Field evaluation of potential mutants obtained after gamma irradiation of banana and plantain (MUSA SPP.) shoot-tip and embryogenic cell cultures

Bananas and plantains provide an important carbohydrate source in the Cuban diet. Low yields and susceptibility to diseases (mainly black Sigatoka, caused by the fungus Mycosphaerella fijiensis) of current cultivars render the development of new varieties a high priority. Biotechnological and nuclear techniques have been successfully applied on shoot tips, resulting in the generation of improved cultivars. Potential induced mutants derived after gamma irradiation were tested in the field. A dwarf-like mutant of the cultivar 'Parecido al Rey' (clone V6-44) was obtained. Some mutants (Parecido al Rey variant 6-32 and 6-44 and Gran Enano variant 3-2) were selected for further field evaluation due to their tolerance to black Sigatoka disease, as well as their higher yield compared to non-irradiated control plants. These characters appeared to be unstable during following field cycles. To reduce the frequency of chimeras obtained after irradiation and to obtain a higher multiplication rate of irradiated samples, cell suspensions were established and used as starting material for mutation induction. The regeneration capacity of the established 'Navolean' cell culture was quantified. Homogenized samples of 500 mul cell suspension gave rise to between 1300 and 2650 embryos with a germination frequency of 20.7%. Percentages of survival ex vitro amounted to 95%. Field performance and genetic stability of plants regenerated from irradiated cell suspensions are currently under investigation.