Usefulness of embryogenic cell suspension cultures for the induction and selection of mutants in MUSA spp.

In bananas shoot-tip cultures are traditionally used for mutagenesis. The main problem with this type of culture is the presence of chimerism. In contrast, embryogenic cell suspensions allow the handling of large populations under controlled conditions and simultaneously avoid chimerism if embryos have a single-cell origin. In this study, we verified the unicellular origin of somatic embryos by treating embryogenic cell suspensions (ECS) with colchicine and determining the ploidy of regenerated plants by flow cytometry. We have found that none of the plants regenerated from colchicine-treated ECS was mixoploid (chimeric). To optimise a protocol for the irradiation of ECS, several experiments were performed. Flow cytometric analysis of cell-cycle kinetics proved to be more informative than growth curves for the determination of the optimal timing of irradiation. The optimal irradiation dose was determined using three different parameters. Among them, the fresh weight gain and the regeneration capacity indicated that the optimal irradiation dose lies between 50 and 75 Gy for embryogenic cell suspensions of both Williams (AAA) and Three Hand Planty (AAB plantain).