Bean Nodules Research Articles

English

Most of the soils are N and P-deficient and require high applications of chemical fertilizers to ensure optimal crop production. However, this practice poses in most cases serious environmental issues. In recent years, inoculation with beneficial bacteria has emerged as a safe and sustainable alternative to chemical fertilizers. In this context, we investigated the effect of two symbiotic Agrobacterium radiobacter strains (LMR670 and LMR676) and two plant growth-promoting rhizobacteria Bacillus sp. (M131) and Enterobacter sp. (P1S6), as single or combined inoculants, on common bean growth and yield under N and P-deficient conditions. In a first trial, Agrobacterium strains’ symbiotic efficiency with common bean was evaluated in a low phosphorus and nitrogen soil under greenhouse conditions. Strain LMR670 recorded the highest nodules number (53 nodules per plant) and shoot dry weight (0.553 g plant-1). This strain was then used in combination with the PGP rhizobacteria in a common bean co-inoculation assay under sufficient and deficient P levels (80 kg ha-1of P and No P added). Single inoculation with LMR670 recorded the highest shoot dry weight (82% increase compared to non-fertilized control) compared to combined inoculants (46-47% increase). To corroborate the obtained results, a field experiment was conducted using the same treatments. LMR670 as a single inoculant or mixed with M131 was consistently effective leading to common bean yields comparable to N and P fertilized plants (13.07 t ha-1 and 12.35 t ha-1 respectively). In addition, single inoculation with the multi-PGP strain M131 showed positive effects on all common bean growth parameters and yield value (14 t ha-1); exceeding even N and P fertilized control plants. These results suggest that the strains LMR670 and M131 can be used, in a single or combined inoculation, as effective biological fertilizers for common bean cultivation to replace phosphorus and nitrogen fertilizers. Globally our results highlight the potential of native phytobeneficial strains for successful nodulation, growth and yield of common bean under N and P-deficient conditions.

Evaluation of Symbiotic Association between Various Rhizobia, Capable of Producing Plant-Growth-Promoting Biomolecules, and Mung Bean for Sustainable Production

To feed the increased world population, sustainability in the production of crops is the need of the hour, and exploration of an effective symbiotic association of rhizobia with legumes may serve the purpose. A laboratory-scale experiment was conducted to evaluate the symbiotic effectiveness of twenty wild rhizobial isolates (MR1–MR20) on the growth, physiology, biochemical traits, and nodulation of mung bean to predict better crop production with higher yields. Rhizobial strain MR4 resulted in a 52% increase in shoot length and 49% increase in shoot fresh mass, while MR5 showed a 30% increase in root length, with 67% and 65% improvement in root fresh mass by MR4 and MR5, respectively, compared to uninoculated control. Total dry matter of mung bean was enhanced by 73% and 68% with strains MR4 and MR5 followed by MR1 and MR3 with 60% increase in comparison to control. Rhizobial strain MR5 produced a maximum (25 nodules) number of nodules followed by MR4, MR3, and MR1 which produced 24, 23, and 21 nodules per plant. Results related to physiological parameters showed the best performance of MR4 and MR5 compared to control among all treatments. MR4 strain helped the plants to produce the lowest values of total soluble protein (TSP) (38% less), flavonoids contents (44% less), and malondialdehyde (MDA) contents (52% less) among all treatments compared to uninoculated control plants. Total phenolics contents of mung bean plants also showed significantly variable results, with the highest value of 54.79 mg kg−1 in MR4 inoculated plants, followed by MR5 and MR1 inoculated plants, while the minimum concentration of total phenolics was recorded in uninoculated control plants of mung bean. Based on the results of growth promotion, nodulation ability, and physiological and biochemical characteristics recorded in an experimental trial conducted under gnotobiotic conditions, four rhizobial isolates (MR1, MR3, MR4, and MR5) were selected using cluster and principal component analysis. Selected strains were also tested for a variety of plant-growth-promoting molecules to develop a correlation with the results of plant-based parameters, and it was concluded that these wild rhizobial strains were effective in improving sustainable production of mung bean.

Plant-microbe-microbe interactions influence the faba bean nodule colonization by diverse endophytic bacteria.

Legume root nodules harbor rhizobia and other non-nodulating endophytes known as nodule-associated bacteria (NAB) whose role in the legume symbiosis is still unknown. We analysed the genetic diversity of 34 NAB isolates obtained from the root nodules of faba bean grown under various soil conditions in Egypt using 16S rRNA and concatenated sequences of three housekeeping genes. All isolates were identified as members of the family Enterobacteriaceae belonging to the genera Klebsiella, Enterobacter and Raoultella. We identified nine enterobacterial genospecies, most of which have not been previously reported as NAB. All isolated strains harbored nifH gene sequences and most of them possessed plant growth-promoting (PGP) traits. Upon co-inoculation with an N2 fixing rhizobium (Rlv NGB-FR128), two strains (Enterobacter sichanensis NGB-FR97 and Klebsiella variicola NGB-FR116) significantly increased nodulation, growth and N-uptake of faba bean plants over the single treatments or the uninoculated control. The presence of these enterobacteria in nodules was significantly affected by the host plant genotype, symbiotic rhizobium genotype and endophyte genotype, indicating that the nodule colonization process is regulated by plant-microbe-microbe interactions. This study emphasizes the importance of nodule-associated enterobacteria and suggests their potential role in improving the effectiveness of rhizobial inoculants.

Isolation and Characterization of High-Efficiency Rhizobia From Western Kenya Nodulating With Common Bean.

Common bean is one of the primary protein sources in third-world countries. They form nodules with nitrogen-fixing rhizobia, which have to be adapted to the local soils. Commercial rhizobial strains such as Rhizobium tropici CIAT899 are often used in agriculture. However, this strain failed to significantly increase the common bean yield in many places, including Kenya, due to the local soils’ low pH. We isolated two indigenous rhizobial strains from the nodules of common bean from two fields in Western Kenya that have never been exposed to commercial inocula. We then determined their ability to fix nitrogen in common beans, solubilize phosphorus, and produce indole acetic acid. In greenhouse experiments, common bean plants inoculated with two isolates, B3 and S2 in sterile vermiculite, performed better than those inoculated with CIAT899 or plants grown with nitrogen fertilizer alone. In contrast to CIAT899, both isolates grew in the media with pH 4.8. Furthermore, isolate B3 had higher phosphate solubilization ability and produced more indole acetic acid than the other two rhizobia. Genome analyses revealed that B3 and S2 are different strains of Rhizobium phaseoli. We recommend fieldwork studies in Kenyan soils to test the efficacy of the two isolates in the natural environment in an effort to produce inoculants specific for these soils.

Variation in winged bean (Psophocarpus tetragonolobus) growth parameters, seed yield, nodulation, and nitrogen fixation

Abstract. Adegboyega TT, Abberton MT, Abdelgadir AH, Mahamadi D, Olaniyi OA, Ofodile S, Babalola OO. 2021. Variation in winged bean (Psophocarpus tetragonolobus) growth parameters, seed yield, nodulation, and nitrogen fixation. Asian J Agric 5: 61-71. Underutilized legumes are widely distributed in tropical agriculture and associated with low yield. Thus they have not really been fully explored due to lack of research investment, breeding programs targeting crop improvement, marketing, and low awareness of nutritional benefits. This study was conducted to determine the variation in growth parameters, seed yield, nodulation, and nitrogen fixation in winged bean (Psophocarpus tetragonolobus) germplasms. High genotypic and phenotypic coefficients of variances were observed in traits evaluated. The combined analysis of variance for five variables of 25-winged bean accessions showed that replication by year interaction was statistically significant (p ? 0.0001) for nodule parameters and dry shoot weight while it was not significant (p = > 0.05) for dry root weight, and total biomass. Significant variations (p = ? 0.05) were observed among the accessions on some growth parameters. The genetic variability of winged beans could be carefully exploited to provide higher grain yield, as well as other economic and important traits to boost food security and conservation of the plant genetic materials.

Diversity and biotechnological potential of rhizobia isolated from lima bean nodules collected at a semiarid region

AbstractLima bean (Phaseolus lunatusL.) is the second most important species of thePhaseolusgenus worldwide. In Brazil, it is grown primarily in the semiarid Northeast region. Although lima bean establishes symbiosis with N2‐fixing bacteria (rhizobia), there is not yet a recommended inoculant. The aim of this study was to phenotypically and genotypically characterize rhizobia strains isolated from root nodules of lima bean collected in a Northeast region, and to evaluate their efficiency in supplying N nutrition to the crop under axenic conditions and in a Humic Rhodic Hapludox with and without correction of acidity. The symbiotic efficiencies were evaluated in a greenhouse under axenic conditions and, afterward, in pots with nonautoclaved soil with and without liming. Treatments consisted of the strains under evaluation, controls without inoculation (with low or high concentration or without mineral N), and a strain efficient for the crop. In all, 66 strains were isolated from the root nodules with predominance of strains belonging to theBradyrhizobiumgenus. Liming brought about increases in lima bean development as it interacted with some strains. Six strains of theBradyrhizobiumgenus, belonging to groups of type strains that includeB. elkaniiandB. japonicum, stood out for their biotechnological potential as inoculants for lima bean, and they should be tested in the field with the aim of validating their recommendation as inoculants for that crop.

Role of Elemental Sulfur and Copper Oxychloride against Damping- Off Disease of Faba Bean Caused by Fusarium solani.

The efficacy of the organic fungicides elemental sulfur (S) and copper oxychloride (Cu) as well as a soil treatment Rhizobium leguminosarum were evaluated under laboratory, plastic houses and the field conditions, to control faba bean damping-off disease caused by Fusarium solani. Under laboratory conditions, the fungicides produced reduced mycelial growth of F. solani compared to R. leguminosarum as their effect was weak in reducing its growth. Under plastic houses and/or field conditions during (2015/2016 and 2016/2017) growing seasons, the faba bean plant was treated with the organic fungicides elemental sulfur at 500 ppm, copper oxychloride at 500 ppm (as a soil treatment) and / or seed packaging with R. leguminosarum, individually or combined. All treatments reduced the pre- and post-emergence damping-off, as well as increased the remaining plants, fresh & dry weight shoots and Nodulation of faba bean compared to the comparison treatment. In addition, under field condition, it caused a significant increase in the yield components for example (the number of pods per plant and total yield per Fed of both seasons. The combination of R. leguminosarum and the fungicide elemental sulfur was the best of these treatments compared to the other treatments.

Interplay of Rhizobial Inoculants and Fungicide on Chickpea (Cicer Arietinum) and Faba Bean (Vicia Faba L.) Nodulation and Seed Yield in Central Ethiopian Highland

Field and green house experiments were conducted on faba bean and chickpea during 2016-2017 to investigate the effect of fungicides and rhizobial inoculant interaction on nodulation and biomass accumulation of chickpea under Vertisol condition and (ii) faba bean under Nitisol condition. Chickpea seed was treated with Apron Star, Imidalm and both, and co-dressed with EAL-029 rhizobia simultaneously or a week later. Likewise, in one of the two sets, faba bean seed was treated with Apron Star and simultaneously dressed with FB-1017 or FB-1035 rhizobial strain. The other set had the same strains as pre inoculant and sprayed with Mancozeb at 30th day after sowing. Sole inoculants and N (faba bean) were used as check. The application rates of Apron Star, Imidalm, and inoculant were 2.5, 0.75, and 3.12 g kg-1 of seed while for Mancozeb is 2.5kg/ha. All treatments were replicated 4x and laid in RCB design. The result generally depicted that Apron Star application was compatible to EAL-029 rhizobia on chickpea. Staggered dressing of Apron Star and EAL-029 had better chickpea shoot dry matter accumulation. With regards to faba bean, co-dressing of Apron Star with FB-1017 or FB-1035 produced the highest nodulation. This confirmed the synergy of Apron Star with FB-1017 on Nitisol of central high land of Ethiopia. Moreover, spraying mancozeb on the 30th day after sowing to FB-1017 or FB-1035 preinoculated faba bean plant showed enhanced seed yield on Nitisol.

Characterization and nodulation capacity of native bacteria isolated from mung bean nodules used as a trap plant in Brazilian tropical soils

Mung bean [Vigna radiata (L.) Wilczek] is a legume of Asian origin with great importance worldwide, particularly in developing countries. It is known for its promiscuous association with soil rhizobia, which provides nitrogen via biological nitrogen fixation (BNF). From the prospective of increasing productivity, efforts are ongoing to identify bacteria that form more efficient symbiotic associations with mung bean. In this regard, we evaluated the nodulation of two mung bean cultivars with native rhizobia from 10 samples of tropical Brazilian soil and performed the isolation of bacterial strains present in the nodules. These isolates were characterized morphologically, and grouped based on sequencing of the 16S rRNA gene. The isolates were also evaluated for nodulation capacity in mung bean and BNF efficiency. We found differences in mung bean plant development depending on the soil for both cultivars. In general, the plants cultivated in soil samples from the Atlantic Forest region showed greater nodulation and shoot dry weight compared to the Brazilian Cerrado (tropical savanna). On the basis of an evaluation of nodulation by native rhizobia, we isolated 101 bacterial strains, which were classified according to 16S rRNA gene into nine genera: Bradyrhizobium (66), Rhizobium (19), Mesorhizobium (4), Ensifer (3), Leifsonia (3), Bacillus (3), Agrobacterium (1), Mycolicibacterium (1), and Kaistia (1). Bradyrhizobium was the most abundant genus, and its isolates formed 12 phylogenetic groups. Inoculation assessments revealed that only Bradyrhizobium isolates induced nodule formation in mung bean, with the BNF efficiency of isolates differing depending on phylogenetic group and soil of origin. Plants inoculated with isolates grouped with Bradyrhizobium yuanmingense B071 were found to show greater increases in shoot dry weight. Considering the soil origin, we observed that plants inoculated with Bradyrhizobium isolated from Mato Grosso state soil samples showed smaller increments in nodulation and shoot dry weight. These results suggest that the Bradyrhizobium is the predominant symbiont in the nodules of mung bean grown in Brazilian tropical soils, and its isolates have the potential for mung bean inoculation, especially when grown in soils that provide low nodulation by native rhizobia.

Assessment of Consortia Inoculation Effects on the Agronomical Performance of the Common Bean

ABSTRACT The massive use of inputs is often applied in common bean for nitrogen (N) supply, better plant development, and to prevent plant disease. Instead, the co-inoculation of Rhizobium, Azospirillum and Trichoderma may play the same role; however, its effects are unknown in common bean. This work aimed to evaluate the effects of co-inoculating three microorganisms on the development, nodulation and grain yield (GY) of a common bean. The experiments were carried out on a randomized block design with four replicates. The treatments were NI: not inoculated; Rt: inoculated with Rhizobium tropici; Rt+Ab: inoculated with Rt and Azospirillum brasilense; Rt+Ab+Ta: inoculated with Rt, Ab and Trichoderma asperellum; Nf120: 120 kg ha−1 of N. In the inoculated treatments, the seeds were treated with Rt inoculant and with Ta inoculant before sowing, using a dose of 10 g of each inoculant kg−1 of seed. The inoculant containing the Ab was sprayed out in a dose of 300 mL ha−1 at the V2/V3 phenological stage. Evaluations were performed for the number of nodules (NN), nodule dry weight (NDW), root dry weight (RDW), shoot dry weight (SDW), pod number (PN), grain number (GN) and GY. NN and NDW were higher in NI and Rt treatments. The Rt+Ab treatment resulted in higher SDW, whereas the same treatment and Rt+Ab+Ta provided higher RDW and SDW, resulting in values similar to those of the Nf120 treatment. Innoculation with rhizobia (Rt) provided PN and GN equivalent to those of the Nf120 treatment. The inoculation (Rt) and co-iconulation (Rt+Ab) resulted on GY of 2946.27 and 2892.42 kg ha−1, respectively, surpassing the Nf120 treatment, which was 2741.91 kg ha−1. These results indicate that Rt inoculation and Rt+Ab co-inoculation can be alternatives to the substitution of nitrogen fertilizers, guaranteeing high GY levels in common bean.

Effects of Rhizobium tropici azide-resistant mutants on growth, nitrogen nutrition and nodulation of common bean (Phaseolus vulgaris L.)

Inoculation with Rhizobium tropici and Rhizobium freirei can partially supply the nitrogen demand required for normal development and high productivity of common bean (Phaseolus vulgaris L.). Here, a simple and low-cost approach was used to select R. tropici sodium azide-resistant mutants with improved efficiency as microsymbiont of common bean. We mutagenized R. tropici CIAT889 by treatment with methyl methanesulfonate (MMS) and selected azide-resistant mutants. Six mutants (AzR14, AzR15, AzR16, AzR17, AzR18, and AzR19) with varying levels of resistance were obtained and characterized for symbiotic traits and performance upon inoculation of common bean. Mutants grew and produced exopolysaccharides similar to the CIAT899 wildtype; however, swarming motility, biofilm, and auxin production were altered. About nodulation, shoot biomass, and nitrogen content, the performance of mutant strains was improved or similar to that of CIAT899. All mutants enhanced nodulation of common bean; furthermore, AzR14, AzR18, and AzR19 increased nodule biomass by 25%–36%. AzR18 and AzR19 increased shoot biomass by up to 13% compared to CIAT899, whereas AzR14, AzR15, AzR16, and AzR17 reduced biomass accumulation by 9%–19%. In addition, AzR18 and AzR19 showed higher motility or biofilm production than the other mutant strains, suggesting that these traits are involved in bacterial symbiotic effectiveness. Shoot N content do not differ between plants inoculated with the CIAT899 or mutant strains, although plants inoculated with AzR18, AzR19 and CIAT899 had increased the shoot N as compared to uninoculated plants grown at N-limiting conditions. Our results demonstrated the possibility to improve the performance of the R. tropici microsymbiont through induced mutagenesis followed by the selection of azide resistant mutants. This approach allowed to identify the AzR18 and AzR19 strains, which showed superior nodulation and symbiotic effectiveness than CIAT899 while providing equivalent amounts of N to the inoculated plants. We propose the AzR18 and AzR19 as promising candidates for developing new and more efficient inoculants for common bean, nevertheless further trials under field conditions are required to confirm their superior performance to the wild strain.

Effect of rhizobial inoculants on yield and yield components of faba bean (Vicia fabae L.) on vertisol of Wereillu District, South Wollo, Ethiopia

BackgroundNitrogen fixation by legumes like faba bean is a cheap way of fixing atmospheric nitrogen to plant available form. However, the inoculation of grain legumes with rhizobium bacteria are poorly researched in Amhara Region of Ethiopia.MethodsThus, a study to examine the effects of rhizobium leguminosarum (var vicae) strains on nodulation, growth, and yield of faba bean was conducted in Wereillu district of Amhara Region, Ethiopia during the rainy season of 2018. The treatments comprised of four levels of faba bean Rhizobium strains (un-inoculated, EAL-1018, EAL-1035 and EAL-17) arranged in a randomized complete block design with three replications. The collected data on yield and yield-related parameters were analyzed using Statistical Analysis System (Statistical Analysis System, version 9.1, SAS Institute Inc, Cary, 2003), version 9.1 and subjected to Duncan’s Multiple Range Test for mean separation when the analysis of variance was significant.ResultsThe result revealed that the effect of EAL-1018 brought significantly (P ≤ 0.05) higher difference on nodule number, nodulation volume, nodule dry weight, biomass yield and grain yield compared to the control. Faba bean strain, EAL-1018 gave 45.6, 27 and 11.6% grain yield advantage over the control, EAL1017 and EAL 1035 respectively.ConclusionBiologically as well as Economically EAL 1018 brought the maximum yield and net benefit (47020.7) compared to the other treatments. Hence, EAL-1018 is recommended for the study area and similar agro—ecologies.

CaCl2seed priming stimulate nodulation and oleosome lipids formation in the root nodules of cadmium-treated faba bean plants

This study was designed to highlight the impact of calcium chloride (CaCl2) seed priming on faba bean nodulation and root nodule oleosomes under cadmium stress. In the un-primed plants, high Cd exposure (50 μM) led to a decrease in nodule number and dry weight by 63% and 76% respectively as compared to control. Furthermore, metal supply resulted in a decrease (by 46%) in lipid content and the level of saturated fatty acids of oleosomes. However, CaCl2 seed priming improved nodule number by 23% and 20% and dry weight by 34% and 7% at 0 and 50 μM Cd respectively, compared to the control. Moreover, results showed that CaCl2 alleviated adverse effects of Cd on oleosome lipid content and fatty acid composition. Overall, CaCl2 seed priming was effective to alleviate the detrimental effects of Cd on some physiological and biochemical characteristics of faba bean root-nodule.

Legume-rhizobium specificity effect on nodulation, biomass production and partitioning of faba bean (Vicia faba L.)

Greenhouse and multi-location experiments were conducted for two consecutive years to investigate the effects of rhizobium on nodulation, biomass production and partitioning of faba bean. Split-plot in randomized complete block design was used for field experiments. Treatments consisted of six rhizobium strains and three faba bean varieties. Peat carrier-based inoculant of each strain was applied at the rate of 10 g kg−1 seed. Non-inoculated plants without N fertilizer and with N fertilizer served as –N and + N controls, respectively. Data on nodulation, shoot dry weight and root dry weight were collected and analyzed. Inoculation of rhizobium significantly increased nodulation of faba bean under greenhouse and field conditions. Location x strain x variety interaction had significant effects on nodulation, dry matter production and partitioning. Rhizobium inoculation increased nodulation, shoot and root dry weights of faba bean across locations. For example, inoculation with rhizobium strains NSFBR-15 and NSFBR-12 to variety Moti resulted in 206.9 and 99.3% shoot dry weight increase at Abala Gase and Hankomolicha, respectively and 133.3 and 70.7% root dry weight increase on the same variety at the same sites, respectively. Nodulation and biomass production depend on the compatibility between faba bean genotype and rhizobium strain and its interaction with soil bio-physical conditions.

Effect of Rhizobium inoculant, Nitrogen Starter and Cobalt on Stimulation of Nodulation, N Fixation and Performance of Faba Bean (Vicia faba L.) Grown under Salinity Stress

In the modern agriculture systems, there is a general tendency to reduce the amounts of mineral nitrogen inputs and maximize their use efficiency to minimize environmental pollution and its hazards on public human health. It is well known that cobalt is a necessary trace element to leguminous crops and bacterial communities responsible for biological nitrogen fixation (BNF). So, two field trials were performed in a split-split-plot design with three replicates during two-successive winter seasons of 2019/2020 and 2020/2021 as the sake of studying the influence of Rhizobium inoculant, nitrogen application rates [100, 75 and 50% of nitrogen recommended dose (NRD) as starter, equivalent to 20, 15 and 10kg N fed-1, respectively] and cobalt supplementation (seeds soaking and foliar application as combined method) at different concentrations of cobalt (0.0, 8.0 and 12.0 mg cobalt L-1) on nodulation, nitrogenase activity and performance of faba bean plants grown on saline clay soil. Findings of this study showed that plants inoculated prior to sowing with the strain of Rhizobium at rate of 10 g inoculant per 1.0 kg seeds under N fertilization at rate of 15 kg N fed-1 with cobalt treatment at rates of 8.0 and 12.0 mg cobalt L-1 realized better results than that fertilized with ammonium sulphate at rate of 20 kg N fed-1 without both Rhizobium inoculation and cobalt treatment. Generally, cobalt treatments improved nodulation, nitrogenase activity and stimulated nodulation parameters, thus enhancing all studied growth criteria, green yield and its components of faba bean plants grown under salinity stress.

Bradyrhizobium as the Only Rhizobial Inhabitant of Mung Bean (Vigna radiata) Nodules in Tropical Soils: A Strategy Based on Microbiome for Improving Biological Nitrogen Fixation Using Bio-Products.

The mung bean has a great potential under tropical conditions given its high content of grain protein. Additionally, its ability to benefit from biological nitrogen fixation (BNF) through association with native rhizobia inhabiting nodule microbiome provides most of the nitrogen independence on fertilizers. Soil microbial communities which are influenced by biogeographical factors and soil properties, represent a source of rhizobacteria capable of stimulating plant growth. The objective of this study is to support selection of beneficial bacteria that form positive interactions with mung bean plants cultivated in tropical soils, as part of a seed inoculation program for increasing grain yield based on the BNF and other mechanisms. Two mung bean genotypes (Camaleão and Esmeralda) were cultivated in 10 soil samples. Nodule microbiome was characterized by next-generation sequencing using Illumina MiSeq 16S rRNA. More than 99% of nodule sequences showed similarity with Bradyrhizobium genus, the only rhizobial present in nodules in our study. Higher bacterial diversity of soil samples collected in agribusiness areas (MW_MT-I, II or III) was associated with Esmeralda genotype, while an organic agroecosystem soil sample (SE_RJ-V) showed the highest bacterial diversity independent of genotype. Furthermore, OTUs close to Bradyrhizobium elkanii have dominated in all soil samples, except in the sample from the organic agroecosystem, where just B. japonicum was present. Bacterial community of mung bean nodules is mainly influenced by soil pH, K, Ca, and P. Besides a difference on nodule colonization by OTU sequences close to the Pseudomonas genus regarding the two genotypes was detected too. Although representing a small rate, around 0.1% of the total, Pseudomonas OTUs were only retrieved from nodules of Esmeralda genotype, suggesting a different trait regarding specificity between macro- and micro-symbionts. The microbiome analysis will guide the next steps in the development of an inoculant for mung bean aiming to promote plant growth and grain yield, composed either by an efficient Bradyrhizobium strain on its own or co-inoculated with a Pseudomonas strain. Considering the results achieved, the assessment of microbial ecology parameters is a potent coadjuvant capable to accelerate the inoculant development process and to improve the benefits to the crop by soil microorganisms.

Isolation and characterization of rhizobium strains from root nodules of faba bean (Vicia faba L.)

Isolation and characterization of rhizobium strains from root nodules of faba bean (Vicia faba L.)

Agroecological modeling of nitrogen and carbon transfers between decomposer micro-organisms, plant symbionts, soil and atmosphere in an intercropping system

The modeling of continuous transfers of carbon (C) and nitrogen (N) previously published in the literature has paid little attention to the functional role of micro-organisms. In general, only monoculture systems have been modeled. Furthermore, there have been few experiments under field conditions at farm scale, where clear evidence for the benefits of intercropping is lacking. This work focus on mechanistic modeling approaches based on the ecological functioning of the microbial biomass, to quantify the daily exchange of C and N between plant organs, micro-organisms, rhizobial symbionts, soil compartments and the atmosphere in an arable intercropping system. The MOMOS model was validated on C and N data collected from a common bean (Phaseolus vulgaris L. cv. El Djadida) and maize (Zea mays L. cv. Filou) intercropping system. The experiment was performed at two field sites that were chosen with farmers to represent both high and low soil P availability. The results show that all C and N exchanges were successfully predicted at 5% significance and that they depend on the phenological stage, especially the flowering stage. Increased C allocation from photosynthesis to roots contributed to increasing both grain yield and N grain for intercropped maize. C and N stocks in the common bean nodules were lower in intercropping than in monocultures, and this is associated with the decrease of total atmospheric nitrogen (N2) fixation by intercropped common beans, in particular with a high soil P. However, the rate of N2 fixation was higher in the intercrops than in the monoculture when the soil is P-deficient. Micro-organisms were responsible for most of the C losses from the soil to the atmosphere but intercropping significantly reduced the C losses by improving micro-organism C use efficiency. These results uncover the strong link between N and C stocks, confirming the robustness of the newly formulated MOMOS equations that are validated in this paper. This agroecological modeling experiment demonstrated the functional role of microbial biomass, in both the growth of the intercrops crop and their symbiosis, improving the prediction of the daily C and N flows between plant organs, soil compartments and the atmosphere.

Alleviating the deleterious effects of soil salinity and alkalinity on faba bean (Vicia faba L.) production using Rhizobium/Agrobacterium inoculants

ABSTRACT The effectiveness of Rhizobium inoculation is largely determined by soil properties. In this study, the symbiotic efficiency of 17 Rhizobium/Agrobacterium local strains was screened in greenhouse experiments. Subsequently, the combined effects of selected five rhizobial strains plus a starting N-dose (48 kg N ha−1) on nodulation and yield of faba bean were evaluated in two-year field trials. The field experiments were conducted in multiple locations which represent fertile, alkaline-calcareous, and salt-affected soils. Regardless of soil type, rhizobial inoculation overwhelmingly improved the nodulation of faba beans compared to the non-inoculated control and N-fertilized (48 and 96 kg N ha−1) treatments. In all of the sites, inoculated faba beans, with at least two strains, produced grain yield and grain N yield significantly greater, or comparable to N-fertilized (96 kg N ha−1) treatment. The maximum response of faba bean to inoculation was identified in the salt-affected soil, whereas faba bean inoculated with Rlv strain NGB-FR 126 showed significant increases in the averages of grain yield (50%) and grain N-yield (56%) compared to N-fertilized (96 kg N ha−1) treatment, over the two cropping seasons. Besides enhancing nodulation, application of rhizobial inoculants effectively improved production and plant response in alkaline-calcareous and salt-affected soil conditions.

Phosphorus use efficiency, yield and nodulation of mung bean (Vigna radiata L.) as influenced by the rate of phosphorus and Rhizobium strains inoculation in Metema district, Ethiopia

Mung bean (Vigna radiata L.), which is a recently introduced legume crop in Ethiopia particularly in Metema area, is considered as one of the useful cash crops known in the world. Hence, In order to get the potential benefit, it is indispensable to increase the production and productivity of the crop. Most Ethiopian soils including Metema area are deficient in nutrients, especially N and P. Application of NP fertilizers have significantly increased yields of crops. Besides, using suitable Rhizobium strains have crucial role in N2 fixation capabilities of legume crops. Therefore, this field experiment was conducted during 2018 cropping season to assess the effect of P and Rhizobium inoculant on mung bean production. The experiment consisted factorial combination of five levels of P (0, 10, 20, 30 and 40 kg ha−1) and two levels of inoculation (un-inoculated and seeds inoculated with Rhizobium strain MB-001). The treatments were laid out in randomized complete block design with three replications. The result revealed that the effect of inoculation have significant effect on all studied parameters except number of seed per pod, harvest index, straw P uptake, P physiological efficiency and P agro-physiological efficiency. Phosphorus rate have significant effect in all parameters except nodule effectiveness and P physiological efficiency. Based on partial budget analysis, application of 30 kg P ha−1 together with Rhizobium inoculation (10 g per kg of seed) were found optimum for mung bean (Rasa (N-26) variety) production in Metema area.