2-ALLELE HETEROTHALLISM IN TAPESIA-YALLUNDAE, THE TELEOMORPH OF THE CEREAL EYESPOT PATHOGEN PSEUDOCERCOSPORELLA-HERPOTRICHOIDES

A technique is described which permits in vitro sexual reproduction between compatible isolates of Tapesia yallundae. It involves the inoculation of isolates onto either barley straw nodal segments or a compost malt medium, followed by incubation for 12 weeks under white light at 10°C. Mating studies were made in which tester strains were crossed against a range of isolates of the W-pathotype of Pseudocercosporella herpotrichoides and pairwise crosses were made between a series of ascospore offspring from the same apothecium. These revealed that T. yallundae exhibits two-allele heterothallism, with the two mating types designated MAT1-1 and MAT1 -2. Increased phenotypic variation was observed as a result of recombination during the sexual cycle with the appearance of novel phenotypes, differing from those of the parental strains, amongst the progeny of a defined cross. Recombination was detected between mating type, resistance to the fungicide benomyl and randomly amplified polymorphic DNA (RAPD) markers. © 1993 Academic Press, Inc.