High-throughput 18K SNP array to assess genetic variability of the main grapevine cultivars from Sicily

The viticulture of Sicily, for its vocation, is one of the most important and ancient forms in Italy. Autochthonous grapevine cultivars, many of which known throughout the world, have always been cultivated in the island from many centuries. With the aim to preserve this large grapevine diversity, previous studies have already started to assess the genetic variability among the Sicilian cultivars by using morphological and microsatellite markers. In this study, simple sequence repeat (SSR) were utilized to verify the true-to-typeness of a large clone collection (101) belonging to 21 biotypes of the most 10 cultivated Sicilian cultivars. Afterwards, 42 Organization Internationale de la Vigne et du Vin (OIV) descriptors and a high-throughput single nucleotide polymorphism (SNP) genotyping array (Vitis18kSNP) were applied to assess genetic variability among cultivars and biotypes of the same cultivar. Ampelographic traits and high-throughput SNP genotyping platforms provided an accuracy estimation of genetic diversity in the Sicilian germplasm, showing the relationships among cultivars by cluster and multivariate analyses. The large SNP panel defined sub-clusters unable to discern among biotypes, previously classified by ampelographic analysis, belonging to each cultivar. These results suggested that a very large number of SNP did not cover the genome regions harboring few morphological traits. Genetic structure of the collection revealed a clear optimum number of groups for K = 3, clustering in the same group a significant portion of family-related genotypes. Parentage analysis highlighted significant relationships among Sicilian grape cultivars and Sangiovese, as already reported, but also the first evidences of the relationships between Nero d'Avola and both Inzolia and Catarratto. Finally, a small panel of highly informative markers (12 SNPs) allowed us to isolate a private profile for each Sicilian cultivar, providing a new tool for cultivar identification.