Nodule Mass Research Articles

Fungal nutrition allocation enhances mutualism with fungus-growing termite

Fungal nodules and aged fungus gardens are products of termite fungiculture systems, and are the diets of termites. To understand the nutrition flow in fungiculture, we quantified the number and mass of fungal nodules produced along with fungus garden maturation and analysed the α-amino acid and fatty acid compositions of fungal nodules, fungus gardens, and termite tissues of a fungus-growing termite, Odontotermes formosanus. 1 g of fungus garden produced 5,148 fungal nodules (∼68.0 mg). Approximately 7.0% of α-amino acids were allocated to the fungal nodules and the rest (∼93.0%) remained in the fungus gardens. The compositions of α-amino acids or fatty acids in aged fungus gardens and fungal nodules were more similar to that of termite tissues than fresh fungus gardens, which supports the idea that termites nutritionally depend on the fungal products. Among the 18 α-amino acids, tryptophan was an essential amino acid and was the only one missing from fresh and aged fungus gardens, but found in fungal nodules at significantly higher concentrations. Hence, termites must consume fungal nodules to obtain tryptophan for survival. Furthermore, the fungus spores incorporated in nodules, were transferred when nodules were ingested by termites. We propose that allocating tryptophan in fungal nodules is crucial to enhance the mutualism between the fungus and termite.

Nodulation and biological nitrogen fixation (BNF) in forage peanut (Arachis pintoi) cv. Belmonte subjected to grazing regimes

Productivity of grassland ecosystems is highly dependent on the availability of nitrogen (N) from the soil and/or biological fixation (BNF) from the atmosphere. However, the high cost of N-fertilizers and the increasing awareness of the need for sustainable nutrient alternative sources have increased the strategic importance of the BNF. Defoliation interferes with plant growth and also with BNF in legumes, since it modifies the leaf area and the availability of energy to plants. In spite of the potential advantages of forage legumes to pastures, current knowledge regarding the effects of grazing management on BNF is scarce. In order to evaluate the effect of grazing management on aerial and root mass, nodulation and BNF in forage peanut (Arachis pintoi cv. Belmonte), two experimental protocols based on the continuous and intermittent (rotational grazing) stocking methods were used. In the continuous stocking protocol, treatments corresponded to four grazing intensities represented by four management heights - 5, 10, 15 and 20 cm. In the intermittent stocking protocol, treatments corresponded to combinations between two pre- (95% and maximum canopy light interception during regrowth – LI95% and LIMax, respectively) and two post-grazing (post-grazing heights equivalent to 40 and 60% of the pre-grazing height) conditions. It was hypothesized that hard grazing, represented by low management heights under continuous stocking or low post-grazing heights under intermittent stocking, causes reduction in root mass and nodulation interfering with the balance between root and aerial, with negative impacts on BNF. Under continuous stocking, greater number of nodules was associated with lower nodule mass and vice-versa throughout the year. Swards managed at 5 and 10 cm had greater root and nodule mass than those managed at 15 and 20 cm. However, greater BNF (%Ndfa and BNF) was recorded on swards managed at 15 and 20 cm relative to those managed at 5 and 10 cm. Under intermittent stocking, the combinations between frequencies and severities of grazing did not affect root mass or nodule number at both pre- and post-grazing conditions. Overall, swards managed with the LIMax target showed greater BNF than those managed with the LI95% target. For swards managed with the same LI target (LI95% or LIMax), hard grazing (40% of the pre-grazing height) resulted in lower %Ndfa and BNF during early and late spring and summer II. For both grazing methods, the range of management targets used did not result in negative impacts on root mass or nodulation. Regardless of grazing method, BNF was determined by aerial biomass, indicating that moderate intensities of grazing would be adequate for optimizing BNF.

Nitrogen fixation characteristics of root nodules in different peanut varieties and their relationship with yield.

Root nodules in peanut (Arachis hypogaea L.) could directly utilize nitrogen (N) in the atmosphere as N source, which plays an important role in the N supply in peanut. However, little is known about the mechanism of efficient N fixation by root nodule. In this study, 15N tracer technology was used to investigate the characteristics of N fixation by root nodule and its relationship with peanut yields of 19 varieties in a pot culture experiment. Results showed that there were significant differences in nodule number, fresh quality, internal material, N fixation amount and other related indices among different varieties. The range of number and fresh mass of root nodule was 170.59-696.15 per pot and 0.83-3.74 g per pot, with coefficients of variation (CV) of 36.1% and 41.1%, respectively. The range of leghaemoglobin content and nitrogenase activity was 15.51-23.23 mg per pot and 2.75-20.46 μmol C2H4·h-1 per pot, with CV of 13.1% and 57.2%, respectively. The CV of nitrogenase activity was significantly higher than that of leghaemoglobin content, indicating that nitrogenase activity was not only affected by leghaemoglobin content but also other factors. The range of N fixation by root nodule and total N accumulation was 0.71-1.82 and 2.16-3.72 g per pot, with CV of 21.6% and 12.9%, respectively. The CV of the former was significantly higher than that of the latter, indicating that other N sources could automatically compensate the deficit when N fixation of root nodule was insufficient. Nitrogen fixation by root nodule was one of the main N sources for peanut, while the average N supply percentage was more than 40% of the total N, with a maximum of 50%. Cultivating the variety with high N supply capacity is an effective way for N-saving cultivation in the peanut production. Except for nodule number, there were significantly positive correlations between the other indices and peanut yield, indicating that the physiological indicators of N fixation were closely related to N fixation capacity by root nodule and the final yield. Therefore, enhancing these characters would help achieve high yield of peanut and simultaneously reduce fertilizer application.

Enhancing Effects of Phosphorous Enriched Citrus Waste Compost on Nodulation and Various Yield Attributes of Mung Bean in Peshawar District

Lack of knowledge with farmers regarding the use of optimum fertilizers rate is one of the key cause of diminishing productivity of our soil. The current study was conducted with an aim to evaluate comparison between inorganic phosphorous fertilizers and phosphorous enriched citrus waste compost in enhancing the nodulation and obtaining economical yield of mungbean. The field trail was operated in Rabi season 2018-2019 using RCB design with 8 treatments and 3 replications. Total 8 treatments were used such as T1 (Control), T2 (Citrus waste compost alone) T3 (DAP alone), T4 (rock phosphate alone), T5 (SSP alone), T6 (4% DAP enriched CW compost), T7 (4% RP enriched CW compost), T9 (4% SSP enriched CW compost) and each treatment was replicated three times. The outcomes of the field trail showed that all the phosphorous treatment has significantly affected the nodulation and grain yield of mungbean but treatments containing phosphorous enriched citrus waste compost was far better in results as compared to treatments containing alone mineral fertilizers. Treatment containing 4% DAP enriched citrus waste compost has significantly increased the grain yield, plant height and number of pods per plant up to 65%, 49% and 43% respectively significantly followed by treatments containing 4% SSP and 4% RP enriched citrus waste compost. However, in case of nodulation maximum values were obtained for treatment receiving alone RP increasing the number and mass of nodules up to 72% and 64%. It was concluded that pretreatment of DAP with citrus waste compost makes the soil favorable for long term phosphorous uptake resulting in better grain yield and yield attributes of mungbean. Though the DAP enriched citrus waste compost was best in our results, but other levels and their consequent effect on soil and crop yields should be assessed along with their environmental risks for wider and long term recommendations.

Physiological potential and initial development of soybean plants as a function of seed treatment

ABSTRACT Seed treatment is a process that helps to control insects and soil-borne pathogens, besides allowing a given crop to reach its maximum production potential and protect its seedlings. This study aimed to evaluate the physiological performance of seeds and the initial development of soybean, as a function of seed treatment. The study was based on a completely randomized design, with five treatments [imidacloprid + thiodicarb (75 + 225 g a.i. 100 kg-1 of seeds); chlorantraniliprole (62.5 g a.i. 100 kg-1 of seeds); cyantraniliprole (72 g a.i. 100 kg-1 of seeds), fipronil + thiophanate-methyl + pyraclostrobin (5 + 45 + 50 g a.i. 100 kg-1 of seeds); and control (seeds without treatment)]. Initially, the physiological quality of the seeds was evaluated by determining the first germination count, final germination and accelerated aging, with four replications. After that, the effect of the seed treatment on the soybean plant development was evaluated by analyzing the leaf area, number of leaves, shoot height, root and shoot dry mass and fresh mass of root nodules, with ten replications. The seed treatment with fipronil + pyraclostrobin + thiophanate-methyl allows an increased germination when the seeds are subjected to the accelerated aging test, besides an increment in the shoot height and leaf area of the plants.

English

Pre-inoculation of soybean seeds with Bradyrhizobium spp. associated with polymers could be an alternative to the conventional inoculation performed at the day of sowing. The objectives of this study were i) to determine whether the HiCoat® technology (peat inoculant + liquid inoculant + polymer) allows the survival of B. elkanii after storage of the inoculated seeds, and ii) to evaluate whether the pre-inoculation and seed treatment reduces the physiological quality of seed and soybean yield. Soybean seeds were treated with different fungicides and insecticides associated with pre-inoculation using HiCoat® and the seeds were stored at room temperature. The survival of B. elkanii was reduced over time with standard inoculation, however there was above 2 x 106 colony-forming units of B. elkanii per seed at 60 days after inoculation with HiCoat®. Seed germination, number of nodules per plant, mass of nodules, yield, number of grains per plant and number of pods per plants were not significantly affected by the pre-inoculation and seed treatments. Our findings indicated that the fungicide and insecticide associated with HiCoat® can be used to treat and to pre-inoculate seeds that can be stored for up to 71 days without compromising the nodulation of plants and soybean yield. Key words: Industrial seed treatment, biological nitrogen fixation, storage period, fungicide, insecticide, polymer, HiCoat, Glycine max.

Nodulation and Development of Soybean Submitted to Inoculation With Bradyrhizobium japonicum and Phosphorus Doses

Among the several factors that may influence nodulation and the efficiency of biological nitrogen fixation for soybean plants, nutrient availability is among the most important. This study aimed to evaluate the inoculation with Bradyrhizobium japonicum and doses of phosphorus on the development of soybean in a Vertisol, in Tocantins. The experimental design was completely randomized in a 4 × 2 factorial scheme, with four replications. Four doses of phosphate fertilization (0, 100, 200, and 300 kg ha-1 P2O5) were studied, combined with two inoculation treatments with Bradyrhizobium japonicum (inoculated and not inoculated). The following variables were evaluated: plant height, stem diameter, nodules per plant, dry mass of nodules, dry mass of plant, dry mass of root, number of pods and number of grains per pod. Under greenhouse conditions and soil with good availability of phosphorus, there is no influence of the doses on the inoculation with Bradyrhizobium japonicum. Soils with good availability of phosphorus have low response to the application of phosphate fertilizer.

Probability distribution for size and mass of a nodule in the KR5 area for the development of a manganese nodule miner

In this paper, probability distribution for the size and mass of seafloor manganese nodules is investigated to improve the reliability of a pick-up device in a deep-sea manganese nodule miner. Because the size and mass of the manganese nodules are strongly correlated, statistical models for the size and mass cannot be estimated independently. In order to consider the correlation between the size and mass in a statistical model, the joint probability density function (PDF) is estimated by using copula. This method requires the estimation of the marginal distributions and copula for the two correlated environmental variables. However, this is significantly difficult when there is no prior knowledge of the two physical properties. The proposed method, which employs the Akaike information criterion to select the fittest marginal distributions and copula, provides a systematic procedure to determine a statistical model of correlated environmental variables without any prior knowledge of their distributions. To demonstrate the effectiveness of the proposed method, the joint PDF for the size and mass of manganese nodules is modeled by using the multivariate normal distribution and the proposed method. It was found that the proposed method provides more accurate and reliable estimation results for the two correlated environmental variables.

Inoculation of soybean seeds coated with osmoprotector in diferents soil pH's

Inoculation with nitrogen-fixing bacteria ( Bradyrhizobium ) is an indispensable technology to increase the productivity of the soybean crop. The objective of this study was to evaluate the viability of the inoculation with Bradyrizobium bacteria associated with the osmoprotector coating on different pre-sowing days and the effect of different soil pH on the components of yield, nodulation and grain yield of soybean. Two soybean cultivars were used, sown in two seasons and submitted to soil pH of 5.3 and 6.5. The seeds were inoculated at different pre-sowin periods with Bradyrizobium bacteria in the presence or absence of osmoprotectants. In the cultivar NA 5909RG (pH 5.3), the seeds inoculated with Bradyrhizobium and osmoprotector, at four and seven days of pre-sowing, presented an increase of 10.8% and 8.3% of productivity, in relation to those without osmoprotector. The osmoprotector and the inoculation of Bradyrhizobium increases the number and dry mass of nodules in soil with more acidic pH. The soil of lower acidity is responsible for higher grain yield, compared to the higher acidity, when both were not inoculated. The variable with the greatest explanatory power and contribution in the variability in the data of the experiment is the grain yield.

Screening Cowpea Genotypes for High Biological Nitrogen Fixation and Grain Yield under Drought Conditions

Core Ideas Cowpea nodule biomass was more sensitive to water stress compared to shoot biomass. Rainfed conditions resulted in 57% decrease in N2 fixation compared to well‐watered. Inter‐seasonal variability in rainfall accounted for 58% difference in cowpea grain yield. Future increase in drought and heat stress will challenge legume productivity in many regions. In Sub‐Saharan Africa, legumes are earmarked as an integral component in building resilience to climate change and food security in smallholder farming systems. Hence, the need for continuous screening of drought tolerant legume genotypes for sustained productivity. A 2‐yr field study was conducted to identify superior cowpea genotypes with high biological nitrogen fixation (BNF), grain yield, and drought tolerance. Four genotypes, selected from a pool of 91, were grown under four moisture levels ranging from well‐watered (WW) to severe water stress (SS). Grain yield, shoot biomass, nodule mass, and BNF were determined. There was significant effect of water stress on the measured parameters. Nodule mass and BNF were more sensitive to water stress compared to shoot biomass across genotypes. Water stress resulted in 80% reduction in nodule biomass between WW and SS. As a result, cowpea genotypes grown under SS conditions fixed 57% less N2 compared to those under WW. The study also revealed significant genotypic variation in shoot biomass, grain yield, and BNF. Genotype TVu4607 was low in grain yield but performed better for BNF (71 kg N ha−1 under WW and 30 kg N ha−1 under SS). Genotype IT00K‐1263, proved to be our superior genotype with a good balance of biomass, BNF and grain yield. Our findings suggest that future water stress may significantly affect cowpea productivity, mostly its capacity to fix nitrogen. Consequently, adaptation strategies to improve drought resistance in cowpea are needed, particularly improvement of BNF under water stress.

Metabolomics and Transcriptomics in Legumes Under Phosphate Deficiency in Relation to Nitrogen Fixation by Root Nodules.

Phosphate (Pi) deficiency is a critical environmental constraint that affects the growth and development of several legume crops that are usually cultivated in semi-arid regions and marginal areas. Pi deficiency is known to be a significant limitation for symbiotic nitrogen (N2) fixation (SNF), and variability in SNF is strongly interlinked with the concentrations of Pi in the nodules. To deal with Pi deficiency, plants trigger various adaptive responses, including the induction and secretion of acid phosphatases, maintenance of Pi homeostasis in nodules and other organs, and improvement of oxygen (O2) consumption per unit of nodule mass. These molecular and physiological responses can be observed in terms of changes in growth, photosynthesis, and respiration. In this mini review, we provide a brief introduction to the problem of Pi deficiency in legume crops. We then summarize the current understanding of how Pi deficiency is regulated in legumes by changes in the transcriptomes and metabolomes found in different plant organs. Finally, we will provide perspectives on future directions for research in this field.

Rising CO2 accelerates phosphorus and molybdenum limitation of N2-fixation in young tropical trees

Nitrogen fixation may be critical for supplying the nitrogen (N) needed to maintain the tropical carbon sink in a world of rising atmospheric CO2. However, we do not know whether increased CO2 acts to exacerbate nutrient limitation on the fixation process itself. We experimentally test this idea by growing N2-fixing plants in pre-Industrial (280 ppm), present-day (400 ppm), and doubled (800 ppm) atmospheric CO2. In a greenhouse experiment, we grew tree seedlings from N2-fixing species and a non-fixing species at three CO2 concentrations with control, +P (phosphorus), +Mo (molybdenum), and + P +Mo nutrient treatments. We found nutrient limitation to be minimal at pre-Industrial CO2, but with increasing CO2 fixer growth and fixation became increasingly limited by P and by a P-by-Mo interaction. At 400 ppm, plants with +P grew ~50% faster and fixed 10-15× more N2 based on nodule mass and nitrogenase activity. At 800 ppm, plants with +P +Mo grew 200% more, and fixed 25× more N2, suggesting Mo-P co-limitation at elevated CO2. Our findings imply that complex patterns of nutrient limitation can develop as CO2 rises, potentially suppressing tropical N2-fixation and the new inputs of N needed to sustain the tropical carbon sink.

Evaluation of T categories for pure ground-glass nodules with semi-automatic volumetry: is mass a better predictor of invasive part size than other volumetric parameters?

This study aimed to investigate the diagnostic advantage of nodule mass in differentiating invasive pulmonary adenocarcinomas (IPAs) among pure ground-glass nodules (pGGNs) over other volumetric measurements. Another aim of this study was to analyse the correlation between volumetric measurements on computed tomography (CT) scans and the pathological invasive component size. This Institutional Review Board-approved retrospective study included 117 patients (men:women = 53:64; mean age, 57.3 years) with 117 pGGNs. Semi-automatic segmentation was performed for all nodules, and volumetric measurements, such as nodule volume, attenuation, mass, two-dimensional (2D) average diameter and three-dimensional (3D) longest diameter, were obtained. Receiver operating characteristic (ROC) curve analyses were performed to evaluate the diagnostic performances of the volumetric parameters in discriminating IPAs. Spearman correlation coefficients were calculated between the volumetric measurements and the invasive component size. Area under the ROC curve for mass was 0.792 (95% CI, 0.691-0.872) in non-enhanced CT and 0.730 (95% CI, 0.607-0.832) in contrast-enhanced CT. Nodule mass was not superior to 2D average diameter for the differentiation of IPAs in both non-enhanced (0.792 vs 0.780; p = 0.501) CT and contrast-enhanced CT scans (0.730 vs 0.700; p = 0.319). The correlation between the volumetric measurements (mass, 3D longest diameter and 2D average diameter) and the invasive component size was moderate (Spearman's rho, 0.401-0.422) in non-enhanced CT and weak (Spearman's rho, 0.276-0.310) in contrast-enhanced CT. Nodule mass measurement had no strength over other volumetric parameters for the prediction of pathological invasiveness in the diagnosis of pGGNs. • Mass is not superior to other volumetric measurements for the diagnosis of pure ground-glass nodules. • Mass and two-dimensional average diameter exhibited comparable performance for the discrimination of invasive adenocarcinomas among pure ground-glass nodules. • The diagnostic performance of volumetric measurements was lower on contrast-enhanced CT scans. • The correlation between the volumetric measurements and the invasive component size was moderate on non-enhanced CT scans and weak on contrast-enhanced CT scans.

The volume and mass growth of persisted pulmonary nodules detected in low-dose CT screening and its influence factors

Objective: To evaluate the changes of volume and mass of pulmonary nodules which were detected in low-dose computed tomography (LDCT) screening, and to analyze the influencing factors. Methods: This retrospective study analyzed the CT images of the participants who underwent at least two chest LDCT scanning from March 2009 to December 2015 in National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. The inclusion criteria was the nodule diameter ≥6 mm; the volume growth was defined as ≥20%. Fifty-one pulmonary nodules (PNs) were selected among 51 enrolled participants (26 men and 25 women). According to characteristic of nodule and risk stratification of participant, the nodules were classified into different groups (10 non-solid nodules, 17 part-solid nodules and 24 solid nodules; 14 PNs in high-risk group, 12 PNs in moderate-risk group and 25 PNs in low-risk group). The Lung-VCAR software was used to measure the diameter and volume of the PNs, and all nodules were calculated for the volume doubling time (VDT) and mass doubling time (MDT). Results: Among the 51 PNs, the diameter of 33 nodules increased more than 1.5 mm while 18 nodules increased less than 1.5 mm. The median VDT of part-solid nodules was 364 days, which was shorter than that of non-solid nodules and solid nodules (761 and 819 days, respectively), the differences were statistically significant (both P<0.05). The median MDT of part-solid nodules was 351 days, which was lower than that of non-solid nodules and solid nodules (772 days and 840 days, respectively). The difference was statistically significant (P<0.05). The median VDT and MDT of the pulmonary nodules in the high-risk group were 181 days and 256 days, respectively, which were lower than those in the low risk group (1 037 days and 1 035 days, respectively). VDT has good correlation with MDT (r=0.909, P<0.001). Conclusions: Both the characteristic of PNs and the risk status of the participants could affect the growth of nodules in LDCT screening. The part-solid nodules and high-risk group nodules grew relatively faster, which should be closely focused on. Compared with the two-dimensional diameter, the three-dimensional quantitative indicators (VDT and MDT) were more sensitive for nodule growth. The mass changes of part-solid nodules were earlier than that of volume.

Nitrogen acquisition, net production and allometry of Alnus fruticosa at a young moraine in Koryto Glacier Valley, Kamchatka, Russian Far East.

Alders (Alnus spp.) often dominate at nutrient-poor sites by symbiotic relations with atmospheric nitrogen-fixing bacteria. However, little is known about quantitative relationships between root nodule as a nitrogen acquisition organ and leaf as a carbon acquisition organ. To examine carbon allocation, nitrogen acquisition and net production in nutrient-poor conditions, we examined allocation patterns among organs of shrub Alnus fruticosa at a young 80-year-old moraine in Kamchatka. Slopes of double-log allometric equations were significantly smaller than 1.0 for the root mass, leaf mass and root nodule mass against stem mass, and for the root nodule mass against root mass, indicating that smaller individuals invested disproportionally more biomass into resource-acquiring leaf and root tissues than to supportive tissues compared to older individuals. The slope of allometric equation of root depth against stem height was 0.542, indicating that smaller/younger individuals allocate disproportionally more biomass into root length growth than stem height growth. On the contrary, the root nodule mass isometrically scaled to leaf mass. The whole-plant nitrogen content also isometrically scaled to root nodule mass, indicating that a certain ratio of nitrogen acquisition depended on root nodules, irrespective of plant size. Although the net production per plant increased with the increase in stem mass, the slope of the double-log regression was smaller than 1.0. On the contrary, the net production per plant isometrically increased with leaf mass, root nodule mass and leaf nitrogen content per plant. Since the leaf mass isometrically scaled to root nodule mass, growth of each individual occurred at the leaves and root nodules in a coordinated manner. It is suggested that their isometric increase contributes to the increase in net production per plant for A. fruticosa in nutrient-poor conditions.

CT features differentiating pre- and minimally invasive from invasive adenocarcinoma appearing as mixed ground-glass nodules: mass is a potential imaging biomarker

To investigate the differential diagnosis value of preoperative computed tomography (CT) features between pre/minimally invasive and invasive adenocarcinoma in pulmonary mixed ground glass nodules (mGGNs). The histopathological data and CT images of 146 mGGNs in 141 patients were reviewed retrospectively. Logistic regression analysis and receiver operating characteristic (ROC) curve analysis were performed to identify the CT features differentiating between pre/minimally invasive and invasive adenocarcinoma and to evaluate their accuracy. In univariate analysis, there were significant differences (p<0.05) in the nodule diameter, volume, density, mass, solid portion volume, shape, margin, air bronchogram, and pleural retraction between pre/minimally invasive and invasive adenocarcinoma. Multivariate logistic regression analyses revealed that nodule mass and volume were statistically significant independent differentiators. ROC curve analysis was performed to evaluate the differentiators. According to the corresponding ROC curve, the optimal cut-off mass to differentiate pre/minimally invasive adenocarcinoma from invasive adenocarcinoma was 254.87 mg, with a sensitivity of 84.52%, a specificity of 88.71%, and an accuracy of 86.30%. Compared with the area under the ROC curve (AUC) for mass, volume, and diameter, the differential diagnosis value of mass was higher than those of volume and diameter. Nodule mass and volume were significant differentiators of pre/minimally invasive adenocarcinoma from invasive adenocarcinoma in mGGN, and mass had a higher differential diagnosis value.

Glyphosate effects on symbiotic nitrogen fixation in glyphosate-resistant soybean

Most soybean (Glycine max L. Merr.) cultivars grown in the U.S. are Roundup Ready®, genetically modified for resistance to the herbicide glyphosate. The objectives of this study were to examine the impacts of glyphosate applications on symbiotic N2 fixation in glyphosate-resistant (GR) soybean and to evaluate the responses of rhizobial isolates and nifH gene abundance in the rhizosphere soil to glyphosate. In two repeated greenhouse experiments, GR soybean received foliar applications of glyphosate once or twice during the study period; the untreated GR and near-isogenic conventional cultivar served as controls. Plants were harvested twice, two days after each glyphosate application. In addition to plant growth parameters, the nitrogenase activity of root nodules and the abundance of the nifH gene in the rhizosphere were determined using the acetylene reduction assay and quantitative PCR, respectively. Glyphosate-treated GR soybean had lower chlorophyll content, root mass, nodule mass, total plant N, and nitrogenase activity than the untreated conventional cultivar, especially for the second harvest. Without glyphosate application, few differences were observed between the two cultivars. Glyphosate inhibited the growth of rhizobia isolated from root nodules; however, the nifH gene abundance in the rhizosphere was not different among the treatments. Glyphosate appeared to exert stress to the GR soybean cultivar used in this study. Further research is needed to verify the greenhouse experiment findings and possible yield effects under field conditions.

Poly-β-hydroxybutyrate (PHB) biosynthesis, tricarboxylic acid activity and PHB content in chickpea (Cicer arietinum L.) root nodule

An experiment was conducted to assess the relationship between poly-β-hydroxybutyrate (PHB) biosynthesis and tricarboxylic acid (TCA) activity in desi and kabuli chickpea (Cicer arietinum L.) genotypes. The specific activities of enzymes of PHB metabolism viz., β-ketothiolase (PHB-A), acetoacetyl coenzyme A reductase (PHB-B) and PHB synthase (PHB-C), and those of tricarboxylic acid cycle (citrate synthase (CS) and malate dehydrogenase (MDH) under symbiosis were measured in bacteroids and compared with the PHB accumulation in the nodule and the root. The significant positive correlation was observed between shoot and nodule mass and PHB-A, PHB-B, and PHB-C activities. However, nodule and shoot weights were not significantly correlated with PHB content either in the roots or nodules. The same was true for PHB levels and citrate synthase activity. MDH activity showed a significant negative correlation with nodule PHB. A marked variation and an age dependant increase in malate dehydrogenase activity were measured. A higher capacity for malate oxidation by an increased MDH is likely alter the balance between malate decarboxylation and oxidation, resulting in a higher steady-state concentration of oxaloacetate and that may favor the utilization of acetyl-CoA in the TCA cycle rather than for the synthesis of PHB.

English

The objective of this study was to evaluate the symbiotic efficiency of rhizobia under field conditions for peas (Pisum sativum L.). Ten treatments were evaluated and divided into eight strains of rhizobia and two uninoculated strains as controls (with and without the addition of mineral N). The variables analyzed were: Nodulation, dry mass of the aerial part, total N of the aerial section, pea production and symbiotic efficiency. The inoculated rhizobia strains had effects on the number and mass of nodules, accumulated N in the aerial part and pea grains production. The strain EEL7802 presented the highest symbiotic efficiency for peas. The inoculation may allow cost reduction due to the equivalence with nitrogen fertilization. Studies in other soil types are needed to confirm the efficiency of this strain. &nbsp; Key words: Pisum sativum, Rhizobium leguminosarum, nodulation, nitrogen biological fixation.

Nitrogen fixation, plant growth and yield enhancements by diazotrophic growth-promoting bacteria in two cultivars of chickpea ( Cicer arietinum L.)

A total of 11 rhizobia-like-bacteria, isolated from the nodules of chickpea, were characterized for nitrogen fixation potential and growth promoting ability. All the isolates nodulated chickpea, amplified nifH gene and fixed nitrogen but, four isolates (ICKM-9, ICKM-15, ICS-31 and ICS-32) were found to fix nitrogen more than 4.0 nmoles of ethylene g−1 fresh weight of nodules h−1. Under field conditions, seeds of chickpea varieties ICCV 2 and JG 11, when treated with the bacteria, enhanced the nodule number (up to 46% and 46%), nodule mass (up to 76% and 50%), shoot mass (up to 21% and 42%) and grain yield (up to 27% and 25%), respectively, over the un-inoculated control. At the harvest, organic carbon (up to 7% and 24%), total nitrogen (up to 11% and 19%) and available phosphorous (up to 14% and 29%) were found enhanced, respectively, in the rhizosphere of ICCV-2 and JG-11 treated with bacteria over the un-inoculated control. All the isolates produced plant growth-promoting traits including indole acetic acid, β-1,3-glucanase, hydro cyanic acid (except ICKM-17 and ICS-31) and siderophore (except ICS-31). The 16 S rDNA gene sequences of bacterial isolates of ICKM-1, ICKM-4, ICKM-7, ICKM-9, ICKM-12, ICKM-14, ICKM-15, ICKM-17, ICS-30, ICS-31 and ICS-32 showed maximum identity with Pantoea dispersa, Chryseobacterium indologenes, Pseudomonas geniculata, Stenotrophomonas pavanii, P. geniculata, P. geniculata, Stenotrophomonas maltophilia, Chryseobacterium sp., P. geniculata, Chryseobacterium indologenes and Stenotrophomonas acidaminiphila, respectively. This study indicates nodule-associated bacteria could be a valuable pool for improving nitrogen fixation and crop yields in chickpea.