Application of embryo rescue in grape (Vitis) cultivar development

Interspecific hybridization and stenospermocarpic seedless grape cultivars from Vitis vinifera L. or its hybrids have been widely used in Florida grape cultivar development. Unfortunately, interspecific sternospermocarpic hybrid em­bryos aborted prematurely and failed to develop into plants. Immature ovule cultures were conducted to rescue such embryos and recover the hybrid plants for improving grape breeding efficiency. Immature ovules were excised from berries 6 to 8 weeks after pollination and then cultured on Emershad and Ramming (ER) medium supplemented with 0.05 g·L–1 casein hydrolysate, 0.05 g·L–1 inositol, 1.21 g·L–1 cysteine, 0.98 g·L–1 MES [2-( N -Morpholino) ethanesulfonic acid] for 2 months, followed by dissecting embryos and cultured on Lloyd and McCown woody plant (WP) medium for germination. Ovules cultured on ER medium plus 0.2 mg·L–1 BAP (6-benzylaminopurine), Nitch and Nitch (NN) medium supplemented with 0.2 mg·L–1 NAA (α-naphthaleneacetic acid) and 0.5 mg·L–1 GA (gibberellin) were also tested for direct germination. It was found that using ER medium for ovules culture followed by WP medium for embryo germination was the most efficient approach for recovering aborted embryos. For example, 57.3% of hybrid embryos were rescued from ‘O47-3-7’ x ‘Orlando Seedless’, and 50.0% from its reciprocal cross. However, direct in vitro germination of the aborted embryos without ovule dissecting was found less success.