Genetic variation for grapevine reproductive development

Plant reproductive development has evolved to ensure reproductive success. However, in crop species, genetic variation in reproductive development has also been targeted from domestication to current breeding programs to improve the production of fruits and seeds. In grapevine, genetic variation in reproductive developmental processes such as flower induction and initiation, inflorescence and flower development, and gamete, embryo and seed development have direct implications on most production traits, including fertility, cluster weight, cluster compactness or berry weight, but also on quality traits such as skin-to-pulp ratio or seedlessness. Lack of sexual reproduction in traditional wine-grape cultivars has allowed the accumulation of mutations that affect gamete development and viability as well as embryo and seed development. Mutations that would be lost through purifying selection in natural populations can provide interesting quality traits in grapevine cultivars. In this way, genetic variation decreasing gamete viability is behind low seed number per berry, berry size and cluster compactness phenotypes, current quality goals in clonal selection for low production and loose clusters. This trait can have negative consequences, depending on environmental conditions. Complete absence of gamete viability is behind some forms of parthenocarpic development, as in the case in the origin of 'Corinto' raisins. Genetic variation impairing ovule and seed development seems to be behind stenospermocarpic seedlessness, a main quality trait in table-grape breeding. All these examples point out how understanding the processes of grapevine reproductive development and particularly the existing genetic variation for these traits can help to develop more suitable and adapted cultivars for both wine and table grape production.