Genomics and Applied Biology 2024, Vol.15, No.1, 12-21 http://bioscipublisher.com/index.php/gab 17 experiments. Through these experimental verifications, it is possible to determine which candidate genes are actually involved in the disease resistance response of maize. 3 Practical AWAS in Corn Disease Resistance Breeding 3.1 Functional verification of candidate genes Genome-wide association studies (GWAS) in corn disease resistance breeding is not only limited to the identification of candidate genes, but also involves the verification of the functions of these genes. Functional verification of candidate genes is a key step in converting GWAS research results into practical breeding applications. To ensure that the identified genes are directly related to specific disease resistance traits, scientists used a variety of molecular biology techniques to verify the functions of these genes, including gene knockout, gene overexpression, and, more recently, gene editing, which has been widely used technology. Professor Xu Mingliang's research group used integrated genome-wide association (GWAS) and transcriptome analysis methods to obtain a series of candidate genes for corn ear rot resistance, and initially revealed the molecular mechanism of early disease resistance. Corn ear rot is one of the most serious diseases in China's corn production. It not only affects the yield and quality of corn, but also seriously threatens the health of people and livestock due to corn kernels contaminated by toxins secreted by pathogenic bacteria. In their experiments, they found SNP sites significantly associated with resistance through genome-wide association studies, and found genes around these sites that may be related to ear rot resistance. Then, phenotypically stable resistant and susceptible materials were selected for transcriptome analysis, and it was found that differentially expressed genes were mainly enriched in pathways such as plant hormone signal transduction, phenylalanine metabolism, and cytochrome P450 metabolism. The results showed that there were differences in gene expression between resistant and susceptible materials, especially in the plant hormone signal transduction pathway. Finally, it is speculated that when pathogenic bacteria infect corn kernels, disease-resistant materials will adjust the balance of growth and resistance, synthesize more secondary defense metabolites, and form an early defense response to ear rot (Figure 1) (Yao et al., 2020). Figure 1 Analysis of corn ear rot (Yao et al., 2020) Note: A, C, E, G: Quantile-Quantile plot and (B, D, F, H) Manhattan plot of each position are shown; A, B: Corn grown in Beijing in the summer of 2017; C, D: Corn planted in Hainan in the winter of 2017; E, F: Corn planted in Beijing in the summer of 2018; (G, H: BLUP data; BLUP data calculated from data of 309 lines from 3 environmental replicates
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