QTLs Analysis Of Small Brown Planthopper Resistance And Proteomics In A New Rice Germplasm

Small brown planthopper(SBPH),Laodelphax striatellus Fallen(Homoptera:Delphacide)is one of the most destructive insect pests in main rice-growing.SBPH not only causes direct damage,but also transmits several viral diseases.In recent years,application of chemical peticides is the main measure for control SBPH.However,chemical control can lead to pesticide resistance in the insect,environmental pollution and control effect is not satisfactory.Therefore,host resistance has been recognized as one of the most economic and practical measures in controlling SBPH.Oryza officinalis Wall.ex Wstt,a wild rice species,contained abundant genetic diversity and accumulated a large number of important beneficial genes.O.offcinalis and O.sativa(cv.02428)were used for asymmetric somatic hybridization.Pf9279-4 is an introgression line derived from the asymmetric somatic hybridization and exhibits resistance to SBPH.By using Standard Seedbox Screening Technique Test,evaluation of resistance to SBPH was performed in the tested rice materials.The results were that O.officinalis is immune to SBPH.Mudgo and Pf9279-4 were highly resistant and resistant to SBPH.02428,9311,TN1 and Wuyujing 3 were all highly susceptible to SBPH,respectively.There was an adverse effect in the life span,nymph duration,fecundity and antixenosis in Pf9279-4 plants to SBPH.The resistance of Pf9279-4 to SBPH was tolerance and antixenosis.The mapping population composing of 101 F2 lines derived from a cross between 9311 and Pf9279-4 were used to detect QTLs for resistance to SBPH.The QTLs for SBPH resistance,three QTLs for SBPH resistance,designated as Qsbph3d,Qsbph 7a and Qsbph12b,were mapped on chromosomes 3,7 and 12,respectively.They were mapped at location between RM1324-RM6881,RM3225-RM3755 and RM3225-RM3755,respectively.According to the result of the detection of QTLs for SBPH resistance,the identification of the introgressed segments using SSR markers was employed to determine whether the Pf9279-4 carries the wide rice(O.officinalis)segments in the regions of the QTLs for SBPH resistance that assigned in the present study or not.The result showed that the Pf9279-4 carried only one single homozygous segment of O.officinalis on chromosome 3 between RM218 and RM7425.The Pf9279-4 carried only a single homozygous segment of O.officinalis on chromosome 7 between RM218 and RM7425.The infiltration fragment on chromosome 12 is between RM463 and RM6265.The position of these chromosomal segments detected existed within the regions of the QTLs for SBPH resistance,so this result confirmed the accuracy of the detected QTLs.Qsbph3d was reduced between RM218 and RM7425,the physical distance was 3.2 Mb,Qsbph7b was reduced between RM7012 and RM6338,the physical distance was 3.1 Mb,Qsbphl2a was reduced RM463-RM6265,the physical distance is 2.9 Mb.The single chromosome replacement lines C2-1-12 and C2-1-6 contain the resistant QTLs of chromosome 3 and 7.The results of the proteomics study of Pf9279-4 are as follows:29 differentially expressed protein spots(DEPs)changed their intensities in Pf9279-4 compared with 02428 without SBPH infestation(i.e.at 0 h).21 of them were down-regulated in Pf9279-4 and 8 of them were up-regulated.64 DEPs were found at 6 h after SBPH infestation with 28 of them being down-regulated and 36 of them up-regulated.39 DEPs were identified at 12 h after SBPH infestation with 15 of them being down-regulated and 24 of them up-regulated.These DEPs were classified into stress response,photosynthesis process,protein metabolic process,carbohydrate metabolic process,energy metabolism,cell wall-related protein,amino acid metabolism,catalytic function,transcription and others.Physiological index activity were performed between Pf9279-4 and 02428.SOD and GSH activities in Pf9279-4 were significantly higher than that in 02428 at each time point(P<0.01);CAT,POD and hydroxyl radical inhibition activities in Pf9279-4 were significantly lower than that in 02428 at each time point(P<0.01).In this study,the protein level of SAM synthetase was up-regulated in Pf9279-4 than in 02428 at 12 h after SBPH infestation in the SA pathway,so we hypothesized that the Pf9279-4 rice plants defend against BPH through activation of the pathway of the SA-dependent systemic acquired resistance.