| Rice（Oryza sativa L.）is one of the most important food crops in the world.Rice production suffers from all kinds of diseases and insect pests all year round,among which brown planthopper is the most serious pest,which seriously threatens the yield and quality of rice.Breeding and using insect resistant rice varieties is considered to be the most economical and effective measure to control brown planthopper.Therefore,it is of great significance to explore and locate new genes of rice resistance to brown planthopper.Therefore,genetic analysis and QTL mapping of brown planthopper resistance in indica rice variety Youzhan 8 were completed.In addition,on the basis of previous studies,fine mapping of the major QTL Bph35（t）for brown planthopper resistance in indica rice variety Sinna Sivapp was further completed,and the candidate genes in the fine mapping interval were analyzed.The main results are as follows:1.QTL mapping for resistance to BPH in rice variety Youzhan 8The results showed that the resistance level of Youzhan 8 and Cambodian wild rice was 1 and 9 respectively.The results showed that Youzhan 8 was highly resistant to BPH at seedling stage,while wild rice in Cambodia was highly susceptible to BPH at seedling stage.A BC4F8 population with 300 families was constructed by Youzhan 8 and Cambodian wild rice,and 167 families were identified for resistance to BPH.Then,2031 KASP markers distributed on 12 chromosomes of rice were selected to screen the polymorphism of parents Youzhan 8 and Cambodian wild rice.269 markers with good polymorphism between the two parents were selected to construct the molecular linkage map of CSSLs population.Based on the results of phenotypic data,the QTLs for resistance to BPH were detected.Results a QTL with LOD value of 4.74 and contribution rate of 11.02%was detected on chromosome 2,which was named q Bph2.The results showed that q Bph2 was a new BPH resistance locus.2.Fine mapping of major QTL Bph35（t）resistant to Nilaparvata lugensA major QTL Bph35（t）for BPH resistance was detected in the short arm of rice chromosome 6 by constructing F2 population with Sinna Sivapp and susceptible cultivar02428.On the basis of previous work,a total of 61 recombinant individuals were screened from 8214 Sinna Sivapp/02428 F2 individuals,3192 BC1F2 individuals,3033 BC2F2individuals and 3213 BC3F2 individuals using primer S6-27 and primer RM19359.The F2:3and F3:4 families were obtained by selfing.The phenotype of each plant was determined by offspring verification.The gene was located in the 39 kb physical distance interval by continuously encrypting markers.There are four genes with functional annotation in this mapping region,which are LOC＿Os06g04090、LOC＿Os06g04130、LOC＿Os06g04150 and LOC＿Os06g04169.The gene LOC＿Os06g04090 is reported to be a NAC transcription factor involved in secondary wall synthesis,which has been named Os SWN1.Sequence analysis showed that the promoter sequence of Os SWN1 in Sinna Sivapp was different from that in 02428,but there was no difference in the coding region.Through the feeding induction of BPH,it was found that the expression level of Os SWN1 in Sinna Sivapp was significantly higher than that in 02428.Previous studies reported that the expression level of Os SWN1 could affect the accumulation of lignin,and the accumulation of lignin was also reported to improve the resistance of rice to BPH.It is speculated that the resistance of BPH may be affected by the expression of Os SWN1.LOC＿Os06g04130 is a member of seven transmembrane receptor family.The common feature of these receptors is that there are seven transmembraneαhelices in their stereostructure,which have the binding sites of guanylate binding protein.Gene LOC＿Os06g04150 is reported to be a magnesium protoporphyrin IX methyltransferase,a key enzyme in chlorophyll synthesis and chloroplast development.LOC＿Os06g04169 is considered to be a hemolytic phospholipase that can hydrolyze lysophosphatidylcholine.Sequence analysis of the three genes in Sinna Sivapp and 02428 showed that the amino acid sequences were different.Next,the transgenic materials of candidate genes were constructed,which laid a solid foundation for map-based cloning and breeding of BPH resistance genes. |
