Control of fungi causing post-harvest rot in white yam (Dioscorea cayenensis) using selected plant extracts

Abstract

Post-harvest yam tuber rot is a fungal disease affecting the storage of white yam [Dioscorea cayenensis subsp. rotundata (Poir.) J. Miège], and this poses a significant threat to global food security. There is a need to develop suitable measures to mitigate the threat and ensure the availability of rot-free tubers to consumers. This study aimed to isolate and identify the fungi responsible for post-harvest rot in white yam sourced from selected markets in Lagos, Nigeria, and the efficacy of various plant extracts in treating these fungi. Isolated fungal strains were subjected to pathogenicity tests to assess for virulence. The virulent strains were identified using molecular techniques. Ethyl acetate and n-hexane extracts of Pseudocedrela kotschyi, Parkia biglobosa, and Mezoneuron benthamianum were screened against the isolates using the agar well diffusion method. Six fungi were isolated from the diseased yam tubers, of which two were virulent and capable of inducing rot in healthy yam tubers after 14 days of inoculation. These were identified as Penicillium oxalicum strain LBCCN_YS_A3 (OQ550968) and Aspegillus niger strain LBCCN_YS_A8 (OQ550969). Of all plant extracts tested, P. biglobosa had the highest antifungal effects on the growth of the fungal strains. Therefore, this plant extract is a sustainable alternative to the inorganic fungicides for mitigating post-harvest spoilage of white yam tuber.