| Plasmodiophora brassicae is a serious soil-borne disease of cruciferous plants.When the environment is favorable for the occurrence of club root,the root of the plant will swell and the absorption of water and nutrients will be hindered,resulting in the decline of the quality and yield of the crop,or even all of the crop will be lost.The main control measure of the disease is still chemical control.In terms of application,excessive application of drugs and low utilization rate of resources greatly damage the structure of soil microecological community,lead to deterioration of soil properties,and create an environment conducive to the occurrence of club root,thus aggravating the occurrence and harm of club root.Temperature,humidity,pH value,light,trace elements and soil microorganism in soil environment have important influence on the occurrence and prevalence of club root.According to the pathogenesis and biological characteristics of Plasmodiophora brassicae,the susceptible host"precocious no.5"Chinese cabbage and rape varieties were used as the experimental host,and four agents including bacillus subtilis(XF-1),new lime nitrogen,quicklime and soil conditioner were used for the control experiment of club root,and the changes of soil pH were detected by soil pH meter,the changes of soil mineral elements were detected by atomic absorption spectrophotometry,the changes of soil microbial species and quantity were detected by megagenomic 16S rDNA and 18S rDNA sequencing.The main research results are as follows:1.Effects of different agents on dormancy spore germination of Plasmodiophora brassicaeThe effects of four agents on the germination of dormant spores in Plasmodiophora brassicae were studied by using the method of dormant spore germination.The results showed that the inhibition rates of four agents on dormant spores in rhizoma cystis were 75.05%of quicklime,71.51%of soil conditioner,67.67%of lime nitrogen,and 61.19%of bacillus subtilis(XF-1).2.Indoor pot experiment was conducted to screen the appropriate concentration of agentsThe control effect of four kinds of medicaments on club root was tested by potted experiment in laboratory,and the suitable concentration was selected for field control experiment.The bacillus subtilis(XF-1)with the best control effect of the four agents was 91.44%,soil conditioner 88.57%,quicklime88.57%,lime nitrogen 68.58%.Bacillus subtilis(XF-1)group A2 was diluted at a concentration of 600times,group B2 was treated at a concentration of 450g/basin,group C4 was treated at a concentration of 900g/basin,and group D1 was treated at a concentration of 250g/basin.3.Field chemical experiment3.1Xingluo village,tangchang townBacillus subtilis(XF-1)had the lowest incidence,and the control effect was up to 81.66%,which was the dominant treatment.The control effects of the other three agents were:lime nitrogen 72.48%>soil conditioner 58.41%>quicklime 56.67%.The investigation of fresh weight of Chinese cabbage after field harvest showed that the fresh weight of Chinese cabbage was 1286.35Kg/667m~2,which was a serious disease in the control area.Compared with the fresh weight of Chinese cabbage treated with medicament,the fresh weight of Chinese cabbage treated with medicament obviously grew well and the yield was high.The fresh weight of Chinese cabbage treated with soil conditioner was 2802.36Kg/667m~2,2886.26Kg/667m~2,2770.50Kg/667m~2 of lime nitrogen,which was the dominant treatment,and bacillus subtiliflora(XF-1)3185.89 Kg/667m~2,which was the most dominant treatment.3.2 Ruihong village,nanquan town,shifang cityThe incidence of blank control group was 93.20%,the incidence of bacillus subtilis(XF-1)treatment was 60.00%,and the control effect reached 81.51%.The weight of rapeseed treated with chemical agents reached 2,651.33 Kg/667m~2,the taproot was very strong,thick and long,the lateral root was luxuriant,the diameter of rapeseed was large,and the leaves were green and many.The weight of rape in the blank control area was 391.86Kg/667m~2,which was generally smaller than that of rapeseed treated with chemical agents.The main roots were short and thin,and even seriously decayed in the soil.The number of lateral roots was very small,and the leaves turned yellow.4.Determination of soil physical and chemical properties4.1 Change of pH in laboratory experimentThe pH value of the soil before application was 6.0,which was acidic soil and conducive to the occurrence of club root.The pH value of soil treated with quicklime was 7.5 at the highest after treated with 2 days.The pH values of soil conditioner and new lime nitrogen were 6.7 and 6.5respectively.Again,bacillus subtilis xf-1 with a pH of 6.3.Quicklime,lime nitrogen and soil conditioner can adjust the soil environment to alkalinity,which will result in unfavorable conditions for the occurrence of club root.4.2 Change of pH value in the field experiment in xingluo village,tangchang town,Pidou area.The pH value of the soil before application was 6.3,which was slightly acidic and conducive to the occurrence of root swelling disease.After treatment with chemicals,the pH value increased to 6.6 after treatment with soil conditioner,6.5 after treatment with bacillus subtilis(XF-1),7.0 after treatment with quicklime,and 6.7 after treatment with lime nitrogen.4.3 pH change of field experiment in ruihong village,nanquan town,shifang cityThe pH value of the soil before application was 5.83,which was acidic soil and extremely conducive to the occurrence of club root.The pH value of soil treated with bacillus subtilis(XF-1)was adjusted to6.42.4.4 changes of soil elementsCompared with the blank control group,the total magnesium content of quicklime,lime nitrogen,XF-1 and soil conditioner increased after application,and the difference of soil conditioner was the most significant.The total calcium content increased after applying soil conditioner,XF-1,lime nitrogen and quicklime,and the difference of soil conditioner was the most significant.Compared with the blank control group,the total phosphorus content of quicklime,XF-1 and soil conditioner decreased and the content of lime nitrogen increased,but the difference was not significant.5.Detection of soil microbial species and quantity in tangchang town after field applicationThe changes of soil microbial species and number were detected by macromegenomic 16S rDNA and 18S rDNA sequencing.Compared with the blank control group,the number of bacteria and fungi increased significantly after administration.According to the Alpha diversity index,soil species diversity was the highest among bacteria treated with lime nitrogen and bacillus subtilis(XF-1).The diversity of soil species was the highest among fungi treated with soil conditioner.The highest proportion of Proteobacteria detected at the level of soil samples was Proteobacteria,which was the dominant bacterial group,mainly composed of Rhizobiales and Sphingomonadales.At the level of bacterial genera,the difference of detected population was not obvious,but the proportion was different.As bacillus subtilis(XF-1)is a biocontrol bacterium,it has a direct effect on rhizome swelling disease,and the regulation effect of the obvious increase in the number of bacteria and fungi after the application of other agents is also the regulation mechanism of soil microecology. |
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