## 2 Selective Breeding Strategies for Large Yellow Croaker Seedlings
### Disease Resistance Selection  
Disease resistance selection has become a key strategy for improving the aquaculture efficiency of large yellow croaker (_Larimichthys crocea_) and ensuring the sustainable development of the industry, receiving widespread attention in recent years. Due to the constraints of high-density farming practices, disease issues have become increasingly severe, with pathogens spreading rapidly and exhibiting high mortality rates, which severely restrict the stable development of the industry. Therefore, improving the disease resistance of large yellow croaker populations has become one of the primary focuses of current breeding efforts [29]. At present, genetic improvement of disease resistance traits in large yellow croaker is mainly based on traditional phenotypic selection, with the gradual incorporation of modern breeding technologies such as marker-assisted selection (MAS) and genomic selection (GS) to improve the efficiency and precision of disease resistance breeding [30]. With the development of functional genomics and high-throughput sequencing technologies, theoretical support for understanding the genetic basis of complex disease resistance traits has been provided. Researchers have identified multiple key genetic loci associated with disease resistance through quantitative trait loci (QTL) mapping and genome-wide association studies (GWAS), and have combined single-nucleotide polymorphism (SNP) and microsatellite markers to screen for disease-resistant individuals [31]. Additionally, genetic databases constructed from large-scale whole-genome resequencing data have provided important data support for the development of breeding chips, significantly improving trait identification and selection efficiency. Currently, disease resistance assessments for major pathogens such as Vibrio alginolyticus and Iridovirus have been widely applied in breeding practices, and related functional gene research has made significant progress. [PERSON] et al. [32] studied the autophagy-related gene ATG10 in large yellow croaker, discovering that its expression was significantly upregulated under viral infection stress, and its overexpression in vitro effectively inhibited viral replication, indicating its important role in antiviral immune responses. Additionally, [PERSON] et al. [33] identified Bacillus amyloliquefaciens NB Lm36, which exhibited broad-spectrum antibacterial activity. This strain showed significant inhibitory effects against multiple aquatic pathogens and was non-toxic to the large yellow croaker, indicating its potential as a biocontrol agent. In the application of disease resistance breeding, the \"Ningxin\" series breeding chips developed by [PERSON]'s team at Xiamen University integrate molecular markers for multiple traits, and based on this, the \"Ningkang No. 1\" strain, with significantly enhanced disease resistance, was successfully bred. This provides valuable germplasm resources and efficient technical means for disease resistance breeding of large yellow croaker [34], with genomics-assisted breeding technologies offering multiple approaches to cultivating disease-resistant fly (Figure 2). Figure 2: Workflow of genomics-assisted breeding for disease-resistant fish [35;36]. Notes: Collection of target fish germplasm resources for genomic and population sequencing to identify bacterial/viral/parasitic disease resistance traits. Process and key elements of genomics-assisted breeding technology, including marker-assisted selection, genomic selection, genome editing and transgenesis. Selection of optimal parents based on the results of the analyses and selection of disease-resistant varieties. Although significant progress has been made in disease resistance breeding for the large yellow croaker, several challenges remain. These include the diversity and variability of pathogen spectra, the complex genetic basis of disease resistance traits, and gene-environment interactions (G \(\times\) E) [29].