International Journal of Horticulture, 2024, Vol.14, No.2, 66-77 http://hortherbpublisher.com/index.php/ijh 68 In 2005, the first GWAS study on plants was published on the model plant Arabidopsis thaliana, marking the successful initial application of GWAS in plant science (Aranzana et al., 2005). Subsequently, research gradually expanded to major economic crops. For example, in rice, GWAS revealed the genetic basis for controlling mineral and micronutrient composition, providing an important foundation for further research into plant genetics and molecular mechanisms (Yang et al., 2018). Shortly after, important food crops such as maize and wheat also began GWAS research. These early studies primarily focused on elucidating the genetic basis of key agronomic traits affecting crop yield, disease resistance, and stress tolerance. With technological advances, particularly the development and cost reduction of high-throughput sequencing technologies, the application of GWAS has significantly expanded. In the 2010s, more vegetable crops such as tomatoes, carrots, and spinach were included in GWAS studies, which not only focused on yield and disease resistance but also gradually involved complex traits such as nutritional quality (Harish et al., 2023). By the second decade of the 21st century, GWAS had become an indispensable research tool in the field of plant science, capable of utilizing larger sample sizes and more abundant genetic diversity to provide more precise and comprehensive genetic information. Furthermore, the methodologies of GWAS have also been constantly evolving, such as through the integration of phenotypic, genotypic, and environmental data in multi-omics analysis, further improving the accuracy and depth of research (Kao et al., 2017). These advances have not only deepened our understanding of crop genetic mechanisms but have also provided richer and more precise genetic resources for crop genetic improvement. 1.3 Comparison of GWAS with other genetic improvement methods GWAS provides a more comprehensive and in-depth approach to plant genetic improvement, enabling researchers to explore the complex relationships between genetic variations and traits across the entire genome (Tibbs Cortes et al., 2021). Compared to traditional genetic improvement methods such as selective breeding and hybridization, GWAS offers a more precise and efficient approach to identifying genetic variations associated with specific traits. Traditional breeding relies on phenotypic selection and visual assessment of genetic diversity, while GWAS can precisely locate genes or genetic regions associated with traits using genetic markers. Compared to marker-assisted selection (MAS), GWAS covers a broader range of the genome, enabling the exploration of more unknown relationships between genetic variations and traits. MAS typically relies on known associations between genetic markers and traits, while GWAS can identify new associations without bias. The application of GWAS has also led to a series of innovations in the fields of plant genetics and breeding, including the development of multi-omics integrated analysis, precision breeding, and gene-editing technologies. Research has found that combining GWAS with genomic selection (GS) provides new methods for crop improvement, particularly in long-cycle fruit tree breeding, where GWAS can identify genetic markers associated with important agronomic traits (Iwata et al., 2016). These developments further enhance the potential of GWAS in crop improvement, enabling researchers to more rapidly translate genetic discoveries into practical applications. In practice, GWAS results can be directly applied to marker-assisted breeding (MAS), allowing for rapid and accurate selection of plants with desired traits during the breeding process. Additionally, the candidate genes identified through GWAS provide precise targets for gene editing, enabling researchers to directly modify specific genes to improve crop traits. GWAS has played an important role not only in scientific research but also in providing powerful tools for practical crop genetic improvement. Through comparison and integration with other genetic improvement methods, GWAS is expected to play a greater role in global agricultural production, particularly in increasing crop yield, improving nutritional quality, and enhancing environmental adaptability. 2 Current Status and Challenges in Vegetable Crop Genetic Improvement Genetic improvement of vegetable crops not only needs to consider the goals of increasing production and improving quality but also needs to overcome technical and methodological challenges, and gain a deep
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