Production of triploid plants from crosses between diploid and tetraploid grapes (Vitis complex) through immature seed culture and subsequent embryo culture

To develop efficient embryo-rescue methods in breeding triploid grapes, a combination of immature seed culture and embryo culture, and embryo culture without the preceding culture of immature seeds were applied during different developmental stages of seeds from an interploid cross between tetraploid 'Red Pearl' and diploid 'Muscat Bailey A'. Embryos grew larger than Imm in their length after three months of the immature seed culture initiated between 24 and 56 days after pollination (DAP). Overall, the embryos through subsequent culture germinated and then grew into plantlets at the higher rates than did those cultured without the preceding immature seeds culture. The highest rate of seedling recovery was 31.5% per cultured seed when immature seeds were collected 52-56 DAP, though none of four growth regulators added separately to the medium of the preceding immature seed culture were effective for development of embryos cultured in the same period. Results from our present and recent studies on breeding triploid grapes indicated that a combination of immature seed culture and subsequent embryo culture initiated one to two weeks before veraison (the beginning of fruit-softening period) is the best method for efficient production of triploid grapes.