Abstract
Plant growth-promoting rhizobacteria (PGPR) are noticeably applied to enhance plant nutrient acquisition and improve plant growth and health. However, limited information is available on the compositional dynamics of rhizobacteria communities with PGPR inoculation. In this study, we investigated the effects of three PGPR strains, Stenotrophomonas rhizophila, Rhodobacter sphaeroides, and Bacillus amyloliquefaciens on the ecophysiological properties of Oilseed rape (Brassica napus L.), rhizosphere, and bulk soil; moreover, we assessed rhizobacterial community composition using high-throughput Illumina sequencing of 16S rRNA genes. Inoculation with S. rhizophila, R. sphaeroides, and B. amyloliquefaciens, significantly increased the plant total N (TN) (p < 0.01) content. R. sphaeroides and B. amyloliquefaciens selectively enhanced the growth of Pseudomonadacea and Flavobacteriaceae, whereas S. rhizophila could recruit diazotrophic rhizobacteria, members of Cyanobacteria and Actinobacteria, whose abundance was positively correlated with inoculation, and improved the transformation of organic nitrogen into inorganic nitrogen through the promotion of ammonification. Initial colonization by PGPR in the rhizosphere affected the rhizobacterial community composition throughout the plant life cycle. Network analysis indicated that PGPR had species-dependent effects on niche competition in the rhizosphere. These results provide a better understanding of PGPR-plant-rhizobacteria interactions, which is necessary to develop the application of PGPR.
Highlights
Stenotrophomonas rhizophila and Bacillus amyloliquefaciens treatments significantly increased the soluble protein content in the plant, whereas the Rhodobacter sphaeroides treatment caused a significant decrease of total C (TC) compared to the CK treatment
Rs treatment significantly increased the concentrations of K (7.08%), NH4 + (250.95%), and TC (28.17%) in rhizosphere soil compared with bulk soil (Table 3)
Based on quantitative PCR and the bacterial community structure analysis with four stages, it was demonstrated that, the plant growth-promoting rhizobacteria (PGPR) cannot colonize the rhizosphere in a persistent manner, the effect of PGPR on the rhizobacterial community was long-lasting
Summary
The rhizosphere is one of the most complex Critical Zone (CZ) ecosystems in which plant growth-promoting rhizobacteria (PGPR) plays an indispensable role [1], as these organisms can promote plant growth or health, either directly or indirectly [2], through a wide variety of mechanisms including biological nitrogen fixation [3], phosphate solubilization [4], siderophore production [5], production of 1-aminocyclopropane-1-carboxylate deaminase (ACC) [6], phytohormone production [7], quorum sensing (QS) [1], induction of systemic resistance [8], and interference with pathogen toxin production [9]. B. amyloliquefaciens can suppress Fusarium disease by manipulating rhizosphere microbial community composition and stimulating potentially beneficial taxa [13]. It has been reported that treatment with B. amyloliquefaciens could markedly improve the plant growth and resist plant viral disease by changing rhizosphere microbial community structure and enhancing plant systemic resistance [14]. Wu [10] found that B. amyloliquefaciens had the dual effects of promoting plant growth and reducing N2 O emissions by changing the rhizosphere microbial community structure. These studies indicate the complex interactions that exist between PGPR strains and the native rhizosphere microbial community
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