Evaluation and genetic analysis of grapevine black rot resistances
Black rot of grapevine is caused by the hemibiotrophic fungus Guignardia bidwellii (Ellis) Viala and Ravaz. The vine disease originally occurred in North America and was introduced to Europe with plant material in the second half of the 19th century. So far studied, all traditional European grapevine cultivars can be infected by the black rot fungus which can lead to severe yield losses under unfavorable conditions. In order to screen genetic resources for black rot resistances experimental plants were artificially inoculated with spores of in vitro propagated G. bidwellii and finally rated for black rot symptoms on their leaves. We evaluated (i) accessions of different wild species of the genus Vitis, (ii) about 30 American-French hybrids and (iii) a mapping population. Among the wild species tested most accessions from V. aestivalis, V. cinerea and V. vulpina showed no disease symptoms whereas half of the accessions of V. amurensis showed typical black rot lesions. In the set of the hybrids, 15 cultivars with mainly V. labrusca and V. vinifera in their genetic backgrounds were rated as resistant. To study the genetic basis of black rot resistance and for the development of tightly linked markers for marker-assisted selection in breeding programs we analysed a mapping population of GF.GA-47-42 × 'Villard Blanc'. First analysis detected several resistance loci scattered over the entire genome. Among them, one major locus is located on chromosome 14 in the same region where previously black rot resistances were mapped in two other biparental populations.