Abstract
Crossbreeding is a traditional breeding technique and has been performed successfully in many fish species. However, distant hybridization between different genera is hard to be successful because of reproductive isolation. In this study, diploid hybrids (PL) were successfully derived from the hybridization of Ussuri catfish (Pseudobagrus ussuriensis, PU, ♀, 2n = 52) and longsnout catfish (Leiocassis longirostris, LL, ♂, 2n = 52). And the morphological data, external frame parameters, chromosomal karyotypes, DNA content measurement, mitochondrial DNA control region, and species-specific marker identification were applied to investigate the traits and genetic characterization of the PL hybrid offspring and their parents. Both quantifiable traits and shape frame parameters of the PL hybrid offspring were revealed to be intermediate between those of their parents; however, cluster analysis showed that their external morphology was more in favor of the maternal PU. The growth comparisons showed that the hybrids had significant growth advantages over maternal PU. Based on karyotype patterns, DNA contents and mitochondrial DNA, the hybrid origin and maternal inheritance of hybrid offspring were further confirmed. According to the sequence variations identified from the genome sequences of the two catfish species, one species-specific marker was developed to distinguish the PL hybrid offspring and their parents. Therefore, this study provides a successful case for intergeneric hybridization and hybrid superiority, and the PL hybrid shows promise for commercial application, pending further studies into its husbandry, health, and welfare with larger populations of fish.