Differential Rate of Dry Rot in &amp;lt;i&amp;gt;Dioscorea rotundata&amp;lt;/i&amp;gt; (White Yam) along the Tuber Length Due to Rot Causing Fungi

Apovughaye Taiga

doi:10.4236/aim.2012.24058

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.

Highlights

The word “yam” refers to the tuber of the botanical genus Dioscorea in the family Dioscoreaceae [1]
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

Summary

Introduction

The word “yam” refers to the tuber of the botanical genus Dioscorea in the family Dioscoreaceae [1]. Edible species of yam include D. rotundata Pour, D. cayennesis Lam; D. inspida Dennst; D. Cultivates three edible species namely: D. rotundata Pour (white yam), D. cayenensis Lam (yellow yam) and D. bulbifera L. Dioscorea rotundata is a swollen tuber, a liana, which contain about eighteen different amino acids in smaller quantities ad mainly carbohydrates [4], a fact that makes it a major source of carbohydrate for most people in the world, especially Africans and Asians. In the Niger-Delta of Nigeria, it is cooked into a delicacy known as “ukodo” (yam and pepper soup) that is usually used for marriage and burial ceremonies or as breakfast, during the cold season. The yam peelings form part of household waste use in feeding livestock [6]

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