Identification and Control of Postharvest Fungal Contaminants of Sweet Potato (Ipomea batatas L.) In Lafia

Postharvest rot leads to huge yield losses of potato annually. A study was conducted to identify and control fungi causing postharvest tuber rot of sweet potato in Lafia. Infected tubers were collected from sales points in Lafia, and conveyed to the Plant Science Laboratory, Federal University of Lafia. Infected tissues were collected from the rotted tubers using a sterile scalpel, surface sterilised in 70% ethanol, and cultured for 3-5 days on PDA. Based on cultural and microscopic morphology, fungi isolated were identified under four genera, namely Mucor, Aspergillus, Candida, Fusarium. A total of 13 isolates were obtained, of which Aspergillus niger and Candida sp. had the highest number of isolates 4(30.77%), followed by Mucor racemosus 3(23.08) and Fusarium sp. 2(14.39). Pathogenicity test of the identified fungi showed that of the four identified species, Aspergillus niger produced tissue rot on the tubers, beginning from the first week (8.67 mm) to second week after inoculation (10.00 mm). Tuber rot produced by A. niger differed significantly from the other fungi as well as the uninoculated control (P≤0.05). Test of bioefficacy of aqueous and ethanolic extracts of Moringa oleifera in the control of A. niger showed that ethanolic extracts of Moringa oleifera produced higher and significantly different growth inhibition of A. niger compared to the extracts of Zingiber officinale (P<0.05). The study revealed that extracts of Moringa oleifera and Zingiber officenale hold promising prospects in the development of biofungicides for the management of postharvest tuber rot of sweet potato.