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Poster: Epidemiology: Pathogen Dispersal


Specific TaqMan qPCR and a PvABC qPCR assays for monitoring airborne sporangia of Plasmopara viticola f. sp. riparia, aestivalis and vinifera.
O. CARISSE (1), M. Tremblay (2), A. Lefebvre (3) (1) Agriculture and AgriFood Canada, Canada; (2) Agriculture and Agroalimentaire Canada, Canada; (3) Agriculture and AgriFood Canada, Canada

Grape downy mildew (Plasmopara viticola) is among the most important grapevine diseases in eastern Canada. Recently, five new cryptic formae speciales of P. viticola from wild and cultivated Vitis species were described. In Eastern Canada, only P. viticola f.sp. riparia (clade A) and P. viticola f.sp. aestivalis (clade B) have been detected. As part of a biovigilance network aiming at tracking new pathogens and new genotypes, molecular assays for simultaneous quantification of sporangia of clade A and B and detection of clade C (P. viticola f. sp. vinifera) from air samples were developed. The assays are a specific triplex TaqMan qPCR and a PvABC qPCR developed from sequence alignments of internal transcribed spacer 1 and 2 (ITS1-2) DNA regions for P. viticola clade A, B, C and other closely related species. These essays were used to study the temporal and spatial occurrence of these genotypes in two vineyards. At one site, almost exclusively (99%) clade A was found while at the other site it was mostly (83%) clade B. Hence the genotype A was found at both sites, however, it was observed for the first time in early July at one site and in early June at the other site. The impact of these genotypes on grape downy mildew development is under study. Using these new tools, it will be possible to acquire knowledge on aerobiology and spatio-temporal distribution of genotypes A and B and to monitor clade C not present in Eastern Canada, but detected in north-east of USA.