Legume Genomics and Genetics 2024, Vol.15, No.4, 187-198 http://cropscipublisher.com/index.php/lgg 191 4 Genetic Diversity in Domesticated Legumes 4.1 Genetic variation within and between species Genetic diversity in domesticated legumes arises from various sources, including wild relatives, landraces, and exotic germplasm. Wild relatives, in particular, harbor a wealth of genetic variation that has been shaped by natural selection in diverse environments. This genetic reservoir is crucial for introducing novel traits into domesticated species (Coyne et al., 2020; Pratap et al., 2021). Additionally, the use of molecular markers such as microsatellites has revealed significant allelic diversity within legume species, indicating a relatively wide genetic base (Smýkal et al., 2015). Population genetics studies have been instrumental in assessing the genetic diversity within and between legume species. For instance, the use of SSR markers in Vigna stipulacea has shown high genetic diversity among accessions, which is essential for breeding programs. Similarly, genome-wide analyses of common bean have identified distinct genetic pools resulting from independent domestication events, highlighting the genetic differentiation within the species (Schmutz et al., 2014). 4.2 Role of genetic diversity in crop improvement Breeding strategies that leverage genetic diversity are vital for crop improvement. Introgression breeding, which involves the incorporation of genes from wild relatives into domesticated species, has been successful in developing improved cultivars with enhanced traits such as disease resistance and stress tolerance (Figure 3) (Pratap et al., 2021). The use of pre-breeding programs to develop new gene pools with a broad genetic base is also crucial for the genetic enhancement of grain legumes (Sharma et al., 2013). Conserving genetic diversity is essential for sustainable crop improvement. Ex situ and in situ conservation methods are employed to preserve the genetic resources of wild relatives and landraces. These conserved genetic resources serve as a reservoir for future breeding efforts, ensuring the availability of diverse alleles for crop improvement (Coyne et al., 2020; Ambika et al., 2022). 4.3 Comparative analysis of genetic diversity in wild and domesticated legumes Domestication bottlenecks have led to a significant reduction in genetic diversity in domesticated legumes compared to their wild counterparts. This loss of diversity is attributed to the selection of specific traits during domestication, which narrows the genetic base of cultivated species (Ambika et al., 2022). For example, the domestication of common bean involved two independent events, each resulting in a distinct genetic pool with limited shared genetic material (Schmutz et al., 2014). Gene flow between wild and cultivated populations can introduce new genetic variation into domesticated species, enhancing their adaptability and resilience. Hybrid populations created through the introgression of wild alleles into cultivated backgrounds provide valuable genetic resources for breeding programs (Coyne et al., 2020; Pratap et al., 2021). This gene flow is facilitated by the use of modern genomics and systematic phenotyping, which help identify and harness beneficial alleles from wild relatives. In summary, understanding and leveraging genetic diversity in domesticated legumes is crucial for crop improvement. By utilizing genetic resources from wild relatives and employing advanced breeding strategies, it is possible to develop cultivars with enhanced traits and ensure the sustainability of legume crops (Kreplak et al., 2019; Gore et al., 2022). 5 Case Study: Genetic Diversity and Phylogenetics of Common Bean (Phaseolus vulgaris) 5.1 Importance of common bean as a global food source The common bean (Phaseolus vulgaris L.) is a crucial legume crop globally, serving as a fundamental source of protein, particularly in rural societies. It is the most important grain legume for human consumption and plays a significant role in sustainable agriculture due to its ability to fix atmospheric nitrogen (Scarano et al., 2014; Schmutz et al., 2014; Assefa et al., 2019). In regions like Southern Italy and Brazil, common bean cultivation is integral to local economies and diets, highlighting its importance as a staple food (Burle et al., 2010).
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