Molecular Microbiology Research, 2025, Vol.15, No.2, 82-92 http://microbescipublisher.com/index.php/mmr 84 research team aggregated the three genes Pi1, Pi2, and Pita through molecular marker-assisted selection technology, and the new materials cultivated showed high resistance when artificially inoculated with 32 rice blast fungus subspecies (Xiao et al., 2019). It is worth noting that there is functional overlap or interaction between different disease-resistant genes, and sometimes the more genes, the better, so the rational selection and configuration of disease-resistant gene combinations is particularly critical. 2.2 Exploration of resistance to secondary fungal diseases such as bacterial leaf blight Although bacterial leaf blight is a bacterial disease, it is often discussed together with rice blast because it is highly related to rice blast in breeding strategies and mechanism research. To date, more than 40 bacterial leaf blight resistance genes (Xa series) have been identified, of which 15 have been cloned and functionally verified. A typical example is Xa21, which comes from wild rice Oryza longistaminata and encodes a receptor kinase protein that can provide broad-spectrum resistance under multiple environmental conditions. It is one of the most practical Xa genes at present (Song et al., 1995). In addition, Xa23 is also a broad-spectrum and highly efficient resistance gene that has been successfully used in the improvement of multiple hybrid rice varieties (Li et al., 2025). In addition to major effect genes, some recessive genes such as xa5 (encoding translation elongation factors) and xa13 (related to the sugar transporter SWEET family) also play a key role in bacterial leaf blight resistance. In particular, mutations in the promoter of xa13 can prevent pathogen effectors from binding, thereby inhibiting the transport of nutrients required by pathogens, and are widely used in the construction of resistant materials (Chu et al., 2006; Oliva et al., 2019). Compared with rice blast, research on resistance to fungal diseases such as sheath blight and false smut is still in its infancy. These diseases often lack clear major resistance genes, and resistance improvement is currently mainly carried out through QTL positioning and large-scale resistance source screening. Studies have found QTLs with stable resistance to sheath blight in multiple japonica and indica rice varieties, such as qSB-11LE (Jia et al., 2025). In recent years, the use of gene editing technology to knock out certain genes related to disease susceptibility has also become a new strategy. For example, Shi et al. (2023) obtained rice materials with broad-spectrum resistance to sheath blight, white leaf blight and bacterial streak by knocking out the OsCDS5 gene. 3 Research on Resistance Mechanisms to Bacterial Diseases of Rice 3.1 Identification of major resistance genes to bacterial leaf blight Bacterial leaf blight is one of the major bacterial diseases of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo). The disease usually infects through wounds or water holes, spreads rapidly under high temperature and high humidity conditions, and can cause a 20%~50% reduction in yield. Since the 20th century, researchers have identified more than 40 gene loci in rice that are resistant to bacterial leaf blight, of which at least 15 have been cloned and functionally verified (Luet al., 2022). The major genes Xa1, Xa3/Xa26, and Xa21 play a significant role in resistance to bacterial leaf blight. Xa21 originated from African wild rice O. longistaminata and is the first cloned broad-spectrum resistance gene for bacterial blight. It encodes a transmembrane receptor kinase containing an LRR domain that can recognize signal molecules secreted by pathogens and trigger downstream immune responses (Song et al., 1995). Xa23 is considered to be a highly practical broad-spectrum resistance gene and has been successfully introduced into multiple hybrid rice restorer lines (Li et al., 2025). In addition, there is a class of "executive" resistance genes, such as Xa10 and Xa27, whose expression is activated by the TAL effectors of the pathogen and induces hypersensitive cell death to prevent the spread of the pathogen (Gu et al., 2005). Some resistance genes are temperature-dependent. For example, Xa7 has enhanced resistance under high temperature and has strong potential to adapt to climate change (Webb et al., 2010). Therefore, the screening of disease resistance genes should not only consider the resistance spectrum, but also pay attention to its performance stability under different environmental conditions.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==