Study On The Mechanism Of DSE Fungi Promoting Phosphorus Absorption In Blueberr

In this study,‘Laigexi’ blueberry(Vaccinium corymbosum L.),DSE(Dark septate endophytes,DSE)Phialocephala fortinii as materials,to explore the phosphorus solubilization effect of DSE on 7 kinds of insoluble phosphates and the mechanism of phosphorus solubilization,through pot experiment of inoculating blueberry with DSE under different phosphorus levels,the influence mechanism of DSE promoting phosphorus absorption in blueberry was revealed from physiological and molecular aspects..The main research achievements are as follows:1)DSE has a certain solubility to tricalcium phosphate,iron phosphate,aluminum phosphate,zinc phosphate,mineral phosphate,lecithin,calcium phytate,which are seven kinds of insoluble phosphate.The increment of available phosphorus content was in order as follows: calcium phytate > phosphate powder > aluminum phosphate >tricalcium phosphate > zinc phosphate > lecithin > iron phosphate.Among the five inorganic phosphates,the dissolution effect of phosphate powder is the best,and among the two organophosphates,the dissolution effect of calcium phytate is better.DSE dissolves insoluble phosphatases by producing mycelia,secreting extracellular phosphatases,producing organic acids(mainly lactic acid,succinic acid,malic acid,as well as characteristic DL-3-phenyllactic acid,3-hydroxy-3-methylglutamic acid,phenylpyruvate)and lowering the pH of the fermentation fluid synergies to dissolve insoluble phosphates and increase the soluble phosphorus content in the environment.2)After inoculation with DSE,the growth and development of blueberry seedlings were promoted to different degrees.At the medium P level,the mycorrhizal infection rate,mycorrhizal contribution rate and mycorrhizal phosphorus uptake rate were the highest.The growth promotion effect was medium P > high P > low P,and the effect was better in organophosphorus than in inorganic P.The phosphorus content of blueberry plants was significantly increased after inoculation with DSE.Correlation analysis showed that,on the one hand,DSE could enhance the root vitality of blueberry and change the root morphology of blueberry by expanding the extension range of root(root length increased after inoculation)and increasing the absorption area(root surface area,root tip number,root bifurcation number and root volume),thus promoting blueberry to absorb more phosphorus.On the other hand,in addition to the organic acids and phosphatases secreted by DSE itself,It can also promote blueberry to secrete more organic acids(lactic acid,(R)-3-hydroxybutyric acid,3-hydroxyphenylacetic acid,L-pyroglutamic acid,succinic acid,o-hydroxyphenylacetic acid,indole-3-acetic acid,etc.),phosphatase(acid phosphatase,neutral phosphatase,phytase)and other root exudates to activate the insoluble phosphorus source in the substrate and reduce the pH value of the substrate,increased available phosphorus content.3)High-throughput sequencing of 16S r DNA and ITS amplicon was performed on rhizosphere microorganisms of blueberry.It was found that the bacteria in rhizosphere soil after inoculation with DSE were Pseudomonas,Bacillus,Bdellovibrio,Ensifer and Aquicella.The fungi Phialocephala,Echinospora and Sporospora increased significantly.Correlation analysis of environmental factors found that these fungi were significantly negatively correlated with soil total phosphorus and pH,and significantly positively correlated with soil acid phosphatase,neutral phosphatase,alkaline phosphatase,phytase and available phosphorus,which promoted each other.Pseudomonas and Bacillus are common phosphorus solubilizing bacteria.DSE inoculation caused changes in rhizosphere microbial population structure,and significantly increased the proportion of phosphorus soluble microbial population such as Pseudomonas and Bacillus.4)Transcriptome sequencing analysis of the treatments with the largest contribution rate of mycorrhizal phosphorus uptake showed that the number of upregulated differential genes was 5.95 times that of down-regulated genes after DSE inoculation.KEGG enrichment analysis showed that,Phenylpropyl anabolic pathway,metabolic pathway,secondary metabolite synthesis pathway,various plant secondary metabolites biosynthesis pathway,brassinolide biosynthesis pathway,amino sugar and nucleotide sugar metabolism,glutathione metabolism,pentose and glucuronic acid mutual conversion pathway,unsaturated fatty acid biosynthesis pathway,MAPK signaling pathway-plant and other related pathways are poor Heterosignificant enrichment;Through GO enrichment analysis,it was found that the biological processes were mainly enriched in metabolic processes,monomer metabolic processes and cellular processes.Cell group is divided into membrane;Molecular functions are catalytic activity and binding.DSE promotes the gene expression of Vc:Pht1;4(Vadar＿017380)in the phosphate transporter Pht1 family significantly up-regulated,4.26 times that of CK treatment(194.85/45.76).Vc:Pht1;4(Vadar＿017380)is a mycorrhizal up-regulated phosphate transporter.In this study,mycorrhizal technology is associated with phosphorus enrichment in blueberry,and the mechanism of phosphorus absorption regulation by DSE in blueberry is preliminarily clarified.It will help to understand the relationship between DSE and host plants,and provide theoretical basis for increasing soil soluble phosphorus content by using DSE,promoting effective utilization of phosphorus by plants,and accelerating blueberry mycorrhizal seedling cultivation.It has great economic and social significance in improving crop yield and protecting environment.