Maize Genomics and Genetics 2024, Vol.15, No.2, 80-92 http://cropscipublisher.com/index.php/mgg 82 Genetic analyses have demonstrated that maize possesses high levels of allelic variation, particularly between different landraces and wild relatives such as teosinte. This variation is evident in traits related to yield, disease resistance, and environmental adaptability (Doebley, 1990). The genetic diversity within maize is essential for maintaining its resilience against pests and diseases, such as Maize Lethal Necrosis Disease (MLND), which poses a significant threat to maize production in regions like Eastern Africa (Ndakidemi et al., 2016). Furthermore, genetic diversity is vital for ongoing breeding programs. By utilizing the diverse genetic pool available in both cultivated and wild maize populations, breeders can develop varieties that are more productive, nutritionally enhanced, and better suited to specific growing conditions. This genetic richness provides the foundation for future improvements in maize, ensuring the crop remains viable and productive in the face of environmental challenges (Figure 1) (Yamasaki et al., 2007). Figure 1 Effect of artificial selection on the genetic diversity of maize genes (Adopted from Yamasaki et al., 2007). Image caption: Artificial selection in maize can be divided into two stages: domestication and improvement (plant breeding). The coloured circles represent different alleles. The shaded areas indicate bottleneck effects placed on all genes by the processes of domestication and improvement. The model assumes that there will be three types of genes; neutral (unselected) genes that show reduction of diversity by the general bottleneck effects, domestication genes in which diversity is greatly reduced by selection between the teosintes and landraces, and improvement genes in which diversity is greatly reduced by selection between the landraces and inbreds (Adapted from Yamasaki et al., 2007).). 3.2 Genomic studies tracing the migration of maize populations Genomic studies have played a crucial role in tracing the migration and spread of maize from its center of domestication in southern Mexico. These studies leverage advanced genomic technologies to analyze the DNA of ancient and modern maize samples, providing insights into how maize populations have moved and adapted over time. One significant finding from genomic research is the identification of genetic markers that indicate the pathways through which maize spread across the Americas and eventually to other parts of the world. For instance, maize spread northward into the southwestern United States and southward into Central and South America. Genetic evidence suggests that as maize migrated, it hybridized with local teosinte populations, incorporating beneficial traits that enhanced its adaptability to diverse environments (Aguirre-Liguori et al., 2016; Kistler et al., 2020). Additionally, genomic studies have highlighted the role of human selection in shaping the genetic landscape of maize. Artificial selection for desirable traits such as yield, taste, and hardiness has resulted in a variety of landraces adapted to specific regions and uses. This selection pressure has left distinct genetic signatures in the maize genome, which researchers can trace to understand the historical development and spread of different maize varieties (Yamasaki et al., 2007). 3.3 Insights from genetic markers and phylogenetic studies Genetic markers and phylogenetic studies provide critical insights into the evolutionary history and genetic relationships of maize. These tools enable scientists to construct detailed phylogenetic trees that illustrate the genetic connections between different maize varieties and their wild relatives.
RkJQdWJsaXNoZXIy MjQ4ODYzNQ==