Otusanya MO, Enikuomehin O, Popoola A, Adetunji M,Kehinde O, Latunde-Dada O and Amusa O
Evaluation of the Virulence of Three Isolates of Aspergillus niger van Tiegh. on Dioscorea Species
Three isolates of Aspergillus niger van Tiegh. from Nigerian yam Dioscorea rotundata were assessed for their virulence on Nigerian varieties of white, water and yellow/bitter Dioscorea species (Yams). The first isolate labelled An2 had been assessed in a previous study along with nine others from a range of geographical locations globally and hosts, for their virulence on Brazilian D. alata, Jamaican D. cayenensis, Nigerian and Ghanaian D. rotundata and French D. opposita. It was found to be most aggressive. The second isolate labelled An3 had also been assessed in a previous study on three improved clones from the International Institute of Tropical Agticulture, Ibadan, Gene Bank namely Dioscorea rotundata TDr 179, Dioscorea alata TDa 297 and Dioscorea esculenta (IITA). It was found to be equally virulent on all three clones. The third isolate labelled An5 was got ftom a rotting tuber in a yam lot from a Yam Market in Abeokuta, in the South West region of Nigeria. Isolates An2, An3 and An5 were assessed in this study on Dioscorea rotundata varieties Efuru and Apepe, Dioscorea alata variety Agbodo and Dioscorea. cayenensis variety Alo, varieties popular within the South Western region of Nigeria. An2 and An5 were similar in virulence on D. cayenensis variety Alo. The combined virulence of An2 and An5 were not significantly different (P=0.05) on D. rotundata variety Efuru and D. cayenensis variety Alo. An2, An3 and An5 were not significantly different in combined virulence on D. rotundata variety Apepe and D. alata variety Agbodo. A cluster analysis also revealed a close relationship among the three isolates. A molecular genetic analysis of isolates of A. niger from Nigerian Dioscorea varieties is necessary to confirm host specificity.
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