Contribution bias of parental genomes to the hybrid lineages of black Amur bream and topmouth culter revealed by low-coverage whole-genome sequencing.

Interspecific hybridization has the potential to increase animal genetic diversity, enable the introgression of advantageous genetic variation, and even create hybrid lineages. Using the low-coverage whole-genome sequencing data of black Amur bream (Megalobrama terminalis [SJ]), topmouth culter (Culter alburnus [QZ]), and their hybrid progeny, we focused on the sequence variation and contribution bias to the genomic composition of the hybrid lineages of SJ♀ × QZ♂ [ZJ] and QZ♀ × SJ♂ [FJ]. Both mash-based genetic distance analysis and variant analysis based on various reference genomes revealed that the hybrid lineages' genomes are more prone to QZ composition. Furthermore, we assess the degree of subgenomic intermixing between parents QZ and SJ in the FJ and ZJ hybrid lineages. In the Jaccard index-zero genomic area, 89.41% of the genomic region in ZJ and 90.23% in FJ are entirely from one of the parental genomes. This genomic area is primarily from QZ, regardless of FJ or ZJ. In FJ, the proportion is 55.70%; in ZJ, the proportion is 54.60%. Using the reference-free variant discovery tool, we identified two InDel markers (Both were SSR-type InDel markers) and one (T/A)-type SNP marker that displayed differences in agarose electrophoresis. Our current findings suggest that parental genomic contribution bias leads to an imbalance in the genomic composition of hybrid lineages. The genomic composition bias is connected to species but not maternal effects, giving insights into the development of vertebrate genomes shortly after hybridization.