Characterization Of Maize Resistance To Puccinia Polysora

Southern corn rust (SCR) is a destructive disease in the summer maize area andcauses more than10%yield loss in disease epidemic years. For finding and utilizingthe new SCR-resistance germplasm, screening of1589accessions to SCR was carriedout by inoculation in the fields during2008-2012. The results showed that26accessions were highly resistant, accounting for1.64%;138accessions were resistant,accounting for8.62%;382were moderately resistant, accounting for24.04%;489were susceptible, accounting for30.77%;555were highly susceptible, accounting for34.93%. There were more resistant type lines (HR, R and MR) in imported maizegermplasm. By re-screening26accessions, including18inbred lines,3landraces，4Zimbabwe lines and Dr11from CIMMYT were confirmed with highly resistance tosouthern corn rust that will provide new SCR-resistance source for breeding in China.Simple sequence repeat (SSR) markers were adopted in heterotic parts of39maize inbred lines of resistance to SCR. Forty SSR primers giving stable amplifiedprofiles detected115alleles among the lines tested. The UPGMA analysis classified45inbred lines into3clusters, which corresponded to the heterotic groups determinedby pedigree analysis.17haploid types were identified from39disease-resistantresources. Resistance resources from same place belong to the same type single times.It is necessary to reinforce researches of germplasm enhancement, improvement andinnovation in that the less of germplasm types in our country.Scanning and transmission electronic microscopy technique was used to studythe cytological changes of the host in the process of infection by the pathogen of P.polysora. Rssults were as follows: spore germination, germination of spores andmycelia growth were earlier,more and faster in resistant rice than that in susceptiblerice.There were hyphae on intercellular space and a large number of haustoria in thecell at the early of infection process.The plasma of host cell where mitochondrion wasrich accumulated around the haustorium. A large number of phenolics appeared inmesophyll cells, intercellular space and epidermal cells on resistant material. Most of the intrusion is from the leaf epidermis and less of intrusion is from stoma andintercellular space.The top of Hyphae produced degradation enzyme into degradationof cell wall and making its loose until resolution.F3populations were constructed from Liao2204/Huangzaosi to conduct the genemapping experiment. Results of resistance identification furthern showed that theresistance gene of Liao2204was one dominat gene, SSR markers located on thechromosome bin10.00were identified to be linked to resistance gene of Liao2204and the distance of this gene from the nearest marker umc1380was9.6cM. Wesuggested designating this gene as RppL2204temporarily.