Effects Of Soil Factors On Clubroot Disease In Main Rapeseed Production Areas

Clubroot caused by Plasmodiophora brassicae Woronin is one of the most serious soil-borne diseases on crucifers. In practice, the major measure used to control the clubroot is root irrigation with fungicides. Though chemical fungicides are effective, the developments of integrated control measures are needed for development of sustainable agriculture with little environmental pollution. Utilization of suppressive soil is an important part of integrated control of soil-borne diseases. In this study, twelve different soil samples collected from seven provinces were tested for clubroot incidences in the inoculation experiments using the cabbage variety Beijing new III as the host plant. The purposes are to provide a theoretical basis for sustainable disease control and effectively prevent diffusion of clubroot disease. Effects of microbes on clubroot were determined by sterilization of soils. Relationship of physical and chemical properties of soils and clubroot incidence were analysized by path analysis using the statistical analysis software SPSS. The main results are listed below:1. The clubroot incidences between different origin soils differed significantly. The disease incidences were up to63.6%and51.7%respectively in the samples collected from Suizhou of Hubei and Chaohu of Anhui with the resting spore concentration of102spores/g of soil. However, disease incidences in soils from Wuchang and Yangluo of Hubei, Xining and Huzhu of Qinghai were as low as1.7%and3.3%respectively when the inoculation density was as high as105spores/g of soil; disease incidences in soils from Minle of Gansu were only3.3%with the concentration of106spores/g of soil. The results suggested that clubroot risks were high in the Suizhou of Hubei and Chaohu of Anhui, while the clubrot risks were low in Wuchang and Yangluo of Hubei, Xining and Huzhu of Qinghai, and Minle of Gansu.2. Clubroot incidences are positively related with the spore concentration in soils. The incidence of clubroot are increased with the increase of resting spore concentration.3. The soil microorganisms affect the occurrence of clubroot. The microorganisms in two soil samples collected from Wuhan showed significant inhibition on the incidences of clubroot. The incidence of clubroot in pre-sterilization soils were0.0%,0.0%and0.0%,3.3%, when the inoculation of Plasmodiophora brassicae density is104spores/g of soils and105spores/g of soils, the incidence of clubroot increased to21.7%,5.0%and46.7%,51.7%in sterilization soils.4. The pH, available Ca, total P, total K and cation exchange capacity (CEC) were found to be negatively related with the clubroot incidence.