Callus induction and somatic embryogenesis in muscadine and seedless bunch grapes (Vitis) from immature ovule culture

Pre-embryogenic calli were obtained from the culture of fertilized immature ovules of muscadine (Vitis rotundifolia Michx.) and seedless bunch grapes (Vitis vinifera L.) on: 1) Murashige & Turcker (MT, 1969) basal medium supplemented with 4.4 mu M 2, 4-D (2, 4-dichlorophenoxyacetic acid) and 1 mu M BA (6-benzyladenine) with 6.0% (w/v) sucrose; 2) Chee and Pool (CP, 1978) basal medium supplemented with 5.0 mu M NAA (alpha-naphthaleneacetic acid) and 1.0 mu M BA with 3.0% sucrose; and 3) Nitch and Nitch (NN, 1969) medium supplemented with 9.0 mu M 2, 4-D and 4.0 mu M BA with 3.0% sucrose, respectively. Somatic embryogenesis, with a success rate of 1.1 to 2.2%, was achieved in seedless bunch grape cultivars 'Autumn Royal Seedless', 'Crimson Seedless', and with muscadine grape cultivars; 'Alachua', 'Summit', and 'Tara' when the callus was subcultured on those NN media with or without plant growth regulators (PGR). The frequency of somatic embryogenesis was genotype dependent and greater in callus derived from white crystal callus. Embryogenic calli maintained their regeneration capacity for 24 months. Somatic embryos proliferated rapidly and germinated and developed into normal plantlets after transfer to Lloyd and McCown Woody Plant (WP) medium supplemented with 1 mu M BA and 1.5% (w/v) sucrose.