BIOACTIVE POTENCY OF MEDICINAL PLANT EXTRACTS AND SYNTHETIC CHEMICAL ON POST-HARVEST ROT PATHOGENS OF WHITE YAM (Dioscorea rotundata Poir) TUBER CULTIVARS

Abstract

Diseases are the major challenges facing postharvest deterioration of yam tubers by pathogens in storage. The present study was carried out at Advanced Plant Pathology Laboratory, Federal University of Agriculture, Makurdi, Nigeria to study the bioactive potency of leaves of Azadirachta indica A. Juss, seeds of Piper guineense Schumach and rhizomes of Zingiber officinale Rosc with the synthetic fungicide Mancozeb used as a standard for comparison on the storability of Hembankwase, Pepa, Ogoja and Ghini white yam tuber cultivars. Tubers weighing 2kg were stored for a period of five months each year for two years from December, 2015 to April, 2016 and from December, 2016 to April, 2017 to determine the biological potency of the extracts using the Decay Reduction Index (DRI) method. Mean values obtained after five months of storage in 2016 indicated that the lowest and the highest mean Decay Reduction Index of 0.45 and 0.93 respectively were recorded on Hembankwase when A. indica was used. Similar results obtained in 2017 revealed that Z. officinale produced the lowest and highest mean value of 0.44 and 0.72 on Pepa and Ogoja respectively. Mean values recorded in the first year of storage showed significant difference (P≤0.05) between treatments. There were only significant differences (P≤0.05) when Mancozeb and Z. officinale were used in the second year. Differences in means for each treatment between first and second year of storage produced significant difference (P≤0.05). It is concluded that all the plant extracts and synthetic fungicide inhibited growth of pathogens in storage and should therefore be formulated for managing storage pathogens of yam.