Effect of flooding on the viability and pathogenicity of sclerotia ofSclerotium rolfsiiin Malaysian soil∗

Abstract

Abstract Sclerotial viability of Sclerotium rolfsii the seedling blight and collar rot pathogen of chilli, decreased rapidly with time of submerging in flooded field soil. Viability was reduced to 10% 9 days after submerging. No reduction was observed in sclerotia submerged in non‐sterilized tap water. Loss of viability resulted in complete loss of pathogenicity. Nongerminated sclerotia became soft and broke easily. Maceration of cortical cells was common. A bacteria‐like organism was consistently associated with the ruptured and macerated sclerotia. In glasshouse studies, soil flooded at a high temperature decreased the viability of the sclerotia; this was reflected in a reduced incidence of seedling blight and collar rot on chilli seedlings. The incidence of seedling blight was recorded as 43–7% in the non‐flooded soil, 10.2% in flooded soil and 12.3% in the planter that had received an application of Brassicol. However, incidence of collar rot was 25.3% and 28.1 % in the flooded and fungicide‐amended soils respectively and 58.1% in the non‐flooded pots. It is concluded that satisfactory control of seedling blight and collar rot of chilli can be achieved by flooding.