Patho-physical Characteristic Studies of Varieties of Dioscorea Rotundata (yam) in Storage

Abstract

Storage rot at the ‘top’, ‘middle’ and ‘bottom’ portions of four (4) varieties of Dioscorea rotundata (‘Giwa’, ‘Suba’, ‘Kpako’ and ‘Dindiyam’) cultivated in Niger State, Nigeria was investigated on the bases of tissue hardness and moisture content, to establish their comparative rotting subjectivity. Yam tubers stored in an empty room on a polythene material for 30 days were divided along the length into three equal portion of ‘top’, ‘middle’ and ‘bottom’; which were further subdivided into many pieces in search for symptom(s) of infection. The rotting was more than twice as high in the bottom (54.2%) as the middle (22.9%) and the top (22.9%). Isolated fungi from the infections were Aspergillus parasiticus and Fusarium accuminatum. A. parasiticus was most pathogenic on ‘Suba’ variety (13.69±0.75mm) and least on Giwa (11.09±0.48mm), and it is a more potent pathogen of rotting than F. accuminatum, which showed a rotting range of 2.22±0.32 to 3.49±0.46mm. Bottom portions of the yam varieties were most subjective to pathogenicity. In all the varieties, except Dindiyam, the bottom portion contained significantly (P> 0.05) higher moisture than the middle or the top. All portions of the yam varieties had significantly different (P> 0.05) hardness; ranging from bottom to top. Pathogenicity of A. parasiticus is probably favoured with the optimal moisture and softness of the bottom portion.