Induction and verification of autotetraploids in diploid banana (Musa acuminata) by in vitro techniques

Flow cytometry and stomata characteristics were used for screening ploidy levels in a large population of in vitro induced autopolyploids of the Musa acuminata breeding clone SH-3362. Culturing shoot tips in liquid medium supplemented both with 5.0 mM colchicine for 48 hours or 30 mu M oryzalin (3,5-dinitro-N4,N-dipropylsulphate) for seven days, both in combination with 2% (v/v) DMSO, resulted in a high (23.1% and 29.1%) frequency of non-chimeric tetraploids in the fourth vegetative generation. Although mixoploidy persisted in subsequent cycles of vegetative propagation, tetraploids as identified by flow cytometry remained solid non-chimeric during two more cycles. These autotetraploids were propagated for field testing. A rough pre-selection of regenerated V4 plants based on their stomata characteristics resulted in a population in which only 56.2% of the plants were solid tetraploids. The somatic polyploidization system reported here can be utilised for banana breeding programmes.