EVALUATION OF POLLEN FERTILITY OF DIPLOID AND DOUBLED-DIPLOID CLONES OF MLALI AND THEIR POTENTIAL USE FOR BANANA BREEDING

Past phylogenetic studies pointed to some Mlali clones (AAcv) as the 2N gamete donor parents of ‘Cavendish’ (AAA) and ‘Gros Michel’ (AAA) cultivars, thus revealing their significance to Musa breeding. Nevertheless, cultivated bananas are usually highly sterile at diploid and triploid level, which seriously hampers the production of new hybrids. Therefore, it is necessary to investigate the floral biology of these Mlali clones to evaluate their capacity of generating such progenies. Pollen fertility of both diploid and doubled-diploid Mlalis (as donor of diploid gametes) was assessed by different approaches. At anthesis, the Alexander staining technique has revealed that up to 35% of haploid and diploid pollen were viable. Pollen viability was confirmed in test crosses with wild Musa accessions presenting no fertility problems. The results were then correlated with post-meiotic observations at the tetrad stage: 70% were regular tetrads in the diploid and doubled-diploid clones whereas the remaining cells were aggregated under forms of pentads and hexads and, more rarely, heptads leading probably to aborted microspores. Detailed observations of the irregular tetrads suggested that meiotic errors occurred during both first and second mitosis of the meiosis. These preliminary results suggest that doubled-diploid Mlali clones (AAAAcv) might be useful male parents with high breeding potential for the development of new disease-resistant AAA export bananas.