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M. Meyerson, C.M. Benton and D.J. Gray

Micropropagation of Vitis bourquiniana Lenoir `Black Spanish', V. champini Planchon `Dog Ridge', Vitis hybrids (`Blanc du Bois', `Himrod', and `Niagara Seedless'), V. rotundifolia Michx. (`Carlos' and `Dixie'), and V. vinifera L. (`Autumn Seedless', `Cabernet Sauvignon', `Carignane', `French Colombard', `Ruby Cabernet', and `Tokay') was accomplished. Shoot tips taken from micropropagated plants in long-term culture were inoculated onto solidified C2D medium containing 5 μM benzyladenine. Culture times consisting of either one or two 4-week cycles were compared for effect on shoot number. A range of response among cultivars tested was noted. The best-responding variety was V. champini `Dog Ridge', with 5.8 shoots per apex. All other varieties were less prolific. When shoot micropropagation from nodal explants and apices was compared, so significant difference was noted. In vitro micropropagation offers rapid clonal production of grape and is a source of sterile leaf explant material for embryogenic cultures, which, in turn, are useful target for genetic transformation.

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D.J. Gray, K.A. Labeau and C.M. Benton

The development of grape somatic embryos (Vitis vinifera cv. Thompson Seedless) was studied using high-resolution light microscopy and scanning electron microscopy. Somatic embryos develop either from discrete embryogenic cell clusters (indirect somatic embryogenesis) or from previously formed somatic embryos (direct somatic embryogenesis). In both instances, embryo development begins when a small, isodiametric, densely cytoplasmic cell undergoes a series of organized divisions, which are identical to those observed during zygotic embryogenesis. Developing embryos pass through recognizable embryonic stages, remaining white and opaque through maturity. Upon germination, embryos begin to enlarge, become yellow, then green, and develop into morphologically correct plants. The cells of somatic embryos contain little starch, but abundant storage proteins. However, lipids comprise the primary storage compound. Some developmental abnormalities occur during embryogenesis, including overly enlarged hypocotyls and fewer or more than two cotyledons. In addition, relatively few somatic embryos grow into plants primarily due to inadequate shoot apical meristem development. These abnormalities are best attributed to inadequacies of the in vitro environment of medium in a culture vessel when compared to the in vivo environment of a seed.

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D.J. Gray, J.A. Mortensen, CM. Benton, R.E. Durham and G.A. Moore

Ovules of seedless bunch grapes (Vitis spp.) fertilized by controlled pollination increased in size during berry development. More ovules cultured 10 days or 60 to 70 days after pollination became brown compared to those cultured at 20 to 40 days. Cultured ovules developed with and without endosperm. Globular to torpedo stage embryos were recovered. More embryos and plants were recovered from ovules cultured at 40 or 60 days than at 10 or 20 days after pollination. Pollen parent significantly affected both embryo and plant recovery at certain sampling times. BA incorporated into medium significantly increased embryo germination percentage. Electrophoretic analysis of glucosephosphate isomerase in progeny showed that 67% to 88% were hybrids of controlled crosses. Of four vines that fruited thus far, two were seedless. Seedless progeny had smaller seed traces than either parent. Chemical name used: N-(phenylmethyl) -1H-purin-6-amine (BA).