Relative susceptibility of sweet potato varieties and clones to major diseases in Central Uganda

Sweet potato is ranked as the third most important food staple in Uganda after cassava and banana. However, Alternaria leaf spot and stem blight and sweet potato virus disease (SPVD) are reportedly causing considerable yield reduction on this crop. Most commercial varieties especially in the entire lake Victoria crescent region are reportedly susceptible to the diseases. This study was initiated to; 1)assess the levels of resistance of selected clones and varieties to sweet potato virus disease and Alternaria leaf and stem blight, 2) determine the yield potential of elite sweet potato clones under natural infection by SPVD and Alternaria. There was significant variation (P=0.05) in the reaction of the clones to the two diseases. The incidence of Alternaria disease ranged from 4.4-40.6%. Clones 18-66, 23-60, 39-66, NKA-18, TZ-360, 23-40, Sowola, TZ-898, TZ-80 and TZ-1927 were ranked resistant. The moderately resistant included; TZ-3181, TZ-309, TZ-check, TZ-2009, and NKA-18. Susceptible clones were NKA-21, NKA-check and TZ-2074. Clones TZ-2074 and TZ-3181 had the highest AUDPC values for SPVD and clone 18-66 the lowest. NKA-21 had the highest AUDPC for Alternaria `leaf and stem blight.