Abstract
The segregation and distribution patterns of the mating types of Cochliobolus miyabeanus were determined. The segregation ratio of the two types A, B, and C, D was about 1:1 in monoascosporic isolates and 35:49 in monoconidial isolates from field. In field, both mating types were distributed almost equally and moreover co-existence (sympatric distribution) of these types in the same localities or on the same rice plant was demonstrated. Over 60% of both monoconidial and monoascosporic isolates of the fungus were hermaphroditic. The remainder showed a loss of female character(s) in mating tests. Crosses between isolates of H. oryzae from Japan and U.S.A. were attempted. Fertile ascocarps were produced with the correct combinations. The identity of this fungus from both countries was confirmed by the formation of the perfect state.
