Abstract
Aiming at revealing the possible mechanism of its growth promoting effect on tomato, the correlations among Streptomyces sp. TOR3209 inoculation, rhizobacteriome, and tomato growth/production traits were investigated in this study. By analyses of Illumina sequencing and plate coating, differences in rhizosphere microbial communities were found in different growth stages and distinct inoculation treatments. The plant biomass/fruit yields and relative abundances of families Flavobacteriaceae, Sphingobacteriaceae, Polyangiaceae and Enterobacteriaceae in treatments T (tomato inoculated with TOR3209) and TF (tomato inoculated with TOR3209 + organic fertilizer) were higher than that in the controls (CK and CK+ organic fertilizer), respectively. The analysis of Metastats and LEfSe revealed that the genera Flavobacterium and Sorangium in seedling stage, Klebsiella in flowering stage, Collimonas in early fruit setting stage, and genera Micrococcaceae, Pontibacte and Adhaeribacter in late fruit setting stage were the most representative rhizobacteria that positively responded to TOR3209 inoculation. By cultivation method, five bacterial strains positively correlated to TOR3209 inoculation were isolated from rhizosphere and root endosphere, which were identified as tomato growth promoters affiliated to Enterobacter sp., Arthrobacter sp., Bacillus subtilis, Rhizobium sp. and Bacillus velezensis. In pot experiment, TOR3209 and B. velezensis WSW007 showed joint promotion to tomato production, while the abundance of inoculated TOR3209 was dramatically decreased in rhizosphere along the growth of tomato. Conclusively, TOR3209 might promote the tomato production via changing of microbial community in rhizosphere. These findings provide a better understanding of the interactions among PGPR in plant promotion.
Highlights
Rhizosphere refers to the narrow region of soil in the vicinity of plant roots, where the physicochemical traits of soil and the microbiome are quite different from those in bulk soil, because the influence of root secretions and metabolism
Many studies have demonstrated that PGPR play a key role in affecting the biological characteristics of plants through changes in composition and structure of rhizobiome, most of the studies have focused on only one time point and one influencing factors, and the regulation of rhizomicrobiome by a certain microorganism in the entire life cycle of plant growth has been rarely s tudied[7]
Based on the threshold of 97% sequence identity, these sequences were clustered into 6631–11,844 operational taxonomic units (OTUs) depending on the replicate and treatment, which presented coverages ≥ 90.85% (Table 1), and the OTU Shannon rarefaction curve
Summary
Rhizosphere refers to the narrow region of soil in the vicinity of plant roots, where the physicochemical traits of soil and the microbiome are quite different from those in bulk soil, because the influence of root secretions and metabolism. Some other studies have shown that PGPR can improve plant resistance and promote plant growth by changing soil microbial c ommunity[10,11]. Non-cultivation methods with highthroughput sequencing technology have been widely applied in studies on rhizomicrobiome that overcome the limits of microbial culture and isolation technology These non-cultivation methods have greatly improved our understanding about the composition and function of microbiome in different environments, and provided a more direct way to detect the microbes, especially those difficult to isolate and cultivate. TOR3209 was isolated from rhizosphere of tomato as a PGP strain in our previous study[14] The inoculation of this strain could increase the disease resistance and promote growth of several plants, including pear trees, tomatoes and golden silk jujube[15,16]. TOR3209 could change the rhizobiome and in turn to achieve the growth promotion effects; and (2) to discover the PGP effects of microbial species that responded to the TOR3209 inoculation for further explaining its PGP mechanism
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