Rhizobium Inoculation Research Articles

Recent progress and potential future directions to enhance biological nitrogen fixation in faba bean (Vicia faba L.).

The necessity for sustainable agricultural practices has propelled a renewed interest in legumes such as faba bean (Vicia faba L.) as agents to help deliver increased diversity to cropped systems and provide an organic source of nitrogen (N). However, the increased cultivation of faba beans has proven recalcitrant worldwide as a result of low yields. So, it is hoped that increased and more stable yields would improve the commercial success of the crop and so the likelihood of cultivation. Enhancing biological N fixation (BNF) in faba beans holds promise not only to enhance and stabilize yields but also to increase residual N available to subsequent cereal crops grown on the same field. In this review, we cover recent progress in enhancing BNF in faba beans. Specifically, rhizobial inoculation and the optimization of fertilizer input and cropping systems have received the greatest attention in the literature. We also suggest directions for future research on the subject. In the short term, modification of crop management practices such as fertilizer and biochar input may offer the benefits of enhanced BNF. In the long term, natural variation in rhizobial strains and faba bean genotypes can be harnessed. Strategies must be optimized on a local scale to realize the greatest benefits. Future research must measure the most useful parameters and consider the economic cost of strategies alongside the advantages of enhanced BNF.

Dynamic modulation of nodulation factor receptor levels by phosphorylation-mediated functional switch of a RING-type E3 ligase during legume nodulation

The precise control of receptor levels is crucial for initiating cellular signaling transduction in response to specific ligands; however, such mechanisms regulating nodulation factor (NF) receptor (NFR)-mediated perception of NFs to establish symbiosis remain unclear. In this study, we unveil the pivotal role of the NFR-interacting RING-type E3 ligase 1 (NIRE1) in regulating NFR1/NFR5 homeostasis to optimize rhizobial infection and nodule development in Lotus japonicus. We demonstrated that NIRE1 has a dual function in this regulatory process. It associates with both NFR1 and NFR5, facilitating their degradation through K48-linked polyubiquitination before rhizobial inoculation. However, following rhizobial inoculation, NFR1 phosphorylates NIRE1 at a conserved residue, Tyr-109, inducing a functional switch in NIRE1, which enables NIRE1 to mediate K63-linked polyubiquitination, thereby stabilizing NFR1/NFR5 in infected root cells. The introduction of phospho-dead NIRE1Y109F leads to delayed nodule development, underscoring the significance of phosphorylation at Tyr-109 in orchestrating symbiotic processes. Conversely, expression of the phospho-mimic NIRE1Y109E results in the formation of spontaneous nodules in L. japonicus, further emphasizing the critical role of the phosphorylation-dependent functional switch in NIRE1. In summary, these findings uncover a fine-tuned symbiotic mechanism that a single E3 ligase could undergo a phosphorylation-dependent functional switch to dynamically and precisely regulate NF receptor protein levels.

Bio-priming Treatment with PGPB Strains in Cowpea Production Increases Grain Yield and Net Income

In the 21st century, the use of beneficial microorganisms as biological fertilizers has become a notable phenomenon, driven by the ongoing search for sustainable solutions due to environmental issues associated with synthetic fertilizer use. This study aimed to investigate the effect of bio-priming with plant growth-promoting bacteria (PGPB) strains comparing them with synthetic fertilizer and rhizobium inoculation in Siirt ecological conditions. The field experiment was laid out according to a completely randomized design with four replications in the arable land of Siirt University (Siirt, Türkiye) during the 2019 summer season. Three synthetic fertilizer doses as diammonium phosphate (SF1: 100 kg ha-1, SF2: 200 kg ha-1, SF3: 300 kg ha-1) and seven biological fertilizer treatments (B1: TV61C, B2: TV62C, B3: TV126C, B4: TV24C, B5: TV53D, BMIX: TV119E+TV126C, RZB: Bradyrhizobium sp.) were compared with control (no fertilization+hydro-priming) in the study. The research results indicated that 300 kg ha-1 DAP and PGPB consortia showed the best results on agronomic characteristics. However, particularly when applied in the form of a consortium, PGPB strains exhibited performance very close to synthetic fertilization. Moreover, it was determined that 300 kg ha-1 DAP and PGPB consortia increased grain yield over hydro-primed plants by 54.6% and 42.4%, while they provided a net income of $654 and $721.6, respectively. Thus, bio-priming with PGPB increased higher net income compared with synthetic fertilizer due to lower treatment costs. In conclusion, bio-priming with PGPB strains has the potential of useful, sustainable and cost-effective strategy in cowpea production.

Rhizobial-induced phosphatase GmPP2C61A positively regulates soybean nodulation.

Symbiotic nitrogen fixation (SNF) is crucial for legumes, providing them with the nitrogen necessary for plant growth and development. Nodulation is the first step in the establishment of SNF. However, the determinant genes in soybean nodulation and the understanding of the underlying molecular mechanisms governing nodulation are still limited. Herein, we identified a phosphatase, GmPP2C61A, which was specifically induced by rhizobia inoculation. Using transgenic hairy roots harboring GmPP2C61A::GUS, we showed that GmPP2C61A was mainly induced in epidermal cells following rhizobia inoculation. Functional analysis revealed that knockdown or knock-out of GmPP2C61A significantly reduced the number of nodules, while overexpression of GmPP2C61A promoted nodule formation. Additionally, GmPP2C61A protein was mainly localized in the cytoplasm and exhibited conserved phosphatase activity in vitro. Our findings suggest that phosphatase GmPP2C61A serves as a critical regulator in soybean nodulation, highlighting its potential significance in enhancing symbiotic nitrogen fixation.

Combination Effects of Sulfur Fertilizer and Rhizobium Inoculant on Photosynthesis Dynamics and Yield Components of Soybean

Sulfur (S) fertilization and rhizobium inoculation are important agronomic practices for improving soybean growth and yield. However, their combined effects on yield components and the resultant impacts on yield need further investigation. Our study aimed to verify the combined effects of S fertilizer and rhizobium inoculant on the yield components and seed yield of soybeans, as well as photosynthesis dynamics during the V5–R6 growth stages. A randomized block design incorporating two factors was employed for field experiments on soybean, involving the application of five rates of sulfur (0, 5.0, 9.8, 14.8, and 19.6 kg S ha−1) with rhizobium inoculation or without. A reduction of 50% in mineral fertilizer according to farmer practice (FP) was applied alongside different rates of sulfur for field experiments on soybeans. The findings indicated that the application of sulfur fertilization significantly enhanced soybean yield by increasing the number of grains per plant (NG) and the number of pods per plant (NP). Maximum grain yield was reached under treatment with an S rate of 19.6 kg S ha−1, which increased NG by 39% more than an S rate of 0 kg S ha−1. Correlation analysis indicated that higher photosynthesis was closely associated with increased yield components. This study demonstrated that applying S fertilizers could improve soybean production by combining the appropriate sulfur concentration and rhizobia inoculation.

Temporal dynamics of rhizosphere bacterial community in the Robinia pseudoacacia–Mesorhizobium loti symbiotic system for remediation of cadmium-contaminated soils

Rhizobia can be used to enhance the phytoremediation of cadmium-contaminated soils by legumes, and a symbiotic nitrogen-fixing system has been shown to reshape the structure of rhizosphere microbiota in a mining area. However, little is known about the temporal dynamics and possible roles of rhizosphere microbiota in rhizobia-enhanced phytoremediation. A rhizobox experiment was conducted using Robinia pseudoacacia alone or inoculated with Mesorhizobium loti HZ76 under greenhouse conditions. Rhizosphere bacterial communities were characterized over a 90-day period at three levels of cadmium (determined by the distance from the mining area; uncontaminated: 0.08 mg kg−1, contaminated: 0.39 and 1.72 mg kg−1). Rhizobial inoculation considerably improved the phytoremediation efficiency, such as increasing plant biomass and cadmium accumulation by approximately two times at 90 days after planting. The bacterial community structure shifted remarkably with increasing duration of remediation. Bacterial diversity exhibited a decreasing trend in the first 60 days and then recovered at 90 days. Despite having no discernible impact on the bacterial community structure in the rhizosphere, rhizobial inoculation enabled the enrichment of potentially beneficial taxa (e.g., Microvirga, Mesorhizobium, Diaphorobacter, Steroidobacter, Brevundimonas) with resistance to heavy metals and involvement in nutrient cycling. The bacterial co-occurrence networks of low and high cadmium-contaminated soils showed the highest average degree and clustering coefficient at 60 and 30 days, respectively. Some bacterial taxa involved in nitrogen fixation (e.g., Rhizobacter, Mesorhizobium), denitrification (e.g., Niastella, Nitrospira), and carbon turnover (e.g., Solirubrobacter, Brevundimonas) were found to be potential keystone taxa. The collective findings clarify possible mechanisms by which rhizosphere bacteria participate in phytoremediation of cadmium-contaminated mining soils using the R. pseudoacacia–M. loti symbiotic system.

Effects of Rhizobium Strains on Seed Yield and Yield Related Traits of Chickpea (Cicer aritienum L.) Varieties at Ambo, Ethiopia

The chickpea (Cicer arietinum L.) is a significant legume food crop in West Showa that farmers exploit to generate revenue and sustenance. Nevertheless, two major obstacles to production are the scarcity of high-quality seed and the poor fertility of the soil. Thus, the purpose of this study was to evaluate how Rhizobium inoculation affected yield, growth, and its constituent parts. Four Rhizobium strains (Cp11, Cp17, Cp41, and control) x four varieties (Eshete, Dimtu, Teketay, and Local) organized in factorial combinations were assessed using a randomized complete block design with three replications. All phenology and growth parameters, yield components, seed yield, and productivity indices were significantly influenced by both variety and Rhizobium strain, with the exception of crop phenology and hundred seed weight, which were not significantly influenced by Rhizobium strain. Plant height and the number of pods per plant were significantly impacted by the interaction between the R strain and variety. Four types yielded seed with a range of 2013.89 to 2777.78 kg ha-1, whereas inoculation procedures produced seed with a range of 2152.78 to 2690.97 kg ha-1. The Teketay variety and seeds infected with the Cp17 Rhizobium strain produced the best seed yield. Higher grain yield index per day, Rhizobium sensitive or infection index, yield index, and seed production efficiency were also seen in Teketay variety and seeds infected with Cp17 Rhizobium strain. The largest seed yield was produced by the Teketay variety inoculated with the Cp17 Rhizobium strain, and in most cases, the enhanced varieties' seeds inoculated with the Cp17 strain also produced high yields.

Effect of varietal selection and nutrient management on productivity, soil fertility and economics of summer groundnut (Arachis hypogaea)

A field experiment was conducted at research farm of Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, West Bengal, during 3 consecutive summer seasons of 2017, 2018 and 2019, to find out the influence of varietal differences and nutrient-management practices on crop productivity, soil fertility and economics in groundnut (Arachis hypogaea L.). The experiment was laid out in a split-plot design with 3 replications. Higher crop growth and yield were recorded under variety ‘TAG 24’; and 125% recommended dose of fertilizer (RDF) with Rhizobium inoculation resulted higher growth, yield attributes and yield of groundnut followed by 100% RDF + Rhizobium inoculation. The nutrient (N, P and K) availability in soil after harvesting was also higher under ‘TAG 24’ variety with 125% RDF + Rhizobium. However, interaction effect of crop variety and fertilizer treatment was found insignificant. The pooled analysis of economics revealed that, higher benefit: cost ratio (2.73) was obtained under ‘TAG 24’ in combination with 100% RDF+ Rhizobium.

Inoculant and fertilizer effects on lentil in the US northern Great Plains

AbstractLentil (Lens culinaris Medikus) is an important crop, averaging over 250,000 ha in Montana and North Dakota during 2016–2021. However, relatively little is known about rhizobial inoculant and fertility response in lentil in the US northern Great Plains. The objective was to evaluate the effect of rhizobial inoculant formulations (seed coat and in‐furrow) and nutrient additions (potassium [K], sulfur [S], and micronutrients) on lentil yield and seed protein concentration. This study was conducted at seven university research centers in Montana and North Dakota from 2019 to 2021, resulting in 20 location‐years of data. In six of 20 experiments, inoculant application increased seed yield by an average of 36% (323 kg ha−1, p ≤ 0.05) but had no consistent effect on seed protein concentration. Lentil or pea crop history among locations did not explain inoculant response. Inoculant formulations (seed coat vs. in‐furrow) and K fertilizer had inconsistent and small effects on seed yield and protein concentration. However, S fertilizer (5.6 kg S ha−1) increased seed yield in four of 20 experiments (p ≤ 0.02) by an average of 14.5% (255 kg ha−1) in those experiments and decreased seed yield for one experiment (p = 0.05) by 5.8% (153 kg ha−1). Pre‐plant SO4‐S soil test levels did not predict lentil response to S fertilizer. Micronutrient application was assessed in 12 location‐years but had no effect on lentil yield or protein concentration. This research suggests a need to better understand what factors control lentil yield and protein response to rhizobial inoculant and S fertilization.

Effectiveness of Rhizobium tropici sp. Strain UD5 Peat Biofertilizer Inoculant on Growth, Yield, and Nitrogen Concentration of Common Bean

Common bean (Phaseolus vulgaris L.) ranks among the most produced and consumed legume crops and contains essential macro- and micronutrients. Grain yield of the food crop is markedly decreased by poor management, especially a lack of additional essential nutrient elements through the application of fertilizers. In addition to the application of fertilizers, scholarly research and crop farmers have shown that the use of biofertilizer inoculants improves the yield of legume crops. The objective of this research study was to assess the effectiveness of peat-based Rhizobium tropici sp. UD5 on the growth, yield, and nitrogen concentration of common bean. The peat inoculant contained 6.5 × 109 viable cells/g. The experiment was conducted in two climatic zones, as described by the Koppen–Gieger climatic classification system. Treatments involved the peat-based inoculant Rhizobium tropici (T0 = 0 g without inoculation, T1 = 250 g of peat inoculant of strain UD5 for 50 kg seeds, T2 = 500 g of inoculant of strain UD5, and T3 = 200 g of comparative peat inoculant). The results indicated that common-bean-inoculated formulation of R. tropici sp. strain UD5 increased the following parameters compared to the controls: plant height (T1 = 18.22%, T2 = 20.41%, and T3 = 19.93% for bioclimatic zone 1; T1 = 16.78%, T2 = 20.71%, and T3 = 19.93% for bioclimatic zone 2), root length (T1 = 13.26%, T2 = 21.28%, and T3 = 19.38% for zone 1; T1 = 15.06%, T2 = 23.70%, and T3 = 19.20% for zone 2), number of nodules (T1 = 1162.57%, T2 = 1166.36%, and T3 = 1180.30% for zone 1; T1 = 1575%, T2 = 1616.5%, and T3 = 1608.25% for zone 2), size of nodules (T1 = 224.07%, T2 = 224.07%, and T3 = 208.33% for zone 1; T1 = 166.4%, T2 = 180%, and T3 = 140% for zone 2), and yield (T1 = 40.49%, T2 = 47.10%, and T3 = 45.45% for zone 1; T1 = 62.16%, T2 = 54.05%, and T3 = 58.55% for zone 2). R. tropici sp. UD5 peat inoculant formulation also increased the nitrogen concentration in leaves compared to the control (T1 = 3.75%, T2 = 1.12%, and T3 = 8.72%) in both bioclimatic zones. The findings of this study provide significant information on the positive effect of R. tropic UD5 strain peat inoculant application in the improvement of plant growth, development, and yield through the formation of nodules.

Physiological responses of low- and high-cadmium accumulating Robinia pseudoacacia-rhizobium symbioses to cadmium stress

The role of rhizobia in alleviating cadmium (Cd) stress in woody legumes is still unclear. Therefore, two types of black locust (Robinia pseudoacacia L.) with high and low Cd accumulation abilities were selected from 11 genotypes in China, and the effects of rhizobium (Mesorhizobium huakuii GP1T11) inoculation on the growth, CO2 and H2O gas exchange parameters, Cd accumulation, and the absorption of mineral elements of the high (SX) and low Cd-accumulator (HB) were compared. The results showed that rhizobium-inoculation significantly increased biomass, shoot Cd contents, Cd accumulation, root-to-shoot translocation factor (TF) and the absorption and accumulation of mineral elements in both SX and HB. Rhizobium-inoculation increased chlorophyll a and carotenoid contents, and the intercellular carbon dioxide concentrations in HB plants. Under Cd exposure, the high-accumulator SX exhibited a significant decrease in photosynthetic CO2 fixation (Pn) and an enhanced accumulation of Cd in leaves, but coped with Cd exposure by increasing chlorophyll synthesis, regulating stomatal aperture (Gs), controlling transpiration (Tr), and increasing the absorption and accumulation of mineral elements. In contrast, the low-accumulator HB was more sensitive to Cd exposure despite preferential accumulation of Cd in roots, with decreased chlorophyll and carotenoid contents, but significantly increased root biomass. Compared to the low-accumulator HB, non-inoculated Cd-exposed SX plants had higher chlorophyll contents, and rhizobium-inoculated Cd-exposed SX plants had higher Pn, Tr, and Gs as well as higher levels of P, K, Fe, Ca, Zn, and Cu. In conclusion, the high- and low-Cd-accumulator exhibited different physiological responses to Cd exposure. Overall, rhizobium-inoculation of black locust promoted the growth and heavy metal absorption, providing an effective strategy for the phytoremediation of heavy metal-contaminated soils by this woody legume.

Shining a Light on Symbiosis: N-Fixing Bacteria Boost Legume Growth under Varied Light Conditions

Legumes are a diverse and important group of plants that play a vital role in agriculture, food security, and environmental sustainability. Rhizobia are symbiotic bacteria that form nitrogen-fixing nodules on legume roots, providing the plant with a valuable source of nitrogen. Phenolic acids are a group of secondary metabolites produced by plants that have a wide range of biological functions, including defense against pests and diseases, tolerance to abiotic stresses, and nutrient uptake. In the context of climate change and the imperative for sustainable agriculture, this study delves into the dynamic responses of legume species to varying light intensities and their intricate interactions with soil microorganisms. We investigated the impact of light intensity and rhizobial inoculation on the biomass, nitrate reductase, acid phosphatase, and production of phenolic acids in the roots of four legume species, Trifolium repens, Vicia sativa, Ornithopus compressus, and Coronilla juncea. Plants were grown under three light intensity regimes (low, medium, and high) and inoculated with either rhizobia or a non-inoculated control. The results highlight that shaded-light-adapted species, T. repens and V. sativa, increased root exudate production when exposed to high light intensity. This response aligns with their mining strategy, effectively allocating resources to optimize nutrient acquisition under varying conditions. In contrast, species hailing from well-illuminated environments, O. compressus and C. juncea, displayed distinct strategies by significantly increasing biomass under high irradiance, capitalizing on the available light and nutrients. The mining strategy of legumes emerged as a central theme, influencing biomass production, nitrogen dynamics, and enzymatic activities. The strong correlations between biomass and total nitrogen accumulation underscore the role of the mining strategy in efficient nutrient acquisition. Inoculated plants, which rely more on biological nitrogen fixation (BNF), exhibited lower δ15N values, indicative of a successful mining strategy to acquire and utilize atmospheric nitrogen. Enzymatic activities and phenolic acids exhibited significant interspecies variations, reflecting the adaptability of legumes to different light conditions. The findings of this study could be used to develop new strategies for improving legume stress tolerance, nutrient uptake capacity, and rhizosphere health.

Does Rhizobial Inoculation Change the Microbial Community in Field Soils? A‍ ‍Comparison with Agricultural Land-use Changes.

Although microbial inoculation may be effective for sustainable crop production, detrimental aspects have been argued because of the potential of inoculated microorganisms to behave as invaders and negatively affect the microbial ecosystem. We herein compared the impact of rhizobial inoculation on the soil bacterial community with that of agricultural land-use changes using a 16S rRNA amplicon ana-lysis. Soybean plants were cultivated with and without five types of bradyrhizobial inoculants (Bradyrhizobium diazoefficiens or Bradyrhizobium ottawaense) in experimental fields of Andosol, and the high nodule occupancy (35-72%) of bradyrhizobial inoculants was confirmed by nosZ PCR. However, bradyrhizobial inoculants did not significantly affect Shannon's diversity index (α-diversity) or shifts (β-diversity) in the bacterial community in the soils. Moreover, the soil bacterial community was significantly affected by land-use types (conventional cropping, organic cropping, and original forest), where β-diversity correlated with soil chemical properties (pH, carbon, and nitrogen contents). Therefore, the effects of bradyrhizobial inoculation on bacterial communities in bulk soil were minor, regardless of high nodule occupancy. We also observed a correlation between the relative abundance of bacterial classes (Alphaproteobacteria, Gammaproteobacteria, and Gemmatimonadetes) and land-use types or soil chemical properties. The impact of microbial inoculation on soil microbial ecosystems has been exami-ned to a limited extent, such as rhizosphere communities and viability. In the present study, we found that bacterial community shifts in soil were more strongly affected by land usage than by rhizobial inoculation. Therefore, the results obtained herein highlight the importance of assessing microbial inoculants in consideration of the entire land management system.

Effect of rhizobial inoculation on the nodulation, growth and yield of Soybean in the Savannah regions of Nigeria

Rhizobial inoculation is the introduction of rhizobium bacteria in a high concentration into the soil before or during the planting of crops. Field experiments were conducted during the rainy seasons of 2020, 2021, and 2022 at the Research farm of the Department of Crop Sciences, Faculty of Agriculture, University of Abuja, Gwagwalada, the Southern Guinea Savanna of Nigeria. The study aimed to analyse the effect of Bradyrhizobium japonicum inoculation on the nodulation, growth and yield parameters in Soybean. The treatments consisted of three Soybean varieties, namely TGX 1485-1D (early maturing), TGX 1448–2E (medium maturing), and TGX1987–10F (medium maturing) and Two levels of inoculant (control, with inoculant), The experiment was laid out in a randomized complete block design (RCBD), with three replicates and 54 plots. Agronomic and cultural practices were duly observed, and data were collected for growth and yield parameters. Data were subjected to analysis of variance (ANOVA) using the ‘agricolae’ package in the R Statistical Programme (R version 4.2.2.), T-test was conducted using the SPSS statistical package (Version 23), and the Duncan Multiple Range Test (DMRT) and Standard error (SE) were used to separate significant means at (P ≤ 0.05). Results showed that for all varieties of Soybean observed, the inoculated had the best performance (2685kg/ha, 2842.3kg/ha, 3038.5Kg/ha for TGX 1485-1D, TGX 1448–2E and TGX1987–10F respectively best compared to the control.

Capacity of Gliricidia sepium and Indigofera zollingeriana plants which were given Rhizobium inoculants as a source of feed for Bali caws on post-mining lands

Capacity of Gliricidia sepium and Indigofera zollingeriana plants which were given Rhizobium inoculants as a source of feed for Bali caws on post-mining lands

Response of cowpea (vigna unguiculata l.) to organic and chemical fertilizer applications on grain yield and yield components

Grain of cowpea are used for human diet and its grain contains high protein, minerals and vitamins. Cowpea was also used as hay, silage, green forage, grain fodder for feed livestocks. The experiment was conducted under irrigated conditions in the experimental area of Field Crop Deparment, Faculty of Agriculture, Cukurova University, Balcalı, Adana, Turkiye. The growing period covered throughout 2021 and 2022. The field experiment was organized in split plots based on randomized complete blocks design with three replication. Two registered cultivars (Karagöz ve Akkız) were used as a research material. In this experiment the main plots were cultivars and sub-plots were application of fertilizer. Treatments were: control (no fertilizer), solid leonardite, liquid leonardite, basal chemical dose + solid leonardite, basal chemical dose +liquid leonardite, basal chemical fertilizer + additional N fertilizer. Basal chemical dose was application of 40 kg N ha-1 and 100 kg N ha-1 P2O5 (Di ammonium phosphate or DAP) before sowing as recommended chemical fertilizer. Addition chemical dose was application of 80 kg N ha-1 (Ammonium sulfate) over the basal dose at the seedling stage. Rhizobia inoculant was not applied during the field experiment. Akkız seed yield was significantly higher in application of liquid leonardite fertilizer and the combination of basal chemical fertilizer + liquid leonardite fertilizer with 1656 and 1533 kg ha-1 respectively, compared to other treatments. The grain yield in the control plot was the lowest in both cultivars. As a result, applying liquid leonardite fertilizer into the soil before sowing can be useful for grain production in cowpea.

Exploring the biochemical dynamics in faba bean (Vicia faba L. minor) in response to Orobanche foetida Poir. parasitism under inoculation with different rhizobia strains.

In Tunisia, Orobanche foetida Poir. is considered an important agricultural biotic constraint on faba bean (Vicia faba L.) production. An innovative control method for managing this weed in faba bean is induced resistance through inoculation by rhizobia strains. In this study, we explored the biochemical dynamics in V. faba L. minor inoculated by rhizobia in response to O. foetida parasitism. A systemic induced resistant reaction was evaluated through an assay of peroxidase (POX), polyphenol oxidase (PPO) and phenyl alanine ammonialyase (PAL) activity and phenolic compound and hydrogen peroxide (H2O2) accumulation in faba bean plants infested with O. foetida and inoculated with rhizobia. Two rhizobia strains (Mat, Bj1) and a susceptible variety of cultivar Badi were used in a co-culture Petri dish experiment. We found that Mat inoculation significantly decreased O. foetida germination and the number of tubercles on the faba bean roots by 87% and 88%, respectively. Following Bj1 inoculation, significant decreases were only observed in O. foetida germination (62%). In addition, Mat and Bj1 inoculation induced a delay in tubercle formation (two weeks) and necrosis in the attached tubercles (12.50% and 4.16%, respectively) compared to the infested control. The resistance of V. faba to O. foetida following Mat strain inoculation was mainly associated with a relatively more efficient enzymatic antioxidative response. The antioxidant enzyme activity was enhanced following Mat inoculation of the infected faba bean plant. Indeed, increases of 45%, 67% and 86% were recorded in the POX, PPO and PAL activity, respectively. Improvements of 56% and 12% were also observed in the soluble phenolic and H2O2 contents. Regarding inoculation with the Bj1 strain, significant increases were only observed in soluble phenolic and H2O2 contents and PPO activity (especially at 45 days after inoculation) compared to the infested control. These results imply that inoculation with the rhizobia strains (especially Mat) induced resistance and could bio-protect V. faba against O. foetida parasitism by inducing systemic resistance, although complete protectionwas not achieved by rhizobia inoculation. The Mat strain could be used as a potential candidate for the development of an integrated method for controlling O. foetida parasitism in faba bean.

Does coinoculation with bradyrhizobia and cyanobacteria improve groundnut growth and yield?

Summary Groundnut plants can obtain N from N2 fixation via symbiosis with rhizobia, and inoculation with selected strains can improve grain yields. We report the results of four field experiments carried out under subtropical conditions to confirm whether microbial inoculants can improve groundnut performance through the effects of single inoculation with Bradyrhizobium arachidis (SEMIA6144), coinoculation with Arthrospira platensis (IPR7059) or Synechocystis sp. (IPR7061), or N fertilization with 100 kg ha-1 N on plant growth, nodulation, N accumulation in tissues, grain protein concentration (GPC), and grain yield. There were no effects of inoculation treatment or N fertilizer on shoot or root dry weight. In clayey soil, coinoculation with B. arachidis and cyanobacteria increased grain productivity by an average of 19% compared to that in the noninoculated control. In this clayey soil with a higher P content, regardless of whether coinoculated with B. arachidis or cyanobacteria or single inoculated, grain productivity was 16% greater on average than that resulting from N fertilizer addition. In conclusion, the success of rhizobial inoculation in groundnuts is dependent on the soil, probably due to P limitation and weather conditions.

Application of Rhizobium inoculants and Phosphorus fertilizer for effective nodulation of Chickpea at T/koraro Tigray Ethiopia

This study was conducted over the 2015 and 2016 main cropping seasons under rain-fed conditions at T/koraro in the North Western Zone of Tigray Regional State, Ethiopia. The objective was to evaluate the impact of different fertilizer treatments on chickpea agronomic performance and soil properties. The experiment employed a randomized complete block design (RCBD) with four treatments: T1 (control without inoculant), T2 (50 kg DAP), T3 (50 kg DAP + CP inoculant), and T4 (CP inoculant + compost), each replicated three times. Composite soil samples were collected and analyzed for texture, pH, EC, organic carbon, available phosphorus, and CEC before planting. Agronomic data collected included biomass yield, grain yield, days to 50% emergency and flowering, plant height, number of nodules, and harvest index. Results showed that treatments significantly affected soil properties and chickpea growth parameters. T4 (CP inoculant + compost) produced the highest biomass (4412.3 kg/ha) and grain yield (2015.0 kg/ha), indicating a 40.03% increase over the control. The number of nodules per plant was highest in T4, emphasizing the role of phosphorus and inoculants in enhancing nitrogen fixation and plant growth. Days to 50% emergency and flowering were reduced in treated plots, suggesting an accelerated growth rate due to nutrient availability. Plant height and the number of pods per plant were positively influenced by the application of compost and DAP fertilizer. Statistical analysis using ANOVA and LSD tests confirmed significant differences between treatments at a 5% significance level. The study concludes that the combined application of compost and CP inoculant significantly improves chickpea yield and soil health, offering a sustainable approach to crop production in the region.

Factors Influencing Selection and production of Common Bean Cultivars in medium Potential Agro Ecological Zone of Imenti South Sub-County, Kenya

Varietal selection is a key aspect in common bean production in Kenya since different varieties are bred for specific agro ecological conditions. In Kenya, many common bean varieties are found growing under medium agro ecological zones, however, some farmers have been found to grow some bean varieties not suited to preferred ecological zones. The current study was thus carried out to assess the factors that affect varietal selection and production of common beans in medium potential agro ecological zones of Imenti South Sub County, Meru County. The target population was 300 common bean farmers. A sample size of 75 farmers derived from Gaatia, Kathanthatu, Kiambogo and Kiigene villages using Nassiuma Formula. A structured questionnaire was administered to collected data on socioeconomic factors, common bean production systems and agronomic practices. The collected data weresubjected to analysis of variance (ANOVA) using SAS version 9.4 and Significant means separated using least significant difference at p< 0.05. The findings on socio-economic factors revealed that farmers with higher levels of education produced more beans per unit area. Approximately 10.52 % of the 22.37 % of the farmers with tertiary college education had a production of 1.4 – 1.9 tonnes/ha. Majority (88.16 %) of the farmers applied DAP planting fertilizer,while none of the farmersapplied rock phosphate. Moreover, the highest percentage (34.9 %) of farmers who applied DAP had attained tertiary level education. Most (18.42 %) middle aged farmers did not apply rhizobium inoculant during planting. The most popular production system was mixed cropping (46.7 %) and the least was intercropping (6.59 %). Mixed cropping was highest in farmers who planted GLP 585 (13.33 %) and least in KAT B1 (10.23 %). Sole cropping was highest in Mwitemania (12.0 %) and least in Rose coco (6.58 %). Crop rotation was highest in Rose coco (5.26 %) and least in GLP 585, Mwitemania and KAT B1 (2.63 %). Intercropping was highest in Rose coco (2.63 %) and least in GLP 585, Mwitemania and KAT B1 varieties at (1.32 %).Bean variety KAT B1 despite being bred for semi-arid agro ecological zones, performed fairly well in medium potential agro ecological zones. Bean variety KAT B1 can be recommended for production in medium potential agro ecological zones to enhance common bean production and food security in Kenya.