Molecular and pathogenicity characterization of Fusarium oxysporum species complex associated with Fusarium wilt of common bean in Brazil

Fusarium wilt in the common bean, caused mainly by the fungus Fusarium oxysporum f. sp. phaseoli (Fop), is considered one of the most important soil diseases for this crop. The aim of the present study was to identify the pathogen that causes Fusarium wilt in common bean through morphological and molecular characterization and pathogenicity studies in Fusarium isolates (UFV01, IACs 18,001, 18,002, 18,003, 19,009, 19,014, and 19,015) obtained from symptomatic plants in different common bean producing regions of Brazil. Morphocultural characterization was carried out in PDA and SNA media by evaluation of the color of the colony, the size and shape of the conidia, and conidiogenic cell type. Molecular characterization was conducted through construction of the phylogenetic tree with sequences of the partial translation elongation factor 1-alpha (TEF-1α), beta-tubulin (TUB2), RNA polymerase II, and calmodulin (CAL). Results showed that the isolates collected in different regions of Brazil, and in different periods of time, were identified as belonging to the species Fusarium nirenbergiae, F. fabacearum, and others unidentified and possibly of two new species of Fusarium, according to genealogical concordance phylogenetic species recognition criteria. The representative isolates of Fusarium oxysporum f. sp. phaseoli are most aggressive and comprised a monophyletic group separated from previously reported Fusarium oxysporum complex. Isolates of intermediate severity were identified as F. nirenbergiae and the isolates less aggressive as F. fabacearum.