In vitro and In vivo antimicrobial potency of selected plant extracts in the control of postharvest rotcausing pathogens of yam tubers in storage


Gwa, V. I. Nwankiti, A. O.

Potency of Piper guineense, Zingiber officinale, Azadirachta indica, Carica papaya and Nicotiana tabacum on in vitro control of Curvularia eragrostide and in vivo control of postharvest rot-causing pathogens of yam tubers in storage was carried out. Rotted Ogoja and Ghini white yam tubers were collected from farmers’ barns in different locations in Lafia, Nigeria. Fungi organisms isolated from Ghini and Ogoja white yam tubers after four months included Botryodiplodia theobromae, Aspergillus flavus, A. niger, Fusarium moniliforme, F. oxysporum, Penicillium purpurogenum C. eragrostide and Colletotrichum sp. Only P. purpurogenum and C. eragrostide showed significant differences (P≤ 0.05) in mean percentage frequency of occurrence between the two cultivars. Pathogenicity test showed that all the isolated fungi were able to incite rot in the healthy yam tubers. The result revealed that Z. officinale, P. guineense, A. indica, C. papaya and N. tabacum exhibited more antifungal properties against C. eragrostide at higher concentrations (60 g/L and 90 g/L) than at lower concentration (30 g/L) throughout the period of incubation. Results also indicated that Z. officinale, P. guineense, A. indica and the synthetic chemical mancozeb were more efficacious in vitro. In vivo test using the most potent extracts; Z. officinale, P. guineense and A. indica and mancozeb showed that the extracts were effective against postharvest pathogens of yam at all the level of concentrations. Mean decay reduction index (DRI) of more than 0.6 indicated that the extracts as well as the chemical were able to inhibit the growth of pathogens on the yam tubers by more than 60% throughout the five months of storage. It is therefore recommended that extracts from these plants could be used to control postharvest pathogens of yam since they are ecofriendly, cheap and easily available.


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