Effect Of Rhizobial Inoculation Research Articles

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.

Bradyrhizobium arachidis mediated enhancement of (oxy)matrine content in the medicinal legume Sophora flavescens.

Effect of rhizobial inoculation and nitrate application on the content of bioactive compounds in legume plants is an interesting aspect for interactions among microbes, plants and chemical fertilizers, as well as for cultivated practice of legumes. In this study, nitrate (0, 5 and 20mmoll-1 ) and Bradyrhizobium arachidis strain CCBAU 051107T were applied, individually or in combination, to the root rhizosphere of the medicinal legume Sophora flavescens Aiton (SFA). Then the plant growth, nodulation and active ingredients including (oxy)matrine of SFA were determined and compared. Rhizobial inoculation alone significantly increased the numbers and fresh weight of root nodules. Nodulation was significantly inhibited due to nitrate (5 and 20mmoll-1 ). Only oxymatrine was detected in the control plants without rhizobial inoculation and nitrate supplement, while both oxymatrine and matrine were synthesized in plants treated with inoculation of B. arachidis or supplied with nitrate. The content of oxymatrine was the highest in plants inoculated solely with rhizobia and was not significantly altered by additional application of nitrate. Combinations of B. arachidis inoculation and different concentrations of nitrate did not significantly change the concentrations of (oxy)matrine in the plant. In conclusion, sole rhizobial inoculation was the best approach to increase the contents of key active ingredients oxymatrine and matrine in the medicinal legume SFA.

Effect of rhizobial inoculation combined with phosphorus fertilizer on nitrogen accumulation, growth and yield of soybean in Benin

The objective of this study was to determine the amount of phosphorus application needed for the Bradyrhizobium inoculation to improve soybean N uptake and grain yield. Two factors were investigated: inoculation with Bradyrhizobium diazoefficiens strain USDA 110 and application of phosphorus fertilizer with different doses (0; 50; 100 and 150 kg ha-1 P2O5). Trials were carried out in two agro-ecological zones (ZAE) in Benin with two experimental sites namely Ketou and Ze. The experimental design was a Complete Randomized Block Design. Results showed that the highest mean height values were recorded T1+150P (42.22 cm at Ze and 43.82 cm at Ketou) while the lowest values were recorded with the treatment T0 + 0P. Treatment T0 +100P gave the highest aboveground biomass at 10 weeks after sowing at Ketou (2521.43 kg DM ha-1) while T1+150P recorded the highest aboveground biomass at Ze (3392.75 kg DM ha-1). At Ketou, the grain yield was increased under T1+100P by 98% compared with T0+0P. At Ze, the treatments T1+100P significantly increased the soybean grain yield by 147% compared with T0+0P. Likewise, T1+100P allowed to have the highest total nitrogen yields in the grain which is respectively 144.13 kg ha-1 N and 295.02 ha-1 kg N at Ketou and Ze. Overall, the inoculation with B. diazoefficiens had significantly increased the number of nodules for all of the phosphorus fertilizer amounts. The mycorhization frequency was significantly lower under the treatment T0 + 0P (41.46%) than the other treatments while that was higher under the treatment T1+50P (76.04%). Keywords: Bradyrhizobium diazoefficiens, soybean inoculation, grain yield, Benin.

Agronomical parameters of host and non-host legumes inoculated with Melilotus indicus-isolated rhizobial strains in desert unreclaimed soil.

In a search for identification of rhizobial strains with superior N2-fixation efficiency and improved plant agronomic characteristics upon inoculation, four strains, 4.21, 9.17, 11.2 and 14.1, isolated from root nodules of wild-grown Melilotus indicus have been used to inoculate field-grown common bean, pea, cowpea and fenugreek plants. Uninoculated plants and those inoculated with host-specific commercial inoculants were used as a control. The root length, shoot height, shoot dry weight and root dry weight and the grain yield of the plants were determined after harvest. The content of N, organic C and carbohydrates content of the grain were also recorded. The inoculation with the strains 4.21 and 14.1 increased the grain yield of the fenugreek compared both with the uninoculated plants and those inoculated with the commercial strain ARC-1. The grain yield of the common bean treated with the strains 9.17 and 14.1 was also higher than that of the uninoculated and the commercial strains ARC-301. In contrast, none of the strains increased the grain yield of the pea and cowpea plants compared to the commercial strains ARC-201 and ARC-169, respectively. Significant increases of some agronomical parameters were observed in some plant-bacterium couples, albeit nodulation was not observed. It is possible that the positive effects of rhizobial inoculation on the agronomical parameters of the non-nodule forming legumes could be due to plant growth promotion characteristic of the strains used for inoculation. Analysis of the phylogeny of the almost complete 16S rRNA sequence of the rhizobial inoculants revealed that the strains 4.21 and 9.17 clustered together with R. skierniewicense and R. rosettiformans, respectively, and that the strains 11.2 and 14.1 grouped with E. meliloti. All the four strains produced IAA, and showed biocontrol activity against Rhizotocnia solani, Fusarium oxysporum, Pythium ultimum, Alternaria alternata and Sclerotonia rolsfi, albeit to a different extent.

Diversity and Functionality of Culturable Endophytic Bacterial Communities in Chickpea Plants.

The aims of this study were to isolate, identify and characterize culturable endophytic bacteria from chickpea (Cicer arietinum L.) roots grown in different soils. In addition, the effects of rhizobial inoculation, soil and stress on the functionality of those culturable endophytic bacterial communities were also investigated. Phylogenetic analysis based on partial 16S rRNA gene sequences revealed that the endophytic bacteria isolated in this work belong to the phyla Proteobacteria, Firmicutes and Actinobacteria, with Enterobacter and Pseudomonas being the most frequently observed genera. Production of indoleacetic acid and ammonia were the most widespread plant growth-promoting features, while antifungal activity was relatively rare among the isolates. Despite the fact that the majority of bacterial endophytes were salt- and Mn-tolerant, the isolates obtained from soil with Mn toxicity were generally more Mn-tolerant than those obtained from the same soil amended with dolomitic limestone. Several associations between an isolate’s genus and specific plant growth-promoting mechanisms were observed. The data suggest that soil strongly impacts the Mn tolerance of endophytic bacterial communities present in chickpea roots while rhizobial inoculation induces significant changes in terms of isolates’ plant growth-promoting abilities. In addition, this study also revealed chickpea-associated endophytic bacteria that could be exploited as sources with potential application in agriculture.

Inoculant rhizobia suppressed root-knot disease, and enhanced plant productivity and nutrient uptake of some field-grown food legumes

ABSTRACTThe potential effect of rhizobial inoculation on root knot nematodes in chickpea, mungbean and pigeonpea were studied under field condition. The seed treatment with respective rhizobium strains increased the nodulation, leghemoglobin content, bacteriod population, plant growth, yield and nitrogen uptake of three three food legumes compared to the plants without the rhizobium treatment. The nematode (1500 juveniles/kg soil) incited oval galls on the roots of the three legumes, and suppressed plant growth and yield. The galling, egg mass production and soil population of the nematode was greater on the plants without the rhizobium treatment. The pure culture and culture filtrate of the rhizobium strains suppressed the egg hatching and induced mortality to the juveniles of M. incognita over control. The nematode infection reduced the nodulation, bacteroid population and leghemoglobin contents of the nodules and NPK uptake by the plants. Hence, the rhizobia treatment shall be integrated to common agronomic practice of food legume cultivation so as to enhance crop productivity and to protect roots from nematode attack.

Effect of Rhizobial Inoculation and Weed Control on Weed Species, Bactria Nodulation and Peas Yield

Effect of Rhizobial Inoculation and Weed Control on Weed Species, Bactria Nodulation and Peas Yield

Effect of Fertilizer and Fixed Nitrogen on the Water Use Efficiency of Genge (Astragalus sinicus L.)

To compare the effect of fertilizer nitrogen (N) and fixed N on water use efficiency (WUE), we measured the cumulative evapotranspiration (ΣET) and total dry matter mass (DM) of genge growing in plant growth chambers. When regulating NH4–N application at 11 levels ranging from 0 – 315 mgN flask −1, N concentration of the genge rose from 0.7% to 3.9% as fertilizer N application was increased. Although both DM and ΣET changed on a quadratic curve, their relationship approximated a single regression line, regardless of N concentration. The effects of rhizobial inoculation of genge samples along with NH4–N application rates of 0, 10.5, 105, and 252 mgN flask−1 were also tested. The samples with application rates of 0 and 10.5 mgN flask −1, where both nodulation and fixed N application were confirmed, had lower WUE than un-inoculated samples. These results suggest that the impact on WUE is much greater in fixed N than in fertilizer N.

Diversity and phylogeny of soybean rhizobia in central India

Soybean is the most important crop legume with the highest share of biological nitrogen fixation among cultivated legumes. During the early years following the introduction of soybean cultivation in India, the effects of rhizobial inoculation were impressive, but they have declined over time due to naturalization of the introduced strains. We have characterized the diversity of soybean rhizobia, mainly those from central India, for phenotypic features, such as utilization of carbon sources and intrinsic resistance to antibiotics. The PCR-amplified 16S rRNA gene products of the strains were sequenced to study genetic diversity and phylogenetic relationships. We found that the rhizobia comprised both slow and fast growers, with the former having a higher Shannon–Weiner Diversity Index (H = 2.93 and 3.00 for carbon utilization and intrinsic antibiotic resistance, respectively) than the latter (H = 2.62 and 1.90, respectively). There were two 16S rRNA sequence types among the slow growers—Bradyrhizobium spp. (99.4–99.8 % sequence homology) and Rhizobium radiobacter (96.1–99.7 %). In contrast, the fast growing strains belonged exclusively to R. radiobacter (98.9–99.7 %). Bradyrhizobium japonicum strain USDA 110, which was originally introduced on a large scale in Indian soils more than four decades ago, shared 34–81 % phenotypic and 63–83 % genotypic similarity with the other Indian rhizobial isolates characterized. There was conservation of 16S rRNA gene sequences among rhizobia in various soybean-growing areas and the evolution of native rhizobial strains among slow and fast growers. These results on the biodiversity of soybean rhizobia are important for strain selection, which is crucial for the design of successful inoculation programs.

Seasonal changes of bacterial communities in the rhizosphere of Acacia senegal mature trees inoculated with Ensifer strains in Burkina Faso and Niger

Acacia senegal is of paramount importance in sub Saharan Africa because it produces gum arabic. Inoculation with specific rhizobial strains improves the vigour of the trees but also positively enhances the gum arabic production of mature trees. A host-specific cocktail of Ensifer strains was used to inoculate mature A. senegal trees in Burkina Faso and Niger. Rhizosphere soils were sampled during dry and rainy seasons from 2006 to 2008. Total microbial biomass and soil inorganic nitrogen were assessed, and DNA extracted and used to analyse diversity of A. senegal rhizosphere bacterial communities on Denaturing Gradient Gel Electrophoresis after PCR amplification of the 16S rDNA. In Niger, results showed a significant increase of total bacterial diversity due to the season but no effect of the rhizobial inoculation was observed. However, a significantly higher microbial biomass was found in soil from uninoculated trees than from inoculated trees. In Burkina Faso, no effect of both season and rhizobial inoculation was observed on total bacterial diversity, but higher microbial biomass values were obtained compared to Niger, especially for 2006. However, there were no significant differences between inoculated and uninoculated trees. Rhizobial inoculation significantly enhanced gum arabic production in Niger but not in Burkina Faso.

Effects of rhizobial inoculation, cropping systems and growth stages on endophytic bacterial community of soybean roots

The effects of rhizobial inoculation, soybean-maize intercropping and plant growth stages on the diversity of soybean root endophytic bacteria were evaluated. PCR-based terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes and analyses of cloned partial 16S rRNA gene libraries were used to study the endophytic bacterial communities. The root endophytic bacterial populations during the whole growing season was significantly affected by the three factors analyzed, with plant growth and rhizobial inoculation showing the highest and lowest impact. The alphaproteobacteria and betaproteobacteria were the most predominant endophytes of soybean roots. Some undefined bacterial lineages were also found, indicating that the root endophytic populations might constitute an important source for the isolation of novel bacteria. Bradyrhizobium liaoningense (used as inoculant) occupied most of the soybean nodules formed and Sinorhizobium americanum-related bacteria were detected as the main root endophytes. Results also suggest that bacteria might be transferred from nodules to roots (as endophytic bacteria) when the seeds become mature, which might be a possible process in the life cycle of rhizobia. Rhizobial inoculation and intercropping practices could increase the diversity of the soybean root endophytes, which might have a positive influence on the growth of soybean plants.

The efficiency and competitiveness of three Mesorhizobium sp. strains nodulating Acacia senegal (L.) Willd. under water deficiency conditions in the greenhouse

The combined effects of drought and salinity were investigated on the growth, efficiency and competitiveness of three Mesorhizobium sp. strains (ORS 3416, ORS 3428 and ORS 3437) isolated from Acacia senegal (L.) Willd. Sixteen combinations of polyethylene glycol (PEG) 6000 (0, 6, 12, 20%, w/v) and NaCl (0.005, 0.5, 1, 1.5%, w/v) were used to study rhizobial strains growth in screw-capped tubes containing yeast extract mannitol liquid medium. Whatever the combination, the strains grew. However, high concentrations of PEG 6000 and NaCl were depressed on rhizobial growth but strain ORS 3428 was the most tolerant. The effect of rhizobial inoculation on growth of A. senegal plants was also examined under non-limited (100% of water holding capacity, WHC) and water-limited conditions (50% WHC) in the greenhouse for 4 months on non-sterile sandy soil. A significant decrease in the nodulation rate, nodule dry weight, plant height and shoot dry weight was observed under water-limited conditions. Nevertheless, inoculation with the three selected Mesorhizobium strains significantly improved nodulation and A. senegal plant growth under water-limited conditions. Whatever the irrigation condition, strains ORS 3428 and ORS 3437 were more competitive than ORS 3416. These rhizobial strains may prove valuable for inoculation of Acacia senegal plants grown for transplantation to dry saline habitats.

Effect of on-field inoculation of Phaseolus vulgaris with rhizobia on soil bacterial communities

The aim of this study was to assess the impact of inoculation of Phaseolus vulgaris with two indigenous rhizobia strains on plant growth promotion, nitrogen turnover processes, richness and structure of the Rhizobiaceae and total bacterial communities in the bulk soil. Both strains used induced a significant increase in nodulation and grain yield. Analysis of bulk soil fertility showed positive, negative and strain-dependent effects of inoculation on nitrate, phosphorus and ammonium, respectively. Terminal-restriction fragment length polymorphism profiling demonstrated that inoculation significantly increased the phylotype richness of the bacterial communities. No significant difference in richness between the strains used and no additive effect of co-inoculation were observed. However, differences between both inoculants and a clear additive effect of co-inoculation on heterogeneity were found. This work gives original insights into the effect of rhizobial inoculation outside the restricted rhizospheric area. Effects on bacterial structure and diversity are clearly sensed in the neighbourhood of 25 cm and in a limited time course. Both Alpha- and Gammaproteobacteria, together with Firmicutes and Actinobacteria, were enhanced by inoculation, No evidence of terminal-restriction fragment inhibition was found. However, it remains to be answered how the impact on taxonomic groups can be related to effects on functional capabilities of soil microbial communities.

Rhizobial Association with Non-Legumes: Mechanisms and Applications

It has been known for more than a century that rhizobia can promote the growth of legumes through the formation of nitrogen-fixing nodules, but the interaction of rhizobia with non-legumes has been neglected as an experimental system. During the last couple of decades, work on rhizobial interaction with non-legumes has been done progressively and it has been demonstrated that rhizobia can associate with roots of non-legumes also, without forming true nodules, and can promote their growth by using one or more of the direct or indirect mechanisms of actions. Phytohormone production, secretion of other chemicals like lipo-chito-oligosaccharides (LCOs) and lumichrome, solubilization of precipitated phosphorus and mineralization of organic P, improvement in uptake of plant nutrients by altering root morphology, production of siderophores to meet the iron requirements of the plant under iron-stressed conditions and lowering of ethylene level through ACC deaminase enzyme, are some examples of the rhizobial mechanisms with direct positive effects on non-leguminous plant growth. Indirectly, rhizobia improve the growth of non-legumes through biocontrol of pathogens via antibiosis, parasitism or competition with pathogens for nutrients and space, by inducing systemic resistance in the host plant and through increasing root adhering soil by releasing exopolysaccarides which regulate the water movement and facilitate the root growth. However, no influence or even inhibitory effects of rhizobial inoculation on non-legumes has also been demonstrated in some cases. Plant growth promoting mechanisms of rhizobia and its practical application in non-legumes are the major focus of this review.

Effect of rhizobial inoculation on growth of Calliandra tree species under nursery conditions

A nursery experiment was conducted in un-sterilized soil in Senegal using six Calliandra species or provenances inoculated with a mixture of seven rhizobial strains. Plant growth was assessed periodically at 1, 2, 3, 12 and 18 months whereas nodulation, shoot and root dry weights were assessed at 12 and 18 months after planting (MAP). Un-inoculated seedlings of all the six species died at 12 months after planting. Results of growth assessments were variable with significant differences (P < 0.05) between C. calothyrsus Meissn provenances (Flores and San Ramon) and C. juzepczukii Standley in height at 1, 2 and 3 MAP. Shoot dry weights of San Ramon provenance of C. calothyrsus Meissn were also significantly different from those of C. acapulcensis (Britton and Rose) Standley and C. longepedicellata (Mc Vaugh) H. Hern and Macqueen at 18 MAP. In contrast, C. glandiflora (L’Her.) Benth grew poorly and did not nodulate. Although rhizobial inoculation improved shoot and root dry weights some differences were observed among the Calliandra species in response to the inoculation, which suggested the occurrence of interaction between the rhizobial strains and the host plant species tested.

Effect of rhizobial inoculation on growth, yield, nodulation and biochemical characters of vegetable pea ( Pisum sativum )

A field experiment was conducted with 8 genotypes of vegetable pea and 3 levels of rhizobial inoculation for two consecutive years. Inoculation with Rhizobium leguminosarum @ 20 g kg −1 seed made the plants taller and enhanced biomass production through branching, but delayed maturity. It resulted in more pods, enlarging them to contain more seeds, leading to higher test weight and enhanced harvest index. It increased nodulation, the benefit of which was reflected in most of the yield traits. It also enriched the seeds with nitrogen and protein, as well as activating nitrogenase enzyme in the root nodules to fix more atmospheric nitrogen.

Nodulation and effect of rhizobial inoculation on biochemical Sesban (L.) Merr. constituents of Sesbania

Soil samples from 10 different regions in Andhra Pradesh were collected and plants of Sesbania sesban (L.) Merr. were raised in pots containing each kind of soil. The chemical and physical properties of each kind of soil were broadly similar. Root nodulation characters of the Sesbania sesban were studied at 50 DAS. Highest nodule number was observed in plants raised in SS3 region. The Rhizobium isolates were obtained from root nodules of S. sesban grown in these soils. The plants inoculated with SSR-7 and SSR-8 gave maximum nodule number and biochemical constituents.

Potential use of Iberian shrubby legumes and rhizobia inoculation in revegetation projects under acidic soil conditions

Disturbances that affect plant and soil properties are important threats to the stability of ecosystems. Since positive interactions with soil microorganisms are essential for plant growth, the restoration of heavily disturbed habitats should include the re-introduction of both plants and their mutualists. In Mediterranean areas, shrubby legumes are key components of natural systems and good candidates for revegetation projects because of the ability to fix nitrogen as a result of the rhizobial symbiosis. This study analyses the role of soil microorganisms, and, specifically, of Bradyrhizobium sp., in the growth of six Iberian shrubby legumes in natural soils from central western Spain. Plants were grown in non-treated soils and in soils from which soil microorganisms were experimentally removed. The effect of rhizobial inoculation on plant performance was assessed using six Bradyrhizobium strains isolated from natural populations of the studied species. Plant growth was hindered in sterilized soils, whereas inoculation with native rhizobia significantly enhanced plant growth. The results highlight the importance of positive interactions with soil microorganisms for plant growth and advise the use of native organisms as inoculants in revegetation strategies.

Influence of Rhizobial Inoculation on Photosynthesis and Grain Yield of Rice

Rhizobial inoculation increases grain yield in rice (Oryza sativa L.), a nonlegume plant, but little is known about the mechanism(s) involved. This study was conducted to determine whether inoculation with rhizobia could influence leaf photosynthesis of rice plants under greenhouse conditions. Rice seeds and pot soil were inoculated with three rhizobial strains with or without added N fertilizer. Single‐leaf net photosynthetic rates were measured with portable photosynthesis systems (LI‐6200 and LI‐6400) at several growth stages. Stomatal conductance, chlorophyll fluorescence, specific leaf weight, and leaf N content were also measured. Grain yield and yield components were determined at maturity. A significant increase in single‐leaf net photosynthetic rate by rhizobial inoculation was observed in all three independent experiments. The effect of rhizobial inoculation on photosynthesis was greater in zero‐N than in 90 kg N ha−1 treatment. The increase in photosynthetic rate by rhizobial inoculation was 12% averaged across all treatments in the three experiments. The effects of rhizobial inoculation on stomatal conductance, specific leaf weight, and leaf N content were relatively small and less consistent than photosynthetic rate. Chlorophyll fluorescence data suggest that the increase in photosynthetic rate following rhizobial inoculation was not associated with conversion efficiency of light energy in photosystem II. Rhizobial inoculation increased grain yield by 16%. The increase in grain yield was due to an increase in total biomass production rather than harvest index. These results suggest that certain strains of rhizobia can promote rice growth and yield through mechanisms that improve single‐leaf net photosynthetic rate.

Effect of Rhizobial Inoculation on Albizia lebbeck and Its Rhizosphere Activity in Mine Spoils

The evolution of stable and productive mine spoil requires active microbial populations for effective energy flow and nutrient cycling. This can be achieved either by introducing beneficial microorganisms through inoculation or increasing the microbial activity through the incorporation of amendments. Efficient strains of Bradyrhizobium sp. were isolated from mine spoils and used to inoculate seeds of Albizia lebbeck grown in both gypsum and limestone mine spoils. It was observed that nodulation and nitrogenase activity were significantly improved by about 2- and 20-fold respectively with inoculation, along with an enhancement in the growth of 5-month-old seedlings by about 50%. Inoculated plants had higher concentrations of nitrogen and phosphorus, indicating better nutrition. Soil metabolism, as indicated by the activities of dehydrogenase and phosphatases and AM-fungal spores of the mine spoils, was significantly improved with inoculation. The results suggests that the use of efficient strains of Bradyrhizobium for A. lebbeck may be a useful technology for revegetating mine spoils and improving the productivity of these mine spoils.