| Bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the three most seriousdiseases in rice. Identifying and utilizing new resistant resources, developing and planting varietieswhich resist to bacterial blight are the safe, economic and effective way to control this disease. Therewere three parts in the present study. The candidates Tainong(TN69) and Huimei(HM) resistance tobacterial blight and segregating generations, crossed with susceptive donors, are used as the researchmaterials and inoculated by suspention of bacterial blight6pathogen races in seedling-and adult-stageto validate the disease resistance. Genetic analysis and preliminary mapping are also been done. Theresistant gene xa5in IRBB5is introduced into the CMS maintainer line Tian-feng B(TFB) and therestorer line Hua-zhan(HZ) of hybrid rice ‘Tian-you-hua-zhan’ to improve its bacterial blight resistanceby backcross and marker-assisted selection(MAS). Meanwhile, the gene Xa7harbored by XQR6-7andZhen R084(ZR084) is pyramided into TFB and HZ respectively with xa5by top-cross method. Thepolymerization effect is analyzed to the dual gene polymerization plants and lines. The main results areas follows:(1) TN69, a japonica variety, displays susceptible and horizontal resistance to bacterial blight atseedling-and adult-stage, respectively. The resistant intensity of F1plants, crossed with TFB, isapproximate to TFB. The genetic analysis of F2populations to race ZHE173indicated that thehorizontal resistance was controlled by complex quantitative trait.(2) The identification of resistance to bacterial blight indicated that the resistant reaction differedbetween individuals of HM, a developing indica line. There are three kinds of resistant spectrumbetween lines of HM which were named as HM11, HM16and HM42, respectively. The allelic testshowed that the resistant gene in lines HM16and HM42was allele to Xa23. Genetic analysis madeclear that the resistance to races CR1and CR6in lines HM42and HM11was regulated by quantitativetrait and single dominant gene respectively, which whether allele to Xa3remains unknown.(3) Resistant reaction manifested that the resistant intensity of the improved plants and lines of HZcontaining the homozygous resistant gene xa5approached the donor parent IRBB5and the resistance toall the races showed no difference among the improved plants or lines. However, there were differenceon improved plants and lines of TFB to CR1, ZHE173, C6and so on, The parts of the plants or linesshowed moderate resistance and moderate susceptibility to some bacterial blight pathogen races such asZHE173.(4)8improved individuals in BC3F1generation of acceptor TFB and HZ containing the gene xa5with the former got rid of the restorer genes were obtained respectively. And one individual whichbackground recovery rate over97%was gained from above improved individuals of TFB and HZ inBC3F1generation respectively.(5) Background selection demonstrated that the discrepancy between the highest and the minimumrecovery rate of selected individuals from backcrosses of TFB and HZ reach up to15.89%and22.7% respectively. The background recovery rate showed a small difference among the same lines and a largedifference between the lines. It implied that the appropriate background selection could be recovery toacceptor TFB and HZ to accelerate the backcross breeding process.(6) The analysis of polymerization effect on xa5and Xa7showed that the dual gene homozygousindividuals and lines of HZ was resistant and susceptible to PXO99Ain Hai-nan and Hang-zhourespectively. And the improved individuals of TFB with the gene-types xa5xa5Xa7Xa7andxa5xa5Xa7xa7displayed resistant and susceptible to race PXO99Arespectively. The results indicatedthat the polymerization effect of xa5and Xa7differed under different environmental conditions, geneticbackground and gene-types. |
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