International Journal of Horticulture, 2024, Vol.14, No.2, 66-77 http://hortherbpublisher.com/index.php/ijh 71 GWAS can identify genes affecting plant water use efficiency and transpiration rates. In sesame drought and salt tolerance studies, GWAS revealed significant single nucleotide polymorphisms (SNPs) and potential candidate genes associated with these stress responses (Li et al., 2018). In barley, Tu et al. (2021) used GWAS and transcriptomic analysis to identify salt-responsive genes with altered expression under salt stress, primarily involved in metabolic and transport processes, which could aid in improving crop salt tolerance. In some vegetable crops, GWAS has successfully identified multiple genes associated with drought tolerance, often involving physiological processes such as water regulation, root development, and osmotic adjustment. For example, in maize GWAS research, the natural variation in the ZmVPP1 gene was found to significantly contribute to seedling drought tolerance through enhanced photosynthetic efficiency and root development (Wang et al., 2016). By understanding the mechanisms of these genes, more drought-tolerant vegetable varieties can be cultivated, enhancing the sustainability of agricultural production. GWAS plays a crucial role in the genetic improvement of vegetable crops, from increasing yield to enhancing disease resistance and improving environmental adaptability. This methodological approach continues to drive scientific progress and practical applications in vegetable breeding. By precisely identifying key genetic factors, GWAS accelerates the process of improving vegetable varieties, providing robust scientific support to meet the growing global food demand. 4 The Role of GWAS in Improving Nutritional Value of Vegetable Crops GWAS plays a significant role in improving the nutritional value of vegetable crops. By precisely identifying and functionally validating nutrition-related genes, GWAS provides powerful genetic and molecular biology tools for the nutritional improvement of vegetable crops, thereby promoting the development and adoption of healthier dietary patterns. 4.1 Genetic basis of nutrition-related traits The nutritional value of vegetable crops, including the content of vitamins, minerals, antioxidants, and dietary fiber, is a multi-genic trait controlled by complex genetic networks. The formation and expression of these traits depend on intricate biochemical pathways and metabolic networks within plants, which interact and regulate through various mechanisms during plant growth and development. For example, the synthesis of carotenoids involves multiple biochemical reactions controlled by a series of enzyme-coding genes, whose activities and expression levels are jointly regulated by multiple genes through complex regulatory networks, affecting the final carotenoid content (Saini et al., 2015). The genetic basis of nutrition-related traits is also significantly influenced by environmental factors, such as soil type, water conditions, sunlight exposure, and temperature, which can significantly affect plant metabolic processes and the accumulation of nutrients. Therefore, the interaction between genetics and environment is crucial for understanding and improving the nutritional value of vegetable crops. Understanding the genetic and environmental basis of traits related to nutritional value not only helps scientists and breeders select or design improved vegetable varieties more effectively, but also aids in developing vegetable products that meet the nutritional needs and preferences of consumers. This requires the use of advanced tools in genetics, molecular biology, and bioinformatics to identify and utilize genes and genetic variations that significantly impact nutritional value. 4.2 The role of GWAS in identifying nutrition-related genes Genome-Wide Association Studies (GWAS) play a crucial role in elucidating the connections between vegetable crop nutritional traits and genotypes. Through association analysis, GWAS can identify genetic markers closely associated with variations in nutrient content, providing important clues for in-depth investigation of gene function and regulatory mechanisms. For example, in studies of local and modern tomato varieties, GWAS not only effectively identified genomic regions controlling fruit traits using the SNP diversity from RNA sequencing but also discovered variations associated with climate change adaptability (Rodriguez et al., 2020).
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