Legume Genomics and Genetics 2025, Vol.16, No.1, 11-22 http://cropscipublisher.com/index.php/lgg 17 6 Application of Genome-Wide Association Mapping in Soybean Drought Resistance Breeding 6.1 Marker-assisted selection (MAS) and improvement of drought resistance traits Nowadays, when it comes to drought-resistant breeding of soybeans, marker-assisted selection (MAS) has really been of great help. I remember that the study in 2020 was quite practical (Ren et al., 2020). They used SLAF-Seq technology to create a high-density genetic map, clearly marking all the QTLS related to drought resistance. This technology features high sequencing efficiency and relatively controllable costs, making it particularly suitable for breeding applications. With these precise molecular markers, breeding experts can screen out superior genotypes at the seedling stage, no longer having to wait until flowering and fruiting to make judgments as before, saving both time and effort. Although problems such as recombination rate and environmental interaction may still be encountered in actual operation, compared with traditional breeding methods, MAS has indeed accelerated the progress of drought-resistant variety selection and breeding significantly. The mark-assisted selection (MAS) technique works not only well on soybeans but also on other crops. As early as the 1990s, studies had already reaped benefits on common legumes (Schneider and Kelly, 1997), proving that this method was indeed effective in dealing with complex traits such as drought resistance. Later, around 2005, researchers found that the combination of MAS and traditional breeding was more effective (Francia et al., 2005; (Miklas et al., 2006), whether under normal or drought conditions, the output can be increased. Although there may be some differences among various crops, the molecular markers provided by GWAS have indeed saved breeding efforts a lot of detours. Ultimately, without the assistance of these markers, conducting drought-resistant breeding nowadays would be like walking in the dark, and the efficiency would be in a completely different league. 6.2 Application of genomic selection (GS) in drought resistance breeding Genomic selection (GS) has indeed gained popularity in the breeding circle in recent years, especially in dealing with complex traits such as drought resistance. It's quite interesting to say that it can be regarded as a golden pair with GWAS-by feeding the labeled data found by GWAS to the GS model, the prediction accuracy can improve significantly (He et al., 2014). The most remarkable aspect of this technology lies in the fact that it can estimate the breeding value based on whole-genome markers without waiting for the plants to grow up and exhibit traits. This trick was used in soybean breeding and the results were quite good. However, in actual operation, the debugging of model parameters and the marking density and other details are quite meticulous. But compared with traditional methods, it is indeed much more time-saving and labor-saving. Nowadays, more and more breeding projects are trying this approach. Although they are still in the exploratory stage, the prospects are indeed quite attractive. The combination of genomic selection (GS) and genome-wide association analysis (GWAS) has indeed sparked quite a few ideas. Especially when studying the drought resistance of soybeans, this combination approach is particularly effective-GWAS is responsible for extracting the key QTLS, and GS uses these data to build predictive models. The entire process is like an assembly line (Ren et al., 2020). Nowadays, with those high-throughput genotyping platforms and increasingly intelligent statistical models, the efficiency of finding drought-resistant loci has improved significantly. A study in 2021 proved this point (Hasan et al., 2021). Using GS to select drought-resistant genotypes is not only fast but also reliable in accuracy. Although the model training stage still requires some effort, once it runs smoothly, the breeding efficiency will increase visibly to the naked eye. Ultimately, this approach of integrated analysis has put molecular breeding on a fast track. 6.3 Potential of gene editing technology Gene editing technology has truly brought revolutionary changes to breeding work in recent years, especially CRISPR-Cas9, the "gene scissors", which are particularly convenient to use. In the past, when doing drought-resistant breeding, it took a lot of effort just to find the key genes. Now it's better. GWAS screens out the candidate genes first (Manavalan et al., 2009), and CRISPR can precisely operate on these genes. For instance, for genes related to drought resistance, if you want to enhance their expression, you can do so; if you want to knock
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