Microsatellite stability in the plant pathogen Botrytis cinerea after exposure to different selective pressures.

The stability of microsatellite markers was investigated in the spore-producing fungus Botrytis cinerea exposed to four growth conditions. This knowledge is essential in order to differentiate mutations from genetic exchanges or recombination in population genetics studies. It is also important when using strains from collections that need to be regularly propagated on medium. Successive spore generations of four isolates of the fungus were realised in plates on different agar media: a nutrient-rich medium, a nutrient-poor medium, a medium supplemented with the antibiotic pyrrolnitrin and a medium supplemented with the fungicide iprodione. The stability of nine microsatellite markers was studied by comparing the molecular pattern obtained between the wild type parent strains and the final generations obtained. The results showed that, despite the phenotypic changes observed in some generations, no changes were observed in the allele size at nine microsatellite loci whatever the selective pressure endured by the fungus. This is the first study that reveals long-term stability of microsatellite markers of a spore-producing fungus exposed to different stresses.