Fusarium solani species complex isolates conspecific with Fusarium solani f. sp. cucurbitae race 2 from naturally infected human and plant tissue and environmental sources are equally virulent on plants, grow at 37 degrees C and are interfertile.

In a previous taxonomic study based on multilocus sequencing of Fusarium from clinical specimens and hospital environments, the most common lineage was Fusarium solani species complex group 1 (FSSC 1) which is conspecific with F. solani f. sp. cucurbitae race 2, a pathogen of cucurbit fruits. The aims of our study were to determine if clinical and environmental isolates of FSSC 1 are plant pathogens and members of the same biological species as cucurbit isolates, and to determine if all isolates can germinate, grow and sporulate at 37 degrees C. Isolates from the different sources did not differ in virulence on zucchini fruits. All FSSC 1 isolates were pathogenic and produced more rot than FSSC isolates from plant hosts other than cucurbits. Both mating types were found among isolates from each of the sources, and all isolates were sexually compatible with cucurbit isolates. All isolates germinated, grew and sporulated at 37 degrees C. This is the first report in which plant pathogenicity has been verified for a collection of human clinical isolates. Our data are consistent with the hypothesis that all FSSC 1 isolates, regardless of source, are a single biological species, equally virulent plant pathogens and tolerant of the human body temperature.