox FR ShumanLM Welch RM (Eds) Micronutrients in Agriculture 2nd edSSSA Book Series 4 SSSA Madison WI pp 549ndash592

Martens DC Lindsay WL (1990) Testing soils for copper iron man-ganese and zinc in Westerman RL (Ed) Soil Testing and PlantAnalysis Soil Science Society of America Madison WI pp 229ndash273


Mayer JE Pfeiffer WH Beyer P (2008) Biofortified crops to alleviatemicronutrient malnutrition Curr Opin Plant Biol 11 166ndash170

McGuire J (1993) Addressing micronutrient malnutrition SCN News 91ndash10

McIntyre BD Bouldin DR Urey GH Kizito F (2001) Modelingcropping strategies to improve human nutrition in Uganda AgrSyst 67 105ndash120

McLaughlin MJ Parker DR Clarke JM (1999) Metals and micronu-trients - Food safety issues Field Crop Res 60 143ndash163

Meharg AA (2004) Arsenic in rice - understanding a new disaster forSouth-East Asia Trends Plant Sci 9 415ndash417

Menzi H Kessler J (1998) Heavy metal content of manures inSwitzerland in Proceedings of the Eighth International Conferenceof the FAO Network on Recycling of Agricultural Municipal andIndustrial Residues in Agriculture (in press)

Miller D Waissman N Melton B Currier C McCaslin B (1987)Selection for increased phosphorus in alfalfa and effects on othercharacteristics Crop Sci 27 22ndash26

Mitchell CC Entry JA (1998) Soil C N and crop yields in Alabamarsquoslong-term lsquoold rotationrsquo cotton experiment Soil Till Res 47 331ndash338

Mortvedt JJ (1985) Plant uptake of heavy metals in zinc fertilizers madefrom industrial by-products J Environ Qual 14 424ndash427

Mortvedt JJ (1994) Needs for controlled-availability micronutrient fer-tilizers Fert Res 38 213ndash221

Mortvedt JJ (1996) Heavy metal contaminants in inorganic and organicfertilizers Fert Res 43 55ndash61

Murray CJL Lopez AD (1997) Global mortality disability and thecontribution of risk factors Global Burden of Disease Study Lancet349 1436ndash42

Nable RO Webb MJ (1993) Further evidence that zinc is requiredthroughout the root zone for optimal growth and development PlantSoil 150 247ndash253

Neidecker-Gonzales O Nestel P Bouis H (2007) Estimating the globalcosts of vitamin A capsule supplementation A review of the litera-ture Food Nutr Bull 28 307ndash316

Nicholson FA Chambers BJ Williams JR Unwin RJ (1999) Heavymetal contents of livestock feeds and animal manures in Englandand Wales Bioresource Technol 70 23ndash31

Nicklas TA (1995) Dietary studies of children the Bogalu Heart Studyexperience J Am Diet Assoc 95 1127ndash1133

Nogawa K Kobayashi E Okubo Y Suwazono Y (2004) Environmentalcadmium exposure adverse effects and preventive measures inJapan BioMetals 17 581ndash587

Novack B Schwyzer I Schulin R (2008) Uptake of Zn and Fe byWheat (Triticum aestivum var Greina) and Transfer to the Grains inthe Presence of Chelating Agents (Ethylenediaminedisuccinic Acidand Ethylenediaminetetraacetic Acid) Agr Food Chem 56 4643ndash4649

OrsquoDell BL de Boland AR Koirtyohann SR (1972) Distribution ofphytate and nutritionally important elements among the morpho-logical components of cereal grains J Agr Food Chem 20 718ndash721

Pareek S Pareek S (1999) Effect of macro-and micro-nutrients on char-coal rot disease development of maize induced by Macrophomineaphaseolina Ann Agr Res 20 129ndash131

Pessarakli M (ed) (1999) Handbook of plant and crops stress MarcelDekker New York

Pinstrup-Andersen P (1999) Selected aspects of the future global foodsituation in 25th International Fertilizer Industry AssociationEnlarged Council Meeting Rome Italy

Prasad B (1999) Conjoint use of fertilizers with organics crop residuesand green manuring for their efficient use in sustainable crop pro-duction Fert News 44 67ndash73

Prasad B Sinha MK (1981) The relative efficiency of zinc carriers ongrowth and zinc nutrition of corn Plant Soil 62 45ndash52

Prasad B Sinha SK (1995a) Effect of recycling of crop residues andorganic manure on capacity factor and diffusion rate of zinc in cal-careous soil J Nucl Agr Biol 24 185ndash188

Prasad B Sinha SK (1995b) Nutrient recycling through crop residuesmanagement for sustainable rice and wheat production in calcare-ous soil Fert News 40 15ndash2325

Raboy V Noaman MW Taylor GA Pickett SG (1991) Grain phyticacid and protein are highly correlated in winter wheat Crop Sci 31631ndash635

Raj H Gupta VK (1986) Influence of organic manures and zinc onwheat yield and Zn concentration in wheat Agr Wastes 16 255ndash263

Ramalingaswami V (1995) New global perspectives on overcoming mal-nutrition Am J Clin Nutr 61 259ndash263

Reeves PG Chaney RL (2008) Bioavailability as an issue in risk as-sessment and management of food cadmium A review Sci TotalEnviron 398 13ndash19

Rengel Z (2001) Genotypic differences in micronutrient use efficiency incrops Commun Soil Sci Plan 32 1163ndash1186

Rengel Z Graham RD (1995) Importance of seed Zn content for wheatgrowth on Zn-deficient soil 2 Grain yield Plant Soil 173 267ndash274

Rengel Z Batten GG Crowley DE (1999) Agronomic approachesfor improving the micronutrient density in edible portions of fieldcrops Field Crop Res 60 27ndash40

Reuter DJ Alston AM McFarland JD (1988) Occurrence and correc-tion of manganese deficiency in plants in Graham RD HannanRJ Uren NC (Eds) Manganese in Soils and Plants KluwerAcademic Dordrecht The Netherlands pp 205ndash224

Rice EL (1984) Allelopathy 2nd ed Academic Press Orlando FL422 p

Rose SJ Burnside OC Specht JE Swisher BA (1984) Competitionand allelopathy between soybeans and weeds Agron J 76 523ndash528

Rosegrant MW Leach N Gerpacio RV (1999) Alternative future forworld cereal and meat consumption Proc Nutr Soc 58 219ndash 234

Rosegrant MW Paisner MS Meijer S Witcover J (2001) 2020 GlobalFood Outlook Trends Alternatives and Choices A 2020 Visionfor Food Agriculture and the Environment Initiative InternationalFood Policy Research Institute Washington DC

Rosielle AA Hamblin J (1981) Theoretical aspects of selection foryield in stress and non-stress environments Crop Sci 21 943ndash946

Sanghvi TG (1996) Economic Rationale for Investing in MicronutrientPrograms A Policy Brief Based on New Analyses Office ofNutrition Bureau for Research and Development United StatesAgency for International Development Washington DC

Sauerbeck DR Helal HM (1990) Factors affecting the nutrient ef-ficiency in plants in El Balsam N Dambroth M LoughmanBC (Eds) Genetic Aspects of Plant Mineral Nutrition KluwerAcademic Publisher Dordrecht the Netherlands pp 11ndash17

Schulin R Khoshgoftarmanesh A Afyuni M Nowack B Frossard E(2009) Effect of soil management on zinc uptake and its bioavail-ability in plants in Banuelos GS Lin Z (Eds) Development and


uses of biofortified agricultural products CRC Press Boca RatonFL

Shaver TM Westfall DG Ronaghi M (2007) Zinc fertilizer solubilityand its effects on zinc bioavailability over time J Plant Nutr 30123ndash133

Siddiqi MY Glass AD (1981) Utilization Index A modified approachto the estimation and comparison of nutrient utilization efficiencyin plants J Plant Nutr 4 289ndash302

Sillanpaa M (1982) Micronutrients and Nutrient Status of Soils AGlobal Study Food and Agriculture Organization Rome FAO SoilBull No 48

Sillanpaa M Vlek PLG (1985) Micronutrients and the agroecology oftropical and Mediterranean regions Fert Res 7 151ndash168

Sims JT Wolf DC (1994) Poultry waste management Agricultural andEnvironmental issues Adv Agron 52 2ndash72

Singh G Abrol IP Cheema SS (1989) Effects of gypsum applicationon mesquite (Prosopisjulitlora) and soil properties in an abandonedsodic soil Forest Ecol Manag 29 1ndash14

Singh B Natesan SKA Singh BK Usha K (2005) Improving zincefficiency of cereals under zinc deficiency Curr Sci 88 36ndash44

Soil Science Society of America (1997) Glossary of soil science termsSoil Science Society of America Madison Wisconsin

Solomons NW Russell RM (1980) The interaction of vitamin A andzinc Implications for human nutrition Am J Clin Nutr 33 2031ndash2040

Stein AJ (2006) Micronutrient Malnutrition and the Impact of ModernPlant Breeding on Public Health in India How Cost-effective isBiofortification Cuvillier Verlag

Stein AJ Nestel P Meenakshi JV Qaim M Sachdev HP Bhutta ZA(2007) Plant breeding to control zinc deficiency in India how cost-effective is biofortification Public Health Nutr 10 492ndash501

Stevenson FJ (1991) Organic matter-micronutrient reaction in soil inMortvedt JJ et al (Eds) Micronutrients in Agriculture Soil SciSoc Am Madison WI pp 145ndash186

Stevenson FJ (1994) Humus chemistry Genesis composition ReactionWiley New York p 496

Stewart WM Dibb DW Johnston AE Smyth TJ (2005) The contri-bution of commercial fertilizer nutrients to food production AgronJ 97 1ndash6

Streeter JG (2001) Simple partial purification of D-pinitol from soybeanleaves Crop Sci 41 1985ndash1987

Swaddiwudhipong W Limpatanachote P Mahasakpan P KrintratunS Padungtod C (2007) Cadmium-exposed population in Mae SotDistrict Tak Province 1 Prevalence of high urinary cadmium lev-els in the adults J Med Assoc Thai 90 143ndash148

Tagwira F (1993) Some chemical and physical factors that associatedwith micronutrient status and availability in Zimbabwean soilsZimbabwean J Agr Res 31 1051ndash1059

Takkar PN Walker CD (1993) The distribution and correction of zincdeficiency in Robson AD (Ed) Zinc in Soils and Plants KluwerAcademic Publishers Dordrecht The Netherlands pp 151ndash165

Thung M (1988) Phosphorus A limiting nutrient in bean (Phaseolus vul-garis L) production in Latin America and field screening for effi-ciency and response in Bassam N Dambroth MC LoughmanBC (Eds) Genetic Aspects of Plant Mineral Nutrition KluwerAcademic Publishers Dordrecht pp 501ndash521

Thongbai P Hannam RJ Graham RD Webb MJ (1993) Interactionbetween zinc nutritional status of cereals and Rhizoctonia root rotseverity I Field observation Plant Soil 153 207ndash214

Tillman D (1999) Global environmental impacts of agricultural expan-sion the need for sustainable and efficient practices Proc NatlAcad Sci (USA) 96 5995ndash6000

Timsina J Connor DJ (2001) Productivity and management of rice-wheat cropping systems Isssues and challenges Field Crop Res69 93ndash132

Torun A Guumlltekin I Kalayci M Yilmaz A Eker S Cakmak I (2001)Effects of zinc fertilization on grain yield and shoot concentrationsof zinc boron and phosphorus of 25 wheat cultivars grown on azinc-deficient and boron-toxic soil J Plant Nutr 24 1817ndash1829

UNICEF Vitamin A Supplementation A Decade of Progress (2007) TheUnited Nations Childrenrsquos Fund (UNICEF)

United Nations General Assembly (2000) United Nations MillenniumDeclaration ARES552

United Nations Administrative Committee on Coordination ndashSubcommittee on Nutrition Situation (1992) Vol 1 Globaland Regional Results World Health Organization GenevaSwitzerland pp 1ndash80

US Department of Health and Human Services Healthy people 2000Nutrition Today (1990) NovemberDecember 29ndash30

Verna TS Minhas RS (1987) Zinc and phosphorus interaction in awheat-maize cropping system Fert Res 13 77ndash86

Vijayaraghavan K (2002) Control of micronutrient deficiencies in Indiaobstacles and strategies Nutr Rev 60 S73ndashS76

Walker DW Jenkins DD (1986) Influence of sweet potato plant residueon growth of sweet potato vine cuttings and cowpea plants HortSci21 426ndash428

Walker DW Hubbell TJ Sedberry JE (1989) Influence of decayingsweet potato crop residues on nutrient uptake of sweet potato plantsAgr Ecosyst Environ 26 45ndash52

Wallace A Mueller RT (1973) Effects of chelated and non-chelatedcobalt and copper on yields and microelement composition of bushbeans grown on calcareous soil in a glasshouse Soil Sci Soc AmProc 37 904ndash908

Wallace GA Wallace A (1982) Micronutrient uptake by leaves fromfoliar sprays of EDTA chelated metals in Nelson SD (Ed) IronNutrition and Interactions in Plants Marcel Dekker Basel pp 975ndash978

Webber MD Webber LR (1983) Micronutrients and heavy metalsin livestock and poultry manures in Farm Animal Manures inthe Canadian Environment Publication No NRCC 18976 of theEnvironmental Secretariat Ottawa Canada p 59

Wei X Hao M Shao M Gale WJ (2006) Changes in soil propertiesand the availability of soil micronutrients after 18 years of croppingand fertilization Soil Till Res 91 120ndash130

Welch RM (1998) Fashioning healthful agricultural systems in CombsGF Jr Welch RM (Eds) Creating Healthful Food SystemsLinking Agriculture to Human Needs Cornell International Institutefor Food Agriculture and Development Cornell University IthacaNY pp 7ndash13

Welch RM (1999) Importance of seed mineral nutrient reserves in cropgrowth and development in Rengel Z (Ed) Mineral Nutrition ofCrops Fundamental Mechanisms and Implications Food ProductsPress New York pp 205ndash226

Welch RM (2002) The impact of mineral nutrients in food crops onglobal human health Plant Soil 247 83ndash90

Welch RM Graham RD (1999) A new paradigm for world agriculturemeeting human needs ndash Productive sustainable nutritious FieldCrop Res 60 1ndash10


Welch RM Graham RD (2000) A new paradigm for world agricultureproductive sustainable nutritious healthful food systems FoodNutr Bull 21 361ndash366

Welch RM Graham RD (2004) Breeding for micronutrients in staplefood crops from a human nutrition perspective J Exp Bot 55353ndash364

Welch RM Allaway WH House WA Kubota J (1991) Geographicdistribution of trace element problems in Mortvedt JJ Cox FRShuman LM Welch RM (Eds) Micronutrients in Agriculture2nd ed Soil Sci Soc Am Madison WI pp 31ndash57

Welch RM Combs GF Jr Duxbury JM (1997) Toward a ldquoGreenerrdquorevolution Issues Sci Technol 14 50ndash58

White PJ Broadley MR (2005) Biofortifying crops with essential min-eral elements Trends Plant Sci 10 586ndash593

Williams CH David DJ (1976) Effects of pasture improvement withsubterranean clover and superphosphate on the availability of tracemetals to plant Aust J Soil Res 14 85ndash93

Williams PN Price AH Raab A Hossain SA Feldmann J MehargAA (2005) Variation in arsenic speciation and concentration inpaddy rice related to dietary exposure Environ Sci Technol 395531ndash5540

Woodbury PB (1992) Trace elements in municipal solid waste compostsA review of potential detrimental effects on plants soil biota andwater quality Biomass Bioenerg 3 239ndash259

World Health Organization (1992) Second report on the world nu-trition situation Global and regional results United NationsAdministrative Committee on Coordination ndash Subcommittee onNutrition Geneva Switzerland 1 pp 1ndash80

World Health Organization (1996) Trace elements in human nutrition andhealth Geneva pp 30ndash35 90ndash91

World Health Organization (1999) Malnutrition Worldwide httpwwwwhointnutmalnutrition_worldwidehtm World HealthOrganization Geneva pp 1ndash13

Yang XE Chen WR Feng Y (2007) Improving human micronutrientnutrition through biofortification in the soil-plant system China asa case study Environ Geochem Hlth 29 413ndash428

Ye X Al-Balil S Kloli A Zhang J Lucca P Beyer P Potrykus I(2000) Engineering the provitamine A (b-carotene) biosyntheticpathway into (carotenoid-free) rice endosperm Science 287 303ndash305

Yilmaz A Ekiz H Torun B et al (1997) Effects of different zinc ap-plication methods on grain yield and zinc concentrations in wheatgrown on zinc-deficient calcareous soils in Central Anatolia JPlant Nutr 20 461ndash471

Yilmaz A Ekiz H Guumlltekin I et al (1998) Effect of seed zinc content ongrain yield and zinc concentration of wheat grown in zinc-deficientsoils J Plant Nutr 21 2257ndash2264

Yodkeaw M De Datta SK (1989) Effects of organic matter and waterregime on the kinetics of iron and manganese in two high pH ricesoils Soil Sci Plant Nutr 35 323ndash335

Zuo Y Zhang F (2008) Effect of peanut mixed cropping with grami-neous species on micronutrient concentrations and iron chlorosis ofpeanut plants grown in a calcareous soil Plant Soil 306 23ndash36

Zuo Y Zhang F (2009) Iron and zinc biofortification strategies in dicotplants by intercropping with gramineous species A review AgronSustain Dev 29 63ndash71

Introduction

Improving crop yield

Crop quality and human health

Consequences of micronutrient deficiencies

Nutrient bioavailability

Correction of micronutrient deficiency

Fertilizer application

Soil amendments

Organic fertilizer sources

Plant residue

Animal manure

Organic amendments

Crop rotation

Developing micronutrient-efficient genotypes a new strategy

Definition of nutrient efficiency

Micronutrient-efficient genotypes and crop productivity

Micronutrient-efficient genotypes crop quality and human health

Total concentration of micronutrients in plant based foods

Bioavailability of micronutrients in food

Combining the benefits of high yield and better nutritional quality

Need to limit grain Cd and As while improving levels of Zn and Fe in crops

Challenges in programs for selecting or breeding micronutrient-efficient genotypes

Stress tolerance indicators for selecting micronutrient-efficient genotypes

Conclusion

References


cultivars Accordingly low levels of micronutrients have beenreported on many crops grown in different countries (Cakmaket al 1996 Fageria 2000a Galratildeo 1999 Graham et al1992 Grewal and Graham 1999 Martens and Lindsay 1990)Therefore micronutrient deficiency has become a limiting fac-tor for crop productivity in many agricultural soils In orderto obtain the genetic potential yields of crops correcting mi-cronutrients deficiencies is necessary

On the other hand agricultural practices have almost al-ways targeted higher crop yield production while minimizingcosts In addition nutrient output of farming systems has neverbeen a goal of either agriculture or of public policy Thus theincrease in crop yield in many agricultural systems as a resultof chemical fertilizer application has been accompanied withreduced micronutrients concentrations in the edible parts ofdifferent crops So that already many food systems in devel-oping countries can not provide sufficient micronutrients con-centrations to meet the demands of their people especially low-income families (ACCSCN 1992 1997 2000 Combs et al1996 Combs and Welch 1998 McIntyre et al 2001 Welchet al 1997 Welch 1998)

Recently mid 1980s the nutrition community reportedthe global significance of micronutrient malnutrition (Allen2000) In 2001 fighting micronutrient malnutrition was con-sidered an integral component of three of the eight MillenniumDevelopment Goals (MDGs) of the General Assembly of theUN to alleviate the worldrsquos greatest health and poverty issuesby 2015 (United Nations General Assembly 2000) The fo-cus of improving the micronutrient quality of crops notes thedensity of bioavailable micronutrients in crops as consumed inorder to take into account crop factors which increase or de-crease the bioavailability of crop micronutrients (see below)For example phytate in grains is well known to inhibit absorp-tion or utilization of crop Zn by humans and livestock suchthat grain phytate must be considered whenever the quality ofgrain Zn for human use is considered

Deficiencies of iron zinc vitamin A and iodine not onlycompromise the immune system but can irreversibly retarddevelopment in infancy Deficiency of any of these in a preg-nant or lactating woman can result in subclinical mental re-tardation in children Such children may be less fit to controltheir environment and to provide for their own food securityin later life to compete for better education and for higherlevel jobs within their society Vitamin A deficiency can leadto poor night vision eye lesions and in severe cases perma-nent blindness increased illness and death from infectionsIodine deficiency can cause goiter mental retardation braindamage and reproductive failure Iron deficiency can causenutritional anemia problem pregnancies stunted growth andlower resistance to infections long-term impairment in mentalfunction decreased productivity and impaired neural develop-ment Zinc deficiency can cause growth retardation delayedskeletal and sexual maturity dermatitis diarrhoea alopeciaand defects in immune function with resulting increase in sus-ceptibility to infection

Several approaches such as soil and foliar fertilization im-proved crop systems application of soil amendments and or-ganic nutrient sources are possible to correct micronutrients

deficiency and to increase their density in edible parts ofplants Considering ecological concerns sustainable agricul-ture is looking for more environmental-friendly and cost ef-fective approaches with low input of energy and chemicalsAmong different strategies applied for correcting micronutri-ent deficiency in the food chain from plant to human themost sustainable solution particularly for developing coun-tries seems to be cultivation and breeding of micronutrient-efficient genotypes in combination with proper agronomicmanagement practices

Nutrient efficiency and nutrient-efficient genotypes havebeen defined in different ways (Stewart et al 2005 Fageriaet al 2008) Definitions of nutrient efficiency generally canbe divided into those emphasizing crop productivity and thoseemphasizing the internal plant nutrient requirement (Gourleyet al 1994) With regard to yield parameters nutrient ef-ficiency has been defined as the ability to produce a highplant yield in a soil that would otherwise limit the produc-tion of a standard genotype (Marschner 1995) Other defi-nitions of nutrient efficiency also referred to as lsquoagronomicefficiencyrsquo include the amount of shoot production per unitof nutrient applied (Caradus 1990 Sauerbeck and Helal1990) Nutrient efficiency has also defined as yield responseper unit of added nutrient or of nutrient in the crop shoots(Baligar et al 1990 Blair 1993 Thung 1988) This pa-per will briefly discuss some aspects of using and developingmicronutrient-efficient crop plant genotypes as a sustainableand cost-effective method for alleviating food-chain micronu-trient deficiency malnutrition of humans

2 IMPROVING CROP YIELD

Mineral nutrients have played an important role in enhanc-ing crop production since the beginning of the green revolu-tion According to Borlaug and Dowswell (1993) nearly halfof the increase in crop yields during the 20th century was dueto chemical fertilizer application Generally improving the nu-tritional status of plants by applying fertilizers and maintainingsoil fertility has been the critical step in doubling food produc-tion both in developed and developing countries (Loneragan1997) The increase in crop production has been mainly re-sulted from the application of N-P-K fertilizers (Brady andWeil 2002) Since 1950 application of N-P-K fertilizers hasbeen rapidly increased in agricultural lands while less attentionhas been paid to micronutrients fertilization Further highercrop production per unit area depleted greater amount of mi-cronutrients from soils Now micronutrient deficiency is a lim-iting factor for attaining greater crop yields in many cultivatedsoils

Accordingly micronutrient deficiency has been reportedwidely in plant crops grown in different countries For ex-ample Fe deficiency in crops have been reported for vari-ous regions of Europe east India Bangladesh Malta TurkeyZambia and Mexico (Sillanpaa 1982) Indonesia (Katyaland Vlek 1985 Welch et al 1991) several North Centraland South American countries (Leon et al 1985) Australia

































42 Soil amendments














44 Plant residue






45 Animal manure









47 Crop rotation



























0 691 826 941 929 99660 593 754 631 855 853120 502 553 613 695 804180 306 491 435 681 585

With Zn0 805 1165 986 933 100860 771 921 775 872 896120 763 843 682 796 881180 351 544 431 718 657
































































0

1

2

3

4

5

6

7

8

9

0 20 50 80 110 140 170 200


Crop yield (tha)

Genotype 3

Genotype 1

Genotype 2























MP = (Ys + Yp)2 (3)





GMP =radic

(Ys lowast Yp) (5)



















6 CONCLUSION













REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References

































42 Soil amendments














44 Plant residue






45 Animal manure









47 Crop rotation



























0 691 826 941 929 99660 593 754 631 855 853120 502 553 613 695 804180 306 491 435 681 585

With Zn0 805 1165 986 933 100860 771 921 775 872 896120 763 843 682 796 881180 351 544 431 718 657
































































0

1

2

3

4

5

6

7

8

9

0 20 50 80 110 140 170 200


Crop yield (tha)

Genotype 3

Genotype 1

Genotype 2























MP = (Ys + Yp)2 (3)





GMP =radic

(Ys lowast Yp) (5)



















6 CONCLUSION













REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References




44 Plant residue






45 Animal manure









47 Crop rotation



























0 691 826 941 929 99660 593 754 631 855 853120 502 553 613 695 804180 306 491 435 681 585

With Zn0 805 1165 986 933 100860 771 921 775 872 896120 763 843 682 796 881180 351 544 431 718 657
































































0

1

2

3

4

5

6

7

8

9

0 20 50 80 110 140 170 200


Crop yield (tha)

Genotype 3

Genotype 1

Genotype 2























MP = (Ys + Yp)2 (3)





GMP =radic

(Ys lowast Yp) (5)



















6 CONCLUSION













REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References








47 Crop rotation



























0 691 826 941 929 99660 593 754 631 855 853120 502 553 613 695 804180 306 491 435 681 585

With Zn0 805 1165 986 933 100860 771 921 775 872 896120 763 843 682 796 881180 351 544 431 718 657
































































0

1

2

3

4

5

6

7

8

9

0 20 50 80 110 140 170 200


Crop yield (tha)

Genotype 3

Genotype 1

Genotype 2























MP = (Ys + Yp)2 (3)





GMP =radic

(Ys lowast Yp) (5)



















6 CONCLUSION













REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References


























0 691 826 941 929 99660 593 754 631 855 853120 502 553 613 695 804180 306 491 435 681 585

With Zn0 805 1165 986 933 100860 771 921 775 872 896120 763 843 682 796 881180 351 544 431 718 657
































































0

1

2

3

4

5

6

7

8

9

0 20 50 80 110 140 170 200


Crop yield (tha)

Genotype 3

Genotype 1

Genotype 2























MP = (Ys + Yp)2 (3)





GMP =radic

(Ys lowast Yp) (5)



















6 CONCLUSION













REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References





























































0

1

2

3

4

5

6

7

8

9

0 20 50 80 110 140 170 200


Crop yield (tha)

Genotype 3

Genotype 1

Genotype 2























MP = (Ys + Yp)2 (3)





GMP =radic

(Ys lowast Yp) (5)



















6 CONCLUSION













REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References













MP = (Ys + Yp)2 (3)





GMP =radic

(Ys lowast Yp) (5)



















6 CONCLUSION













REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References















6 CONCLUSION













REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References











REFERENCES





















































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References
































































































































































































































Introduction







Soil amendments


Plant residue

Animal manure

Organic amendments

Crop rotation











Conclusion

References

micronutrient-efficient genotypes for crop yield and nutritional...

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