Genetic structure and fungicide sensitivity of Botrytis cinerea populations isolated from grapevine in northern Italy

Grey mould, caused by Botrytis cinerea, is a disease severely affecting grape production in northern Italy. However, little information is available on the variability of B. cinerea populations associated with grapevine. The mode of reproduction, sensitivity to fungicides, and for the first time in Italy, the genetic structure of B. cinerea populations isolated from grapevine in a northern Italian region are reported. Botrytis cinerea isolates (317) were completely genotyped for six microsatellite loci and characterized for the presence of the transposable elements Boty and Flipper, for the mating type and for resistance to cyprodinil, fludioxonil, boscalid and fenhexamid. All the isolates were found to belong to B. cinerea Group II, indicating the absence of B. pseudocinerea in the investigated areas. The populations possess a high genotypic diversity, different frequencies of transposable elements and a mixed mode of reproduction. At a regional level, B. cinerea populations belong to a large and interconnected pathogen population that includes the major grape-growing districts. The populations were generally sensitive to fungicides, with a low proportion (8%) of isolates resistant to cyprodinil, fludioxonil and boscalid. A small genetic distance was found between B. cinerea populations. However, the populations geographically isolated from the others by a mountain range showed a small but statistically significant genetic differentiation and a different pattern of fungicide resistance. The results show that northern Italian B. cinerea populations possess a high evolutionary potential and adaptive capacity.