Abstract
Application of diazotrophs (N2-fixing microorganisms) can decrease the overuse of nitrogen (N) fertilizer. Until now, there are few studies on the effects of diazotroph application on microbial communities of major crops. In this study, the diazotrophic and endospore-forming Paenibacillus triticisoli BJ-18 was inoculated into maize soils containing different N levels. The effects of inoculation on the composition and abundance of the bacterial, diazotrophic and fungal communities in the rhizosphere and root/shoot endosphere of maize were evaluated by sequencing the 16S rRNA, nifH gene and ITS (Inter Transcribed Spacer) region. P. triticisoli BJ-18 survived and propagated in all the compartments of the maize rhizosphere, root and shoot. The abundances and diversities of the bacterial and diazotrophic communities in the rhizosphere were significantly higher than in both root and shoot endospheres. Each compartment of the rhizosphere, root and shoot had its specific bacterial and diazotrophic communities. Our results showed that inoculation reshaped the structures of the bacterial, diazotrophic and fungal communities in the maize rhizosphere and endosphere. Inoculation reduced the interactions of the bacteria and diazotrophs in the rhizosphere and endosphere, while it increased the fungal interactions. After inoculation, the abundances of Pseudomonas, Bacillus and Paenibacillus in all three compartments, Klebsiella in the rhizosphere and Paenibacillus in the root and shoot were significantly increased, while the abundances of Fusarium and Giberella were greatly reduced. Paenibacillus was significantly correlated with plant dry weight, nitrogenase, N2-fixing rate, P solubilization and other properties of the soil and plant.
Highlights
Plants host distinct microbial communities on and inside their tissues, designated as the plant microbiome [1,2,3]
Paenibacillus was significantly correlated with plant dry weight, nitrogenase, N2 -fixing rate, P solubilization and other properties of the soil and plant
The population densities of P. triticisoli BJ-18 in the maize rhizosphere and root/shoot endosphere were determined by qPCR with the specific primers for the nifH gene of P. triticisoli BJ-18 during the plant growth period from Days 7 to 35
Summary
Plants host distinct microbial communities on and inside their tissues, designated as the plant microbiome [1,2,3]. The microorganisms in the plant microbiome could be beneficial, harmful or neutral, according to their effects on plant development [4]. Rhizobacteria in the plant rhizosphere are more active in this zone and possess diverse metabolic capabilities and play a crucial role in plant health and soil fertility [5]. Many rhizobacteria are PGRB (plant growth-promoting rhizobacteria), inhabiting around or on the root surface, and may directly or indirectly promote plant growth and development in the vicinity of the rhizosphere [6,7]. Endophytes that live inside plant tissues for at least part of their life cycles do not cause harm and could establish a mutualistic association [8,9]. The mechanisms used by endophytic bacteria to promote plant growth are similar to PGPR
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