A high-quality chromosome-level wild rice genome of Oryza coarctata.

Oryza coarctata (2n = 4X = 48, KKLL) is an allotetraploid, undomesticated relative of rice and the only species in the genus Oryza with tolerance to high salinity and submergence. Therefore, it contains important stress and tolerance genes/factors for rice. The initial draft genome published was limited by data and technical restrictions, leading to an incomplete and highly fragmented assembly. This study reports a new, highly contiguous chromosome-level genome assembly and annotation of O. coarctata. PacBio high-quality HiFi reads generated 460 contigs with a total length of 573.4 Mb and an N50 of 23.1 Mb, which were assembled into scaffolds with Hi-C data, anchoring 96.99% of the assembly onto 24 chromosomes. The genome assembly comprises 45,571 genes, and repetitive content contributes 25.5% of the genome. This study provides the novel identification of the KK and LL genome types of the genus Oryza, leading to valuable insights into rice genome evolution. The chromosome-level genome assembly of O. coarctata is a valuable resource for rice research and molecular breeding.