Molecular Pathogens, 2025, Vol.16, No.4, 171-181 http://microbescipublisher.com/index.php/mp 175 4.2 Molecular labeling assisted selection Molecular marker-assisted selection (MAS) is a key technology widely used in crop disease-resistant breeding in recent years. It greatly improves the accuracy and efficiency of breeding selection by using DNA markers to track disease-resistant genes. MAS has achieved many successful cases in rice resistant bacterial disease breeding. On the one hand, for cloned main-acting disease-resistant genes, researchers have developed tightly linked or functional molecular markers to rapidly detect whether the material carries the target resistance allele (Sun et al., 2025). For example, for the broad-spectrum anti-white leaf blight gene Xa7, some scholars have designed specific molecular markers that can accurately distinguish the genotype of rice materials and achieve efficient detection of homozygous or heterozygous Xa7 (Liu et al., 2021). This marker is used in breeding to select offspring carrying Xa7, which is more reliable than simply relying on intra-field inoculation identification. On the other hand, MAS is often used in gene pyramiding breeding, that is, to gradually accumulate multiple disease-resistant genes into the same variety (Figure 2). By establishing marker tests for each disease-resistant gene, individuals carrying all target genes were simultaneously screened in each generation of offspring, thereby cultivating new varieties with multigene resistance (Bharani et al., 2010; Ullah et al., 2022). Figure 2 Lesion developed by Xoo isolates on advanced RILs of rice (Adopted from Ullah et al., 2022) 4.3 Gene editing and precision breeding The rise of gene editing technology provides new ideas and means for rice disease-resistant breeding. In particular, the third-generation gene editing tool represented by CRISPR/Cas9 can accurately transform specific sites in the rice genome and obtain improvements in disease-resistant traits without introducing exogenous genes (Xu et al., 2019; Zafar et al., 2020). At present, there are two main application strategies for gene editing in rice antibacterial disease breeding: one is to edit susceptible genes to reduce their function and enhance their resistance, and the other is to modify resistance genes at a targeted location to expand or enhance their resistance function. Another strategy is to directively modify the resistance gene itself to create new functions or expand the resistance spectrum. Traditional disease-resistant genes mostly come from natural mutations, and there may be problems with narrow resistance spectrum or unstable resistance. Gene editing can introduce specific amino acid variants on known resistance gene sequences to create new alleles (Zhou et al., 2021). In addition, genome-directed insertion is also a promising technology, such as using gene editing to accurately insert expression cassettes of multiple disease-resistant genes into safe sites in rice genomes, achieving one-time transformation to obtain multi-gene polymerized disease-resistant strains. Although this involves transgenic manipulation, with the development of biotechnology, it is expected to reduce transgenic blots through precise insertion without exogenous selection markers.
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