[Protoplast culture and plant regeneration of the methionine resistant variant of Astragalus melilotoides Pall].

An efficient protocol for plant regeneration from protoplasts of the methionine resistant variant of Astragalus melilotoides was established. The friable calli induced from internode segments of variant plants were used for protoplast preparation. The protoplasts were isolated through enzyme digestion. Calli were formed after sustained divisions of protoplasts. High frequency of shoot differentiation was obtained from the protocalli on differentiated medium. The effects of different media, culturing methods and plating densities on protoplast divisions and plant regeneration were studied. The results show that agarose-beads culture method, KM8p medium supplemented with 1.0 mg/L 2,4-D, 0.5mg/L 6BA, 0.3 mol/L mannitol, 2% (W/V) sucrose and 500 mg/L casein hydrolysate at a plating density of 3 x 10(5)/mL are the appropriate conditions for protoplast division of the methionine resistant cell line. The division frequency is over 38%. The protoplast-regenerated plants still preserve resistance to methionine and ethionine.This research builds up the foundation for the resistant cell line as a parent of somatic hybridization.