Studies on Biological Control of Postharvest Rot in Yams (Dioscorea spp.) using Trichoderma viride

From in vitro and in vivo screening tests for antagonism by isolates of Trichoderma against postharvest pathogens of yams "Dioscorea spp[#\ an isolate of Trichoderma viride Pers[ ex S[F[ Gray was selected as the most promising candidate for the biocontrol of postharvest rot of yams[ Inoculation of white yam "Dioscorea rotundata Poir[# with conidiaspores of T[ viride and subsequent storage of the tubers under the ambient environment conditions of a traditional yam barn\ resulted in a drastic reduction in the frequency of occurrence of the normal tuber surface myco~ora over a 3!month "December April# storage period[ Trichoderma viride on the other hand\ maintained a high frequency of occurrence during the same period[ Furthermore\ whereas up to 41[9) rot was found among groups of tubers that were arti_cially inoculated with the postharvest pathogens of yams\ Asper`illus ni`er Van Tiegh[\ Botryodiplodia theobromae Pat[ or Penicillium oxalicum Currie and Thom\ and also the group that was not inoculated with any organism "control#\ among groups of tubers that were inoculated with T[ viride the rot was either totally suppressed or only a low percentage of rot occurred[ The signi_cance of the _ndings is dis! cussed in relation to yam storage especially by farmers with limited resources[