MORPHOLOGICAL DIVERSITY IN CULTIVATION, CARBENDAZIM SENSITIVITY AND PATHOGENICITY OF TAPESIA-YALLUNDAE (ANAMORPH, PSEUDOCERCOSPORELLA-HERPOTRICHOIDES)

Three types of colonies(WH, WA, and RA) have been characterized among 2245 isolates of Pseudocercosporella helpotrichoides on the basis of colony growth rate and appearance (W, rapid growth and regular margin; R, slow growth and irregular margin) and of the shape of the majority of conidia (H, coiled; A, straight). Apothecia of Tapesia yallundae (anamorph: P. herpotrichoides) were produced on naturally infected stems of winter wheat and barley. Apothecia of an undetermined discomycete were occasionally observed. The progeny of more than 1700 ascospores from 72 apothecia of T, yallundae was distributed among the three types of colonies. These types remained stable through successive conidial and mycelial subcultures. All three colony types were sometimes obtained from a single apothecium. WH and WA were the most common, while RH was never observed. WA isolates were more often resistant than WH isolates to carbendazim. Inoculations of wheat and barley stems with ascospores of T. yallundae were unsuccessful, while inoculations with conidia or mycelium resulted in eyespot lesions. During equivalent periods, RA isolates were less virulent than WH and WA.