Multiple geographic breakdown events of the Rpv1/Rpv3.1 pyramided resistance in grapevine by Plasmopara viticola.

In 2024, three vineyard sites located within a radius of 40 km in southeastern France, each planted with Artaban, a grapevine variety carrying pyramided resistance (Rpv1 and Rpv3.1), exhibited severe downy mildew symptoms following climatic conditions highly conducive to disease development. Twenty-one Plasmopara viticola isolates were collected from these vineyards and, after monosporangium isolation, tested under controlled conditions on a panel of susceptible and resistant grapevine varieties to assess their virulence. Among the 21 tested field strains, 19 overcame Rpv3.1 mediated resistance, 10 overcame Rpv1 alone, and four genetically distinct strains from two separate vineyards were overcoming the pyramided Rpv1-Rpv3.1 combination. The genetic characterization of the strains suggests that this adaptation likely resulted from convergent evolution. To our knowledge, these represent the first documented cases in Europe of a breakdown in resistance conferred by Rpv1, whether deployed alone or in combination with Rpv3.1.