Reuiw of: Literature

REVIEW OF LITERATURE

HISTORY AND DIS'l'NBUTION OFTHE DISEASE

Threc mcmbers of powdery mildew fungi have been recorded on teak.

They arc Unci~zula leclonne (Salmoa, 1907), Pliyllacti~rin co~ylen (Bagchee,

1952) and Pl~yllactinia guttata (Spaulding, 1961). U~~c inu ln tectonne is wide-

spread in central and souther11 parts of India, It was first discovered in India in

the state of Maharaslitra by Salmo~i (1907), in Madhya Pradesh by Agarwal el al.

(1959), in Karnataka by Rangaswamy el ai (1970), in Kerala by Sharlna el 01.

(1985) and in Andhra Pradesh by Bagyanarayana et 01. (1996).

L. 1. SYMPTOMATOLOGY

Thc pathogen infection caitses isccgl~lar white patches consisting of

mycelium and asexoal conidia developed on llic upper leaf surface. Symptoms

occur laic in Septembcr or from October and cause early defoliation (Shukla

et nl., 2001). The while patches coalesce and cover the entire surface of tlie lenf

giving grayish-white powdcry appearance (Shalma el al.. 1985) whicli later on

change to bluish grey mealy appearance finally results in black ffuctifications,

tlie oleistothecia (Shukla ct a/., 2001).

2 . 2 . ENVIRONMENTAL RE1,ATIONSHIPS IN POWDERY MI1,DEWS

Brown and Wood (1953) stated that powdcry mildews are abundant in dry

weather though they reqoirc high humidily or free moisturc for germination.

Te~iiperature relations of powdcry niildcws were rev~ewed and the

optimum ranges from about ll-28'C, for different species and averages about

22°C (Yarwood et al., 1954).

Delp (1954) sh~died the conidial ger~i~illation of grape powdery mildew

and reported the rapid germination, infection and growth took placc from 21-

30°C and the optimum temperature for gelmination was 25'C.

Powdcry mildcws are gcncrally favored by relatively dry atmospheric and

soil conditions, moderate temperatures, reduced light, fertile soil and succuletit

plant growth and thcy can bc intcrpretcd quantitatively i n terms of separate

environmental factors (Yarwood, 1957).

Nour (1958) Cound that conidia of Er~uipizr. grawinis nvefiene germinated

only at 100% R.H. and coticluded tliat germinatioo was best between 95.100%

R.H. Maximum germination of conidia offirysiphe gramifzis lrilici was occi~rrcd

at 100% R.H. (Prabhu et al., 1962).

Manners and I-Iossai (1963) reported the optimum lemperaturc for spore

germination of Prysiphe grafninis was 20°C and the optimum relative humidity

was 100% whereas for germ tube growth 25'C and 100% R.H. were optimum.

The obsel~ations of Schnathorst (1965) on powdery mildews indicated that

100% R.H. is necessary for appressorial formation on glass slides.

Conidia or Euysiplie cicho,nceor~un. E, graminis, E. tt~flrtii, Spkuerotheco

ftrligi~teo, S ri~ncuiaris and Oiriitrnr sp. on ilrrica dioicn showed optimuni

germination percentage at K.kl. ranging from 70-100 was recorded by Paul and

Kauslial(1985).

The grape powdery tnildew cotlidin were ci~pable of germinating at 25"

and at all R.H. levels ranging Gotn 0.100% (Singh and Munshi, 1990).

Saharan and Saharan (1994) obsetved that conidial germination of

Le~,eiNtiln latiuica was siaximun~ at 30°C and 60% R.H. whcrcas rnaxitnum

appressorial fonnation was rccorcled at 25°C and 70% R.H.

Germination of Sphaeuotheca fuliginea conidia on sunflower leaves was

optitnuni at 20°C and ~naxi~nulil germ tube elongation was at 20 and 25°C and

maximum gcrln Lube elongation and conidial germination were at 100% R.H.

(IIusain and Akrani, 1995).

2.3. BIOCHEMICAL STUDIES

Metnbolic alterations in the host plant takes place by the invasion of tile

pathogen into the host tissue. lnfcction to plant tissues immediately evokes a

complex array of biochemical responses in cells adjacent to the disrupted cell

layer.

Pero and Maill (1970) reported that reduction in total chlorophyll conlent

in infected leaves as compared to healthy leaves may be due to inhibition of its

proteclion by the fungus.

Vach and Bianki (1971) reported that in leaves orapplc varictics resistant

lo Podosphaern leucotrichn the level of phenol compounds was probably higher

than in susceptible varieties. Tugnnwnt (1'177) found that the chlorophyll alb

ratio was reduced by fungal infection.

Rno and Dnu (1978) found tlie decrcilse in ortlio-dihydroxy and total

phenols in the leaves of Antarnnthris infected with Albui:~) 61iti.

Biochemical changes in teak powdery mildew infected leaves were carried

out by Thite et al. (1980) and reported the infection caused considerable decrease

in moisture percentage, titrable acidity, total chloropliylls, carbohydrate contents

and poly phenol conteiit was increased.

Reduction in reducing and non-reducing sugars in blight infected

su~~flower leaves than healthy leaves may occur due to degradation metabolism

in diseased tissue (Neina, 1983).

Cliahal (1986) found decreased phenol levels in the lesions induced by

Alter~inriic ~lter17afa on tobacco leavcs.

Reduction i n the starch level due to pathogenic infection lias bee11 reported

by several workem (Allen, 1942; Summer and Somer, 1949; Govindarajulu,

1976; Thile et al., 1980).

According to Schipper and Mirocha (1968) the depletion of starch in

infected plants was due to the activation of starch hydrolyzing enzymes by fitngal

metabolites.

25

Fungal inoculation of Ailernaria sola~ri in chilli leaves caused a decrease

in the nmount of chlorophylls, reducing, non-reducing sugars, starch and an

increase in the levels of orho dihydroxy and lurel phenols wcrc observctl as

compared to hcalthy leaves by Veeramohan et ai. (19V4).

ReductLon of total chlorophyll content was observed in infected leaves of

sul~flower with Alter~rarin alternnla causes the leaf spot of sunflower (Rnjlv

ICumar and Singh, 1996).

Higher amount or clilo~ophyll, amino acids and ortlio dihydric phenols

were observed in the leaves of safflower cultivars tolerant of Plrccinin

calcitmapoe (Reeti Singh et crl., 1998).

The arnounl of total sugars and rcducing sugars were higher in leaves of

susceptible varieties of pea powdery niildew than in resistnlit varieties wl~ich

ailer infection increased in resistant vilrieties (Rathi et ai., 1998).

The surfaces of aerial plant parts provide a habitat for epiphytic

microorganisms. Phyllosphcrc thus constitlltcs a11 external surface which fonns

an environment for microorganisms. The term was first used by Last (1955), later

by Ruinen (1956).

According tu Icerling (1950) phyllosphere is restricted to the zone near the

leaves which Inter on replaced as phylloplane for the leaf surface by several

workers (Preece and Dickinson, 1971; Blakeman, 1981; Hayes, 1982).

Microorganisms reach the plant surfaces through air currents, water,

seeds, roots especially hy insects and rnitcs (Lcben, 1965), dcw dl.ops (Kuinea.

1961) and by rains (Dimenna, 1959).

Phyllosphere microflora ~nainly depend on lcaf cxudates and water which

contain Sree sugars, amino acids, pectin sr~bstances and vitamins (Tukey, 1971)

that leached from leaf surface for their nutritioa. The features of above ground

atmosphcrc forms Ulc essential medium for dispersi~l of many organisms

inhabiting the aerial surfaces (Gregory, 1973).

2 . 5 . PHYLLOSPEIERE MYCOFLORA

A wide range of literature is available regarding (he phyllosphcrc

~nycoflora of several plants (Ruscoc, 1971; Sharnia and Sinha, 1972; Sliarma and

Mukherji, 1973; Dickinson and Preccc, 1976; Riakernan and Fokkema, 1982),

where Alternaria, species of Aspergiilirs. Curvirlnuin, F~tsnriurn and

Sporobolornjres were bund lo be the most commoll and successful genern of

phylloplat~e. Clado~porium, Piloma and Epicoccum also have been reported as

phyllopiane saprophytes (Sinha and Rahadur, 1974).

IGta (1988), isolated Cladosporiu~rt cladosporioides, Aller~taria nlternato,

Cladosporiuiti sphaei.ospermrrln, Bofryris ciiievea and Sclerotinia sclerotiorvrrr

from the leaves of sunflower.

Phylloplane mycoflora of young, mature and senescent, healthy leaves of

Partheniiml 11)~sfevophorris include Alleriiaria alternata, Aspergill~is sp.,

Cfirvuloria sp., L'usarifim s p , Penicilliii sp., Rhizopirs arrhizws and

Trichodenna Iig~~oruin (Dhawan el ol., 1995).

Few reports gave the fungal colonization of botli infected and healthy

leaves in qualitative and quantitative accounts. The infected leaves of cotton by

Xanfhomonas ~~zali~acear~rrn recorded about 20 types of mycoflora which mainly

include species of Aspergillus, Rhizopus arrhizus, M~rcor sp., Alternaria teizrris,

Cephalosporiuin htrmicola, Cladosporiurn herbar~rm, Ci~ivrrlaria lunam,

Fusariurn nzor~iliforme, F. oxy.fporum, Gliocladiuin roselrni, Hel~nirilhospo~~itini

leframerrr, Nigrospora sphnericn, Penicilliuni sp., Pho~nrr exigira, Sclerotiu~n

ro@ii and non-spomlnting phycotnycetes (Wadje and Deshpande, 1979) and

lhcir study revealcd that incrcase in infection alwnys gavc increase in number of

fungi.

Sharrna et al. (1985) reported Aspergillusflavipes, A. fumigalus, A. niger,

A. sydowii, Peniciilitiin citrinum, P, oxalicrim, Cladosporiurn cladosporioicles

and Curvularia lunata were more in number and occurred frequently on powdery

mildew infected leavcs than healthy leaves of Bhindi.

28

Rust infected leaves of triticale illvariably supported higher popi~latiun of

rungi than non-infected leaves. Those fungi includc A l ~ e i ~ i ~ o r i ~ i nlter~riaia, A.

liurrricola, Aspe~gil1~1.i luchi~erisii, Aureoba.ridii~nr p~rllulnns, Cr~ndillir olbictrns,

Clociosporium clodosporioides, C, kerbonlrr7, Ci~r~vrrlario Irisrrto, Epicocaisr

purpuresceirs, Fusatium o.rysponrrn, Pri7iciiliun1 expnris~~ttr and Trichotheciurtt

roseurn (Ciarg and Sharma, 1983).

Pliyllasphere s t~~dies of (Garg and Sharma, 1985) both healthy and white

blister infectcd mustard leaves revealed the existence of 34 species of fungi on

hcalthy leaves and 48 species on infectcd leavcs indicating that infected leaves

supported distinct rungal flora than heal thy leaves.

Sharma el al. (1985) found that the mycoflora of powdery mildew

infected leaves of bhindi was higher than that of healthy leaves both qualitatively

and quantitatively,

Microbes on phylloplane interact aiid affect the gerlnination and growth

~i~utually. Both stirnulatory and inhibitory i~~teractions have been reported (Singh

and Sinha, 1962; Leben, 1964; Sinlia, 1965; Kapooria and Sinha, 1969: Preece

and Dickinson, 1971; Shar~na and Sinha, 1972; Wadje and Deslipande, 1979).

Development of leaf pathogens is affected by plant saprophytes,

colonizing the phylloplane. Earlicr rcports (Rainberg, 1931; Newhook, 1957;

Flcntje, 1959; Sinha, 1965) proved h a t the propngules of a range of co~nlnonly

occurring saprophytes may influencc the germination nnd infectivity of

pathogens if both are present in the same infection dmp.

The relationship of epiphytic microorganisms to plant disease has been

previously discussed by Leben (1965). The activity of bolh saprophytes and

pathogens on leaves is dependent on the microcli~natological conditions at the

plant surface as well as on the chemical envilunment (Blakeman, 1973).

The ~nicroorganisms found nn tlie surfacc of leafplay nn important rolc in

nn associative or antagonistic manner on tlie ger~iiination of spores of pathogenic

fungi (Brooks and Moorc, 1926; Mains, 1934; Kapooria, 1964).

Sinha (1965) stated that some of the surface niicroorganisms may cause

(he production of pl~ytoalexi~ls in the host and bring about changes in the reaction

of the host to parasites. A few surface niicroorganisms may be hyperparnsites

and also themselves produce sclf-inhibitory and sclf-stimnlatory substances to

bring out a grcat influence on their own gel-mination.

Thc antibiotic like inliibitory substances produced by tlie leaf surface

mycoorgnnisms of Cicer arietinurn has fungistatic potentiality against

uredospores of Urornyces ciceris-arielif~i (Sinha and Bahadur, 1974).

Excretions on thc surfacc of leaves contnin slimulatory substnlices and

rcgulate the colonization of leaf surface organisms (Fating and Khare, 1978).

Leaf infected with pathogen modifies the silrfacc flora which partially or

completely protect the leaf against subsequent il~fection by other pathogens

(Sharnla et al., 1985).

Leaf roll affected grapevines were rzsistant to powdery mildew infection

(Gohen and Schnathrose, 1961). Tobacco infected leaves with chilli mosaic vi~us

showed resistance against developrncnt of powdery mildew symptoms (Chadha

and Raychaudhi~ry, 1968). Excretions from virus infected lenves of bhindi

inhibited the germination of Evysiphe cickorucearui~i and other surface flora

(Sharnw et nl.. 1985).

Bopaiah el (11. (1991) repoled that the pathogens, Hrlinisihosl~oriuw

oiyzue, Pl~yfophfi~ora arecne and Pyriculnrin o y a e were inhibited hy all the

saprophyLes, during their sh~dy or leaf surface saprophytes and pathogen

interaction.

%. 6. BIOLOGICAL CONTROL

The tcrm biological control was used in relation to plant pathogens by

C.F. Von Tuveuf in 1914, and to insects by H.S. Stnit11 in 1919, with the broad

simplistic interpretation of co~itrol of onc organism by another, exclusive of man

(Baker, 1987). Biological control, as defined by Garrett (1965), involves

reduction in disease through ihc agency of one or more living organisms other

than the host or man.

The word antagonism in microbiology was introduced by Robert.? (1874)

as quoted by Raker (1987).

Raker and Cook (1974) believed a~itagonists should be souglit in areas

where the disease caused by a given pathogen does not occur, has declined, or

cannot develop, despite the presence of a susceptible host, ralhel. than wllerc the

disease occurs.

Weindling (1932) discovered that Trichodei.~rra Iigr~ovi~rn would pnrasitize

a number oC soil borne fungi in culture and suggested controlling certaln

pathogenic fungi by augmenting soil with an abundance of these mycoparasite.

'Thus, the idea of biological control of plant pathogens by mycoparasitism was

born (Adams, 1990).

Hyperparusitism

The ternis hyperpal.atism, mycopal.asitism, direct parasitism, and

interfungus parasitism are used with reference to the phenomenon of one fungus

parasitising on another. The pathogen of this type of pi~rasitism is known as the

hypcrparasite, mycoparasitc, or simply as thc parasilc (Boosalis, 1964).

Barnett and Binder (1973) separated mycoparasites into two groups based

on thcir mode of parasitism namcly necrotrophic mycoparasites which kill the

mycohost by excreting toxic substances when they come in contact and later

utilize the nutrients that are released and biotrophic mycoparasites that often

obligate, obtained the nutrients from the living cells of the mycohosi with or

without causing hnrm to the mycohost (Barnett and Binder, 1973).

Many fungi havc been recorded growing on othcr fi~ngi in nature. These

f h g i considered as fungicolous (Sundheirn ant1 Tronsmo, 1988).

In many antagonist~c rclatiunships between ~uicroorgnnisms, the actual

~nechanism is either due to parasitism, competition and antibiosis (Blakeman and

Brodie, 1976; Pokkema, 1976 ant1 Skidmorc, 1976).

Drechsler (1938) reported a hyphnmycete wbich vigorously parasilizctl

oosporcs of pythiaccous root rolling fungi. Internal parasitism is see11 ill

Koze/lncladoclzylriumn Karling has a host range oi' Lhree species of

No~vakowskiella and Cladoclzytriunz (lcarling, 1942).

Barnett and Lilly (1958) have dcscribcd io dctail relatively the comlnon

type of parasites. Most of the known contact parasites are imperfect fungi and

their hosts are either ascolnycetes or imperfect fungi.

Parasitism involves penetration of fungal tissues and production of

metabolic substances which result in destruction, by lysis, of spurcs, sori or

hyphae and displacement of tissues of the pathogen by the hyperparasite either

within pustules or by the for~nation of crusls of mycclium which overlay fiuiting

structures (Barnett, 1963).

A less specialized hyperparasitic relationship is shown by Trichoderrna

sps. which wstrict development of othcr fungi including pilthogens, by hyphal

interactions involving coiling m d pcnetration (Dennis and Webster, 1971a).

Alterrraria and Cladosporiurn species were llype~parasitic, penetrating and

causing lysis of the uredinosporcs of Melairrpsora lnrici-populiila (Omar and

Heather, 1979).

Sharnia and Heather (1981) rcported parasitism and lysis of orcdospores

of Melanzpsora iarici popuiirla by two C~l~~rlusporiiini spccies, C. herbor~rm and

C, tenirissirnuin.

C. Competition

0118 of the most ilnpoliant factors that affects cornpetilion or

niycoparasitism is nutrition (Barnett and Lilly, 1962: Boosnlis, 1964). Soil

amendment with dried ground soyabean stenis and leaves enhanced the incidence

of parasitism of Rhizoctonia solmii Icuhn, by Trichoderina sp. and Perzicilii~rm

vermiculalurn Dang (Boosnlis, 1956).

Exogenous nulricnts may stimulate germinalion, mycclial growth or

appressorium formation on the surface of leaves as well as stimulating aggressive

lesion development in necrotrophic pathogens such as Botrytis ciri~iea (Clark

and Lorbccr, 1977).

Erwinia herbicolu ficqucntly associated with the fire blight pathogen

E.anzylovoru, on aerial plants fruit trees reduces amounts of nutrients thus

restricting growth of E, amylovora (Riggle and Klos, 1972). Inhibition of

Xanthomonos oryzoe on rice shoots by E. hcrbicola due to similar causes (Hsieh

and Buddenhagen, 1974).

In a fcw instances where antibiotic production (Forrer, 1977) has been

identified as the main cause of anlagonism by a saprophytc, a ccll-ficc cultural

filtrate or semipurified antibiotic preparation inay be used for bioco~itrol

purposes. A numbcr of phylloplane genera including representatives of

filamentous fungi, yeast and bacteria havc bccn rcporled to produce antibiotics bi

vitru (Blalceman and Fokkema, 1982).

Species of Alterntrrin, Dotryfis, Aui.eobasirliuaz and Trichodernla have

been reported to produce antibiotics. Thc majority of strains of Airernaria have

been reported to product antibiotics active against gram pasitivc bacteria wd

fungi (Lindenl'clser and Ciegler, 1969).

Trichodertna spp. produce both lion-volatile and volat~le antibiotics.

"Trichodcrmin" antibiotic is aciivc against fungi and other peptide antibiotics nre

active against fungi and bacteria (Dennis and Webster, 1971b).

Trichoderw~a species, T, hamnhrrn and T pseudoitoningii inhibited

Phyfophllzora sp, apparently by direct antagonism wit11 niinor inhibition by

al~tibiosis (Chambers and Scott, 1995).

e.7. HYPERPARASITES ON POWDERY MILDEWS

Large number of hypc~parasitcs on powdery mildews was described on

members of Erysiphaceae family (I-Iiraisuka et al., 1979).

The possible use of hypeiparasitcs in biological control has been

discussed in detail by Krnnz (1981).

Hypcrparasites attack hyphae and sporulating structures of plant

pathogens in the field, reducing infectiorl and pathogen inoculum (Blakcman and

Fokkema, 1982).

The most common hyperparasite on powdery mildews is the coelomycete

/ln~pelornyces qrrisqunlis first described in the middlc of ninctcclith ccntury. For

many years some ~iiycologists considered the hyperpawsites pycnidia for

accessory sporc stages oC the powdery mildew hosts (Sundheim and Tronsmo,

1988).

The most important specics of hypcrparasitic fungi are Amnpelo~~zyces

quisqnalis, Tilleliopsis spp. and Clnrluuporii~rn spp. on powdery mildews

(Sundheim and Tronsmo, 1988).

Yalwood (1932) used conid~al suspension of A. q~risq~rnlis in cxpclimcnts

with the biological control of red clover powdery mildew and reported that

conidial prodllctioli in the powdery mildew liost ceased within one week after

npplicntioli of the hyperpnrns~tes.

Apple powdery mildew Podu~pknera lerrcolriclzrr was controlled by

application of conidial suspensions of the hyperparasite A, quisqualis (Odintsova,

1975). Jarvis and Slingsby (1977) ohtnined conh.01 of the cucumber powdery

mildew S. fuliginea with the conidial suspensions of liyperparnsitc A, qrrisqunlis.

Sztejnbesg (1979) repo~ted on the control of S.fuligir~ea on cucumher and water

melon by A, quisqualis.

Ar~lpelowlyces yuisqualis inhibited mycelial growth, sporulation and

conidinl germination of powdery mildew of cucumber caused by Spkaerothcca

fuligi~lca (Beuther et al., 1981).

Sundheim and Krel<lilig (1982) investigated ihe infeclion process of A.

quisqunlis on (he ci~cumber powdery niildew Sl~haeroti~ecafirligi?~ea (R..) Poll.

by using a scanning electron microscope.

Thc powdcry mildew infecled leaves of Dnlbexia sissoo showing

hyperpnrnsitization of A. quisqualis on Pl~yyiloctinin rlillbergirie (Rajasab and

Vidyasagar, 1993). Falk et al. (1995) reported the mycopnrasitism of A.

qrtisqualis on the cleistothecia of Uncinula necator on grape leaves.

IIoch and Provvidenti (1979) found strong antagonism between a

Tilletiopsis sp. and the cucutnbcr powdcry mildcw S/ipl~ilerotiieca fnligiizen.

Tilietiopsis spp. are common phylloplnne yeasts belonging to the family

Sporobolornycetaceae was a hyperparasite on powdery mildews (Sundheim and

Tmnsmo, 1988).

Cladosporiun~ sps. have been reported Lo parasitire sevcral powdery

mildews. Mathur and Mukerji (1981) controlled by sprnyiiig a spore suspension

of Cladosporium spongiosum onto lenves of Morus alba infected with

Phyllactinia guttata, They also reported parasitization and inhibition of conidial

germinnti011 of Phyllactinia dalbergiae on Dalbergin sissoo.

Bagyanardyana and Nirnnjan Rao (1981) repo~ted Alternaria aiterzraia

and Clndosporiurri spongiosutn as hyperparasitcs on Acvosporivrrz deridrophtboae

causes powdery mildew on Dewdropk~iioiir,fiilcaie and niycopalasitisni results in

plasrnolysis in the complete collapse and disin~c~ration of l~owdeiy mildew

fungus. Shama Rao and Sullia (1981) reported Cladospori~mt sp, as a

hyperparasite of phyiinctiniil corylea which causes the powdery mildew of

mulberry, infects the conidiophores and conidia of pathogen.

2.8. USE OF CULTURE FILTRATES ON PLANT YA'I'HOGENS

Brown and Boyle (1944) who observed that a crude ciiltiire filtrate of

Pe~iicilliun notntum was effective against crown gall, caused by Agrabiicleriiirrz

tumefaciens. Culture filtrates of Trichodernza roseum inhibited [lie germination

of uredospores of Pziccinia gratniriis tritici was reported by Srcekantaiah and

Joshi (1958). The culture filtrate of Trichoderma roseirin inhibited the sporc

germination of rusts fungi include species of Pirccinin and Uror~tyces (Ahamad,

1970).

Culture filtrates of Bncillli$ subtilis contain a ther~nostable con~poutid that

protects peaches from infection by Mo,iilinia fiuoticola (Pusey wd Wilson,

1984). Autoclaved cultun filtrates of Bacillus stibli1i.r suppressed i~ifectioli af

soyabean stems by Pl~omopsis sp. in the field (Cubeta et al.. 1985). Chaumsia

and Dayal(1985) found the inhibition of Peronospora arboresce~zs by the culture

metabolites of Nadosporium chlorocephflluiiz.

Cell-Lree culture liltrates from Ti.ichoderrria,fii~us killed riiicrosrleroiia of

Verticilliuiiz duhliae in slcrilc soils (Fravel et al., 1987). In 1908, M.C. Potter

first reported inhibition of plant pathogens by their own metabolites. Erwiniu

carotovora growing on tuiliip tissuc and Penicillibr~ri i l i~ i ic~i~n in orangc rind,

were killed by liquid media in which each pothogen had grow11 (Bnker, 1987).

Cell-free culture filtrates or extracts of these filtrates liave been used in

biocontrol (Fravel, 1988). Perzicilliurri islandicurrr culture filtrate inhibited the

growth 01" palhogenic fungi, Hel~ninthuspuriurn or:],zne, Piij~tophfhorn irrecne and

Pyricularia oryzae (Bopninh et al.. 1991). Culture filtrates of Trichoderiu

hairlaturn, T. pseudokoningii and Gliocladirrn~ virens inhibited the growth of

Phytophrhom cirznamor~~i and Phytophthora citric010 (Chambers and Scott,

1995).

Maximum inhibition of growth of Alto?rariir solani was recor<led with the

rnetabolitcs of Aspergillus jlnvus and A.~pergill~rr terpeus during in virro

screening of non-volatile nietabolites of phyllosphere mycoflora of brinjal

agninst leaf spot fungus (Singh and Singh, 1999).

Due to this significant control of plant pathogens by fungal cultlire

filtrates, in recent times, several inicrobial products linve been developed

commercially as bioconlrol agcnts to control plnnt diseases. There are number of

fungal products in the markct used to control plant diseases and nearly 40 have

been reported (Cook et aL, 1996; Whipps, 1997; Fravel eta/ . , 1998).

AQ-10, a commercial fungal product developed specifically from

Anlpeloniyces q~risqitoiis for controllt~ig powclcly mildews on strawbeny, tomato

and grape (Dick rf al., 1998).

%. 9. DlSEASIC MANAGEMENI'ltY CIIEMICALS, FUNGICIDES AND PLANT EXTRACTS

Powdcry mildew fungi can be controlled by protective eradicant and

therapeutic applications. Ynrwood (1957) statcd powdery mildews were well

controlled by spraying sulfur dust and reported use of cliemicals also preferable.

Chemicals like copper sulfate (Radclyffe, 1861; Ynlwood, 1945)

Burgundy mixture (Horne, 1918), Sodii~m biocarbotiate (Curry, 1924), Sulfuric

acid (Guba, l928), Sodium chloridc (Jorstad, 1925), Bordeaux mixture (Braun,

1948; Yarwood, 1951), Mn~izate (l'liomas and Holtzmano, 1951) have becn toxic

to powdery mildews or even effective in disease co~~trol in limited trials.

Sahni (1973) recorded fair control of Altertiaria allernata by Benlate,

Difolatan, Kitazili and Demosan on leaf blight of roses and stated Demosa~i

inhibiled spore germination complctcly at 1500 pptn

Kulkarni and Siddaramninh (1979) reported that teak powdery mildew

was most effectively controlled by sulphur dust followed by Baycor, Morestan

and Calixin.

Bavistin and Cercobin M, fungicides were effective against the

gemn~ination of teliospores, sporidia and the n~ycelial growth of Neovossia indica

(Ashok Gishna and Singh, 1983).

Effect of Calixin and Korathanc on dcvclopment of mildew epidelilics on

pen was studied by Mishrn and Asliok Icrishna (1990) and reported reduction in

coliidial germination ofpathogen.

0.2% Dilhi~ne M-45 colitrolled Altentor.in blight of bottlegourd upto 70%

(Bhargilva and Singh, 1992). Soluble silicon sprays reduced scvcrity of powdcry

mildew (U17cirtuio necnlor) on grape leaves (Bowen ern/.. 1'1'12). Grape powdery

mildcw wns reduced significantly when sterol demethylation inhibiting

fungicides are mixed with copric hydroxide (Anderson and Wicks, 1903).

Gadoury et nl. (1994) observcd reduction of powder mildew and other

discascs by the application of limc sulfur on dormant grape vines. Foliar

application of phospliates effectively controlled powdcry mildcw fungus on

field-grown wine grapes (Reuveni and Reuveni, 1995).

Sodium hydrogen carbonate cont~~olled powdery mildew on grape vine as

repolfed by Reh and Schloesser (1995). Application of potassium silicate for the

control of grape powdery mildew proved as an alternative spray material to

sulfur for powdety mildew control (Reynolds el nl., 1996).

Copper sulphate and zinc sulphate were more effective in reducing the

lesio~i numbers and lesion size at 1000 ppm in leaf spot of chillies caused by

Xastltomonas nxonopodis pv. vesicntoria (Swapna Sree, 2002).

Powdery mildew of sesamurn caused by Oidilmm acawthospcrmi was

colitrolled maximnm by karathane and found to be effective next to sulphur dust

(Karunanithi, 1996).

Fungicides chlorothalonil, thiram and mncoreb inhibited compleiely sporc

germination of Aiteriznria alternata of brinjal lcnr spot at 1000 pprn

concentration (Pandey et ul.. 2000).

Hexaconazole and Tebuconazole were most effcctivc to keep the disease

powdery mildew of pea utidc~ check (Abraham Mathew et at., 2003).

Ylalit Extracts

The applicatio~i of cxtracts of highcr plants and their preparations fur

controlling plant diseases has been in use since 1470 B.C. (Sharville, 1960).

Extracts of many plants and their conlponents are known to be useful i ~ i

controlling plant pathogens (Spencer el al., 1957; Sheklinwat and Pwsad, 1971;

Egawa et al.. 1971; Appleton and Tansey, 1975; Misra and Dixit, 1977; Dixit

el al., 1983).

The leal' extracts oC Cin~ia~nonu~n canrphora and Cathornnrlius roseus

completely checked the ratlid growth of Cuwularia lunnin (Rhowmick and

Vardhan, 1981). Considerable reduction in the growth of Apergil!usJ7ai~us with

the extracts of C~rrcnma rhizomes and Clenatis lcaves was found by Reddy

(1987).

Dubey and Kishore (1988) found that essential oils from leavcs of

Melnnleuca leucadendron, Ocirnurn cariztrn and Citrus rnedica between 500-2000

pprn were able to protect several stored commodities from biodeterioration by

Aspergillusflavus and A, versicolor.

G h e ~ w d e (1989) has observed that aqueous leaf extracts of Azndirachtn

indioo eCCectively controlled the leaf rust caused by Pirccirlin ai.aciiidis on

groundnut.

Singh el al. (1991) concluded that frcsi~ ginger extract can be used to

control powdery mildew of pea effectively under field conditions.

Antifimgal activity of leaf extract oC Azadirnchta irldica was morc

effective to inhibit spore ge~~nination of Ceroteliir~ri jici whereas extracts of

Eucalyptus sp. and Calotropis gigarrfea highly toxic to Cercosporn 111orico1a

causes leaf rust and leaf spot diseases in mulberry respectively (Sarvamangaln el

a/., 1993).

Biswas et a/. (1995) reported that the extracts of Zirrgiber oflcinale and

Azadirachta indicn were effective against powdery mildew of pea. Haillbawale el

a/. (1995) found that extracts of Da2ur.a metal, D. slrnn~oniu~r~ and Solanrlrn

nigrum delayed the spore germination of Alternaria macrosporn causing leaf

spot in cotton.

Extracts of Aliium cepa, A, sativrrm, Zingiber 08cinnle and Azndirachtn

indicn were found to be non-phytotoxic and fungicidal in nature and have great

potential in controlling tl~epowdery mildew orpea (Sindhan e l a l , 1999).

Aqueous wccd extracts of Diplaziurn esculer~ircni, Ageratrim

houstonianzim, Cnssin tora, Solanum nigrurn and Polygonurn plebeiunr were

found to significantly inhibit the ~nycelial growth of Rhizoclo111(i solani which

causes sheath blight of rice (Ralljana S m l a ef nl., 1999).

The lenf extracts of Solnnlrnz torvzan, Datlrva rnefnl arid Prosol~is juiiflora

wcrc found to effectively inhibit the conidial germination and mycelial growth of

Cnllerorricilu~n cnpsici nnd Gloeo,~poriurn pipemlunr infecting chillies (Gumathi

and Kannabiran, 2000).

Bansal and Gupta (2000) proved that the leaf extmct of Aznrlir.achm

indica was higllly toxic with co~nplete inhibition or mycelial growth and spore

gertninntion of ITlrsaritr~n oxysporuill causing wilt of fenugreek.

Javed and Charaya (200.3) found that the growtb of Colletotrichirsr cap.~ici

was completely inhibited by the leaf exkact of Azadii.acirta indica. They also

proved that the leaf extracts of Ocinruin sanctunr and Oci~nir~n basilictrrn were

quite cffcctive against thc pathogcn causing fruit rot of chillies.

SCOPE O F T H E PRESENT INVESTIGATION

The present study comprises investigations on various aspects of U~~cinrila

tectonae, the causal agcnt of powdery mildew disease of teak. The earlier reports

ol' this fungus are from central and southern states of India like Mahamsl~trn,

Madhya Pradesh, Kerala, Karnataka and Andhm Pradesh where teak is the most

important timber yielding plantation tree species. In view of its economic value

the present invcsligation was undertaken.

An overall survey and consideration of thc review of literature revealed,

very limited studies on powdery nlildew disease of teak. Shldies were camed out

on the nio~phology of the pathogen and biocheniical changes of host-pathogen

interaction and very little was contributed lowards co~itrol measures in previous

dccades. Kecping tliis limited work io view the present investigation was

undertaken to carry out the studies on control measures of teak powdery mildew

disease.

The main objective of the present study was to investigate the biological

control o r the pathogcn aucl to suggest an improvcd means of disease

mnnagement. The screening of niycoparasites and their nutritional requirements

were also carried out.

Incidence of powdery mildew discase was sh~died in four locations of

Chittoor district namely Rangampet, Chandragiri, Tirupati and Palamaner.

Studies on effects of environmental factors on conidial gerniination were carried

out.

Various biochemical studies on changes in chlorophyll, carbohydrates.

proteins, phenols and peroxidases were carried out in powdcry mildcw affected

leaves to understand the possible n~echanisms involved in the development or

disease. An efSorl was made to detect possible control measures by using few

chemicals, fungicides and usc of plant extracts.

I t is hoped that this study will rcsult in a bctter understanding the host-

pathogen interaction and help in evolving contl.ol measures against powdery

mildew of teak.