Fusarium bilaiae, a new cryptic species in the Fusarium fujikuroi complex associated with sunflower.

A Fusarium species associated with sunflower based on multilocus genealogy, morphological, physiological, ecological, mating type, and mycotoxin production data is formally described as the newly discovered species Fusarium bilaiae. The F. bilaiae strains formed a genealogically exclusive lineage within the African clade of the F. fujikuroi species complex. Comparison of morphological characteristics of F. bilaiae strains with those of the closely related F. phyllophilum strain NRRL 13617 revealed similarities in the main micromorphology of both species: production of numerous one-celled microconidia in false heads and short chains on monophialides and polyphialides and the absence of macroconidia and sporodochia. There was a slight but significant distinction between the two species when the strains were grown on different agar media, as well as in the shape and width of microconidia. Fusarium bilaiae strains isolated from symptomatic sunflower were not pathogenic to members of the Asteraceae tested; apparently, they live as saprophytes or endophytes in sunflower tissues. A difference between the strains of the two species in the production of mycotoxins was demonstrated with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis. On autoclaved rice, F. bilaiae did not produce fumonisins and beauvericin but produced moniliformin, whereas F. phyllophilum produced all these mycotoxins. A polymerase chain reaction (PCR) assay specific for mating type alleles identified F. bilaiae as a putative heterothallic species with MAT1-1 and MAT1-2 idiomorphs, but laboratory crosses were unsuccessful. Determining the area and host range of the new endophytic species F. bilaiae is a priority for future research.