Detection of Botrytis cinerea field isolates with multiple fungicide resistance from table grape in Sicily

• Botrytis cinerea population showed a variable sensitivity level to botryticides.
• About 10% of field isolates possessed resistance at least to two or more fungicides.
• Different isolates were simultaneously resistant to four different fungicide classes.
• No isolates were found resistant to fenexamid and fludioxonil.
• Management of resistance in vineyard is needed to delay multiple fungicide breakdown.

During 2009–2013, 302 single-spore isolates of Botrytis cinerea were collected from vineyards located in the most important site of table grape production in Sicily, recognized by the European Community as Protected Geographical Indication (PGI) ‘Mazzarrone grape’. In preliminary studies, all isolates were tested in vitro for their sensitivity to six fungicides belonging to the following groups: benzimidazoles, dicarboximides, anilinopyrimidines, succinate dehydrogenase inhibitors, hydroxyanilides and phenylpyrroles. In these tests, 45.7% of the isolates were found to be resistant to at least one fungicide. Specific resistance to pyrimethanil was found in 30.8% of the isolates, whereas 13.9, 10.3 and 7.6% of the isolates exhibited resistance to carbendazim, iprodione and boscalid, respectively. No isolates resistant to fenhexamid and fludioxonil were detected within our dataset of B. cinerea isolates. However, 30 B. cinerea isolates possessed multiple resistance to two or more fungicides. In detail, 8 isolates were simultaneously resistant to four fungicides, whereas 5 and 17 isolates were resistant to three and two fungicides, respectively. For boscalid, 11/23 of isolates showing in vitro resistance possessed a mutation at the SdhB gene, whereas all isolates resistant to carbendazim and iprodione possessed mutations at β-tubulin and BcOS1 histidine kinase genes, respectively. Accordingly, these fungicides failed to control gray mould infections caused by resistant or reduced sensitivity isolates on grape berries and grapevine leaves whereas the sensitive isolates were effectively managed by all fungicides applied at label rates. This study represents the first report of B. cinerea field isolates resistant and/or with simultaneous resistance to several botryticides from table grape vineyards in Sicily. Therefore, current strategies for fungicide resistance management of B. cinerea could be negatively affected in future.