Dataset Information

Co-Inoculation of Bacillus velezensis Strain S141 and Bradyrhizobium Strains Promotes Nodule Growth and Nitrogen Fixation.

ABSTRACT: The objective of this research was to evaluate the PGPR effect on nodulation and nitrogen-fixing efficiency of soybean (Glycine max (L.) Merr.) by co-inoculation with Bradyrhizobium diazoefficiens USDA110. Co-inoculation of Bacillus velezensis S141 with USDA110 into soybean resulted in enhanced nodulation and N2-fixing efficiency by producing larger nodules. To understand the role of S141 on soybean and USDA110 symbiosis, putative genes related to IAA biosynthesis were disrupted, suggesting that co-inoculation of USDA110 with S141?yhcX reduces the number of large size nodules. It was revealed that yhcX may play a major role in IAA biosynthesis in S141 as well as provide a major impact on soybean growth promotion. The disruption of genes related to cytokinin biosynthesis and co-inoculation of USDA110 with S141?IPI reduced the number of very large size nodules, and it appears that IPI might play an important role in nodule size of soybean-Bradyrhizobium symbiosis. However, it was possible that not only IAA and cytokinin but also some other substances secreted from S141 facilitate Bradyrhizobium to trigger bigger nodule formation, resulting in enhanced N2-fixation. Therefore, the ability of S141 with Bradyrhizobium co-inoculation to enhance soybean N2-fixation strategy could be further developed for supreme soybean inoculants.

SUBMITTER: Sibponkrung S

PROVIDER: S-EPMC7284691 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Co-Inoculation of Bacillus velezensis Strain S141 and Bradyrhizobium Strains Promotes Nodule Growth and Nitrogen Fixation.

Sibponkrung Surachat S Kondo Takahiko T Tanaka Kosei K Tittabutr Panlada P Boonkerd Nantakorn N Yoshida Ken-Ichi KI Teaumroong Neung N

Microorganisms 20200507 5

The objective of this research was to evaluate the PGPR effect on nodulation and nitrogen-fixing efficiency of soybean (Glycine max (L.) Merr.) by co-inoculation with Bradyrhizobium diazoefficiens USDA110. Co-inoculation of Bacillus velezensis S141 with USDA110 into soybean resulted in enhanced nodulation and N2-fixing efficiency by producing larger nodules. To understand the role of S141 on soybean and USDA110 symbiosis, putative genes related to IAA biosynthe ...[more]

PMID: 32392716

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Project description:Plant growth-promoting rhizobacteria (PGPR) may provide a biological alternative to fix atmospheric N2 and delay N remobilisation in maize plant to increase crop yield, based on an understanding that plant-N remobilisation is directly correlated to its plant senescence. Thus, four PGPR strains were selected from a series of bacterial strains isolated from maize roots at two locations in Malaysia. The PGPR strains were screened in vitro for their biochemical plant growth-promoting (PGP) abilities and plant growth promotion assays. These strains were identified as Klebsiella sp. Br1, Klebsiella pneumoniae Fr1, Bacillus pumilus S1r1 and Acinetobacter sp. S3r2 and a reference strain used was Bacillus subtilis UPMB10. All the PGPR strains were tested positive for N2 fixation, phosphate solubilisation and auxin production by in vitro tests. In a greenhouse experiment with reduced fertiliser-N input (a third of recommended fertiliser-N rate), the N2 fixation abilities of PGPR in association with maize were determined by 15N isotope dilution technique at two harvests, namely, prior to anthesis (D50) and ear harvest (D65). The results indicated that dry biomass of top, root and ear, total N content and bacterial colonisations in non-rhizosphere, rhizosphere and endosphere of maize roots were influenced by PGPR inoculation. In particular, the plants inoculated with B. pumilus S1r1 generally outperformed those with the other treatments. They produced the highest N2 fixing capacity of 30.5% (262 mg N2 fixed plant-1) and 25.5% (304 mg N2 fixed plant-1) of the total N requirement of maize top at D50 and D65, respectively. N remobilisation and plant senescence in maize were delayed by PGPR inoculation, which is an indicative of greater grain production. This is indicated by significant interactions between PGPR strains and time of harvests for parameters on N uptake and at. % 15Ne of tassel. The phenomenon is also supported by the lower N content in tassels of maize treated with PGPR, namely, B. pumilus S1r1, K. pneumoniae Fr1, B. subtilis UPMB10 and Acinetobacter sp. S3r2 at D65 harvest. This study provides evidence that PGPR inoculation, namely, B. pumilus S1r1 can biologically fix atmospheric N2 and provide an alternative technique, besides plant breeding, to delay N remobilisation in maize plant for higher ear yield (up to 30.9%) with reduced fertiliser-N input.

Project description:The co-inoculation of Bradyrhizobium with other non-bradyrhizobial strains was already assessed on cowpea, but the co-inoculation of two Bradyrhizobium strains was not tested up to now. This study aimed to evaluate the cowpea growth, N accumulation, and Bradyrhizobium competitiveness of the elite strain B. pachyrhizi BR 3262 when co-inoculated with other efficient Bradyrhizobium from the Brazilian semiarid region. Three potted-plant experiments were carried out. In the first assay, 35 efficient Bradyrhizobium isolates obtained from the semiarid region of Brazil were co-inoculated with the elite strains B. pachyrhizi BR 3262. The experiment was conducted in gnotobiotic conditions. The plant growth, nodulation, N nutritional variables, and nodular occupation were assessed. Under gnotobiotic and non-sterile soil conditions, ten selected bacteria plus the elite strain B. yuanmingense BR 3267 were used at the second and third experiments, respectively. The cowpea was inoculated with the 11 bacteria individually or co-inoculated with BR 3262. The plant growth and N nutritional variables were assessed. A double-layer medium spot method experiment was conducted to evaluate the interaction among the co-inoculated strains in standard and diluted YMA media. The co-inoculation treatments showed the best efficiency when compared to the treatments inoculated solely with BR 3262. This strain occupied a low amount of cowpea nodules ranging from 5 to 67.5%. The treatments with lower BR 3262 nodule occupancy showed the best results for the shoot nitrogen accumulation. The culture experiment showed that four bacteria inhibited the growth of BR 3262. In contrast, seven strains from the soils of Brazilian semiarid region were benefited by the previous inoculation of this strain. In the second and third experiments, the results indicated that all 11 co-inoculated treatments were more efficient than the single inoculation, proofing the best performance of the dual inoculation of Bradyrhizobium on cowpea.

Project description:It has been reported that supply of nitrate to culture solution rapidly and reversibly inhibits nodule growth and nitrogen fixation activity of soybean. In this study, the effects of ammonium, urea, or glutamine on nodule growth and nitrogen fixation activity are compared with that for nitrate. Soybean plants were cultivated with a nitrogen-free nutrient solution, then 1 mM-N of nitrate, ammonium, glutamine, or urea were supplied from 12 DAP until 17 DAP. Repression of nodule growth and nitrogen fixation activity at 17 DAP were observed by ammonium, urea, and glutamine like nitrate, although the inhibitory effects were milder than nitrate. The removal of nitrogen from the culture solutions after nitrogen treatments resulted in a recovery of the nodule growth. It was found that the glutamine treatment followed by N-free cultivation gave highest nitrogen fixation activity about two times of the control. Tracer experiments with 15N and 13C were performed to evaluate the translocation of N and C to the different tissues. Culture solutions containing a 15N-labeled nitrogen source were supplied from 21 DAP, and the whole shoots were exposed to 13CO2 for 60 min on 23 DAP, and plants were harvested on 24 DAP. The percentage distribution of 15N in nodules was highest for ammonium (1.4%) followed by glutamine (0.78%), urea (0.32%) and nitrate (0.25%). The percentage distribution of 13C in the nodules was highest for the control (11.5%) followed by urea (5.8%), glutamine (2.6%), ammonium (2.3%), and nitrate (2.3%). The inhibitory effects of nitrogen compounds appeared to be related to a decrease in photoassimilate partitioning in the nodules, rather than 15N transport into the nodules. The free amino acid concentrations after nitrogen treatments were increased in the nodules and leaves by nitrate, in the roots by ammonium, in the stems by urea, and the roots, stems, and leaves by glutamine treatment. The concentrations of asparagine, aspartate, and glutamine were increased after nitrogen treatments. By the long-term supply of nitrogen for 2-weeks, nitrate significantly increased the lateral roots and leaf growth. The long-term supply of urea and glutamine also promoted the lateral roots and leaf growth, but ammonium suppressed them.

Project description:Sulfur (S)-containing molecules play an important role in symbiotic nitrogen fixation and are critical components of nitrogenase and other iron-S proteins. S deficiency inhibits symbiotic nitrogen fixation by rhizobia. However, despite its importance, little is known about the sources of S that rhizobia utilize during symbiosis. We previously showed that Bradyrhizobium diazoefficiens USDA110T can assimilate both inorganic and organic S and that genes involved in organic S utilization are expressed during symbiosis. Here, we show that a B. diazoefficiens USDA110T mutant with a sulfonate monooxygenase (ssuD) insertion is defective in nitrogen fixation. Microscopy analyses revealed that the ΔssuD mutant was defective in root hair infection and that ΔssuD mutant bacteroids showed degradation compared to the wild-type strain. Moreover, the ΔssuD mutant was significantly more sensitive to hydrogen peroxide-mediated oxidative stress than the wild-type strain. Taken together, these results show that the ability of rhizobia to utilize organic S plays an important role in symbiotic nitrogen fixation. Since nodules have been reported to be an important source of reduced S used during symbiosis and nitrogen fixation, further research will be needed to determine the mechanisms involved in the regulation of S assimilation by rhizobia.IMPORTANCE Rhizobia form symbiotic associations with legumes that lead to the formation of nitrogen-fixing nodules. Sulfur-containing molecules play a crucial role in nitrogen fixation; thus, the rhizobia inside nodules require large amounts of sulfur. Rhizobia can assimilate both inorganic (sulfate) and organic (sulfonates) sources of sulfur. However, very little is known about rhizobial sulfur metabolism during symbiosis. In this report, we show that sulfonate utilization by Bradyrhizobium diazoefficiens is important for symbiotic nitrogen fixation in both soybean and cowpea. The symbiotic defect is probably due to increased sensitivity to oxidative stress from sulfur deficiency in the mutant strain defective for sulfonate utilization. The results of this study can be extended to other rhizobium-legume symbioses, as sulfonate utilization genes are widespread in these bacteria.

Dataset Information

Co-Inoculation of Bacillus velezensis Strain S141 and Bradyrhizobium Strains Promotes Nodule Growth and Nitrogen Fixation.

Publications

Co-Inoculation of <i>Bacillus</i> <i>velezensis</i> Strain S141 and <i>Bradyrhizobium</i> Strains Promotes Nodule Growth and Nitrogen Fixation.

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