| Maize is the world and China’s major food, fodder, and industrial crop. However, the yield loss is more than50%on a regular basis due to the hazards of the maize leaf blight caused by Exserohilum turcicum, which occurs frequently in maize growing areas of China, resulting in increasing threat to the safety of maize production and a direct impact on the sustainable development of maize. The most economical and effective method to prevent and control maize leaf blight is to screen and cultivate resistant varieties against Exserohilum turcicum as researchers widely used artificial inoculation method to identify resistant varieties in China and abroad. This test was to analyse firstly diverse artificial inoculation methods with different pathogenicity degree and screen the most effective and economical inoculation method available for different areas for various reasons. Then the resistance of widely-planted maize varieties resources against Exserohilum turcicum in Sichuan province were evaluated. At the same time applying three fungicides on Exserohilum turcicum population were to test their antibacterial activity and analysed the differences of fungicides virulence on Exserohilum turcicum population. And RAPD was taken as to analyse polymorphism of Exserohilum turcicum population genetic diversity in Sichuan Province.Filtering the the optimum growth stage for artificial inoculation by bonsai was the frist step of test. Then we employed4different means of artificial inoculation including spore suspension liquid spray, crushing corn diseased leaves, bacteria filling heart and contaminated sorghum grain, to inoculate corns in field. Then we compared the incidence and disease severity of corns with artificial inoculation to that of natural disease, so as to turn out the most economical and effective method was the contaminated sorghum grain inoculation. Following in this way, we identified100maize varieties in Sichuan Province, indicating that no varieties are immune to Exserohilum turcicum,germplasm resources2,33,51,14were highly resistant,resistant, moderately resistant and susceptible to Exserohilum turcicum respectively, accounting for2%,33%,51%,14%separately. The resistance of most varieties was concentrated in moderate resistance and susceptibility. Moreover, there was no highly susceptible variety.Pathogenic plants were collected in the main maize producing areas in Sichuan Province and58pure strains were obtained by single spore isolation in pure culture. Then we applyed three fungicides namely Imazalil, Diniconazole, Carbendazim to these58Exserohilum turcicum respectively. The result showed that Carbendazim got the Exserohilum turcicum virulence changing in the smallest difference, Imazalil followed up, and Diniconazole got the Exserohilum turcicum virulence changing in the biggest difference. Three fungicides on the virulence of Exserohilum turcicum difference were significant, Imazalil in the highest, Diniconazole in the medium, Carbendazim in the lowest, indicating that the commonly-used Carbendazim had a low effect and unused Imazalil&rarely-used Diniconazole may have a better effect in production, providing a theoretical basis for the future study of chemical control of leaf blight.58Exserohilum turcicum genomic DNAs were extracted by the means of CTAB, then genetic polymorphism of these DNAs were analyzed at the molecular level by RAPD. The5amplified polymorphic and stable random primers were screened out from the52RAPD random primers, with a total amplification of51bands, ranging from250to2000bp. There were36polymorphic bands with a polymorphism rate of70.59%. To some degrees, it showed that maize leaf blight pathogen strain groups in Sichuan Province ha an abundant genetic diversity. Genetic similarity coefficients (GS) were beteen0.4091to0.9545, Cluster analysis manifested that58strains could be divided into six groups and the cluster results had no manifest correlation with cultivars isolated strains, sampling points. |
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