Abstract
Cultivated grapevines (Vitis vinifera) lack resistance to powdery mildew (PM) with few exceptions. Resistance to this pathogen within V. vinifera has been reported in earlier studies and identified as the Ren1 locus in two Central Asian table grape accessions. Other PM-resistant cultivated varieties and accessions of the wild ancestor V. vinifera subsp. sylvestris were soon identified raising questions regarding the origin of the resistance. In this study, F1 breeding populations were developed with a PM susceptible V. vinifera subsp. vinifera breeding line and a PM-resistant subsp. sylvestris accession. Genotyping was carried out with five Ren1 locus linked SSR markers. A PM resistance locus explaining up to 96% of the phenotypic variation was identified in the same genomic position, where the Ren1 locus was previously reported. New SSR marker alleles linked with the resistance locus were identified. We report results of PM resistance in multiple accessions of subsp. sylvestris collected as seed lots or cuttings from five countries in the Caucasus and Central Asia. A total of 20 females from 11 seed lots and 19 males from nine seed lots collected from Georgia, Armenia, and Azerbaijan were resistant to PM. Three male and one female plant collected as cuttings from Afghanistan and Iran were also resistant to PM. Allelic analysis of markers linked with the Ren1 locus in conjunction with disease evaluation data found a high diversity of allelic haplotypes, which are only possible via recombination events occurring over a long time period. Sequence analysis of two alleles of the SSR marker that cosegregates with the resistance found SNPs that were present in the wild progenitor and in cultivated forms. Variable levels of PM resistance among the tested accessions were also observed. These lines of evidence suggest that the powdery mildew fungus may have been present in Asia for a longer time than currently thought, giving the wild progenitor V. vinifera subsp. sylvestris time to coevolve with and develop resistance to this pathogen.
Highlights
Grapes are the most economically important perennial horticultural crop in the world[1]
We report the discovery of powdery mildew (PM) resistance in multiple accessions of subsp. sylvestris that were collected as seed lots or cuttings from five countries
Two sets of germplasm were evaluated for PM resistance
Summary
Grapes are the most economically important perennial horticultural crop in the world[1]. The major centers of grapevine diversity are East Asia and North America with up to 30 and 28 reported species, respectively[2,3]. Most cultivated grapes belong to the species Vitis vinifera, which is further subdivided into two subspecies subsp. There is evidence of human presence for more than 20,000 years in the mountains of the southern Caucasus[8], and transitional types of grapes that include wild forms of the subsp. Sylvestris, feral and cultivated landraces, and ancient local varieties are common in this region. Grapevines were disseminated from the primary center of domestication to Europe and North Africa following trade routes and reached Central Europe by the first millennium BCE.
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