Screening local grapevine germplasm for resistance to powdery mildew

Abstract

Grapevine (Vitis vinifera) is one of the most widely cultivated perennial crops in Italy; however, most of cultivars are susceptible to powdery mildew, a major fungal disease caused by Erysiphe necator. In this context, a comprehensive phenotypic and genetic characterization of unexplored germplasm may represent a useful strategy for identifying novel sources of tolerance to be exploited in new breeding programs. To this end, two grapevine collections were analyzed. The first comprised local varieties rediscovered in recent years due to their valuable ampelographic, morphological, and qualitative traits. The second consisted of a full-sib table grape population developed by crossing the Hungarian cultivar ‘Terez’, which exhibits resistance to powdery mildew, with the susceptible, seedless table grape cultivar ‘Autumn Giant’. A total of 246 accessions were genotyped using a high throughput 20K SNP array and phenotyped through in vitro leaf inoculation assays and assessment of disease severity. The resulting genotypic and phenotypic data were integrated into QTL mapping (for the segregating population) and a genome-wide association study (GWAS) for the germplasm collection. These analyses will help to identify genomic regions closely associated with powdery mildew resistance, helping to dissect the genetic determinism of the resistance/susceptibility to powdery mildew of grape.