INDUCTION OF HIGH-FREQUENCY SOMATIC EMBRYOGENESIS IN GERANIUM (PELARGONIUM X HORTORUM BAILEY CV RINGO ROSE) COTYLEDONARY CULTURES

The cv Ringo Rose of hybrid seed geranium (Pelargonium x hortorum Bail ey), previously shown to be recalcitrant in culture, produced somatic embryos when cotyledonary explants were cultured on regeneration mediu m containing thidiazuron (TDZ), forchlorfenuron (CPPU), or a combinati on of indole-3-acetic acid and N-6-benzylaminopurine (IAA+BAP). Amendm ent of the basal medium with TDZ (0.5 mu M) was the most effective tre atment. Addition of amino acids to the medium promoted the growth of s omatic embryos. Retention of the proximal region of the cotyledon was crucial for regeneration, but the removal of the distal 1/3 to 1/2 cot yledon had no significant effect on somatic embryogenesis. Cotyledonar y explants formed somatic embryos in higher frequency and much earlier than hypocotyl explants cultured on the same medium. The somatic embr yos induced on cotyledonary explants were germinated on basal medium. More than 70% of the somatic embryos were converted into plants and tr ansferred to soil.