Maize Genomics and Genetics 2024, Vol.15, No.4, 182-190 http://cropscipublisher.com/index.php/mgg 186 Temporal patterns of gene flow are also crucial, as they can indicate historical introgression events and ongoing hybridization processes that shape the genetic structure of maize populations over time. 4.4 Impact of human activities on gene flow Human activities have a profound impact on gene flow in maize. Agricultural practices, such as the cultivation of genetically modified (GM) crops and the movement of seeds across regions, can facilitate or hinder gene flow between wild and cultivated populations. The study on CWRs advocates for the use of evolutionary approaches to capture and conserve genetic variation, highlighting the role of human intervention in managing gene flow (Egan et al., 2018). Additionally, the research on wheat underscores the importance of human-mediated selection in shaping the adaptive landscape of crops through introgression (He et al., 2022). These insights underscore the need for careful management of gene flow to balance crop improvement with the conservation of genetic diversity. 5 Implications of Gene Flow 5.1 Genetic diversity and adaptation Gene flow plays a crucial role in maintaining and enhancing genetic diversity within maize populations. The introduction of alleles from modern varieties (MVs) into traditional landraces (LRs) and wild relatives (WRs) has been shown to increase genetic diversity, which is essential for adaptation to changing environmental conditions. For instance, a study demonstrated that gene flow from MVs into LRs and WRs in Mexico led to an increase in genetic diversity post-2000, likely due to the introgression of beneficial alleles from MVs (Rojas-Barrera et al., 2019). This enhanced genetic diversity is vital for the evolutionary capacity of maize populations to adapt to novel environments, as evidenced by the retention of 99% of the standing molecular marker variation in a population subjected to directional selection for flowering time adaptation (Wisser et al., 2019). 5.2 Evolution of agronomic traits Gene flow significantly influences the evolution of agronomic traits in maize. The introgression of alleles from MVs into LRs and WRs can lead to rapid changes in traits such as flowering time, yield, and drought resistance. For example, a high-resolution genome-wide association study identified hundreds of candidate genes associated with genotype by environment interactions, which are crucial for agronomic performance across diverse environments (Gates et al., 2019). Additionally, the domestication process of maize, which involved the transformation of teosinte into modern maize, was driven by genetic interactions and selection pressures that shaped key agronomic traits (Stitzer et al., 2018). These findings underscore the importance of gene flow in the ongoing evolution and improvement of agronomic traits in maize. 5.3 Pest and disease resistance Gene flow also has implications for pest and disease resistance in maize. The introduction of alleles from MVs into LRs and WRs can enhance resistance to pests and diseases, which is critical for crop sustainability. The genomic evidence of ongoing evolution in maize due to introgression from MVs suggests that beneficial alleles conferring resistance to biotic stresses may be incorporated into the genetic pool of LRs and WRs (Rojas-Barrera et al., 2019). This process can lead to the development of maize varieties with improved resistance to pests and diseases, thereby reducing the reliance on chemical control methods and promoting sustainable agricultural practices. 5.4 Conservation and biodiversity The conservation of genetic diversity and biodiversity in maize is closely linked to gene flow. The introgression of alleles from MVs into LRs and WRs not only enhances genetic diversity but also contributes to the conservation of these genetic resources. Monitoring strategies and policies that promote the use and safeguarding of genetic diversity are essential for the conservation of maize at its center of origin (Rojas-Barrera et al., 2019). Furthermore, understanding the evolutionary dynamics of maize populations, including the role of gene flow, is crucial for developing effective conservation strategies that ensure the long-term sustainability of maize biodiversity (Stitzer et al., 2018; Rojas-Barrera et al., 2019; Gates et al., 2019).
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