Rice Genomics and Genetics 2024, Vol.15, No.2, 69-79 http://cropscipublisher.com/index.php/rgg 74 Functional genomics can also verify the function of candidate genes through methods such as gene silencing or overexpression. For example, the rice stress-resistant molecular breeding team used map-based cloning and CRISPR/Cas9 gene editing methods to prove that Pib in the rice variety "Yunyin" (YY) can effectively enhance its disease resistance. Further research found that SH3P2, a protein containing an SH3 domain, has a punctate structure with Pib, which is mainly co-localized at clathrin-coated vesicles in rice cells, and SH3P2 can directly bind to the CC domain of Pib (Xie et al., 2022). To further explore the function of SH3P2 in Pib -mediated rice blast resistance, the researchers studied overexpression and CRISPR/Cas9 knockout transgenic lines and found that SH3P2 itself has no basal resistance, but SH3P2 in YY Overexpression of impairs Pib-mediated resistance to AvrPib-bearing blast strains and cell death induced by Pib-AvrPib specific recognition. Further competition experiments revealed that SH3P2 can inhibit the self-association of the Pib-CC domain. It is shown that SH3P2 is dependent on the Pib -mediated immune pathway and affects the formation of the smallest functional unit of Pib dimer by inhibiting the self-association of the CC domain, thereby negatively regulating Pib-AvrPib recognition-mediated resistance (Xie et al., 2022). 3.3 Mapping of rice blast resistance QTL Rice blast resistance QTL (Quantitative trait loci) is an important research work. Through this work, scientists can discover the genetic factors that control rice blast resistance traits and provide important information for breeding. The steps of quantitative trait locus analysis mainly include multiple stages such as population establishment, phenotypic and genotypic data collection, and QTL analysis. The application of this method provides a powerful tool for rice disease resistance breeding. Combined with the practical significance of molecular marker-assisted breeding, it lays the foundation for the cultivation of highly efficient disease-resistant rice varieties. Mapping rice blast resistance QTL requires establishing a population with rich genetic variation. Typically, scientists choose to cross parents with different disease resistance traits to obtain a series of offspring, forming a genetically diverse population. Taking the cross between a certain resistant rice variety and a susceptible variety as an example, through large-scale phenotypic observation of the hybrid progeny, data on resistance traits are collected and a population suitable for QTL analysis is established (Peng et al., 2021). Scientists need to collect a large amount of molecular marker data, including single nucleotide polymorphism (SNP) markers, parsimonious sequence repeat (SSR) markers, etc. These molecular markers can represent different regions in the rice genome. By analyzing molecular markers for each individual in the population, a high-density genetic map can be constructed. This step helps determine the genotypes of different individuals in the rice population and provides data support for QTL analysis. When conducting QTL analysis, scientists usually use statistical methods, such as association analysis or population genetic analysis, to identify QTL related to rice blast resistance. By comparing individuals in a population showing different disease resistance traits and combining their genotype information, a series of QTL that may be related to resistance can be found. The location information of these QTL helps understand the genetic basis of rice blast resistance traits and provides a strong genetic basis for rice disease resistance breeding (Singh et al., 2021). Molecular marker-assisted breeding has practical significance in disease resistance breeding. Through the use of molecular markers, breeders can screen plants with target disease resistance QTL at an early stage. This helps improve breeding efficiency and reduce waste of resources and time. Taking the previous example as an example, if the disease resistance QTL of a rice variety has been determined through QTL analysis, breeders can use molecular marker technology to directly screen individuals carrying the target QTL in the hybrid progeny to quickly form germplasm resources with resistance genes. Molecular marker-assisted breeding can also help breeders conduct precise genomic selection. Through molecular marker technology, breeders can conduct targeted selection of specific regions in the rice genome, which not only
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