Advances in genomics: applications to banana breeding

Like many vegetatively propagated crops, most cultivated bananas are highly heterozygous polyploids of mono or interspecific constitution. During human selection for edibility over thousands of years, Musa cultivars developed a particularly high level of male and female gamete sterility associated with a low fertilizing potential making genetic recombination through meiosis and hybridization rare events during domestication. Recent evolutionary studies in Musa suggest that only a few hybridization events occurred from the wild seedy primitive ancestors to the most evolved present day cultivars. Unlike other crops, in such a context where the species complex is nearly fixed, banana breeding relies on strategies where an extremely limited number of crosses are possible. Several genomic tools are now being used to decipher the complexity of the Musa genepool. Molecular markers can distinguish between genotypes and have provided a clear understanding of banana domestication suggesting only a few hybridization events from the wild seedy primitive to the present day cultivars. This allows us to build breeding schemes mimicking the sequence of crossings and selections that occurred over several millennia. The Musa genome can now be explored for desirable genes and subsequent marker-assisted selection. For banana improvement, this approach is particularly important in a biological context of gamete sterility (and difficulties to get large quantities of seeds) for which recombination and implementation of introgression strategies remain the greatest challenge.