Optimization of Embryo Rescue System for Different Ploidy Crosses and Creation of Triploid Germplasm in Grape

To further improve the efficiency of triploid embryo rescue breeding and accelerate the selection of new seedless grape varieties, this study utilized six diploid and three tetraploid grape varieties as parents, configuring 15 cross combinations. The effects of sampling time, abnormal seedling rescue, and parental genotype on embryo rescue efficiency were investigated, and the early ploidy identification of hybrid progeny was conducted using flow cytometry. The results show that the optimal sampling time for crosses with ‘Sweet Scarlet’ as the female parent was 45 days after pollination. Among these, the embryo development rate (20.71%) and plantlet formation rate (10.00%) of the ‘Sweet Scarlet × Jumeigui’ combination were significantly higher than those of other treatments. Embryo germination results indicate that among 1535 developed embryos, normal plantlets accounted for 42.67%, while abnormal plantlets accounted for 31.51%, with the proportions of abnormal plantlets in ‘Jumeigui × Shine Muscat’ and ‘Ruby Seedless × Jumeigui’ exceeding 60%. A total of 494 abnormal seedlings were subjected to rescue, ultimately yielding 165 normal plants, with an average conversion rate of 33.40%, among which ‘Queen Nina × Muscat Hamburg’ achieved the highest conversion rate (66.67%). Ploidy identification of 229 hybrid seedlings from 10 cross combinations using flow cytometry revealed 70 diploids, 51 triploids, 26 tetraploids, and 82 aneuploids, with a triploid hybrid rate of 22.27%. Within the parental materials tested in this study, the hybrid combinations using the diploid seeded cultivar ‘Wink’ as the female parent yielded a higher proportion of triploid hybrids than those with tetraploid female parents. Ultimately, 532 hybrid progeny were successfully transplanted and survived, providing important material foundations and technical references for germplasm innovation and elite variety breeding of seedless triploid grapes.