Induced Systemic Resistance And Its Mechanisms By Endophytic Burkholderia Pyrrocinia JK-SH007 Volatile Organic Compounds In Poplar

Poplar canker disease is a kind of serious poplar branch disease.It is difficult for control that there are many kinds of pathogens and various symptoms.In this study,a strain of,a highly effective endophytic control strain Burkholderia pyrrocinia JK-SH007 isolated from the early stage of the study,which can induce poplar risistance poplar canker,focusing on studing VOCs produced by B.pyrrocinia JK-SH007 induced resistance to poplars,and their antibacterial effects and molecular mechanism on three poplar canker disease pathogens(Cytospora chrysosperma,Phomopsis sp.,Fusicoccum aesculi).The main results are as follows:1.The antibacterial effect of VOCs produced by strain JK-SH007 on the three poplar cankers pathogens was detected with two-sealed-base-plates method,and the effect of the VOCs on the pathogenic bacteria mycelia morphology was observed under the microscope.After incubation for 4 days at 28°C,the VOCs produced by strain JK-SH007 the antibacterial rates of Cytospora chrysosperma,Phomopsis sp.and Fusicoccum aesculi was 45.51%,21.69%,43.82%,respectively.The mycelium of three kinds of pathogens were selected and observed,the control dish grew vigorously,smooth and slender,and the mycelium was separated clearly.After the treatment of VOCs produced by strain JK-SH007,the mycelium of the Cytospora chrysosperma became thick,dry,distortion and flexibility decrease.The mycelium of the Phomopsis sp.became thicker,and the internal protoplasm agglomerates.The mycelium of Fusicoccum aesculi became thick and enlarges.Strain JK-SH007 liquid culture of 200?L was added to a small beaker and co-cultured with poplar seedings.,the changes of PPO,POD,?-1,3 glucanase,PAL,SOD defense enzyme activities and the malondialdehyde content and the total phenols content were detected at different periods.The results showed that the defense enzyme activity of the treatment group was higher than the controlgroup.The ?-1,3 glucanase activity of the treatment group reached the highest value on the third day,and the other four defense enzyme activities reached the highest value on the 9th day after treatment.The malondialdehyde content of the treatment group was lower than the control group.The total phenol content of the treatment group was higher than the control group began to the 9th day.There were 13 kinds of main VOCs were identified by SPME-GC-MS method in the strain JK-SH007 fermentation broth,dimethyl disulfide,methyl iminobenzoate,dimethylthiomethane,phenyl acetone,dimethyl trisulfide,3-propoxy-1-propene,aromatic phenyl acetone,1-methy-2-methylthiomethyl disufide,4-methyl-2,3-pentanediol,2-methyvaleraldehyde,benzothiazole,6-methyl-3-heptanone,acephenone,respectively,and other VOCs account for very few components.Dimethyl disulfide was accounted for the largest proportion.2.Different volumes of dimethyl disulfide,benzothiazole,dimethylthiomethane,and phenylacetone standards were added to 5mL beakers,and placed in culture flasks of inoculated with poplar seedlings,respectively.The activity of PPO,POD,?-1,3 glucanase,PAL,SOD and the malondialdehyde content and total phenol content were measured at different periods.The results showed that dimethyl disulfide had the greatest effect on various defense enzyme activities,malondialdehyde content and total phenol content,the best effect was added to 7.5?L for 9days.The results showed that dimethyl disulfide treatment had the greatest effect on various defense enzyme activities and malondialdehyde and total phenol content.Among them,7.5?L treatment was the best for 9 days.Others three kinds of VOCs had certain effect but not obvious.3.Different volumes of VOCs standards(dimethyl disulfide,dimethyl thiomethane,dimethyl trisulfide,phenyl acetone,benzothiazole,2-methylvaleraldehyde)were tested on the growth inhibitory effects of three poplar canker pathogens(Cytospora chrysosperma,Phomopsis sp.,Fusicoccum aesculi)by the method of special divided plastic petir dishe.With the increase of the added volume,the inhibitory effect of VOCs on the three poplar cankers pathogens was also gradually enhanced.When the amount of VOCs standards was 80?L in the special divided plastic petir dishe,the growth inhibition rates of dimethyl disulfide on the Phomopsis sp.,Cytospora chrysosperma,Fusicoccum aesculi was 96.05%,94.36%,91.08% respectively,the growth inhibition rates of dimethyl thiomethane on the Cytospora chrysosperma,Phomopsis sp.,Fusicoccum aesculi was 96.62%,92.62%,89.93% respectively,the growth inhibition rates of dimethyl trisulfide on the Fusicoccum aesculi,Cytospora chrysosperma,Phomopsis sp.was97.21%,96.99%,95.79% respectively,the growth inhibition rates of phenyl acetone on the Cytospora chrysosperma,Fusicoccum aesculi,Phomopsis sp.was 78.00%,74.60%,60.17%respectively,the growth inhibition rates of benzothiazole on the Cytospora chrysosperma,Fusicoccum aesculi,Phomopsis sp.was 73.36%,71.84%,56.10%,respectively,the growth inhibition rates of 2-methylvaleraldehyde on the Cytospora chrysosperma,Fusicoccum aesculi,Phomopsis sp.was 96.60%,96.53%,79.73%,respectively.The mycelia of pathogens treated with VOCs standards was observed by microscope,it was found that the above six VOCs standards caused a certain degree of damage to the mycelium of three poplar canker pathogens,and the mycelium of damaging was thickened,distortion,shortening,segmentation,swelling in the middle or at the end,deformity,fracture,increased number of terminal branches,bifurcation at the top,aggregation of internal protoplasm and so on.4.The poplar seedlings were treatmented with dimethyl disulfide for 9 days and transcriptome sequencing.Through the analysis and comparison,there were 129 differentially expressed genes related to disease resistance.Among them,there are 16 genes that increase cell wall lignin,20 disease-associated protein genes,55 pathways of ethylene and salicylic acid genes,13 lipoxygenase genes,19 related to SA signal transduction pathways genes,6 plant defense protein genes.There were 612 differentially expressed genes related to growth,including 428 genes related to phytohormone signal transduction pathways,56 biosynthesis genes of diterpenoids,95 biosynthesis genes of steroid skeletons,and 33 biosynthesis genes of zeatin.Fluorescent quantitative PCR was used to ten differentially expressed genes related to disease resistance,and ten differentially expressed genes related to growth.The results showed that the gene expression trends were consistent with biological information predictions.This study further reveals the induced resistance of B.pyrrocinia JK-SH007 to poplar canker at the molecular level,which opens a new way for comprehensive prevention and control of poplar disease.