Effect of culture medium, genotype, and year of cross on embryo development and recovery from in vitro cultured ovules in breeding stenospermocarpic seedless grape varieties

Abstract

A highly efficient embryo rescue technique using in ovulo culture is critical for maximising success when using stenospermocarpic female parents to breed new seedless grape varieties. The effects of medium composition, pollen parent, and year of cross on embryo development and recovery in cultured ovules were investigated to improve in ovulo embryo rescue from stenospermocarpic parents commonly used in breeding seedless grapes for the Australian table and dried grape industries. Increasing CaCl2 concentrations in the culture medium improved embryo recovery, but embryo emergence from ovules and germination rates were unaffected by varying FeEDTA concentrations. A casein hydrolysate supplement in the culture medium improved embryo recovery, emergence, and germination. Embryo recovery varied with parental genotype and ranged from 5% to 14% in 4 self-pollinated genotypes. Mean embryo recoveries from ovules cultured 50 days after controlled cross-pollination from berries of the pollen-sterile, stenospermocarpic variety ‘Carina’ were 36% and 26% where the pollen parents were seeded (11 crosses) and seedless (6 crosses), respectively. Embryo recovery and germination were affected by the year in which a cross was made and there was a significant cross × year interaction. The results indicated that in ovulo embryo rescue can be improved by increasing CaCl2 concentrations and incorporating a casein hydrolysate supplement in the basal medium, by exploiting genotypic differences through the use of seedless parents that yield greater proportions of rescued hybrids, and possibly by understanding environmental effects on female parents to maximise the numbers of hybrids produced.