Relationship Between Environment And Cucumber Downy Mildew(Pseudoperonospora Cubensis) Infection?Latent Stage

Cucumber downy mildew is one of main diseases affecting cucumber yield.In the process of germ infection,it absorbs nutrition of the host,destroys internal tissue structure and then establishes a relationship with host,reaching incubation stage before the disease.In the incubation stage pathogens and hosts co-exist.Temperature and dew duration mainly affect whether the disease can develop.Therefore,incubation stage plays an important role in the process of cucumber downy mildew infection.In order to determine the downy mildew incubation period in cucumber(Cucumis sativus)‘Changchun honey thorn',we observed the changes of internal leaf tissue by X-ray microscopy imaging technique,stomatal conductance and leaf temperature differences.Different temperatures and dew duration combination,reach incubation stage time varies.To establish an early warning system to control downy mildew.The results show that:After infection of downy mildew for 68-74 h,stomatal conductance and leaf temperature were significantly increased compare with the uninoculated side under the condition of 23?,100% humidity,8h dew duration,which determined the incubation period.Under the X-ray microscope,the hyphae infected 75% leaf thickness(60/80 layer)which caused a decrease in pore structure at 68-70 h,leaves entered the incubation period.Through the X-ray microscopy,not only could we observe the blade as a whole,but also the segmental internal structure,from which we can accurately locate the infected period,infected position and incubation period.The study provided theoretical basis for the research of physiological changes of leaves infected by pathogens.When humidity was 100%,the temperature significantly affected whether the inoculated leaves entered the latent period,and irrelevant condensation duration.The lowest temperature of the inoculated leaves entering the latent period is 14?,5h dew condensation time.Low of 12?5h and high temperature continuous 3d can effectively inhibit leaf reaching the latent period.Low temperature and high temperature both can prevent downy mildew occur.But at low temperature the sporangium did not germinate,cucumber leaf could not enter the latent stage.Continuous high temperature inoculation leaf temperature compared with uninfected leaves,which is low-high-low phenomenon.Although the leaves enter the incubation period,high temperature environment 80-84 h is inhibited leaves enter to latent period.It can reduce the occurrence of downy mildew and has certain practical value in production.Based on the different temperature and dew duration influence downy mildew incubation stage,we collected environmental data was input into the compiled program to establish a cucumber downy mildew warning system.When greenhouse environment input into system,its can automatically determine whether the cucumber downy mildew is likely to occur.If the warning standard is reached,user will be reminded to ventilate or heat up the shed to reduce cucumber downy mildew incidence.The cucumber downy mildew early warning system is not only simple,easy to operate,but also highly real-time.In production its can effectively reduce the occurrence of cucumber downy mildew.