Effects Of Different Preceding Crops On Clubroot Disease Of Chinese Cabbage And Soil Microorganisms

In recent years,the ecological environment of vegetable fields has been deteriorating as the long-term unscientific management,which has lead to seriously soil-borne diseases.The clubroot disease was caused by the soil-borne pathogen plasmodiophora brassicae,which is one of the main factors restricting the production of Chinese cabbage.The progress of disease resistance breeding is slowly due to many small physiological species and the application of a large number of chemical agents threatened human health and soil ecological environment.Therefore,h ow to improve the ecological environment of vegetable fields soil,reduce the incidence of Chinese cabbage diseases,and promote the sustainable production of Chinese cabbage has become an urgent problem to be solved.A suitable preceding crop can promote the growth of the succeeding crops and reduce the incidence of soil-borne diseases.At present,there is less studies on the preceding crop to facilitate the growth of Chinese cabbage.In this study,Chinese cabbage(Brassica rapa ssp.Pekinensis)was used as a research object,and the field experiments was conducted to test the effects on the growth of Chinese cabbage,soil physical and chemical properties and soil microorganisms with the preceding crops of soybean(Glycine max(Linn.)Merr.),potato onions(Allium cepa var.agrogarum L.)and wheat(Triticum aestivum L.)comparing with the local preceding crop garlic(Allium sativum L)..The aim at this study is to screen for the suitable preceding crops for the growth of Chinese cabbage and the control of Chinese cabbage clubroot disease,and providing a certain theoretical basis of its production and a reference type of model for the ecological prevention.The main results were as follows:1.Different preceding crops have different effects on the growth of Chinese cabbage.In detail,both potato onion and wheat as a preceding crop promoted the growth of Chinese cabbage and significantly increased the yield of Chinese cabbage during the continuous planting for two years.And they increased the shoot yields of Chinese cabbage by 37.89%and 30.53%at the first year of planting,the shoot yields were increased by 58.33%and 36.67%at the second year of planting.2.Compared with the control,both potato onion and wheat as a preceding crop significantly reduced the clubroot disease index in each sampling period,and the control effects of the three preceding crops on the clubroot disease was potato onion>wheat>soybean,which consistent performance for two continuous years.3.Compared with the control,the three preceding crops reduced the soil bulk density,increased the total soil porosity and significantly reduced the soil EC value after planting,and the soil catalase activity was significantly increased after planting potato onion.During the Chinese cabbage planting period,the three preceding crops significantly reduced the EC value of the soil.After the Chinese cabbage was sown for 40 days,these three preceding crop significantly reduced the soil available potassium level and soil invertase activity.The results of the experiment were almost identical for two continous years.4.Compared with the control,both the three preceding crops reduced the population of resting spores of plasmodiophora brassicae in the soil.The population of resting spores of plasmodiophora brassicae in each gram of soil with a preceding crop of soybean,potato onion,or wheat was respectively decreased 3.734×10~4,3.560×10~4,3.139×10~4 for the first year,and 4.749×10~4,5.003×10~4,5.542×10~4 for the second year,which reached significant difference.comparing with the control.5.Miseq sequencing results showed that the three preceding crops significantly increased the abundance and diversity of bacteria and decreased the fungus abundance and diversity,significantly increased the relative abundance of Chloroflexi and significantly reduced the relative abundance of Proteobacteria and Firmicutes while prededing crops were harvested.After the Chinese cabbage was planted for 20d,the three preceding crops both significantly increased the relative abundance of Ascomycota and significantly reduced the relative abundance of the Basidiomycota.Soil p H and EC values were the main environmental factors affecting soil bacterial and fungal communitie s when preceding crops were harvested;when Chinese cabbage was sown for 20d,s oil p H,EC value and soil available phosphorus level were the main environmental factors to affect soil bacterial structure,soil EC value and soil available phosphorus level were the main environmental factors to affect soil fungal structure.6.Correlation analysis between soil microorganisms and resting spores revealed that bacteria OTU 9(Lysobacter)and OTU 39(Gemmatimonadaceae)were significantly negatively correlated with the quantity of resting spores.In summary,the three preceding crops can change the structure of soil microbes,alleviated the clubroot disease of Chinese cabbage,and the effects of promoting growth and suppressing disease was followed as:potato onion>wheat>soybean...