Near telomere-to-telomere genome assembly of the rainbow trout (Oncorhynchus mykiss)

Abstract

The rainbow trout (Oncorhynchus mykiss) exhibits extensive karyotypic diversity (2n = 58–64) driven by Robertsonian translocations, yet widely used reference genomes are derived from North American lineages, leaving Chinese aquaculture populations underrepresented. Here, we present a near telomere-to-telomere (T2T) genome assembly of a farmed rainbow trout from China. Integrating PacBio HiFi, ONT ultra-long reads, and Hi-C data, we assembled a 2.29 Gb genome with 99.04% anchored to 30 chromosomes. Notably, the genome contains only 18 gaps, with 16 gap-free chromosomes and 13 achieving T2T status. Comparative synteny analysis revealed a third chromosomal fission/fusion iteration in which Swanson Omy14 splits into Arlee Omy14 and Omy32. Annotation identified 43,137 protein-coding genes, with a BUSCO completeness of 98.9%. This dataset provides a valuable resource for resolving lineage-specific structural variation, supporting pangenome construction and facilitating molecular breeding in rainbow trout.