Arbuscular Mycorrhizal Fungus Glomus Mosseae Research Articles

Coinoculation of arbuscular mycorrhizal fungi and rhizobia stimulates atrazine dissipation by changing the atrazine-degrading bacterial community at the soil aggregate scale

As a potential low-cost and environmentally friendly strategy, bioremediation of herbicide polluted soil has attracted increasing attention. However, there is a lack of knowledge regarding the response of the atrazine-degrading bacterial community to coinoculation of arbuscular mycorrhizal (AM) fungi and rhizobia for atrazine dissipation. In this study, a pot experiment was conducted with AM fungi Glomus mosseae (AM), rhizobia Rhizobium trifolii TA-1 (R) and their coinoculation (AMR) with atrazine. In each treatment, the atrazine-degrading bacterial community of four soil size aggregates, namely large macroaggregates (LMa), small macroaggregates (SMa), microaggregates (Mia) and primary particles (P) were investigated. The results showed that the atrazine residue concentration was lowest in AMR, and that in LMa was also significantly lower than that in the other smaller aggregate sizes. Overall, inoculation, the aggregate fraction and their interaction had significant effects on soil TN, SOC, AP and pH. For the atrazine-degrading bacterial community, the Chao1 index increased with decreasing particle size, but the Shannon index decreased. Moreover, the abundances of the dominant atrazine-degrading bacterial genera Arthrobacter, Bacillus, Marmoricola and Nocardioides in the Mia and P particle size groups were greater than those in the LMa and SMa groups in each treatment. The bacterial communities in the Mia and P particle sizes in each treatment group were more complex. Therefore, coinoculation of AM fungi and rhizobia stimulated atrazine dissipation by changing the atrazine-degrading bacterial community, and the response of the atrazine-degrading bacterial community to each aggregate size varied depending on its distinct soil physicochemical properties.

Combined Effects of Microbial Inoculation and Activated Carbon/Biochar on the Accumulation and Transfer of Nutrients and Potentially Toxic Metals in Maize Plants Grown on a Contaminated Soil

ABSTRACT This study was conducted in a greenhouse pot experiment to assess the effects of biochar (BC) or activated carbon (AC) alone or in combination with arbuscular mycorrhizal fungus (AMF) Glomus mosseae or acid-producing bacteria (BA) Bacillus polymyxa on plant growth, EDTA-extractable Cd and Pb, and contents of heavy metals (Cd and Pb) and nutrients (Ca, Mg, K, and P) in maize (Zea mays L.) grown on sewage wastewater contaminated soil. The results showed that most treatments with BC, AC, or its co-application with microbial inoculation led significantly to greater nutrient uptake and promoted growth of maize than non-treated plants. Additionally, the soil additives used decreased the amounts of EDTA-extractable Cd (by 28.7%-100%) and Pb (by 22.8%-94.3%). The applied treatments caused significant decreases in Cd concentrations and the bioconcentration factor (BCF) of Zea mays. The highest shoot Cd reduction was observed for AC (53%), followed by AC+BA (36.9%) > AMF (34.5%) > AC+AMF (28.5) > BA (28.3%) > BC+BA (26.1%) > BC (22.7%). However, more Cd was accumulated in the roots of plants treated with AMF by 63.7% with a lower value of translocation factor (TF) compared to control soil. In contrast, the treatments increased the levels of Pb in the maize plants, and BC coupled with AMF showed the greatest Pb accumulation. It could be concluded that the investigated additives can be applied as immobilizing agents for Cd in the soil but maize plants as phytoextractants for both metals in sewage-contaminated soil are not feasible, as indicated by insufficient phytoextraction efficiency.

Promotion effect of AM fungi and rhizobia co-inoculations on alfalfa (Medicago Sativa L.) growth

Arbuscular mycorrhizal fungi (AMF) and rhizobia have been widely used in agriculture in recent years to increase production, reduce fertilizer consumption and control plant diseases. However, it is unclear whether there are differences in the effects of AMF and rhizobia inoculation alone and in combination. In this study, alfalfa seedlings were inoculated with AMF Glomus mosseae (G.m), Glomus intraradices (G.i) and co-inoculated with AMF and rhizobia Sinorhizobium meliloti (S.m) before being transplanted outdoors. The growth characteristics, fine root yield and fine root death of alfalfa were measured throughout the experiment, and the results showed that co-inoculation with AMF and rhizobia promoted alfalfa growth, while increasing plant height, branch number and total biomass. However, the growth promoting effects of AMF and rhizobia differed; AMF inoculation displayed no advantage over S.m inoculation in increasing aboveground biomass (P > 0.05) but did lead to an increase in underground biomass (P < 0.05). Compared with that observed following the single inoculations with G.m or S.m, the annual fine root production following co-inoculation with G.m and S.m increased by 15.38% and 47.06%, respectively, although there was less effect following co-inoculation with G. i and S.m. These results indicated that there was mutual selectivity and interaction between AMF and rhizobia. G.m and S.m inoculation treatment has a positive effect on alfalfa growth, on the one hand, it is because that AMF-Rhizobia synergically promoted alfalfa root system to absorb nutrients (N), then improve the plant growth, on the other hand, their vaccination can reduce the death of alfalfa fine roots, significantly improve the alfalfa biomass of underground part.

Morphological characterization and response of red flower rag leaf (Crassocephalum crepidioides Benth S. Moore) to organic and inorganic fertilizers and arbuscular mycorrhizal fungus

Red flower rag leaf (Crassocephalum crepidioides) is one of the underutilized vegetables consumed globally. Pot trials were conducted to characterize 15 morphologically distinct accessions of C. crepidioides and assess the effects of treatment combinations of eggshell, NPK 15:15:15, poultry manure and arbuscular mycorrhizal fungus(Glomus mosseae) as soil amendments on growth and yield-related characters of C. crepidioides. Thereafter, 48 seedlings of the best performing accession were transplanted into perforated polythene bags filled with 7 kg of heat-sterilized soil. The experiment was laid out in a completely randomized design with three replicates. Treatment combinations were incorporated into in the polythene bags 1 week after transplanting, while control plants received no amendments. The results showed that accession NH/GKB-15 had the highest plant height (29.83 cm), stem length (27.67 cm), number of leaves (15) and length of internode at node 3 (1.13 cm) and node 4 (1.17 cm). The growth and yield characters of this best performing accession (NH/GKB-15) in response to soil amendments showed that poultry manure produced the tallest plants (55.17 cm), longest and widest stems (48.35 and 0.66 cm), longest and widest leaves (16.39 and 6.26 cm, respectively), and higher number of inflorescence (2.13). With NPK 15:15:15 the seedlings did not survive. Poultry manure should therefore be utilized for better plant nutrition and faster growth of C. crepidioides seedlings as well as for safer consumption of the leafy vegetable.

Effect of single or dual inoculation of the arbuscular mycorrhizal fungus Glomus mosseae and root-nodulating rhizobacteria on reproduction of the burrowing nematode Radopholus similis on non-leguminous and leguminous banana intercrops

The bio-protective effect of either single or dual mycorrhizal (AMF) and rhizobial colonisation of the roots of non-leguminous and leguminous banana intercrops differing in host response to Radopholus similis on the reproduction of this important migratory endoparasitic nematode was examined. Included in the study were sorgho-Sudan grass (good R. similis host), sweet potato and common bean (intermediate hosts), soybean and sunn hemp (poor hosts), and marigold (non-host). Significant plant growth-promoting effect of single AMF and rhizobial colonisation in the good and intermediate R. similis hosts sorgho-Sudangrass (AMF) and common bean (AMF and rhizobium), respectively, was observed whereas this plant growth-promoting effect was absent in the other intercrops with the exception of sunn hemp with significant plant growth-promoting effect of AMF colonisation on fresh root weight. An additive plant growth-promoting effect of dual AMF and rhizobial colonisation (on fresh shoot weight) was only observed in the poor R. similis host soybean. Single AMF and rhizobial colonisation also resulted in a significant bio-protective effect against R. similis in sorgho-Sudangrass (AMF), sweet potato cv. Inzovu (AMF) and common bean (AMF and rhizobium). The growth-promoting and bio-protective effects of AMF colonisation were clearly present in the good and intermediate R. similis hosts with moderate to high relative mycorrhizal dependency (RMD) values ranging from 47% (sorgho-Sudangrass) to 65% (common bean) but absent in the intermediate R. similis host sweet potato, which had a negative RMD value, and in the poor and non- R. similis hosts. Overall, no suppressive effect of R. similis infection on AMF and rhizobial colonisation was observed except in soybean and sunn hemp in which AMF colonisation was significantly reduced.

Mycorrhizal fungi enhance flooding tolerance of peach through inducing proline accumulation and improving root architecture

This study aimed to evaluate the effect of an arbuscular mycorrhizal fungus (AMF) Glomus mosseae on plant growth, root architecture, and proline metabolism in roots of peach (Prunes persica L.) under non-flooding and flooding conditions. The 12-day flooding dramatically inhibited root colonisation of G. mosseae, but induced a large number of extraradical mycelia. Although the flooding treatment also relatively inhibited growth and root architecture of peach, the mycorrhizal fungal inoculation dramatically increased shoot and root biomass, plant height, stem diameter, number of 1&lt;sup&gt;st&lt;/sup&gt;- and 2&lt;sup&gt;nd&lt;/sup&gt;-order lateral roots, root total length (mainly 0–1 cm and &amp;gt; 3 cm long), root surface area, and root volume under flooding. The study also revealed distinctly higher proline accumulation in the roots of mycorrhizal plants than non-mycorrhizal plants under both non-flooding and flooding conditions, accompanied by higher Δ&lt;sup&gt;1&lt;/sup&gt;-pyrroline-5-carboxylate synthase (P5CS) activity and lower δ-ornithine transaminase and proline dehydrogenase activities. In addition, the PpP5CS1 gene expression was up-regulated by flooding and mycorrhization. This study concluded that mycorrhizal fungi enhanced flooding tolerance of peach through inducing proline accumulation and improving root architecture.

Role of rhizospheric microorganisms in mitigating the adverse effect of salinity stress in Plantago ovata growth, biochemical and photosynthetic traits

ABSTRACT This pot experiment was carried out to investigate the efficiency of plant rhizospheric microorganisms (PRMs) to counteract salinity stress in Plantago ovata. The treatments included soil salinity (2.5 (as control), 5 and 10 dS m−1), arbuscular mycorrhizal fungi (Control, Glomus mosseae, Rhizophagus intraradices and Funneliformis mosseae) and phosphate solubilizing bacteria (Control and Pseudomonas fluorescens). The highest amount of growth and yield parameters, relative water content (RWC), potassium (K+) and phosphorus (P) concentration, photosynthetic traits (chlorophyll a and b, carotenoid, maximal efficiency of PSII (fv/fm), variable fluorescence to initial fluorescence (fv/f0) and stomatal conductance (gs)), antioxidant enzymes and the lowest sodium (Na+) concentration, malondialdehyde (MDA) and electrolyte leakage were observed in the plants treated with mixture of Rhizophagus intraradices and Pseudomonas fluorescens under all salinity levels. Although all previously mentioned traits significantly and severely decreased under salinity stress, mucilage percentage, electrolyte leakage and Na+ concentration were increased under salinity levels. In conclusion, the results suggested that inoculation of AMF (particularly Rhizophagus intraradices) in combination with Pseudomonas fluorescens by the accumulation of proline along with decreased electrolyte leakage, maintenance of relative water content in leaves and selective uptake of K+ ions could overcome detrimental effects of salinity stress in isabgol. Abbreviations AMF: arbuscular mycorrhizal fungi; APX: ascorbate peroxidase; CAT: catalase; Chl: chlorophyll; CAR: carotenoids; ECe: electrical conductivity of soil saturation extract; EL: Electrolyte leakage; Fv/Fm: maximal efficiency of PSII; gs: stomatal conductance; Fv/F0: variable fluorescence to initial fluorescence; K+: potassium; MDA: malondialdehyde; Na+: Sodium; PGPR: plant growth-promoting rhizobacteria; P: phosphorus; PRM: plant rhizospheric microorganisms; PSB: phosphate solubilizing bacteria; RWC: relative water content; SOD: superoxide dismutase

The effects of biological, chemical, and organic fertilizers application on root growth features and grain yield of Sorghum

To investigate the effect of some biological and chemical fertilizers on the root physiological and growth indexes and also Sorghum grain yield, this study was carried out in randomized complete block design with three replicates. The treatments of the study included (1) arbuscular mycorrhizal fungus Glomus mosseae + vermicompost, (2) mycorrhiza fungus + Nitroxin, (3) mycorrhiza fungus+ Rhizobium sp., (4) mycorrhiza fungus + NPK chemical fertilizer (40-40-20), (5) mycorrhiza fungus, and (6) control treatment. The highest root colonization rate and specific root length were observed in the co-inoculation with mycorrhiza + Nitroxin treatment. The other root growth parameters were observed at the mycorrhiza + vermicompost treatment. Also the highest rate of Sorghum physiological growth indexes root such as root area index and net assimilation rate were belonged to the co-inoculation of mycorrhiza + Nitroxin treatment. The highest root growth rate and root relative growth rate were obtained in the mycorrhiza + vermicompost treatment. So it can be concluded that biological fertilizers can be used as an appropriate alternative for chemical fertilizers in sustainable agriculture system.

Arbuscular mycorrhizal fungi combined with exogenous calcium improves the growth of peanut (Arachis hypogaea L.) seedlings under continuous cropping

The growth and yield of peanut are negatively affected by continuous cropping. Arbuscular mycorrhizal fungi (AMF) and calcium ions (Ca2+) have been used to improve stress resistance in other plants, but little is known about their roles in peanut seedling growth under continuous cropping. This study investigated the possible roles of the AMF Glomus mosseae combined with exogenous Ca2+ in improving the physiological responses of peanut seedlings under continuous cropping. G. mosseae combined with exogenous Ca2+ can enhance plant biomass, Ca2+ level, and total chlorophyll content. Under exogenous Ca2+ application, the Fv/Fm in arbuscular mycorrhizal (AM) plant leaves was higher than that in the control plants when they were exposed to high irradiance levels. The peroxidase, superoxide dismutase, and catalase activities in AM plant leaves also reached their maximums, and accordingly, the malondialdehyde content was the lowest compared to other treatments. Additionally, root activity, and content of total phenolics and flavonoids were significantly increased in AM plant roots treated by Ca2+ compared to either G. mosseae inoculation or Ca2+ treatment alone. Transcription levels of AhCaM, AhCDPK, AhRAM1, and AhRAM2 were significantly improved in AM plant roots under exogenous Ca2+ treatment. This implied that exogenous Ca2+ might be involved in the regulation of G. mosseae colonization of peanut plants, and in turn, AM symbiosis might activate the Ca2+ signal transduction pathway. The combination of AMF and Ca2+ benefitted plant growth and development under continuous cropping, suggesting that it is a promising method to cope with the stress caused by continuous cropping.

Influence of Tomato Plant Mycorrhization on Nitrogen Metabolism, Growth and Fructification on P-Limited Soil

The application of mycorrhizal fungi in agricultural soils as bio-fertilizers is going to be established as an agronomic practice for enhancing crop nutrients acquisition and production. In this work, the effects of tomato root colonization by arbuscular mycorrhizal fungus Glomus mosseae, on nitrogen metabolism, fructification and environmental sustainability without P soil fertilization have been studied. At the harvesting fruit stage, the mycorrhizal (M) plants present a significantly higher concentration of mineral nutrients and organic nitrogen compounds. In particular, GLU, GLN, ASP and ASN have risen about 35% more than non-mycorrhizal (NM) plants. Tomato root mycorrhization improved nitrogen metabolism in plants, too by increasing the nitrate reductase and the glutamine synthetase enzymatic activity. Moreover, mycorrhization affects many aspects of vegetative and reproductive growth. In particular, the fruit production turns from inoculated (M) plants into non-inoculated (NM) plants, rising up to 50%.

Improving plant growth and alleviating photosynthetic inhibition from salt stress using AMF in alfalfa seedlings

ABSTRACT The effects of arbuscular mycorrhizal fungi Glomus mosseae (+AMF) on the growth, nutrient uptake and leaf photosynthetic characteristics of alfalfa (Medicago sativa) under salt stress were studied. In alfalfa, 100 mM salt stress had no obvious effect on plant growth, nutrient content and photosynthetic capacity, however, 200 mM salt stress significantly inhibited biomass accumulation and NPK uptake. In addition, 200 mM salt stress led to decreased photosynthetic carbon assimilation capacity and lower PSII and PSI activity levels. Cultivation of alfafa with +AMF promoted biomass accumulation and uptake of nutrients, increased its underground growth, and promoted accumulation of P over N and K. +AMF increased PSII and PSI activities in alfalfa leaves under salt stress, and increased the electron transfer ability of PSII donor and acceptor sides. +AMF not only made alfalfa have relatively high stomatal conductance under salt stress, but also significantly enhanced its ability to utilize CO2.

Influence of Arbuscular Mycorrhizal Fungi (AMF) Inoculation on Growth and Mycorrhizal Dependency of (&amp;lt;i&amp;gt;Lens culinaris&amp;lt;/i&amp;gt; L.) Varieties

Arbuscular mycorrhizal fungi (AMF) are soil fungi, obligate biotrophic fungi and form the most common mutualistic symbiosis in nature: the arbuscular mycorrhiza (AM). This association occurs on the roots of most plants, promoting improvements in plant growth and development. The present study was aimed to investigate the effect of arbuscular mycorrhizal fungi (Glomus aggergatums, Glomus fasciculatum, Glomus mosseae and Sclerocystis niger) inoculation on growth and mycorrhizal dependency of Lens culinaris L. varieties. The experiment was carried out under natural condition with two treatments (inoculated and control) in triplicates. Inoculation of lentil plants with arbuscular mycorrhizal fungi resulted a significant increase in various plant growth parameters compared to plants without inoculation. In addition, fungal inoculation significantly increased mycorrhizal dependency as compared to un-inoculated plants. It is concluded that fungal inoculation improve plant growth parameters under phosphorous deficient soil.

Regulation of mycorrhiza development in durum wheat by P fertilization: Effect on plant nitrogen metabolism

AbstractThe aim of this work was to study the effect of arbuscular mycorrhizal fungus Glomus mosseae on growth and nitrogen (N) metabolism of durum wheat (Tritcum durum) under various P soil contents. The analyses were extended to macro and micronutrient tissue concentrations, nitrate reductase and glutamine synthetase activities, as well as protein, aminoacids, pyridine dinucleotides and adenine nucleotides. Arbuscular mycorrhiza increased wheat growth in soil in which P availability was low and nitrate was the dominant N form. The root colonization occurred at the highest level in plants grown in limiting soil P and was inversely related to soil P content. The micorrhizal wheat plants contained also the highest concentrations of macro (P, K, Ca, N) and micronutrients (Fe, Zn, Mn) as well as free amino acids, protein, NAD, NADP, AMP, ADP, ATP in roots and leaves. In particular, the micronutrient tissue concentrations (Zn, Mn) supported that mycorrhiza actively modulated their uptake limiting interferences and optimizing growth better than the plant roots, like a very efficient “rootstock”. Control plants grown at the highest soil P did not reach the same concentration as the mycorrhizal plants. Nitrate reductase activities in the roots of mycorrhizal plants were higher than in the control ones, while glutamine synthetase activities were highest in the leaves. Protein and amino acids concentrations, as well as AMP, ADP, ATP, NAD(P), and NAD(P)H were also higher than in the control. Among the free amino acids in the roots, the high levels of glutamine, asparagine, arginine, support the view that ammonium was transferred through the arbuscules to the root cells where it was re‐assimilated in the cortical cells, forming high N : C ratio‐amino acids. They were transferred to the leaves where all the other N compounds could be largely synthesized using the carbon skeletons supplied by photosynthesis.

Agronomic bio-fortification and quality enhancement in okra–pea cropping system through arbuscular mycorrhizal fungi at varying phosphorus and irrigation regimes in Himalayan acid alfisol

ABSTRACTA field experimentation was conducted during 2009-2011 at CSK Himachal Pradesh Agricultural University, Palampur, India characterized with wet-temperate climate and acid Alfisol soil having medium available phosphorus content. The study aimed at bio-fortification and quality enhancement of okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through arbuscular mycorrhizal fungi (AMF) (Glomus mosseae) at varying inorganic phosphorus (50, 75, and 100% soil-test-based recommended P dose) and irrigation regimes (40 and 80% available water capacity) in a Himalayan acid Alfisol. The results revealed that AMF and inorganic P significantly enhanced the concentrations and uptake of various primary [nitrogen (N), phosphorus (P), and potassium (K)]; secondary [calcium (Ca)]; and micronutrients [iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), boron (B), and molybdenum (Mo)] in okra and pea crops. However, effects of varying irrigation regimes were found to be nominal. In okra, AMF inoculation considerably enhanced N, P, K, B, and Mo uptake by 5, 19, 3, 4, and 15%, respectively, over their non-AMF counterparts. Likewise in pea, a higher amount of N (10%), P (26%), K (7%), Fe (7%), Cu (38%), Zn (20%), Mn (4%), B (7%), and Mo (13%) uptake was registered through AMF inoculation over their non-AMF counterparts. Application of soil-test-based P dose from 50% to 100% P also resulted in significant and consistent improvement in N, P, K, B, and Mo uptake both in okra and pea and in Zn, Cu, Mn, and Fe uptake in pea crop. Magnitude of increase in Ca content was to the tune of 13 and 4%, respectively, in okra fruits and pea pods following AMF inoculation, whereas crude protein content enhanced by 4% each in both the crops. Overall, the current study demonstrates the important role of AMF in nutrient enrichment and quality enhancement of okra and pea crops in acid Alfisol, besides considerable reduction in investment on chemical fertilizers. Results of current study suggest that AMF use in Himalayan production systems is of tremendous significance to harvest nutritionally-rich farm produce for Himalayan communities suffering from malnutrition especially anemia and Zn deficiency, and equally to resource-poor Himalayan farmers who ill-afford expensive external inputs.

Effects of arbuscular mycorrhizal fungi on photosystem II activity of three pistachio rootstocks under salt stress as probed by the OJIP-test

We applied chlorophyll a fluorescence as a biomarker to assess the growth response and PSII behavior and performance of three pistachio (Pistacia vera) rootstocks to different salt levels after inoculation with arbuscular mycorrhizal fungi Glomus mosseae and compared it with non-mycorrhizal plants (control). Our results confirmed the depressing effect of salt stress on mycorrhization extent and showed that the effect of salinity on colonization rate is completely under the influence of host plant. In this experiment, mycorrhizal symbiosis could enhance plants total dry mass (TDM), electron transfer on the donor and the acceptor side of PSII, decrease the energy dissipation and increase the comprehensive photosynthesis performance under salt stress as well as under normal conditions. We found that both donor and acceptor sides of PSII are the target sides under high salinity in pistachio rootstocks. We also found that performance index is the parameter that better reflects the responses of the studied rootstocks to progressive salt stress. Bane-baqi was less affected by salinity in terms of TDM followed by Sarakhs and Abareqi.

Influence of AM fungi, inorganic phosphorus and irrigation regimes on plant water relations and soil physical properties in okra (Abelmoschus esculentus L.) – pea (Pisum sativum L.) cropping system in Himalayan acid alfisol

ABSTRACTPresent investigation studied plant water relations and soil physical properties through AM fungi (Glomus mosseae) to mitigate drought stress in Himalayan acid Alfisol having low water retentivity. Experimentation was carried out at Palampur, India during 2009–2011 in okra–pea cropping system in randomized block design (RBD) replicated thrice with 14 treatments comprising arbuscular mycorrhizal (AM) fungi, varying phosphorus nutrition and irrigation regimes at 40 and 80% available water holding capacity. Integrated use of AM fungi at varying phosphorus (P) levels and irrigation regimes led to significantly higher relative leaf water content (3% each) in okra and pea besides significantly higher xylem water potential (27%) in pea over non-AM fungi counterparts. AM fungi enhanced water-use-efficiency in okra (5–17%) and pea (12–35%) over non–AM fungi counterparts. AM fungi also improved water holding capacity (5–6%) and mean weight diameter of soil particles (4–9%) over non–AM fungi counterparts; but, had nominal or no effect on bulk density. Mycorrhizal plants maintained higher tissue water content imparting greater drought resistance to plants over non–mycorrhizal plants at moisture stress. It is inferred that integrated application of AM fungi and P at varying irrigation regimes improved the plant water relations vis-à-vis drought resistance, crop productivity, WUE, soil aggregation and water holding capacity in okra–pea sequence in Himalayan acid Alfisol.

Interrelated effects of mycorrhiza and free-living nitrogen fixers cascade up to aboveground herbivores.

Aboveground plant performance is strongly influenced by belowground microorganisms, some of which are pathogenic and have negative effects, while others, such as nitrogen-fixing bacteria and arbuscular mycorrhizal fungi, usually have positive effects. Recent research revealed that belowground interactions between plants and functionally distinct groups of microorganisms cascade up to aboveground plant associates such as herbivores and their natural enemies. However, while functionally distinct belowground microorganisms commonly co-occur in the rhizosphere, their combined effects, and relative contributions, respectively, on performance of aboveground plant-associated organisms are virtually unexplored. Here, we scrutinized and disentangled the effects of free-living nitrogen-fixing (diazotrophic) bacteria Azotobacter chroococcum (DB) and arbuscular mycorrhizal fungi Glomus mosseae (AMF) on host plant choice and reproduction of the herbivorous two-spotted spider mite Tetranychus urticae on common bean plants Phaseolus vulgaris. Additionally, we assessed plant growth, and AMF and DB occurrence and density as affected by each other. Both AMF alone and DB alone increased spider mite reproduction to similar levels, as compared to the control, and exerted additive effects under co-occurrence. These effects were similarly apparent in host plant choice, that is, the mites preferred leaves from plants with both AMF and DB to plants with AMF or DB to plants grown without AMF and DB. DB, which also act as AMF helper bacteria, enhanced root colonization by AMF, whereas AMF did not affect DB abundance. AMF but not DB increased growth of reproductive plant tissue and seed production, respectively. Both AMF and DB increased the biomass of vegetative aboveground plant tissue. Our study breaks new ground in multitrophic belowground–aboveground research by providing first insights into the fitness implications of plant-mediated interactions between interrelated belowground fungi–bacteria and aboveground herbivores.

Impact of Arbuscular Mycorrhizal Fungi with Trichoderma viride and Pseudomonas fluorescens on Growth, Yield and Oil Content in Helianthus annuus L.

:A pot experiment was performed to see the interactive potential of arbuscular mycorrhizal fungi (Glomus mosseae and Acaulospora laevis) alone or in combination with Trichoderma viride and Pseudomonas fluorescens on Helianthus annuus L. under glass house conditions. Various morphological and biochemical parameters were measured after 120 days. Overall results suggest that although, all co-inoculation treatments showed beneficial effects but inoculation with a combination of G. mosseae+A. laevis+T. viride + P. fluorescens showed maximum increment in all the growth parameters studied i.e. plant height, shoot biomass, root biomass, root length, leaf area, flower head diameter, chlorophyll content, root and shoot phosphorus, acidic and alkaline phosphatase, AM spore number, protein percent and oil content, whereas stomatal conductance was found maximum in G. mosseae+A. laevis+T. viride. The overall results demonstrate that the co-inoculation of bioinoculants like P. fluorescens and T. viride with AM fungi promotes higher AM colonization and spore number enhancing nutrient acquisition especially phosphorus (P), producing plant growth hormones resulting in improvement of rhizospheric condition of soil, altering the physiological and biochemical properties of sunflower plant.

Glomus mosseae bioprotection against aster yellows phytoplasma (16srI-B) and Spiroplasma citri infection in Madagascar periwinkle

The bio-control potential of arbuscular mycorrhizal fungus Glomus mosseae against two pathogenic microorganisms aster yellows (AY) phytoplasma and Spiroplasma citri has been examined in Madagascar periwinkle (Catharanthus roseus). G. mosseae had a positive influence on healthy C. roseus plants and S. citri infection. It provided bioprotection against S. citri pathogen and induced significant degree of resistance to spiroplasma infection. Besides, symptom expression significantly reduced and shoot height, leaves number, root fresh and dry weight increased in spiroplasma-infected plants treated with mycorrhiza fungus. Although, G. mosseae had no positive effect on phytoplasma disease. The root architectures were affected by the phytoplasma pathogen, and the root surface area dramatically decreased in G. mosseae treated AY-infected periwinkles compared with the control. Nitrogen and Phosphorus concentrations notably increased in spiroplasma + G. mosseae compared with control plants. Potassium concentration did not differ significantly in all mycorrhizal treated and untreated infected plants except in G. mosseae treated healthy plants. The spore density and root colonization rate did not vary in both pathogen treatments G. mosseae + spiroplasma and G. mosseae + phytoplasma. To our knowledge, this is the first report showing the bioprotective effect of G. mosseae on S. citri. The possible mechanisms involved in complex interaction between plants, cell wall-less bacteria and arbuscular mycorrhizal fungi (AMF) are discussed and the underlying mechanisms for the functioning of AMF are hypothesized.

Influence of Inorganic Phosphorus, VAM Fungi, and Irrigation Regimes on Crop Productivity and Phosphorus Transformations in Okra (Abelmoschus esculentus L.)–Pea (Pisum sativum L.) Cropping System in an Acid Alfisol

The present investigation was carried out at CSK Himachal Pradesh Agricultural University, Palampur, India, during 2009–2011 to economize inorganic phosphorus (P) and water needs of an okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through vesicular arbuscular mycorrhizal (VAM) fungi (Glomus mosseae) in a Himalayan acid Alfisol. The field experiment was replicated three times in a randomized block design comprising 14 treatments consisting of 12 treatment combinations of two VAM levels [0 and 12 kg ha−1], three phosphorus levels [50, 75, and 100% of recommended soil-test-based nitrogen (N)–P–potassium (K)], and two irrigation regimes [40 and 80% of available water-holding capacity of field soil (AWC)], in addition to one treatment with “generalized recommended NPK dose with generalized recommended irrigations (GRD)” and one treatment based on “farmers’ practice of plant nutrition and irrigation management in the region.” This article presents crop productivity and P dynamics studies during the second crop cycle of okra–pea sequence (2010–2011) and statuses of different P fractions in the soil after the second pea crop harvest during 2010–2011. Crop productivity and P uptake data in okra–pea sequence indicated that application of VAM + 75% P dose at either of two irrigation regimes did not differ significantly than GRD treatment and VAM + 100% P dose. It suggests an economy of about 25% inorganic P dose through VAM fungi. The treatments imbedded with VAM inoculation enhanced the P uptake in okra–pea system, on an average by 21% over the GRD and non-VAM-inoculated counterparts. Further, integrated application of P, VAM, and irrigation regimes evaluated in okra–pea sequence for 2 years led to greater status of water-soluble P (21%), sodium bicarbonate (NaHCO3)–inorganic phosphorus (Pi) (11%), sodium hydroxide (NaOH)–Pi (9%), hydrochloric acid (HCl)–extractable–P (20%) over non-VAM-inoculated counterparts and low status of organic P (NaHCO3-Po and NaOH-Po), all of which appreciably contributed to available P supply to plants in the present study in an acid Alfisol. The correlation coefficient reveals that contribution of inorganic P forms is highly correlated to crop productivity and total P uptake in okra and pea crops besides soil available P in the present study. Overall, it is concluded that VAM inoculation in okra–pea cropping system significantly enhanced the P availability to plants by way of enriching the labile-P pool such as water-soluble P and P loosely bound to aluminium (Al-P) and iron (Fe-P) on adsorption complexes and by P mineralization from organic matter in an Himalayan acid Alfisol.