Modernizing grapevine rootstock breeding at UC Davis: strategies, tools, and early outcomes

Abstract

Soil salinity is an increasingly critical challenge for grapevine production, particularly in Mediterranean climates like California. Chloride (Cl^–) accumulation, in particular, severely impacts vine growth, productivity, and fruit quality. Despite its significance, the genetic basis of chloride exclusion in Vitis remains poorly understood. In this talk, I will present recent findings from our lab that shed light on the underlying genetic architecture of this key trait.

We conducted a comprehensive genetic analysis of chloride exclusion using a diverse panel of 335 accessions spanning 18 wild and cultivated Vitis species. Following a controlled salt exposure, plants were phenotyped for leaf Cl^– content. We employed genome-wide association studies (GWAS) to identify loci associated with Cl^–exclusion. These findings were independently validated using QTL mapping in a biparental population segregating for this trait.

Our analyses identified a major QTL on chromosome 8, designated ClEX1, which harbors cation/H⁺ exchanger (CHX) genes, including homologs of AtCHX20, as strong candidates underlying chloride exclusion. We further detected functionally relevant SNPs within exonic regions of these genes. Additionally, we discovered a novel QTL on chromosome 19 enriched for G-type lectin S-receptor-like kinases, which are implicated in salt stress signalling. These loci offer promising targets for marker-assisted selection in rootstock breeding. In addition to these findings, I will discuss ongoing efforts in our UC Davis rootstock breeding program focused on drought resilience, adventitious root formation, root system architecture, and graft compatibility, traits essential for viticulture in a changing climate.