Abstract
Soil microorganisms are key drivers of plant productivity in terrestrial ecosystems, yet controls on their diversities and abundances are not fully elucidated. Phenolic acids, released through plant root exudation and residues decomposition, are usually referred as autotoxins of several crops, including cucumber. In this study, effects of vanillic acid (VA) on cucumber rhizosphere microbial communities were investigated by treating cucumber seedlings with VA every two days for five times. Amplicon sequencing, PCR-denaturing gradient gel electrophoresis and quantitative PCR were used to analyzed the 16S rRNA genes of total bacterial, Pseudomonas and Bacillus spp. communities. Results showed that VA at 0.05 μmol g−1 soil changed total bacterial community diversity and composition. In particular, VA inhibited the relative abundances of genera with plant-beneficial potentials, such as Bacillus and Lysobacter spp. Moreover, VA changed Pseudomonas and Bacillus spp. community compositions by altering the number and/or relative abundances of their OTUs; and decreased Bacillus spp. community abundance at 0.02 to 0.2 μmol g−1 soil and Pseudomonas spp. community abundance at 0.2 μmol g−1 soil. Overall, VA changed cucumber seedling rhizosphere total bacterial, Pseudomonas and Bacillus spp. communities, which maybe be associated with the adverse effects of VA on cucumber growth under soil conditions.
Highlights
Soil microorganisms are responsible for the key processes associated with soil fertility and plant health, greatly influence the functioning of terrestrial ecosystems[8]
Compared with rhizosphere soils treated with water, rhizosphere soils treated with 0.05 μmol g−1 soil vanillic acid had higher relative abundances of Proteobacteria, Planctomycetes, Bacteroidetes, Gemmatimonadetes and Verrucomicrobia, but lower relative abundances of Acidobacteria, Firmicutes and Nitrospirae (P < 0.05) (Figs 1a, 2)
Our results revealed that vanillic acid changed cucumber rhizosphere total bacterial, Pseudomonas and Bacillus spp. community compositions, and Pseudomonas and Bacillus spp. community abundances
Summary
Soil microorganisms are responsible for the key processes associated with soil fertility and plant health, greatly influence the functioning of terrestrial ecosystems[8]. Pseudomonas and Bacillus spp. are ubiquitous in terrestrial ecosystems, and are frequently found in associations with plants, either as mutualists, saprophytes or pathogens. P. putida, B. pumilus, B. subtilis are able to promote cucumber growth, induce systemic resistance, and directly inhibit plant pathogens, such as Fusarium oxysporum f.sp. It has been shown that agricultural management regimes, including crop continuous monocropping, affected Pseudomonas and Bacillus spp. communities[16,20,21]. How phenolic acids affect soil Pseudomonas and Bacillus spp. communities are still not clear. Vanillic acid inhibited cucumber seedling growth and changed the whole bacterial community structure as evaluated by PCR-denaturing gradient gel electrophoresis (DGGE)[23]. Cucumber rhizosphere Pseudomonas and Bacillus spp. community structures and abundances were estimated by PCR-DGGE and quantitative PCR, respectively
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