Preliminary Evidence for Two Debilitating Cytoplasmic Agents in a Strain ofEndothia parasiticafrom Western Michigan

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Abstract
Single-conidial isolates (SC1) of EP-60, a highly debilitated, dsRNA-containing strain [double strand] of E. parasitica from western Michigan, segregated into 3 types. Type A was indistinguishable from EP-60 in cultural characteristics, pathogenicity, and fruiting capacity in American chestnut [Castanea dentata] and in its pattern of SCI segregation. Type B had cultural characteristics unlike type A or typical E. parasitica, was weakly pathogenic, and produced a few stromata, perithecia and ascospores typical of E. parasitica in American chestnut. It yielded only type B and C SCI. Type C was indistinguishable from typical E. parasitica. It produced typical perithecia and ascopores in the field and in the laboratory, when matted with a type a mating type tester, and it yielded only type C SCI. When type A, B, and C isolates were paired on agar, type A and B characteristics were rapidly transferred to type C, and type A characteristics were slowly transmitted to type B. These results indicate that EP-60 has a genetic background typical of E. parasitica, with mating type A, and suggest that it contains 2 debilitating cytoplsamic agents. Type B isolates appear to represent the genetic background of EP-60 when it contains one of the agents and type A this background when it contains both agents. A 4th isolate type, with only the 2nd agent, was not found.