Abstract
The Amur grape (Vitis amurensis Rupr.) thrives naturally in cool climates of Northeast Asia. Resistance against the introduced pathogen Plasmopara viticola 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 (Vitis vinifera L.). A QTL analysis revealed a dominant gene Rpv12 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 P. viticola–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 Rpv12+ haplotype and identified polymorphisms in 12 varieties of V. vinifera 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 V. vinifera, V. amurensis, and V. amurensis x V. vinifera crosses. The Rpv12+ 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 Rpv12+ became introgressed, shortened, and pyramided with another downy mildew resistance gene from North American grapevines (Rpv3) only by phenotypic selection. Rpv12+ has an additive effect with Rpv3+ to protect vines against natural infections, and confers foliar resistance to strains that are virulent on Rpv3+ plants.
Highlights
The Amur grape (Vitis amurensis Rupr.) is native to cool climates of the Far East, including Siberia, China, Korea, and Japan [1]
We report on another resistance gene donated by V. amurensis to existing grape varieties
The Rpv12 locus coincides with a cluster of CC-NB-LRR genes on chromosome 14 and the inheritance of the resistant haplotype is associated with a localised hypersensitive response (HR) in leaves challenged with P. viticola
Summary
The Amur grape (Vitis amurensis Rupr.) is native to cool climates of the Far East, including Siberia, China, Korea, and Japan [1]. A few forms of what is believed to be pure V. amurensis with domestication traits–i.e. relatively large berries and hermaphroditic flowers–are grown in northeastern China [2] or reported in literature [3,4] This species is a reservoir of important viticultural traits that are absent from the germplasm of the European wine grape Vitis vinifera. Several haplotypes of the most documented North American resistance gene for downy mildew (Rpv3) have been introgressed since the mid 1800s into many varieties [8]. Rpv is the first mapped resistance gene against downy mildew that was introgressed from V. amurensis into grapevine varieties of Western Europe [12]. Many resistant varieties such as Severnyi, Rondo, and Solaris–selected in Russia, Czechoslovakia, and Germany– share Rpv by descent [12] but many others are derived from V. amurensis and show high levels of resistance in the absence of known resistance genes
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