SOMATIC EMBRYOGENESIS IN Citrus sinensis, C. reticulata AND C. nobilis x C. deliciosa

Most of the plant regeneration processes in citrus, through tissue culture, involve indirect somatic embryogenesis. The optimization of these processes is important for the development of in vitro plant improvement and micropropagation studies. Studies to evaluate the effect of different carbohydrates in somatic embryogenesis were conducted using calli from ‘Ponkan’ mandarin (Citrus reticulata, Blanco), ‘Cravo’ mandarin (C. reticulata), ‘Itaboraí’ sweet orange (C. sinensis L. Osbeck.), ‘Valencia’ sweet orange (C. sinensis) and ‘Kinnow’ mandarin (C. nobilis Loureiro x C. deliciosa Tenore). The culture medium used was MT supplemented with sucrose, galactose, glucose, maltose or lactose with the following concentrations of 18, 37, 75, 110, and 150 mM. The culture medium used for the maturation of somatic embryos had 0, 15, 29, 44, 58 and 73 mM of sucrose, in presence or absence of 0.5 g L of activated charcoal. Seventy-three mM of sucrose with 0.1 mg L of GA3 in the presence or absence 0.5 g L –1 of activated charcoal was also tested. Overall, the carbohydrates galactose or lactose induced a higher number of somatic embryos. Sucrose concentrations of 58 and 73 mM generated a higher number of plantlets from mature embryos of ‘Ponkan’ mandarin and ‘Valencia’ sweet orange.