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Amusa, A.N.; Ikotun, T. & Bankole, J.O. Résumé Une enquete sur les pathogenes de taches foliaires d'ignames cultives, le Dioscorea alata et D. rotundata, etait effectuee au Nigeria. Le Calletotrichum glaeasporioride etait l'organisme predominant de part sa frequence d'apparition de 45,6% et 42,7% en 1992 et 1993, respectivement. Les autres champignons associes au taches foliaires d'ignames etaient notamment Curvuloria eragrostides, Pestalatia macrotrichia, Scleratium rolfsii, Rhizoctania solani, Colletotrichum graminicola, C lindemuthianum, Batryadiplodia theobromae, Curvuleria pallanscen, Fusarium oxysparum et Macrophorria sp. Cependant, au point de vue de test de pathogenecite, il n'y avait que C glacosporioides, C graminicala, S. rolfsii, R. solani, eragrostides et P. macratrichum qui etaient capable d'induire des lesions necrotiques sur les feuilles de D. alata et D. rotundata; ce qui suggere que seuls ces organismes etaient les pathogenes primaires de taches foliaires d'ignames. Mots Clés Dioscorea alata, D. rotundata, champignon, pathogenecite

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Survey of Leaf Spot-causing Microorganisms on Yams Amusa, A.N.; Ikotun, T. & Bankole, J.O. Abstract A survey of leaf-spot pathogens of cultivated Dioscorea alata and D. rotundata in Nigeria was conducted. Colletotrichum gloeosporioide was the predominant organism judging by its frequencies of occurrence of 45.6% and 42.7% in 1992 and 1993, respectively. Other fungi found associated with yam leaf-spot included Curvuloria eragrostides, Pestalotia macrotrichia, Sclerotium rolfsii, Rhizoctonia solani, Colletotrichum graminicola, C. lindemuthianum, Botryodiplodia theobromae, Curvuleria pallanscen, Fusarium oxysporum and Macrophorria sp. In pathogenicity test, however, only C. glocosporioides, C. graminicola, S. rolfsii, R. solani, eragrostides and P. macrotrichum were able to induce necrotic lesions on leaves of both D. alata and D. rotundata, suggesting that only these organisms were the primary leaf-spot pathogens of yams. Keywords Diascorea alata, D. rotundata, fungi, pathogenicity

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