Molecular Microbiology Research, 2025, Vol.15, No.2, 82-92 http://microbescipublisher.com/index.php/mmr 85 In addition, some recessive resistance genes in rice also play an important role. For example, Xa5 encodes the translation elongation factor EF-G, and its mutation can weaken the expression regulation effect of pathogen effectors, thereby improving resistance (Chu et al., 2006); and xa13 is a variant of the OsSWEET11 promoter, which blocks the binding ability of pathogen effectors and inhibits nutrient transport (Oliva et al., 2019). Through multi-gene aggregation breeding, combining xa5, xa13 and major effect genes such as Xa21 can effectively improve the breadth and durability of resistance (Kim et al., 2019). 3.2 Sources of resistance and gene positioning of bacterial leaf streak The frequency of bacterial leaf streak (Xanthomonas oryzae pv. oryzicola, Xoc) has increased in South Asia and southern China's rice-growing areas in recent years, becoming a new threat that cannot be ignored among rice bacterial diseases. Similar to bacterial leaf blight, Xoc mainly invades through stomata, causing chlorotic streaks between mesophyll, affecting photosynthetic efficiency and filling quality. Most cultivated rice varieties have a certain resistance to bacterial leaf blight, but are susceptible to bacterial leaf streak, and no major resistance gene has been cloned yet (Jiang et al., 2020). Current research focuses on screening for resistance sources and mining quantitative trait loci (QTL). For example, several materials resistant to Xoc have been identified from African cultivated rice O. glaberrima and common wild rice O. rufipogon. By constructing a recombinant inbred line population and conducting QTL mapping, it has been found that several resistance QTLs are located on chromosomes 1, 5, and 11, such as qBlsr5a and qBls11.1 (Tripop et al., 2021). Studies have shown that the recessive bacterial leaf blight resistance gene xa5 has a certain resistance effect on both bacterial leaf blight and bacterial leaf streak, providing a theoretical basis for multi-disease combined resistance. In addition, with the introduction of genome-wide association analysis (GWAS) technology, multiple loci significantly associated with bacterial leaf streak resistance have been identified. For example, Cai et al. (2025) found 7 significant association loci in the analysis of 247 core germplasms of indica rice, and confirmed their resistance effects through subsequent material screening. These studies have laid the foundation for the subsequent cloning and functional verification of resistance genes. In recent years, CRISPR/Cas9 gene editing technology has also made its debut in BLS resistance research. Yang et al. (2023) simultaneously edited the blast resistance recessive gene Pi21 and the susceptible gene OsSULTR36, and obtained dual-resistant rice materials that are resistant to both rice blast and bacterial leaf streak. This strategy indirectly inhibits the spread of bacteria in leaves by reducing pathogen-induced host transport activity, providing a new path for rice multi-disease resistance breeding. 4 Analysis of Disease Resistance-Related Genes and Regulatory Networks 4.1 Functional characteristics of cloned disease resistance genes With the advancement of genomics and functional genetics technologies, the cloning and functional research of rice disease resistance-related genes has made great progress. The cloned disease resistance genes can be roughly divided into three categories: the first category is typical NLR (nucleotide-binding site-leucine-rich repeat) protein encoding genes, such as Pi9, Pita, Pikm and Xa1, which can recognize pathogen effectors and activate cellular immune responses; the second category is receptor kinase genes, such as Xa21 and Pi-d2, which are involved in pathogen pattern recognition receptor (PRR)-mediated pattern-triggered immunity (PTI); the third category is "executive" resistance genes, such as Xa10 and Xa23, which can be activated by pathogen TAL effectors and induce programmed cell death (Song et al., 1995; Gu et al., 2005; Younas et al., 2024). These genes also have great differences in resistance performance. Broad-spectrum genes such as Pi9, Pigm, and Xa23 can provide stable resistance to multiple strains and are the focus of current disease-resistant breeding (Pedrozo et al., 2025); while specific Rgenes such as Piz and Pita are only effective against some strains and are easily ineffective due to pathogen evolution (Yang et al., 2020). In order to improve the durability of resistance, multi-gene aggregation strategies are usually adopted in breeding practice, combining major R genes with
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