EFFECTS OF GAMMA-RAYS DOSES ON SHOOT APEX OF BANANA (MUSA SP) PLANTS DEVELOPED IN-VITRO AIMING AT MUTATION-INDUCTION

Shoot tips from banana cv. Maca, were gamma-irradiated (20, 40, 60, 80 and 100 Gy) and subcultivated in vitro for 4 vegetative generations ( M1V4). Based on leaf variegation observed in vitro it was concluded th at M1V4 is the minimum number of generations to be used before the scr eening of mutants. At greenhouse, besides leaf variegation others phen otypic changes (anthocyanin, distrubed plant and leaf architecture) we re also quantified. The frequency of this variants increased with the dose, and, the treatment with 40 Gy produced the highest frequency of 13,49% while in control plants it was only 0.85. So, this dose is reco mmended to be applied in mutation breeding with this cultivar. Inocula tion of 2765 young plants were carried out in green-house with spores suspension of Fusarium oxysporum f. sp. cubense. No resistant plants w ere found, but this system permitted a quick and efficient screening o f the susceptible ones and can be utilized for the selection of the mu tants from big populations of banana cultivars.