New disease-resistant, seedless grapes are developed using embryo rescue and molecular markers

Improving the operation of embryo rescue technology is a highly efficient way to breed new high-quality cultivars of seedless, disease-resistant grapes when using a stenospermocarpic Vitis vinifera L. (female parents) hybrid with Chinese wild Vitis (male parents). In this study, sampling time had a significant effect on embryo recovery. Four crosses were investigated to improve the embryo rescue efficiency by determining the best sampling time, which was found to be 40, 50, 55, and 57 days after pollination (DAP) for 'Flame seedless' × 'Ruby seedless', 'Kunxiang seedless' × 'Flame seedless', 'Ruby seedless' self-pollination and 'Ruby seedless' × 'Flame seedless', respectively. The highest percentage embryo germination ranged from 60.83 to 89.10% for four cross-combinations when the embryo was germinated on woody plant medium (WPM), with 1.0-μM thidiazuron (TDZ, a potent cytokinin). For 11 cross-combinations, the embryo recovery rate varied from 4.8 to 29.6% and the plant development rate varied from 17.1 to 78.9%. 'Ruby seedless' was the best female parent followed by 'Flame seedless'. The Grape Seedless gene Probe 1 (GSLP1) and SCF27 molecular markers were used to assist the identification of the seedless traits of the 388 progeny. A total of 309 plantlets were amplified, with the specific bands at 569-bp and 2k-bp being preliminarily considered as seedless. The S382-615 marker was used to identify the downy mildew resistance of the 'Ruby seedless' × 'Beichun' cross. Two F1 progeny were amplified, with the specific band at 615-bp being identified as downy mildew resistance.