International Journal of Horticulture, 2024, Vol.14, No.2, 66-77 http://hortherbpublisher.com/index.php/ijh 69 understanding of the complex interactions between genetic and environmental factors to meet the growing global food demand and environmental challenges. To overcome these challenges, researchers can adopt a comprehensive approach, combining traditional breeding techniques with knowledge from molecular genetics, ecology, and environmental science. 2.1 Major improvement goals and research trends Genetic improvement of vegetable crops is primarily focused on improving yield, enhancing nutritional quality, increasing disease resistance, and improving stress tolerance. With the growth of the global population and rising food demand, increasing yield has become one of the core objectives. Researchers are striving to achieve higher crop yields per unit area through genetic improvement while maintaining or improving the nutritional value of vegetables. Sardar (2023) found that the use of gene-editing techniques such as CRISPR/Cas9 can improve the quality, yield, and overall productivity of vegetables and fruits, while improving stress tolerance and meeting biosafety standards. In terms of disease resistance, as diseases can significantly reduce the yield and quality of vegetable crops, researchers seek to identify and introduce disease resistance genes to increase crop resistance to specific pathogens (Samal and Rout, 2018). Furthermore, with the increasingly significant impact of global climate change, the stress tolerance of vegetable crops, such as drought, heat, and salt-alkali tolerance, has also become an important target for genetic improvement. 2.2 Technical and methodological challenges in genetic improvement Despite significant progress in genetic improvement, technical and methodological challenges still exist. One major issue is the limitation of genetic diversity, particularly for economically valuable specialized vegetable varieties, which may lack sufficient genetic diversity, limiting the available genetic resources for improvement (Bate et al., 2021). Additionally, vegetable crop genetic improvement often involves complex traits, which are typically controlled by multiple genes and influenced by environmental factors. This means that identifying and manipulating the multiple genes affecting these complex traits is a technical challenge, especially in the absence of complete genetic maps and functional genomic data. Efficient genotyping and phenotyping methods are crucial in the genetic improvement process, requiring accurate and high-throughput techniques to handle large numbers of samples, rapidly and accurately identifying genetic markers for target traits. There are also challenges in data management and analysis, as large-scale GWAS studies and the integration of genotypic and phenotypic data generate massive amounts of data, requiring efficient data management and analysis tools for processing and interpretation. Furthermore, for some vegetable crops that have not been widely studied, the lack of complete reference genomes, annotated databases, and functional verification tools limits research into the genetic improvement of these crops. Addressing these challenges requires the integrated application of methods and techniques from various disciplines, including genetics, molecular biology, computational biology, and statistics. 2.3 Influence of environmental factors and genetic complexity The phenotypic expression of vegetable crops is influenced by both genetic and environmental factors, increasing the complexity of genetic improvement. On one hand, environmental conditions can significantly affect gene expression and phenotypic variation of traits; on the other hand, the genetic control of traits may exhibit different genetic mechanisms under different environmental conditions. Geshnizjani et al. (2020) found that the quality of tomato seeds and the establishment of seedlings are influenced by genetic background and maternal environment. Through a study of a tomato hybrid population, they revealed how seed quality is controlled by adverse maternal conditions, which may aid in improving the production of high-performance seeds. Research has shown that wheat traits are significantly influenced by genotype, while sowing date has the greatest impact on early developmental stages, indicating that environmental conditions such as sowing time significantly impact plant traits (Kiss et al., 2019).
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