IMPROVEMENT OF SOMATIC EMBRYOGENESIS IN FEIJOA-SELLOWIANA BERG (MYRTACEAE) BY MANIPULATION OF CULTURE MEDIA COMPOSITION

Somatic embryos could be induced from the cotyledons of zygotic embryos from immature fruits of Feijoa sellowiana Berg (Feijoa) in the presence of a wide range of concentrations of fructose, glucose, maltose, and sucrose. Mannitol or sorbitol alone were ineffective. The highest frequencies of induction (99%) and the greatest number of somatic embryos per explant (134) were obtained with 0.4 M fructose and 0.3 M sucrose, respectively. This sucrose concentration also showed greater induction capacity than equimolar combinations of its monosaccharide constituents combined. Somatic embryo development was arrested at the globular stage at concentrations higher than 0.5 M of all the sugars tested. When transferred to solid germination medium containing 2.0 mg/liter (5.17 mu M) gibberellic acid, 0.5 mg/liter (2.32 mu M) kinetin, and 0.029 M sucrose, somatic embryos formed under 0.3 or 0.4 M sucrose had better germination capacity than those induced under lower (0.1 and 0.2 M) concentrations, as assessed by the frequency of explants presenting germinated embryos and by the number of plants obtained from those explants. On liquid media of similar composition somatic embryos did not germinate. Our data suggest that high (0.3 to 0.4 M) carbohydrate levels improve somatic embryogenesis by acting both as carbon source and as osmotic regulator.