Genetic Relationship among Fusarium oxysporum f. sp. melonis Vegetative Compatibility Groups and Their Relatedness to Other F. oxysporum formae speciales

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Fusarium wilt of melon is a destructive fungal disease throughout the world. In this study, the evolutionary relationships among isolates of different formae speciales of Fusarium oxysporum was examined, with a special emphasis on the forma specialis melonis. Bootstrapped maximum likelihood analysis of the elongation factor-1α (EF-1α) sequence was conducted on 16 Iranian and 11 foreign isolates of F. o. melonis that included representatives of different vegetative compatibility groups (VCGs 0130-0136). The tree inferred from the dataset resolved five evolutionary lineages that were correlated with the F. o. melonis VCGs, with the exception of VCGs 0130 and 0131, which could not be differentiated with EF-1α sequences. Furthermore, based on EF-1α sequences, specific associations were found between F. o. melonis VCGs and the other formae speciales whose sequences were obtained from the GenBank. Taken together, these results support a polyphyletic origin for F. o. melonis, meaning that the ability of this forma specialis to cause disease on melon has emerged multiple times.