Botryodiplodia theobromae stem rot of cassava and methods of selecting varieties for resistance
1984
Otim-Nape, G.W. (Serere Agricultural Research Station, Soroti (Uganda). National Root Crops Improvement Programme)
After Botryodiplodia stem rot of cassava (CSR) was observed for the first time in Africa (in Uganda) in 1981, a series of experiments were initiated to determine the effects of stem maturation on infection; to identify suitable methods of screening for field resistance; and to screen varieties for sources of resistance to the disease. Four cassava varieties were planted in a split plot experiment, with varieties as the main plots and heights as the subplots. At maturity, the stems were harvested, and the number of B. theobromae postules counted. The number of postules was directly related to maturity of the stem. Two methods of screening for resistance were compared: scoring for rot severity on a 0-5 scale and counting rot postules per unit area. Scoring for severity was deemed most suitable for resistance screening, and counting of postules had advantages for epidemiological and pathogenicity studies. In screening tests of eight families, four: IYT (OP) 1979; PYT (OP) 1980; 30555 (OP) 1979; and 30572 (OP) 1980 exhibited some resistance to the disease.
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