Parents' Selection Affects Embryo Rescue, Seed Regeneration and the Heredity of Seedless Trait in Table Grape Breeding Programs

The development of new seedless cultivar represents one of the most important goals in table grape breeding programmes worldwide. The most common technique to obtain new seedless cultivars is embryo rescue, an approach that allows the isolation of immature embryos and their cultivation in vitro. In this study, a total of 23 crosses (developed employing one seeded and one seedless parent) were performed during two seasons (2017 and 2018) for a total of 1140 seedlings. For each cross, the principal parameters related to the efficiency of the pollination were measured (harvested bunches, collected berries, recovered embryos/seeds and plants obtained). Based on these traits, statistical analyses were performed to calculate the female and male parental efficiency and to compare the two techniques of propagation employed: embryo rescue (7.8% of plants obtained) and gamic propagation (8.4%). Finally, the segregation of the SSR marker p3_VvAGL11 was evaluated on the progeny of four crosses in which the same cultivar was used alternately as female or male parent (SugxIta/ItaxSug and CrixIta/ItaxCri). The parameters measured showed a positive correlation between berries, seeds and plants obtained, exclusively in combination with a seeded female parent. The crossing combinations investigated indicate that some genotypes outperformed others when used as female parent in terms of embryos/seeds produced. Therefore, the efficiency in terms of seedlings obtained for the seedless female parents is actually balanced with those obtained for the seeded ones. The proposed research aims to provide useful information to guide the choice of genotypes used in the genetic improvement programs of seedless grapes, to increase their efficiency.