In-ovulo embryo culture of Vitis vinifera L. c.v. «Thompson Seedless»

In-ovulo embryo culture of Vitis vinifera L. c.v. 'Thompson Seedless' was investigated as a method to enable the hybridization of stenospermic seedless grapes. Fertilized ovules taken 68 days after anthesis were cultured on two basal media: 1) Cain's medium; and 2) Stewart and Hsu's (1977) medium, both tested with five separate addenda (IBA, Ergostim@, tartaric acid, L-glutamine and L-cysteine). Addition of 10 mM L-cysteine to C medium promoted the growth of more embryos. Three months after culture, embryos were excised and subcultured. Thirty embryos were recovered by this method but only one embryo grew into a plant. THE DEVELOPMENT of seedless grape ( Vitis vinifera L.) cultivars is an important part of the U.S.D.A.'s grape breeding program at Fresno, CA. Conventional breeding of seedless grapes involves pollinating seeded grapes with pollen of seedless cultivars. The resulting progenies contain 10 to 15% seedless progeny (Weinberger and Harmon, 1964; Loomis and Weinberger,1979). The proportion of seedless progeny increases with the known amount of seedlessness in the parentage ofthe seeded parent (Weinberger and Harmon, 1964; Loomis and Weinberger, 1979), suggesting that intercrossing of seedless grapes to obtain seedless progeny would be more eXective. Many seedless grapes are stenospermic (Stout, 1936), in which fertilization occurs but embryo development stops soon after and the seed aborts. The use of these zygotic embryos in a breeding