Antifungal Potency of Some Plant Extracts in the Control of White Yam (Dioscorea rotundata poir) Tuber Rot

Studies were carried out on the effect of some hot aqueous plant extracts using Piper guineense, Zingiber officinale, Azadiracta indica, Carica papaya and Nicotiana tabacum using three concentrations (30, 60 and 90g/l) along with a chemical fungicide (mancozeb) at three concentrations (4, 8 and 12g/l) amended in potato dextrose agar (PDA) on in vitro control of B. theobromae, causal organism of yam tuber rot. The research was conducted at Advanced Plant Pathology Laboratory, Federal University of Agriculture and Madurai, Nigeria. The pathogen was isolated and identified from rotted white yam tubers. Pathogen city test carried out confirm the organism to be associated with rot in yam tubers. The study showed that B. theobromae was able to induce rot on the healthy looking yam tubers. The result also revealed that N. tabacum was the least potent extract at 30g/l, 60 g/l and 90g/l with mean percentage value of 19.11%, 26.76% and 38.16% respectively while the most effective extract was P. guineense with mean value of 81.88%, 84.80% and 92.86% at 30g/l, 60g/l and 90g/l respectively. The result also revealed that all the plant extracts were able to inhibit the mycelial of the pathogen with concentration III having the highest inhibitory effect in all the extracts. There was a 100% inhibition when mancozeb was used irrespective of the level of concentrations and duration of incubation. Treatment of the test plant extracts significantly (P≤0.05) reduced mycelial growth of B. theobromae in vitro. The study showed that all the plant extracts showed high potency in the control of B. theobromae at varying degrees. These plant extracts can therefore be prepared and used against rot causing fungi of white yam tubers in storage.

Keywords: Antifungal; Plant extracts; Yam; Botryodiplodia theobromae; Inhibition; Storage