NORMALIZATION OF ASPARAGUS SOMATIC EMBRYOGENESIS USING A MALTOSE-CONTAINING MEDIUM

Embryogenic calli derived from internal buds were cultured and maintai ned on Murashige and Skoog (MS) medium containing 2 mg/L 2,4-D, 3 % su crose and 0.2 % gellan gum. Normal somatic embryos were induced from t he embryogenic calli by pretreating with 1/2 MS liquid medium for 7 da ys, sieving through 600 mu m stainless steel mesh and then partially d esiccating on plant growth regulator-free MS medium containing a high concentration of gellan gum (1.0 % w/v) for 1 week. Furthermore, use o f maltose as a sugar and/or osmoticum in the embryo induction medium p romoted development of normal somatic embryos. Using these methods, no n-vitrified bipolor embryos were induced 30 days after transfer (appro ximately 1,500 embryos per 0.1 mL packed cell volume). The somatic emb ryos induced on maltose-containing medium exhibited a much higher germ ination rate (more than 80 %) with cold treatment (14 days at 4 degree s C) than that induced on sucrose-containing medium.