| Agricultural chemicals and inorganic fertilizers are used to control plant diseases and promote plant growth,but their improper or excessive use has caused a series of food safety and environmental pollution problems.In recent years,the application effect of beneficial microorganisms in plant biocontrol and growth promotion has been widely concerned.Bacillus,a large group of potentially beneficial bacteria,is commonly exist in soil,has been used to control plant diseases and promote plant growth.Bacillus amyloliquefaciens Ba13 obtained in previous studies has the biological functions of promoting plant growth,antagonizing plant pathogens and inducing plant systemic resistance.In order to explore the potential mechanism of strain Ba13 in promoting plant growth,antagonizing plant pathogens and inducing plant anti-virus function,genes and pathways related to biocontrol and growth-promoting functions were predicted based on the results of whole-genome sequencing of strain Ba13.In further experiments,biochemistry and liquid chromatography were used to analyze the biosynthesis of related growth-promoting substances;at the same time,the antagonistic ability of strain Ba13 to the pathogen of tomato bacterial wilt was tested in Petri dishes and pot experiments.Finally,pot experiments were conducted to study the effect of strain Ba13 in inducing plant antiviral diseases,combined with plant transcriptome and virus genome methylation detection to reveal the potential mechanism of plant resistance induced by strain Ba13.The main results are as follows:1.Plant growth-promoting ability: The results of whole genome sequencing of strain Ba13 predicted that it could synthesize IAA through IPA pathway,producing VOCs(2,3-butanediol and Acetoin)with growth-promoting activity,and secrete extracellular protein with growth-promoting function: Phytase through Sec pathway.Further experiments showed that the culture medium of strain Ba13 contained all intermediates of the process in synthesizing IAA through IPA pathway,and the concentration of IAA in the culture medium reached 7.26μg/m L.In pot experiment that verify the growth-promoting activity of the strain,the plant height and fresh weight of tomato treated with Ba13 strain increased significantly by 10.98%and 20.15% respectively.2.Antipathogenic ability: The results of genome sequencing predicted that strain Ba13 could secrete antifungal protein β-1,3-1,4 glucanase and synthesize antibiotics such as Surfactin,Bacillaene,Bacillomycin D,Bacillibactin,Bacilysin.Furthermore,antagonistic effect of strain Ba13 against Ralstonia solanacearum CQPS-1 was tested in Petri dishes,and the diameter of bacteriostatic zone was 15.37 ± 0.96 mm.In the pot experiment,strain Ba13 played a significant role in control tomato bacterial wilt caused by R.solanacearum CQPS-1,and the Control Efficiency was 37.5%.3.Antiviral disease ability: Plants pre-inoculated with strain Ba13 increased the expression of disease resistance-related HR genes(Rboh 1.51-Fold,RPM1 3.55-Fold,RPS21.83-Fold and FLS2 2.83-Fold)、TGS pathway-related genes(AGO3 2.94-Fold,DCL2 1.34-Fold)and growth-related IAA-responsive genes(AUX/IAA 1.72-Fold,ARF 1.52-Fold).In the follow-up experiment,the results of methylation detection showed that the methylation degree of multiple methylation sites(Position: 39,228,461)of virus DNA in plant leaves increased with treatment of Ba13.The pot experiment result showed that the virus content in the leaves of strain Ba13 decreased by 55.95% on the 28 th day and the height,stem branching numbers,fresh weight of plants increased by 13.63%,11.01%,31.50% respectively.To sum up: B.amyloliquefaciens Ba13 secreted plant hormone IAA and had the potential to synthesize extracellular growth-promoting proteins,growth-promoting VOCs,antibiotics and antifungal proteins.Strain Ba13 had obvious effect of anti-bacterial wilt and plant growthpromoting.Meanwhile,B.amyloliquefaciens Ba13 can regulate disease-resistence pathway like plant HR and TGS to improve the anti-virus capability of tomato. |
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