Maize Genomics and Genetics 2024, Vol.15, No.4, 182-190 http://cropscipublisher.com/index.php/mgg 185 3.4 Experimental and observational studies Experimental and observational studies are crucial for validating hypotheses about gene flow in maize. For example, the development and validation of the 5.5 K SNP markers panel using GBTS technology involved extensive genetic analyses of two maize populations, revealing genetic divergences and prediction accuracies for various traits (Ma et al., 2022). These studies provide empirical data on the genetic structure and diversity of maize populations, which are essential for understanding gene flow. Observational studies, such as the analysis of DNA methylation patterns in modern maize, landrace, and teosinte populations, have also shed light on the role of epigenetic variations in adaptive evolution (Xu et al., 2020). Together, these experimental and observational approaches contribute to a comprehensive understanding of gene flow dynamics in maize. 4 Patterns of Gene Flow in Maize 4.1 Gene flow between wild relatives and cultivated maize Gene flow between wild relatives and cultivated maize is a critical factor in the evolutionary dynamics of maize. Wild relatives of crops, such as teosinte, serve as reservoirs of genetic diversity that can be introgressed into cultivated maize. This gene flow can introduce beneficial traits, such as disease resistance and environmental adaptability, into the cultivated gene pool. For instance, the study on crop wild relatives (CWRs) emphasizes the importance of capturing genetic variation from wild relatives to enhance crop improvement efforts (Egan et al., 2018). Similarly, research on wheat has shown that introgression from wild relatives significantly contributes to the adaptive diversity of modern crops, suggesting a parallel importance in maize. 4.2 Introgression and hybridization events Introgression and hybridization events play a pivotal role in shaping the genetic landscape of maize. These processes involve the incorporation of genetic material from one species into the gene pool of another through repeated backcrossing. The study on wheat highlights how introgression from wild relatives has historically contributed to the adaptive evolution of crops by increasing genetic diversity and reducing deleterious alleles (He et al., 2019). This phenomenon is likely mirrored in maize, where hybridization with wild relatives can introduce new alleles that enhance agronomic traits and environmental adaptability. 4.3 Spatial and temporal patterns The spatial and temporal patterns of gene flow in maize are influenced by various factors, including geographic isolation and environmental conditions. The research on woodland strawberry demonstrates that landscape isolation and mesoclimatic variation are significant determinants of genetic variation in wild populations (Egan et al., 2018). These findings suggest that similar spatial proxies could be used to predict gene flow patterns in maize. 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
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