Recombination and large structural variations shape the genomes of interspecific edible bananas.. BWW

Admixture and polyploidization are recognized as major processes of eukaryote genome evolution. However, knowledge of their impact on chromosome segregation is still limited. Many banana cultivars are triploid (sometimes diploid) interspecific hybrids between Musa acuminata (A genome) and M. balbisiana (B genome). They have no or very low fertility, are vegetatively propagated and were classified based on morphological characters as '€˜AB'€™, '€˜AAB'€™ or '€˜ABB'€™. We used NGS sequence data to characterize the A vs. B chromosomes composition of nine diploid and triploid interspecific cultivars, to compare chromosome structure between A and B genomes and to analyze A/B chromosome segregations in a polyploid context. We showed that interspecific recombination occurs frequently between A and B chromosomes. We identified two large structural variations between A and B genomes, a reciprocal translocation and an inversion, that locally affect recombination and lead to segregation distortions and aneuploidy in a triploid progeny. The interspecific recombination and large structural variations resulted in edible bananas having mosaic genomes. The unprecedented resolution in deciphering their genome structure, allowed us to start revisiting the origins of banana cultivars and will allow to explore breeding strategies with much more efficiency.