Production of interspecific somatic hybrid plants in the genus Medicago through protoplast fusion.

Symmetric somatic hybrid plants have been produced by electrofusion of leaf protoplasts of Medicago sativa and callus protoplasts of Medicago coerulea. The selection of hybrid individuals has been performed at the cellular level by recording the positions of single heterocaryons immobilized in a semisolid culture medium. The hybrid nature of the heterokaryons was assessed in fluorescent light on the basis of their color. Hybrid minicalli were picked up manually and grown first on propagating, and then on regenerating, media. Six putative hybrid calli were selected and two of them regenerated several plants. The hybrid nature of the regenerants was confirmed by cytological and isozyme analysis. Among the several morphological traits taken into account for the characterization of somatic hybrid plants, some were intermediate, some lower, and some higher, with respect to the parents. The somatic hybrid plants were fertile and set seed. The production of somatic hybrid plants in the genus Medicago is discussed in relation to the regenerating capability of parental protoplasts.