Methods Of Predicting Wine Grape Downy Mildew In The Eastern Foot Of Helan Mountain

Grape downy mildew caused by Plasmopara viticola is an important disease on leaves of Vitis vi-nifera,and it is also a common and most serious grape diseases,which seriously restricts the high qual-ity and production of wine grape in the eastern foot of Helan mountain.Although scholars and experts have done a lot of research on the pathogenic,occurrence and control of grape downy mildew in the eastern foot of Helan mountain,there is still a lack of systematic research on monitoring and prediction methods of grape downy mildew in the eastern foot of Helan Mountain.In order to provide scientific theoretical basis for early warning and prevention of wine grape downy mildew in the eastern foot of Helan mountain.In this study,sporangium captured,real-time PCR and GIS were used to monitor and predict wine grape downy mildew in time and space.Main contributions of this work are as followings:(1)From 2016 to 2018,wine grape downy mildew in three typical vineyards was systematically investigated in the eastern foot of Helan mountain.This study used 11 mathematical models,such as Linear,Quadratic,Growth,Cubic,S,Exponential and Logistic,to simulate the seasonal epidemic dy-namic curve of wine grape downy mildew on Cabernet Sauvignon in the eastern foot of Helan Mountain.It was great that Logistic model could best reflect the seasonal epidemic dynamic of wine grape downy mildew in the eastern foot of Helan Mountain,with high accuracy(R2?0.946).The exponential growth phase of wine grape downy mildew was July 22 to August 8,with the highest disease index is 0.98;the logistic growth phase was August 9 to October 10,with the highest disease index is 47.69:the decline phase was from October 11 to the end of grape growing,and the peak of disease index of was less than 60 in eastern foot of Helan Mountain.Apparent infection rate was the highest in exponential phase(r=0.1266),which was the best period to control grape downy mildew with chemical pesticide.Al-though the occurrence degree of wine grape downy mildew among different varieties had distinctions,it abided by the Logistic model.In this study,the model of wine grape downy mildew was preliminarily clarified,which provided theoretical basis for early warning of wine grape downy mildew in the eastern foot of Helan mountain.(2)The study explores the diffusion regularity and revealed the epidemic mechanism of the spo-rangium of P.viticola,and provided a theoretical basis for the prediction,prevention and control of wine grape downy mildew in the eastern foot of Helan mountain.From 2016 to 2018,this study took the sporangium of P.viticola as object and the airborne sporangium density of P.viticola monitored with quantitative airborne romote-controlled spore trap in vineyard.The diffusion regularity of the spo-rangium of P.viticola with the disease index and meteorological factors discussed in depth,it's aim was that evaluated the prevalence of wine grape downy mildew and explored the key influence factors of meteorological factors in the eastern foot of Helan mountain.The results showed the daily dynamics of sporangium diffusion of P.viticola revealed dual-peak at 10:00 am and 12:00 pm,and higher at 10:00 am,and the sporangium was mainly distributed at near canopy in the vertical direction in vineyard.The seasonal dynamic of sporangium of P.viticola is the kind of inverted "U" type,that slowly riseed firstly and then fell to a lower level.There was better correlation among airborne sporangium of P.viticola with the disease index,temperature,humidity,the time of leaf wetting in vineyard,and these factors also had an omportant affect on sporangium diffusion of P.viticola.The sporangium density of P.viti-cola was significantly correlated with the disease index,the average 7-day relative humidity,the aver-age 7-day leaf surface wetness duration,the daily average temperature,and the daily leaf surface wet-ness duration,the correlation coefficients were-0.374,-0.394,-0.473,-0.290,and-0.305,seperatively.The method of quantitative airborne romote-controlled spore can be used to study the diffusion regular-ity of sporangium of P.viticola in the eastern foot of Helan mountain.The correlation that the sporan-gium density with the disease index and meteorological factors was explored in the study,and it would provide new ideas for the early warning and effective prevention and control of grape downy mildew.(3)The objective of this study is to establish a real-time PCR detection system of P.viticola based on the pathogen sequence information,and to provide a scientific basis for early diagnosis and prediction of grape downy mildew.According to the cox2 gene sequence of P.viticola in GenBank,a pair of specific primers F-cox-Pv/R-Pv,was designed to establish and optimize the conventional PCR and real-time PCR reaction system.The mycelium DNA of 14 species of grape and other crop patho-gens and antagonistic fungus were used to detect the specificity of conventional PCR and real-time PCR.The sensitivity and repeatability of the system were also evaluated.The pathogen DNA in the grape leaves during the latent infection period of artificial inoculation with P.viticola was quantitatively de-tected by the established real-time PCR system.The relationship between inoculation time and latent infection amount of P.viticola in the grape leaves was analyzed by SPSS 19.0 software.The primers designed in this study had high specificity.A 139 bp fragment of genome DNA was only amplified from y conventional PCR P.viticola.The detection results of real-time PCR assays showed that the primers had only one absorption peak for P.viticola,and no product absorption peak was detected for other test strains.The sensitivity of conventional PCR was 10 pg·?L-1 genomic DNA,while the sensi-tivity of real-time PCR was 0.1 pg·?L-1 which was 100 times higher than that of the conventional PCR.The linear relationship between Ct and concentration was constructed by using recombinant plasmid containing cox2 gene fragment as standard material.The standard curve was y=42.27-3.36x,with the correlation coefficient of 0.997 and amplification efficiency of 98.50%.The curve showing a good li-near relationship at 2.4×103?2.4×109 copies/?L.The real-time PCR system was used to detect the pa-thogen DNA in the grape leaves during the latent infection period of artificial inoculation with P.viti-cola.The results showed that the latent infection of P.viticola in the grape leaves increased exponen-tially with the change of inoculation time,the curve was y=6.34×104·e0.084x,with the correlation coeffi-cient of 0.936.The real-time PCR system could detect the P.viticola DNA 6 h after inoculation,and the DNA content was 5.68×104 copies/?L.The sensitivity of the established real-time PCR system for de-tection of grape downy mildew is much higher than that of conventional PCR,and the specificity and reproducibility of this real-time PCR system are good.There was better linear relationship between Ct and concentration,and the amplification efficiency is higher.This method can be used to quantitatively detect the latent infection of P.viticola.(4)Geographic information system(GIS)and geostatistical analysis were used to analyze the spa-tial structure of wine grape downy mildew at three scales and different periods in the eastern foot of Helan mountain in 2017.The spatial distribution pattern of downy mildew of grapes at three scales and different periods was simulated by ordinary Kriging based on different models.The results showed that three scales of wine grape downy mildew showed distinct spatial structures at different occurrence stages,and the semi-variograms mainly were exponential and gaussian.The spatial patterns of wine grape downy mildew occurrence at three scales were different,the spatial autocorrelation is better and the distribution is aggregated from 176.8?328.9 m at microscale and mesoscale,while highth spatial variability is greatly influenced by random factors and spatial lower autocorrelation at macroscle.Spa-tial distribution simulation can directly simulate the dynamic changes of wine grape downy mildew in time and space,showing the occurrence degree and range of wine grape downy mildew of in the eastern foot of Helan mountain.GIS was used to study the occurrence and spread of wine grape downy mildew in different scales and different occurrence periods,will provide a better basis for the prevention and control of grape downy mildew in larger area.(5)The wine grape downy mildew forecasting model was established by GIS in the eastern foot of Helan mountain,and the model was y=-34.400+1.824x0+0.640x1+2.370x2(y:disease index;x0:disease index before 15-day;x1:15-day average wetting time;x2:15-day average temperature).ArcGIS 10.2,a geographic information software platform,was used to simulate the distribution of predicted and meas-ured values of wine grape downy mildew in the eastern foot of Helan mountain.The results showed that the regional prediction technology of grape downy mildew based on GIS was more intuitive and accu-rate,the predicted and measured results are basically consistent,the accuracy of early warning was 76.60%by random sampling test.The wine grape downy mildew forecasting model based on GIS can better reflect the different occurrence degree of grape downy mildew in the eastern foot of Helan Mountain,and the areas and the proportions of different occurrence degree of grape downy mildew will be highly efficient statistics.