Genome-wide Association Analysis And Transcriptomics Study On Resistance Of Rice Brown Planthopper

Brown planthopper（BPH）is one of the most serious pests to rice production.Improving the resistance of rice varieties is considered the safest and the most effective way to control the harm of this pest.Therefore,it is of great significance to further understand the resistance mechanism of rice to brown planthopper by digging out the resistance genes of brown planthopper continuously and carrying out related functional studies.In this study,the progeny materials of rice dominant genic male sterile recurrent population were used to identify the BPH resistance genes,and the near-isogenic line of Bph32 was constructed for transcriptome sequencing analysis.The results of the study explored an efficient way for the excavation of rice dominant genes,provided important genetic resources for improving the BPH resistance of rice,and laid a foundation for further understanding the regulation mechanism of rice resistance to BPH.The results are summarized as follows:1.A field experiment was conducted to test BPH resistance in a F₉ rice population developed by recurrent selection of a variety with dominant genic male sterility.Three high-resistance lines were identified and subjected to a genome-wide association study（GWAS）,which mapped the BPH resistance gene within the region 1.2 Mb-1.67 Mb on the short arm of Chromosome 6.2.One highly resistant line（14CF2426）which identified in the field experiment was further crossed with Taichuang Native 1（TN1）to construct an F₂-segregating population.Identified by artificial insect infestation,three quantitative trait loci（QTL）were mapped to Chromosomes 1,6,and 10.The QTL on Chromosome 6 is located between 0.4 Mb and 1.76 Mb,covering the one calculated by our GWAS analysis and verifying the localization results of the GWAS analysis.The QTLs detected on Chromosome 1 and 10 may be two novel brown planthopper resistance genes.3.Comparative analysis found that the gene located on Chromosome 6 was Bph32.Two pairs of screening markers were developed for Bph32,and the near-isogenic lines NIL-BPH32 and NIL-bph32 of Bph32 were constructed by molecular marker-assisted selection.The results of resistance identification of near-isogenic lines showed that Bph32 significantly increased the resistance of rice to BPH.4.RNA sequencing（RNA-seq）detected 1,268 significant differentially expressed genes（DEGs）with significant differences between the two near-isogenic lines.Compared with NIL-BPH32,1,064 genes were upregulated and 204 were downregulated in NIL-bph32.Gene ontology（GO）enrichment analysis detected 46 significantly enriched terms,and KEGG analysis revealed four significantly enriched metabolic pathways.Multiple DEGs are associated with salicylic acid and jasmonic acid signaling pathways,suggesting that salicylic acid and jasmonic acid signaling pathways may play an important role in the resistance expression of Bph32.