| Pinellia ternata is a plant of Pinellia genus in Araceae,and its dry tubers are used as medicine.It is a traditional Chinese medicine.Pinellia ternata（referred as P.ternate hereafter）has serious continuous cropping obstacles,resulting in low yield,poor quality,and weak plant growth,while systematic research on it remains rare.In addition,it is reported that allelopathy is one of the main reasons for continuous cropping obstacles,and the previous research of our research group found that there is allelopathic substance 4-methyl-2,6-di-tert-butylphenol in the decomposition solution of P.ternate.In order to systematically understand the performance of continuous cropping obstacles of P.ternate and explore the effects of continuous cropping on soil microorganisms and chemical components.At the same time,the gene expression of P.ternate root treated with 4-methyl-2,6-di-tert-butylphenol was explored.This experiment mainly studiedthe effects of continuous cropping on the growth,physiology,and quality of P.ternate,analyzed the changes of soil microbial community and soil allelochemicals of P.ternate under continuous cropping,and the effects of allelochemicals 4-methyl-2,6-di-tert-butylphenol on gene expression in roots of P.ternate were also studied.It provides a theoretical basis for further study on the continuous cropping obstacle of P.ternate.The main results are as follows:1.Effects of continuous cropping on growth,physiology and quality of P.ternate.The seedling emergence rate,leaf area,plant height,stem diameter and total yield of continuous cropping P.ternate were lower or significantly lower than those without continuous cropping.With the increase in continuous cropping years,the emergence rate,leaf area,plant height and stem diameter decreased,the inverted seedling rate increased,and the total yield decreased.That is It indicated that,continuous cropping inhibited the emergence,plant growth and yield of P.ternate,and the longer the continuous cropping years,the more serious the inhibition.Continuous cropping could reduce the net photosynthetic rate,relative chlorophyll content and the activities of peroxidase,superoxide dismutase and catalase.The soluble protein of P.ternate under continuous cropping for 1-5 years was 1.01～1.69 times higher than that of without continuous cropping,and the soluble sugar content was 1.81～2.80 times higher than that of without continuous cropping.The contents of malondialdehyde and proline in continuous cropping increased by 9.49%～32.43%and 13.86%～54.17%respectively.The contents of soluble protein,soluble sugar,malondialdehyde and proline of P.ternate in continuous cropping for 1-5 years show an increasing trend,twhich manifests that continuous cropping will cause physiological damage to P.ternate and make it in a state of adversity.The contents of water,total ash,extract and succinic acid in P.ternate under continuous cropping were lower than those in non-continuous cropping,and showed a downward trend after continuous cropping for 1-5 years.It indicates that continuous cropping will reduce the quality of P.ternate,and the longer the continuous cropping period,the worse the quality.2.Effects of continuous cropping on soil microbial community of P.ternate.The species diversity and richness of soil fungi and bacteria decreased gradually with the increase in continuous cropping years.As continuous cropping years become longer,at the phylum level,the relative abundances of Ascomycota and Basidiomycota first increased and then decreased.Mortierellomycota decreased first and then increased.The relative abundances of Actinobacteriota and Acidobacteriota in bacteria first decreased and then increased.The relative abundances of Proteobacteria and Chloroflexi decreased gradually.At the genus level,the number of Solicoccozyma and Fusarium increased,and the number of Morphella decreased first and then increased.norank＿f＿＿norank＿o＿＿Vicinamibacterales of bacteria decreased,norank＿f＿＿Vicinamibacteraceae and norank＿f＿＿norank＿o＿＿Gaiellales decreased first and then increased.Continuous cropping reduced the relative abundances of beneficial bacteria such as Proteobacteria,Chloroflexi and Morphella,and increased the relative abundance of pathogens such as Fusarium.With the increase in continuous cropping years,the p H value and water content of soil gradually decreased,the contents of available nitrogen and available phosphorus first decreased and then increased,and the available potassium showed a decreasing trend.The fertility of non-continuous cropping soil was significantly higher than that of continuous cropping soil.Correlation analysis showed that the main influencing factors of soil fungal and bacterial communities of P.ternate under continuous cropping were soil p H value,soil moisture,available potassium and available nitrogen.3.Changes of soil allelochemicals of P.ternate under different continuous cropping years.53,53,63,59,58 and 60 compounds were detected in the soil of P.ternate under continuous cropping for 0-5 years.The types of compounds in continuous cropping soil were more than those in non-continuous cropping soil.There are 20 same compounds in each continuous cropping soil,among which dibutyl phthalate,vanillin,benzoic acid have allelopathic effect on P.ternate,showing the phenomenon of low promotion and high inhibition,and all showing the promoting effect at the concentration of 0.1 mg.L-1.The comprehensive allelopathic effect index revealed that dibutyl phthalate and vanillin could inhibit the the germination rate and bud growth of P.ternate at the concentration of 1 mg.L-1,and benzoic acid had the inhibitory effect at the concentration of 20 mg.L-1.With the increase of concentration,the inhibitory effect increased.Dibutyl phthalate had the strongest inhibitory effect on the germination of P.ternate,followed by vanillin and benzoic acid.4.Effects of allelochemicals 4-methyl-2,6-di-tert-butylphenol on gene expression in roots of P.ternate.The results showed that compared with the control group,when the concentration of 4-methyl-2,6-di-tert-butylphenol was 400 mg.L-1,there were 16 716 differentially expressed genes in the roots of P.ternate,of which 7669 genes were up-regulated and 9 047 genes were down-regulated.When the concentration was 100 mg.L-1,there were 17 142 differentially expressed genes,of which 7 490 genes were up-regulated and 9 652 genes were down-regulated.When the concentration was 0.1 mg.L-1,there were 2 234 differentially expressed genes,of which 1 251 genes were up-regulated and 983 genes were down-regulated.The transcription factor corresponding to differentially expressed genes are MYB＿superfamily、AP2/ERF、NAC and WRKY families,which plays a role in the regulation of plant tolerance to stress.There are also b HLH,C3H,and b ZIP families related to plant stress resistance.GO annotation analysis exhibited that differentially expressed genes（DEGs）were mainly in multicellular organismal,biological regulation,cellular process,protein-containing complex,cell,organelle,cell part,transcriptional regulator activity,binding,catalytic activity,and molecular transducer activity.In GO function enrichment,DEGs are mainly enriched in ribonuclease activity,extracellular region,cell wall organization or biogenesis.KEGG annotation analysis showed that the DEGs were mainly annotated in carbohydrate metabolism,lipid metabolism,amino acid metabolism,energy metabolism,and biosynthesis of other secondary metabolites.In KEGG pathway,the DEGs are mainly enriched in phenylpropane biosynthesis,pentose and glucuronate interconversions,ribosome,flavonoid biosynthesis and oxidative phosphorylation.Comprehensive GO and KEGG functional annotation and enrichment analysis showed that the roots of Pinellia ternata treated with 4-methyl-2,6-di-tert-butylphenol were significantly affected in the above process. |
