Variability studies in bipolaris sorokiniana (Sacc.) shoem causing leaf blight of wheat
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Date
2005
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CCSHAU
Abstract
Bipolaris sorokiniana (Sacc.) Shoem (Teleomorph: Cochliobolus sativus
(Ito and Kuribayashi, Drechs ex. Dastur) causes leaf blight of wheat. A total of
13 isolates of B. sorokiniana obtained from blighted leaf samples collected from
different agroclimatic zones of India (NWPZ-Pant Nagar, Karnal, Hisar and
Ludhiana; NEPZ-Faizabad, Dharwad, Coochbehar and Samastipur; CZ-Pune and
Vijapur and NHZ-Almora). Morphological, pathological and genetic variability
were studied. Nine characters were studied at morphological level of study of
pathogen viz. spore and sporophore size, sporulation, per cent germination,
colony growth, septation, color of cytoplasm, shape of spore, spore and
sporophere color and nuclear staining. Two type of colors of spores viz. light
brown and dark brown were observed whereas, sporophores showed different
types of colour viz. light brown, dark brown, dark olivaceous, light to darkbrown
and grayish brown. Maximum septa in spores were found in isolate BS-6, while
the maximum sporophore septa were in BS-2 and BS-8. Similarly four types of
cytoplasm colors i.e. light blue, blue, greenish blue and brown were observed
whereas three types of shape of spores were observed namely elliptical, oblong
and slightly curved. Fastest colony growth was observed in isolate BS-11
whereas, BS-5 was the slowest growing. Maximum sporulation was observed in
BS-13 while minimum in BS-5. Among all spores and sporopores, the longest
were in isoalate BS-8 whereas, shortest in BS-2. Isolate BS-2 showed maximum
spore germination whereas, minimum in BS-1. All the spores represented high
degree of variability when nuclear staining was done with ethidium bromide (2,
7-diamino-9 phenyl phenanthridium bromide). The pathological variability was
studied at five characters viz. incubation period, infection response (IR), number
of lesions on flag-2 leaf, necrotic area development and terminal disease
severity. Differential infection response (susceptible, moderately susceptible,
moderately resistant and resistant) were observed at seedling stage on differential
set of five genotypes viz. Sonalika, GW322, HD2733, PBW-34 (d) and
HPW184. Maximum virulence was observed in isolate BS-2 in respect to four
pathological characters namely incubation period, number of lesions on flag-2
leaf, necrotic area development and terminal disease severity. Out of 20 primers,
only two i.e. OPAA-15 and OPAA-16 produced the band of all 13 isolates of B.
sorokiniana isolates and a high degree of variability was detected. The isolate
BS-5 made a separate group when cluster analysis was done. Isolate BS-9 and
BS-11 made another group and rest were in third group.