RESUMO
We constructed a two-locus database, comprising partial translation elongation factor (EF-1alpha) gene sequences and nearly full-length sequences of the nuclear ribosomal intergenic spacer region (IGS rDNA) for 850 isolates spanning the phylogenetic breadth of the Fusarium oxysporum species complex (FOSC). Of the 850 isolates typed, 101 EF-1alpha, 203 IGS rDNA, and 256 two-locus sequence types (STs) were differentiated. Analysis of the combined dataset suggests that two-thirds of the STs might be associated with a single host plant. This analysis also revealed that the 26 STs associated with human mycoses were genetically diverse, including several which appear to be nosocomial in origin. A congruence analysis, comparing partial EF-1alpha and IGS rDNA bootstrap consensus, identified a significant number of conflicting relationships dispersed throughout the bipartitions, suggesting that some of the IGS rDNA sequences may be non-orthologous. We also evaluated enniatin, fumonisin and moniliformin mycotoxin production in vitro within a phylogenetic framework.
Assuntos
DNA Espaçador Ribossômico/genética , Bases de Dados de Ácidos Nucleicos , Fusarium/classificação , Fusarium/genética , Micoses/microbiologia , Fator 1 de Elongação de Peptídeos/genética , Doenças das Plantas/microbiologia , Sequência de Bases , Sequência Conservada , Infecção Hospitalar/microbiologia , Impressões Digitais de DNA , DNA Fúngico/genética , DNA Ribossômico/genética , Evolução Molecular , Fusarium/metabolismo , Humanos , Técnicas de Tipagem Micológica , Micotoxinas/biossíntese , Micotoxinas/genética , Filogenia , Plantas/microbiologia , RNA Ribossômico 18S/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
Species limits were investigated within the Fusarium graminearum clade (Fg clade) through phylogenetic analyses of DNA sequences from portions of 11 nuclear genes including the mating-type (MAT) locus. Nine phylogenetically distinct species were resolved within the Fg clade, and they all possess contiguous MAT1-1 and MAT1-2 idiomorphs consistent with a homothallic reproductive mode. In contrast, only one of the two MAT idiomorphs was found in five other species, four of which were putatively asexual, and the other was heterothallic. Molecular evolutionary analyses indicate the MAT genes are under strong purifying selection and that they are functionally constrained, even in species for which a sexual state is unknown. The phylogeny supports a monophyletic and apomorphic origin of homothallism within this clade. Morphological analyses demonstrate that a combination of conidial characters could be used to differentiate three species and three species pairs. Species rank is formally proposed for the eight unnamed species within the Fg clade using fixed nucleotide characters.
