Effect of silkworm litter on collar rot disease development in sporangia inoculation of Phytophthora nicotianae var. parasitica on roselle

Soil amended with organic matter is the one of more promising and most frequently used methods of attaining biological control of soil-borne plant pathogens. This method had not toxic substance residues, which affected to men, animals, food and environment. Organic matter could improve physical property of soil for growth well of plants, soil fauna and soil microorganisms. This paper, soil amended with silkworm litter was used to control Phytophthora nicotianae var. parasitica which caused to collar rot disease of roselle. Induction to sporangia for pathogen inoculum, decreased disease development of roselle plants, affected to the number of survival Phytophthora propagules in the infested soil, and hypersensitivity reaction on a tissue of roselle grown in the infested soil were proceeded in this sutdy. The results found that sporangia induction by cultured active growth mycelia of Phytophthora into V8+20 percent CaCO3 liquid media. Phytophthora liquid cultures were incubated under fluorescence light with 3000 lux of light intensity and taken time for 16 hours at 25-28 deg C on incubation room for 1 month. Sporangia were produced at a tip of mycelia. These sporangia were harvested by mycelia filtration with a sterilized cloth-sheets from culture liquid media and washing mycelia with sterilized water at 3 times. Sporangia were separated from mycelia by blender with sterilized water at 25 deg C for 3 minutes and then mycelia were excluded from sporangia by filtration with sterilized cloth-sheet. Sporangia were collected by centrifugation with a velocity at 1,500 g on 15 deg C temperature for 10 minutes. Supernatant of sporangia solution was excluded, pellet on the bottom of tube was washes with sterilized water and then was centrifuged with the same velocity again. Single sporangia solution were adjusted to a concentration at 15.72*104 cell/ml and were inoculated into soil with volume at 50 ml/a fresh weight of soil at 200 g. Collar rot disease development in roselle plants were decresed when inoculated with a infested soil (sporangia) into the amended soil with 3 percent silkworm litter. Furthermore, hypersensitivity reaction was only found on roselle tissue grown in the amended soil. However the number of survival Phytophthora propagules were more than in the infested soil treatment and the amended soil also inhibited a germination of roselle seedlings.