Grapevine, Vitis vinifera L.,is mainly cultivated for the production of wine, table grapes, raisins and juices. In 2016, almost 8 million hectares were planted with grapevines worldwide, with a total wine production of more than 270 million liters. Vitis viniferaspecies includes twosubspecies: sylvestris, the dioecious wild form and sativaor vinifera,its derived domesticated form.Cultivated, sativavarietiesnormally bear hermaphrodite flowers,although a few ancient varieties with female flowersstill exist. Although the molecular basis of sex determination ingrapevine is still unknown, a QTL on chromosome 2 has been described as the Sex locus and includes several candidate genes that could play a fundamental role in sex determination. The main objective of this work is the genetic and molecular characterization of a somatic variant line of cultivarTempranillo Tinto that develops android flowers instead of the regular hermaphrodite flowers. Those android flowers carrynormal stamens and a small gynoecium that, unlike male flowers, still allows fertilization andthe developmentof berries. Phenotyping of the flowersex in a self-progeny of thisTempranillo variant line showed that the mutant phenotype isheritableas a dominant trait appearing in the frequency expected of hermaphrodite flowers. Additionally, genotyping of a microsatellite marker linked to the Sex locus, VVIB23, also supportsthat the putative causal mutation is fully linked tothis locus. We found that acandidate gene within this locus,VviAPT3,encoding an adenine phosphoribosyl transferase that may inactivate cytokinins, isoverexpressed in the variant line compared to normal Tempranillo Tinto. In addition, cytokinins applied externallyon inflorescencesof the variant line were able to induce the developmentof a gynoeciumof normal size. Several experiments following genomics and transcriptomics approaches as well as other focused on VviAPT3and other candidate geneswithin the Sex locus are ongoing to identify thecausalgenetic variation. Understanding this mutant phenotype could help providing molecular genetic evidence on the control of sexual dimorphism in grapevine.

Resumen del trabajo presentado en la XV Reunión de Biología Molecular de Plantas (XV Meeting of Plant Molecular Biology), celebrada online los días 26 y 27 de noviembre de 2020

This study was funded by the Spanish MICINN BIO2017-86375 project and PRE2018-086017 Spanish grant for pre-doctoral contracts (FPI).