Comparative Assessment of Antimicrobial Potency of Some Selected Plant Extracts Against Seed Borne Pathogens of Germinating Yam Setts

Abstract

Comparatives studies of the potency of seeds of Piper guineense Schumach. (Black peper), rhizomes of Zingiber officinale Rosc. (Ginger), leaves of Azadirachta indica A. Juss. (neem), leaves of Carica papaya Lam. (pawpaw) and leaves of Nicotiana tabacum Linn. (Tobacco) were tested against growth of F. solani in vitro. Pathogenicity tests were carried out on Botryodiplodia theobromae, Aspergillus flavus, A. niger, A. ochraceus, Fusarium moniliforme, F. oxysporum, F. solani, Curvularia eragrostide and Colletotrichum sp which confirmed that all the fungi organisms elicited rot on healthy Hembankwase cultivar. In vitro tests of the different plant extracts on F. solani at 30 g/L, 60 g/L and 90 g/L revealed that all the extracts were fungitoxic. However, P. guineense and Z. officinale were more potent compared with A. indica, C. papaya and N. tabacum. The synthetic fungicide mancozeb consistently gave higher inhibition of 100% throughout the period of incubation in spite of the concentration used. Application of these extracts in the control of seed borne pathogens of yam during germination of yam setts also proved effective in both years with decay reduction index (DRI) ranging from 0.22 in Hembankwase to 0.88 in Pepa using Z. officinale in 2015 compared with 0.66 in Hembankwase and 0.77 in Pepa using P. guineense in 2016. Mean decay reduction index showed that all the extracts were more potent on Pepa cultivar than Hembankwase. It is therefore, concluded that plant extracts could be used as alternative to chemicals in controlling fungal pathogens of yam both in vitro and in vivo.