Stomatal abundance in grapevine: Developmental genes, genotypic variation, and physiology

Grapevine cultivation is threatened by the global warming, which combines high temperatures and reduced rainfall, impacting in wine quality and even plant survival. Breeding for varieties resilient to these challenges must address plant traits such as tolerance to supraoptimal temperatures and optimized water use efficiency while minimizing productivity and quality losses. Stomatal abundance (SA) determines the maximum leaf potential for transpiration and thus water loss and cooling. Since SA results from a developmental process during leaf emergence and growth, knowledge on the genetic control of this process would provide specific targets for modification. Several genes controlling stomatal development have been characterized in Arabidopsis. Using translational genomics, we identified in the grapevine reference genome single orthologues of the master stomatal development regulators SPCH, MUTE and FAMA. We complemented Arabidopsis loss-of-function mutants with the grapevine candidate proteins, whose conditional overexpression also produced the expected epidermal phenotypes. The corresponding grapevine gene promoters are also under study. Additionally, we scored SA in 13 grapevine varieties over four consecutive growing seasons, and disclosed substantial SA differences with a strong genetic basis. These varieties were also examined for water use efficiency and physiological performance under drought and irrigation, finding significant varietal differences. Correlating developmental and physiological traits will contribute useful tools for grapevine management and breeding.