EFFECTIVENESS DIFFERENCES OF CARBOXYLIC ACID AMIDES FUNGICIDES TOWARDS PLASMOPARA VITICOLA POPULATIONS: IN VIVO TESTS AND MOLECULAR STUDIES ON PVCESA3 GENE

Plasmopara viticola is controlled by fungicides with different modes of action,including \ncarboxylic acid amides (CAAs). Dimethomorph was the first CAA introduced in 1988, \nfollowed by iprovalicarb, flumorph, benthiavalicarb, mandipropamid, valifenalate and latest \npyrimorph in 2010 \n. The mode of action of CAAs is linked to the inhibition of cellulose synthesis \nin the Oomycete plant pathogens. The mutations conferring CAA resistance in Plasmopara \nviticola located on the CesA3 gene are G1105S and G1105V.The aim of this work was to \nevaluate the activity of dimethomorph and mandipropamid on P. viticola populations. \nBioassays on leaf discs, and on seedlings were carried out. In leaf discs assay, CAAs tested on \nItalian populations showed different level of activity and in particular dimethomorph showed \nlower levels of EC95 and this behavior was also confirmed from seedling tests. \nAll CAA resistant populations carried the G1105S/V mutations, which were detected by RFLPPCR \nand qPCR . In order to gain a better understanding of the different behavior and to define \nthe possible different resistant mechanism, molecular modelling and docking studies are \nongoing.