Plant Gene and Traits 2024, Vol.15, No.4, 174-183 http://genbreedpublisher.com/index.php/pgt 178 quality. For instance, the wheat breeding line 10V-2, which carries the Pm10V-2 resistance gene, has demonstrated superior agronomic performance alongside its resistance to powdery mildew (Ma et al., 2017). This suggests that resistance genes can be integrated into breeding programs without detrimental effects on other important traits. Further analysis has revealed that the presence of resistance genes can sometimes be associated with improved agronomic performance. For example, the Pm5e gene, identified in a Chinese wheat landrace, not only provides resistance to powdery mildew but also contributes to the overall robustness of the plant (Figure 1) (Xie et al., 2020). This indicates that the MlWE74 gene, similar to other resistance genes, may have a positive correlation with certain agronomic traits, making it a valuable addition to wheat breeding programs (Xie et al., 2020; Zhu et al., 2021). Figure 1 Validation of the candidate NLR gene for the powdery mildew resistance gene Pm5e and phenotypes of EMS mutants (Adapted from Xie et al., 2020) Image caption: (a): Structure of the NLRgene and its mutants, showing the gene structure from the start to stop codon. Blue, green, and red represent the coiled-coil (CC-like) domain, nucleotide-binding site (NBS), and leucine-rich repeat (LRR) domain, respectively. Vertical short lines indicate the mutation sites, with the changes in the coding sequence (c.) and the predicted effects on the translated protein (p.) annotated below; (b): Infection phenotypes of resistant variety FZ30, susceptible control Xuezao, and five susceptible mutants 14 days after inoculation with powdery mildew fungus (Blumeria graminis f. sp. tritici) (Adapted from Xie et al., 2020) Xie et al. (2020) validated the powdery mildew resistance gene Pm5e in wheat through EMS mutants, and their study revealed that multiple mutation sites in NLRgenes were associated with the loss of disease resistance. In the research, the resistant variety FZ30 showed strong disease resistance, while different mutants, due to mutations at specific gene sites, exhibited increased susceptibility to powdery mildew, indicating that these mutations affected the function of the Pm5e gene. This study provides an important molecular foundation for wheat disease resistance breeding. From this, it can be concluded that wheat powdery mildew resistance genes such as MlWE74 and Pm5e can help in breeding varieties with stable resistance to powdery mildew, reducing the use of pesticides and improving wheat yield and quality. 5.3 Successful cases in breeding programs Several successful cases in breeding programs highlight the effectiveness of incorporating the MlWE74 gene into wheat varieties. One notable example is the development of the wheat line WE74, which has been extensively tested and shown to possess strong resistance to powdery mildew due to the MlWE74 gene (Zhu et al., 2021). The use of molecular markers has been instrumental in tracking the gene during the breeding process, ensuring its successful integration into new cultivars. Another successful case involves the wheat breeding line Yannong 99102-06188, which carries a different resistance gene, pmYN99102. This line has shown high resistance to powdery mildew across various growth stages and has been effectively used in breeding programs to develop new resistant varieties (Mu et al., 2022). The success of these programs underscores the potential of resistance genes like MlWE74 in enhancing the disease resistance of wheat cultivars while maintaining or even improving their agronomic performance (Zhu et al., 2021; Mu et al., 2022).
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