Molecular Pathogens, 2025, Vol.16, No.5, 236-245 http://microbescipublisher.com/index.php/mp 239 resistance screening of thousands of local varieties in Southeast Asia, a number of broad-spectrum blast-resistant rice varieties were discovered, such as the Indian variety Tadukan, the Philippine variety IR36, etc., from which important broad-spectrum blast-resistant genes such as Pi9 and Pi2 were cloned in subsequent studies (Ashkani et al., 2015). Multiple new disease resistance gene loci have also been identified in China's abundant rice local varieties and wild rice resources. Regarding wild relatives, common wild rice (Oryza rufipogon), long-male wild rice (O. longistaminata), etc. have been proven to contain many disease-resistant genetic variations that cultivated rice lacks. Some resistance can be introduced into cultivated rice through distant hybridization. For example, the bacterial blight resistance gene Xa21 was successfully discovered from the wild rice O. longistaminata and transferred into cultivated rice (Vasudevan et al., 2014). Therefore, in the identification and utilization of disease-resistant germplasm, the method of combining field multi-point resistance identification with laboratory molecular markers should be strengthened. Figure 1 Schematic illustration of DNA methylation mechanism (Adopted from Wu and Fan, 2025) 4.2 Cross breeding and group selection strategies Traditional cross-breeding combined with population selection is a classic way to breed disease-resistant rice. Usually, a “resistant source For example, Indian rice Tadukan (Pi-ta), IR64 (Pi-b) and China's "rice blast resistance source 74-1-1" have successfully bred new blast-resistant varieties. Group selection is crucial in breeding. In the early stage, disease-resistant individual plants are strictly selected in the disease nursery. In the later stage, the yield and quality are comprehensively inspected in the normal field, and excellent pedigrees are fixed from generation to generation. Group improvement (recurrent selection) gradually improves group resistance through the cycle of "mating-selection-remating". Especially for horizontal resistance controlled by multiple genes, through multiple rounds of reciprocal crosses and phenotypic screening, favorable allele frequencies can be accumulated, ultimately significantly enhancing the overall disease resistance level (Song et al., 2016). 4.3 Application of marker-assisted selection (MAS) in disease resistance breeding Molecular marker-assisted selection is a technical means that has achieved remarkable results in disease resistance breeding in the past 20 years. MAS uses DNA markers that are closely linked to the target disease resistance gene or produced by its direct mutation to screen the offspring for genotypes, thereby efficiently identifying individuals carrying the target gene in the early generations. Compared with relying solely on phenotypic screening, MAS can accurately determine individual genotypes when the disease has not occurred or is hidden, significantly improving selection accuracy and shortening the breeding cycle. In rice blast resistance breeding, MAS has been successfully used to aggregate multiple broad-spectrum blast resistance genes (Sattari et al., 2014). In the bacterial blight-resistant sterile lines bred in China, functional markers of the Xa23 gene are widely used, and individual plants of each generation are tested to ensure that all selected plants carry Xa23. Another advantage of MAS is
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