Effective Nodules Research Articles

Performance of Black gram (Vigna mungo L. Hepper) under Different Levels of Phosphorus at Bardiya, Nepal

A field experiment was conducted during the spring season of 2023 in Badhaiyatal Rural Municipality-7, Bardiya district to evaluate the performance of black gram at various levels of phosphorus. A randomized complete block design (RCBD) consisting of four treatments and five replications were used for the study. The treatments consisted of different levels of phosphorous viz. 0 Kg ha-1 (control), 20 Kg ha-1, 40 Kg ha-1 and 60 Kg ha-1. Black gram var. BLG 0093-1 was sown at spacing of 40 cm x 5 cm in the plots sized 8 m2. All the growth parameters and yield obtained from each treatment were compared at 5% level of significance. The results showed significantly greater number of branches (13.84), flower buds (11.33), root length (16.27 cm) and secondary roots (16.05) at 60 Kg phosphorus per ha followed by 40 Kg ha-1. However, plant height, pods per plant, seeds per pod, weight of pods per plant, biomass and grain yield showed non-significant results at similar levels of phosphorus (60 Kg ha-1). Though non-significant, higher number of fruiting branch, number of nodules, effective nodules, 1000 grain weight and harvest index were observed at 40 Kg ha-1 phosphorus. The findings suggested a gradual increase in the yield with increasing levels of phosphorus with the highest gross return from 60 Kg ha-1 phosphorus. However, since the variation in grain yield among the treatments was not significant, the cost involved with the 60 Kg ha-1 was greater as compared to 40 Kg ha-1 phosphorus, greater benefit was observed with the latter. So, on grounds of greater net return and better BC ratio, 40 Kg ha-1 phosphorus seems to be more profitable for the farmers.

Virtual thoracoscopic imaging for accurate pulmonary nodule localization: clinical experience.

The increasing detection of small pulmonary nodules on computed tomography (CT) warrants simple and effective nodule localization methods. We describe our clinical experience using an experimental computer that displays virtual thoracoscopic images. This device constructs three-dimensional images from preoperative CT scans and simulates the deflated lung parenchyma in the lateral decubitus position. Five patients underwent lung resection using this technology. The device provided images that closely resembled actual thoracoscopic images in all cases. This method addresses the limitations of other localization techniques such as allergic reactions and mechanical marker-related complications. The method only requires preoperative CT images, and the process is semi-automatically performed by specifying the nodule location, thoracoscopic camera insertion site, and camera angle. This study is still in the preliminary phase and has several limitations. However, this method has the potential to accurately predict nodule locations and eliminate the many risks associated with other techniques.

Rhizobial secretion of truncated exopolysaccharides severely impairs the Mesorhizobium-Lotus symbiosis.

The symbiosis between Mesorhizobium japonicum R7A and Lotus japonicus Gifu is an important model system for investigating the role of bacterial exopolysaccharides (EPS) in plant-microbe interactions. Previously we showed that R7A exoB mutants that are affected at an early stage of EPS synthesis and in lipopolysaccharide (LPS) synthesis induce effective nodules on L. japonicus Gifu after a delay, whereas exoU mutants affected in the biosynthesis of the EPS side chain induce small uninfected nodule primordia and are impaired in infection. The presence of a halo around the exoU mutant when grown on Calcofluor-containing media suggested the mutant secreted a truncated version of R7A EPS. A non-polar ΔexoA mutant defective in the addition of the first glucose residue to the EPS backbone was also severely impaired symbiotically. Here we used a suppressor screen to show that the severe symbiotic phenotype of the exoU mutant was due to secretion of an acetylated pentasaccharide, as both monomers and oligomers, by the same Wzx/Wzy system that transports wild-type exopolysaccharide. We also present evidence that the ΔexoA mutant secretes an oligosaccharide by the same transport system, contributing to its symbiotic phenotype. In contrast, ΔexoYF, and polar exoA and exoL mutants have a similar phenotype to exoB mutants, forming effective nodules after a delay. These studies provide substantial evidence that secreted incompatible EPS is perceived by the plant leading to abrogation of the infection process.

Inter-species interaction of bradyrhizobia affects their colonization and plant growth promotion in Arachis hypogaea.

Bradyrhizobia are the principal symbiotic partner of the leguminous plant and take active part in biological nitrogen-fixation. The present investigation explores the underlying competition among different strains during colonization in host roots. Six distinct GFP and RFP-tagged Bradyrhizobium strains were engineered to track them inside the peanut roots either independently or in combination. The Bradyrhizobium strains require different time-spans ranging from 4 to 21days post-infection (dpi) for successful colonization which further varies in presence of another strain. While most of the individual strains enhanced the shoot and root dry weight, number of nodules, and nitrogen fixation capabilities of the host plants, no significant enhancement of plant growth and nodulation efficiency was observed when they were allowed to colonize in combinations. However, if among the combinations one strains is SEMIA 6144, the co-infection results in higher growth and nodulation efficiency of the hosts. From the competition experiments it has been found that Bradyrhizobium japonicum SEMIA 6144 was found to be the most dominant strain for effective nodulation in peanut. The extent of biofilm and exopolysaccharide (EPS) production by these isolates, individually or in combinations, were envisaged to correlate whether these parameters have any impact on the symbiotic association. But the extent of colonization, growth-promotion and nitrogen-fixation ability drastically lowered when a strain present together with other Bradyrhizobium strain. Therefore, it is imperative to understand the interaction between two co-inoculating Bradyrhizobium species for nodulation followed by plant growth promotion to develop suitable consortia for enhancing BNF in peanut and possibly for other legumes.

Effect of Rhizobium Bacteria Inoculation Rate on Yield and Yield Components of Field Pea (Pisum sativum L.) at Awi Zone, Ethiopia

Field peas (Pisum sativum L.) is economically a significant crop in Ethiopia. The yield of field peas in our country has fell due to poor management practices of Bio fertilizer rates usage. Three rates of bio fertilizer (0, 250 and 500g ha-1) were laid out in Randomized Complete Block Design with three replications. Number of nodules per plant, Pod numbers per plant, plant height, and effective nodule number of productive tillers, total biomass yield, grain yield, and straw yield were recorded and significantly affected by bio-fertilizer rate application. The determined or the highest grain yield (2671kg ha-1) was recorded from 250 g ha-1 bio-fertilizer rate. Almost 250g ha-1 bio fertilizer rates were superior for the research area. Nevertheless, more investigation has to be done under different locations and seasons to come up with practical recommendations correlated to the current study.

Structure of root nodules in <i>Laburnum anagyroides</i> Medik.

The structure of the <i>Laburnum anagyroides</i> root nodules was studied by means of classical light and transmission electron microscopy methods. The ability of cross-inoculation and effective nodulation by rhizobial microsymbionts, effective in other genistean species, was not confirmed in <i>L. anagyroides</i>. However, the seedlings were successfully albeit ineffectively nodulated by non-identified rhizobia from soil sampled under established <i>L. anagyroides</i> trees. The microscopic (ultra)structure of these nodules met the basic criteria of genistoid nodules: their meristem was apically positioned and contained two domains (infected and non-infected one), non-bacteroidal rhizobia persisted in apoplast enclaves, and intra-nodule rhizobial infection was passed from cell to cell by host cell division and not by infection threads. The developmental disturbances detected in the nodules (primarily, formation of multi-bacteroid sacs instead of typical single-bacteroid symbiosomes and proliferation apoplast enclaves with accompanying cell wall discontinuities) suggested that the host plant incorrectly recognized the microsymbiont used in the present study.

Bradyrhizobium Inoculation Improved Agrosymbiotic Performances of Cowpea [Vigna unguiculata (L) Walp] Varieties at Two Sites in Ethiopia

Cowpea [Vigna unguiculata (L) Walp] is an important crop that protects soil fertility, supplements protein deficiency, and provides food security in the face of climate change. However, its productivity in the study area is low due to a lack of high‐yielding varieties, high cost of mineral fertilizer, insufficient information on effective inoculum, and inadequate management practices. Therefore, this study aimed to assess the agrosymbiotic response of inoculated cowpea varieties at Dale and Hawassa sites in Ethiopia. A factorial combination of four cowpea varieties (Bole, TVU, Keti, and White Wonderer Trailing) and two inoculation levels (uninoculated and strain CP‐24 inoculated) were evaluated in two experimental sites using a randomized complete block design with three replications. The results revealed that phenology, nodulation, growth, yield, and yield components differed significantly (P < 0.05) among the tested cowpea varieties. Among the varieties, the White Wonder Trailing produced the highest grain yield of 2.98 t ha−1. The influence of Bradyrhizobium strain CP‐24 was apparent in most of the studied parameters, except for days to emergence and harvest index. It increased cowpea grain yield by 28.47% compared to the control. The interaction of variety and Bradyrhizobium inoculation revealed a significant effect on nodule number, effective nodules, leaf area (LA), leaf area index (LAI), root dry weight, root length, pod length, aboveground biomass yield, and straw yield. Grain yield was strongly and markedly related to all parameters except for the harvest index. The partial budget analysis revealed that the White Wonder Trailing with inoculation provided the highest net benefit of 67171.3 Ethiopian Birr (ETB) ha−1, with a marginal rate return of 1386.7%. Therefore, using Bradyrhizobium strain CP‐24 in combination with the White Wonder Trailing variety is highly recommended to increase cowpea yield and generate higher economic returns in the research sites and similar agroecological areas.

Intercropping on Mars: A promising system to optimise fresh food production in future martian colonies.

Future colonists on Mars will need to produce fresh food locally to acquire key nutrients lost in food dehydration, the primary technique for sending food to space. In this study we aimed to test the viability and prospect of applying an intercropping system as a method for soil-based food production in Martian colonies. This novel approach to Martian agriculture adds valuable insight into how we can optimise resource use and enhance colony self-sustainability, since Martian colonies will operate under very limited space, energy, and Earth supplies. A likely early Martian agricultural setting was simulated using small pots, a controlled greenhouse environment, and species compliant with space mission requirements. Pea (Pisum sativum), carrot (Daucus carota) and tomato (Solanum lycopersicum) were grown in three soil types ("MMS-1" Mars regolith simulant, potting soil and sand), planted either mixed (intercropping) or separate (monocropping). Rhizobia bacteria (Rhizobium leguminosarum) were added as the pea symbiont for Nitrogen-fixing. Plant performance was measured as above-ground biomass (g), yield (g), harvest index (%), and Nitrogen/Phosphorus/Potassium content in yield (g/kg). The overall intercropping system performance was calculated as total relative yield (RYT). Intercropping had clear effects on plant performance in Mars regolith, being beneficial for tomato but mostly detrimental for pea and carrot, ultimately giving an overall yield disadvantage compared to monocropping (RYT = 0.93). This effect likely resulted from the observed absence of Rhizobia nodulation in Mars regolith, negating Nitrogen-fixation and preventing intercropped plants from leveraging their complementarity. Adverse regolith conditions-high pH, elevated compactness and nutrient deficiencies-presumably restricted Rhizobia survival/nodulation. In sand, where more favourable soil conditions promoted effective nodulation, intercropping significantly outperformed monocropping (RYT = 1.32). Given this, we suggest that with simple regolith improvements, enhancing conditions for nodulation, intercropping shows promise as a method for optimising food production in Martian colonies. Specific regolith ameliorations are proposed for future research.

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.

A complex regulatory network governs the expression of symbiotic genes in Sinorhizobium fredii HH103.

The establishment of the rhizobium-legume nitrogen-fixing symbiosis relies on the interchange of molecular signals between the two symbionts. We have previously studied by RNA-seq the effect of the symbiotic regulators NodD1, SyrM, and TtsI on the expression of the symbiotic genes (the nod regulon) of Sinorhizobium fredii HH103 upon treatment with the isoflavone genistein. In this work we have further investigated this regulatory network by incorporating new RNA-seq data of HH103 mutants in two other regulatory genes, nodD2 and nolR. Both genes code for global regulators with a predominant repressor effect on the nod regulon, although NodD2 acts as an activator of a small number of HH103 symbiotic genes. By combining RNA-seq data, qPCR experiments, and b-galactosidase assays of HH103 mutants harbouring a lacZ gene inserted into a regulatory gene, we have analysed the regulatory relations between the nodD1, nodD2, nolR, syrM, and ttsI genes, confirming previous data and discovering previously unknown relations. Previously we showed that HH103 mutants in the nodD2, nolR, syrM, or ttsI genes gain effective nodulation with Lotus japonicus, a model legume, although with different symbiotic performances. Here we show that the combinations of mutations in these genes led, in most cases, to a decrease in symbiotic effectiveness, although all of them retained the ability to induce the formation of nitrogen-fixing nodules. In fact, the nodD2, nolR, and syrM single and double mutants share a set of Nod factors, either overproduced by them or not generated by the wild-type strain, that might be responsible for gaining effective nodulation with L. japonicus.

Effect of foliar application of micronutrients and urea on mungbean varieties

Experiment was carried out to at the Agronomy field of Patuakhali Science and Technology University (PSTU). The treatments comprised of four variety and three fertilizer including control. Varieties were V1= BINA Mung-8, V2=BARI mung-2, V3=BARI mung-5 and V4=BARI mung-6 and treatments were T0 = control, T1 =micro nutrient, T2= micronutrient and urea. The experiment was laid-out in the Randomized Complete Block Design (RCBD) with three replications. The maximum plant height was found at BARI mung-6 (29.7). Maximum nodule number was found at BARI mung-6 variety (5.90). The number of effective nodule was highest at BARI mung-6 variety (2.36). In case of no of seed per pod and 1000-seed weight, BARI mung-6 variety gave highest value and those were 11.25 and 70.5 g respectively. Maximum plant height, nodule number, number of effective nodule and number of pod per plant were found at T2 treatment. The pod length, seed per pod and 1000-seed; T2 treatment gave the highest value and those were 5.5 cm, 11.25 and 65.64 g respectively. In case of plant height, chlorophyll content, number of nodule, number of effective nodule, pod per plant, pod length, pod weight/m2, seed per pod and 1000-seed weight, combined effecr of BARI mung-6 x micronutrient and urea (T2) gave highest value and those were (29.95, 47.5, 6.17, 2.40, 6.20, 6.20, 76.75, 11.20) cm and 68.45 g respectively. This result revealed that mungbean variety BARI mung-6 and T2 treatment performed best in combination (V4T2).

Effects of biofertilizers, lime and inorganic NPSB fertilizers on nodulation, growth and yield of soybean (Glycine max L. Merrill) in Assosa Zone, Western Ethiopia

The productivity of soybean in Assosa Zone particularly in Assosa and Bambassi districts is very low due to poor soil fertility management practices which resulted in severe soil acidity and low N-fixing inoculant in the soil. Hence, this experiment was conducted during the main cropping season of 2019 and 2020 in Assosa and Bambassi districts to evaluate the effect of biofertilizers, lime, and inorganic NPSB fertilizers on nodulation, growth, and yield of soybean (Glycine max L. Merrill). Factorial combinations of four biofertilizer inoculants [without biofertilizer (B1), SB12 biofertilizer at the recommended rate of 500 g ha −1 (B2), MAR1495 biofertilizer at the recommended rate of 500 g ha−1 (B3) and SB12 plus MAR1495 biofertilizers at their recommended rates (B4); two lime rates named without lime (L1) and lime at 5 ton/ha (L2); two inorganic NPSB fertilizers NPSB at 9.5-23-3.5-0.05 (F1) and NPSB at 19-46-7-0.1 (F2) at their recommended rates for soybean] were laid out in a randomized complete block design (RCBD) with three replications. Effective nodules, leaf area index, and grain yield were collected and analyzed using SAS 9.1.3 version software. Results of the experiment showed that effective nodules per plant, leaf area index, and grain yield were affected by biofertilizers, lime, inorganic fertilizers, and their interactions significantly (p < 0.01) at both locations and years. Finally, the interaction of SB12 + MAR1495, lime at 5 t/ha and NPSB at 19-46-7-0.1, and the interaction of SB12, lime at 5 t/ha and NPSB at 19-46-7-0.1 gave the maximum grain yield at Assosa and Bambassi, respectively.

Effect of Chemical Mutagenesis on Salt Tolerance of Common Beans (Phaseolus vulgaris L.) Nodulating Rhizobium

The chemical mutation is one of the important factors in the enrichment of the salt resistance capacity of the rhizobium isolates. Therefore, this study focused on 10 isolates of rhizobium collected from soil samples of Babile, Hararghe region, Ethiopia. All the collected isolates turned into a moderately yellow, yellow, and deep yellow color in yeast extract mannitol agar medium (YEMA) containing bromothymol blue after 48 h of incubation. It indicated that all the isolates were acid-producing Rhizobia. Moreover, based on colony morphology and diameter, 70% of the isolates displayed large mucoid colonies, and 30% of the isolates showed large watery colonies in YEMA media. Among the 10 isolates, 9(90%), 9(90%), 6(60%), 6(60%), 2(20%), and 1(10%), were grown at different salinity levels such as 2%, 4%, 6%, 8%, 9% and 10% of NaCl, correspondingly. The most salt-resistant wild isolate was HUCR 6 collected from Babile soil grown at 10% NaCl salinity level. A total of six mutants were considered after chemical mutagenesis based on their capacity to survive in the extreme salinity levels (11 to 14%). Mutant isolates such as HUCRM 4, HUCRM 5, and HUCRM 6 were the most tolerant Rhizobium that grew at the salinity level of 11 to 14% NaCl. The most sensitive mutant isolate was HUCRM 10 followed by the isolates HUCRM 8 and HUCRM 9 was the next sensitive mutant Rhizobia that grew only at 11% of NaCl concentration. Compared to the Rhizobium wild isolates, the mutant isolates were observed to be more tolerant to a medium containing higher concentration of NaCl, as high as 11% to 14%. Besides, 80% of the mutant isolates demonstrated effective nodulation with the common beans. The mutant isolate (HUCRM 4) showed better performance in relation to root nodule performance of Rhizobium species and increased the plant biomass production. In this study, mutant isolates HUCRM 6, which is tolerated to 14% NaCl, and HUCRM 4, HUCRM 5, and HUCRM 6 isolates tolerated at 12% salinity level. Finally, based on their symbiotic efficiency and tolerance to extreme salt levels, these mutant isolates (HUCRM 4, HUCRM 5 and HUCRM 6) were encouraged to be used for the development of Rhizobium inoculants of common beans grown under extreme saline conditions. J. Bio-Sci. 30(2): 13-22, 2022

Increasing the Fertility and Productivity of Marginal Land by Planting Leguminous Plants

Background: Marginal land is dry land which has limited nutrient content so it has relatively low productivity. The development of marginal land use can be optimized with an ecosystem approach strategy through improving soil fertility. Planting leguminous plant species that can fix nitrogen from the atmosphere can increase soil fertility. Methods: This research was conducted to determine the ability of plants (A = Corn; B = Peanuts; C = Green Beans; D = Soybeans) to increase soil fertility and plant productivity. The experiment was designed in a randomized block design consisting of four treatments, each treatment was repeated four times. Soil fertility analysis was carried out before planting (pH, Carbon (%), Nitogen (%) and C/N ) and after planting (pH, Carbon (%), Nitogen (%) and C/N). Productivity (straw (kg/ha), seeds (kg/ha) and effective nodules. Results: The experimental results showed that the planting of legumes had a significant effect on increasing soil fertility and forage productivity, nodulation but lower legume seed production compared to maize

Selection of rhizobial strains differing in their nodulation kinetics under low temperature in four temperate legume species

AbstractBackgroundWinter climate change including frequent freeze‐thaw episodes and shallow snow cover will have major impacts on the spring regrowth of perennial crops. Non‐bloating perennial forage legume species including sainfoin, birdsfoot trefoil, red clover, and alsike clover have been bred for their adaptation to harsh winter conditions. In parallel, the selection of cold‐tolerant rhizobial strains could allow earlier symbiotic nitrogen (N) fixation to hasten spring regrowth of legumes.MethodsTo identify strains forming nodules rapidly and showing high N‐fixing potential, 60 rhizobial strains in association with four temperate legume species were evaluated over 11 weeks under spring soil temperatures for kinetics of nodule formation, nitrogenase activity, and host yield.ResultsStrains differed in their capacity to form efficient nodules on legume hosts over time. Strains showing higher nitrogenase activity were arctic strain N10 with sainfoin and strain L2 with birdsfoot trefoil. For clovers, nitrogenase activity was similar for control and inoculated plants, likely due to formation of effective nodules in controls by endophyte rhizobia present in seeds.ConclusionsSelection based on nodulation kinetics at low temperature, nitrogenase activity, and yield was effective to identify performant rhizobial strains for legume crops. The use of cold‐tolerant strains could help mitigate winter climatic changes.

Growth, yield, yield components, and grain qualities of groundnut (Arachis hypogaea L.) as affected by liming and phosphorus rates in southwest Ethiopia

Two field experiments were conducted in the main seasons of 2021/22 ​at the farmers' farm in two districts of southwest Ethiopia to investigate the effects of lime and phosphorus on groundnut yield and yield components, employing four levels of lime (0, 2, 4, and 6 ​t CaCO3 ha−1) and phosphorus (0, 46, 69, and 92 ​kg P2O5 ha−1) arranged in factorial RCBD design with three replications. Data on the yield and its components were collected and subjected to an ANOVA using SAS software. The result demonstrated that plant height, number of branches, canopy spread, and shelling percentage were affected significantly by liming while effective nodule number, total peg, matured pod, and pod yield of groundnut significantly influenced by the main factors and their interactions. The combined application of 4 ​t lime and 46 ​kg P2O5 ha−1 resulted in the highest number of effective nodules (147.23 plant−1), total pod (72.6 plant−1), mature pod (62.4 plant−1), pod yield (4.49 ​t ​ha−1), oil content (50.6%) and protein content (33.1%) whereas the lowest values of these parameters were seen in plots where neither lime nor phosphorus was applied. Therefore, it is advised that groundnut growers in the study areas, and similar agro-ecologies, apply the combination of 4 ​t lime and 46 ​kg P2O5 ha−1.

Effect of Various Microbial Inoculums on the Growth, Quality and Nutrient Uptake of Mung Bean (Vigna radiata L.)

A field experiment was conducted at Technology Park of Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut (UP) to study the Growth, Quality, and Nutrient Uptake of Mung Bean (Vigna radiata L.) as Influenced by Different Microbial Inoculums during the kharif season of 2020. The experiment including ten treatments was conducted in RBD design and replicated thrice. The maximum values of growth attributes viz., Root length (15.7 cm), Root weight (1.4:1.06 fresh/dry g/plant), Effective nodules (41.5 no./plant), Nodules dry weight (96.3 mg/plant) and Grain yield (1106 kg/ha), Quality i.e., Protein content (25.4%), Protein yield (279.7 kg/ha) and nutrient content and uptake viz., nitrogen, phosphorus and potassium were recorded under NPK Consortia +ZSB, each @ 20 ml/kg followed by NPK Consortia @ 20 ml/kg. This shows that NPK Consortia with ZSB have better adoptability in growth, yield and quality of mung bean.

PERTUMBUHAN TANAMAN KACANG TANAH YANG DIBERI BERBAGAI JENIS DAN TAKARAN PUPUK HIJAU PADA TANAH ULTISOL

This study aims to determine the effect of giving various types, doses of green manure and to determine the treatment that gives the best response on the growth of peanut plants on ultisol soils. This research was carried out at the Experimental Field Laboratory II and the Agrotechnology Laboratory of the UHO Faculty of Agriculture from April 2021 to February 2022. This study used a factorial randomized block design (RAK), namely the type of green manure (H) as the first factor consisting of 3 treatment: gamal leaves (H1), colopogonium (H2) and kirinyuh (H3) and the dose of green manure (T) as the second factor consisting of 4 levels of treatment: control (T0), 7.5 t ha-1 (T1), 15 t ha-1 (T2) and 22.5 t ha-1 (T3). The variables observed included stem diameter, number of leaves and nodules, leaf area, total leaf area, effective nodules, root dry weight and root loss ratio. The results showed that the application of various types and doses of green manure with kirinyuh (H3T3) was able to have a positive effect on increasing the growth of peanut plants grown on ultisol.

Effects of cowpea (Vigna unguiculata) inoculation on nodule development and rhizosphere carbon and nitrogen content under simulated drought

AimsInoculation with climate-adapted rhizobia is able to increase legume productivity in drought-prone regions of Sub-Saharan Africa. Enhanced nodulation might additionally affect plant-soil interactions and control rhizosphere carbon (C) and nitrogen (N) pools.MethodsWe investigated inoculation effects on nodulation and biological N2 fixation (BNF) of Vigna unguiculata and consequent effects on C and N pools in two Namibian soils. Three treatments (Bradyrhizobium sp.1–7 inoculant, non-inoculated, N-fertilised with 50 kg N ha−1) were applied in rhizoboxes at 45% and 20% maximum water holding capacity. Nodule development was photo-documented, and rhizobia-DNA sequences were identified. BNF was assessed by δ15N enrichment, and organic C and N pools were analysed in bulk and root adherent soil.ResultsPlant growth initially enhanced mineral N losses from the rhizosphere at flowering stage (6 weeks growth), but led to a re-increase of N, and organic C contents after ripening (10 weeks). Inoculation had no effect on nodulation and soil C and N pools, indicating that both soils contained sufficient indigenous rhizobia to allow effective nodulation. However, the inoculant strain was more competitive in establishing itself in the root nodules, depending on the local conditions, showing a need for regional adjustment of inoculation strategies.ConclusionWater stress was the main limitation for nodulation and, in combination with soil type, substantially affected rhizosphere and bulk soil C and N contents. The temporally enhanced rhizodeposition after ripening could be able to maintain soil C and N pools after legume cultivation.

The T6SS-Dependent Effector Re78 of Rhizobium etli Mim1 Benefits Bacterial Competition.

The genes of the type VI secretion system (T6SS) from Rhizobium etli Mim1 (ReMim1) that contain possible effectors can be divided into three modules. The mutants in them indicated that they are not required for effective nodulation with beans. To analyze T6SS expression, a putative promoter region between the tssA and tssH genes was fused in both orientations to a reporter gene. Both fusions are expressed more in free living than in symbiosis. When the module-specific genes were studied using RT-qPCR, a low expression was observed in free living and in symbiosis, which was clearly lower than the structural genes. The secretion of Re78 protein from the T6SS gene cluster was dependent on the presence of an active T6SS. Furthermore, the expression of Re78 and Re79 proteins in E. coli without the ReMim1 nanosyringe revealed that these proteins behave as a toxic effector/immunity protein pair (E/I). The harmful action of Re78, whose mechanism is still unknown, would take place in the periplasmic space of the target cell. The deletion of this ReMim1 E/I pair resulted in reduced competitiveness for bean nodule occupancy and in lower survival in the presence of the wild-type strain.