Molecule Detection Of Puccinia Polysora And Resistance Mechanism To Southern Corn Rust In Maize

Southern corn rust, caused by Puccinia polysora Underw., is becoming serious in recent years and is a potential threat for maize production in China. With the purpose of studying on the epidemic regularity and resistance mechanism of southern corn rust, specific detection of the pathogen was carried out, and the histopathological characters of P. polysora during infection and colonization in four maize inbred lines were investigated by trypan blue clearing staining technique. Meanwhile, the dynamic change of biochemical indicators was determined. The biochemical indicators associated with southern corn rust resistance were figured out. The main results of this study were as follows:1. Southern corn rust DNA was amplified by universal primer, and the ITS sequences were obtained after gel extraction, cloning, and sequencing. The length ITS was 692 bp. Primers specific for P. polysora were designed using the primer-design software primer 5. The specific primers were used to amplify some fungal pathogens of maize and healthy tissues. A fragments 365 bp in length was amplified from the pathogen P. polysora only. The detection sensitivity was 10 pg/μL DNA.2. The histopathological characters of P. polysora during infection and colonization in four maize inbred lines were investigated by trypan blue clearing staining technique. The process of pathogen invasion included five phases: spore germination and germ tube formation, appressorium formation, infection, formation of haustorium, and expansion of mycelium. The differences between spore germination and germ tube information were not very distinct. On the countary, when the pathogen invaded into the host cells of resistant maize lines, the growth and expansion degree of hyphae were distinguished. In the resistant lines, it was later to form primary hyphae, haustoriums and secondery hyphae, and less of haustoria in cells, fewer branches of hyphae and lower growth of hyphae than that in the susceptable lines.3. After inoculation, the soluble protein contents in resistant and susceptible inbred lines were reduced, which were not associated with disease resisitance. The dissoluble sugar content was higher in the susceptible inbred lines than that in the resistant inbred lines. The resistant inbred lines showed higher increasing rate of the free proline content and the activity of PAL than the susceptible inbred lines. There was no certain correlation on resisitance of the activity of PPO in resistant and susceptible inbred lines. The resistant inbred lines showed higher increasing rate of the activity of SOD and POD. Furthermore, the activity of SOD and POD maintained high level throughout the study. The activity of CAT of the resistant inbred lines was always higher than the susceptible inbred lines and the control. Therefore, at the seedling stage of maize, the dissoluble sugar and the free proline contents and the activity of PAL, SOD, POD, and CAT in leaves can be used as the indictors for screening resistance to P. polysora in maize.