Legume Genomics and Genetics 2025, Vol.16, No.3, 100-107 http://cropscipublisher.com/index.php/lgg 102 and water-deficient conditions. For example, the number of seeds per plant and the number of pods per plant are often used as key indicators for variety selection (Balko et al., 2023). Now, scientists have also found many stress-related genes through transcriptome and physiological experiments. These genes are important for breeding varieties that are resistant to harsh environments and can also have high yields (Araújo et al., 2015; Abdelrahman et al., 2018). 3.3 Physiological efficiencies: nitrogen fixation and source-sink relationships In order for leguminous plants to have high yields, they must not only grow fast, but also have "high internal efficiency". A key point is that they can coexist with rhizobia to fix nitrogen in the air, which not only helps their own growth, but also improves the soil and reduces the use of chemical fertilizers. After producing nutrients, plants need to transport these "goods" reasonably to leaves, roots, seeds and other places. Whether this distribution is efficient is directly related to whether more biomass and seeds can be produced. The structure of the roots, water use efficiency, and photosynthesis ability are also very important (Duc et al., 2015; Sofi et al., 2021). Current breeding work is also paying more and more attention to these "invisible" physiological traits. Scientists hope to select new leguminous varieties that are both high-yielding and use fewer resources by integrating these characteristics (Dutta et al., 2022). 4 Utilization of Germplasm in Breeding Programs 4.1 Trait introgression from exotic or wild donors In breeding, scientists often introduce wild relatives, local varieties or exotic species into excellent legume crops. This practice is called gene introgression breeding. Doing so can bring new genetic variation, help us improve varieties, improve disease resistance, drought tolerance, and yield. There are many successful examples, such as hybridization with wild or exotic species to breed better chickpeas, pigeon peas, peanuts, lentils, mung beans, urdu beans and kidney beans. These varieties not only grow better, but are also more disease-resistant and stress-resistant. In order to transfer these complex traits faster, many people now use some "specially designed" breeding populations in combination with new tools such as molecular markers. These methods can reduce the problem of unwanted traits being transferred in together. Now, gene introgression breeding has become a common method for improving legume crops (Sharma et al., 2013; Pratap et al., 2021; Gore et al., 2022). 4.2 Development of pre-breeding lines and core collections In the early stages of breeding, researchers will first introduce excellent genes from wild species or local varieties, and then introduce them into those strains that are more suitable for breeding. This step can solve the problem of incompatibility during hybridization and avoid bringing in some unwanted traits. They will first collect a lot of germplasm materials, then evaluate and screen them one by one, and finally establish a core germplasm bank. This germplasm bank retains many useful genes and alleles for subsequent breeding. Taking cowpea breeding as an example, the core germplasm has helped us find a lot of good materials with potential. These resources are also critical because they can support subsequent improvement work and help varieties better adapt to different environments (Egan et al., 2021; Gayacharan et al., 2023; Chaudhary et al., 2025). 4.3 Marker-assisted and genomic selection approaches Now many breeding projects have begun to use some modern methods, such as marker-assisted selection (MAS), marker-assisted backcrossing, and genomic selection. These methods can speed up the process of finding good traits and breed new high-yield and disease-resistant varieties more quickly. With high-density genetic maps, complete genomic information and molecular markers, we can more accurately find the genetic locations (QTLs) related to yield, disease resistance and stress tolerance, and then transfer them to the target varieties. GWAS (genome-wide association analysis) and next-generation sequencing can also enable us to improve the entire population faster and achieve continuous genetic progress. Now we can also combine omics technology and artificial intelligence to more efficiently explore traits and assist decision-making, thereby supporting the breeding of high-yield and stress-resistant legume varieties (Varshney et al., 2018; Singh et al., 2021; Jha et al., 2022; Biswas et al., 2023).
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