Plant regeneration via somatic embryogenesis from protoplasts of Uganda cherry orange (Citropsis schweinfurthii)

Protoplasts isolated from embryogenic callus of Citropsis schweinfurthii (Engl.) Swing. & M. Kell were cultured in MT (Murashige and Tucker 1969) basal medium containing 5% sucrose supplemented with 0.0, 0.001, 0.01, 0.1 or 1.0 mg l(-1) BA, 0, 300, 600 or 900 mg l(-1) malt extract and 0.6 M sorbitol. The highest plating efficiency was obtained on MT basal medium containing 5% sucrose supplemented with 0.01 mg l(-1) BA and 600 mg l(-1) malt extract. MT basal medium containing 5% sucrose and supplemented with 0.01 mg l(-1) kinetin was found to be a medium suitable for the development of globular somatic embryos derived from protoplasts into heart-shaped somatic embryos with cotyledon-like structures. The highest percentage of shoot formation was obtained using 0.1 mg l(-1) GA3. A complete protoplast to-plant system was developed for C. schweinfurthii, which could facilitate the transfer of nuclear and cytoplasmic genes from this species into cultivated Citrus through protoplast fusion.