| Purpose: Pseudostellaria heterophylla is one of the authentic medicinal materials in Fujian Province.Its planting has serious continuous cropping obstacles.After many years of planting,Pseudostellaria heterophylla grows stunted,and its yield and quality are severely reduced.In this project,Capsicum annuum is introduced into the Pseudostellaria heterophylla planting system to study the effect of Capsicum annuum and Pseudostellaria heterophylla on the improvement of Pseudostellaria heterophylla continuous cropping obstacles from the perspective of changes in soil p H,autotoxic substances and microbial communities,in order to explore the practical possibility of Capsicum annuum and Pseudostellaria heterophylla crop rotation to solve the problem of continuous cropping obstacles of ginseng.Methods: 1.Take five-point sampling method and root shaking method to collect blank(K),continuous cropping Pseudostellaria heterophylla(LS),continuous cropping Capsicum annuum(LJ),Pseudostellaria heterophylla and Capsicum annuum crop rotation(LZ)Rhizosphere soil;use a p H meter to measure the p H value of the four groups of soils.2.Use70% methanol as the extraction solvent to extract allelopathic autotoxic substances in four groups of soil samples(K,LS,LJ,LZ),methanol and 0.1% acetic acid aqueous solution as the mobile phase gradient elution,obtain fingerprints,and perform integration processing,compare the number of chromatographic peaks and total peak areas of allelopathic autotoxins in various soil samples;alkaline extraction and acid precipitation method extracts phenolic acid allelopathy autotoxins in four groups of soil samples(K,LS,JS,SJ),ethyl acetate extraction,methanol and 1% acetic acid aqueous solution as the mobile phase for gradient elution,to obtain fingerprints,and select eight kinds of phenolic acids as standard products,compare the sample chromatograms,use the external standard one-point method to calculate the phenolic acids in each sample Substance content.3.Collect 14 samples of blank(K),continuous cropping Capsicum annuum(LJ),continuous cropping Pseudostellaria heterophylla(LS)rhizosphere soil to study the microbial diversity of rhizosphere soil.Extract the genomic DNA of the sample,select specific primers(bacterial16s RNA,fungal ITS1,archaea 16 s RNA,actinomycete 16 s RNA and nitrogen-fixing bacteria nif H gene)for PCR amplification,Miseq sequencing;biological information analysis of the measured sequence Statistics,calculation of diversity index,community diversity analysis using R language,etc.Results: 1.The pH value is sorted from low to high: LS,LZ,LJ,K.After planting Pseudostellaria heterophylla,the degree of soil acidification was the highest.After rotation of Pseudostellaria heterophylla and Capsicum annuum,the soil p H value increased significantly(P < 0.05).2.A large amount of allelochemicals was accumulated in the rhizosphere soil of Pseudostellaria heterophylla under long-term continuous cropping.After rotation with Capsicum annuum,the amount and content of allelochemicals decreased;After continuous cropping of Pseudostellaria heterophylla,the autotoxic contents of eight phenolic acids increased,and the contents of vanillic acid,syringic acid,vanillin,pcoumaric acid and p-ferulic acid increased significantly(P < 0.01);After rotation with Capsicum annuum,the content of phenolic acids in the soil showed a downward trend,and the contents of syringic acid,p-coumaric acid and ferulic acid decreased significantly(P <0.05).In general,the rotation of Capsicum annuum and Pseudostellaria heterophylla had a certain effect on reducing the content of phenolic acids in the soil of Pseudostellaria heterophylla.3.In terms of bacteria: compared with LS soil,the number and diversity of bacterial microbial community in LJ soil are more and higher,which is conducive to the stability of micro ecological environment.Compared with the three groups of treatment soil,the proportion of most pathogenic bacteria positively related to plant disease is higher in LS,and the proportion of most bacteria beneficial to plant growth is higher in LJ soil;In terms of archaea,thaumarchaeota had the highest proportion in LS soil and Euryarchaeota had the highest proportion in LJ soil.The complementary beneficial Archaea provided the possibility for the rotation of Capsicum annuum and Pseudostellaria heterophylla;In terms of fungi: LS soil has a large number of fungi with high diversity.A variety of harmful fungi causing root rot were detected in LS soil,and they were the dominant flora.Chaetomium and Mortierella were detected in LJ soil;Actinomycetes: a variety of potential beneficial bacteria were detected in K soil and LJ soil,which played a certain role in environmental remediation and nitrogen cycle;Nif H gene of nitrogen fixing bacteria: there are 18 nif H gene microbial genera with significant differences among the three groups,of which 13 species are the dominant flora in the soil after planting pepper.The increase of nitrogen fixing dominant flora in the soil after planting pepper plays an important role in promoting the interaction of beneficial bacteria,antagonizing harmful bacteria and harmful substances.Conclusion: 1.Experiments have verified that planting Pseudostellaria heterophylla will cause soil acidification to a certain extent.The rotation of Capsicum annuum and Pseudostellaria heterophylla can significantly alleviate the soil acidification caused by planting Pseudostellaria heterophylla,and improve the continuous cropping obstacle of Pseudostellaria heterophylla from the aspect of adjusting soil p H.2.Soil acidification is closely related to phenolic acids.The p H of the soil decreases with the increase of phenolic acids,roughly inversely proportional to it.It is speculated that the accumulation of phenolic acids in the soil is the main cause of soil acidification of Pseudostellaria heterophylla The crop rotation of Capsicum annuum and Pseudostellaria heterophylla has a certain effect to reduce the content of phenolic acids that plays a significant role in Pseudostellaria heterophylla continuous cropping disorder.3.There are great differences in rhizosphere soil microbial community structure between Capsicum annuum and Pseudostellaria heterophylla.To guide the rotation of Capsicum annuum and Pseudostellaria heterophylla based on community differences may play a role in alleviating the continuous cropping obstacle of Pseudostellaria heterophylla in terms of beneficial bacteria complementation and pathogen antagonism. |
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