Triticeae Genomics and Genetics, 2025, Vol.16, No.3, 120-129 http://cropscipublisher.com/index.php/tgg 123 neat and efficient. Even better, it can perform surgery on susceptibility genes (S genes) or simply "create" new resistance alleles, immediately broadening the disease resistance spectrum. Although this method is still being continuously optimized, its efficiency has already been impressive (Huang et al., 2024). It not only saves time but also helps maintain the original agronomic traits without being damaged (Waites et al., 2025). In the future, CRISPR multi-gene integration technology is highly likely to become the new normal in wheat disease-resistant breeding. 4 Key Resistance Genes Used in Transgenic Wheat 4.1 Rust resistance genes (e.g., Lr34, Sr22, Yr36) The "destructive power" of rust disease on wheat is no longer news, so the related resistance genes have become the first choice for transgenic superimposition. Genes like Lr34 are often mentioned, not only because they have a wide range of disease resistance, but also because they "resist for a long time". It encodes an ATP-binding cassette transporter protein, which enables wheat to simultaneously resist leaf rust, stripe rust and even powdery mildew. Although it is not completely immune, the long-term effect is good. This gene can function at both the seedling stage and the mature plant stage, but the effect depends on the coordination of the expression level and the background genome (Risk et al., 2012; Chauhan et al., 2015). Some other anti-rust "experts" like Sr22, Sr21, Sr13, Sr43 and Sr62, mostly from wild wheat relatives, have been successfully cloned and integrated into the five-gene box. For instance, combinations containing Sr22 demonstrated very strong field resistance against a variety of highly toxic stem rust fungi (Chen et al., 2018). As for stripe rust, there have also been new developments recently. For instance, genes like YrNAM and Yr36 have been verified to effectively combat the mainstream stripe rust populations, providing new ideas for subsequent combination strategies (Ni et al., 2023). 4.2 Fungal and viral resistance genes Research on the resistance of wheat does not stop at rust disease. Anti-powdery mildew genes like Pm3, Pm17 and Pm57 have also long been incorporated into the transgenic superposition system. Among them, Pm57 originated fromAegilops searsii and is a typical example of "borrowing genes" from wild species. Multiple Pm3 alleles or combinations like Pm17+Pm3b can bring about a stronger field resistance effect (Zhao et al., 2024b). Furthermore, Fhb7 is a very special gene. It originally originated from fungi and was "mixed" into the plant genome through horizontal gene transfer. This gene can produce a glutathione S-transferase, which is specifically used to detoxify the toxins of Fusarium, and has inhibitory effects on both scab and crown rot. The key point is that it does not affect the yield (Wang et al., 2020). There is another rather interesting case from Damai. After the chi26 (chitinase) gene of barley is transferred into wheat, it enhances the wheat's defense against rust and powdery mildew by breaking down the cell walls of fungi. The effect of this gene has remained relatively stable over multiple generations, indicating that its inheritance is also quite reliable. 4.3 Broad-spectrum defense genes (e.g., PR proteins, antimicrobial peptides) Not all resistance strategies rely on "point-to-point" specific genes; some activate the wheat's own defense system. For instance, PR genes can encode proteins such as chitinase and glucanase, which specifically attack the cell walls of pathogens and are an indispensable part of the acquired resistance (SAR) system in wheat (Eissa et al., 2017). NPR1 is another "dispatch center" type gene. It does not directly resist diseases, but it can regulate the expression of a series of defense-related genes, thereby indirectly enhancing broad-spectrum resistance. Such genes are often a "safety net" strategy under the threat of multiple pathogens. As for antimicrobial peptides, although there are not many application cases in wheat yet, based on the experience of other crops, they have considerable potential. In the future, if multiple antimicrobial peptide genes can be effectively integrated into the wheat genome, it may become an important supplement for building multi-disease resistance. 5 Case Study 5.1 Background: the Ug99 threat and the push for durable resistance Many researchers frown upon hearing the name "East African wheat stalk Rust Pathogen (Pgt) Ug99". This strain of wheat stalk rust disease from East Africa did not suddenly "drop in", but its appearance was like a heavy blow, making people realize that the resistance genes they originally thought were "sufficient" were actually far from
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