A study was undertaken to determine the prevalence of black point and percentages of germination, moisture content and different fungi associated with wheat seeds during storage in different types of container. Seeds of a widely cultivated variety Kanchan were stored in five types of containers viz., 'dole'(bamboo made), earthen pitcher, tin container, polyethylene bag and refrigerator (10 0 C) for ten months at room temperature. Samples were taken at monthly interval beginning from the month of April (prior to storage). The seed moisture content and black point severity were found highest in dole resulting in the lowest percentage of seed germination. The highest germination percentage was observed under storage in refrigerator followed by polyethylene bag, tin container and earthen pitcher. The moisture content and black point infection increased and seed germination decreased with the increase of storage period. Prior to storage in April, the seed germination was 95%, which decreased to about 75% at the end often months of storage (in January). Various fungal flora associated with wheat seeds differed in their prevalence depending on the length of storage period and types of container used for storage. The population of field fungi viz., Alternaria alternata, Aiternaria triticina, Bipolaris sorokiniana, Cladosporium cladosporioides, Curvularia lunata, Epicoccum purpurascens and Fusarium spp. decreased while that of storage fungi viz., Aspergillus, Chaetomium, Nigrospora, Penicillium and Rhizopus increased with the progress of storage period.

Performance of potato seed tubers of first, second, third, fourth, and fifth generations were evaluated against PVY and PLRV. Potato plants grown from first generation seed tubers were free from PVY infection. Incidence of the virus was the minimal at second generation, which increased afterwards steadily by third, fourth, and fifth generations. Incidence of PLRV was minimal at first generation. It increased gradually with the advancement of generation seed tubers showing the highest incidence at fifth generation. The highest plant growth and tuber yield were recorded at second generation, which was followed by third, fourth, and fifth generations. The highest reduction in plant height, tuber number, and tuber yield were recorded in 5th generation due to infection of PVY and PLRV. Keywords: Generation evaluation; PVY; PLRV; growth; yield; potato DOI: 10.3329/bjar.v35i1.5865Bangladesh J. Agril. Res. 35(1) : 37-50, March 2010

An experiment was conducted to find out variation in isolated Rhizoctonia solani based on radial mycelial growth and sclerotial production. Five isolates of Rhizoctonia solani representing five clusters group were selected and were grown at different levels of temperature and pH on potato dextrose agar (PDA). It was observed that optimum temperature and pH for growth and scierotial production varied among the isolates. The rates of growth and sclerotial formation were not uniform at the same levels of the two growth factors. The maximum mycelial growth of all isolates was found at 30°C. At 35°C, only GAZ-9 and GAZ-18 showed initiation of growth, but the rate was very slow. The optimum temperature for sclerotial production of the isolates GAZ-9, JES-16, GAZ-18 SYL-26 was 30°C and for the isolate DIN-8 was 25°C. The optimum pH for maximum radial growth was 6 for DIN-8 and 7 for other four isolates. The maximum number of sclerotia was produced by DIN-8, GAZ-9, and SYL-30 at pH 8, 4, and 7, respectively. The optimum pH for sclerotia formation in JES-16 and GAZ-18 was pH 6.

Bactericidal effect was investigated by chemicals against potato soft rot bacteria in vitro and in storage. The chemicals were acetic acid, boric acid, bleaching powder, lactic acid, calcium hydroxide, calcium chloride, potassium chloride and sodium hypo-chloride. Among eight chemicals only three chemicals viz. acetic acid, boric acid and bleaching powder showed bactericidal activity against potato soft rot bacteria Pectobacterium carotovorum subsp. carotovorum (E. carotovora subsp. carotovora) P-138 in vitro. Based on the results of in vitro experiment three chemicals, acetic acid, boric acid and bleaching powder were used to control soft rot disease of potato in storage. Fresh potato tubers were dipped in 0.2% solution/suspensions of acetic acid, boric acid and bleaching powder for 30 min. Then soft rot bacteria Pectobacterium carotovorum subsp. carotovorum P-138 was inoculated on potato. Finally potatoes were stored for 22 weeks in net bags in sterilized condition. All the three chemicals significantly decreased the infection rate, loss in weight and increased percentage of disease reduction (PDR) of potato. Boric acid was the most effective in controlling the soft rot disease of potato in storage followed by acetic acid and bleaching powder. So these chemicals may be used for seed purpose storage of potato tubers for year round storage at farmer's level.