Somatic embryogenesis and plant regeneration from protoplasts of asparagus (Asparagus officinalis L.).

Protoplasts were isolated from embryogenic calli of Asparagus officinalis L. cv. Mary Washington and cultured in 1/2 MS medium with 1 mg/l NAA, 0.5 mg/l zeatin, 1 g/l L-glutamine, 0.6 M glucose and 0.1% Gellan Gum. Protoplasts started to divide after 3-4 d of culture and formed visible colonies after 30 d of culture. The percentage of colony formation (plating efficiency) was 7.2%. The colonies were then transferred onto Gellan Gum-solidified MS medium containing 1 mg/l 2,4-D and 3% sucrose for further growth. Somatic embryos were induced from all colonies of 0.5-1.0 mm size after transferring to 1/2 MS medium lacking growth regulators. After treating these somatic embryos (1-3 mm) in distilled water for a week, 30-40% of them germinated normally and grew into plantlets 20-30 d after transplanting on 1/2 MS medium containing 1 mg/l IBA, 1 mg/l GA3 and 1% sucrose. These protoplast-derived plants were diploid with 20 chromosomes.