Antagonistic endophytic bacteria associated with nodules of soybean ( Glycine max L.) and plant growth-promoting properties

Abstract

A total of 276 endophytic bacteria were isolated from the root nodules of soybean (Glycine max L.) grown in 14 sites in Henan Province, China. The inhibitory activity of these bacteria against pathogenic fungus Phytophthora sojae 01 was screened in vitro. Six strains with more than 63% inhibitory activities were further characterized through optical epifluorescence microscopic observation, sequencing, and phylogenetic analysis of 16S rRNA gene, potential plant growth-promoting properties analysis, and plant inoculation assay. On the basis of the phylogeny of 16S rRNA genes, the six endophytic antagonists were identified as belonging to five genera: Enterobacter, Acinetobacter, Pseudomonas, Ochrobactrum, and Bacillus. The strain Acinetobacter calcoaceticus DD161 had the strongest inhibitory activity (71.14%) against the P. sojae 01, which caused morphological abnormal changes of fungal mycelia; such changes include fracture, lysis, formation of a protoplast ball at the end of hyphae, and split ends. Except for Ochrobactrum haematophilum DD234, other antagonistic strains showed the capacity to produce siderophore, indole acetic acid, and nitrogen fixation activity. Regression analysis suggested a significant positive correlation between siderophore production and inhibition ratio against P. sojae 01. This study demonstrated that nodule endophytic bacteria are important resources for searching for inhibitors specific to the fungi and for promoting effects for soybean seedlings.

Isolation and Properties of Enterobacter sp. LX3 Capable of Producing Indoleacetic Acid

“…It was clear to cluster strain LX3 into clade of E. cloacae that had a 99.8% similarity, in which Enterobacter sp. CCBAU15492 appears related to E. cloacae [27]. Those phylogenetic results proved that strain LX3 must be part of genus Enterobacter.…”

Plant Biostimulants: Importance of the Quality and Yield of Horticultural Crops and the Improvement of Plant Tolerance to Abiotic Stress—A Review

“…The volatile substances also positively affect the dry matter content and root volume as well as the dry and fresh mass of the shoot [29]. Zhao et al [30] managed to isolate 276 endophytic bacteria from soybean root nodules that protected soybean roots against fungal infections of Phytophthora sojae. The antagonistic bacteria included Enterobacter spp., Acinetobacter spp., Pseudomonas spp., Ochrobactrum spp., and Bacillus spp.…”

Plant growth‐promoting rhizobacterial communities from an area under the influence of iron mining and from the adjacent phytophysiognomies which have high genetic diversity

“…(Armanhi et al, 2018;Cao et al, 2015;Castro et al, 2017;Chou et al, 2007;De Meyer et al, 2015;Hoque et al, 2011;Li et al, 2011;Lu et al, 2017;Sun et al, 2017;Thijs et al, 2014;Whang et al, 2014;Xiao et al, 2017). The other genera isolated have been registered in the literature as endophytic bacteria and plant growth promotors (Chen et al, 2001;Costa et al, 2016;Flores-Félix et al, 2014;Guglielmetti et al, 2013;Guimarães et al, 2012;Jaramillo et al, 2013;Mendis et al, 2018;Souza et al, 2015;Wang et al, 2017;Zhang et al, 2016;Zhao et al, 2017). Although the symbiotic relationships of these communities with siratro may be different from those with native Leguminosae species from each phytophysiognomy (Ribeiro et al, 2017;Santos et al, 2017), even rhizobia can act as PGPR by means of various processes, contributing to the sustainability of the ecosystems (Costa et al, 2016;Marra et al, 2012;Oliveira-Longatti et al, 2014).…”