Molecular Pathogens, 2025, Vol.16, No.4, 159-170 http://microbescipublisher.com/index.php/mp 166 Secondly, genetically modified technology breaks through species boundaries and can introduce disease-resistant genes from other plants and even microbial sources into wheat. In the field of antifungal diseases, some disease-resistant proteins such as plant antitoxin enzymes, antimicrobial peptides, etc. show enhanced resistance after being introduced into wheat through genetic engineering. Again, the new breeding concept emphasizes reasonable gene layout and resistance gene diversity. Due to the uncertainty of pathogen variation, the rotation or superimposed use of different disease-resistant genes in time and space is regarded as an important strategy to delay resistance loss. For example, my country has implemented a variety layout of "large regions with multiple systems" in stripe rust endemic areas, that is, planting multiple varieties carrying different combinations of disease-resistant genes in the same ecological area, reducing the probability of pathogens overcoming all resistance from the population level. 7 Case Analysis: Molecular Mechanism and Breeding Practice of Wheat’s Resistance to Stripe Rust 7.1 Pathogenic and prevalent characteristics of strip rust Wheat stripe rust is a devastating disease caused by Puccinia striformis f. sp. tritici, referred to as Pst, and is famous for its high frequency of outbreaks and long distances. Striped rust is an obligate parasitic fungus with a complex life history and requires the sexual stage to be completed with the help of winter hosts (such as squid roses), but it mainly uses asexual summer spores to spread circulating in the wheat fields. The bacterial summer spores pile up to form yellow stripe-like rust spots on wheat leaves, and the large number of spores produced can spread thousands of kilometers across regions through airflow (Li et al., 2023). Therefore, strip rust often presents the characteristics of prevalence in large areas. In China, striped rust bacteria will "victory summer" in the southwestern mountainous areas, and in autumn, it will cause epidemics with cold air to migrate northwest and North China wheat areas (Liu et al., 2025). This long-distance migration and transmission gives stripe rust a distinct cross-regional epidemic pattern and the concept of bacterial source base: certain specific areas (such as the southern plateau of China and the western alpine valleys) are the main hosts of bacterial sources over summer or winter, and the occurrence of diseases in these areas often determines the epidemic risk in the main production areas in the spring of the following year. The stripe rust population is highly variable, and its strains (small species) can produce new pathogenic types through sexual reproductive recombination or mutation. Once new virulent species appear, they can often break through the resistance of a wide variety of planted varieties, leading to a pandemic (Figure 2). The mutation rate of stripe rust bacteria is also reflected in the development of drug resistance. The long-term use of single fungicides in some areas has also led to the pathogen's drug-resistant strains (Li et al., 2023). The prevalence of stripe rust is also closely related to climatic conditions. The suitable onset temperature of this bacteria is 10 ℃~15 ℃ and a high humidity environment, so it is prone to occur on a large scale in winter and spring and in high-altitude humid areas. Global warming trends have made high-latitude areas that were previously unsuitable for rust in winter, and now they may become rust-wintering areas, thus expanding the epidemic range. 7.2 Discovery and functional analysis of typical disease-resistant genes (such as Yr series) Since the 20th century, plant protection scholars around the world have identified more than 80 wheat stripe rust-resistant genes, collectively known as the Yr series genes. These genes are widely sourced, including resistance mutations in common wheat itself and multiple relative wild species. For example, Yr15 comes from wild digranular wheat, which gives a high resistance with a wide antibacterial spectrum and is used in breeding in many countries; Yr18 (i.e., Lr34) is a lasting resistance gene. Although the effect alone is moderate, it can significantly delay the onset of the disease and is known as the "slow rust gene". A team from Northwest A&F University of China cloned the high-temperature leaf rust/stripe rust-resistant gene YrZH22 from the wheat variety Zhoumai22 in 2022 and found that it encodes a new NLR protein that can still exert anti-rust effect at higher temperatures (Lai et al., 2024). Some Yr genes have been shown to be essentially allelically or associated with other disease resistance genes. For example, Yr6 and powdery anti-powdery gene Pm5 were found to be different allelic variants of the same gene—the variation of the two loci I366Tand M1011I
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