Abstract
Seeds of three hybrid rice varieties viz. Heera-1, Heera-2 and Heera-5 were collected from 15 different blocks of Supreme Seed Company limited along with one high yielding variety BRRI dhan-29 from 15 different farmers field at Mymensingh district. Longevity of seed borne fungal pathogens Bipolaris oryzae was studied during June, 2012 to June 2016. Moisture percentage, Purity percentage, 1000 seed weight, Germination percentage was recorded. The moisture content was 11.4 to 14.0%, pure seed was 94.5 to 99.0% and germination was 62 to 77%. The incidence of B. oryzae was 1.5-20%, 2-25% 1-21% and 13-37% in Heera-1, Heera-2 and Heera-5 hybrid rice seeds and BRRI dhan-29, respectively. The longevity of B. oryzae was observed till five years by blotter incubation methods, component plating techniques, seedling symptom test and growing on test. Both untreated and seeds treated with Vitaflo 200FF (carboxin and thiram) were kept in jute bag and polybag stored for five years under both normal and dehumidified condition. When the seed samples were stored under dehumidified condition, the highest incidence of B. oryzae was recorded in case of jute bag. Incidence of B. oryzae was recorded 14%, 18%, 15% and 28% after 60th months of storage, whereas initial incidence was recorded 20%, 25%, 21% and 37% on Heera-1, Heera-2, Heera-5 and BRRI dhan-29, respectively. Low germination percentage was recorded 77%, 70%, 75% and 62% when incidence of B. oryzae was observed 20%, 25%, 21% and 37% in-case of Heera-1, Heera-2, Heera-5 and BRRI dhan-29 rice seed, respectively. Vitaflo was effective in controlling seed-borne B. oryzae and provax followed by BAU fungicides and IPM bio pesticides. Consequently the germination percentage was high.