STUDIES ON POWDERY MILDEWS OF SOME ECONOMICALLY IMPORTANT PLANTS

DISSERTATION SUBMITTED FOR THE DEGREE OF

M^ittt of ^dilos^opljp IN

BOTANY

BY

ASHRAF HAMBBD KHAN

D E P A R T M E N T O F B O T A N Y A L I G A R H M U S L I M U N I V E R S I T Y

A L I G A R H ( INDIA)

1991

:^-!V'"r**t"^

DS1816

Dr. MOIID. AKRAM M S c , Ph .D , (Ah( i ) F. P. S. I.; r. n .

Reader

Principal Investigator UGC. (Mildew) Project

jRcf. No.

Mycolop;y and Plant Patholo^Y Ldbonilorlcs

DEPARTMENT OF BOTANY ALIGARH MUSLIM UNIVERSIT :

ALlGARH-202001 (INDIA.

Dated

CERTIFICATE

This i s t o c e r t i f y t h a t MR. ASKRAF HAICED KHAT'I has wcrKeci

i n t h i s depar tment as a Research Schola r under my super­

v i s i o n and gu idance . His work on the "STUDIES ON PCDn^R.'

MIUJEV/S OF SOME ECONOMICALLY I M P O R T M T PLAI^ITS" i s up*o

d a t e and o r i g i n a l . He i s al lowed to submit h i s d i s s e r t a ­

t i o n for the c o n s i d e r a t i o n of the award of the degree of

Master of Phi losophy i n Botany.

( Dr. MOHD. AKRAI-1

^ ® miT iP^ia^Em'Wi

ACKNDWLEDCEMENTS

I t i s merely not out of t r ad i t i on tha t one acknowledges

the co-operation of multitude of people in the accomplishment

of a work but i t i s solely due to the earnest r ea l i za t ion of

the fact t ha t without them, the very existence of i t would not

have been poss ib le . No amount of thanks^will be enough to

express my feelings for my supervisor Dr. Mohd. Akram, Reader,

Department of Botany without whose consis tent guidence, c r i t i c a l

counselling and encouragement, th i s work would not have seen

the l i g h t of the day.

Thanks are a lso due to my ideal teacher Prof, A.K.M.CJiouse,

Chairman, Department of Botany who not only provided me laboratory

and l i b r a ry f a c i l i t i e s to undertake t h i s venture but has always

been a continuous source of insp i ra t ion for me,

I offer my gra t i tude to Dr, M,WaJid Khan, Reader, whose

moral and material support was always avai lable to me whenever

I needed i t most,

I take th i s opportunity to acknowledge the co-operation

rendered by my senior colleagues M/S M , S , Perwez (Lab, col league) ,

M,J, Pasha, M. Imran Khan, Mohd. Abul-Fazal, Naimuddin,

M,B, Siddiqui and Samiullah Khan and also by my friends M/s

Saiyed Iqbal Husain (Lab. colleague), Munawar, Imran, Naseer,

Kamal, Farooq, Nafees and Rasheed for the i r wholehearted support

and encouragement.

[ii]

At the end I would like to place on record my gratefulness

to my family members especially to M/S B.Z. Khan and R.H. Khan

whose brotherly affection and encouragement has gone a long way

in completion of this project.

ASHRAF HAMEED KHAN

C O N T E N T S

1 . INTRODUCTION 1 - 1 3

2 . REVIEW OF LITERATURE 14 - 43

2.1 Brassicaceae 15

2.2 Cucurbitaceae 20

2.3 Papilionaceae 27

2,A Environment and powdery mildews 34

2.5 Powdery mildew fungicides 39

2.5.1 Siaphur 40

2.5.2 Dinitrophenols 41

2.5.3 Quinomethionate 42

2.5.4 2-Amino pyrimidines 42

2.5.5 Triforine 43

3 . PLAN OF WORK 44

4 . MAIERIALS AND METHODS 4 5 - 5 7

4.1 Survey 45

4.2 Identity and maintenance of pathogen 45

4.3 Host range and varietal resistance 47

4.4 Observations 48

4.5 Effect of temperature and relative humidity

on incubation period 50

4.5.1 Effect of temperature 50

4.5.2 Effect of relative humidity 50

4.6 Chemical control 52

4.6.1 Estimation of sugar 53 4.6.2 Estimation of nitrogen 54

4.7 Phylloplane fungi and powdery mildew 56

5 . REFERENCES 58 - 8f

CHAPTER 1

INTRODUCTION

The family Bryslphaceae contain many serious plant

pathogens known as 'Powdery Mildews*. Their common name is

derived £rom the mealy appearance of conidia on infected foliage.

Powdery mildews recognised ast biotrophic parasitic fungi of

Angiosperas having siqperficial mycelium within the epideroal

cells of -the host; their abundant growth during the period of

comparatively low temperature and high hximidity; germination of

conidia without external water sv5)ply due to their high water

content and production of dark superficial perithecia,

Taxonofflically» the Bryslphaceae beloDg to the order

Srysiphales which is often included in the sub-ria>s piectomyci-

tidae of AscomjTcetes because of having ascocarp without ostiole.

Srysiphales consists of a single family Srysiphaceae. i^proximatly

•00 species of powdery mildews constitute 20 genera to form the

family Erysiphaceae. On the basis of degree of ectoparasitism

Srysiphaceae is divided into two sub-families Brysipheae and

Phyllactinfiae by Salmon (1900) and into three subfamilies

Brysipheae, Phyllactineae and Leveilluleae by Homma (1937).

With few exceptions, members of the Erysiphaceae have an

entirely superficial mycelium (Ectophytic mjrcelium) which consists

of a network of colourless hyphae abundantly present on the

epidermis of the infected parts of the host and securely anchored

to it by numerous haustoria. Haustoria penetrate into the

epidermal cells of host plant to obtain nourishment from their

protoplast. Several types of haustoria are produce by different

members of the family. In Levelllula the hyphae penetrate into

leaf through the stomata and spread between the mesophyll cells

(Endophytic mycelium) • Tufhile in case of Phyllactinia and

Pleochaeta the epiphytic mycelium produces both conidiophores

and special branches which penetrate the stomata and grow into

the interior of the plant (Hemiendophytic mycelium).

Erysiphaceae reproduce asexually by means of single celled

hyaline conidia borne on conidiophores. Conidia differ in shape

and size from species to species but,in general, may be described

as ovoid or cylindrical with rounded edges. Conidia of powdery

mildews do not require fz*ee water for germination. The conidia

are short lived summer spores. In contrast to those of most fur gi,.

the conidia of some powdery mildews are able to germinate at very

low humidity levels. On approaching the favourable conditions

each conidium germinates by germ tube which tiltimatfily gives rise

to new mycelium.

The sexual reproduction occurs at the end of summer, when

conidial production slows down and eventually ceases. The white

powdery appearance of the host surface now changes to greyish

or borwn shade and hypha prepare to form ascocarps which are

perithecia. Sexual reproduction involves the production of

recognizable ascogonium and antheridium as a result of reproduc­

tion asci and ascospoi*e3 are developed within the perithecium.

Ilie perithecium is a small more or less spherical structure

bearing appendages wbich are commonly siniple curled or branched

at the tip in a manner characteristic of each genus* The

function of these appendages is rather dubious, but their struc­

ture furnishes a useful taxonomic character.

The powdery mildews disease appears first on the leaves

as white or greyish felt like patches. The patches may enlarge

rapidly and cover the entire leaves, newly emeiiging twigs and

inflorescence; fruits may also get covered with the mycelium of

the fungi, roots are however, not infected.

The infected leaves become chlorotic, deformed and often

killed. The flowers become deformed or blighted causing failure

of fruit setting. Blighting of twigs lessen or prevent the

formation of blossom bud for the next season. Fruits on infected

plant ripen prematurely and lack the texture, flavour and

contain reduced sugar contents.

The mildews are reported to perennate by means of

perithecia (Dash, 1913; Stevens, 1925), Many overwinter as

mycelium in the dormant buds of their hosts, and over winters

as oi\iinary mycelium (Treboux, 1914), and in seeds (Uppal et al,,

1935),

Large number ol cultivated and wild species of different

families have been recorded as the hosts of the members of

Erysiphaceae. Due to •ttiis disease a considerable amoxint of

damage has been recorded and at times it exceeds 209 . jagger

(1926); Milbrath (1927) and McKeen (1954) reported heavy losses

in the yield of Muskmelon due to powdery mildew while Szembel

(1930) estimated 759 reduction in the 3rield of cucumber, in

case of clover loss was iq)to i*0 percent (Horsfall, 1930). Suhag

and Duhan (1965) reported 23.42 percent yield loss in the seed

of radish,

The first serious attempt to stop damage caused by powdery

mildews were probably made in early nineteenth centuary, when

sulphur dust . came Into use for the control of mildew on fruit

trees* Since that tisie usage of fungicide against powdery mildews

has increased enormously. The value of other methods of control

is planting resistant yarieties» prtuonlng and burning mildewed

shoots and removing volunteer host plants have, also been

increasingly recognized. However, it is the application of

chemicals with or without the concomitant use of other measure(s)

which forms the principal defence against powdery mildews

throughout the world.

Generally, the members of family Braasicaceae, Cucurbitaceat

and Papillonaceae are economically important in various means

such as food value, medicine, timber and oil etc. are obtained

from their representatives, their economic importance can be

summarised as under;

FAMILY t BRASSICACEAE; The plants belonging to Brassicaceae

are cosmopolitan in distribution, but

the major centres of distribution are North temperate regions

especially the Mediterranean regions. Some of the plants are

alpine. In India, the family is represented by 25 genera and

200 species. Chiefly occuring in Western Himalayas and the

plains of North West India. A few species however, occur in

fiasteni Himalayas and the plains of North India. In South India

mostly cultivated species and few weeds associated with them

are found. Brassicaceae is of considerable economic importance

because many of its members are used as oil seed crops, vegetable

crops, medicinal and ornamental plants. Few economically

Important plants are as follows i

Brasalca caagjestrla (Venu Sarson): Oil extracted from the seeds

known as 'Karwa-tel*, largely

used as a medium of cooking and for preserving various pickles.

It is also used for lighting purposes.

Brasalca rapa (Vem. Shalgam): It is largely cultivated for

the sake of its leaves as well

as the thickened roots, which are consumed as vegetable either

raw or cooked.

Bntsaica Juncea (V«m« Ral) t ^ e seeds are used as a condiment

and also yield an oil which Is

used for cooking purposes and as an essential oil.

Raphanua aatlYua (Vem, Mill) t The leaves and the fruits are

eaten both raw as well as

cooked. The Juice of the fresh leaves is diuretic and laxative.

The seeds are carminative and also yield an essential oil. The

roots az*e used for urinary complaints.

FAMILY t CUCURBITACEAB t The family is spread over 110 genera

and 6^ species. In India^the family

is represented by 25 genera and 86 species. The plants are

mainly tropical or substropical, a few however, occur in

temperate zone. In our country a large number of plants are

cultivated for fruits. Some of them are as under t

Benlncaaa biapida (Vem« Patha) s The fruits which are of the

size of water-melon or

pumpkin are largely used both as a vegetable and in the prepara­

tion of sweets. The fruit is a laxative and useful in haemorrhages

from the intex*nal organs, the seeds are anthelmintic.

Cucxuais male (Vem. Kharbuza) i The plants are climbars or

creeping herbs, with large, soft, hairy leaves and spherical,

ovoid or elliptical fruits of varying size and colour. The

fruits contain protein, carbohydrates, fats, crude fiber, calcium,,

phosphorus, iron, copper, vitamins A, B and C. The seeds are also

edible and are d iuret ic . The pulp of frui ts i s beneficial in

chronic or acute eczema.

CucuMls melo rar . uti l isaimta (Vem. Kakri): The plants are

largely cultivated

for the sake of frui t vrtiich form an inportant art ic le for poor

class of people during summer months. The seeds are useful in

suppression of urine.

Cucumis sativua (Vem. Khira)t The plants are largely cultivated

for the sake of fruits and i t s

seeds have cooling e f f ec t .

Cltrullua vulgarla (Vem. Sarbuz) j The plants are largely

cultivated due to the fruits

which are largely eaten. The frui ts have cooling ef fect .

Cucurblta aaxlafc (Vem. Kaddu)s The frui ts are consumed as a

vegetable and the fruit pulp

i s used as a poultice for bui*n. Inflammation and bo i l s .

Cucurblta pepo (Vem. Kumra) j The frui ts are eaten as a

vegetable and the leaves are

used for external application on bums.

mrfa acutangula var. amara (Vem. Tlngatarul): The plants are

largely cu l t i ­

vated for the frui ts which are eaten as vegetable. The seeds,

8

l eaves and roo ts are used medicinal ly. The seeds are emetic

and are used as a purga t ive . The Juice of fresh leaves i s

droped in to the eyes i n granular con junc t i v i t i e s . The pounded

leaves are applied l o c a l l y i n leprosy .

Lagenarla Igucantha (Vem. L%ukl)t The p lan t s are la rge ly

cu l t iva ted for f ru i t s which

are eaten as vegetables . The dried she l l of the bo t t l e shaped

f r u i t s used for holding water and tha t of wild form " Tumri"

i s made in to »^ t a r« a s t r inged musical instrt iment. The decoc­

t i on of leaves mixed with sugar i s given in Jaundice, The pulp

of f r u i t i s applied to the soles in burning of the f ee t .

Moaoridlca charant ia (Vem. Karelai) { The Jtdce of leaves i s

emetic and i s used as

purga t ive . I t i s given i n b i l i ous affect ions and i s rubbed in

burning of soles of the f e e t . The f r u i t and the leaves are

useful In p i l e s , leprosy, Jaundice and as vermifuge. The Juice

of the f r u i t i s used i n snake b i t e .

TrlchOBanth»s aggtiina (Vtm. Ghlchlnda) s The p lan t s are la rge ly

cu l t iva ted for the

fxnilts which are eaten as vegetables , the seeds have cooling

effect*

FAMILY s PAPILIONACEAE : "mis is the largest family of the order

leguminales containing about 375 genera.

In India the family is represented by about 70 genera and 867

species. Indian representative of this family grow all over

India,in plain as well as on hills xipto 3000 to 8000 feet. They

are also grown as halophytes along sea-shore. The family is of

great economic value. A large number of plants are very ornamental

several are of either food value or of medicinal importance. The

most important ones are given as under :

Clcer arietinum (Vem, Ghana): An erect or spreading much

branched annual herb, cultivated

in India during winter months. Gram is the most important

pulse crop in India, ranking fourth among the grain crops in

acreage and production. The main producing areas are the upper

basin of the Ganges and adjacent tracts of the central India and

central province. Gram is the chief food crop for the people,

diabetic patients and for catties. Gram is a nutritive pulse

extensively used as a protein adjunct to starchy diets. The

plants when growing in fields exude an acidic liquid containing

Oxalic acid, Acetic acid and Malic acid. This can be obtain by

collecting the dew from the foliage.

Cajanua cajan Syn, indicus (Vem. Arhar) s A monotj^ic genus

comparising C, cajan,

an important leguminous crop, widely distributed in the tropics

and cultivated extensively for its seeds. The pulse is extremely

10

nutritious and eaten by all classes of people in India. 'Dal' is

used extensively as a protein adjunct to an otherwise diet. The

husk of pods and seed obtained during threshing constitute a

valuable cattle feed. The green leaves and tops of the plant

are consumed as fodder, they are also used as green manure.

Crotolaria juncea (Vem. Sanal): it is a tall stiff shrubs,

largely cultivated as a rainy

season crop for its fibre which is white silky and very strong.

The leaves and the branches as well as the seeds are given to

Hdich cows food. The waste after extraction of the fiber is

used in the manufacture of paper. The seeds are used medicinally

to purify blood.

Crotolaria retusa (Vem* Ghiinghunian): An erect robust under

shrub, attaining some

times a height of 15-20 ft. common throughout India, Ceylon and

Malaya, It is cultivated occasionally for fiber which is used

in admixture with sunhemp in cordage and canvas. The plant

popularly called Glory of Mahbaleshwar in Bombay. The leaves

contain Indlcan.

Dalbergia lanceolarla (Vem, Bithua, Takoll); A tall deciduous

tree with

yellowish white wood turning dark with age mostly straight

grained and medium coarse textured. It contains no heart wood.

11

It is strong, moderatly hard and heavy but not very durable. It

is used for tool handles and agricultural impliments. It is

suitable for carving, hoarding rafters, scantlings, packing cases

and general construction purposes.

Dedbergla slaaoo (Vem, Shlsham); A deciduous tree attaining a

height of upto 100 ft. and a

grith of 8 ft.It occurs throughout the sub Himalayan tract from

Ravi to Assam ascending upto 5000 ft. Shisham is extensively

cultivated in Punjab, Uttar Pradesh, Bengal and Assam, Sissoo,

like an Indian rose wood is a high class furniture and cabinet

wood, widely used throughout North India. On account of its

great strength, elasticity and durability, it is highly valued

as constructional and general utility timber and is used for all

purposes for which Indian rosewood is employed in the South. It

is esteemed also for railway sleepers, musical instrument and

electric casings etc.

Dalbergia volubilis (Vem. Nari Siris ): it is large woody

climber found almost

throughout India. The leaves are used as fodder, the Juice of

the leaves is applied in apathae and used as gargle for sore

throat. The root juice mixed with cumin and sugar is given in

gonorrhoea.

12

Dollchos lablab (Vex*n. Sem): The p lan t s which are twining herbs

are extensively cul t iva ted for

the pods which r ipen during winter months. The green pods are

pickled and a l so eaten as *Sag*.

Brythrina Indica (Vem, Indian coral tree)s I t i s a highly

ornamental t ree with

red flowers.

Lathyrus odoratus (Vem, Sweet pea)s The p lan t s are highly

ornamental and are la rge ly

grown i n gardens, homes, for the beaut i ful technicolour flowers.

Lathyrua satlvua (Vem, Xhesarl-tatri): A much branched sub

e r r ec t annual, found

throughout India as a weed and cu l t iva ted for pulse and fodder

especia l ly in northern, cen t ra l and western India upto an

a l t i t u d e of 1200 m. People i n s c a r s i t y areas consumed Khesari

as the p r inc ipa l a r t i c l e of d i e t for mouth are known to be

affected by a pa ra ly t i c disease known as Lathyrism.

Lena escuaeata (Vem, Nasur) t The p lan t s are la rge ly cul t ivated

as a cold weather crop throughout

Ind ia . I t i s considered as one of the most nu t r i t i ous among the

pu l s e s . I t i s eaten as a d a l . The young pods are eaten as

a vegetable . The p lan t afford a good fodder for c a t t l e . The

13

seeds are mucilaginous l axa t ive and useful i n const ipat ion and

other i n t e s t i n a l d i so rde r s . Vlhen made in to a paste i t i s

applied in u l c e r s .

Melilotus Indlca (Vem. Ban Methl): The p lan t s are annual herbs

with yellow flowers found as

weed in various crop f i e l d s . They are used as green fodder for

c a t t l e . The seeds are used in bowel complaints and in i n f a n t i l e

diarrhoea, the p l an t i s used ex te rna l ly as a fomentation or

pou l t i ce for swel l ings .

Phaaeolua aur'eus (Vem, Mung); A cul t iva ted very ancient legume

of Ind ia . I t i s an important

crop. The small oval seeds are highly n u t r i t i o u s and the green

pods are also ea ten . Over a hundred kind of mung beans are grown

in Cailna and o-ttier Asiatic coun t r i e s . The mungbean i s grown in

USA as a forage p l a n t .

Trigonell* jroemup-graecum (Vem. Methl): The leaves are eaten

as Sag. They are used

both i n t e r n a l l y and ex te rna l ly for t he i r cooling p rope r t i e s .

The seeds are carminative. An infusion i s given in small pox

as a cooling d r ink . They are also used i n dysentry.

CHAPrai 2

REVIEW OF LITERATURE

The powdery mildews are obligate specialized parasites

of angiospeinns having dark, spherical perithecia with colour­

less, uninucleate hyphae, producing conidiophores and conidia

which appear as white powdery growth on the plant surface due

to which Linnaeus assign the name 'Powdery Mildews' to this

group of fungi as back as 1753.

The multiplication of these ascomycetous fungi is restric­

ted to the foliage of living angiosperms. Its presence on the be

roots is yet to/established. However, the fungus parasitizes

stem*, leaves, flowers and fruits frequently. In the beginning

fungus appears in the form of mild infection producing small

patches on the host, later it become chlorotic and may kill

the plant as a result of severe infection. Infection leads to

the premature ripening of fruits which is accompanied by lack of

texture and flavour, of course lessen the sugar contents too.

Now and then fungus blamed to bring about failure in fruit setting

or reduction in its size. An amazing number of cultivated and

wild species belonging to different families have been recorded

as the hosts of the members of Brysiphaceae.

15

2.1 BRASSICACBAE i Brasslcaceae contains forage brasslcas,

horticultural and oil crops etc.,which are

very iniportant for the human beings as well as catties. Besides

other pathogens, crucifers are also attacked by the powdery

mildews. Originally Salmon recognized Eryslphe polygoni as a

pathogen of this group on swede and turnip. Hirata (1966)

reported species causing powdery mildews of crvicifers as

Srysiphe communis, Eryslphe clchoracearum, Leveillula taurica, aiKl

Oidium spp. But Junell (1967) recognised Eryslphe cruelferarum

to be the major Brysiphacean to attack the ci*uclfers.

Symptoms mainly consists of patches of their mealy

mycelium on the upper leaf surface; these gradually coalesce

until the entire surface Is covered by the pathogen, later

spread to the lower surface. Heavily infected parts become

chloratlc but death of the host usually takes a long time.

Disease Is cosmopolitan In distribution.

According to CJiupp and ^erf (1960) the crops such as

cabbage, Chinese cabbage, kohlrabi, broccote kale, mustar*d,

collaixls, cauliflowers, radish and Europe horse radish means

the horticultural crops which are consumed by humans are much

susceptible to powdery mildews, the disease found on all foliage

especially the upper surface and when severe leads to leaf

curling and abscission.

16

The powdery mildews of Brasslca and Raphanus species are

reported by Hirata (1966) as Eryslphe communis, Eryslphe

clchoraceariun, Levelllula taurlca and Oldliun species.

Sryslphe polygonl has been reported on Brasslca napus var,

olelfera from France by Darpoux (19A5), on rape seed

(B. campestrla) from Sweden by Anderson (1956), while Sawamura

(1957) reported Sryslphe polygonl on cabbage from Japan.

Powdery mildew In United Kingdom has only recently been

appreciated as a severe cause of yield loss. This is similar

to the situation with cereal mildew (Sryslphe gramlnis) which

was thought to have little effect on yield until Doling and

Large (1962, 1963) proved that heavy losses were attributable

to the disease. The statement that disease is not 'generally

a serious problem on brasslcas' (Channon and Maude, 1971) has

been made In Ignorance of the true situation in the field crops.

Al-Hassan (1973) reported Eryslphe communis on Brasslca

campeatris and Brasslca rapa, whereas Sryslphe cichoracearum

on Raphanus sativus from Iraq. Infection with powdery mildew

has been reported on rape and mustard seed crops in Europe and

India, Cook (1975)» however, suggested that in France and

Germany the disease is seen late in season and is not of

economic significance. In United Kingdom disease is regularly

seen on maturing crops, particularly on spring sown material,

differences In cultlvar resistance have been noted (Furber,

unpublished data).

17

In India , Bhunder e;;t a l , (1963) found ozily the conidial

s tage of mildew on Brassica juncea but they could successfully

inocula te seedlings of Brassica campestrig va r , sarson with

t h a t mildew ma te r i a l . The fungus on Brassica campestris va r .

Sarson and Brassica juncea was found to be amphigenous, d i r t y ,

white hyaline mycelium with ba r r e l shaped, hyaline granular

conidia, measuring 32.58x14.59M (42.0-24.5x19.5-10.5M) (Sankhla

e t a l . , 1967). Sankhla e t a l . (1967a) found the p e r i t h e c i a l

s tage of Erysiphe polygonl on Brassica campestris and Brassica

juncea. Per i thec ia were scatteired, b^rom to dark brown i n

colour, globose to subglobose, measuring 102.8M (77.0-1 26 .0M) i n

diameter bearing hypha l i k e brownish septate appendages and

containing 6-7 subglobose to broadly ovate s ta lked a s c i , each

f i l l e d with 3-5 hyal ine , oval to oblong one cel led ascospores.

Oidium l i n i , the powdery mildew of l l n seeds (Llnum

usitat lssimum) incidence were reported a t Jabalpur by Singh

and Kaurav (1973). They described tha t out of 69 l inseed

v a r i e t i e s and t h e i r crosses Kith E,C9832 was completely free

from powdery mildew during 1971-1972 while i t s 5 crosses i . e .

E.G. 9832 X Hira, E.G. 9832 x T 397, E.G. 9832 x No. 55,

E.G. 9832 X Rt and E.G. 9832 x Sabour (a) showed infec t ion in

t r e e s only. These were also found to be r e s i s t a n t to powdery

mildews a t Raipur during 1969-1970. The remaining v a r i e t i e s

crosses were highly susceptible to powdery mildews.

18

Levellla taurjca was observed on Lepldlum satlviiin from

Rajasthan by Desal et al. (197D). The fungus characterised as

whitish growth only on lower surface of lower leaves. Affected

leaves turn yellow. Mycelium endophytic, conidiophores emerging

out of stomata, singly, branched 1-5 times measuring 121.6-345.8 x

5.7D-7.6M (avg. 178.1AX6.84M), Conidia are hyaline, inaviculate

or cylindrical, straight, measuring A1,48*74.10x11.4-1 9.0M

(avg, 59,05x15.27M),

Khan et al, (1972) reported Ervslphe communis (Wallroth)

link on the living leaves and stem of Lepidium densifloinim

schrad from - Sopore (jammu and Kashmir),

Shanna (1980) reported powdery mildews on 5 Brassicas

viz, Capsella bursa-pastoris, Coronopus didymis, Raphanus sativus,

Iberis amara and Brassica juncea from Jammu and Kashmir state.

Radish and Brassica .luncea were the new host records for Jammu and

Kashmir while others were new Indian records.

According to Sahran and Kaushik (1981) the powdery mildew

disease of Brassica crops especially rapeseed and mustard was

considered as a minor problem tij-l recently. However, during the

months of March and ) ril (1960) the disease assumed an epidemic

form in Haryana and caused considerable yield losses to rape

seed and mustard crop,

Sahran and Kaushik (1961) reported the occurrence and

epidemiology of powdery mildew of Brassica. Brassica nigra

19

var«matopobka,Bra3sica napus var.tovyer,Brasslca campestris var,candle

and Brassica juncea v a r i e t i e s Blaze domo, leth~2?A, pahari ra i

RH-30 prakash, RIK-7&-6-1, RIK-78-6-2 and RC 781 were found

h i the r to , unrecorded host species and v a r i e t i e s of Srysiphe

cruciferarum opiz . ex. J u n e l l . from Ind ia ,

Pe r i t hec i a l formation on Brassica was favoured by

a l t e rna t ing low and moderate temperature, heavy sponi la t ion,

low n u t r i t i o n of the host, low r e l a t i v e humidity, dry so i l and

aging of the hos t .

For onset and epidemic development of powdery mildews

^^ Brassica« moderate temperature, low humidity, minimum ra in f a l l

or dry season during February and March months were congenial.

During 1963-84 crop season a severe out break of powdery

mildews was observed on the Radish cv. HH-1 raised for seed

production a t the farm of Haryana Agr. Univ. Hissar (Suhag and

Duhan, 1985) and also i n the c u l t i v a r s f ie ld around Karnal. The

present note embodies informations on the occurrence of sexual

stage of the pathogen, epidemic development of disease and

extent of losses in seed y i e l d . The weather var ia t ions v i z .

temperature and p r e c i p i t a t i o n prevai l ing during the month of

February to May 1964 were analysed to co r re la t e with disease

spread. The disease at tack a l l the a e r i a l p a r t s of the p lan ts ,

except lower por t ion of the stem. The ssnnptoms were f i r s t seen

i n mid Febmiary i n the form of small d i r ty-whi te floury patches

20

on the older leaves, the mycelium of the fungus produced

cylindrical conidia measuring 29.12-43.32 x 11.90-15.52M in

size. From mid April and onward dark peritheci? were found

scattered on the leaves but densely grouped on the pods, they

measured 71.80-119»10M In diameter and contained 3-5 asci per

perithecium. Appendages myceloid, septate unbranched and

about 1-2 times longer than diameter of perithecia. The

characteristics of the pathogen infect radish are confirming

with those of Bryslphe cruelferarum Opiz. ex. Junell. It was

seen that powdery mildews affected length of pods, number of

seeds per pod and weight of one thousand seed leading consequently

an average reduction of 23.42 percent in seed yield. As the

area of infection of pod increased there was a corresponding

adverse effect on all yield parameters.

Sahran and Sheoran (1988) reported that rape seed and

mustard powdery mildews caused by Bryslphe cruciferarum cplz.

ex. Junell has become one of the wide spread and serious disease

causing considerable yield losses in late sown and late maturing

cultivars all over India.

2'i2 CUCURBITACEAB i The identity of the fungus in case of

cucurbitaceaeous hosts had been in dispute.

Early European mycologist such as Leveille (1851), Passerini

(1867), Fuckel (1869) and Jackzewskl (1896) Identified the

causal organism as Sphaerotheca castengnei. Humphery (1892)

21

On the other hand iden t i f i ed the pathogen as Erysiphe

cicboraceanun* While Schroeter (1893) as Erysiphe poly^oni»

They based t h e i r i d e n t i t y on the p e r i t h e c i a l cha rac te r s .

Salmon (1900) for the f i r s t time observed the presence of

pe r i thec ia on Cucurbita pepo p lan t s infected with powdery mildew

fungus. In vrtiich each ascus contain two ascospores. Ihis

led him to conclude tha t the causal organism of powdery mildews

was Erysiphe cichoracearum ra the r than Sphaerotheca castengnei .

Subsequent s tudies by Rodigin (1936), Roder (1937) and Randall

e t a l . (1956) confirmed the findings of Salmon ( l o c . c i t ) as

a l l of them found the pe r i thec ia of Erysiphe cichoracearum on a

va r i e ty of cucurb i t s . In absence of perfec t stage Jagger

(1926 and 1931), Flkry (1936), Pa r r i s (1949), Ivanoff (1957)

McKeen (1954), Schmitt (1955) and Nikiforova (1962) also reported

the causal organism to be Erysiphe cichoracearum. While

Poretzky (1923), Szembel (1926), Uoz\iml e t a l . ( l 952) and Pa l t i

(1961) on the o the r hand reported the perfec t stage of

Sphaerotheca ful iginea on cucurb i t s . T&rr (1952), Nour (1957),

Boerema e t a l . (1964), Gtoster (l966) and Zacha (1968) also shows

the presence of Sphaerotheca fu l ig inea . Clare (1958), Ballantyne

(1963), Kable e t a l , (1963), Zaracovit is (1965), Jhooty (1967),

Nagy (1970, 1971), have conclusively proved these f indings. Ihey

based t h e i r i d e n t i t y on ce r t a in conidial charac te r s ; such as

colour of mycelium, shape of conidia, presence and absence of

f ibros in bodies and shape of germ tube .

22

Cvjetkovic et al. (1988) confirmed that isolates collected

from the cucumber plant were belong to Sphaerotheca rather than

Sryslphe cichoracearum« Their assumption was based on perithecia,

Khan and Al-Ammari (1967) on the other hand reported

three pathogen viz. Erysiphe cichoracearum. Leveillula taurica

and Sphaerotheca fuliginea during a survey of powdery mildews

on cucurbits listing Libya one of the few countries, where all

the three pathogens of powdery mildew of cucurbits were present,

Sphaerotheca fullginea was predominant, infecting all the

Cucurbits grown throughout the country. Erysiphe cichoracearum

and Leveillula taurica were present on indoor cucumbers.

Sokolov et al. (1977) reported Erysiphe cichoracearum

and Sphaerotheca fuliginea on water melon in Astrakhan region

(USSR) which later become dominant.

In the Imperial valley California, Kontaxis (1977) found

Sphaerotheca fuliginea as the causal agent of powdery mildew of

watermelon fnd.ts, but it only occured on the leaves of muskmelon

and cucumber. Hyperplastic growth (pimples) was frequently

present on watermelon fruit and closely associated with

infection.

According to Molot et al. (1966) out of three different

species of powdery mildews of cucurbits growing areas, only

two viz. Sphaerotheca fuliginea and Erysiphe cichoracearum are

23

of major economic importance in France. Powdery mildew of melon

(Cucumis melo) caused by Sphaerotheca fuliginea in Brazil was

reported by Reifshneider et al. (1965). Sphaerotheca fuliginea

race 1 not the gryalphe cichoracearum as previously reported was

Identified as the causal agent of melon (Cucumis melo) powdery

mildew in three Brazilian states. Identification of Sphaerotheca

fuliginea was based on characteristics of Oidium state as well

as on reactions of standered race differentials.

In India,Butler (1918) reported Erysiphe cichoracearum

on Coccinia indica, Trichosanthes dioica and ^ omordica balsamlna.

Vasudeva (1960) listed Bryonopsis laciniosa, Citrullus vTolgaris

Coccinia cordifolia. Cucumis melo« Cucumis sativus. Cucurbita

species and Trichosanthes anguina. In addition to the above

hosts Rajendran (1965) reported Erysiphe cichoracearum on

Lagenaria vulgaris. Mathur et al. (1971) recently reported

Erysiphe cichoracearum on Cucumis melo var. utilissimus.

Sharma (1978) reported that there were two powdery mildew

pathogens of cucurbits in India viz. Sphaerotheca fuli^inea

[(Schlecht)Fn] and Erysiphe cichoracearum DC.ex.-Merat, of these

the former exhibit comparatively wider range of geographical

distribution than the later. Erysiphe cichoracearum, the other

powdery mildew which infect cucurbits in India is however, not

known to occur in Jammu and Kashmir state so far. Although

Khan £t al. suggested that its Tperaence In the state can not be

totaly ruled out in view of its existence in some neighbouring

2U

states. According to Khan et al. (1971) powdery mildew is a

serious widespread disease of cucurbits in India. The occurrence

of Sphaerotheca fuliginea (schlecht) poll and Erysiphe

cichoracearum DC. on cucurbits was pointed out by Khan et al.

(1974) in various parts of the world. While in India^as early

as 1918 Butler reported theoccxjrrence of both organisms on

cucurbits on the basis of conidial characters. Jhooty (1967)

claimed that Sphaerotheca fuliginea was responsible for the

disease in Punjab. Kapoor (1967) in CMI descriptions of the

Sphaerotheca fuliginea and Srysiphe cichoracearum described that

Sphaerotheca fuliginea exclusively attacks cucurbits where as

Erysiphe cichoracearum is confined to the members of compositae

and other non cucubitaceous plants.

During the survey of cucurbit growing areas Kaur and

Jhooty (1985) found that out of the twelve cultivated cucurbits

only six were infected by Sphaerotheca fuliginea, severe

infection was observed on the leaves of Cucumis melo, Cucumis

melo var. utillssimus, Cucurbita pepo, Lagenaria siceraria and

citrullus lanatus during Ihe month of MayandJuly Luffa cylindrica

which is also a predominant cucurbit during this season was

conipletely free from infection. During winter season (Nov-Jan)

severe infection was observed on the leaves and fruits of

Luffa cylindrica and Lagenaria siceraria. Cucurbita pepo and

Lagenaria sicereria were infected by all the isolates and

Cucumis melo, was resistant to isolate 5 and 6 and moderately

25

resistant to isolate 2, Cucumis melo var. utilisslmus was

moderately resistant to isolate 5.

Mital and Akram, (1985)reported that Cucunds sativus is a

common host of cucurbit powdery mildew viz. Srysiphe cichoracearum

and Sphaerotheca fuliginea under Indian conditions. Powdery

mildew appeared moderately when plants were inoculated with

Sphaerotheca fuliginea, Only infection of both pathogens occured

when different leaves of a single plant were inoculated with

conidia of Brysiphe cichoraceai*um and Sphaerotheca fuliginea,

consequently both the pathogens also appeared on a single leaf

when half portion of a leaf was inoculated with conidia of

Erysiphe cichoracearum and the other half with conidia of

Sphaerotheca fuliginea respectively. The time taken for the

appearance of disease is same in either case.

Khan (1977) observed that Sphaerothea fuliginea is

widely distributed and infect most of the cucurbits in Bihar,

while Erysiphe cichoracearum is confined to Coccinia ccrdifolja.

In the host range studies of Sphaerotheca fuliginea,

Akram ^ al. (1976) tested the relative susceptibility of 7

cultivated and 10 wild cucurbits as well as non-cucurbits

against 5 isolates of Sphaerotheca fuliginea. This species is

probably the principal cause of cucurbit powdery mildew in the

North India.

26

According to Khan and Khan (197D) although powdery

mildew of cucurbits occurs i n almost a l l the cucurbi t growing

areas of the world, yet pe r i thec ia are seldom produce. Since

1900 the perfec t stage of t h i s fungus has been known as Erysiphe

cichoracearum DC. as proposed by Salmon (1900). In the year

1956 Randall and Menzies a lso iden t i f i ed the per fec t stage of

cucumber powdery mildew as Erysiphae cichoracearum.

Kapoor (1967) recent ly described the per fec t stage of

powdery mildew of Cucumis melo as Sphaei^Jtheca fu l ig inea . Sohi

and Nayar (1969) obtained p e r i t h e c i a l stage of Sphaerotheca

ful iginea on Cucurbita moscfaata from Himachal Pradesh.

Khan and Khan (197D) reported the production of per i thecia

° ^ Spfaaezx>theca ful iginea on several v a r i e t i e s of Laginaria

leucantha and Cucumis sat ivus under g lass house conditions from

Aligarti . Khan e t a l , (1972) again observed the pe r i thec ia l stage

of Sphaerotheca ful iginea on the l i v ing leaves and stem of

Lagenaria leucantha.

Paul and Kapoor (1982) reported tha t the pe r i thec ia l

formation of Levei l lu la i s general ly believed to be rather

severe and ingenus, has mostly been reported i n i t s conidial

stage a l l over the world. They observed tha t two host species

were found to contain pe r i thec ia which were iden t i f ied as

Levei l lula t au r i ca (Lev.) Arn, (Amdes).

21

Cucurbit powdery mildews seldom produce perithecla in

nature, perithecia of Sphaerotheca fuliginea are produced on

certain cultivars of Cucurbita moscbata Poiret, Cucumls sativus

Linn., Cucumis melo var. momordica Roxb, Cucumis melo var.

utilissimus (Duthey & Puller), Cltrulus vulgaris Schrad.,

Lagenaria leucantha (Dichl) Rushy, and Luffa cylindrjca Linn.

The interesting feature was that perithecia produced only on

r Laginaria leucantha, Cucumis sativus, Cucurbita moschata and

Citrullus vulgaris, possessed asci each containing 8 ascospores.

While in other cases the asci lack ascospores under glass house

conditions at Aligarh (Akram, 1964).

Mir et al, (1988) reported the presence of perithecial

stage of Erysiphae cichoraceaiMm DC. in vivo on pumpkin, was a

new record for India and its presence on cucumber and Lagenaria

siceraria was also a new report from Jammu and Kashmir state.

2.3 PAPILIONACBAE J The family papilionaceae is of considerable

economic importance,because pulses belonging

to this family, are used as a source of food/protein. Members of

this family are often attacked by a number of pathogens includ­

ing powdery mildews. Most of the crops belonging to this family

are parasitized by Erysiphe species (Kapoor, 1967a).

Powdery mildews of pea (Pisum sativum) caused by Erysiphe

pi si (often reffered as Erysiphe polygoni; Kapoor 1967a),

28

Pea is an important pulse and vegetable crop of subtropical

and teniperate regions of the world. According to Haware (1971)

powdery mildews of pea caused by E^ysiphe polygoni DC. is an

important disease which cause severe damage to this crop. The

disease occur in epidemic almost every year in Madhya Pradesh.

Singh and Singh (1977) described that it become a limiting

factor in the production of pea in Uttar Pradesh and occurs in

varying intensity every year depending upon climatic conditions.

According to Jhamaria and Dalela (1974) Srysiphe poly go ni

DC. on Pisum sativum var. arvense Poir, appear in epidemic form

every year in Rajasthan. The disease cause severe losses to

this crop. No variety was found to be resistant. Raut and

Wangikar (1979) also observed the epidemic form of this disease

every year in varying intensity which leads to heavy reduction

in the yield, L^pal et al. (1935 ) reported that the infection

was ao severe that even one picking was not possible against six

to seven picking from normal crop.

Mahmood et al . (1963) estimated the yield losses of pea

due to powdery mildews in Pakistan. The yield losses caused by

Srysiphe polygoni in eight garden pea varieties were 10.1-18.0.

Krishna al. (1987) observed that Ervsiphe pisi DC.often

assumes epidemic properties on pea especially when favourable

weather conditions prevails even for a small duration.

29

Mandloi et al. (1968) found the perfect stage of Srysiphe

polyja:oni on pea. The perithecial formation of Eryslphe polygonl

DC, on pea is of rare occurrence, has been recorded consistently

on pea crosses.

Krishna and Mishra (1989) studied the powdery mildew caused

by Brysiphe pisi DC. on twelve pea cultivars during rabi of 1983-

1964 and 198A-1965. The observations on apparent infection ratio

showed that cultivar IPS-207, IPS-77, IPS-293, IPS-241 and IPS-96

were resistant to powdery mildews due to retard mycelial growth

(slow mildewing). The slow mildewing cultivar had longer latent

period, smaller and fewer conidia per speck in comparison with

fast mildewing ones.

Bhaixiwaj et al « (1987) reported heavy losses of pea crops

in Himachal Pradesh due to the infection by Brysiphe polygoni.

All commercially available varieties were found to be susceptible

to disease. In field trials 99 pea varieties were screened for

resistance, out of these 4 were resistant, 7 were moderatly

susceptible and 54 highly susceptible.

Besides pea a number of papilionaceous plants are the

hosts of powdery mildews. The list include Cicer, Cajanus,

Phaseolus, Lens. Trifolium, Lathyrus.Medicago. Vicia. Glycine.

Robinia. Erythrina, Vigna. Crotolaria. Dolichos, Pongamia.

Tephrosia. Dalbergia. Desmodium, Trigonella, Astragallus etc.

The crops like Cicer arietinum, Cajanua cajan. Phaseolus mungo.

30

Phaseolua aureus Lens esculenta are attacked by Eryslphae pisi

(Gupta, 1974), These crops were also at risk from Levelllula

taurica. This pathogen was reported on pegion pea (Cajanus

cajan) in India (Kamat and Patel, 19A8); several workers reported

this pathogen from various parts of the world as, viz., In Sudan by

Tarr (1955) and on chickpea (Cicer arietinum) by Tarr (1955).

A full account of host range and distribution was given by

Hirata (1966).

The first United States report i»evealed that soybean

(Glycine max) was infected by Erysiphe polygoni DC.(Lehman,1931)

but later workers (Dunleavy et al ,, 1966; Johnson and Jones,

1961; Paxton and Rogers, 1974) (U.S. Dept. of Agr. 1960) identified

the fungus as Microsphaera diffusa which was confirmed again by

Amy et al. (I975)i when they reported Microsphaera diffusa on

the same host from Wisconsin, Garcia t al. (1984) found

perlthecia of Micrx)sphaera diffusa on soybean in field as well

as in nursery. Under field condition infection began after

flowering, but on inoculated plants it occured at all stages.

Erysiphe trifolii is common on Trifolium and Lathyrus

which is occasionally seen on other leguminosae (Kapoor, 1967a),

Trifolium species have been reported to be infected by a range

of Brysiphe species such as Brysiphe communis, Erysiphe martii

and Brysiphe polygoni, The other legumes such as lucerne

(Medicago) and vetch (Vicia) have also been found to be infected

31

with Bi^slphe species (Boughey, 1946; Hirata , 1966; Connors, 1967;

Oran, 1974). While Levei l lula taur ica can cause disease in a l l

herbage legumes especia l ly in Mediterranean, Middle and Par

Eastern Regions, Afghanistan, Iran (Ershad, 1971), who referred

the pathogen as Levei l lula leguminosarum, I s r ae l (Chorin and

P a l t i , 1962); Sudan (Tarr, 1955; Zapromentoff, 1930). Various

Vicia species were a lso infected by powdery mildews, t h i s i s

usual ly a t t r ibu ted to Brysiphe poly j^ni , In California and

Georgia, however, Microsphaera has been iden t i f i ed as causal

organism although th i s may be l imi ted geographical ly. Other

repor ts of Srysiphe polygoni on Vicia has been made by Tarr

(1955) in Sudan; Al Hassan (1973) from Iraq reported srysiphe

cichoracearum while Oran (1974) observed Brysiphe communis on

Vicia from Turicey.

Both Phaseolus and Vicia species may be attacked by

Levei l lu la t au r i ca , t h i s had been reported in Sudan (Boughey,

1946). Additionally Oidium erypsoides was reported in Argentina

on peas and beans (Feldman and Pont is , i960) . Beicht and Wessel

(1963) found srysiphe cichoracearum on beans in West Germany,

In glasshouse grown beans (Phaseolus vxilgaris cv. favori te)

showed typ ica l powdery mildew symptoms often combined with

vein necrosis i n summer of 1979 and 1980. The disease h i th r to

undescrlbed in West Germany could be t ransferred from beans to

cucumber €Uid vice versa . Several beans cu l t i va r s were infected

na tu ra l ly and infec t ion could be induced a r t i f i c i a l l y .

32

In India, Chona and Munjal (1955) reported Sryslphe polysoal

on the l iv ing leaves of Vicia e r v i l i a wild from New Delhi.

Patel e t a l . (1949) studied Erysiphe polygoni DC on Phaseolus

mungo var . raj[;l^atu3 and Vigna cat.jang, Levei l lu la t auric a on

Caplanus ca^lan, C?rotolaria .luncia. Crotolar la usuramoensis. Medicaji;o

sa t iva and on the leaves of Dolichos lablab , whei^as Oldium species

on the leaves of Cix>tolaria s inens i s . Erythrina indica and

Pongamia glabra»

Erysiphe polygoni was a lso reported on the leaves, stems

and pods of Tephrosia purpurea by Chona and Munjal (1955). Varma

and Daftari (1974) also given the s imilar repor t on Tephrosia

purpurea. The mildew was found to have hyaline mycelium, the

pe r i thec ia were scat tered brown to dark brown in colour, super>-

f i c i a l , almost globose with 108.10-169.50 ( 1 4 3 . 8 3 M ) in diameter

bearing myceloid appendages and contained 3-8 broadly ovate

s l i g h t l y stalked to s e s s i l e a s c i , measuring 39.95-61.10 x

25.85-42.30 (avg. 50.14 x 34.43M). Each ascus contained 3-5

(more frequently 4) oval,oblong, one celled ascospores of

13.90-25.85x9.40-16.45 (avg. 1 8 . 3 0 X 1 2 . 3 5 M ) in s i z e .

Sohi e t a l . (1966) described Sphaerotheca macularis on

Phaseolus mungo L. from Himachal Pradesh. The i r r egu l a r patches

of fungus covered almost en t i r e l ea f surface and gave a d i r ty

white appearance to the l ea f . Per i thec ia gregarious brown to

dark brown in colour, globose to subglobose measuring 62.2-90.8 x

55.9-83.8 in diameter; ascus hyaline, s ingle , 7-8 spored,

33

subglobose to broadly ovate without a s t a lk , un ice l lu l a r asco-

spores broadly oblong to e l l i p so ida l i n shape, measured 18.6-23.3 x

16 .3 -20 .9M.

Wilson (1966) reported from Kerala t h a t Oidium species

p a r a s i t i z e s Desroodium t r i f lorum. The m3rceliuni of fungus was

slender, supe r f i c i a l , hyal ine, sep ta te , forming white powdery

coating on e i t h e r side of the l eaves . The conidiophores were

simple, hyal ine, un i ce l lu l a r cy l indr ica l with rounded ends

measuring 20.1-35.7 x 11.9-17.0M.

Sankhla ^ £!• (1967) reported Srysiphe polygon! on l e n t i l

(Lens esculenta Moench) from Ja ipu r . In February the plants

showed white patches, begining on lower side of leaves which

l a t e r enlarged and covered both the leaf sur faces . At maturity

in fec t ion was a lso observed on pods. Heavy infec t ion produced

ch loros i s , cur l ing and de fo l i a t ion of l eaves .

Desai e t a l . (1970) reported Leveil lula taur ica on

Trigonella c o m i c u l a t a . Affected t i s sues turned yellow, conidio­

phores emerged out through stomata from endophytic mycelium.

Kumar e t a l . (1975) studied Erysiphe communis (Wallr.)Link.

on the leaves of Astra^allus species from Laddakh (Jararau and

Kashmir) while Paul and Munjal (1982) observed Erysiphe marti i

l e v . on the leaves of Trifolium repens from Palarapur.

34

Paul and Kapoor (1964) r epor t ed Erysiphe aesmodli on

Desmodium s p e c i e s from Punjab . The powdery mildew on Desmodjum

s p e c i e s was e a r l i e r r epo r t ed t o be Erysiphe communis (Wal l r . )

L inn , G i l l e t a l , . , 1961 found i t to be d i s t i n c t from a l l

Erysiphe Hedw. f l l . and i s being desc r ibed as a new s p e c i e s .

Gohokar and Peshney (1985) found L e v e i l l u l a t a u r i c a on

Cajanus ca jan L. (Mi l l ) s p . , the n a v i c u l a r h y a l i n e conidia were

measured 42-77Mm x 14-28wn (Avg, 58.00 x 19.58)um), borne s i n g l y

on s h o r t or e longa ted conidiphoi^es measuring 74.0-189.4Mffl x

8.08-8.60Aiin (124.98 x 8.38ium) emerging through s tomata .

Pandey £ t a l . (1989) observed Erysiphe p i s i on Faba bean

fo r the f i r s t t ime i n I n d i a . The d i s e a s e i n t e n s i t y va r ied from

60-7096.

l a longo (1964) observed t h e powdery mildew fungus on

Roblnia pseudoacacia a s Microsphaera psedudoacac iae . Teyegaga

(1967) r epo r t ed Phy l l ac . t l n i a on the l e a v e s of S rv th r ina

l y s l s t e m o n . The fungus was c ro s s pa thogenic to i t s usua l hos t

paw-paw.

2.4 ENVIRONMENT AND POWEERY MILDEWS ; The effect Of environ­

mental factors on powdery

mildews has been extensively studied by GrafMarin (1934),

Cherewick (1944), Yarwood (1957), and schnathorst (1965).

Yarwood (1957) and Schnathorst (1965) claimed that the development

35

of powdery mildews in general was favoured by warm humid weather

(Anonymus 1946, 1950); in glasshouse conditions as against out

door conditions (Steiner, 1908; Tucker, 1852) and hot dry weather

(Wager, 1937). Out of various environmental factors, temperature

and moisture have been reported to have profound effect on

powdery mildews.

The cardinal temperature for germination of conidia of

different strains of Srysiphe cichoracearum ranged between

5-35°C (Levykh, 19A0; Deslandes, 1954; Rossouw, 1959; Schnathorst,

I960; Morrison, 1961, 1964 and Tafradzhiiski, 1963), for

infection and growth ranged between 5-32* 0 (Levykh, 1940;

Deslandes, 1954; Minev, 1957; Rossouw, 1957, 1959 and schnathorst,

1960), Conidial germination of Erysiphe cichoracearum from

lettuce was highest at 18* C (Schnathorst, I960). The cardinal

ten?)erature for infection was 6-10 C (minimum), 18 C (optimum)

and 27°C (maximum).

Related to the environmental factors, the more contro­

versial aspect is the relative humidity. It also plays an

Important role for the germinationi of conidia. Hashloka (1937)

found that conidia of SphaeI theca fuliginia from cucumber

germinated between 15-85 percent relative humidity. The

survival of conidia was 14 days at 76 to 80 percent relative

humidities and so far 30 days in a saturated atmosphere.

Tafradzhiiski (1963) reported that the conidia of the same host

of a Sphaerotheca fuliginia germinated best at relative humidity

36

of 9U percent but they failed to germinated In drops of water.

Germination of conldla was also observed in calcium

chloride chamber at 0.1 percent relative humidity by Morrison

(1961, 1964) and Schnathorst (l960)»Conidia were also germinated

at 0 and 100 percent relative humidities as reported by Roussow

(1959). Comers (1935)i Minev,/(l957);Morrison, (1961, 196A)and

Tafradzhiiski (1963) observed that free water inhibit the

germination of conidia. Morrison (196A) observed that the free

water on leaf disc surface inhibit the germination of conidia

of large number of powdery mildews fungi, but high relative

humidity favoured the germination, Nour (1958) studied the

effect of the different relative humidities on the percentage

germination of conidia of various powdery mildew fungi.

It had been claimed that both infection and incidence of

powdery mildews were severe under dry condition rather than

wet climatic condition (Wager, 1937; Anonymous, 1945; Boughey,

1949; Palti, 1953). D'Angremond (1924); Blumer (1927); Blumer

(1927); Deslandes (1954) and Morrison (1961) reported that high

relative humidity favoured the incidence of powdery mildews.

Brisley (1926); Beeley (1932); Moore (1936); Fisher (1938);

Bremer (1940) and Parris (1949) were also of the opinion that

overhead irrigation favoured the development of powdery mildews.

Schnathorst (1959) reported that the growth of mycelium was

abnormal, when a film of moisture was present on the surface

37

of epidermis. Yarwood (1939); Schnathorst (1959); Morrison

(1961) on the other hand reported that the film of free water

did not favour the development of the powdery mildews. An

observation was made by Salmon (1903); Yossifovitch (1923) and

Moseman et al, (1957) that free water was essential for the

maturation of ascospores.

THie conidia of powdery mildews fungi have been found to

germinate at a wide range of pH but highest germination was

observed at 6,6 to 7.0 pH (Yarwood, 1957).

Childs (19A0) observed a diui*nal cycle in maturation of

ascospores in certain powdery mildews. Periodic microscopic

examination of the cucumber infected with Erysiphe cichoracearum

revealed a more complex diurnal cycle of conidiophore develop­

ment. Abstriction occured between 6-8 a.m. and than at 2-4 p.m.

and formation of the succeeding crop of conidia occured between

2-4 p.m. and 6-8 a.m. Highest abstriction of conidia of

sunflower powdery mildew occui^d between 8 a.m. to 2 p.m.

The germination of conidia was also influenced by the

time of collection. Yarwood (1936) reported that the highest

germination of conidia of Erysiphe polygoni occured when the

spores were collected in the afternoon, their germination however,

decreased with the onset of the darkness and the least germina­

tion was observed in early morning. Jhooty (1970), while

38

confirming the above findings pointed out that such diurnal

cycle was present in Sphaerotheca fuliginea, Sphaerotheca

macular!s, Erysiphe graminis and Erysiphe cichoracearum. However,

Yarwood (1936) suggested that regular alternation of light and

dark periods may be responsible for expression of this phenomenon.

Jhooty (1971) was of the view that alternation of light and dark

period may not be the basic cause of this phenomenon but it

certainly influenced the onset of low and high cycle in germina­

tion of conldia of Erysiphe polygon!,

Different environmental factors also influences the

production of perithecia (Yarwood, 1957). Buchheim (1928) and

HJ.umer (19A8) reported that low relative humidity favoured the

formation of perithecia. Similarly, Bioletti (1907) reported

that generally low temperature favoured the development of

perithecia in powdery mildews. On the other hand, Cherewick

(1944); Arya and Ghemawat (l954) reported that in Erysiphe

graminis formation of the perithecia and ascospores was favoured

at alternating moderate and low temperatures. Schnathorst (1959)

reported that the formation and maturation of perithecia was

also a matter of time rather than cyclic changes in temperature

or alternate wetting and drying. He observed the formation of

perithecia of Erysiphe cichoracearum at 23 C with 300 foot candle

illumination in leaf culture in 7 days. Perithecial development

was also reported by Schnathorst (1959) at 13°C with 60 percent

relative humidity and 900 foot candle illumination. These

39

observations led to conclude that the perithecla rarely develop

in tropics. Bessey (19A5), Ainsworth (1950) and Yarwood (1957)

reported that amongst different climatic factors, temperature

appeared to be more important for perithecial production. However,

this is not true in India, a large number of perithecial develop­

ment had been observed in powdery mildew fungi.

Severity of mildews is directly related with plant vigour

and that any soil or other factors which promote plant vigority

(Arnaud and Arnaud, 1931; Smith and Blair, 1950). Trelease and

Trelease (1928) and Mansson (1955) found that low nitrogen and

high potassium reduced the development of powdery mildews.

Cole (1960, 1966) on the other hand, reported that the plants

grown in water culture fortified with all the elements, were

more susceptible to Srysiphe cichoracearum, than those grown in

which the ratio of potassium and nitrogen was low, Laibach

(1930) and Homma (1937) reported that low nutritive conditions

of host favoured the development of perithecia.

2.5 POWDERY MILDEW FUNGICIDES i The damage due to powdery

mildews may be manifested as

direct fall in yield, as a suppression or distortion of plant

growth, as a spoilage of fruit or as a disfigurement of ornamental

plants which last in longer terms affects )d.eld. To make plants

free from pov/dery mildews various tjrpe of fungicides are in

usage. Some of then are as under i

^

2.5.1 Sulphur s Sulphur is the oldest and cheapest remedy to

control the powdery mildews. The use of

sulphur was reviewed by McCallan (1967) and Shajrvelle (1969).

Sulphur is applied mainly as a fine dusting powder at

rates which vary between 5 and UO kg sulphur ha . A small

proportion of kaolin and bentonite is commonly added to prevent

the tendency of the sulphur particle to clump together. Wettable

powder and colloidal liquid formulation are also available;

these usually contain 6O-Q0% sulphur. They are diluted with

water and applied in high volume sprays at about 1000-10000 ppm,

sulphur, or in spray at correspondingly increased concentrations.

Lime sulphur made by boiling at aqueous suspension of calcium

hydroxide with sulphur, is a concentrated solution of calcium

polysulphides together with a little calcium thiosulphate. On

mixing with water and exposure to air the product decomposes to

a fine suspension of sulphur particles. Sulphur is also applied

by volatilization. Vapour tends to control mildew better on the

upper leaf surfaces than on the under-sides.

Sulphur exerts its fungicidal action at the surface of

leaves, stems, flowers or fruits to which it is applied. It is

redistributed over such surfaces to a limited extent by vapori­

zation and also by the action of rain and dew. It does not

penetrate into plants or move through them to an extent sufficient

to protect the new parts of the plant which appear after

treatment and which are often highly susceptible to powder mildew.

41

I t must be applied repeatedly to p ro tec t these new t i ssues and

so offse t losses caused by weathering. Coating of sulphur on

t rea ted p lan ts wi l l p ro tec t them for sometime from infect ion by

hindering or preventing the germination of powdery mildew spores.

Powdery mildew grow mainly on the plant surface, applied

sulphur can come in to d i r e c t contact with ex is t ing mycelium and

suppress i t s growth and sporu la t ion . Sulphur tends to work

b e t t e r i n warmer coun t r i e s .

Sulphur does penetra te in to p lan ts to a l imited extent,

and can cause damage. Rapid ' scorching ' (d i rec t local injury)

of leaves tend to occur in h o t t e r c l imates .

Martin (1964) and Tweedy (1969) have suggested tha t

sulphur i t s e l f i s the primary toxicant , i t . must f i r s t be oxidized

to sulphur dioxide or t r i ox ide or to sulphuric acid, or i t must

be reduced to hydrogen sulphide.

The ul t imate biochemical s i t e s of act ion of sulphur and

the basis of the specia l s e n s i t i v i t y of powdery mildew fungi

have not been explained.

2.5»2 Dinitrophenols : Dinocap i s second to sulphur in general

importance as a powdery mildew fungicide.

Dinocap was f i r s t synthesized as an aca r ic ide . Dianocap i s a

mixture containing 65-70% of 2, 6 dini tro-4-octylphenylcrotonate

(dianocap-4) and 30-3596 of 2,4-dini tro-6-octylphenylcrotonate

42

(dianocap-6) (Kirby and Hunter, 1965; Byrde ejt al., 1966;

Kirby et al., 1966).

Dianocap is formulated mainly as a 25% W/W wettable powder

or as a 50% W/V emulsifiable liquid. High volume sprays applied

at concentrations of 200-250 ppp dianocap at 10-1A days interval,

at 100-125 ppm at shorter intervals. It is used widely on

cucurbits but is very expensive. The dinitrophenols are all

surface fungicides. Esterification to the crotonate and the

addition of the octyl side chain is some way confer specificity

of action towards powdery mildews.

2.5.3 Qulnomethionate; Formerly known as oxythioquinox. It

gives good control of powdery mildew,

when applied in programmes of repeated sprays, such as currents,

goosebrries, strawberries and cucurbits and it is used both in in

the glass house and^the field. It is also expensive and can

cause damage to some crops. Qulnomethionate is a surface

fungicide, having protectant, curative and antisporulant action

(Sasse, 1960).

2 .5 .4 2"Amlno-pyrlmi<iinea : Dimethirimol, Bthirimol and

Bupirimate (systemic fungicides)^

these three compounds are read i ly t ranslocated upwards in the

xylem, but are not moved out of t rea ted leaves and are not t r an s -

poi'ted downwards i n the phloem. They can be applied to roots,

either by so i l incorporat ion or by seed t reatments ; a l t e rna t ive ly

they can be used as sprays.

43

Dimethirimol was introduced first, mainly for the control

of cucurbit powdery mildews (Ellias et al., 1968). One application

of 0,25g a,i..as an aqueous soil drench around the base of a

large cucumber plant in a commercial glasshouse for at least

six weeks conferred complete protection on the whole plant.

Bupirimate, a sulphamate derivative of ethirimol, used as

a spray treatment to control the mildew of cucurbits and other

crops (Bent, 1974; Finney et al,, 1975). But it is much less

effective than dimethirimol and ethirimol as a root treatment.

The pyrimidines have a direct action on powdery mildew

fungi. They can inhibit spore germination in vitro when applied

to roots, dimethirimol and ethirimol exert effect at the surface

of the leaves, inhibiting mildew development (Bent, 197D), Other

effect include a •' repellent" action on vegetative powdery

mildew hyphae,

2»3*3 Triforlne : Triforine is a piperazine derivative, bearing

a certain structural relationship to

chloramiformethan. It is highly active against powdery mildews,

in general, and also against a number of other diseases (Fuchs

et al,, 1971). It is systemic, moving in the xylem system, and

has protectant, curative and translaminar effects. It has come

into use in the past few years as a spray for the control of

powdery mildews of cucurbits, peas, etc. giving concomitant

control of other diseases.

CHAPTER 3

PLAN OF VTORK

Brasslcaceae and Papillonaceae families are not free from

the infection of powdery mildew, due to this disease a

considerable amount of damage to crops is done every year. The

review of literature clearly explains that little attempt has

been made to study the causal organism of the powdery mildews

on different members of these families. Moreover, meager is

known about the incidence of the factors affecting the disease

development. Keeping in view, the above facts it is considered

to study the following aspects :-

1. To survey the incidence and severity of powdery mildew

on the members of Brassicaceae and Papillonaceae from

different parts of Uttar Pradesh.

2. Identification of the causal organism of the powdery mildew

and measurement of conidia and conidiophores. Existence

of races, if any.

3. Estimation of sugar and nitrogen in susceptible and

resistant plants in order to correlate it with the disease.

4. Effect of systemic fungicides for the control of the

powdery mildew,

5. Bffect of some phylloplane fungi on powdery mildew disease

development.

\^ HIMACHAl / PRADfSH

1

UHAR PRADESH

' UTTAWCASH

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MttfwT ( r \ •

^ SfTAnjR \ • \

NEPAL

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MAOHYA PRADESH )

8JHAR

^ STATE CAPITAL

• D I S T R I C T HEAOOOAHTtRJ

CHAPTER k

MAERLALS AND METHODS

4,1 SDRVBY t A regular visits will be made to assess the

severity and prevalence of the disease during

their growth periods at Allgarh and Its adjoining areas, where

the members of families Brasslcaceae and Papllionaceae will

be grown. The severity of powdery mildews will be graded as

under t

No Infection (-)

Mild Infection (+)

Moderate infection (++)

Severe Infection (++•)

No visible disease symptoms

A few pustules, small in size

and scattered.

Many pustules, larger in size

tending to cloalesce.

Big pustules covering almost

the entire leaf areas.

4.2 IDENTITY AND MAINTgNANCE OF PAmOGEN; To Identify the

pathogen infected

parts of the plants from different localities will be collected,

labelled and brotight to laboratory in the polythene bag. The

conldla will be examined under the microscope for anamorph

characters In the absence of perithecia. Ihese characters include

colour of mycelium In older pustules (Rodlgin 1936 and Yarwood

1957); shape of conldla (Alcorn, 1968); presence and absence of

l£

fibrosin bodies (Homma, 1937; Clare, 1958, 1964; Kable et^ al.,

1963 and Jhooty, 1967) and type of germ tube (Hirata, 1942; 1955;

Kable et al,, 1963 and Zaracovitls, 1965) and conldial measure­

ments (Bouwens, 192A, 1927). At least 200 conidia will be

measured to determine the size i.e. length and width. The shape

of conidia will also be observed under microscope whether they

are ellipsoid, cylindrical, barrel, oblong,ovoid, lanceolate,

clavate, pyriform or rhomboid.

In order to ascertain the presence or absence of fibrosin

bodies in conidia collected from different localities, the conidia

will be mounted in 3? aq, KDH solution (Kable ej al., 1963)

and observed under microscope.

To determine the type of germ tube and appressoria, conidia

will be dusted over dry clean glass slides placed on glass

triangles in a sterilized petridish containing double distilled

water at the bottom. Which will be transferred to B.O.D.

incubator later, running at 17-22^C. After 24 hrs, conidia will

be stained In cotton blue and mounted in lactophenol to observed

the type of germ tube viz. simple and straight, simple and

fluxuous, branched, forked, forked and broadend, coiled, double,

broadend etc. and length viz. long, moderatly long, short; and

place of emergence of genntube on the conidia; and percentage

of germinating conidia. Type of appresoria will also be

determined whether they are lobed, unlobed or double.

47

Infected plant parts bearing perithecla will be preserved

in FAA for future studies 6'f characters which enable in acertain-

ing the identity of the pathogen. On mechanical rupturing the

number of asci will be examined per perithecium and number of

ascospores per ascus will also be taken into consideration, the

size of perithecia,asci and ascospores will also be determined.

For the size of ascospores 200 20 ascospores will be measured and

the average will be taken.

In order to maintain the inoculum for further studies,

seedlings of the respective hosts in the cotyledonous stage or

at 3-4 leaf stage grown in autoclaved soil (composition, 7s3;1

clay, sand and compostt respectively) contained in 25 cm clay

pots will be inoculated. For inoculation, dusting of conidia

will be done (Schmitt, 1955). The inoculated plants will be

kept in separate glass house chambers at 17-22°C in order to

avoid mixing of inoculum. Plants will be regularly examined for

the appearance and the development of disease.

4.3 HOST BMGR AND VARIETAL RESISTANCE> To study the host range

and varietal resistance, four-week-

old plants and seedlings (in the cotyledonous for 3-4 leaf stage)

of various plants belonging to families Brassicaceae and

Papilionaceae, different cultivars raised from surface sterilized

seeds grown in autoclaved soil will be inoculated with respective

causal organism by dusting. The studies will be carried out in

pots. These studies will be repeated with different isolates of

48

both powdery ndldews. For pot studies, inoculated plants will

be transferred to glasshouse and tenrperature will be recorded.

On the other hand, for field trials inoculated plants will be

transferred with entire soil to pits earlier dug at a distance

of 8-12 ft. Healthy seedlings will also be transferred in the

same way to serve as control. Temperature in field will be

recorded regularly.

After 20 days of inoculation, the intensity of disease

will be rated as given on earlier pages but over all rating will

be catagorised as under :

Resistant (R) » Powdery mildew fail to appear

Susceptible (S) • Powdery mildew appear

Similar inoculation tests will be made on detached leaves

or on leaf discs (Morrison, 1960, 1964). Leaves will be removed

from the upper most nodes of uninfected plants gomini in 25 cm.

clay pots. Leaf discs will be cut with 1 cm. diameter sterilized

cork borer and floated on water in petridishes. On the other

hand, detached leaves will be placed on glass triangles in a

petridish with petioles dipped in water. They will be inoculated

with conidia,

4.4 OBSERVATIONSg The disease intensity will be observed daily

for the two to three weeks after inoculations.

Throughout the studies perithecial production will also be

examined and the time taken for the appearance of perithecia will

49

also be recorded. Later p e r l t h e c i a , i f €uay, wil l be dissected

and examined for the presence of a sc i and ascospores. Ihe

following numerlcals r a t ing for disease In t ens i ty wil l be used

throughout s tud ies (Wheeler, 1969).

Grade Description Infecting ra t ing

Highly r e s i s t a n t Plants completely free from Infec t ion

Moderately r e s i s t a n t

Mycelium developing both on leaves and stem covering 26-509^ lea f area

Susceptible Many colonies appearing l a t e r coalescelng and covering 50-759< of leaf a r ea . Mycelium developing on st«n as wel l .

Highly suscept ib le Ent i re p lan t covered uniformly by mildew

P e r c ^ t a g e disease index wi l l be calculated as follows:

Percentage disease Index

Total numerical r a t ing

Total leaves x maximum ra t ing examined

X 100

In each case unlnoculated plants will serve as control.

50

4 . 5 SFEBCT OF TEMPERAIURE AND RELATIVE HUMIDITY ON INCUBATION

PERIOD t

To study the e f fec t of temperature and r e l a t i v e

humidity per ta in ing to the germination of conldia wil l be ca te ­

gorised under the following headings.

4.5.1 Effect of Ttnperaturei To determine the effect of

temperature on germination of

freshly formed conidia; they wi l l be dusted over a dry clean

g lass s l i d e and kept in incubation chamber. The assembly from

the Incubation chamber wi l l be t ransferred to incubators each

running a t - 5 , 5, 10, 17, 20, 25 and 30°C.

After 4, 8, 12, 36, 48, 60 and 72 h r s . of incubation,

s l i de s wi l l be examined under the microscope for germination

of conidia and percentage of germination wil l a l so be taken.

4.5»2 Effect of Relative humidity s Suppresaturated solutions

of following s a l t s wil l

be prepared to maintain the d i f fe ren t r e l a t i v e humidities

(Handbook of chemistry & physics , 1957).

Super saturated solut ion of

Sodium n i t r a t e Sodium ace ta te Ammonium sulphate Zinc sulphate Sodium h3^rogen phosphate Dis t i l l ed water

Relative humidity (%) a t 20 C

66 78 81 91 95

100

51

Siq)er-saturated solutions will be transferred to lower

chambers of siaail dessicators which would serve as humidity

chambers. Freshly developed conidia almost of the same size and

age will be uniformly dusted over the clean cover glass with the

help of glass-rod (Nair ai.aL.» 1962)* The entire assembly will

be kept at 20°C; after 4, 8, 12, 2A, 36, A8, 60 and 72 hrs. of

incubation, A e number of germinating conidia and that failed

to germinate will be counted and the percentage germination of

conidia will also be noted.

To study the effect of temperature and relative humidity

on disease development, surface sterilized seeds of susceptible

cultivars will be sown in autoclaved soil, contained in 25 cm

clay pots* The plants in cotyledonous stage will be inoculated

with conidia obtained from the original culture maintained in

glasshouse*

Fbr each combination of temperature and relative humidity

the plants will be regularly examined for the appearance of the

disease and the perithecia* Disease intensity will be recorded

after twenty days of inoculation on lower leaves and stem. A

maximum period of one month will be provided in each case to

ensure the production of perithecia, except in those where the

symptoms fail to appear*

In order to determine the role of ascospores in the

recurrence of disease, perithecia if obseirved, will be subjected

to the following treatments*

52

Leaf and stem portions containing perithecia will be

burried in soil for 27D days in small terylene bags. Ihese will

be kept in plastic tubes and transferred to different temperature

cabinets each running at -5, 5» 10, 17, 22, 25 and 30°C, these

will also be given a treatment of low and high temperature

alternately for varying periods (Arya and Ghemawat, 1954). After

every 30 days, leaf and stem samples will be taken out and the

number of aseospores per ascus and number of asci per perithecium

will be determined by mechanically rapturing the perithecia,

Thf aseospores will be tested for their germination on

the lines suggested for conidlal germination.

4,6 CHEMICAL OONTROL t The effect of fungicides will be

determined on the regerminatlon of

conidla as well as on the development of disease. The following

concentrations of the fungicides will be tested against the

disease 0.00001, 0,001, 0.1, 0.2, 0.5f and 1 percent. Ft)r

germination studies, technique as described on earlier pages

will be followed where conidia will be transferred in a crop of

required concentrations of fungicides. Plants of 4 leaf stage

will be inoculated with powdery mildew and treated with fungi­

cide as follows -

1) Plants will be inoculated with powdery mildew eight days

prior to the treatment with fungicides.

53

2) Plants will be first treated with fungicides and then

inoculated with mildew after eight days.

3) Plants will be treated with fungicides after symptoms of

powdery mildew developed.

In each groups, plants will be treated weekly, fortnightly

and monthly with different concentrations of the fungicides

applied both as soil drench and spray, Por the soil drench,

25 ml solution of the different concentrations of fungicides

will be incorporated to 250 gm soil. In each case the severity

of the disease will be recorded seven days after final treatment

as suggested by Munjal et al_. (1963) and Srivastava et al. (1971).

Disease severity will be graded on the bases of intensity of

powdery mildew as givei on page A9 • Percentage disease control

index will be calculated as follows.

Percentage disease index (PDI) in Disease control „ control - PDI in treatment x 1CX)

index PDC PDI in control

4.6.1 Eatlnation of Sugar j The samples of the infected plants

belonging to the family Brassicaceae

and Papilionaceae will be suspended in 3 ml warm 959 ethanol and

ground with mortar and pestle having some quartze sand and heated

in boiling water bath for 2 minute. The volume will be made upto

15 ml with warm ethanol and kept as such successively extracted

with 609 followed by 30% ethanol and finally with distilled water.

54

The siQser saturated solutions will be pooled together and the

volume made up to 30 ml with 95? ethanol and subsequently reduced

to 5 ml water bath (Nelson, 1944; Somogyi, 1945; Bell, 1955;

AOAC, 1960).

To one ml of 10 times diluted above allquate, 1 ml of

freshly prepared somogyl reag«it will be added. The mixture

will be heated for 12 minutes in a hot water bath. To this 1 ml

of arsenomely bate reagent will be added. The blue colour

developed will be diluted by the addition of 50 ml distilled

water for recording optical density at 494 nm, in spectrophoto­

meter. The concentration of reducing sugar will be calculated

using a standard curve with different concentration of glucose.

For estimation of total sugar, to 1 ml of diluted extract,

(extracted for reducing sugar) 1 ml of IN H2S0^ will be added.

The mixture will be heated at 49 C for 30 minutes to hydrolyse

non reducing sugar. After cooling, the acidity will be neutralised

with N NaOH. Optical density will be recorded at 495 nm. in

spectrophotometer and concentration of total sxigar will be

calculated using the above standard curve. There will be 5

replicates throughout the studies. The data will be subjected

to statistical analysis.

4.6,2 Bstination of Nitrogen> The aerial parts of the infected

and uninoculated plants will be

dried for 48 hrs. at SO 'c in an oven and later ground in mortar and

55

pestle for Nitrogen estimation for the former, the portions

showing powdery mildew sjnnptoms will be selected.

The dried and powdered sample (0,5 gm) will be taken into

a 500 ml KJeldahl digestion flask. Subsequently sodium sulphate

(20 gm) plus catalyst digestion mixture will be added. To

this 35 ral concentrated sulphuric acid will be poured by seissling

the flask and subjected to digestion till the organic matter is

digested making the solution clear. The digestion flask will

then be cooled to the point when crystals starts to form and

then 300 ml distilled water will be added.

Separately 25 ml of 4 percent boric acid will be pipetted

into a conical flask (500 ml) and 4 drops of bromocresal green

methyl red indicator solution will be added, A glass receiver

tube will be attached to the flask-neck so that bent end is

submerged in the boric acid solution contained in the flask.

The outer end of the tube will be attached to the condeisor.

The KJeldahl flask containing digested plant material will

be fixed on the distillation stand at 45° angle and connected

with the condenser. About 125 ml of AO percent NaOH will then

be poured and the distillation flask will be heated for 45

minutes followed by disconnection of the receiver flask. The

contents will than be filtrated against standared hydrochloric

acid.

56

4,7 PHYLLOPLANB FUNGI AND POWDERY MILIBVt The culture of common

saprophyte will be

grown on potato dextrose agar medium at 25°C. After 7-9 days

cultures will be ready for the use. Spore suspensions will be

prepared in sterile distilled water by scraping with inoculating

needle. The final concenlration of spores of saprophytes varied

from ^-8x10 spor«/ml.

A culture of powdery mildew pathogen will be maintained

on the susceptible host of family Brassicaceae and Papilionaceae

from which inoculum will be obtained for future studies. Freshly

formed conidia from such leaf samples will be collected and placed

in sterile distilled water. The final concentration will be made

nearly 2x10 conidia/ml.

For testing the effect of saprophytes on conidial germination

and germ tube length in vitro of Powdery mildew a 0,2 ml portion of

each saprophytic fungal spore suspaision mixed with powdery

mildew conidia will placed in cavity slides and incubated at 28°C

for 15 hrs. Perceitage of conidial germination and germ tube

length per conidium will be noted. Control will be maintained

without saprophyte-suspension.

For jta vivo study, plants of a highly susceptible host

variety will be grown in clay pots filled with sterilized soil

and compost. Third and fourth leaves will be rubbed gently with

wet cotton swabs before inoculation. Inoculum was applied with

57

an automizer, the saprophytic fungal suspension will be sprayed

20 hrs. before Inoculation with powdery mildew conidia.

The plants sprayed with distilled water and powdery mildew

Inoculum alone will be used as control. The plants will be

covered with polythene bags to ensure high humidity. Ihe disease

Intensity will be calculated as cited on page 49 . All the

data will be statistically analysed.

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