Duplicação cromossômica e conservação de cultivares de bananeira in vitro

Abstract

With the present work, we aimed at evaluating the effect of colchicine over the duplication of chromosomes in “Ouro” banana explants and analyze the effect of different osmotic regulators (sucrose, sorbitol and mannitol) in the in vitro conservation of Grande Naine, Perciosa and Princesa banana explants. We used banana cultivars pre-established in vitro, provided from Embrapa Mandioca e Fruticultura Tropical, as explant source. Colchicine was used in the concentrations of 0, 0.5, 1.0, 1.5 and 2.0 mg L-1 in MS medium, and the plants were maintained in the dark for 2, 4, 8, 16 and 32 days. The experimental design was completely randomized, in a 5x5 factorial scheme (5 doses of colchicine and 5 exposition periods). By means of flow cytometry analysis we observed that 379 (58.3%) of the explants survived the induction of the in vitro chromosome duplication, especially in the gentler treatments. We obtained 18 tetraploid plants (4.7%), 72 mixoploid (19.1%), 5 plants presented DNA content superior to that of the tetraploid plants (1.3%), 6 aneuploids (1.6%) and 278 remained diploid (73.5%). The period of 2 and 4 days were the treatments that presented higher number of plants with doubled genetic material, having no significant difference between the concentrations of colchicine. In the in vitro conservation, the osmotic regulators were used on the concentrations of 20 and 40 g L-1, being added to the MS culture medium, and the explants remained conserved in vitro for 160, 260 and 360 days. The experimental design was completely randomized, in a 3x3x2 factorial scheme (3 banana cultivars, 3 sources and 2 concentrations of carbon). Subsequently, we inoculated in MS culture medium, evaluating the responsive capacity of the cultivars after 45 days. In the presence of sorbitol, the explants presented favorable results to the growth suspension during the in vitro conservation without presenting greater loss in the survival and resume of growth in vitro.