Pathogen Overwintering Temperature Threshold And Early Spring Prediction Of Wheat Powdery Mildew And The Dispersal Of Aerial Conidia Of Blumeria Graminis F. Sp. Tritici In Wheat Fields

The temperature threshold for over-winter of Blumeria graminis f.sp.tritici?Bgt?was studied,Real-time PCR method was used to quantitatively detect the latent infection level of Bgt in wheat leaves which sampled from different wheat growing areas,and field disease was monitored.The relationship between molecular disease index?MDX?,winter meteorological factors and early spring disease index?DX?of wheat powdery mildew was analyzed.The dispersal of conidia of Bgt in the air was studied by Burkard volumetric spore samplers.The main results are as follows:The first time found Bgt can over-winter at Zhangbei and Wanquan City in Hebei Province,Yongning town and Zhangshanying town in Beijing.The correlation between disease index of Bgt after overwinter and late January average temperature?the coldest ten days?or monthly average temperature of January?the coldest month?of air temperature and surface temperature were relatively much better,the correlation between surface temperature with disease index was better than that between air temperature with disease index.The relationship model between late January average temperature or monthly average temperature of January of air temperature and surface temperature was established,the temperature threshold of ten day average temperature or monthly average temperature of air temperature and surface temperature of wheat powdery mildew for over-winter were-14.6?and-13.7?,-13.4?and-12.4?,respectively.The field distribution of wheat powdery mildew in natural infection fields in Fangshan,Linzhou,Gongyi,Meixian and Qishan Cities in early spring was aggregate distribution,for artificial inoculation fields in Langfang City was aggregate distribution in 2014,and random distribution in 2015,the field survey sampling model of wheat powdery mildew was established:N=?1.47/x+0.60?/D²;At the same time,it was also clarif ied that the field distribution of pathogen latent infections of autumn wheat seedlings in the above areas was aggregate distribution,and sampling model of molecular detection of pathogen latent infection was established:N=?1.73/x+0.99?/D².The latent infection centers of fields in the autumn detected by Real-time PCR almost coincided with field disease centres of natural infection f ields in the spring,in artificial inoculation f ields of Langfang City,the consistency of disease index centers and the latent infection centers which detected in‘Jingshuang 16'planting field was better than in‘Zhongmai 2'planting field.The DX was extremely significantly correlated to MDX of each sampling fields in the different regions,and was also signif icantly correlated with the mean air temperature of January to March,early spring prediction model of wheat powdery mildew was constructed based on MDX?x?:y=686.29x-0.75?R2=0.7336,P=0.0008?,and also prediction model based on MDX?x₁?and the mean air temperature of January to March?x₂?was constructed:y=713.45x₁+0.1767x₂-1.64?R2=0.8014,P=0.0176?,both the two models can be used to predict the occurrence and epidemic of wheat powdery mildew in early spring.The dispersal of conidia of Bgt in the air was studied by Burkard volumetric spore samplers from 2015 to 2017,The number of Bgt spores captured by each spore trap was positively signif icantly correlated with each other,and positively correlated with wind direction,with the distance increased,the correlation coefficients showed a decreased trend;the number of captured spores was low during the early occurrence phase of wheat powdery mildew,however,the Bgt spores could be captured from 64 m away from the north or east of the pathogen source center when the disease index reached 17.72.In the same direction,there existed significant differences between the number of spores which captured from 20 m,40 m and 60 m away from the pathogen source center.There was a logarithmic ralationship between the dispersal distance and the spore numbers captured from 0 m,2 m,4 m,8 m,16 m,32 m and 64 m away from north of the pathogen source center,the relationship model based on the captured spore numbers?y?and the dispersal distance?x?was established:lny=-0.96*ln?x+1?+7.93?R²=0.9769,P<0.001?,the model can be used to describe the relationship between the number of captured spores with the dispersal distance,It laid a foundation for the application of spore trapper in wheat powdery mildew monitoring.The above results of the determination of overwintering temperature threshold of Bgt,the establishment of sampling techniques of early spring disease investigation or pathogen latent infections of autumn wheat seedlings,the establishment of early spring disease prediction model,the dispersal of aerial conidia of Bgt in wheat fields,all provided a theory basis for the monitoring,prediction and control of wheat powdery mildew.