Micropropagação e embriogênese somática em variedades cultivadas de mandioca

Abstract

Despite the great importance of cassava ( Manihot esculenta ) , this crop still has some limiting factors regarding nutritional aspects, as well as its cultivation, because some varieties are quite affec ted by biotic and non biotic factors. Biotechnology has contributing with the use of different techniques, like micropropagation for the large plant production and somatic embryogenesis as a system of plant regeneration, a basic requirement to use the gen etic transformation techniques. This work aimed the evaluation of the ‘ in vitro ’ morphogenetic response and the induction of the somatic embryogenesis in cultivated varieties of cassava. After 30 days in the establishment medium, 92% of the meristems forme d plants that were subcultured three times in a multiplication medium. The best result was obtained with the Mocotó variety. The protocol used in this work was not efficient for the varieties Rose and Amansa Burro. For the study of the somatic embryogenesi s, stem apexes and young leaves of ‘ in vitro ’ cultivated plants of the Cigana Preta variety, cultivated in a induction medium supplemented with 2,4 - D or picloram, both in the concentrations of 8 and 12 mg L - 1 . The results showed that in a period of 30 days the explants formed callus, and that the induction of somatic embryos was influenced by the type and concentration of the plant regulators. There was significant difference among the auxins regarding the frequency of calluses with embryos and average numb er of embryos per explant, at the end of 75 days of induction. Two culture media were tested for the development of the embryos. Embryos at the cotyledonary stage were incubated in a germination medium constituted of MS salts and vitamins, 2 μM copper sulf ate, 2,4 g L - 1 of Phytagel ® , and 1,77 μM of BAP. In a minimum period of four weeks the regenerated plants were transferred to conventional medium for cassava multiplication.