Biology and genetics of grape powdery mildew, Erysiphe necator
Development of genetic markers in E. necator for population studies
Population genetic analyses of E. necator in Italy have revealed a puzzling contradiction. E. necator is a heterothallic fungus, i.e., mating only occurs between individuals of opposite mating type. In theory, this type of mating system should promote outcrossing and a randomly mating population structure if populations are derived from sexual spores (ascospores). However, in one population we studied in Italy where the fungus does not overwinter asexually as mycelium in dormant buds—such that all inoculum in the spring derives from overwintering ascospores—the population structure deviated markedly from random mating. This contradiction has stimulated our interest in the mating system of this fungus in nature. To accomplish this goal, we must first develop a more robust set of genetic markers, particularly codominant markers such as microsatellites. Once codominant markers are available, we will be able to estimate how much inbreeding is occurring and whether E. necator is truly outcrossing in nature.
This project is being done in collaboration with Paolo Cortesi (University of Milan, Italy).
Relevant recent publications:
--Cortesi, P., Mazzoleni, A., Pizzatti, C., and Milgroom, M. G. 2005. Genetic similarity of flag shoot and ascospore subpopulations of Erysiphe necator in Italy. Appl. Environ. Microbiol. 71: 7788-7791. [PubMed]
--Cortesi, P., Ottaviani, M.-P., Milgroom, M. G. 2004. Spatial and genetic analysis of a flag shoot subpopulation of Erysiphe necator. Phythopathology 94:544-550. [pdf]