Survey of Chloride Exclusion in Grape Germplasm from the Southwestern United States and Mexico

Increasing salinization is a threat to viticultural production as the quantity and quality of irrigation water decreases. Grapevines are particularly sensitive to chloride ions, but some wild species of Vitis L. have been found to restrict chloride uptake. Therefore, it is possible to breed rootstocks that prevent chloride from reaching the leaves or fruit, where buildup of the ion can reduce photosynthetic capacity and affect fruit and wine quality. A previously developed greenhouse screen for chloride exclusion, which mimics field results, was applied to 325 accessions of 14 Vitis species collected from the southwestern United States and Mexico. While the trait was not clearly associated with any particular species or geographic region, promising chloride-excluding accessions were identified. Vitis girdiana Munson from southern Nevada and V. X doaniana Munson ex Viala from the border of Texas and Oklahoma both consistently restricted chloride uptake in comparison to 140 Ruggeri (140 Ru), a known salt excluder. In addition, many accessions of V. girdiana from southern Nevada took up less than half the concentration of chloride in the roots as compared with 140 Ru. The prevalence of the chloride exclusion trait across multiple genetic backgrounds indicates that this collection may contain multiple sources for chloride exclusion in grape. This screen is an important first step in the characterization of Vitis rootstock breeding material from the southwestern United States and Mexico.