Study On Breeding For Seedless Grape Varieties Using Embryo Rescue

Traditional cross breeding is the major method for breeding seedless grapevine,but grapevine cultivars with seed as female parent,time-consuming process and low efficiency restricted its development.Embryo rescue in breeding can use stenospermocarpic grapevine varieties as female parents and seedless or seeded varieties as male parents,which improves seedless rate of hybrid progenies,shortens breeding time and accelerates breeding process.In this study,there were 9 cross combinations with stenospermocarpic grapevine cultivars as female materials and seedless or seeded as male materials.Four factors influencing embryo rescue were studied,including parent genotype,sampling time,medium type for embryo development and sugar concentration in the medium for embryo germination.Meanwhile,cytological observation was conducted on abortion and development of embryo and endosperm of two seedless grapevine cultivars,Beauty Seedless and Fresno Seedless.Main results were as follows:(1)9086 hybrid ovules,1316 hybrid embryos and 497 hybrid strains were obtained from 9 cross combinations using embryo rescue,and the average embryo germination rate was 14.48% and the seedling rate was 5.47%.Hybrids obtained from this study can be used for the resource of seedless grapevine breeding in the future.(2)Different female parents affected the embryo development rate and seedling rate.The combinations of Kunxiang Seedless and Rudy Seedless as femal parents showed higher seedling rate and better embryo rescue efficiency.Therefore,the two cultivars were suitable for maternal plants.Male parents also had effect on embryo rescue.Kunxiang Seedless was as female,the seedling rate of three male parents were 7.35% for Beichun,8.37% for Ruby Seedless and 9.48% for Xinyu,respectively.Flame Seedless was female parent,that of Kunxiang Seedless and Beichun as male parents were 3.57% and 2.10%,respectively.(3)210 strains were identified to carry seedless trait by application of GLSP1-569 and SCF27-2000 among 326 hybrid progenies of four cross combinations.(4)Sampling time influenced significantly the result of embryo rescue and mainly depended on female genotype.According to seedling rate,the proper sampling time was as follows: 41 DAP and 7.35% of seedling rate for Flame Seedless × Kunxiang Seedless,40 DAP and 4.00% for Flame Seedless × Beichu,47 DAP and 13.33% and 11.89% for Kunxiang Seedless × Beichun and Kunxiang Seedless × Rudy Seedless,respectively,55 DAP and 8.21% for Rudy Seedless × Crimson Seedless.(5)For Flame Seedless × Kunxiang Seedless and Ruby Seedless × Crimson Seedless,the seedling rate on solid medium were higher obviously than that on solid-liquid medium,while there were no significant difference that of Kunxiang Seedless × Xinyu.For combinations of Rudy Seedless as female parent,1.5% sugar in medium for embryo development was better while 2.0% sugar was fit for Kunxiang × Beichun.(6)To confirm the embryo abortion time of Beauty Seedless and Fresno Seedless,the development and abortion process of embryo and endosperm were observed.The results showed that embryo abortion time of these two cultivars were both at 38 days after blooming.