Annual Dynamic And Dispersal Of Puccinia Striiformis F.sp.Tritici And Blumeria Graminis F.sp.Tritici In Gangu,Gansu Province

Wheat stripe rust and powdery mildew,caused by Puccinia striiformis.f.sp.tritici(Pst)and Blumeria graminis f.sp.tritici(Bgt),are the most important airborne diseases on wheat.Both are polycyclic diseases and have the risk of large-scale outbreak and epidemic.Pst and Bgt have the ability of long-distance dispersal via airborne spores from source areas to other regions.Thus,the core problem for both diseases is monitoring and managing the disease development of source area.Gangu County of Gansu Province is a mountainous area with various altitudes and diverse topographic where favor inoculum survival and epidemic development for Pst and Bgt.Pst could over-summer and overwinter in Gangu,where is the ideal place for produce the novel physiological races.However,powdery mildew has been increasingly serious wheat disease in Gangu,and Bgt could complete its disease cycle in this region.In this study,three ’Multi-vial Cyclone Samplers’ were placed at South Mountain,Valley and North Mountain in Gangu for collecting the airborne spores during 2013-2015,and the quantity of Pst and Bgt were quantified using real-time PCR.And the correlation between spore concentration and disease index was analyzed based on the disease investigation during March to May each year.Meanwhile,the correlation of meteorological data with the airborne spore concentration and disease index were analyzed,and models were built for predicting disease and airborne spore concentration based on the meteorological data that were collected from 2013 to 2015 in Gangu.The conclusions are summarized as follows:1.The airborne inoculum of Pst and Bgt exist year-round in Gangu,and the dynamic pattern showed the periodicity and seasonality with the growth of wheat.The spore concentrations in winter were lower than those in other three seasons for both the pathogens.2.No significant difference in the accumulated spore concentration of both disease between locations in the same season.However,there was significant difference for that between seasons in a year during 2013-2015.The accumulated spore concentration was the largest in spring,and least in winter.3.The time-series analysis demonstrated that the airborne spore concentrations of Pst for all the 10-day-spore-sum during three years at three locations were all significantly described by the autoregressive integrated moving-average ARIMA(1,0,0)models,while,those of Bgt fitted different models at different locations.ARIMA(2,1,1),ARIMA(1,0,1)and ARIMA(0,0,3)were used to described the spore concentrations of Bgt at South Mountain,Valley and North Mountain,respectively.4.Mostly,the spore concentration of both disease could vary with the disease index.The increase or decrease of spore concentration was similar with the tendency of disease index in the field.And the accumulated spore concentration and disease index was significantly correlated.5.Temperature variables,relative humidity and rainfall had significant influence on the spore concentration and disease development,which were the most important factors in the prediction models of wheat powdery mildew,as well as accumulative spore concentration.6.According to the onset time of wheat stripe rust observed in the field,and the correlation of airborne spore between locations at different time,we inferred that the dispersal may occur from south to north and from high altitude to low altitude for Pst in Gangu.As to Bgt,however,there were no obvious trend for the frequent exchange of spores among these locations.Monitoring the annual dynamics of airborne spores of Pst and Bgt in Gangu,and exploring the relationship between airborne spore concentration,disease index in the field and the local meteorological factors,which is helpful to develop better strategies to guide the disease management in Gangu and other places where wheat stripe rust and powdery mildew occurred frequent.