Legume Genomics and Genetics 2025, Vol.16, No.1, 11-22 http://cropscipublisher.com/index.php/lgg 12 Especially those SNPs (Single Nucleotide Polymorphisms), which can reflect the genetic characteristics of yield-related traits under both normal and drought conditions (Li et al., 2023). However, on the other hand, this technology is not omnipotent, but it does help researchers understand many genetic mechanisms of drought resistance (Huang et al., 2024). This research aims to thoroughly explore the secrets behind soybeans' drought resistance. To be honest, people engaged in breeding nowadays all know that relying solely on traditional methods is a bit insufficient. We are going to use the latest genotyping technology to identify all the key gene loci related to drought resistance of soybeans. Although the workload is not small, if a few useful candidate genes can really be found, it will be of great significance. Just think, nowadays the climate is getting more and more extreme. Drought-resistant soybean varieties are simply treasures. If these genetic mechanisms can be understood, perhaps good soybeans can be grown in arid areas in the future. Of course, this matter cannot be rushed. It has to be done step by step. However, it will definitely be helpful for ensuring food security. 2 Genetic Basis of Soybean Drought Resistance Traits 2.1 Complexity of drought resistance traits When it comes to soybean drought resistance, it is not just one or two genes the final say. Researchers have found that just one GWAS study identified 11 SNP loci and 22 QTLs, particularly the transcription factor GmNFYB17, which can both resist drought and increase yield (Sun et al., 2020). However, to be honest, this is just the tip of the iceberg-a study has discovered 75 and 64 drought resistance related QTLs in one go, and these loci explain many phenotypic differences (Wang et al., 2020). Even more exaggeratedly, someone compiled 73 studies and found 483 QTLs distributed in 393 different locations (Shook et al., 2020). You see, drought resistance is so complex, it all relies on a bunch of genes working together to create an expression regulation network. Although we have found many clues now, we are still far from fully understanding them. 2.2 Phenotypic characteristics of drought resistance traits To determine the drought resistance of soybeans, three key aspects need to be considered. Firstly, the root system characteristics-plants overexpressing GmNFYB17 are particularly interesting, with faster root development, significantly increased number of lateral roots, and significantly improved root shoot ratio (Sun et al., 2020). Of course, looking at the root system alone is not enough. The water retention capacity of leaves is also crucial, such as relative water content (RWC), SOD activity, and proline content, which vary significantly under drought conditions (Figure 1). When measuring these traits, it is usually necessary to set different water treatments and combine them with SNP markers for genetic analysis (Dhungana et al., 2021; Ouyang et al., 2022). When it comes to water use efficiency, although often overlooked, it is indeed one of the important indicators for evaluating drought resistance. 2.3 Genetic diversity of soybean drought resistance traits Let's do drought-resistant breeding for soybeans. It's actually quite interesting. Look at those local old varieties. Compared with the varieties promoted now, the drought resistance characteristics at the genetic level are really quite different (Wang et al., 2020). Although the exact details still need to be studied in detail, this difference might just be a breakthrough-by recombining genes from different sources, it might be possible to create new varieties that are more drought-resistant. When it comes to this, the soybean population in China is quite valuable for reference, as it contains many QTLS and candidate genes related to drought resistance. However, then again, it is not enough to just focus on a single study. The QTL data from different teams need to be integrated and viewed together (Hwang and Lee, 2019; Shook et al., 2020), in order to figure out the genetic pattern of drought resistance. Of course, this is easier said than done, but if it can be truly understood, it will definitely be a great benefit for cultivating drought-resistant soybeans. 3 Overview of Genome-Wide Association Studies (GWAS) 3.1 Principles and methods of GWAS When it comes to GWAS method, it is currently being used by breeding researchers. The principle is actually not complicated, it is to compare the genomic data of different individuals together to see which gene variations are
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