Mating relationships between isolates of Phaeosphaeria nodorum, (anamorph Stagonospora nodorum) from geographical locations

Mating types of Phaeosphaeria nodorum isolates (from North Africa, North America, Australia, Europe and Near East) were determined in laboratory conditions. Although both mating types were found, MAT1-1 and MAT1-2 were not evenly distributed among the isolates. Sexual compatibility pairings with standard mating type testers revealed that 56 of 101 isolates could be assigned to MAT1-1 and 5 to MAT1-2. Although the teleomorph occurred in different countries, the two mating types were observed only among isolates collected from France, Great Britain, Germany and Morocco. For Morocco, where no P. nodorum pseudothecia have been reported, this is the first report of the existence of the two opposite mating types. The remaining 40 isolates could not be designated to a specific mating type. However, in 17 crosses, pseudothecial initials or sterile pseudothecia were observed on wheat straw after two months. The implications of the predominance of one mating type are discussed.