Tolerance level of Alternaria sesami and the effect of seed infection on yield of sesame in Kenya

Field plots of sesame (Sesamum indicum) with six different levels of seed i nfection with Alternaria sesami were monitored for Alternaria leaf spot sev erity at Kibwezi, eastern Kenya. The aim of the study was to determine the effect of seed transmission of the pathogen on yield and tolerance level of the fungus in sesame seed. Increase in percentage leaf area diseased and p ercentage defoliation fitted the Gompertz model more closely than the logis tic model. Areas under disease progress curves (AUDPC), infection and defol iation rates varied among the six infection levels. Disease severity increa sed with increase in seed infection and was least and most severe in plots established with seeds with 0 and 8% infection levels respectively. Yields ranged from 234.9 to 300.1 kg ha(-1) compared with 312.5 kg ha(-1) for the control, and losses due to seed infection ranged from 4 % to 25%. Disease s everity was negatively correlated with seed yield, 1000-seed weight and see ds per capsule. Alternaria leaf spot severity had a major effect on the see d weight component of yield. Tolerance level of A. sesami in sesame seed wa s determined to be less than 2%.