On the basis of protoplast culture, we performed protoplast fusion between Astragalus melilotoides Pall. and Zygophyllum xanthoxylum Maxim using a modified PEG high-pH, high-Ca²⁺ method. The protoplasts of A. melilotoides were
pretreated with Rhodamine-6G and those of Z. xanthoxylum with UV radiation. Both parent protoplasts were unable to undergo sustained division, but the interfamilial somatic hybrid cells could be selected because fusion cells renewed their sustained division capability owing to physiological complementation between the two parents. We obtained two hybrid cell lines through this selected procedure. Few buds were induced from only one hybrid cell line. Chromosome checking and molecular biological characterization confirmed the hybrid characters of the two hybrid cell lines. Physiological analyses revealed the salt and drought tolerance of the hybrid cell lines.