Abstract
Selfed oospores were produced by A1 compatibility type isolates of Phytophthora infestans by pairing with A2 compatibility types of either P. infestans or P. drechsleri positioned on the opposite sides of a polycarbonate membrane. Nine single-oospore cultures were derived from one A1 isolate, and one single-oospore culture was derived from another A1 isolate. Segregation for some (but not all) observed characteristics was detected in the progeny. Two of nine progeny from one isolate were segregates for electrophoretic variants of the enzyme peptidase. Hyphae of all nine progeny grew more compactly than those of the parents. There was no segregation for compatibility type. Virulence of two progeny cultures was identical with that of the parent. The other progeny were either nonpathogenic or failed to sporulate in vitro.