In liquid medium colchicine treatment induces non chimerical doubled-diploids in a wide range of mono- and interspecific diploid banana clones

The worldwide production of banana and plantain, which is estimated to 106 Mt·year–1, relies on a narrow genetic basis. Thus, banana production is fragile regarding emergent diseases, and creation of new varieties of banana stands out as a real necessity for its sustainability. In banana, various improvement strategies aim to create triploid hybrids. The objective of this report is to present a simple in vitro methodology to induce stable tetraploid plants by colchicine treatment, usable as parent for obtaining triploid varieties. Materials and methods. Twenty-one diploid M. acuminata clones and three interspecific M. acuminata / M. balbisiana diploid clones were treated as proliferating culture in liquid medium with 1.25 mM of colchicine for 48 h. Plant screening has been performed by morphological identification in greenhouse, chromosome counts on root tips and flow cytometry on leave blades on vitroplants using propidium iodide staining. Results. Chromosome counts led to distinguish diploid and tetraploid plants but did not afford to detect chimeras. Flow cytometry allowed an early screening of a larger number of plants leading to detect rapidly chimerical plants. It was observed that some stable 2x / 4x cytochimeras are periclinal. Tetraploid clones were obtained with all diploid genotypes. General behaviour of tetraploids in the field was globally weaker than the corresponding diploids. Nevertheless, all the doubled-diploids flowered and crossed with diploid plants to obtain triploid progenies. Conclusion. This study has clearly shown that induction of stable doubled-diploid plants can be obtained from a wide range of genetically different bananas. These results open the way to the systematic use of doubled-diploids by banana breeding programs for the release of enhanced triploid varieties