First report of southern blight caused by Sclerotium rolfsii on soybeans in Nigeria

Southern blight of soyabeans caused by S. [Corticium] rolfsii, was observed for the first time in Nigeria, in field nurseries at Bukuru, near Jos in the Plateau State, in 1989. Over 40% of plants in plots of the cultivar TGx 1025-12E were blighted 2 weeks after the plots had been rogued to eliminate plants infected by C. rolfsii. Symptoms included yellowing, browning and wilting of entire plants. A white mat of fungal mycelia and numerous tan to brown spherical sclerotia were present on stem bases, leaf debris and the soil surface around infected plants. C. rolfsii was isolated by plating washed and surfaced-disinfested stem segments of symptomatic plants and sclerotia obtained from the field on acidified potato-dextrose agar at 25°C. Plants of TGx 1025-12E were inoculated in the greenhouse with the isolate of C. rolfsii; typical symptoms were observed and the pathogen was reisolated. Yields from the diseased plants averaged 683 kg/ha, a decrease of 59% from yields of TGx 1025-12E in the same field, under the same management practices, during 1987 and 1988