Isolation and characterization of microsatellite loci in the wheat pathogen Mycosphaerella graminicola

Microsatellites are becoming increasingly important in the study of population structure. To date, however, very few single-locus microsatellite markers have been isolated in fungi. In this paper we report the isolation of nine single-locus microsatellite markers from the fungal pathogen Mycosphaerella graminicola. M. graminicola (Fuckel) J. Shoert. (anamorph Septoria tritici Rob. ex Desm.), is one of the most important foliar diseases of wheat in the northern hemisphere. The pathogen colonizes plant tissue as haploid hyphae and then reproduces both asexually and sexually. Field infections by M. graminicola are initiated by wind-borne, sexual ascospores early in the season and the disease them progresses as a consequence of repeated infections by asexual conidia. The use of molecular technology has provided insights into the population biology of M. graminicola. Using restriction fragment length polymorphism (RFLP), McDonald & Martinez (1990) found that a high level of genetic variability exists within North American S. tritici populations. Interestingly, these studies have also indicated that sexual reproduction probably plays a much more important role than was previously thought. Population studies involving RFLPs are time-consuming to perform. Alternatively, microsatellites have been shown to be simple to use, and can be highly polymorphic between individuals within a population. The nine primer sets described here will be used to study the population dynamics of S. tritici, in order to develop new pathogen-management strategies, and to answer questions concerning the extent to which sexual and asexual reproduction affect population structure.