Legume Genomics and Genetics 2025, Vol.16, No.1, 11-22 http://cropscipublisher.com/index.php/lgg 15 There have been some new discoveries recently regarding the study of soybean drought resistance. There is an interesting paper in 2023 (Li et al., 2023), which found that genes BAH1 and WRKY11 are crucial, especially the E3 ubiquitin protein ligase and transcription factor, which seem to play a significant role in plants' response to drought stress. However, if there are many types of genes, we still need to look at the 2022 study (Ouyang et al., 2022), which identified nine candidate genes alone. Among them, NAC and GATA transport factors are particularly noteworthy, as they seem to regulate gene expression under drought conditions. To be honest, it is particularly important to understand the functions of these genes, after all, the cultivation of drought resistant soybean varieties now relies on these discoveries, although the specific application still needs to be explored. 4.3 Gene-environment interactions on drought resistance traits When it comes to the application of GWAS, it was recently discovered that it can also study the "tug-of-war" between genes and the environment. There was an interesting study in 2022 (Yu et al., 2022), which used a model called 3VmrMLM to analyze tocopherols in soybean seeds. As a result, 57 QTLS were identified. Even more interestingly, 13 QTLS were found to "interact" with the environment-genes close to these loci were particularly susceptible to environmental influences. This doesn't mean that when conducting GWAS analysis, it's really not advisable to ignore environmental factors. However, there are exceptions. A study using the RIL population in 2021 found (Dhungana et al., 2021) that the positions of many drought-resistant QTLS completely coincided with those previously reported, indicating that these sites are particularly "stubborn" and remain stable regardless of how the environment changes. The recent research is quite interesting. Whether under normal watering or drought conditions (Li et al., 2023), some QTLs are particularly "stubborn" and can be detected in both environments. This indicates that these loci may be inherently stable and not affected by the environment. However, on the other hand, QTLs and genes that interact with the environment are more worthy of attention, as soybeans in reality have to face various complex situations. By understanding these, perhaps a new variety that is both drought resistant and high-yielding can be cultivated, although it is easier said than done. 5 Successful GWAS Cases in Soybean Drought Resistance Traits 5.1 Mapping of root development-related QTLs and breeding applications When it comes to drought resistance of soybeans, the characteristics of their root systems are truly a major discovery. Look at that GmNFYB17 gene (Sun et al., 2022). After it was transferred into soybeans and overexpressed, the effect was particularly obvious-the root system grew fast and abundant, the lateral roots were dense, and the drought resistance was immediately enhanced. This gene is quite interesting. It was discovered through GWAS combined with linkage analysis, which can be said to have utilized the advantages of both methods. In fact, as early as 2019, studies noticed the importance of root systems (Khan et al., 2019), and they found 46 new QTLS in a semi-identical population at one go, all of which controlled plant length and dry weight. After organizing these QTLS into an allele matrix, it is particularly helpful for drought-resistant breeding, although the specific application still depends on the actual situation. Ultimately, to cultivate drought-resistant soybeans, merely focusing on the above-ground parts is not enough; the underground root system is the key. 5.2 Discovery and validation of water use efficiency (WUE)-related genes When it comes to the water use efficiency of soybeans, GWAS has been a great help. A study in 2023 was quite interesting (Li et al., 2023), which identified several particularly stable QTLs that can affect yield traits such as pod number and biomass under both normal watering and drought conditions. More importantly, Glyma.19G211300 genes were discovered, which encode proteins directly related to stress response-although the specific mechanism still needs further research. These findings provide new ideas for cultivating water-saving and drought resistant varieties. In fact, as early as 2020, researchers used SLAF sequencing to create an ultra-high density genetic map, mapping QTLs that control plant height and grain weight (Ren et al., 2020). Now breeding experts can directly use these linkage markers for assisted selection, greatly accelerating the breeding progress of drought resistant varieties, but the actual operation still depends on specific environmental conditions.
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