Evidence for homothallism and vegetative compatibility in southern Diaporthe phaseolorum

Abstract
Twenty-nine vegetative compatibility groups (vcgs) were identified among 297 isolates of the fungus causing soybean stem canker in the southeastern United States (southern Diaporthe phaseolorum). Of the isolates characterized, 79% were from one of the vcgs described (group 1). Barrage zones formed between isolates from different vcgs when grown on potato dextrose agar, and also formed, but not always distinctly, on cornmeal agar, Czapek-Dox agar, lima bean agar, and malt agar; barrages did not form on Sach's agar or water agar. Two types of evidence suggested that southern D. phaseolorum is homothallic. Perithecia and viable ascospores were produced by single ascospore isolates, and ascospores produced by mass isolates were always of the same compatibility group as the parental mass isolate.