Espécies do complexo Fusarium oxysporum associadas à murcha de fusarium do feijoeiro

Abstract

Fusarium wilt is a disease of common bean, causing losses in production in Brazil and other countries. The causal agent is known in the literature as Fusarium oxysporum f. sp. phaseoli. But recently, based on the phylogenetic analyses of several barcode regions, members of the Fusarium oxysporum species complex – FOSC have been described as phylogenetic species. In this study we investigated which species of the FOSC can induce symptoms of wilt in common bean and cowpea, and if there is an correlation between the concept of formae speciales and the proposed phylogenetic species. Twenty two isolates with morphological characteristics of F. oxysporum, obtained from the main production areas in Brazil, were evaluated by means of phylogenetic analysis of sequences of the TEF barcode region and pathogenicity tests in common bean and cowpea. Fusarium grosmichelii, F. gossypinum, F. kalimantanense, F. nirenbergiae, F. triseptatum, F. callistephi and still two phylogenetic lineages, not named so far, induced typical symptoms of wilt in all inoculated plants. No specific markers for each of those species could be recognized. Those species have already been reported as causal agents of Fusarium wilt in other crops. Indeed, this is the first study evaluating the etiology of Fusarium wilt in common bean and cowpea under the aspect of redefinition of the species within the FOSC. We bring strong evidence that the forma specialis phaseoli is actually represented by several phylogenetic species. Results presented here are contributing to the redefinition of the etiological agents of this disease, but will also give relevant support to breading programs, aiming the selection of cultivars with durable resistance to this disease.