Triticeae Genomics and Genetics, 2025, Vol.16, No.6, 245-253 http://cropscipublisher.com/index.php/tgg 249 6 Case Studies 6.1 GWAS of fusarium head blight resistance in U.S. winter wheat core germplasm In the United States, researchers did not start from scratch to search for the fusarium head blight resistance gene. Over the past few years, they have conducted high-density SNP genotyping on breeding populations of hard and soft winter wheat, combined with multi-locus GWAS methods. Many loci related to FHB resistance have been identified on multiple chromosomes - such as 2A, 3B, 4A, 4B, 5A, 6A, 7A and 7D - (Arruda et al., 2016; Larkin et al., 2020). Some resistance sites are familiar faces, while others are newly discovered. Research has found that as long as certain alleles are present in varieties, the incidence of FHB and the level of mycotoxins (DON) can be significantly reduced (Figure 2). However, it is not the case that multiple beneficial alleles combined together are very common. In reality, strains with such an "ideal combination" are quite rare, which also indicates that the path of disease-resistant breeding is not simple (Ghimire et al., 2022; Zhang et al., 2022). Figure 2 Pearson's correlation matrix among three Fusarium head blight (FHB) and two morphological traits of 278 soft red winter wheat lines on combined data in the greenhouse across 2 yr (Adoted from Ghimire et al., 2022) 6.2 Multi-platform phenotyping and QTL mapping in wheat varieties from the Huang-Huai region of China In the Huanghuai wheel-growing region, GWAS is also a major tool, but in terms of approach, it focuses more on integrating multiple phenotypic platforms and environmental data. For example, by using 90K SNP chips and in combination with multi-year and multi-site field trials, researchers discovered QTL loci related to FHB resistance stability on multiple chromosomes (Wang et al., 2023). Some sites have been able to stably appear in different environments for several consecutive years, which gives people more confidence in their reliability. More importantly, such results can directly support molecular marker-assisted selection and provide a breeding direction for regionally adapted disease-resistant wheat varieties.
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