Climate change is expected to increase irrigation demand at the same time as reducing irrigation supply, and developing plant material with lower irrigation needs is crucial to adapt the grape industry to future conditions.  Previous work suggests that altering stomatal traits to reduce maximum gas exchange rates or reduce gas exchange more strongly in response to water stress would increase grapevine water-use efficiency without compromising the carbon supply for growth and ripening.  The goal of our project is to use genetic engineering to generate plant material with water-saving stomatal traits, while leaving the rest of the genome intact, to experimentally test the effects of these traits on yield and ripening in economically important grape cultivars.  We will target four genes with known effects on stomatal traits and gas exchange for over-expression (OST1 and CLE25) or under-expression (knock-out mutations) (EPFL9 and EVE).  We will conduct these transformations in Thompson Seedless, as a table grape with a high success rate for genetic transformation, and Chardonnay, as the most-produced wine grape in California, including in hot, water-limited regions.  This year, the first year of a proposed five-year project, we completed the bioinformatics work needed for the plant transformations.  The Cantu lab completed sequencing for the Thompson Seedless genome and identified homologues for the four target genes in the two grape varieties.  The Cantu lab is currently creating the plasmids containing the target mutations, which will be supplied to the UC Davis Plant Transformation facility to create the transformed plant material.