Molecular Detection And Dynamic Analysis Of Temporal-spatial Distribution On Plasmodiophora Brassicae

Clubroot is a soil-borne disease caused by Plasmodiophora brassicae,which seriously occurred and made significant losses in production areas of cruciferae crop worldwide.This pathogen can survive in soil for a long time,which leads to limiting disease management that is unable to effectively control the occurrence and spread of clubroot.In this study,a method of early diagnosis and a quantitative detection system for P.brassicae were established to monitor the temporal and spatial distritbion in the field.This study will provide theoretical referen and technical support for the occurance of P.brassicae and the epidemic of clubroot.The main results are listed as follows:1.An early diagnosis method of clubroot was established based on regular PCR technology.This method can specifically detect the DNA of P.brassicae,but has no amplification products for representative fungi,bacteria,nematode and endophytes of host plants.Sensitivity assay was indicated that the lowest concentration is 1×103 ng/μL for P.brassicae,1×103 spores/g for the contaminated soil,and 1×105 spores/g for the contaminated seeds.In addition,this assay can also apply for diagnosis of several cruciferous crops(including diseased rapeseed,cabbage,stem mustard,cabbage,radish).This method can also used for diagnosic assay of proposed contaminated roots and soils from the oilseed rape field within the growth stages.2.A quantitative detection system for P.brassicae was established uesing qPCR method.This assay can quantitatively detect the spores,soil,seed and planet tissues contaminated by P.brassicae.The minimum levels of sensitivity were analyzed with the baseline concentration of 10 spores for thies pathogen,1×103 spores/g for the soil,1×103 spores/g for the plant tissues(e.g.,oilseed rape,cabbage and stem mustard)and 1×103 spores/g for the seeds.Particuarlly,the standard curves corresponding to the different types of samples were parallel while the limited varation was accessed at the concentation of 1×105 spores that was positively correlated to the disease index.Such study provides a accessment for the possibility of clubroot occurance and epidemic.3.Temporal and spatial dynamics of P.brassicae population in the field was analyzed by the estabilised diagnosis and detection system.On the temortal dynamic,the population changed to initially decline and then increase within a growth season.On the spacial dynamic with vertical distribution,P.brassicae mainly survived in 0-50 cm in soil depth,in which the resting spores were concentrated at 20-40 cm at 4 weeks after seeding and focused at 10-20 cm at 8 weeks after seeding.Meanwhile,on the spacial dynamic with horizontal distribution,the spore concentration was correlated with disease severity in the field.A field area with the abundant resting spores(i.e.,a hot spot)was identified while a new hot spot of field was generated within a growth season..This study establishes an early diagnosis method of clubroot and a quantitative detection system for P.brassicae,which premilinarily used for accurate detect and monitor the dynamic of clubroot in the field.This work will provide an theoretical reference and technological approach for the earily warning and epidemic furcating of clubroot.