International Journal of Molecular Zoology, 2025, Vol.15, No.1, 38-47 http://animalscipublisher.com/index.php/ijmz 39 high-resolution genomic tools, the work of locating quantitative trait loci (QTLs) and candidate genes is also more complicated (Ai et al., 2023; Wu et al., 2023). This study focuses on the rapid growth trait of grouper, and attempts to find the key influencing factors from the perspective of genetic regulation. High-density genetic maps, GWAS and a new generation of typing technology provide data support and decision-making basis for marker-assisted selection and genomic selection in actual breeding. The study found that compared with traditional methods, this type of strategy emphasizes efficiency and accuracy, and is particularly suitable for solving bottleneck problems such as long breeding cycles and complex target traits. Through these technical means, it is expected to accelerate the pace of breeding of high-quality grouper varieties and lay a more solid foundation for the sustainable development of the aquaculture industry. 2 Overview of Growth Traits in Grouper 2.1 Biological basis of growth in grouper The growth of grouper cannot be explained by a single gene or pathway. It is affected by multiple factors such as genetic background, hormone regulation and nutritional status. In recent years, QTL positioning and transcriptome studies have found a number of genes closely related to growth, mainly involving metabolic pathways, RNA transport, PPAR signaling and carbon metabolism (Wu et al., 2023; Wang et al., 2023a). These functions are closely related to cell proliferation, signal transduction and bone development. For example, genes such as npy2r (neuropeptide Y receptor Y2) and bmp2k have been found to be related to bone formation, energy metabolism and growth rate, reflecting that endocrine and nutritional factors play an important role in the entire growth process (Yu et al., 2018; Yang et al., 2020). Environmental factors such as temperature and nutritional conditions also affect the growth rate and developmental pattern of groupers. For instance, growth models fitted at the juvenile and juvenile stages showed that the growth characteristics of groupers can show exponential or decelerating changes depending on different environmental conditions and species or hybrid types (Sun and Wang, 2024). Another study pointed out that 30 °C is the optimal temperature for hybrid groupers (such as E. fuscoguttatus× E. lanceolatus), and its specific growth rate (SGR) is as high as (16.25 ± 2.11)%/day (Das et al., 2022). These research results emphasize that the combined effects of genetic and environmental factors on growth performance must be considered in breeding programs. 2.2 Key phenotypic indicators of fast growth Phenotypic indicators such as body weight, body length, body height and specific growth rate are usually used to evaluate the growth performance of grouper (Ai et al., 2023; Sun and Wang, 2024). Genome-wide association analysis and quantitative trait loci (QTL) mapping studies have found multiple single nucleotide polymorphism (SNP) sites and QTLs associated with these traits, and these genetic loci can explain a significant proportion of phenotypic variation (Yu et al., 2016; Yang et al., 2020; Wu et al., 2023). How much muscle a grouper can build and how well it turns feed into growth are also key signs of fast growth. Researchers have found several important genes that play roles in muscle growth, metabolism, and cell division. These genes are seen as likely candidates that affect these traits. Because of this, they can be used as helpful markers when choosing fish for breeding (Wu et al., 2023; Wang et al., 2023a). 2.3 Intraspecific variation and trait heritability By using high-density SNP typing and building linkage maps, the study showed that there is clear genetic difference both between and within grouper populations (Hsu et al., 2021). In research on red-spot grouper (Epinephelus akaara), Wang et al. (2019) created a detailed genetic map that was 2 300.12 cM long and included 3 435 SNP markers. The average distance between markers was 0.67 cM. They found 17 QTLs related to growth, which explained between 10.7% and 12.9% of the differences in traits. The heritability of growth traits in grouper is medium to high. Some QTLs and SNPs that have been found can each explain up to 12.56% of the differences seen in a single trait (Yang et al., 2020; Ai et al., 2023; Wu et al.,
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