Grape black rot, caused by the homothallic ascomycete Phyllosticta ampelicida, is a disease originating from North America and is widespread in Europe. To investigate population structure and epidemics of this pathogen, we developed 11 microsatellite markers. A multiplex PCR assay was used to amplify genomic DNA from environmental samples including mummified berries and foliar lesions, and from fungal cultures. Environmental samples were collected from five countries (Switzerland, France, Germany, Luxembourg and the USA), and consisted of 64 different genotypes. Five additional genotypes were identified from pure cultures isolated in Switzerland and Germany. The allele rarefaction approach indicated that French vineyards in the region of Bordeaux displayed the greatest mean allelic richness, probably related to the fact that France is the country where the disease was first reported outside North America, in 1885. Our results also suggest the absence of links between the species/cultivar of Vitis hosts and the infecting P. ampelicida genotypes. This is the first report of development of microsatellite markers and their deployment for population studies of P. ampelicida.
Guignardia bidwellii; SSR; population genetics; population structure