Physiological and genetic characterization of rice nitrogen fixer PGPR isolated from rhizosphere soils of different crops
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We aimed to identify plant growth-promoting rhizobacteria that could be used to develop a biofertilizer for rice.
To obtain plant growth-promoting rhizobacteria, rhizosphere soils from different crops (rice, wheat, oats, crabgrass, maize, ryegrass, and sweet potato) were inoculated to rice plants. In total, 166 different bacteria were isolated and their plant growth-promoting traits were evaluated in terms of colony morphology, indole-3-acetic acid production, acetylene reduction activity, and phosphate solubilization activity. Moreover, genetic analysis was carried out to evaluate their phylogenetic relationships based on 16S rRNA sequence data.
Strains of Bacillus altitudinis, Pseudomonas monteilii, and Pseudomonas mandelii formed associations with rice plants and fixed nitrogen. A strain of Rhizobium daejeonense showed nitrogen fixation activity in an in vitro assay and in vivo. Strains of B. altitudinis and R. daejeonense derived from rice rhizosphere soil, strains of P. monteilii and Enterobacter cloacae derived from wheat rhizosphere soil, and a strain of Bacillus pumilus derived from maize rhizosphere soil significantly promoted rice plant growth.
These methods are effective to identify candidate species that could be developed as biofertilizers for target crops.
KeywordsRhizosphere Plant growth promoting rhizobacteria Rice Nitrogen fixation IAA Phosphate solubilization 16S rRNA Bacillus altitudinis Pseudomonas monteilii Pseudomonas mandelii Rhizobium daejeonense
Plant growth promoting rhizobacteria
Acetylene reduction assay
Polymerase chain reaction
DNA data bank Japan
Basic local alignment search tool
Japan Atomic Energy Agency
Randomized block design
This study was supported by the Special Research Fund of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan titled “Research and development of security and safe crop production to reconstruct agricultural lands in Fukushima prefecture based on novel techniques to remove radioactive compounds using advanced bio-fertilizer and plant protection strategies”. This work was also supported by a Grant-in-Aid for Scientific Research (B):24380176 from the Japan Society for the Promotion of Science (JSPS).
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