Historical Introgression of the Downy Mildew Resistance Gene <i>Rpv12</i> from the Asian Species <i>Vitis amurensis</i> into Grapevine Varieties

<div><p>The Amur grape (<i>Vitis amurensis</i> Rupr.) thrives naturally in cool climates of Northeast Asia. Resistance against the introduced pathogen <i>Plasmopara viticola</i> is common among wild ecotypes that were propagated from Manchuria into Chinese vineyards or collected by Soviet botanists in Siberia, and used for the introgression of resistance into wine grapes (<i>Vitis vinifera</i> L.). A QTL analysis revealed a dominant gene <i>Rpv12</i> that explained 79% of the phenotypic variance for downy mildew resistance and was inherited independently of other resistance genes. A Mendelian component of resistance–a hypersensitive response in leaves challenged with <i>P. viticola</i>–was mapped in an interval of 0.2 cM containing an array of coiled-coil NB-LRR genes on chromosome 14. We sequenced 10-kb genic regions in the <i>Rpv12⁺</i> haplotype and identified polymorphisms in 12 varieties of <i>V. vinifera</i> using next-generation sequencing. The combination of two SNPs in single-copy genes flanking the NB-LRR cluster distinguished the resistant haplotype from all others found in 200 accessions of <i>V. vinifera</i>, <i>V. amurensis</i>, and <i>V. amurensis</i> x <i>V. vinifera</i> crosses. The <i>Rpv12⁺</i> haplotype is shared by 15 varieties, the most ancestral of which are the century-old ‘Zarja severa’ and ‘Michurinets’. Before this knowledge, the chromosome segment around <i>Rpv12⁺</i> became introgressed, shortened, and pyramided with another downy mildew resistance gene from North American grapevines (<i>Rpv3</i>) only by phenotypic selection. <i>Rpv12⁺</i> has an additive effect with <i>Rpv3⁺</i> to protect vines against natural infections, and confers foliar resistance to strains that are virulent on <i>Rpv3⁺</i> plants.</p>