Enhancing grapevine rootstock genetic diversity through novel American Vitis progenies

Abstract

Grafting is the predominant propagation method for vineyard establishment worldwide, strongly affecting grape and wine quality. Since their introduction in the late XIX century, grapevine rootstocks have been subjected to genetic improvement primarily aimed at enhancing tolerance to environmental stresses, such as pests, limestone and drought. However, breeding activity drastically declined over the XX century, leading to a limited number of rootstocks available today.

Moreover, most currently used rootstocks derive from a narrow set of founders, further limiting the existing genetic base. Although current rootstock supports viticulture across various pedoclimatic conditions, expanding their genetic base is crucial to address future environmental conditions, especially in the context of climate change.

The preservation of grapevine rootstocks germplasm represents a valuable resource for breeding programs. One of the largest Italian rootstock collection, consisting of about 500 accessions and representing most of the rootstocks used worldwide, has been genotyped with SSR markers, revealing 232 unique genetic profiles. Acore-collection of 70 genotypes was identified to represent the overall genetic diversity of this collection.

The present study aims to evaluate how much the genetic diversity of the rootstock collection can be enhanced by introducing new genotypes derived from American Vitis spp. progenies that have not yet been exploited for rootstock breeding. The existing core-collection and 30 additional genotypes from American progenies were analyzed using an 18k SNP array. Considered genotypes originated from open pollination of V. arizonica, V. acerifolia, V. monticola, V. aestivalis, V. cinerea, V. champinii and V. rotundifolia. Genetic diversity was assessed by estimating heterozygosity and characterizing genetic structure through SNP based multivariate and clustering analyses.

Results showed an increase in genetic variability and a more complex genetic structure after introducing the new American genotypes, enabling the integration of this expanded diversity into an updated SNP-based core-collection. Furthermore, the analyzed American genotypes are currently undergoing phenotyping to determine how this broader genetic base may contribute to enhanced abiotic stress tolerance under future climate scenarios.