Insight into the mosaic structure of cultivated banana genomes

Cultivated bananas are derived from hybridization events between Musa species and subspecies that differentiated in various regions and archipelagos in South-East Asia. These hybridizations generated diploid and triploid inter(sub)specific hybrids with impaired fertility. Some of them, having seedless parthenocarpic fruits, were selected by humans and further dispersed through vegetative propagation. The genomes of these cultivated bananas are expected to have gone through few rounds of recombination and to be organized in a mosaic of large blocks of sequences from different ancestral origins. To characterize mosaic genome structures of diploid bananas, we generated a set of SNPs from RNAseq data. We applied multivariate (COA) and SNP clustering approaches to assign alleles to ancestral banana groups. Grouped alleles were then used to infer the ancestral origin of genomic regions for the selected diploid bananas. First results identified relatively simple mosaic structures for accessions resulting from two ancestral groups as well as more complex patterns involving more than two ancestors. In addition, at least one ancestral contributor to the studied cultivated bananas is still to be determined. Deciphering the mosaic structure of these genomes will improve our understanding of banana domestication, and help banana breeding programs in their strategies to reconstruct improved disease resistant hybrids. (Texte intégral