TRANSMISSION OF Bipolaris sorokiniana FROM SEED TO PLANT TO SEED OF WHEAT

Abstract

The experiments were conducted in the Seed Health Laboratory and Experimental Field of Plant Pathology Department, Sher-e-Bangla Agricultural University, Dhaka- 1207, during the period from October 2008 to April 2009 to find out the transmission of Bipolaris sorokiniana from seed to plant to seed of wheat. There were altogether eight samples that used as treatment for different experiment which are as follows: TI = 0% seed infection (Bavistin treated @ 0.25% of seed weight); T2 = 0% seed infection (Provax treated @ 0.25% of seed weight); T3 = 0.1-10% seed infection; T4 = ]0.1-15% seed infection; T, = 15.1-20% seed infection; T6 = 20.1-25% seed infection; T7 = 25.1-40% seed infection and Ts = 50.1-55% seed infection. Disease severity showed significant variation at flag leaf stage, panicle initiation stage, flowering stage, milking stage and hard dough stage for without and with chemical control measure. For without chemical control measure, at flag leaf stage, in an average the lowest disease severity (0.09) was recorded in TI and the highest (0.45) in T8• At panicle initiation stage, in an average the lowest disease severity (0.15) was observed in TJ, whereas the highest (1.06) in T8. At flowering stage, in an average the lowest (0.43) was found in TI and T2, whereas the highest (1.32) was found in T8. At milking stage, in an average, the lowest disease severity (1.14) was recorded in TI and the highest (2.10) in T8. At hard dough stage, in an average the lowest disease severity was recorded in TI (2.30) and the highest in T8 (3.81). Considering plant height the longest plant (89.35 ern) was recorded in TI whereas the shortest (80.80 em) in T8. For grain yields per hectare the highest (3.67 tonnes) were recorded in TI while the lowest yield per hectare (2.25 tonnes) in T8. In field condition with chemical control measures at flag leaf stage, in an average the lowest disease severity (0.07) was recorded in TI and the highest (0.38) in T8. At panicle initiation stage, in an average thelowest disease severity (0.13) was observed in TI whereas the highest (0.92) was recorded in T8. At flowering stage, in an average the lowest (0.39) was recorded in TI while the highest (1.25) in Tg. At milking stage, in an average the lowest disease severity (0.97) was observed in T I and the highest (1.96) in T8. At hard dough stage, in an average the lowest disease severity (1.70) was recorded in TI and the highest (3.56) in T8. In respect of plant height, the longest plant (90,] 0 em) was recorded in TI while the shortest (81.37 ern) in Tg. In respect of grain yields per hectare the highest (3.71 tonnes) was recorded in TI while the lowest (2.29 tonnes) in Tg.There is a linear relationship between number of infected seedlings/rrr' and incidence of Bipolaris sorokiniana and the relationship was highly positive for without and with chemical control measures.