Genetic diversity and breeding efficiency of a salt-tolerant strain of largemouth bass (Micropterus salmoides) revealed by microsatellite analysis and phenotypic evaluations

To address the underuse of saline-alkaline water and the shortage of suitable aquaculture species, a salt-tolerant strain of largemouth bass was developed through multigenerational selection. In this study, the genetic structure of two base populations and three successive generations (F3-F5) was analyzed using microsatellite markers. Results showed the observed heterozygosity (Ho) ranged from 0.357 to 0.524, the expected heterozygosity (He) from 0.410 to 0.509, and the polymorphism information content (PIC) from 0.3591 to 0.4593, suggesting a moderate genetic diversity across generations. The Fst value between generations ranged from 0.009 to 0.037, indicating weak genetic differentiation among populations. AMOVA analysis revealed that 95% of the genetic variation occurred within populations. Both the UPGMA dendrogram and the structure analysis grouped the different generations into four clusters. Phenotypic evaluation confirmed the selected strain's enhanced salinity tolerance, exhibiting significantly lower 96 h mortality when challenged at 12ppt and 14ppt. Furthermore, growth rates of salt-tolerant strains (F4 and F5) improved by 19.52% and 26.50% compared to control after 120d saline culture (8ppt). In conclusion, this study indicates successful breeding of a salt-tolerant largemouth bass strain that maintains genetic diversity while exhibiting enhanced salinity tolerance and growth, providing useful insights for further genetic improvement in saline aquaculture.