Key message The grapevine VviEPFL9 -2 paralog is specifically expressed during leaf expansion and its knockout provide a phenotype with superior adaptation to environmental stresses via reduced stomatal density. Abstract In Arabidopsis stomatal initiation relies on the transcription factor SPEECHLESS, which is positively regulated by AtEPFL9, a peptide of the epidermal patterning factor family. In grapevine, two EPFL9 paralogs...