| This paper used the artificial fungal disc inoculation method with12strains of Gaeumannomyces graminis var.tritici to determinate the virulence and select potent virulence strains for the follow-up tests studied the effect of temperature on wheat take-all disease analyzed the diversity of relative fitness of Gaeumannomyces graminis var.tritici preliminarily and explored the influence of different wheat varieties,N,P,K fertilizers, and eight kinds of fungicides on the relative fitness of Gaeumannomyces graminis var.tritici.By determinating the tested12strains of Gaeumannomyces graminis var.tritici, the analysis to the disease index and average dry weight loss showed that the disease index and the average dry weight loss of strain AnH2was the largest, up to86.11%and43.92%respectively, following by strain AnH8. In view of the testing requirements, strain AnH8was more suitable for all disease fungal disc inoculation study. The virulence of most strains of AnHui is stronger than HeNan, which provides a theoretical basis for future researches.The relationship between soil temperatures and development of wheat take-all disease on wheat seedling was studied. By researching on disease severity of wheat take-all disease of wheat in5,15,20,25,30℃five different temperatures, the result indicated that the fungus infected wheat seedling under five temperature conditions. When the temperature raised, the symptoms occurred earlier, the root in the column turned brown and rotting, the disease became more severe which expressed as the higher values of the black root rate, the shortest values of root length and plant height. When the temperature is higher than20℃, the disease index decreased to84.22%when the temperature is greater than25℃, the disease severity quickly reduced to47.67%.So15℃～25℃was the optimum temperature for development of take-all, it′s not favorable for the occurrence of disease regardless while the temperature was too low or too high.The relative fitness of wheat cultivars to wheat take-all fungus strain AnH8of AnHui had been analyzed and the results showed that different20wheat cultivars behaved different relative fitness, the difference among the wheat cultivars was beyond significant level of5%. Strain AnH8behaved stronger relative fitness to Newmai18, less relative fitness to Zhoumai18, the least relative fitness to Ningmai13and other varieties have high relative fitness. The least relative fitness to Ningmai13and other varieties have high relative fitness. In addition, the study also founded that the relative fitness of the semi-winter varieties were stronger than spring varieties, it indicated that semi-winter varieties infected with Gaeumannomyces graminis var.tritici more easily.The mathematical model of the relation among nitrogen (x1), phosphorus (x2), potassium(x3) fertilizer established by quadratic regression general rotary unitized design methods, was y=1.05684-0.00908x1-0.00294x2+0.00183x3+0.00026786x1x2+0.0004629x1x3+0.000083333x2x3-0.00008086x12-0.00005001x22-0.00024822x32, the coefficient of determination of the model R2=0.8626. Correlation analysis of the regression equation showed that the effect of nitrogen, phosphorus and potassium three kinds of main nutrient elements on relative fitness of Gaeumannomyces graminis var.tritici is not significant, the order of influence was N>P>K, but interactions between nitrogen, phosphorus and nitrogen, potash were reached the significance level. The incidence of wheat take-all was very serious when nitrogen and phosphate fertilizer high in volume, and to reduce the amount of nitrogen fertilizer use could reduce the occurrence of disease effectively when the phosphate fertilizer usage is high No matter how much nitrogen or phosphorus fertilize used, to reduce the use of potash fertilizer can reduce the occurrence degree of disease.By conducting seed dressing processing with some fungicides as prochloraz, propiconazole, tebuconazole, diniconazole, triadimefon, carbendazim, difenoconazole and fludioxonil to wheat cultivar before sowing and after inoculated by Gaeumannomyces graminis var.tritici and investigation of the relative fitness of Gaeumannomyces graminis var.tritici, the results showed that the relative fitness had a significant difference in the different fungicides, which carbendazim prevention and control of minimum relative fitness F value is0.2887difenoconazole prevention the relative fitness of F value of0.5247. Through toxic nutrient media law, the toxicity testing results showed that the EC50of prochloraz, propiconazole, tebuconazole, diniconazole, triadimefon, carbendazim and difenoconazole was0.19μg/ml,0.23μg/ml,0.29μg/ml,0.50μg/ml,0.63μg/ml,0.69μg/ml,0.71μg/ml,12.89μg/ml.The results showed that the growth inhibitory concentrations of different pesticides on mycelia had a significant difference in EC50, fludioxonil had the best inhibiting effect on the mycelial growth, followed by the difenoconazole, and prochloraz had the least inhibiting. |
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