International Journal of Aquaculture, 2025, Vol.15, No.2, 76-87 http://www.aquapublisher.com/index.php/ija 82 5.3 GS cases of key traits (such as growth, disease resistance) Research on the application of genome selection technology in abalone is still in its infancy, but some cases of key traits have made encouraging progress. In terms of growth traits, some experts conducted genome-wide association analysis on the growth-related traits (shell length, shell width, total weight, etc.) of the wrinkle disc abalone population, and identified multiple significantly associated SNP sites and candidate genes. These growth-related markers explain a proportion of phenotypic variation that can be incorporated into the GS model to improve the accuracy of prediction of growth traits. In terms of disease-resistant traits, taking the common resistance to Vibriopathy as an example, domestic scientific research teams are building large-scale family lines and genotyping the activity, hoping to find molecular markers that resist disease and use them for GS model training. Referring to the successful experience of other aquatic animals, such as the anti-sea lice and anti-bacterial cold water disease traits of salmon, which have achieved a genetic gain of about 20% to 30% through GS, and the prospect of anti-disease GS of abalone is also widely optimistic (Zhao et al., 2023). Genomic selection has shown feasibility in response to environmental stress resistance traits. GS application of high-temperature traits is the most advanced: Liu et al. successfully bred a heat-resistant abalone breeding line using genome prediction, which not only verified the effectiveness of GS in this trait, but also provided an example for other stress-tolerant traits. In this study, they measured the heat-resistant phenotype (adhesion time under high temperature exposure) on 1120 tail wrinkle disc abalone and obtained approximately 64,788 high-quality SNP genotype data (Brokordt et al., 2017). The BayesB model constructed with these data has a prediction accuracy of 0.55 (GBLUP is 0.40), and the accuracy rate is further improved by selecting a significant SNP subset. The highly heat-resistant individuals selected from this are used for reproduction and the heat-resistant survival of their offspring is expected to be significantly higher than that of control systems without GS selection. 6 Practical Applications and Case Studies of Genomic Selection Breeding in Abalone 6.1 Comparative breeding strategies based on different germplasm backgrounds Abalone breeding strategies can vary based on different germplasm resources, primarily including three models: intra-population selection and improvement, hybridization among closely related species to develop new varieties, and distant hybridization to create heterosis. Intra-population selection relies on the genetic variation within the target species, using family selection to accumulate favorable alleles. Hybridization among closely related species utilizes genetic differences between geographical populations, with directional crosses to cultivate new varieties. A representative case is the "Xipan Abalone" bred by Xiamen University: this variety was developed by crossing the imported Japanese disk abalone (Haliotis discus discus) as the female parent with a selectively bred local Jinjiang line of the wrinkled disk abalone (Haliotis discus hannai) as the male parent. After four generations of selection, a new line was obtained that combined the superior traits of both subspecies while overcoming hybrid sterility and instability (Zhao, 2014). Distant hybridization-crosses between different species-has attracted significant attention in abalone breeding. It enables the realization of strong heterosis and breaks through the limitations inherent in the original species. The “Lüpan Abalone” is a successful example of such distant hybridization. It was developed by crossing a selectively bred line of H. discus hannai (wrinkled disk abalone) as the female parent with the introduced American green abalone (H. fulgens) as the male parent, and took 11 years of breeding efforts. This new variety combines the large body size of green abalone with the desirable meat flavor of H. discus hannai. Its growth size is more than double that of ordinary wrinkled disk abalone, with 30% of individuals exceeding 500 grams. It also demonstrates anincreasedheattoleranceof2.26 °Candanearlyhalvedfarmingcycle(Figure1)(Guoetal.,2023). This breakthrough enabled China to possess a domestically bred variety comparable to large abalones imported from South Africa and Australia. The main challenges of distant hybridization lie in reproductive isolation and offspring fertility. However, once successful, the resulting hybrids often carry trait combinations that are impossible to achieve through conventional breeding (Xiao et al., 2022). The development of the Lüpan Abalone
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