Résumé
Musa beccarii is a precious ornamental banana species. It is the only species with a basic chromosome number of x=9 (2n=2x=18) in Musa genus, a number shared with the sister genera Ensete and Musella, while other Musa species are x=7, 10 or 11. Moreover, there are two sections in Musa. M. beccarii is in Callimusa section, while current assembled Musa genomes are in Musa section. To better understand genome evolution in Musaceae, we generated a high-quality chromosome-scale genome assembly of M. beccarii. M. beccariigenome was assembled by long read and Hi-C sequencing, with gene annotations using both long Iso-Seq and short RNA-seq reads. M. beccarii displayed the largest genome size, ~570 Mbp, among known Musaceae genomes, which was attributed to transposable element expansion and amplification of 45S rDNA sites. Regardless of chromosome numbers, we detected extensive genome-wide chromosome fusions and fissions between M. beccarii and the other Musa and Ensete species by synteny analysis. Within Musaceae, M. beccarii showed a reduced number of terpenoid synthase genes which are related to chemical defense and enrichment in lipid metabolism genes linked to the physical defense of the cell wall. Furthermore, type III polyketide synthase (T3PKS) was the most abundant biosynthetic gene cluster in M. beccarii with no conservation in the other Musaceae genomes. M. beccarii, as the first chromosome scale genome sequenced in the Callimusa section in Musa , provides an important resource for further understanding of evolutionary mechanisms in the Musaceae and adds to knowledge of the pangenome.