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A review on Alternaria leaf blight of carrot
Muhammad Mubashar Zafar1*, Hina Firdous2 and Muhammad Saqib Mushtaq2
1Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Pakistan.
2Department of Plant Pathology, University of Agriculture, Faisalabad, Pakistan.
*Corresponding author’s email: [email protected]
Volume: 1 Issue: 1
Received: 2018-10-12 Accepted: 2018-11-07, Published: 2018-11-08
Abstract
Carrot is an important vegetable root having great health, medicinal and nutritional importance.
Carrot (Dacus carota) belongs to family Apiaceae, order Umbellifera. Genus Dacus consists of 25
species. Carrot is a perennial plant having a long conical edible root. It is utilized as serving of
mixed greens, steamed or bubbled in vegetables and may likewise be set up with different
vegetables to get ready soup and stew. Carrot is defenseless to numerous bug vermin and
infections. Carrot crop is influenced by bacterial, viral and parasitic illnesses yet among contagious
ailments Alternaria leaf blight (Alternaria dauci) is real constraining development consider that
causes substantial financial misfortune. Among the disease, Alternaria blight of carrot is the
devastating disease of carrot in which leaves are rapidly killed upon infection. This disease if left
unchecked spreads rapidly and may progress to form an epidemic (epiphytotic). Alternaria dauci
is the pathogen which is commonly supported by direct to warm temperature. Time of long wetness
is extremely fundamental for the germination of contagious spore on the carrot crop. The climatic
conditions for the great generation of this product are 15-20˚C temperature, relative humidity
>50% all through the development season and soil PH of 6, But the climatic conditions for the
contamination advancement because of Alternaria dauci on carrot crop are 20-25˚C temperature,
relative humidity >60% and soil pH of 6-6.5. Great loses occur when the plant is contaminated by
Alternaria dauci amid direct temperature, confronting long relative moistness period because of
dew, precipitation and sprinkler water system. As pathogen is basically presented in the plantings
through seeds so one of the best preventive measure is the utilization of treated or ailment free
48
seeds. Resistance germplasm is additionally an essential source that confines its spread. Sowing
of safe carrot cultivars is a significant way to deal with this disorder of carrot at business level.
Proper forecasting of disease along with the use of resistant varieties and post-infection treatment
of chemicals and plant extracts is favorable for the proper management of Alternaria blight of
carrot.
Key words: Alternaria leaf blight (ALB), carrot, biological control
Introduction
Carrot (Daucus carota L.) is an essential vegetable crop in Pakistan and also in the world. The
carrot has been known since long time prior in this century so it is trusted that this crop was begun
from the Afghanistan and its neighboring ranges before 900s (Gugino et al., 2004). Carrot is a
standout amongst the most vital vegetable product that gives great dietary incentive in everywhere
throughout the world (Rubatzky, 2002). The cultivated area of carrot is one million hectares on
the earth with the yearly production of 27 million tons yet in Pakistan it is grown on 13.9 thousand
hectares with the yearly production of 242.3 thousand tones (FAO, 2008). The national normal
yield of this harvest is sensibly low when contrasted with other dynamic nations, for example,
Belgium (47.64 tons ha-1), Denmark (44.29 tons ha-1) and the United Kingdom (44.28 tons ha-
1). In Africa and South America carrot production expanded gradually when however in Asia
(basically china) it expanded at extremely fast rate particularly in 1997 to declare Europe as a main
creation region (FAO, 2008).
The variety Daucus contains 25 species and is biggest class of the family umbelliferea. Its
name is taken from a French word ˝carotte˝, which originated from the Latin word ˝carota˝ that
implies a lasting plant which is broadly developed because of its long funnel shaped orange
consumable root (Northolt et al., 2004). It has a place with the Apiaceae family and has sixteenth
position when contrasted with different families. It is evaluated that it has more than 3700 species
which constitute around 434 genera (Suojala, 2000). It is utilized as serving of mixed greens,
steamed or bubbled in vegetables and may likewise be set up with different vegetables to get ready
soup and stew (Anjum and Amjad, 2002).
Carrot is a cool season crop and grown under the temperature scope of 10-25˚C in light of
the fact that it gives better production under this temperature. It is demonstrated that the ideal
temperature of day and night for plant development is 25°C and 20°C, separately (Alam et al.,
2004). The seedlings of carrot bear ice and the temperature of - 7˚C however the top development
is influenced by underneath 4˚C, and this serious condition will cause the death of plant. Carrot is
49
the piece of human eating routine. It contains carotene and a forerunner of Vitamin A (Zeb and
Mahmood, 2004). Carrot likewise has helpful impacts that lessening the eyes and blood illness
(Pant and Manandhar, 2007). The taproot of the carrot harvest is the consumable segment and
valuable for the wellness, as per the review, the examination of the eating methodologies of 1,300
develop people in Massachusetts began that individuals who had no less than one serving of squash
or carrots consistently had 60 percent diminishing in their danger of heart assaults connected to
the individuals who ate less than one serving of carotenoid rich sustenance every day. Over
adhering to a good diet conspire on the planet has constrained the general population to expend
additional crisp foods grown from the ground (Rubatsky, 1999).
Carrot crop is influenced by bacterial, viral and parasitic illnesses yet among contagious
ailments Alternaria leaf blight (Alternaria dauci) is real constraining development consider that
causes substantial financial misfortune (Koike et al., 2009). This infection happens toward the
finish of January when temperature is 24˚C (Farrar et al., 2004). Alternaria dauci is the significant
reason for this ailment which is a seed born parasite and is a genuine risk to production of carrot
yield (Rogers et al., 2011). The characteristic symptoms of this disease is the production of lesions
which are green to darker in color that at long last wind up plainly necrotic following 8-10 days of
contamination. Injuries show up on the leaflets and petioles of carrot plant as lesions with a yellow
hallo. Leaves end up plainly yellow, crumple and become dead when 40% leaf region ends up
noticeably contaminated by this pathogen. Because of these indications, rate of photosynthesis
decreased which diminishes the root measure (Pryor et al, 2002).
Great loses occur when the plant is contaminated by Alternaria dauci amid direct
temperature, confronting long relative moistness period because of dew, precipitation and sprinkler
water system. No measurements accessible for yearly production loses because of Alternaria dauci
disease in carrot crop, however in Israel serious damage to this crop have been accounted for to
cause the decrease of yields by 40-60% (Ben et al., 2001).
Sexual multiplication of this pathogen is as yet obscure along these lines, it reproduce
asexually by delivering conidia on erect conidiophores. The essential inoculum of this pathogen is
plant trash and pathogen overwinters in the plant debris. Conidia attach on the leaf surface and
sprout under favourable condition. At 24˚C with expanding hours of relative humidity from 8-56
hours damage increases (Dugdale et al., 1993). Germ tubes are delivered on conidium, which
specifically enter to the host cell divider to set up disease site and create phytotoxin Zinniol, which
degrade the cell membrane structure and chloroplast (Pryor and Strandberg, 2002). At the time of
colony formation leaf cells neighboring mycelium misfortune chlorophyll and end up noticeably
50
yellow. Following 8-10 days of disease conidia will sprout once more. By revising a similar
procedure life cycle is finished (Ben et al., 2001).
Alternaria dauci is the pathogen which is commonly supported by direct to warm
temperature. Time of long wetness is extremely fundamental for the germination of contagious
spore on the carrot crop. At the point when temperature builds the period of wetness decreases
which is required for the leaf disease. Contamination will happen in 8-12 hours of temperature
range of 16-25ºC. At the point when Alternaria dauci will encounter this temperature go, it
sporulates promptly on necrotic tissues of the carrot leaf and spore will grow in water beads and
dew (Gugino et al., 2004).
Carrot is a cool season crop. Disease because of Alternaria dauci will be built up when
there will be ideal ecological conditions for the pathogen to sporulate. The climatic conditions for
the great generation of this product are 15-20˚C temperature, relative humidity >50% all through
the development season and soil PH of 6, But the climatic conditions for the contamination
advancement because of Alternaria dauci on carrot crop are 20-25˚C temperature, relative
humidity >60% and soil pH of 6-6.5 (Joubert et al., 2000).
There are a few approaches to deal with this disease. As pathogen is basically presented in
the plantings through seeds so one of the best preventive measure is the utilization of treated or
ailment free seeds (Farrar et al., 2004). With a specific end goal to lessen the inoculum level, seed
ought to be dealt with by heated water treatment or fungicides, for example, azoxystrobin,
iprodione, fludioxonil and thiram (Strandberg, 1988). Seed treatment is not the full destruction of
applicable pathogen (Farrar et al., 2004). Crop rotation is basic for constraining the contamination
in carrot against Alternaria dauci. Pivot ought to be sufficiently long to disintegrate the plant debris
(Pryor et al., 2002).
Resistance germplasm is additionally an essential source that confines its spread (Boedo et
al., 2010). Sowing of safe carrot cultivars is a significant way to deal with this disorder of carrot
at business level. As advancement of safe cultivars through rearing is tedious process so field
screening is done to locate the safe cultivar. Despite the fact that field screening has a few obstacles
because of ecological variables however it likewise favored over different strategies because of its
simplicity (Pawelec et al., 2006). Without safe carrot cultivar, other technique to control this
infection is the utilization of appropriate fungicide. Diverse sorts of fungicides are utilized to
control this illness as indicated by infection edge level, date-book timetable and estimating
framework (Langston and Hudgins, 2002). In Pakistan, Azoxystrobin and pyraclostrobin
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demonstrated astounding outcomes in the administration of this infection (Hausbeck and Harlan,
2003).
Same pattern of cropping is bad for soil health that outcomes in the inadequacy of
fundamental minerals and supplements when contrasted with those dirts having crop rotation
(Zhou and Zhao, 2011). So adequate accessibility of supplements in the dirt is fundamental for
good product wellbeing and yield. Phosphorus is useful to plants to expand their number of
branches and leaves (Zhang et al., 2004). Also nitrogen is vital piece of protein, nucleic acid and
chlorophyll and it assumes a noteworthy part in vegetative development of plants (Viradia and
Singh, 2004). Calcium is in charge of the abiotic issue of item to expand advertise values (Chang,
2002). Inadequacy of any fundamental component in the dirt outcomes in the generation
misfortunes. Resistance of yield additionally increases by the foliar use of supplements so it
diminishes the Alternaria leaf curse infection seriousness (Kashif et al., 2005). This is likewise
useful to limit the postharvest loses and conidial germination (Yildirim et al., 2002).
REVIEW OF LITERATURE
History and Symptomology of the Disease
Alternaria leaf blight of carrot caused by a growth Alternaria dauci. It has a place with
pleosporaceae group of ascomycetes (Kuhn, 1944). It is an essential foliar disorder of vegetables
in south Asia. This sickness was accounted for in various nations and contemplated by various
researchers like United States, in Louisiana in 1890 (Ellis et al., 1972)Hatay area of Turkey in
November 2003 (Soylu et al., 2005), Germany in 1855 (Pryor and Strandberg, 2002) and in
Pakistan (Kuhn, 1944). The seriousness of this illness come to 80% contingent on ecological
conditions and treatment rate (Ben et al., 2001). Parasites having a place with sort Alternaria
comprise of extensive variety of pathogens in charge of causing tremendous yield and monetary
loss in field, natural product, vegetables and decorative harvests (Strandberg 1992, Farrar et al.,
2004).
Characteristic symptoms of this infection are greenish-dark colored sores on petioles and
appendages. In preliminary stages these sores are unpredictable fit as a fiddle and size which are
normally shaped along the edge of handout. With the progression of time these injuries move
toward becoming water soaked. More seasoned injuries end up noticeably dim dark colored and
encompassed by chlorotic corona. At temperature of 28˚C with long wetness period prompts
contamination improvement and injuries turn into various, extend and combine, giving the cursed
appearance to the leaf tissue (Strandberg, 1984). Pathogen executes the leaves by supporting
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petioles, in this manner significantly decreasing the photosynthetic action (Farrar et al., 2004).
Right off the bat, sores show up on leaves and petioles and following 8-10 days of disease it
assaults on more established leaves in light of the fact that these are more vulnerable to
contamination. At the point when 40% of the leaf winds up noticeably contaminated it ends up
plainly yellow fall and damage. Good natural condition for the disorder improvement make the
whole finish of the plant cease to exist, a marvel in which at some point mistaken for ice harm
(Schwartz et al., 2016). The injuries created by Alternaria dauci are unpredictable fit as a fiddle
having dark colored to dark shading and generally shows up on the edges and tips of the develop
leaves of the carrot plant (Farrar et al., 2004; Hooker, 1944; Strandberg, 1992).
reported that Alternaria spp. is responsible for causing damping-off of carrot seedlings but
when there is over-crowding of carrot foliage it creates a humid environment which makes the
conditions favorable for the development of pathogen thus causing serious infection to the foliage.
Soteros (1979) and Mitakkakis et al. (2001) reported that Alternaria dauci and Alternaria
radiana are threatening pathogens of carrot causing severe foliage infection to carrot plant by
attacking all the plant parts including flowers, leaves, stem and seedling.
Characterization of pathogen
Meier et al. (1922) reported that Alternaria dauci reproduces asexually with the help of conidia
and these conidia are produced in a single phase or in the form of a short chain, displaying light to
dark olive brown color with clavate, ellipsoid, obovoid or turbinate in shape. Conidia ranges
between 34-51 × 10-22µm, mycelium shows 3-8 transverse septation along with one or more
longitudinal septation which causes the division of one or all segments may not be the apical or
basal cells showing compression at the segmentation.
Groves and Skolko (1944) described that A. dauci produces smooth walled hyphae having
a size of 15-30 × 25µm and are colorless pale to dark brown in color. Origin of conidiophores is
in the form of small groups which are may be erect or flexible and sometimes geniculate,
segmented. Conidiophores are pale to olive brown in color ranging in size from 80 × 6-10µm.
Conidia are produced in the form of chains. At immature stage, conidia have smooth wall, straight
curved, obclavate having 7-11 septa which may be transverse, longitudinal or oblique. It ranges in
size from 100-450 × 16-25µm. These conidia have a hyaline, flexuous beak which is about three
times large in length as compared to the main spore body.
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Zimmer and McKean (1968) described that Alternaria dauci liberates the spores at a
maximum pace when the temperature ranges between 15-27oC along with the long wave cool
white fluorescent radiation to ultraviolet radiation photoperiod. On the electromagnetic spectrum,
the ultraviolet radiation excites the production of conidiophores. At the temperature of 24oC.
Roy (1969) determined the pathogenicity of Alternaria dauci on the carrot seedlings grown
in earthen pots as well as detached plants grown in water contained conical flasks. Infection of
Alternaria blight was observed after 3 days of inoculation. The virulence of the pathogen was at
its higher note where humidity was persisted for 72 hours and this intensity was decreased
considerably at 48 hours and 24 hours. On young carrot plants small necrotic spots are produced
along with after six days.
Ellis and Holiday (1972) described the morphology of Alternaria dauci as it produces
septate hypha which is 2-7.5µm in width, which later forms grayish or bluish black mycelia. A.
dauci reproduces asexually by conidia which are produced on the tip of conidiophores. These
conidiophores are 200µm long and 3-9µm wide, mostly unbranched, segmented and erect, flexible
showing pale to olive brown in color.
Ellis and Holliday (1972) also found that Alternaria radicina develops brownish black
color mycelial growth on potato dextrose agar (PDA) media.
Pyror et al. (1998) concluded that Alternaria radicina grows on a specific media called A.
radicina selective media (ARSA).
Pyror and Gilberton (2002) also found that fungus develop mycelium with irregular
margins showing a yellow colored stain on the culture medium and didentric crystal on the petri
dish.
Soylu et al. (2005) described that Alternaria dauci produces a velvety mycelial mat having
reddish brown color on potato dextrose agar media.
Soylu et al. (2005) also assessed the pathogenic behavior of Alternaria dauci on carrot
seedlings of six leaf stage by the spray of A. dauci using a conidial suspension at 1 × 104 spores/mL.
The inoculated plants were covered with polyethene bags placed in incubator at 26oC for 2 days
which then subsequently transferred to growth cabinet at 26oC having 16 hour photoperiod. After
10 days of incubation, symptoms of Alternaria blight were appeared on the plants.
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Mode of spread and survival
With the recent advances in agricultural technology, weather is an important factor which may
cause substantial yield losses (Harrison, 1992). Climate and weather both are important factors
which makes the plants susceptible to the attack of pathogen. Weather includes temperature,
rainfall, humidity, radiation, wind velocity, wind direction, cloud coverage and atmospheric
pressure. These factors contribute towards the development of epiphytotic (Pathak and Singh 1988,
Raposo et al., 1993, Johar et al., 1997, Sunseri and Johnson, 1999).
Luckens (1960) described that with the changes in the periods of lightness and darkness
conidiophore are developed and increased duration and intensity of light determines the number
and size of spores.
Gupta and Nikhanj (1972) at pH level of 6, light intensity favor the production and
multiplication of spores while at pH 7, temperature around 22.5oC was found best for the
germination of Alternaria spp.
Bashi and Rotem (1975) compared the increased and reduced time of leaf wetting for the
development of Alternaria blight and it was concluded that leaf wetness of 24 hours with 12 hours
of light and 12 hours of dark increased the sporulation capability of fungus. The sporulation rate
was decreased to few or none when the lightness and darkness in combination were reduced from
24 hours.
Waggoner and Parlang (1975) discovered that the temperature between 16-35oC the spore
germination of Alternaria spp. increases at a rapid pace.
Madden et al. (1978) predicted that Alternaria blight of tomato is being favored by
temperature and leaf wetness and under the prolonged favorable conditions the severity increases
up to its maximum level.
Kadian and Saharan (1984) reported that on mustard plant, minimum 4 hours of leaf
wetness are essential for the disease development. Longer leaf wetness period increased the rate
of infection on leaves.
Strandberg (1988) concluded that temperature range of 20-28oC with optimum temperature
of 24oC along with increased time period of leaf wetness favors heavily for the in-vivo
development of Alternaria blight of carrot. Furthermore, Alternaria dauci showed virulence on
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carrot plants at 4-6 leaf stage and conditions favorable for the development are 16-28oC with 100%
relative humidity and prolonged wetness on the leaf.
Pelletier and Fry (1989) concluded that infection rate of Alternaria solani increases on
potato crop with an increase in leaf wetness period from 6 to 24 hours.
The fungus is both seed and soil-borne. For the spread of primary inoculum, the diseased
seed plays a vital role in the development and spread to remote areas (Maude 1966, Netzer and
Kenneth 1969, Scott and Wenham 1973, Soteros 1979, Standberg
1983). During the wet and cold conditions seed infection was found to be more virulent as
compared to dry and warm conditions (Tylkowska 1992).
Rottem (1994) described that temperature and leaf wetness are the major contributors for
increasing the severity of Alternaria spp.
Hong and Fit (1996) that temperature of 20oC along with leaf wetness of 4-24 hours tends
to increase the disease incidence.
Rubatzky et al. (1999) reported that maximum temperature of 35oC and minimum
temperature of 14oC and optimum temperature is 27oC which greatly favors the development of
Alternaria dauci.
.Vloutoglou and Kalogerakis (1999) explained that the leaf wetness period from 4 to 6
hours after the infection of fungus is satisfactory for the development of disease on plants. With
every 24 hours increase in leaf wetness, the leaf area under infection also increased and that area
become defoliated.
Vloutoglou and Kalogerakis (2000) also found that level of inoculum, leaf wetness time
period and age of plant showed significant relationship with host susceptibility controlled
environment conditions. Pre-mature leaf defoliation showed direct response with leaf infected
area. With an increase in the concentration of inoculum the rate of leaf defoliation also increased.
Westerveld et al. (2002) explained that running water, splashed rain and infected soil are
the main reservoirs of fungal spores and through these reservoirs spread of fungal spores occurs.
During unfavorable conditions infection rate becomes slow.
Farrar et al. (2004) described the fungus as it produces conidia on conidiophores under the
temperature range from 8-28oC with 96-100% relative humidity or increased leaf wetness. Leaf
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wetness ranging from 8-56 hours along with optimum temperature of 24oC also favors the
increased severity of A. dauci.
Shrestha et al. (2005) concluded that on tomato crop, Alternaria solani infects greatly at
maximum temperature of 18-25oC, minimum temperature of 10-14oC, relative humidity of 80-
90% and leaf wetness of 14-15 hours.
Saude and Hausbeck (2006) that the environmental conditions which makes the pathogen
favorable to attack are 20oC temperature and 96% relative humidity.
Manjunath et al. (2010) tested the impact of various levels of pH, temperature, light
intensity and culture media on the growth and development of Alternaria spp. under controlled
conditions and the results of this experiment concluded that the growth of Alternaria spp. was at
its peak at the temperature of 25-30oC, pH of 6-6.5, 12 hours of lightness and 12 hours of darkness
with repetitions and potato dextrose media was the best for the growth and clear observation of
Alternaria spp.
The rate at which the pathogen spreads mainly depends upon initial inoculum level, air
temperature, leaf wetness time and susceptibility of host plant (Aguilar et al., 1986; Carisse and
Kushalappa, 1990; Gillespie and Sutton, 1979; Pryor, 2002). Petiole contamination can happen
with no sore advancement on leaves and Alternaria dauci can furthermore brings about damping-
off of seedlings, seed stalk curse and inflorescence diseases. The ailment is dynamic amid spring,
summer and harvest time editing cycles. The infection cycle starts when growth overwinters on or
in host seed and in plant debris (Koike et al., 2009).
Alternaria dauci likewise spread into field by means of degraded carrot seeds amid
development. Once presented, the pathogen can persevere in carrot plant debris or polluted seeds
in the dirt for up to two years. Temperature ranging from 20-28oC or optimum temperature of 24oC
along with prolonged leaf wetness helps to develop infection and thus infection is promoted. The
lesions increase in number which merges and enlarges to from foliar blight and it also causes
petiole girdling. Alternaria dauci can also be transmitted through infected or filthy seed (Carisse
and Kushalappa, 1990, 1992; Hooker, 1944; Langenberg et al., 1977; Strandberg, 1988).
Seedling contamination happens close to the hypocotyl-root intersection (just beneath the
dirt line) at that point in the early spring taking after overwintering of pathogen mycelium or
conidia (Rogers et al., 2011). This contaminated area will end up plainly necrotic and prompt the
generation of more abiogenetic conidia on conidiophores which fill in as secondary inoculum.
57
Wind and rain make conidia scatter to neighboring host species and various germination tubes will
be delivered from every conidium that effectively colonizes another host. As entrance happens,
Alternaria dauci creates a compound known as phytotoxin zinniol, which corrupts cell layer and
chloroplast, at last prompting the chlorotic side effects normal for the infection (Farrar et al., 2004).
The germination tube penetrates the host cell divider to start contamination that declines the
nutritive estimation of vegetables, their storability and imperviousness to decays (Coles and
Wicks, 2003). Their polyphagous nature and capacity to deliver mycotoxins and other harmful
metabolites imply that they are possibly perilous sustenance waste specialists (Solfrizzo et al.,
2005).
Histopathological studies reveal that fungal mycelium resides inside the pericarp or in testa
of the seed but does not penetrate inside embryo or endosperm (Pyror, 2002). Kim and Mathur
(2006) reported that pathogen further penetrates inside the endosperm or fused seed coat. During
the germination of seed, the spores of A. dauci infects young seedlings of carrot plant and creates
black necrotic region on the root and shoots leading to deformation of the plant and in severe cases
the death of the seedling. Infection of A. dauci on the roots occurs through damaged or non-
damaged root tissues but more infection was observed on the damaged roots of the plant (Merfield,
2009). Initial infection on the root portion of the plant creates a black ring on the petiole and root
junction which forms a dark, longitudinal spots on flower stalks and umbels. These infected
umbels unable to produce a new seed (Farrar et al., 2004).
Management
Fry (1982) described that resistant cultivar can reduce the onset of disease, symptoms development
and slow the rate of epidemic development.
Acceptance of resistance in plant against pathogen prompted the actuation of guard
qualities that were powerless under typical conditions (Kushalappa and Gunnaiah, 2013).
Utilization of safe assortments was the most proficient and savvy technique (Gugino et al., 2007).
For the determination of safe source, screening of accessible germplasm was the essential.
Roy (1969) evaluated 11 varieties of carrot against Alternaria leaf blight disease. The
varieties evaluated were early nantes, nantes, amsterdam forcing, champion scarlet horn, long
orange, early gem, danvers, fyazabad, golden heart, imperator and tender sweet. The results
concluded that all varieties showed susceptible response against Alternaria leaf blight disease.
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Simon et al. (1998) screened out three cultivars of carrot i.e. Presto, Bolero and B-5280
against Alternaria dauci. The results concluded that Presto showed highly susceptible response
while Bolero and B-5280 showed moderately resistant response against Alternaria leaf blight
disease.
Gugino et al. (2007) tested 8 varieties of carrot i.e. ithaca, fullback, kamaran, napa, nevis,
white fontana, carson and neal. The results concluded that ithaca and fullback showed moderately
susceptible response. Kamaran, napa and nevis showed susceptible response and white Fontana
was the highly susceptible variety found in the experiment as compared to all varieties.
In an exploratory field of the NYSAES Vegetable Research Farm in Geneva, NY, 19, 21,
10, 5, and 3 business cutting and dicing carrot cultivars were planted in 1999-2003, and checked
for the advancement of leaf blight indications. Plots of every cultivar comprised of four 3m long
lines. Each plant was reproduced by 5 times (1999-2002) under Randomize finish square outline
(RCBD). Each pot and line was lined by powerless cultivar "Hawk" and tainted by inoculum of
Altenaria leaf blight. From 2000-2003 just cercospora leaf blight happened in the test field.
Cultivar positioning in view of AUDPC for every time of the review, none of the cultivars assessed
was totally impervious to leaf scourge pathogen. Information in view of the AUDPC esteems
Bergen, Goliath and Oranza were decently defenseless to A. dauci. Ithaca and Fullback turned out
to be less powerless to this pathogen. Idaho, Canada, Eagle, and Indiana were profoundly
vulnerable and Kamaran, Napa, and Nevis were powerless to leaf scourge pathogens (Gugino et
al., 2007).
Alternaria leaf blight infection of carrot brought about serious loses in development and
creation of carrot harvest in everywhere throughout the world. Because of these misfortunes carrot
cultivators are confronting financial emergencies. So there is a need to control Alternaria leaf
scourge (Geeson et al., 1988).
Nega et al. (2003) recommended that for managing the disease and keeping the disease
under the check, disease free seed should be used, roguing of infected plants should be done,
burning of diseased plants, soils should be well drained and monocropping should be avoided. For
the management of seed-born inoculum, hot water treatment should be very effective in which
seed is treated with hot water at 50oC for 20-30 minutes. This treatment significantly causes fungal
spore germination loss.
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Farrar et al. (2004) recommended that for the proper management of Alternaria blight of
carrot, routine based fungicidal application is very much necessary for reducing the incidence.
Under the high inoculum pressure a single management strategy may not be suitable so multiple
fungicidal application is essential in order to reduce the disease incidence and increase the
economic yield and quality of the produce.
Germination is simply the procedure by which a spore changes itself from a lethargic
condition of low metabolic action to high metabolic exercises, since it is the procedure amid which
metabolic and physiological exercises are reestablished. Think about on various plant concentrates
to check its impact on spore germination of Alternaria dauci uncovered this is the best strategy to
control infection alongside sparing the earth. Onion, Tulsi and Strychnine tree removes at three
distinct focuses were utilized against various contagious spores. Comes about demonstrated that
at convergence of 50, 75 and 100 ppm 40%, 60% and 90% spore germination was recorded (Singh
et al., 2014).
Effective management of Alternaria diseases can be done through combined strategy of disease
free seed, sanitation, crop rotation, resistant cultivar selection and judicious application of
fungicides (Soteros, 1979).
Wells and Merwarth (1973) proved that Alternaria leaf blight can be effectively managed
with the application of chemicals. For the commercial management azoxystrobin, chlorothalonil
and iprodine are used and 80% incidence was reduced after third spray.
Hardison (1976) found that mycelia growth of Alternaria radicina on PDA was entirely
suppressed by the application of propiconazole at 30 ppm followed by Ridomil MZ (mancozeb +
metalaxyl), Daconil (chlorothalonil) and Antracol (propineb) was least effective to reduce the
mycelial growth.
Gillepsie and Sutton (1979) established a disease predictive model for the management of
Alternaria blight of carrot. Through this model timing for the application of fungicides was
predicted. During the four growing season Alternaria blight was effectively managed and
fungicidal application was reduced from 5 to 1 as compared to regular schedules. Alternaria blight
was effectively reduced by triademefon upon infection.
Mirkove (1979) checked that fungicidal seed treatment like Vitavax (carboxin) + Thiram
and Voronit at the rate of 2g per Kg seed is effective against Alternariablight of carrot.
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Bollen et al. (1983) reported that Contaf with active ingredient hexaconazole was very
effective and at 1000 1000 µg/ml concentration ceased the mycelial growth of the fungus.
Jat and Jain (1988) checked seven fungicides i.e. Difolatan 80 WP, Dithane M- 45,
Bavistin 75 WP, Blitox- 50, Topsin M and Sulfex 80 WP against Alternaria alternata in-vivo.
Topsin M (thiophenate methyl) at 0.1% concentration with four sprays at an interval
of 20 days was the most effective than Dithane M-45 at 0.3% and
Blitox- 50 at 0.3%.
Strandberg and White (1989) also reported that seed hot water treatment at 45-55°C for 4-
20 minutes reduced the Alternaria dauci population and seed germination was not affected.
Fallas et al. (1992) reported that the in-vivo management of disease can be effectively done
with the help of Blitox (0.25%) or Dithane M-45 (0.25%). Difenoconazole, an EBI fungicide at
the rate of 125 g/Ha when applied with an interval of 21 days showed excellent control of the
Alternariablight of carrot as compared to Mancozeb.
Poissonnier et al. (1995) recommended sprays of iprodione and hexaconazole for the
control of Alternariablight of carrot in France. Resende et al. (1996) reported that the efficacy of
procymidone at 500 and 750g/ha, triflumizole at the rate of 300 and 450g/Ha, thiophanate methyl
+ chlorothalonil at the rate of 500+1250g/ha, chlorothalonil at the rate of
1500g/ha, iprodione at the rate of 750g/ha, copper oxychloride + chlorothalonil at the rate of 600
+ 500g/ha and chlorothalonil + sulphur at the rate of 1125+1300 g/ha in controlling of Alternaria
dauci on carrot. Iprodione and procymidone gave the best disease control and yield.
Schwarz et al. (1998) tested the efficacy of five fungicides i.e., difenoconazole,
azoxystrobin, iprodione, chlorothalonil and macozeb against Alternaria radicina after the
first incidence in the field. Best control was obtained with 3 sprays at
12- day intervals. It is suggested that chemicals should be applied immediately after onset of
symptoms.
Mazur et al. (2005) concluded that Amistar 250SC (azoxystrobin) showed higher efficacy
in controlling Alternariablight of carrot when the disease had already established under field
conditions.
Kumar et al. (2006) worked on different fungicides belonging to different fungicidal
groups on the incidence of Alternaria brassicae which causes blight disease in radish. The results
61
concluded that chlorothalonil showed effective results and reduced the fungal mycelial growth up
to 0.2 percent.
Singh and Singh (2006) checked the efficacy of various contact and systemic fungicides
under the controlled conditions and found that hexaconazole was very effective at 250ppm reduced
the mycelial growth of Alternaria alternata. While the other fungicides like mancozeb, copper
oxychloride, copper hydroxide, chlorothalonil, azoxystrobin and propineb were effective but their
effectiveness was least as compared to hexaconazole at same concentration so at higher doses the
mycelial growth was greatly reduced to a great extent. Under the controlled conditions, mancozab
was least effective even at 250ppm
Rogers et al. (2010) evaluated three fungicides viz. azoxystrobin, chlorothalonil
and boscalid against Alternaria dauci. It was found that azoxystrobin reduced the conidial
germination ranging from 0.01 to 0.37 µg/mL, Chlorothalonil reduced the conidial germination
ranging from 0.08 to 0.09 µg/mL and bascalid reduced the conidial germination ranging from 0.09
to 0.59 µg/mL. So, from these results, A. dauci was very sensitive to chlorothalonil as compared
to azoxystrobin and bascalid.
Ben-noon et al. (2001) conducted an experiment under which the viability of nine
fungicides was resolved in two field tests. All fungicides decreased ailment seriousness, yet there
was noteworthy distinction in viability among them. The best were difenconazole and
chlorothalonil, less compelling were copper hydroxide, tebuconazole, trifloxystrobin and
mancozeb, the slightest viable were flutrifol, propineb and iprodione forthe management of
Alternaria blight under field conditions.
Ben-Noon et al. (2001) also suggested that alternating chemicals would be more suitable
than using single chemical. Recently available fungicides like azoxystrobin and difenconazole
provided better control of this disease as compared to traditional fungicides like copper
oxychloride and sulphur.
Sidlauskiene (2001) has demonstrated the efficacy of Amistar 250 SC, a strobilurin
fungicide in reducing disease prevalence (90.8%) and intensity (88.8%) of Alternaria blight of
tomato.
Prasad and Naik (2002) reported Indofil M- 45 to be most effective against
Alternariasolani causing Alternariablight on tomato.
62
Mohit et al. (1997), Dhanbir et al. (2002) recommended that in early blight of potato caused
by Alternaria solani the effectiveness of Dithane M-45 in controlling the disease has been well
demonstrated under field conditions.
Farrar et al. (2004), Saude and Hausbeck (2006) recommended that foliar application of
fungicides like difenoconazole, chlorothalonil, iprodione, azoxystrobin have been reported to be
effective against A. radicina.
Jensen et al. (2004) has investigated the role of bio agents in managing Alternaria blight
of carrot. Highly infected carrot seed with A. dauci / A. radicina when bioprimed with
Clonostachys rosea strain IK 726, reduced the incidence of the pathogen to 4.8 per cent with a
lower infection rate.
Singh and Singh (2006) reported that carbendazim and mancozeb to be most effective
against Alternaria species. Mixture of Carbendazim + mancozeb was also found to be equally
effective against the Alternaria solani.
Alkseeva (2009) conducted field trials in Russia and concluded that Score
(difenconazole) was quite effective for management of Alternaria blight of carrot on
appearance of first disease symptoms. Persistent trimming in same field brought about the lack of
basic supplements and weakness of product to disorder when contrasted with that in which harvests
were turned. Therefore there was nonstop decrease in natural product yield and plant development
(Zhou and Zhao, 2011). Utilization of fundamental supplements incited the resistance in plant,
lessened the seriousness of ALB sickness of carrot and expanded agricultural parameters of plant
(Abada et al., 2009). Utilization of borax (20 Kg/Ha) with zinc sulfate (14 Kg/Ha) created fiery
plants and high return when contrasted with untreated plants (Attanayake et al., 2015).
Conclusion
Proper forecasting of disease along with the use of resistant varieties and post-infection treatment
of chemicals and plant extracts is favorable for the proper management of Alternaria blight of
carrot.
63
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