Codominance Functional Marker of Bacterial Blight Resistance Gene Xa7 in Rice

[Objectives]A codominance functional marker of the broad-spectrum bacterial blight resistance gene,Xa7,of rice was identified for accurate detection,generation tracking,and differentiation between homozygous and hemizygous genotypes of the gene.[Methods]A potential functional marker containing four primers was designed using Premier 5 software and based on the differences on the sequences of Xa7,xa7,and allele-free genomes.The molecular distinctness of the marker in different materials was verified by PCR.Three crossbreed lines of Xa7 and their parents were inoculated with seven bacterial blight strains at the booting stage to examine the affected agronomic traits at maturation.[Results]The homozygous R084 of Xa7 could be amplified into a 91 bp band and the Nip free of allele with a 153 bp band,while the heterozygote Nip/R084,91 bp and 153 bp bands.The candidate codominance marker,Xa7fun,amplified fragments that matched the predicted target bands.No 91 bp fragment was amplified from 18 germplasms of varied types,indicating a lack of Xa7 in them.Whereas Ry1,Ry2 and Ry3 had a 91 bp band,suggesting the inclusion of homozygous Xa7.Under an elevated temperature,Huazhan responded to the seven bacterial blight pathogens as highly susceptible(HS),intermediate susceptible(MS),or susceptible(S);R084 to six of the seven pathogens(HNA1-4,FuJ,GDA2,GD1358,PX086,and YN24)as highly resistant(HR),intermediate resistant(MR)or resistant(R);Ry-1 to five pathogens(GDA2,HNA1-4,FuJ,GD1358,and YN24)as HR or MR;Ry-2 to five pathogens(GDA2,GD1358,HNA1-4,PXO86,and YN24)as HR or R;and Ry-3 to 6 pathogens(HNA1-4,FuJ,GDA2,GD1358,PXO86,and YN24)as HR or MR.Therefore,the infiltration of Xa7 in the improved crossbred lines RY-1,RY-2,and RY-3 significantly accentuated the blight resistance of Huazhan.[Conclusions]Homozygous or hemizygous Xa7 could be accurately differentiated by the currently identified codominance functional marker Xa7 fun.The Xa7 introgression did not significantly alter the critical agronomic traits in the hybridization from generation to generation and could be safely applied in breeding rice varieties with bacterial blight resistance.

Resistance Evaluation of Indica Rice Varieties with Bacterial Blight Resistance Genes Xa21 and Xa23 under Different Genetic Backgrounds

[Objectives]The paper was to evaluate the resistance of indica rice varieties with bacterial blight resistance genes Xa21 and Xa23 under different genetic backgrounds.[Methods]The rice materials with bacterial blight resistance genes Xa21 or Xa23 were used as the donors,and those without the genes were used as the receptors.By back crossing,composite crossing and other methods,combined with molecular marker-assisted selection(MAS),the materials with Xa21 or Xa23 gene,and their sister lines with/without Xa21 or Xa23 gene were inoculated with 7 widely used physiological races of Xanthomonas oryzae,and the resistance of the materials to bacterial blight was analyzed.[Results]The proportions of cumulative resistance(HR,R,MR)of rice materials with resistance gene Xa21 were HNA1-4/PXO86(84.62%)>YN24(82.14%)>GD1358(73.08%)>PXO99(67.86%)>GDA2(63.33%)>FuJ(6.67%),indicating that the materials with Xa21 gene had no resistance to bacterial blight induced by strain FuJ,but for other strains,there were still 36.67%-15.38%of the materials susceptible to the disease.The cumulative resistance(HR,R,MR)of the materials with Xa23 gene was over 76%,but there were still 23.02%-15.52%of the materials that had no resistance to the 7 strains.The analysis of variation coefficient of lesion length showed that the resistance of materials with Xa21 or Xa23 genes varied among strains,or the resistance to the same strain varied among materials.Correlation analysis demonstrated that there was significant or extremely significant positive correlation between strain GDA2 or HNA1-4 and other 6 corresponding strains in the materials with Xa21 gene,and there was extremely significant positive correlation between strain YN24,GD1358 or PXO86 and other 6 corresponding strains in the materials with Xa23 gene.Selection of these strains for resistance identification could improve the efficiency of breeding.Analysis of sister lines showed that bacterial blight resistance of Xa21 or Xa23 genes was related to the donor of the materials.Correlation analysis showed that the resistance of the materials with Xa21 gene had extremely significant positive correlation with parents(R=0.5725**),and the resistance of the materials with Xa23 gene had significant positive correlation with parents(R=0.2212*).[Conclusions]The study provides the reference for molecular resistance breeding of bacterial blight.

Design of a 10 kV SiC MOSFET-based high-density, high-efficiency, modular medium-voltage power converter

Simultaneously imposed challenges of highvoltage insulation,high dv/dt,highswitching frequency,fast protection,and thermal management associated with the adoption of 10 kV SiC MOSFET,often pose nearly insurmountable barriers to potential users,undoubtedly hindering their penetration in mediumvoltage(MV)power conversion.Key novel technologies such as enhanced gatedriver,auxiliary power supply network,PCB planar dcbus,and highdensity inductor are presented,enabling the SiCbased designs in modular MV converters,overcoming aforementioned challenges.However,purely substituting SiC design instead of Sibased ones in modular MV converters,would expectedly yield only limited gains.Therefore,to further elevate SiCbased designs,novel highbandwidth control strategies such as switchingcycle control(SCC)and integrated capacitorblocked transistor(ICBT),as well as highperformance/highbandwidth communication network are developed.All these technologies combined,overcome barriers posed by stateoftheart Si designs and unlock system level benefits such as very high power density,highefficiency,fast dynamic response,unrestricted line frequency operation,and improved power quality,all demonstrated throughout this paper.