Assessment of Effects of Postharvest Tuber Rot of Yam (Dioscorea spp L (Poir) ) on Proximate Composition and Control of Isolated Pathogens with Some Plant Extracts and Synthetic Fungicide in Awka South, Nigeria

Investigation was carried out to assess the effects of post-harvest tuber rot and the proximate composition and control of isolated pathogen with some plant extract and synthetic fungicide in Awka. The experiment was conducted in the Pathology Laboratory of Department of Crop Science and Horticulture, Nnamdi Azikiwe University, Awka. The varieties used include; white yam (Dioscorea rotundata), water yam (D. alata) and yellow yam (D. cayensis). The infected portion of the yams was sliced into  smaller portions of 0.4cm diameter and surface sterilized in 5% methylated spirit and distilled water for 3 minutes and was rinsed twice. It was later incubated in acidified PDA for four days. The fungi growth observed was isolated and sub-cultured two times to get a pure culture which was later used for identification. In-vitro experiment was carried out to test the effect of two plant extracts Aloe vera and Lime (Citrus aurantifolia) and a synthetic fungicide (Aldrex T.). This experiment was laid out in a factorial in Complete Randomized Design (CRD) and replicated three times. Proximate analysis of the infected and uninfected yam tubers was also carried out. The result of isolation and identification of the rot pathogens from the infected yam tuber showed that the rot causing organism was only Aspergillus flavus. Plant extracts and synthetic fungicide (Aldrex T) were both effective in reducing the radial growth of the fungi pathogen. The highest percentage radial growth inhibition 75.00% was obtained in both A. vera and synthetic fungicide (Aldrex T) while the least (30.06%)was obtained in C. aurantifolia plant extract.   Uninfected yam tubers had higher proximate values except in Moisture and Ash.  It is therefore recommended that plant extracts tested in this study should be used as alternative to synthetic fungicide since they showed similar effectiveness in reducing yam tuber rot in Awka. Yam tubers should be properly harvested and handled to avoid injury to avoid spoilage and deterioration in their nutrient composition as well as loss of their market value.