Antifungal Potential of Selected Plant Extracts on Pathogenic Post-Harvest Fungi Causing Tuber Rot in Ipomoea batatas (L.) Lam. (Sweet Potato)

Abstract

Post-harvest deterioration limits the effective processing and utilization of Ipomoea batatas L. (sweet potato). This study identified the fungi associated with post-harvest tuber rot of I. batatas from selected markets in Lagos, Nigeria, and the antifungal efficacy of selected plant extracts in treating this disease. Sweet potato tubers collected from local markets in Iyana-Iba and Okokomaiko were observed for rot diseases. Isolation, identification, and characterization of fungi and pathogenicity tests were carried out on the specimens collected from the markets. Five fungi were isolated from the diseased tuber, they were identified as Aspergillus aculeatus, Aspergillus flavus, Fusarium sp., Lasiodiplodia theobromae and Penicillium oxalicum. The pathogenicity test revealed that only A. aculeatus and P. oxalicum induced rot in healthy sweet potato tubers 14 days after inoculation, with P. oxalicum being the most virulent. The molecular analysis confirmed the identity of the two virulent isolates as Penicillium oxalicum and Aspergillus aculeatus. The extracts of Parkia biglobosa, Pseudocedrela kotschyi, and Mezoneuron benthamianum exhibited antifungal potency on the fungi isolates. P. kotschyi against A. aculeatus at 20mg/ml had the highest inhibitory zone of 18.17±0.76 for n-hexane extract while against P. oxalicum at the same concentration, the highest inhibitory zone of 25.00±1.00 was recorded. Hence, the recommendation of the use of these plant extracts product as a substitute to synthetic antifungal agents for controlling the growth of fungi causing post-harvest tuber rot of I batatas.