Few main parents contributed to grapevine traditional variety assortment in north western Italy as revealed by microsatellites and SNPs

Studies on parentage and kinship of Vitis vinifera traditional grape cultivars allow shedding light into the likely natural breeding at the basis of the assortment evolution of cultivated grapevines in a certain area during several centuries. They therefore contribute to understand the process of domestication and local development of viticulture through farmer selection and to draw the origin and the history of traditional grape cultivars. For wine grapes, these evidences add significant marketing value to wines and their terroirs, being highly appealing for wine consumers and wine lovers. Around 200 grape cultivars, traditional from north and north western Italy, and nearly 700 unique cultivars mainly from other Italian regions and Central Europe were examined for genetic kinship through nuclear microsatellite markers (nSSR). More than 100 genotypes showed parent/offspring or kinship relationships as revealed by 32 SSR loci. Forty trios of parents and descendants were disclosed, among which the pedigree of 'Dolcetto', the third most planted variety in Piedmont. For samples analysed also by the 20K Illumina SNPs chip, the parental relationships were confirmed. The results, corroborating a pattern shown by other studies, indicate closer kinship among cultivars from the same geographical area, and a complex network of pedigrees with few major founders showing from 12 to 21 links with other cultivars. These main genitors are often varieties no longer cultivated and/or nowadays threatened for extinction. This fact highlights on one hand the urgency of rescuing and preserving these genetic key links before they get missed. On the other hand it explains the jigsaw puzzle still unsolved about the origin of many renowned grape cultivars. Also, their ampelographic features provide significant clues for linking their identity with ancient varieties depicted or described centuries ago, contributing to shed light on the history of descendant cultivars of current high economic value.