Bipolaris species associated with foliar diseases on invasive and weedy grasses in Florida.

Invasive and weedy plants proliferate in disturbed areas, including the margins of agricultural fields where they can be alternative hosts and reservoirs of crop pathogens. Research on plant pathogens focuses on economically important plants, whereas pathogens of weedy and invasive grasses are generally less well characterized. Bipolaris species have the potential to cause disease on many plant species and are common pathogens of grasses and crops in the family Poaceae. This study aimed to identify Bipolaris species causing foliar lesions on common weedy and invasive grasses in disturbed and natural areas in four counties in Florida. Isolation of characteristic Bipolaris conidia from sampled grasses resulted in 22 isolates. Maximum likelihood phylogenetic analysis of internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GPDH) gene sequences from these isolates identified four Bipolaris and one Curvularia species. B. yamadae was the most common species recovered, followed by B. sorokiniana, B. cynodontis, and B. zeae. To determine whether the Bipolaris isolates were potential crop pathogens, we tested their pathogenicity on seedlings of wheat cultivar "Jamestown." All Bipolaris isolates tested caused moderate to severe disease. Our results indicate that invasive and weedy grasses support populations of Bipolaris pathogens of crops. Knowledge of pathogen natural history can inform management of existing and emerging crop diseases.