Genetic Analysis Of Small Brown Planthopper Resistance In Rice Variety MR1523 And Fine Mapping Of QSBPH5

Rice(Oryza sativa L.)is one of the most important food crops in the world and is attacked by a large number of insects.Among these insect pests,small brown planthopper is one of the most serious pests of rice.SBPH is one of the rice planthoppers which widely distributed in Asia.These insects feed on rice phloem sap,affecting the growth of rice plants and resulting in "hopperburn" in the case of SBPH,resulting in yield losses and reduced grain quality.More seriously,these rice planthoppers also act as vectors of major viral diseases such as RSVD and RBSDVD.In recent years,the increasing damage caused by rice planthopper resulted in severe yield losses in rice.This is a serious threat to rice production in China and other rice grown countries and the global food security.Nowadays,the control for rice planthopper and viral diseases transmitted by rice planthopper mainly depends on chemical pesticides.While repeated over-application of pesticides increases the cost of agricultural production,causes environmental pollution,kills predators,and destroys the ecological balance and so on.At the same time,SBPH has strong mobility and can transmit virus instantly,which greatly limits the control of SBPH.The most economical and effective way to control insects and disease is developing new resistant cultivars.This lays the foundation for pyramiding multiple resistance genes and developing durable resistance cultivars.It is of great significance both in theory and practice to accelerate the development of resistance to rice planthopper and rice black streaked dwarf virus.In this study,we studied the genetic basis of resistance of two rice varieties(MR1523 and NU3),and on this basis,we made a fine mapping of one of the QTLs.The major results are as follows:1.The resistant variety MR1523 displays high resistance aganist SBPH,we constructed a F2 populatin derived from the cross between MR1523 and susceptible japonica Suyunuo in this study,each F2 plant was obtained by the corresponding inbred family F2:3 and used 120 SSR and InDel markers uniformly distributed on 12 rice chromosomes to construct the genetic linkage map.Furtherly,we evaluated the resistance of F2:3 families against SBPH by SSST and conducted the rice planthopper resistance quantitative trait loci(QTL)analysis.Four QTLs are detected,located on chromosome 2,5 and 6,named qSBPH2,qSBPH5a,qSBPH5b and qSBPH6,respectively,located between the RM526-RM3763,RM17804-RM13,RM574-RM169 and RM190-RM510,LOD values were 2.14,3.13,3.23 and 2.35,the contribution rate were 12%,14.7%,17.4%and 14.1%,the QTL resistance allele effect from insect resistant parent MR1523.The discovery and location of the above genes can lay a foundation for the subsequent fine mapping of resistance genes and breeding new rice varieties with resistance to small brown planthopper by molecular marker assisted selection.2.The resistant variety NU3 displays high resistance aganist SBPH.In order to investigate the genetic basis of this variety resistance to rice planthopper,we constructed a F2 Populatin derived from the cross between NU3 and susceptible japonica USSR5 in this study,each F2 plant was obtained by the corresponding inbred family F2:3 and used SSR and Indel markers uniformly distributed on 12 rice chromosomes to construct the genetic linkage map.Furtherly,we evaluated the resistance of F2:3 families against SBPH by SSST and conducted the rice planthopper resistance quantitative trait loci(QTL)analysis.3 QTLs are detected in this population on chromosome 4,5 and 7,between markers RM16335-RM6659,RM405-RM169 and RM21976-InDel7-11,with a LOD score of 2.5,3.5 and 2.1,explaining 14.2%,14.3%and 15.3%of the phenotypic variance.We furtherly select heterozygous genotype of qSBPH5,while another two QTLs are USSR5 genotypes,and conduct a secondary separation groups.Then we evaluated the resistance of the families by SSST and map the loci with more markers.Finally we locate the gene in the 200 Kb region of markers RM3328-SG504.The new resistant genes identified in this study provides the foundation for cloning of rice plant hopper resistance gene and developing resistant cultivars to eontrol rice planthoppers and viral diseases transmitted by SBPH.