Animal Molecular Breeding, 2025, Vol.15, No.2, 82-90 http://animalscipublisher.com/index.php/amb 86 Microsatellite markers for association with disease resistance have, for instance, been developed in tilapia lines and can predict offspring survival before challenge by pathogens, thereby enabling non-lethal and effective selection (Chen et al., 2021). In sex control, operations use sex-linked DNA markers to detect and select YY supermales or genetic male tilapia, whose multiplex PCR and high-throughput genotyping platforms are utilized to genotype broodstock rapidly and build stable selection systems (Figure 2) (Chen et al., 2018; Sultana et al., 2020; Wu et al., 2021; Tao et al., 2022). These types of systems are so advanced that information about markers is included in breeding choices to an extent that only individuals with a positive genotype are promoted in the breeding plan (Chen et al., 2021; Wang and Chen, 2024). Figure 2 Marker-assisted selection of disease-resistant tilapia (Adopted from Chen et al., 2021) 5.2 Validation of marker effects and evaluation of selection efficiency Marker effects are confirmed through controlled crossing tests and progeny testing to ascertain that the selected markers are linked to the target characters. For instance, MAS-selected YY supermales have been reported to sire offspring with male proportions of over 94% and significantly increased growth rates, and MAS for disease resistance has resulted in offspring with mortality levels of less than 1% compared to over 70% in susceptible lines (Chen et al., 2018; Vela-Avitúa et al., 2023). MAS effectiveness is further observed by the ability to predict offspring performance for properties from parental genotypes and by obtaining high concordance when validated markers are applied between populations and environments (Sultana et al., 2020; Chen et al., 2021; Curzon et al., 2021; Tao et al., 2022). 5.3 Integrated application strategies of mas and conventional family selection Blending MAS with conventional family selection methods maximizes genetic gain without losing genetic diversity. MAS is utilized early and accurately to select individuals with desirable alleles, whereas conventional family selection techniques are utilized to induce overall performance and versatility (Sultana et al., 2020; Curzon et al., 2021; Tao et al., 2022). This combined approach is particularly valuable for polygenic traits regulated by numerous genes since it applies phenotypic and molecular data together to increase the precision and efficacy of selection. Use. of MAS in Charm. with family selection has also been found to be effective in the production of all-male and disease-resistant tilapia and has thereby established its usefulness for commercial breeding (Chen et al., 2018; Curzon et al., 2021; Wu et al., 2021; Tao et al., 2022). 5.4 Trait improvement performance in advanced generations and industrial promotion prospects MAS-bred tilapia lines have exhibited higher growth rates, higher yields, better disease resistance, and better sex control in later generations than traditionally bred counterparts. Such improvements are equivalent to improved
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