A few main parents contributed to the traditional grapevine cultivar assortment in north-western Italy, as revealed by microsatellites and single-nucleotide polymorphisms

Abstract

Studies on parentage and kinship of traditional Vitis vinifera grape cultivars allow light to be shed on the likely natural breeding at the basis of the assortment evolution of cultivated grapevines in a particular area over several centuries. They therefore contribute to our understanding of the process of domestication and local development of viticulture through farmer selection and allow us to infer the origin and history of traditional grape cultivars. For wine grapes, this evidence adds significant marketing value to wines and their terroirs, being highly appealing for wine consumers and wine lovers. Around 200 grape cultivars, traditional to 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 (nuclear simple sequence repeats; nSSRs). 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 was the pedigree of 'Dolcetto', the third most widely planted cultivar in Piedmont. For samples also analysed 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 a few major founders showing 12-21 links with other cultivars. These main genitors are often cultivars that are no longer cultivated and/or are nowadays threatened with extinction. On one hand, this highlights the urgency of rescuing and preserving these key genetic links before they are lost. On the other hand, it explains the still unsolved jigsaw puzzle of the origin of many renowned grape cultivars. Also, their ampelographic features provide significant clues for linking their identity with ancient cultivars depicted or described centuries ago, shedding light on the history of descendant cultivars of current high economic value.