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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 \ •
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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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