Proliferative Somatic Embryogenesis from Zygotic Embryos of Grapevine

Zygotic embryos isolated from mature berries of Vitis longii Prince and V. vinifera L. cvs. Chardonnay, French Colombard, Grenache, and White Riesling produced somatic embryos when cultured on solid Nitsch and Nitsch medium. Explants of V. vinifera cv. Pinot noir did not produce somatic embryos. The highest incidence of somatic embryogenesis occurred on medium containing (all in mg·liter −1 ) 1.0 NOA plus 0.2 BAP, except in ‘White Riesling’, where 1.0 NOA plus 1.0 BAP was optimal. Somatic embryos developed asynchronously from a mass of white proembryos and passed through globular, heart, and torpedo-shaped stages. Embryos proliferated by budding at the surface of globular embryos. With regular transfers, embryogenic tissues remained morphogenically competent for up to 1 year. Zygotic embryo explants cultured on medium without growth regulators usually germinated within 10 days and produced healthy seedlings. About 40% of somatic embryos germinated after isolation from their parental cultures and transfer to fresh medium. At the concentrations tested, NAA, BAP, and GA 3 did not improve germination frequency over that obtained with basal medium and, in some cases, severely reduced germination. Plants were established in the greenhouse and no morphological abnormalities were observed. Chemical names used: 6-benzylam-inopurine (BAP); gibberellic acid (GA 3 ); 2-(l-naphthyl)acetic acid (NAA); 2-naphthoxyacetic acid (NOA).