High embryogenic ability and plant regeneration of table grapevine cultivars (Vitis vinifera L.) induced by activated charcoal

Somatic embryos and plants from immature anthers or ovaries were obtained from the Vitis vinifera evs Sugraone, Crimson Seedless, Italia and Don Mariano. Explants were cultured on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid (4,7 or 10 mu M) and 6-benzyladenine (0.7, 1 or 1.3 mu M) for callus induction. Callus frequency depended on genotype, explant type and the culture medium used. Calli were transferred to half strength MS without growth regulators for embryo differentiation. The presence of activated charcoal (AC, 0.25%) in this medium was essential to obtain somatic embryos in the case of Crimson Seedless, Italia and Don Mariano and to increase the frequency of embryogenic calli in Sugraone (from 5.8% without AC to 99.5% with AC). Ovaries and anthers showed different degrees of embryogenic competence. When somatic embryos were placed in a medium with indole-3-acetic acid (10 mu M), gibberellic acid (1 mu M) and 0.25 % AC, embryo germination was normal, i.e. embryos turned green, the hypocotyls and cotyledons started to grow and the apical root axis developed. The percentage of germinated embryos was 100 % for Sugraone and 27.5%, 38.1% and 54.5% for Don Mariano, Italia and Crimson Seedless, respectively. When the germinated embryos were transferred to half strength MS medium in test tubes, 100 % of Crimson, Italia and Don Mariano and 68.3% of Sugraone embryos developed into normal plants.