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.

https://link.springer.com/content/pdf/10.1007%2Fs11104-016-2799-z.pdf

Physiological and genetic characterization of rice nitrogen fixer PGPR isolated from rhizosphere soils of different crops

In a previous study soybean Bradyrhizobium strains, used in Brazilian studies and inoculants over the last 30 years, and strains adapted to the Brazilian Cerrados, a region frequently submitted to environmental and nutritional stresses, were analyzed for 32 morphological and physiological parameters in vivo and in vitro. A cluster analysis allowed the subdivision of these strains into species Bradyrhizobium japonicum, Bradyrhizobium elkanii and a mixed genotype. In this study, the bacteria were analyzed for nodulation, N2 fixation capacity, nodule occupancy and the ability to increase yield. The goal was to find a relationship between the strain groups and the symbiotic performance. Two strains of Brazilian B. japonicum showed higher rates of N2 fixation and nodule efficiency (mg of N mg–1 of nodules) under axenic conditions. These strains also showed greater yield increases in field experiments when compared to B. elkanii strains. However, no differences were detected between B. japonicum and B. elkanii strains when comparing nodule occupancy capacity. The adapted strains belonging to the serogroup B. elkanii SEMIA 566, most clustered in a mixed genotype, were more competitive than the parental strain, and some showed a higher capacity of N2 fixation. Some of the adapted strains, such as S-370 and S-372, have shown similar N2 fixation rates and nodulation competitiveness to two Brazilian strains of B. japonicum. This similarity demonstrates the possibility of enhancing N2 fixing ability, after local adaptation, even within B. elkanii species. Differences in the DNA profiles were also detected between the parental SEMIA 566 and the adapted strains by analyses with the ERIC and REP-PCR techniques. Consequently, genetic, morphological and physiological changes can be a result of adaptation of rhizobia to the soil. This variability can be used to select strains capable of increasing the contribution of N2 fixation to soybean nutrition.

/pdf/nitrogen-fixation-capacity-and-nodule-occupancy-by-d4kdrwg5g5.pdf

Nitrogen fixation capacity and nodule occupancy by Bradyrhizobium japonicum and B. elkanii strains

In order to analyze the phylogeny of soybean-nodulating bacteria in alkaline soils in Vietnam, indigenous soybean-nodulating bacteria were isolated from root nodules by cultivating three kinds of Rj-soybean cultivars on two alkaline soils in Vietnam. The 120 isolates were classified into two major genera of soybean-nodulating rhizobia, namely Bradyrhizobium and Sinorhizobium genera, based on a growth analysis on medium and PCR-RFLP analyses of 16S rDNA and of the 16S–23S rDNA internal transcribed spacer (ITS) region. Most of the isolates of B. japonicum were extra-slow-growing and their ITS types were similar to that of B. japonicum USDA 135. They were not isolated from the soybean cultivar CNS used as Rj2Rj3 genotype. Isolates of Sinorhizobium were divided into two groups, S. fredii and S. sp., based on a PCR-RFLP analysis of 16S rDNA. Furthermore, PCR-RFLP analysis of the 16S–23S rDNA ITS region enabled to separate them into five types, three ITS types associated with S. fredii and two with S. sp. Sinor...

https://www.tandfonline.com/doi/pdf/10.1111/j.1747-0765.2005.tb00143.x

Phylogenetic analysis of soybean-nodulating rhizobia isolated from alkaline soils in Vietnam

https://bsnbiotech.files.wordpress.com/2010/11/risal_et_al_sam_33_2010_416_425.pdf

Genetic diversity of native soybean bradyrhizobia from different topographical regions along the southern slopes of the Himalayan Mountains in Nepal.

Diversity of indigenous Bradyrhizobium strains isolated from three different Rj-genotypes of soybean (Glycine max L. Merrill) cultivars which was investigated based on randomly amplified polymorphic DNA (RAPD) fingerprinting, intrinsic antibiotic resistance (JAR) and indole-3-aceticacid (IAA) production, was correlated with preference for and compatibility with Rj-genotypes of soybean cultivars for nodulation. Seventeen strains from Akishirome (nonRj), 22 strains from CNS (Rj 2 Rj 3) and 19 strains from Fukuyutaka (Rj 4) were isolated. All of the isolates from Akishirome and Fukuyutaka and 8 isolates from CNS formed effective nodules on each Rj-soybean cultivar, while 14 isolates from CNS did not form effective nodules on Fukuyutaka after inoculation under sterile conditions. The 14 isolates from CNS produced IAA. Cluster analysis based on RAPD fingerprinting using 5 primers revealed the presence of tw.o clusters, A and B. Cluster B contained B. elkanii USDA 61, USDA 76 and indigenous bradyrhizob...

https://www.tandfonline.com/doi/pdf/10.1080/00380768.2000.10409157

Diversity of Indigenous Bradyrhizobium Strains Isolated from Three Different Rj-Soybean Cultivars in Terms of Randomly Amplified Polymorphic DNA and Intrinsic Antibiotic Resistance

To determine the taxonomic relationship between Thai soybean bradyrhizobia and soybean bradyrhizobia from other regions, a total of 62 Bradyrhizobium strains were isolated in Thailand. The genetic ...

Hideo Imai

Papers

Genetic variability of the common nod gene in soybean bradyrhizobia isolated in Thailand and Japan.