ABSTRACT The susceptibility of different regions in Dioscorea rotundata (white yam) tuber to rot infecting fungi was investigated. Isolation was made from the periphery of the rotted tuber tissues, followed by a pathogenicity test and identification of isolates. Three fungi associated with D. rotundata (white yam) were isolated; they include Penicillium oxalicum, Aspergillus niger and Rhizopus stolonifer. Each of the isolates from pure cultures were inoculated on the head, middle and tail regions of healthy yam tubers. The three fungi were found to be pathogenic at different rates at the head, middle and tail ends of the yam tuber respectively. The head region was less susceptible to the three fungi with the following rot depths (P. oxalicum 25 mma, A. niger 18.2 mma and R. stolenifer 12.7 mmb). Rot depth in the middle region was (P. oxalicum 15 mma, A. niger 10.6 mma and R. stolenifer 8.8 mmb). While the tail region of the yam tuber recorded rot depth of (P. oxalicum 32.0 mma, A. niger 26.4 mma and R. stolenifer 20.8 mmb) respectively. Generally, the tail region of D. rotundata was more susceptible to fungal attack and the rot recorded in the tail region was significantly different from rot at the middle and the head. It was recommended that yam tubers should be stacked with their head on the ground to reduce incidence of rotting in stock-piled yam tubers.
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