The formation of a new type of hybrid culter derived from a hybrid lineage of Megalobrama amblycephala (♀) × Culter alburnus (♂)

Abstract Distant hybridization is an important method for obtaining hybrids with hybrid genomes. In this study, a new type of hybrid culter (BTBT, 2n = 48) was produced by two rounds of backcrossing with an established hybrid lineage of blunt snout bream (Megalobrama amblycephala, BSB, 2n = 48, ♀) × topmouth culter (Culter alburnus, TC, 2n = 48, ♂). Analyses on DNA content, chromosome number, and fertility suggested that BTBT was a bisexual fertile diploid hybrid fish with 48 chromosomes. A survey regarding complete ITS1 of 45S rDNA revealed two types of ITS1 from different genomes (BSB and TC) and chimeric single nucleotide polymorphisms (SNPs) in the BTBT genome. Morphological trait data shown that BTBT was similar in appearance to TC but had a greater body width. Interestingly, the intermuscular bone (IB) count (127.9 ± 2.14) in BTBT exhibited an average 5.70% reduction compared with that (135.2 ± 2.45) in TC. The hybrid culter with improved characteristics provides a good model for producing new hybrid fish by distant hybridization, and the bisexual fertile hybrid culter is expected to serve as a new resource for fish genetic breeding.