CONTROL OF POSTHARVEST YAM (Discorea rotundata) ROT CAUSED BY FUNGI USING SAPROPHYTIC YEAST

Abstract

The potential of saprophytic yeasts (Cryptococcus neoformans, Rhodoturula rubra and Toruiopsis candida) isolated from the apparently healthy fruits of lime fruits, orange and tomatoes for the control of postharvest yam (Discorea rotundata) rot caused by fungi was investigated. Treatments comprising three isolated pathogenic fungi (Aspergillus niger, Aspergillus flavus and Penicillium notatum) from rotten yams, each paired was set up in dual culture with one of the potential antagonists (saprophytic yeasts). The extent of rot reduction was evaluated by calculating the mean percentage (%) inhibition of the pathogens by antagonists. Pathogenicity test showed that A. niger, A. flavus and P. notatum induced rot in healthy yam tubers after fourteen days of inoculation at room temperature (28±2oC) with A. niger being the most virulent. The growth reduction or inhibition of A. niger, A. flavus and P. notatum was highest and significantly different (P<0.05) in C. neoformans (51.1, 51.7 and 50.0) and least in R. rubra (5.6, 4.9 and 6.4) respectively. The three biological antagonists could be used to control the rot of postharvest yam tubers. However, the field efficacies still need to be further investigated.