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.…”

Diversity, Phylogeny and Plant Growth Promotion Traits of Nodule Associated Bacteria Isolated from Lotus parviflorus

“…We observed that many of these nodule inhabitants could exhibit activities potentially beneficial for plant growth and health, including phosphate solubilization, production of siderophores and lytic enzymes, as well as antagonism against two well-known phytopathogens, Phytophthora cinnamomi and Botryosphaeria cortícola. Endophytic bacteria with these beneficial activities are frequently found in legume tissue, including nodules [92][93][94]. The isolation of bacteria other than rhizobia from the interior of the legume nodules has been increasingly reported in precious years [28,[30][31][32][33]95].…”