Breeding and Disease Resistance Evaluation of a New Largemouth Bass (Micropterus salmoides) Strain Resistant to Largemouth Bass Virus (LMBV)

Largemouth bass virus (LMBV) has caused severe impacts on the largemouth bass aquaculture industry in China. Breeding new virus-resistant strains is a fundamental strategy to address the LMBV challenge. In this study, a candidate LMBV-resistant population of largemouth bass was developed using the "Youlu No. 3" as the base population. Through three consecutive generations of selective breeding, a new LMBV-resistant strain was successfully established. To evaluate the LMBV resistance of different breeding generations, four key indicators, including survival rate post-LMBV infection, LMBV viral load, the expression of immune-related genes (GADD45b, FOXO3, TNF-α, IFN-γ, and IL-10), and antioxidant enzyme activities (GSH and AKP), were analyzed in this study. Notably, the F3 generation exhibited significantly lower viral loads in liver tissues after LMBV infection compared to the F1, F2, and control groups. Furthermore, the F3 generation showed a markedly higher survival rate at 14 days post-challenge, indicating enhanced disease resistance. Additionally, both the F2 and F3 generations had increased expression levels of the immune-related genes and elevated activities of antioxidant-related enzymes. These results collectively indicate that the F3 generation possesses stronger LMBV resistance than the F2, F1, and control groups. This study provides effective strategy for addressing LMBV disease in largemouth bass at the source and is of great significance for promoting the healthy and sustainable development of the largemouth bass aquaculture industry.