Embryo rescue of Chinese jujube (Ziziphus jujuba Mill.)

Most cultivars of Chinese jujube (Ziziphus jujuba Mill.), a native fruit tree of China, have very serious embryo abortion. In order to get hybrids, embryo rescue of four excellent cultivars, 'Dongzao', 'Jisifeng', 'Wudeng' and 'Fuzao', was carried out. An optimized system for embryo culture was established. Firstly, young embryos were cultured in the germination medium: MS+BA 0.1 similar to 0.5 mg/L + IBA 0.5 similar to 1.0 mg/L + NAA 0.1 mg/L + Sucrose 50 g/L + Agar 7 g/L + LH 500 mg/L. Secondly, the regenerated seedlings were transferred to growing medium: MS + Sucrose 30 g/L + Agar 5 g/L. Three patterns of development of cultured embryos occurred with the increase of embryo age, i.e. continuous growth (embryo less than 30 days old), callus formation, or direct germination. Of the factors affecting embryo culture, the quality and age of the embryo were the most important. Low temperature treatment (2 similar to 4 degrees C, 44 days) accelerated seedling formation but decreased the quality of seedling. 7 similar to 10 days dark treatment was helpful to rooting. Lateral roots of seedlings could be enhanced significantly by cutting the root tip.