Journal of Plant Pathology & Microbiology

Abstract

Susceptibility of White Yam (Dioscorea rotundata Poir) Tuber to Rot Fungi and Control with Extracts of Zingiber officinale Rosc. Azadirachta indica A. Juss. and Piper guineense Schumach

Gwa VI and Richard IB

Isolation, identification and control of fungal pathogens of Ogoja yam tubers collected from Benue and Nasarawa States, Nigeria were studied between December, 2015 and April, 2017. Fungi identified from the rotted samples were: Aspergillus flavus, A. niger, A. ochraceus, Botryodiplodia theobromae, Curvularia eragrostide, Colletotrichum sp, Fusarium moniliforme, F. oxysporum, F. solani, Penicillium expensum, Pestalotia sp. and P. purpurogenum. Fungi with the highest mean frequency of occurrence were A. niger (21.84%), B. theobromae (19.10%), A. flavus (16.84%) and F. oxysporum (15.49%) while the least were Colletotrichum sp. (1.36%) and P. expansum (1.49%). Tests of pathogenicity carried out on the head and tail regions of the Ogoja yam tubers showed that the head was more susceptible than the tail and all the fungi elicited rot when tested on healthy tubers of yam. Fungi with the highest rot depth both at the head and tail regions were A. niger (23.00 mm, 27.33 mm), A. flavus (16.33 mm, 21.00 mm) and B. theobromae (9.33 mm, 11.33 mm) while the least virulent were Colletotrichum sp. (5.00 mm, 6.66 mm) and P. purpurogenum (4.00 mm, 7.66 mm), respectively. Extract application of leaves of Carica papaya Lam. (pawpaw), rhizomes of Zingiber officinale Rosc. (Ginger), Piper guineense Schumach. (Black peper), Azadirachta indica A. Juss. (neem), and leaves of Nicotiana tabacum Linn. (Tobacco) on tubers before storing for five months showed high level of potency in controlling rot pathogens. These plant extracts could therefore, be applied on tubers to prolong their shelf life.