09-08-2013, 04:17 PM
Variability studies and management of Bipolaris sorokiniana, incitants of spot blotch of wheat in Jammu sub-tropics
ABSTRACT
A extensive survey was conducted during cropping season Rabi 2009-11 for assess the Average infection index (AIDX) and collection of disease leaf sample for the study of morphological and pathogenic variability among the isolates of Bipolaris sorokiniana causing spot blotch of wheat in Jammu sub-tropics. The average infection index ranged from10.0-38.50 per cent during the both the year of survey. Ten isolates of Bipolaris sorokiniana isolated from different area of Jammu division were characterized and grouped into 3 groups on the basis of colony colour, conidial morphology, pathogenic nature and culture characteristics such as black, grayish black and brown colour with profusely sporulated and suppressed type of growth to fluffy and less sporulated type. The average size of conidia ranged from 38.5–63.8 μm x 10.9–24.6 μm with slightly curved, brown to olivaceaous brown with 2–10 septa. Among the isolates, maximum pathogenic virulence was observed in BS-5, exhibiting susceptible (S) type of infection response (IRs) on three genotypes i.e. Agra Local, PBW- 343 and HD-2733. The isolate BS-10 was the least virulent as all the genotype showed R type of infection response (IRs) except Agra Local which exhibited susceptible type of infection response. Under field studies, thirteen wheat cultivars evaluated against Bipolaris sorokiniana, under artificial epiphytotic condition and exhibited that DBW 16, DBW 17 and RSP 561 were found resistant whereas, other cultivars showing moderate to susceptible type of response in field condition. Moreover, propiconazole at 0.1 per cent proved most effective with highest per cent disease control (87.70-84.72%) followed by tebuconazole (85.40-82.50 %), and triadimefon (71.50-72.22 %), respectively, during 2009-10 and 2010-11 cropping season. Trichoderma sp. was found least effective in managing the spot blotch of wheat. While in case of per cent increase in yield per hectare, propiconazole proved most effective at 0.1 per cent concentration, exhibited highest per cent increase in yield followed by tebuconazole and triadimefon, respectively.