Genetics of adventitious root formation in grapevines

Abstract

Commercial grapevine propagation relies on the ability of dormant wood material to develop adventitious roots. Vitis riparia and V. rupestris, two North American native species, are the progenitors of most commercially available rootstocks due to their resistance to Phylloxera and excellent root-forming capacity. Despite the existence of at least 20 others native Vitis species in North America—many of which possess strong resistance to biotic and abiotic stresses—their use has been limited by either poor rooting ability or insufficient understanding of their rooting potential. To advance our understanding of adventitious root formation across Vitis, we combined whole genome sequencing with rooting data from a diverse panel of 19 Vitis species to characterize North American Vitis’ rooting potential, determine its genetic control, and identify associated genes. Using two ordinal scales to assess rooting ability at different stages of callusing, we identified significant genomic regions on chromosomes 2, 5, 10, 12, and 18 through genome-wide association analysis (GWA). Our analyses indicate that rooting capability is a quantitative trait with considerable variation within and between species and is not restricted to any single taxon. Most associations explained only a small proportion of phenotypic variation, suggesting that rooting ability is a complex trait controlled by multiple loci with small effects. Several genes associated with hormone regulation, cell wall modification, and stress response were found to be in linkage disequilibrium with significant genetic variants. Hormone accumulation analysis during callusing in extreme phenotypes confirmed the role of hormone-related genes in the ability of dormant cuttings to form adventitious roots. This research supports the implementation of molecular breeding approaches, including marker-assisted selection and genomic prediction, to accelerate the development of new climate-resilient rootstocks.