Maize Genomics and Genetics 2024, Vol.15, No.2, 70-79 http://cropscipublisher.com/index.php/mgg 71 This study comprehensively assess the genetic structure and diversity within the genus Zea, with a particular focus on both domesticated maize and its wild relatives. This includes evaluating the levels of genetic variation across different species and subspecies, and understanding the factors that have influenced this diversity. explore the implications of genetic diversity for the conservation and breeding of Zea species. This involves identifying key genetic resources that can be leveraged for crop improvement and developing strategies to mitigate the loss of genetic diversity in wild populations. Synthesize current knowledge on the evolutionary history and gene flow within the genus Zea, thereby providing a framework for future research and conservation efforts. By addressing these objectives, this study aims to contribute to the broader understanding of the genetic landscape of Zea and its significance for both agricultural and ecological contexts. 2 Genetic Structure of Zea genus 2.1 Phylogenetic relationships withinzea The genus Zea, which includes both domesticated maize (Zea mays ssp. mays) and its wild relatives (teosintes), exhibits complex phylogenetic relationships shaped by historical gene flow and divergence events. Studies have shown that the diversification of Zea lineages occurred relatively rapidly within the last 150 000 years, with significant gene flow among taxa, including between domesticated maize and wild teosintes (Ross-Ibarra et al., 2009). This gene flow has played a crucial role in the evolutionary history of Zea, contributing to the genetic diversity observed within the genus. 2.2 Genetic variation and population structure Genetic variation within Zea is substantial, with different studies highlighting the diversity present in various populations and breeding lines. For instance, SSR marker analysis of CIMMYT maize inbred lines revealed an average of 7.4 alleles per marker, indicating high genetic diversity (Xia et al., 2004). Similarly, SNP analysis of maize inbred lines from Sichuan province, China, identified significant genetic variation and population structure, with lines clustering into distinct groups based on their genetic backgrounds (Leng et al., 2019). The genetic diversity within and among CIMMYT maize populations was also confirmed by SSR markers, with most molecular variation found within populations rather than between them (Reif et al., 2004). In addition, the genetic structure of maize germplasm in the China Summer maize ecological region was characterized using over 525 000 SNPs, revealing large genetic diversity and distinct heterotic groups (Shu et al., 2021). This diversity is crucial for breeding programs as it provides a broad genetic base for developing new hybrids with desirable traits. 2.3 Methods for assessing genetic structure Various molecular markers and techniques have been employed to assess the genetic structure of Zea. Simple sequence repeat (SSR) markers have been widely used due to their high polymorphism and ability to reveal genetic relationships among inbred lines (Enoki et al., 2002; Reif et al., 2004; Xia et al., 2004). Genotyping by sequencing (GBS) has also been utilized to generate large numbers of SNPs, providing detailed insights into genetic diversity and population structure (Leng et al., 2019; Shu et al., 2021). Additionally, techniques such as quantitative hybridization and slot blotting have been used to measure the variation in repetitive sequences within the maize genome, further elucidating the genetic structure of different maize strains. These methods have enabled researchers to identify genetic clusters, assess linkage disequilibrium, and understand the genetic basis of important agronomic traits. For example, the MAGIC maize population, a multi-parental population derived from eight diverse founder lines, has been developed to facilitate high-resolution QTL mapping and the identification of candidate genes for complex traits (Figure 1) (Dell’Acqua et al., 2015) . This population provides a valuable resource for studying the genetic architecture of maize and improving breeding strategies.
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