基于田间空气中病菌孢子囊浓度的葡萄霜霉病病情估计模型研究

Study on estimation model for grape downy mildew prediction based on airborne sporangium concentration of Plasmopara viticola in field

【目的】明确沈阳地区空中病菌孢子囊浓度、气象因素(空气温度、相对湿度、降雨量和风速)对葡萄霜霉病田间病情发展的影响,开展基于田间空气中孢子囊浓度的葡萄霜霉病病情预测模型研究。【方法】2016—2019年连续调查葡萄霜霉病田间病情,对空气中病菌孢子囊浓度和气象因素进行定期监测,经相关性分析和非线性回归分析,构建并检验葡萄霜霉病病情预测模型。【结果】葡萄霜霉病季节流行曲线通常表现为S形曲线,始发期为7月上旬至下旬,盛发期为7月下旬至8月下旬,衰退期为8月下旬至9月中下旬,降雨量对葡萄霜霉病始发时间和流行程度具有重要影响。经相关性分析,明确空气中孢子囊浓度主要与7 d平均相对湿度和7 d累积降雨量呈显著正相关(r>0.224,p<0.030;r>0.209,p<0.040),与日累积降雨量呈显著负相关(r>-0.233,p<0.025),确定上述3个气象因子是影响霜霉病菌孢子囊空气中飞散的主要气象因素。通过非线性回归分析,明确了葡萄霜霉病田间病情与累积孢子囊浓度的关系均为幂函数关系,其中病情指数与累积孢子囊浓度和一周前累积孢子囊浓度的拟合效果最佳。【结论】根据4 a田间小区试验结果,可利用累积孢子囊浓度预测葡萄霜霉病田间病情发生程度。

【Objective】Grape downy mildew is a typical airborne disease that can damage all green tissues on Vitis plants,including leaves,inflorescences,berries,tendrils and young canes.Sporangium is the important carrier of short distance transmission of the disease.The formation,maturation,germination and release of sporangium are affected by meteorological factors such as temperature,relative humidity,rainfall,illumination and wind speed.In order to clarify the effects of airborne sporangium concentration of Plasmopara viticola and meteorological factors(air temperature,relative humidity,rainfall and wind speed)on disease infection of grape downy mildew in Shenyang,a prediction model of grape downy mildew driven by airborne sporangium concentration of P.viticola was established to guide the effective control of the disease.【Methods】Shenyang,one of the production areas of table grapes in China,was chosen as the experimental base.Experiments were conducted during four growing seasons from 2016 to 2019.Four test plots were arranged from north to south,and the test cultivar was Centennial Seedless(Vitis vinifera L.),which was highly susceptible to grape downy mildew.Each experimental plot was 15 m long,and 5 m wide.Vine spacing was 0.5 m within rows and 0.6 m between rows.The plots were planted on April 30,2016;April 28,2017;May 5,2018 and April 29,2019.Each plot was irrigated and managed normally,and the cropping system was not treated with any fungicide in order to facilitate the onset of the disease epidemic.TRM-ZS1 meteorological ecological environment detector was installed in the orchard for regular recording meteorological data.The concentration of airborne sporangia of P.viticola was monitored daily with Burkard spore trap.The incidence and degree of grape downy mildew was investigated by using the five-point sampling method and 15 fixed grape seedlings were selected from each plot every seven days.Bivariate correlation method in SPSS 19.0 was used for correlation analysis,and Spearman correlation coefficient was used to obtain the correlation analysis results among disease index of grape downy mildew,airborne sporangium concentration of P.viticola and meteorological factors.Eight curve models were selected to fit the data of disease index and the accumulated sporangium concentration of P.viticola during 2016 to 2019.The coefficient of determination(R2),F value(F),significance probability(p)and estimated standard deviation(Std E)were taken as the criteria of model selection to select the best prediction model for grape downy mildew.【Results】The disease progress curve of grape downy mildew was usually sigmoid,the exponential phase was from early July to late July,the logistic phase was from late July to late August,and the decline phase was from late August to mid-late September.Rainfall had an important effect on occurrence and prevalence of grape downy mildew.The variation curve of airborne sporangium concentration of P.viticola in the field showed a wavy change,which increased with the disease index in general.The airborne sporangium concentration decreased gradually as the disease stopped growing.In 2016,the date of first sporangia trapping in the field was June 20,and the airborne sporangium concentration increased slowly before July 1,then increased sharply,and reached the peak of 75 sporangium per m3 on September 8.In 2017,the date of first sporangia trapping was June 26,the airborne sporangium concentration increased rapidly after July 11,and reached the maximum of 52 sporangium per m3 on August 22.The date of first sporangia trapping was June 29,2018,then the airborne sporangia concentration increased in a multi-peak curve,and reached the maximum of 57 sporangium per m3 on September 8.The date of first sporangia trapping in the field in 2019 was June 26,the airborne sporangium concentration fluctuated at a low level before July 12,and reached the peak of 51 sporangium per m3 on September 1.Correlation analysis showed that airborne sporangium concentration of P.viticola was significantly positively correlated with average relative humidity before 7 days(r>0.224,p<0.030)and accumulated rainfall before 7 days(r>0.209,p<0.040),but had a significant negative correlation with daily rainfall,indicating that the above three meteorological factors were the main meteorological factors affecting the airborne dispersion of P.viticola.There was no significant correlation between the sporangium concentration of P.viticola and the average daily air temperature,relative humidity and wind speed,indicating that the daily meteorological factors were not the key factors affecting the airborne dispersion of P.viticola.The relationship between disease index and the accumulated sporangium concentration was a power function by nonlinear regression analysis,and the best prediction model was based on the accumulated sporangium concentration before the day of disease measuring and the accumulated sporangium concentration before the current week of disease measuring.【Conclusion】Based on the analysis of 4-year plot experiment in the field,the accumulation of sporangium concentration of P.viticola can be used to predict disease progress of grape downy mildew in the field.