Bioscience Evidence 2024, Vol.14, No.3, 122-130 http://bioscipublisher.com/index.php/be 126 Genomic analysis focused on identifying key genes and gene networks involved in maize adaptation to different climatic conditions. For example, Wisser et al. (2019) highlighted several key genes driving the phenotypic response to selection for flowering time in a tropical landrace of maize adapted to a temperate environment. Similarly, Brandenburg et al. (2017) combined differentiation- and diversity-based statistics to identify genes involved in flowering time, drought and cold tolerance, plant defense, and starch properties. 4 Results and Analysis 4.1 Growth performance of corn under different climatic conditions The growth performance of maize under various climatic conditions, including growth rate, yield, and resistance to pests and diseases, has been extensively studied. For instance, maize cultivars in Iran showed a significant reduction in days to anthesis (DTA) and anthesis period (AP) under climate change scenarios, with grain yields decreasing by 6.4% to 42.15% over the next 100 years (Moradi et al., 2014). Similarly, maize production in the North China Plain is projected to decrease by 13.2% to 19.1% without adaptation strategies, although the use of high-temperature tolerant varieties could mitigate these losses (Tao and Zhang, 2010). In tropical environments, maize cultivars exhibited varying responses to temperature fluctuations, with some cultivars showing stable yields across a range of temperatures from 13 ℃ to 28 ℃, while others were more specific in their adaptation (Lafitte et al., 1997). These findings highlight the importance of selecting appropriate maize varieties to optimize growth performance under different climatic conditions. 4.2 Genetic basis of maize adaptation to climate The genetic basis of maize adaptation to different climates involves several key genes. The Dwarf8 (D8idp) gene, for example, has been associated with flowering time variation and is subject to diversifying selection, particularly in temperate climates (Camus-Kulandaivelu et al., 2006). Additionally, genomic studies have identified numerous single nucleotide polymorphisms (SNPs) and gene networks involved in traits such as drought and cold tolerance, plant defense, and starch properties (Brandenburg et al., 2017). Gene expression studies have revealed that maize varieties with enhanced root growth ratios under low temperatures are more tolerant to chilling stress. For instance, the transcriptomic response of maize primary roots to low temperatures identified 64 differentially expressed genes in cold-tolerant varieties, suggesting that these genes play a crucial role in cold adaptation. Moreover, the evolutionary dynamics of polygenic architectures have been shown to condition rapid environmental adaptation, with key genes driving phenotypic responses to selection (Wisser et al., 2019). The interaction between genes and the environment is critical for maize adaptation. For example, the genetic analysis of highland and lowland tropical maize revealed significant line × environment interactions for traits such as biomass, grain yield, and flowering time. These interactions were reflected in systematic changes in trait values and genomic composition across different thermal environments (Jiang et al., 1999). Furthermore, the adaptation of tropical maize germplasm to temperate environments has been achieved through stratified mass selection, indicating that a few major genes are responsible for most of the flowering date expression. 4.3 Comparison between different varieties Genetic diversity among maize varieties is substantial, with studies documenting high levels of variation in climatic adaptation and ecological descriptors among Mexican maize races (Corral et al., 2008). The genetic structuring and historical splits of European and American maize have revealed five genetic groups and two independent European introductions, highlighting the role of admixture in environmental adaptation (Brandenburg et al., 2017). The differences between maize varieties can be attributed to their genetic backgrounds and the specific selection pressures they have undergone. For instance, tropical maize cultivars selected for broad thermal adaptation exhibited unique developmental responses to temperature, resulting in stable grain yields across a wide range of temperatures (Lafitte et al., 1997). In contrast, highland-derived alleles showed little effect at lowland sites, while lowland-derived alleles exhibited broader adaptation (Jiang et al., 1999). These differences underscore the importance of understanding the genetic basis of adaptation to optimize maize breeding programs for diverse
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