Maize Genomics and Genetics 2024, Vol.15, No.2, 93-101 http://cropscipublisher.com/index.php/mgg 94 2 Genetic Factors Influencing Grain Quality 2.1 Key genetic traits Grain quality in maize is significantly influenced by various genetic traits. Key traits include kernel composition, such as protein, starch, and oil content, which are critical for both nutritional value and industrial applications. Studies have shown that genetic variation plays a substantial role in determining these traits. For instance, a study evaluating 501 diverse temperate maize inbred lines found significant genetic control over 16 compositional traits, with 22.9-71.0% of phenotypic variation explained by genetic factors (Renk et al., 2021). Additionally, kernel depth and ear length have been identified as important genotypic covariates influencing yield and stability under stress conditions (Romay et al., 2010). 2.2 Molecular markers and QTL mapping Molecular markers and quantitative trait loci (QTL) mapping are essential tools for understanding the genetic basis of grain quality traits. Genome-wide association studies (GWAS) have identified numerous single nucleotide polymorphisms (SNPs) associated with key compositional traits. For example, a GWAS conducted on a maize diversity panel identified 72 significant SNPs for 11 compositional traits, providing valuable insights for breeding programs aimed at improving grain quality (Renk et al., 2021). These molecular markers facilitate the selection of desirable traits, thereby enhancing the efficiency of breeding programs. 2.3 Genetic engineering and CRISPR/Cas9 Genetic engineering, including the use of CRISPR/Cas9 technology, offers promising avenues for improving maize grain quality. CRISPR/Cas9 allows for precise genome editing, enabling the modification of specific genes associated with desirable traits. This technology has the potential to enhance traits such as kernel composition, disease resistance, and stress tolerance. Although specific studies on CRISPR/Cas9 applications in maize grain quality are limited, the technology's success in other crops suggests significant potential for maize improvement. 2.4 Role of teosinte in genetic improvement Teosinte, the wild ancestor of maize, plays a crucial role in the genetic improvement of modern maize varieties. The genetic diversity present in teosinte offers a valuable reservoir of traits that can be introgressed into maize to enhance grain quality. For instance, teosinte has been used to introduce traits such as drought tolerance and disease resistance into maize, thereby improving its adaptability and productivity under various environmental conditions. The integration of teosinte genes into maize breeding programs has the potential to enhance grain quality by introducing novel genetic variations (Russell, 1991). 3 Environmental Factors Influencing Grain Quality 3.1 Climate and weather conditions Climate and weather conditions play a pivotal role in determining the grain quality of maize. Variations in temperature, precipitation, and other climatic factors can significantly impact the yield and quality of maize grains. For instance, high temperatures during critical growth stages can lead to reduced grain filling and lower quality grains. A study conducted in Spain highlighted that climatic variables such as days with mean temperatures over 15 ℃ and maximum temperatures in September were crucial for maize yield under stress conditions like drought and cold (Romay et al., 2010). Similarly, another study in Brazil found that differences in light, accumulated temperature, and precipitation were key factors affecting maize grain quality, with variations in these factors leading to differences in protein, starch, and fat content in the grains (Tian et al., 2021). Drought conditions, in particular, have been shown to severely limit maize yield and quality. Research in Eastern and Southern Africa demonstrated that drought stress significantly affected the grain yield stability of quality protein maize hybrids, with certain hybrids performing better under drought conditions than others (Mebratu et al., 2019). This indicates that both the timing and intensity of drought can influence the final grain quality. 3.2 Soil characteristics Soil characteristics, including soil type, nutrient availability, and soil texture, are critical determinants of maize grain quality. The presence of essential nutrients like nitrogen (N), phosphorus (P), and magnesium (Mg) in the
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