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Background  Grapevine powdery mildew  Erysiphe necator  is a major fungal disease in all grape growing countries worldwide. Breeding for resistance to this disease is crucial to avoid extensive fungicide applications that are costly, labor intensive and may have detrimental effects on the environment. In the past decade, Chinese  Vitis  species have attracted attention from grape breeders because of their strong resistance to powdery mildew and their lack of negative fruit quality attributes that are often present in resistant North American species. In this study, we investigated powdery mildew resistance in multiple accessions of the Chinese species  Vitis piasezkii  that were collected during the 1980 Sino-American botanical expedition to the western Hubei province of China.    Results  A framework genetic map was developed using simple sequence repeat markers in 277 seedlings of an F1 mapping population arising from a cross of the powdery mildew susceptible  Vitis vinifera  selection F2-35 and a resistant accession of  V. piasezkii  DVIT2027. Quantitative trait locus analyses identified two major powdery mildew resistance loci on chromosome 9 ( Ren6 ) and chromosome 19 ( Ren7 ) explaining 74.8 % of the cumulative phenotypic variation. The quantitative trait locus analysis for each locus, in the absence of the other, explained 95.4 % phenotypic variation for  Ren6 , while  Ren7  accounted for 71.9 % of the phenotypic variation. Screening of an additional 259 seedlings of the F1 population and 910 seedlings from four pseudo-backcross populations with SSR markers defined regions of 22 kb and 330 kb for  Ren6  and  Ren7  in the  V. vinifera  PN40024 (12X) genome sequence, respectively.  Both  R  loci operate post-penetration through the induction of programmed cell death, but vary significantly in the speed of response and degree of resistance;  Ren6  confers complete resistance whereas  Ren7  confers partial resistance to the disease with reduced colony size. A comparison of the kinetics of induction of powdery mildew resistance mediated by  Ren6 ,  Ren7  and the  Run1  locus from  Muscadinia rotundifolia , indicated that the speed and strength of resistance conferred by  Ren6  is greater than that of  Run1  which, in turn, is superior to that conferred by  Ren7 .    Conclusions  This is the first report of mapping powdery mildew resistance in the Chinese species  V. piasezkii . Two distinct powdery mildew  R  loci designated  Ren6  and  Ren7  were found in multiple accessions of this Chinese grape species. Their location on different chromosomes to previously reported powdery mildew resistance  R  loci offers the potential for grape breeders to combine these  R  genes with existing powdery mildew  R  loci to produce grape germplasm with more durable resistance against this rapidly evolving fungal pathogen.    Electronic supplementary material  The online version of this article (doi:10.1186/s12870-016-0855-8) contains supplementary material, which is available to authorized users.

Identification of two novel powdery mildew resistance loci, Ren6 and Ren7, from the wild Chinese grape species Vitis piasezkii