Isolation and Identification of Pathogens Associated with Postharvest White Yam (Dioscorea rotundata L) Tuber Rot

Tubers of white yam varieties (Gbangu, Dan-Anacha, Hembakwase, Pepa and Amula) showing symptoms of rot were collected from five farms in five local government areas of Zone “A” Senatorial District of Benue State, Nigeria and assessed for fungal and bacteria contents. Eight isolates (five fungi and three bacteria) were isolated from the samples and identified using morphological, cultural, physiological and biochemical tests as well as standard identification guide. The fungal isolates identified were Aspergillus niger, Botryodioplodia theobromae, Zygosaccharomyces bailli, Zygosaccharomyces rouxil and Myrothecium verrucaria, while Klebsiella oxytoca, Serratia marcescens and Pseudomonas aeruginosa were the bacterial isolates identified.

Pathogenicity tests revealed that all the organisms induced rots in the apparently healthy white yam tubers after seven days of inoculation. The result also showed a significant difference (p < 0.05) in the average rot measurements among the different yam varieties with Aspergillus niger being the most prevalent; Botryodioplodia theobromae, the most virulent, while Hembakwase was the most susceptible white yam variety in the study area.