Sicily: gray mould may have become fungicides resistant

Gray mould, caused by Botrytis cinerea, is one of the most serious fungal disease of table grape (Vitis vinifera L.) worldwide. This pathogen is responsible for heavy losses in one of the most important Italian areas for the table grape production (Mazzarrone - Sicily) an area that has been recognized by the European Community with the 'Protected Geographical Indication' (PGI, Reg. CE 617/2003) label. Gray mould represents the most serious threat for this typical production since grapes harvesting is usually performed up to late December when the climatic conditions occurring in vineyards are favorable for disease development.

From 2009 to 2013, Italian scientists from University of Catania collected 302 single-spore isolates of B. cinerea from vineyards located in Mazzarrone grape district. Scientists evaluated within B. cinerea isolates in vitro sensitivity to boscalid, carbendazim, fenhexamid, fludioxonil, iprodione and pyrimethanil and their relative in vivo performance using detached grape berry and grapevine leaf assays, identified point mutations in field isolates resistant to different fungicides, and investigated the presence of isolates with multiple fungicide resistance within a population of B. cinerea (click here to download a table).

Sensitivity tests showed that 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 B. cinerea isolates tested. About 10% of B. cinerea field isolates possessed multiple resistance at least to two or more fungicides. Different isolates resulted simultaneously resistant to four different fungicides classes. 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 b-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.

Scientists conclude that the use of benzimidazoles, dicarboximides, anilinopyrimidines and the SDHI boscalid within Sicilian districts should be performed in alternation or in mixtures with botryticides having a different action way and showing a low risk of resistance development such as phenylpyrroles and hydroxyanilides. T

The results indicate that, by continuous selection of multi-resistant isolates, chemical control of gray mould in vineyards will become increasingly difficult in this important Italian area of table grape production. Thus, careful monitoring of sensitivity and multiple resistance among botryticides over time will be crucial in managing fungicide resistance.

Study is available online since July 28th 2015 at:
http://www.sciencedirect.com/science/article/pii/S026121941530065X
and it is published on Crop Protection journal.

Source: Anna Panebianco, Ivana Castello, Gabriella Cirvilleri, Giancarlo Perrone, Filomena Epifani, Massimo Ferrara, Giancarlo Polizzi, Dale R. Walters, Alessandro Vitale, 'Detection of Botrytis cinerea field isolates with multiple fungicide resistance from table grape in Sicily', November 2015, Crop Protection, Vol. 77, pages 65-73.

Contacts:
Alessandro Vitale
Department of Agriculture, Food and Environment, University of Catania
Catania 95123, Italy
Email: alevital@unict.it