Mapping Of Brown Planthopper Resistance Genes In Rice And Its Application In Variety Improvement

Brown planthopper (Nilaparvata lugens Stal, BPH) is the most destructive pests to rice. Huge economic losses caused by infestation of BPH on rice production per year. So far,27BPH resistance genes have been identified from indica and wild rice, but only Bphl4has been cloned. It is most cost-effecitive and environmentally friendly for utilizing and excavating BPH resistance genes in rice gerplasm to improve rice resistance to BPH. In this study, Using an F2:3population from a cross of Zhenshan97(ZS97) and IR65482-17-511(A BPH resistant introgression line from O. australinensis in IRRI), combined with151SSR markers that covering the whole rice genome to construct genetic linkage map, based on marker geneotypes and pheontypes (seedling resistance and honeydew weight for BPH feeding rate) quantitive trait loci (QTL) associated with BPH resistance were detected and genetic effects were analyzed. The main results are as follows:1. A QTL, associated with both seedling resistance and BPH feeding rate, was detected in the short arm of chromosome4between molecular markers RM261and RM307, with LOD values of28.36and5.82, and explaining the phenotypic variation rate of46.84%and13.36%, respectively. The allele from IR65482-17-511increased resistace and the additive effects were2.09and5.79, respectively. The results showed that this QTL was a major QTL and was named QBph4.2tentatively. In addition, there were another10QTL associated with seedling resistance or BPH feeding rate, which were located on chromosome1,2,3,5,6,7,8,9,11and12, named QBphl, QBph2, QBph3, QBph5QBph6, QBph7, QBph8, QBph9, QBphll, QBph12, respectively. The range of LOD values of these QTL was2.54to4.39, with explaining phenotypic variation range from0.57%to10.15%, indicating that those may be minor QTLs.2. Epistatic QTLs were also detected and analyzed in the F2:3pupulation. There were seven and one pair QTL interaction associated seeding resistance at10and12days after BPH infestation (DAI), respectively, involving a total of six chromosomes, explaining even of more than20%phenotypic variation. 3. For further fine mapping of QBph4.2, another BC1F2population containing2300individuals carrying QBph4.2was developed, and a total of166recombinats were obtained, after screening for recombinant events between marker RM518and HJ28. Another six markers were developed covering the regions of QBph4.2. Based on the marker genotypes of those recombinants,12key recombinants were detected with crossovers between RM261and RM307. Next setp, those12key recombinants would be phenotyped and analyzed, expecting to narrow down the region of QBph4.2. Using marker-assisted selection (MAS) and conventional breeding, six major donminat genes (Bph10, Bphl7, Bph20, Bph21, QBph4.1, QBph3, QBph4.2) were incroporated into93-11, combined with seeding stage test and agronomic traits selection in the greenhouse and field, respectively, improved versions of93-11were obtained.