Effects of co-inoculation of Bradyrhizobium elkanii BLY3-8 and Streptomyces griseoflavus P4 on Rj4 soybean varieties

Co-inoculation of selected nitrogen-fixing bacteria with plant growth-promoting bacteria is the promising way for the improvement of soybean production through enhancing plant growth, nodulation, and N₂ fixation. Therefore, this experiment was conducted to study the effects of co-inoculation of Bradyrhizobium elkanii BLY3-8 with Streptomyces griseoflavus P4 on plant growth, nodulation, N₂ fixation, N uptake, and seed yield of Rj₄ soybean varieties. Two experiments with completely randomized design and three replicates were done in this study. N₂-fixation ability of soybean was evaluated by acetylene reduction activity (ARA) and relative ureide method. In the first experiment, synergetic effect in N₂ fixation and nodulation was occurred in co-inoculation treatment (BLY3-8 + P4) in Yezin-3 and Fukuyutaka. Based on these results, co-inoculation effect of BLY3-8 and P4 was assessed on Yezin-3 and Fukuyutaka varieties at three different growth stages, using Futsukaichi soil under natural environmental conditions. This study shows that co-inoculation of BLY3-8 and P4 significantly increased N₂ fixation at V6 stage; plant growth, nodulation, N₂ fixation, and N uptake at R3.5 stage; and shoot growth, N uptake, and seed yield at R8 stage, in Rj₄ soybean varieties compared with the control. Significant difference in plant growth, nodulation, N₂ fixation, N uptake, and yield between co-inoculation and control, not between single inoculation and control, suggests that there is a synergetic effect due to co-inoculation of BLY3-8 and P4.     

Selection of type A and type B strains for improving symbiotic effectiveness on non-Rj and Rj4 genotype soybean varieties

The selection of effective rhizobia for higher efficiency nitrogen fixation is one of the most important steps for inoculant production. Therefore, this experiment was conducted to select the most effective type A and type B strains for specific Rj-gene harboring soybean varieties and to test the symbiotic effectiveness of selected strains on different Rj-gene harboring soybean varieties. Screening experiments using the specific soybean varieties were done with a completely randomized design and three replications in this study. Evaluation of the effective Myanmar Bradyrhizobium strains for plant growth, nodulation and N₂ fixation were studied in pot experiments using sterilized vermiculite in the Phytotron (controlled-environmental condition). Then, a pot experiment was conducted using Futsukaichi soil in the screen house (natural environmental condition). The N₂ fixation ability of soybean was evaluated by acetylene reduction activity (ARA) and the relative ureide index method. In the first screening experiment, type A and type B strains with higher nitrogen fixation and proper nodulation on their respective soybean cultivars were selected for the next screening. In the second screening, Bradyrhizobium elkanii AHY3-1 (type A), Bradyrhizobium japonicum SAY3-7 (type A), B. elkanii BLY3-8 (type B) and B. japonicum SAY3-10 (type B) isolates, which showed higher nitrogen fixation and nodulation in Yezin-3 (Rj₄) and Yezin-6 (non-Rj), were selected for the next experiment. In the third screening experiment, SAY3-7 and BLY3-8, which had higher nitrogen fixing potential and proper nodulation, were selected as effective isolates. These two isolates were compatible with non-Rj and Rj₄ soybean varieties for nodulation and nitrogen fixation. Based on the results of the screening experiment, these two strains were tested for their symbiotic efficacy in Futsukaichi soil. This study shows that inoculation treatment of SAY3-7 and BLY3-8 significantly increased plant growth, nodulation, and N₂ fixation at the V6, R3.5 and R8 stages in Yezin-3 (Rj₄) and/or Yezin-6 (non-Rj), and the seed yield at R8 stage, in Yezin-3 (Rj₄) and Yezin-6 (non-Rj) soybean varieties compared with the control treatment. It can be concluded that SAY3-7 and BLY3-8 are suitable for inoculant production because of their higher nitrogen fixation ability, proper nodulation and better productivity of Myanmar soybean cultivars.     

Evaluation of effective Myanmar Bradyrhizobium strains isolated from Myanmar soybean and effects of coinoculation with Streptomyces griseoflavus P4 for nitrogen fixation

In order to substitute the use of chemical fertilizers in legume production, there is a need for the production of rhizobial inoculants which are capable of being used as biofertilizers. To achieve this, an effective symbiotic nitrogen (N) fixation between legumes and root nodule bacteria will be essential. Evaluation of effective Myanmar Bradyrhizobium (Jordan 1982) strains isolated from Myanmar soybean (Glycine max L. Merr.) and effects of coinoculation with Streptomyces griseoflavus Krainsky 1914 P4 for N fixation were studied in pot experiments using sterilized vermiculite and Hoagland solution in the Phytotron (25°C and 70% relative humidity) with completely randomized design and three replicates. N fixation ability of soybean was evaluated by acetylene reduction activity (ARA) by gas chromatography. It was found that MAS23 showed a relatively high degree of stability and a high level of ARA per plant on both Yezin-3 and Yezin-6 soybean varieties. In the symbiotic relationship between Bradyrhizobium strains and P4 experiments, the treatments consisted of six Bradyrhizobium strains (MAS23, MAS33, MAS34, MAS43, MAS48 and USDA110) and Streptomyces griseoflavus P4 were evaluated with four Myanmar soybean varieties (Yezin-3, Yezin-6, Hinthada and Shan Sein). In the Yezin-3 soybean variety, the best treatment for ARA per plant was found in the dual inoculation of P4 and MAS34. In the Yezin-6 soybean variety, the highest nodule dry weight was found in dual inoculation of P4 with MAS34 but the highest ARA per plant was observed in the dual inoculation of P4 and MAS23. On the other hand, single inoculation of MAS43 and coinoculation of P4 with MAS48 were significantly higher in N fixation of Hinthada, and coinoculation of P4 with MAS33 was significant improvement of ARA per plant (P < 0.05) in Shan Sein soybean.     

PLANT GROWTH PROMOTING RHIZOBACTERIA INCREASE GROWTH,YIELD AND NITROGEN FIXATION IN PHASEOLUS VULGARIS

Nitrogen (N) fixation by legume-Rhizobium symbiosis is important to agricultural productivity and is therefore of great economic interest. Growing evidence indicates that soil beneficial bacteria can positively affect symbiotic performance of rhizobia. The effect of co-inoculation with plant growth-promoting rhizobacteria (PGPR) and Rhizobium, on nodulation, nitrogen fixation, and yield of common bean (Phaseolus vulgaris L.) cultivars was investigated in two consecutive years under field conditions. The PGPR strains Pseudomonas fluorescens P-93 and Azospirillum lipoferum S-21 as well as two highly effective Rhizobium strains were used in this study. Common bean seeds of three cultivars were inoculated with Rhizobium singly or in a combination with PGPR to evaluate their effect on nodulation and nitrogen fixation. A significant variation of plant growth in response to inoculation with Rhizobium strains was observed. Treatment with PGPR significantly increased nodule number and dry weight, shoot dry weight, amount of nitrogen fixed as well as seed yield and protein content. Co-inoculation with Rhizobium and PGPR demonstrated a significant increase in the proportion of nitrogen derived from atmosphere. These results indicate that PGPR strains have potential to enhance the symbiotic potential of rhizobia.     

Enhanced soybean (Glycine max L.) plant growth and nodulation by Bradyrhizobium japonicum-SB1 in presence of Bacillus thuringiensis-KR1

Abstract

Nodulation and subsequent nitrogen fixation are important factors that determine the productivity of soybean (Glycine max L.). The beneficial effects of nodulation can be enhanced when rhizobial inoculation is combined with plant-growth-promoting bacteria (PGPB). The PGPB strain Bacillus thuringiensis-KR1, originally isolated from the nodules of Kudzu vine (Pueraria thunbergiana), was found to promote growth of soybean plants (variety VL Soya 2) under Jensen's tube and growth pouch conditions, when co-inoculated with Bradyrhizobium japonicum-SB1. Co-inoculation with Bacillus thuringiensis-KR1 (at a cell density of 10 cfu) provided the highest and most consistent increase in nodule number, shoot weight, root weight, root volume, and total biomass, over rhizobial inoculation and control, under both conditions. The results demonstrate the potential benefits of using nonrhizobial nodule occupants of wild legumes for the co-inoculation of soybean, with Bradyrhizobium japonicum-SB1, in order to achieve plant-growth promotion and increased nodulation.     

Effects of Rhizobium inoculation and magnesium application on growth and nodulation of soybean (Glycine max L.)

Abstract

Magnesium (Mg) deficiency is one of the major nutritional problems in tropic and subtropic areas, where the most soils are acidic. In this study, the effects of Mg application and Bradyrhizobium inoculation on growth, nodulation, symbiotic nitrogen (N) fixation as well as N nutrition status in soybean (Glycine max L.) were investigated in hydroponics under greenhouse conditions. With the increase of Mg up to 0.75?mM at low N and up to 0.5?mM at high N solutions, the dry weights of shoots, roots, and pod grain yield in soybean were increased, while further increase in Mg supply inhibited soybean growth. The availability of Mg was found to entail an improved uptake of N by plants and nodulation process in the root by Bradyrhizobium. Inoculation with rhizobial inoculants not only formed many nodules, but also increased soybean shoot, root biomass and yield, as well as plant N nutrient status.     

Combined Effect of Phosphate-Solubilizing Microorganisms,Rhizobium and Enterobacter on Root Nodulation and Physiology of Soybean (Glycine max L.)

Although phosphate-solubilizing microorganisms play a positive role in plant growth, their role in plant growth and root nodulation in combination with Rhizobium and Enterobacter has not been fully elucidated. Furthermore, only information exists regarding the effect of inoculation at successive stages of nodulation. The present study aimed to monitor the changes in the production of Indole acetic acid (IAA) and Gibberellin (GA₃) in the roots of soybean during and after nodulation (25 DAS and 40 DAS) and in the rhizosphere soil following inoculation with two different strains of phosphate-solubilizing microorganisms (PSM I, strain CA 18 and PSM II, strain 54RB), Enterobacter strain A and BradyRhizobium Japonicum strain Tal 377. The effects of inoculation on the available NO^?3, K, and P content of soil were studied at harvest. Beneficial effects of inoculation with Rhizobium, Enterobacter, and PSM I and II were obtained in all growth parameters of soybean. Co-inoculation resulted in maximum increase in IAA and GA content, plant biomass, root nodulation, number, weight and length of pods as compared with control (non-inoculated) and single-inoculation plants. The soil of the inoculated plants also showed higher IAA and GA content over.     

东北黑土区大豆生长、结瘤及产量对氮、磷的响应

氮肥和磷肥显著影响大豆的结瘤和产量。然而在土壤肥力较高、速效养分有效性差的东北地区,有关氮肥和磷肥施用量对大豆结瘤和产量影响的研究较少。本试验采用裂区田间试验,设置3个氮（N）水平（0、20 和 50 kg/hm2）和 3 个磷（P）水平（0、 20 和 40 kg/hm2）,研究氮、 磷及其交互作用对大豆生长发育、 结瘤特征及产量的影响。结果表明, 单施氮肥大豆生物量和产量随着施氮量的增加而增加,而根瘤数量、 干重、 大小和结瘤指数呈逐渐下降的趋势。单施磷肥促进大豆生物量、 产量、 根瘤数量、 干重、 大小和结瘤指数的增加,但其增幅低于施氮处理下的增幅。氮磷对大豆生长和产量促进作用高于单施氮和单施磷处理,但差异不显著;氮磷处理下的根瘤数量、 干重、 大小和结瘤指数低于单施磷处理;氮磷处理下N2（N 50 kg/hm2）处理下的大豆根瘤数量、 干重、 大小和结瘤指数高于N1处理（N 20 kg/hm2）下的,随着施磷量的增加大豆根瘤数量、 干重、 大小和结瘤指数增加,施磷能够抵消氮对大豆根瘤产生和形成的抑制。氮、 磷及其交互作用对大豆根瘤的影响都是直接的,并且不是通过促进大豆生长间接促进的。因此氮和磷均是限制东北地区大豆结瘤和产量的因素,但氮是主导因素。若要获得大豆高产,氮肥施用量需要控制在50 kg/hm2,磷肥在40 kg/hm2;但若想最大的发挥大豆的结瘤固氮功能,那么应该不施或者减少氮肥的施用量到20 kg/hm2,磷肥仍在40 kg/hm2。     

CO-INOCULATION OF SOYBEAN (GLYCINE MAX) WITH ACTINOMYCETES AND BRADYRHIZOBIUM JAPONICUM ENHANCES PLANT GROWTH,NITROGENASE ACTIVITY AND PLANT NUTRITION

The aim of this study was to determine the potential of the endophytic actinomycetes that produce plant growth promoters used as co-inoculants with Bradyrhizobium japonicum to promote the growth of soybean. These endophytes exhibited the potential to enhance plant growth, nitrogenase activity of root nodules and plant nutrient uptake. Co-inoculum of B. japonicum with Nocardia alba conferred the maximum yield of root and shoot dry weight. All single-inoculated actinomycetes strains had the ability to enhance plant growth. Noc. alba and Nonomuraea rubra increased total plant dry weight up to 2.14-fold and 2.11-fold, respectively, when compared to the uninoculated controls. Co-inoculations of B. japonicum with each of Noc. alba, Non. Rubra, and Actinomadura glauciflava increased acetylene reduction activity up to 1.7 to 2.7-fold. For plant mineral composition, all of co-inoculation treatments significantly increased the nutrient levels of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe) and zinc (Zn) within a soybean plant.     

Nutrients Uptake in Shoots and Biomass Yields and Roots and Nutritive Value of Zuri Guinea Grass Inoculated with Plant Growth-promoting Bacteria

ABSTRACT

The objective of this study was to evaluate the effects of plant growth promoting bacteria (PGPB) inoculation in Zuri guinea grass [Megathyrsus (syn. Panicum) maximus] on shoot dry weight (SDW) and root dry weight (RDW) yield, morphological compositions, number of tillers, and nutrients concentrations in SDW. The experiment was carried out under greenhouse conditions in a randomized block design consisting of eight treatments with five replicates. The inoculation with the Ab-V5 and Ab-V6 strains of Azospirillum brasilense and Pseudomonas fluorescens or co-inoculation with Rhizobium tropici and Ab-V6, with nitrogen (N) fertilization, as well as re-inoculations of the plants after cuttings were taken were evaluated. The plant growth-promoting bacteria and N fertilization promoted increases in SDW and RDW yield, tillers dry weight, relative chlorophyll index (RCI) and nutrients uptake in shoots of Zuri guinea grass. There were effects of re-inoculation the PGPB by P. fluorescens in shoots, N, magnesium (Mg) and boron (B) concentration in SDW.     

Effect of soil physical properties on soybean nodulation and N2 fixation at the early growth stage in heavy soil field in Hachirougata Polder,Japan

We studied the effect of the soil physical properties on soybean nodulation and N₂ fixation in the heavy soil of an upland field (UF) and an upland field converted from a paddy field (UCPF) in the Hachirougata polder, Japan. Seeds of the soybean cultivar Ryuho were sown in each field with or without inoculation of Bradyrhizobium japonicum A1017. The soybean plants were sampled at 35 (V3) and 65 (Rl) d after sowing (DAS), and then nodulation and the percentage of N derived from N₂ fixation in the xylem sap were determined. The soil physical properties were different between UF and UCPF, especially the air permeability and soil water regime. Nodule growth was restricted in UCPF irrespective of rhizobial inoculation, though rhizobial infection was not inhibited by the unfavorable soil physical conditions. Soybean plant growth was closely related to the nodule mass and N₂ fixation activity, and the inoculation of a superior rhizobium strain was effective only at 35 DAS. These results indicate that soybean nodulation and N₂ fixation was considerably affected by the physical properties of heavy soil, and that it is important to maintain the N₂ fixation activity and inoculate the soybean plants with a superior rhizobium strain at a later growth stage in order to increase soybean production in heavy soil fields.     

Impact of single and co-inoculations with Rhizobial and PGPR isolates on chickpea (Cicer arietinum) in cereal-growing zone soil

Strains isolated from chickpea (Cicer arietinum L.) rhizospheric soil from selected sites in Algeria were screened for their plant-growth-promoting potential, for indole acetic acid production and P solubilization ability. Then, we selected native rhizobial strains with high nitrogen-fixing potential. On the basis of their efficiency under controlled conditions, two plant-growth-promoting rhizobacteria (PGPR) isolates and three nodulating bacteria were selected. Then, the effect of single PGPR isolates inoculation was compared to their combination with rhizobial inoculants on plant growth, on native cereal-growing soils under greenhouse conditions. No effects were observed on chickpea yield by using rhizobial inoculation alone, nor by PGPR-rhizobial co-inoculation on two soils presenting weak and no nodulation pattern in natural conditions. Only PGPR inoculation improved growth of plants on soil with no nodulation pattern. These findings emphasized inoculation on native soils at a little scale before large assays on field because no one could predict inocula behavior with native soil microflora.     

Co-inoculation of selected nodule endophytic rhizobacterial strains with Rhizobium tropici promotes plant growth and controls damping off in common bean

Production of common bean(Phaseolus vulgaris)is limited by the occurrence of damping off(rhizoctoniosis),which is caused by the fungus Rhizoctonia solani.However,the co-inoculation of plant growth-promoting rhizobacteria(PGPR)involved in biological control along with diatomic nitrogen(N2)-fixing rhizobia can enhance N nutrition and increase production.In this context,finding microorganisms with synergistic effects that perform these two roles is of fundamental importance to ensure adequate yield levels.The aim of this study was to evaluate the effects of co-inoculation of nodule endophytic strains of the genera Bacillus,Paenibacillus,Burkholderia,and Pseudomonas with Rhizobium tropici CIAT 899,an N2-fixing rhizobial strain,on the biocontrol of damping off and growth promotion in common bean plants.Greenhouse experiments were conducted under axenic conditions using the common bean cultivar Pérola.The first experiment evaluated the potential of the 14 rhizobacterial strains,which were inoculated alone or in combination with CIAT 899,for the control of R.solani.The second experiment evaluated the ability of these 14 rhizobacterial strains to promote plant growth with three manners of N supply:co-inoculation with CIAT 899 at low mineral N supply(5.25 mg N mL^-1),low mineral N supply(5.25 mg N mL^-1),and high mineral N supply(52.5 mg N mL^-1).The use of rhizobacteria combined with rhizobia contributed in a synergistic manner to the promotion of growth and the control of damping off in the common bean.Co-inoculation of the strains UFLA 02-281/03-18(Pseudomonas sp.),UFLA 02-286(Bacillus sp.),and UFLA 04-227(Burkholderia fungorum)together with CIAT 899 effectively controlled damping off.For the common bean,mineral N supply can be replaced by the co-inoculation of CIAT 899 with plant growth-promoting strains UFLA 02-281/02-286/02-290/02-293.Nodule endophytes UFLA02-281/02-286 are promising for co-inoculation with CIAT 899 in the common bean,promoting synergy with rhizobial inoculation and protection against disease.     

Growth,nutrient uptake and yield parameters of chickpea (Cicer arietinum L.) enhance by Rhizobium and Azotobacter inoculations in saline soil

Abstract

A field experiment was conducted during two consecutive growing seasons (2013 and 2014) to evaluate the effects of inoculations with Rhizobium and Azotobacter on the growth and yield of two chickpea (Cicer arietinum L.) varieties under saline (5.8 dS m^?1) arid condition. The single treatment of either Rhizobium or Azotobacter exhibited to promote the growth of chickpea to some level, however, co-inoculation produced more effects and increased the shoot dry weight (30.3 and 26.4%), root dry weight (17.5 and 26.3%), nodule number (79.1 and 43.8 piece per plant), nitrogen content in roots (9.62 and 10.9%), in shoots (12.6 and 8.3%) and seed protein (7.1 and 4.3%) in both Flip06-102 and Uzbekistan-32 chickpea varieties compared to the control. Our studies showed that the highest yield response of 429 (27.9%) and 538 (23.9%) kg?ha^?1 over the control was revealed by the co-inoculation with Rhizobium and Azotobacter inoculants in Flip 06-102 and Uzbekistan-32, respectively. A new introduced Flip 06-102 chickpea variety was more salt tolerant and had higher root nodulation than the local Uzbekistan-32 chickpea variety. Nitrogen (N), phosphorus (P), and potassium (K) contents in the shoots and roots were significantly (p?Rhizobium plus Azotobacter could be applied to improve the vegetative growth and yield of chickpea and to alleviate the effects of salt stress.     

Co-inoculations of arbuscular mycorrhizal fungi and rhizobia under salinity in alfalfa

Alfalfa (Medicago sativa L.) is cultivated in arid and semi-arid regions where salinity is one of the main limiting factors for its production. Thus, this experiment was conducted to evaluate the efficacy of arbuscular mycorrhizal fungus (AMF), Glomus mosseae, alfalfa rhizobia Sinorhizobium meliloti (R) seed inoculation in the development of salinity tolerance of different alfalfa cultivars (Rehnani, Pioneer and Bami) under a variety of salinity levels. The results revealed that under non-stress condition, root mycorrhizal infection, nodulation (the number and weight of nodules per plant), potassium (K), calcium (Ca), phosphorus (P), zinc (Zn), copper (Cu) and magnesium (Mg) contents of the root and shoot, the value of the K/Na ratio, protein [calculated from the nitrogen (N) content] and proline contents of the shoot and the alfalfa yield were found to be the highest while Na contents of the root and shoot were seen to be the lowest when seeds were double inoculated followed by mycorrhizae, rhizobium and control treatments, respectively. Similarly, under salinity condition, the greatest amounts of mycorrhizal infection, nodulation, root and shoot P contents, the value of K/Na ratio, the shoot proline content and the root Ca content were enhanced with the least amount of leaf Na content related to the cases of seeds which were double inoculated, followed by mycorrhizae, rhizobium and control treatments respectively. The results suggested that inoculation of alfalfa seed with AMF or R, especially double inoculation, causes a considerable increase in alfalfa yield under both saline and non-saline conditions by increasing colonization, nodulation and nutrient uptake.     

基因型影响磷镁互作下大豆生长及根瘤和菌根性状

  【目的】  明确施加镁肥在不同磷处理的土壤上对不同基因型大豆生长及根瘤和菌根性状的影响。  【方法】  田间试验采用三因素试验设计,设置施P₂O₅ 40 kg/hm2 (P40)和100 kg/hm2 (P100)两个水平,施MgO 0 kg/hm2 (Mg0)和75 kg/hm2 (Mg75)两个水平,磷高效基因型粤春03-3 (YC03-3)和磷低效基因型本地2号(BD2)两个大豆基因型。测定了大豆植株干重、单株结荚数、根系性状、根瘤性状、菌根侵染率以及植株氮、磷、镁含量。  【结果】  P100处理显著增加了两个大豆基因型的植株干重、单株结荚数、总根长、根表面积和体积以及植株氮、磷、镁积累量。施用镁肥,YC03-3在P40和P100处理下植株干重、单株结荚数、植株氮和镁积累量均显著增加,在P100条件下植株磷积累量以及根表面积、根体积、根平均直径显著增加;BD2在P40和P100处理下植株镁积累量显著增加,P40条件下植株氮积累量显著增加。磷和镁处理显著影响大豆与有益微生物的共生。P40条件下,两个大豆基因型的根瘤数和根瘤干重在Mg0和Mg75处理间无显著差异;P100条件下Mg75处理BD2和YC03-3的根瘤数分别较Mg0处理增加了135%和178%,根瘤干重分别增加了308%和197%。Mg0条件下P40处理YC03-3的菌根侵染率较P100增加了31.6%;Mg75条件下P40处理的BD2菌根侵染率较P100增加了15.0%。P40条件下,Mg75提高了BD2菌根侵染率16.3%;P100条件下,Mg75提高了YC03-3菌根侵染率32.1%。主成分分析发现,P100条件下,Mg0与Mg75处理之间差异显著,而P40条件下镁处理之间差异不明显。  【结论】  增施磷肥显著促进了两个大豆基因型的生长,改善了植株氮、磷、镁养分状况。增施镁肥可增加磷高效大豆基因型YC03-3的地上部和根部干重、单株结荚数、植株氮积累量,对磷低效型基因BD2没有显著作用。YC03-3的根瘤密度对施磷和施镁响应较BD2显著。BD2的菌根侵染率在低磷条件下对施镁的反应敏感,而YC03-3的菌根侵染率在P100条件下对施镁反应敏感。由此可见,磷和镁养分之间的互作效应受到大豆基因型的影响。     

Microbial and chemical sources of phosphorus supply modulate the yield and chemical composition of essential oil of rose-scented geranium (Pelargonium species) in sodic soils

Rose-scented geranium (Pelargonium sp.) is a highly valued aromatic crop. Its growth is limited by soil salinity and sodicity stress. Arbuscular mycorrhizal (AM) fungus, phosphate-solubilizing bacteria (PSB), and P fertilizers may enhance the growth and secondary metabolism in geranium plants. In this context, a pot experiment was conducted to study the effects of PSB, AM fungi (Glomus intraradices), and P fertilizer on the yield, chemical composition of essential oil, and mineral element acquisition of geranium. The dry matter yield of shoot and essential oil yield, and mineral element (P, K, Ca, Mg, Na, Fe, Cu, and Zn) uptake in shoot tissues of geranium were significantly increased by the inoculation with AM fungi, co-inoculation with AM fungi and PSB, and P fertilization as compared to control. While the co-inoculation of geranium with AM fungi and PSB significantly enhanced the content of the monoterpenes such as citronellol, geraniol, geranial, and a sesquiterpene (10-epi-γ eudesmol), the P fertilization only enhanced the content of a sesquiterpene, 10-epi-γ eudesmol in the volatile oil. We conclude that the co-inoculation of PSB and AM fungi could be the best natural alternative to phosphate fertilizers to enhance the yield and quality of essential oil from geranium plants grown in sodic soils.     

Synergistic effect of inoculating plant growth-promoting Pseudomonas spp. and Rhizobium leguminosarum-FB1 on growth and nutrient uptake of rajmash (Phaseolus vulgaris L.)

Plant growth-promoting bacteria (PGPB) Pseudomonas lurida-NPRp15 and Pseudomonas putida-PGRs4 possessing multiple plant growth-promoting traits were isolated from rhizoplane of pea and rhizosphere of garlic, respectively. The effects of individuals and combinations of Pseudomonas spp. with effective root nodulating symbiotic nitrogen fixing Rhizobium leguminosarum-FB1 on plant growth, nutrient uptake and yield of the rajmash plant were studied under greenhouse conditions. Bacterial inoculation resulted in significantly higher values for plant dry biomass, N, P, K, Zn and Fe contents as compared to the uninoculated control. Furthermore, dual inoculation of P. lurida-NPRp15 with R. leguminosarum-FB1 significantly increased root and shoot dry weight, nodulation, nutrient uptake, pod yield, and nutrient content of pods of rajmash VL63 compared to controls, single and triple inoculation. The results of the study indicate the potential of harnessing the benefit of plant growth-promoting and nitrogen-fixing microorganisms to improve the growth and yield of rajmash.     

Study on the Effects of Organic and Inorganic Nitrogen Fertilizer on Yield,Yield Components,and Nodulation State of Chickpea (Cicer arietinum L.)

To study the effects of organic and inorganic nitrogen (N) on yield and nodulation of chickpea (Cicer arietinum L.) cv. ILC 482, a spilt-plot experiment based on randomized complete block design with four replications was conducted in 2008 at the experimental farm of the Agriculture Faculty, University of Mohaghegh, Ardabili. Experimental factors were inorganic N fertilizer at four levels (0, 50, 75, and 100 kg ha^?1) in the main plots that applied in the urea form, and two levels of inoculation with Rhizobium bacteria (with and without inoculation) as subplots. Nitrogen application and Rh. inoculation continued to have positive effects on yield and its attributes. The greatest plant height, number of primary and secondary branches, number of pods per plant, number of filled and unfilled pods per plant, number of grains per plant, grain yield, and biological yield were obtained from the greatest level of N fertilizer (100 kg urea ha^?1) and Rh. inoculation. Application of 75 and 100 kg ha^?1 urea showed no significant difference in these traits. Furthermore, the greatest rate of N usage (100 kg urea ha^?1) adversely inhibited nodulation of chickpea. Number and dry weight of nodules per plant decreased significantly with increasing N application rate. The lowest values of these traits recorded in application of 100 kg ha^?1 urea. Results indicated that application of suitable amounts of N fertilizer (i.e., between 50 and 75 kg urea ha^?1) as starter can be beneficial to improve nodulation, growth, and final yield of inoculated chickpea plants.     

Nitrogen fixation and CO2 exchange in soybeans (Glycine max L.) inoculated with mixed cultures of different microorganisms

N₂ fixation, photosynthesis of whole plants and yield increases in soybeans inoculated with mixed cultures of Bradyrhizobium japonicum 110 and Pseudomonas fluorescens 20 or P. fluorescens 21 as well as Glomus mosseae were found in pot experiments in gray forest soil carried out in a growth chamber. The effects of pseudomonads and vesicular-arbuscular (VA) mycorrhizal fungus on these parameters were found to be the same. Dual inoculation of soybeans with mixed cultures of microorganisms stimulated nodulation, nitrogenase activity of nodules and enhanced the amount of biological nitrogen in plants as determined by the ¹⁵N dilution method in comparison to soybeans inoculated with nodule bacteria alone. An increased leaf area in dually infected soybeans was estimated to be the major factor increasing photosynthesis. P. fluorescens and G. mosseae stimulated plant growth, photosynthesis and nodulation probably due to the production of plant growth-promoting substances. Increasing phosphorus fertilizer rates within the range of 5–40 mg P 100 g^-1 1:1 (v/v) soil: sand in a greenhouse experiment led to a subsequent improvement in nodulation, and an enhancement of N₂ fixation and yield in soybeans dually inoculated with B. japonicum 110 and P. fluorescens 21. These indexes were considerably higher in P-treated plants inoculated with mixed bacterial culture than in plants inoculated with nodule bacteria alone.