Cassandra Bullock-Bent,* Kevin Fort, and M. Andrew Walker 
*Department of Viticulture and Enology, University of California, Davis, CA 95616 (cmbullock@ucdavis.edu)

This study investigated the effect of salinity stress on root growth of four grape rootstocks to understand how root traits relate to salt tolerance. Such traits are key to understanding salt tolerance, since roots adapt to environmental signals while acquiring nutrients and water. Greenhouse-grown 140Ru, O39-16, Ramsey, and Riparia Gloire were screened in 4-L pots with fritted clay at four salt concentrations: 0, 25, 50, and 75 mM NaCl. Plants were destructively harvested over three weekly intervals, with the first harvest occurring after one week of salt treatment. Roots were scanned and analyzed with the WinRHIZOTM image analysis system, which measured and classified root length, area, and volume. Leaves and roots were dried, ground, and analyzed for chloride content. O39- 16 accumulated the most chloride, followed by Ramsey, Riparia, and 140Ru. All rootstocks experienced a decline in root biomass, reduced root length, and increased specific root length as the Cl- concentration increased. O39-16 had the largest differences between 0 and 75 mM NaCl, compared to other genotypes. At higher salt concentrations, the lateral to structural root ratio and chloride accumulation in petioles produced the same ranking and may serve as a useful way to screen for salt tolerance in rootstock breeding programs.

Funding Support: California Grape Rootstock Improvement Commission, California Grape Rootstock Research Foundation, American Vineyard Foundation, CDFA Improvement Advisory Board, California Table Grape Commission, Louise Rossi Endowed Chair in Viticulture, scholarship support for Cassandra from American Society for Enology and Viticulture