Single nucleotide polymorphism profiles reveal an admixture genetic structure of grapevine germplasm from Calabria, Italy, uncovering its key role for the diversification of cultivars in the Mediterranean Basin

Background and Aims: Grapevine (Vitis vinifera L.) is one of the earliest domesticated crops, dating back 6000years ago in the Near East before spreading into Europe. Despite the abundance of historical, archaeological and genetic records, until now secondary domestication events in European regions are not well demonstrated. Here, a genetic characterisation of grape germplasm from Calabria in Southern Italy, a crucial area of the Mediterranean Basin, aims to validate this area as a secondary centre of crop domestication. Methods and Results: True-to-type cultivar classification of 72 accessions was carried out by using microsatellite loci (simple sequence repeat) along with the main Organisation Internationale de la Vigne et du Vin ampelographic descriptors. The classification highlighted a high level of genetic diversity (He = 0.83) among native cultivars from Calabria. A decay of genetic diversity moving from southern Italy to north-western Mediterranean regions was observed, probably because of repeated founder effects during the grapevine expansion from the Mediterranean Basin to Europe. Single nucleotide polymorphism analysis showed an admixture genetic structure at K=7, clarifying a complex network of pedigree relationships generated by crosses among cultivars. Parentage analysis underlined a high proportion of parent-offspring relationships (76%) in Mantonico Bianco and Pecorello, hypothesising their key role in the pedigree of many native cultivars from the southern Mediterranean area. Conclusion: Overall, our results appear to indicate a pivotal role of cultivars from Calabria in the grape genetic diversity of southern Italy. Furthermore, genetic analysis of grape wild accessions from Calabria should be of value in a discussion of a secondary centre of grape domestication. Significance of the Study: A large grape collection from Calabria was for the first time characterised through ampelographic and genetic analysis.