Construction of a high-density genetic map and detection of a major QTL of resistance to powdery mildew (Erysiphe necator Sch.) in Caucasian grapes (Vitis vinifera L.)

Abstract

Background Vitis vinifera L. is the most cultivated grapevine species worldwide. Erysiphe necator Sch., the causal agent of grape powdery mildew, is one of the main pathogens affecting viticulture. V. vinifera has little or no genetic resistances against E. necator and the grape industry is highly dependent on agrochemicals. Some Caucasian V. vinifera accessions have been reported to be resistant to E. necator and to have no genetic relationships to known sources of resistance to powdery mildew. The main purpose of this work was the study and mapping of the resistance to E. necator in the Caucasian grapes ‘Shavtsitska’ and ‘Tskhvedianis tetra’. Results The Caucasian varieties ‘Shavtsitska’ and ‘Tskhvedianis tetra’ showed a strong partial resistance to E. necator which segregated in two cross populations: the resistant genotypes delayed and limited the pathogen mycelium growth, sporulation intensity and number of conidia generated. A total of 184 seedlings of ‘Shavtsitska’ x ‘Glera’ population were genotyped through the Genotyping by Sequencing (GBS) technology and two high-density linkage maps were developed for the cross parents. The QTL analysis revealed a major resistance locus, explaining up to 80.15% of the phenotypic variance, on ‘Shavtsitska’ linkage group 13, which was associated with a reduced pathogen infection as well as an enhanced plant necrotic response. The genotyping of 105 Caucasian accessions with SSR markers flanking the QTL revealed that the resistant haplotype of ‘Shavtsitska’ was shared by ‘Tskhvedianis tetra’ and a total of 25 Caucasian grape varieties, suggesting a widespread presence of this resistance in the surveyed germplasm. The uncovered QTL was mapped in the region where the Ren1 locus of resistance to E. necator, identified in the V. vinifera ‘Kishmish vatkana’ and related grapes of Central Asia, is located. The genetic analysis conducted revealed that the Caucasian grapes in this study exhibit a resistant haplotype different from that of Central Asian grape accessions. Conclusions The QTL isolated in ‘Shavtsitska’ and present in the Caucasian V. vinifera varieties could be a new candidate gene of resistance to E. necator to use in breeding programmes. It co-localizes with the Ren1 locus but shows a different haplotype from that of grapevines of Central Asia. We therefore consider that the Caucasian resistance locus, named Ren1.2, contains a member of a cluster of R-genes, of which the region is rich, and to be linked with, or possibly allelic, to Ren1.

Identification of powdery mildew resistance in wild grapevine (Vitis vinifera subsp. sylvestris Gmel Hegi) from Croatia and Bosnia and Herzegovina

“…These results may indicate a common source of Ren1 loci in studied V. sylvestris . However, as was recently discussed for Caucasus V. vinifera cvs., high complexity at the chromosome 13 region and information gathered thus far does not permit conclusions as to whether studied genotypes from the Caucasus and Central Asia share the same resistance genes 28 .…”

“…SNP Genotyping by Sequencing approach revealed significant and unexpectedly high segregation distortions from Mendelian ratios on chromosome 13 in the susceptible V. vinifera cv. ‘Glera’, making one end of its chromatide less-inherited in the offspring 28 .…”

Powdery Mildew Resistance Genes in Vines: An Opportunity to Achieve a More Sustainable Viticulture

“…Several loci associated with powdery mildew resistance have been identified in different species of the Vitaceae family. These loci have been named Ren1 [59], Ren1.2 [68], Ren2 [63,69], Ren3 [65,70], Ren4 [54], Ren5 [60], Ren6 [57], Ren7 [57], Ren8 [66], Ren9 [65], Ren10 [67], Ren11 [61], Run1 [52,53], Run1.2a and b [71], Run2.1 [55,71], and Run2.2 [55,71] (Figure 1). In the case of most Run and Ren loci, it is not clear which genes are responsible for powdery mildew resistance and their mechanism of action [34].…”

“…Recently, Possamai et al [68] described the Ren1.2 locus, a variant of Ren1. It was mapped in the Caucasus V. vinifera cv.…”

“…Interestingly, the Ren1 and Ren1.2 loci were found in cultivars of different origins, suggesting that Caucasus grapevines have independently developed their resistance loci in the exact same location as Ren1. The Ren1.2 locus provides partial resistance to E. necator, reducing hyphal proliferation and sporulation [68].…”