Study On The Resistance Of Maize To Northern Corn Leaf Blight And Southern Corn Rust

Northern corn leaf blight (NCLB), caused by the fungus Exserohlium turcicum (Pass.) Leonard etSuggs, is a destructive foliar disease of maize. Identifying and screening the maize resistant germplasmresources to NCLB were conducted to find ideal resistant source. The practicabilities of5molecularmarkers linked to Ht2gene were detected. A comparative proteomic study was conducted to explore themolecular mechanisms underlying the defense responses of the maize resistant line A619Ht2to S.turcica race13. Southern corn rust induced by Puccinia polysora Underw., mainly occurres in tropicaland subtropical area. Four F2:3populations from crossing four resistant inbred lines and susceptible lineHuangzaosi were identified their resistance to southern corn rust and the resistant inheritancecharacteristics were explored. The resistant gene of Jiku12was mapped. Main results of our study weresummarized as follows:1.499maize germplasms inoculated with0,1and N races of S. turcica respectively to identifytheir resistance to NCLB. Among the499germplasms,96germplasms displayed resistant to all thethree tested races and accounted for19.24%of499germplasms.150maize germplasms inoculated with0,1, N and123N races of S. turcica respectively and only8germplasms were resistant to all fore raceswhich accounted for5.33%of499germplasms.2.11maize inbred lines with/without Ht2gene were used by detecting the practicability of5molecular markers linked to Ht2gene, including3SSR markers,1SNP marker and1CAPS marker.The resultes indicated that there was almost none amplified band or sequence which was specific to Ht2gene. Those5markers can not be used for identifying the present of Ht2gene in various maize lines.3. Leaf proteins were extracted from mock and S. turcica race13infected maize resistant lineA619Ht2after inoculated for72h and analyzed for differential protein expression usingtwo-dimensional electrophoresis and mass spectrometry identification. One hundred and thirty-sevenproteins showed reproducible differences in abundance by more than2-fold at least, including50up-regulated proteins and87down-regulated proteins. Forty-eight protein spots were successfullyidentified by MS analysis, which included10unique,6up-regulated,20down-regulated and12disappeared protein spots. These identified proteins were classified into9functional groups andinvolved in multiple functions, particularly in energy metabolism (46%), protein destination and storage(12%), and disease defense (18%). Some defense-related proteins were upregulated such asβ-glucosidase, SOD, polyamines oxidase, HSC70and PPIases; while the expressions ofphotosynthesis-and metabolism-related proteins were downregulated by inoculation with S. turcica.4. Four F2:3segragated populations were constructed by using four inbred lines resistant tosouthern corn rust which were Jiku6, Jiku12,5362and Liao2204as resistance-donor crossed tosusceptible line Huangzaosi. Four inbred lines and all the members of F1population were resistant tosouthern corn rust, while the inbred line Huangzaosi was susceptible. The resistant inheritance analysisindicated that only the segregation ratio of resistance and susceptibility of F2:3populations from Jilu12/Huangzaosi fited a ratio of1:2:1, as indicated by the χ2=1.1633and P=0.5590. The resistanceconditioned by Jiku12was controlled by one dominant gene.5. A328F2:3populations were constructed from Jilu12/Huangzaosi to conduct the gene mappingexperiment. Results of resistance identification furthern showed that the resistance gene of Jiku12wasone dominat gene, since77resistant lines,165segragating lines and86susceptible lines were obserbedand fited the segregation ratio of1:2:1.5SSR markers located on the chromosome bin10.02wereidentified to be linked to resistance gene of Jiku12and the distance of this gene from the nearest markerphi063was4.2cM. According to an allelism test between Jiku12and Qi319, the resistance gene ofJiku12was non-allelic to the RppQ of Qi319. We suggested designating the resistant gene conferred byJiku12as Rpp12temporarily.