| Bacterial blight (BB) caused by Xanthomonas oryzae pv. Oryzae(Xoo) is one of the three most destructive diseases in rice. BB damage on this crop was reported to range from20to30%and could sometimes get as high as50%and even crop failure. Widely grown rice in China generally have no or single resistance genes, and planting in large area for a long time easy to lose resistance to diseases. Thus the most economic and effective environmental protection measures to control bacterial blight is Cultivating and planting resistant varieties. The lab early has put the two dominant resistance genes Xa21and Xa23on the same chromosome which have strongest resistance spectrum imported hybrid rice restorer K608R, after6to7generations back occurring simultaneously selfing, obtained the consistent with K608R agronomic traits of disease-resistant breeding materials K608R21and K608R23. On this basis, we take the K608R23as female parent, then taking K608R21and rice near isogenic line IRBB5which carrying a recessive resistance to bacterial leaf blight gene ?a5as male parent respectively,through the study of the resistance of F2and F3hybrids identification and molecular marker detection, established the Xa23+Xa21, Xa23+?a5polymerization technology system, the late comparative analysis polymeric material disease resistance of different genotype, and analysis the Xa23+Xa21, Xa23+?a5aggregation effect, thus further speculating and expounding the mechanism of the Xa23gene.The main results are as follows:1. Got the Fi polymerization plant seedling from Parent K608R21, K608R23hybrid,then taking MAS analysis and inoculating bacterial leaf blight P6,the result showed that the polymerization plant K608R23/K608R21had existed.2. Bioinformatics comparative analysis was used to optimize the function of the Xa21marker genes, and design new molecular detection primer U1/I2, which making the PCR fragments between parents are more likely to separate.3. Analysised the Xa23test primer RM206in the aggregate, the bases only differ between8bp between K608R21with K608R23parents.4. Plantting the K608R23/K608R21Fi seeds and obtained F2generation plants, then Screening of6plants of Xa23homozygous and Xa21hybrid(Xa23++/Xa21+-) and1plant of Xa21homozygous and Xa23hybrid(Xa23+-/Xa21++) with MAS.5. K608R23/K608R21Fi hybridization plant and parent plants real-time quantitative PCR analysis showed that Xa23gene expression induced by pathogen P6, and its expression has differences between Xa21+-1Xa23+-plant and Xa21-/Xa23++plant, At24h and48h, Xa23gene expression quantity have been raised, and the Xa21-1Xa23++plant raised more obvious.6. Obtained Fi generation by Parent K608R23and IRBB5crossed, planting the F1generation and got F2generation, then won the hybrid plants containing the following different genotype combinations by using MAS detection, xa5++/Xa23++(2plants), xa5++/Xa23+-(2plants), xa5++/Xa23-(2plants), xa5+-/Xa23++(6plants), xa5+-/Xa23+-(7plants), xa5+-/Xa23-(7plants), xa5--/Xa23++(3plants), xa5--/Xa23+-(5plants), xa5--/Xa23-(6plants).7. Inoculated P6pathogen to K608R23/IRBB5F2generation of different genotypes of polymerization plant, the results indicate that, the disease resistance in different genotype combinations of polymerization plants are different, among them, the polymerization plants xa5++/Xa23++, xa5++/Xa23+-, xa5+-/Xa23++,xa5+-/Xa23+-achieve high levels, and the presence or absence of xa5genes do not directly affect the overall resistance of plant when Xa23existed.8. Inoculated P6pathogen to K608R23/IRBB5F2generation of different genotypes of polymerization plant, taking rice leaves after48h, then extracted RNA, and taken Xa23gene semi-quantitative RT-PCR analysis, the results show that the Xa23gene expression is induced by the P6pathogenic bacteria, and in the presence of xa5gene, Xa23gene expression is not affected.9. Planting K608R23/K608R21F2generation plants, selfing obtained F3generation plants, MAS molecular detection obtained polymerization plant containing different genotype combinations, Xa21++/Xa23++(30plants), Xa21+-/Xa23++(67plants) Xa21+-/Xa23+-(50plants),Xa21++/Xa23+-(29plants)10. inoculated different kinds of physiological bacterial leaf blight to K608R23/K608R21F3generation of different genotypes,after15days and the disease spot stable, gathering inoculated leaves and taking the disease resistance and resistance spectrum analysis, the results showed that, Polymerization plants of different genotype have higher resistance than the plants which excluding resistance genes (Xa21--/Xa23--) or containing only a single resistance gene when inoculated the different physiological small kind of bacterial leaf blight, and achieves high resistance level. |
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