Intraradices Inoculation Research Articles

Arbuscular mycorrhizal fungi improve the disease resistance of Lycium barbarum to root rot by activating phenylpropane metabolism.

Root rot is one of the common diseases of Lycium barbarum. Pathogens can cause devastating disasters to plants after infecting host plants. This study investigated the effect of arbuscular mycorrhizal fungi (AMF) Rhizophagus intraradices inoculation on phenylpropane metabolism in L. barbarum and evaluated its resistance to root rot. The experiment was set up with AMF inoculation treatments (inoculated or not) and root rot pathogen-Fusarium solani inoculation treatments (inoculated or not). The results showed that AMF was able to form a symbiosis with the root system of L. barbarum, thereby promoting plant growth significantly and increasing plants' resistance to disease stress. The plant height of AMF-colonized L. barbarum increased by 24.83% compared to non-inoculated diseased plants. After inoculation with AMF, the plant defense response induced by pathogen infection was stronger. When the enzyme activity of the leaves reached the maximum after the onset of mycorrhizal L. barbarum, phenylalanine ammonia-lyase, cinnamic acid-4-hydroxylase, and 4-coumaric acid-CoA ligase increased by 3.67%, 31.47%, and 13.61%, respectively, compared with the non-inoculated diseased plants. The products related to the lignin pathway and flavonoid pathway downstream of phenylpropane metabolism such as lignin and flavonoids were also significantly increased by 141.65% and 44.61% compared to nonmycorrhizal diseased plants. The activities of chitinase and β-1,3-glucanase increased by 36.00% and 57.96%, respectively. The contents of salicylic acid and jasmonic acid were also 17.7% and 31.63% higher than those of nonmycorrhizal plants in the early stage of plant growth, respectively. The results indicated that AMF significantly promoted plant growth and enhanced disease resistance by increasing enzyme activities and the production of lignin and flavonoids.

Negotiating soil water deficit in mycorrhizal trifoliate orange plants: A gibberellin pathway

Gibberellins (GAs), an important endogenous hormone, serve a crucial regulatory role in plants’ resistance to environmental stress, whereas it is unclear whether and how arbuscular mycorrhizal fungi (AMF) regulate the profile of GAs in plants exposed to soil water deficit (SWD). This study aimed to analyze how Rhizoglomus intraradices inoculation affected plant growth performance, antioxidant enzyme activities, and the composition, synthesis, metabolism, and signaling pathways of GAs in the roots of trifoliate orange (Poncirus trifoliata) under a 10-week SWD. Although the SWD decreased both root AMF colonization and soil hyphal length, mycorrhizal plants nevertheless outperformed non-mycorrhizal plants in terms of growth performance, as well as peroxidase (70.0%) and catalase (149.2%) activities, indicating greater drought tolerance. A total of nine GAs compositions were detected in the roots, with bioactive GA4 exclusively found in AMF roots. AMF colonization significantly reduced bioactive GA3 levels by 37.9%, while it increased inactive GA8, GA9, and GA15 levels under SWD by 522.2%, 100.0%, and 2500.0%. Inoculation with AMF also up-regulated the expression of PtCPS, PtPKS, and PtKO in GA synthesis pathways of roots and the expression of PtGA20ox, PtGA3ox, and PtGA2ox in GA metabolisms under SWD. In addition, the expression of DELLA genes PtGaipb and PtGai associated with GA signaling pathways was further up-regulated under SWD by AMF inoculation. It is concluded that AMF regulated the composition, synthesis, and deactivation of GAs in roots to promote plant growth, along with an increase in PtGaipb and PtGai expression to possibly initiate mycorrhizal signaling pathways in response to SWD.

Effects of Arbuscular Mycorrhizal Fungi on Growth and Nutrient Accumulation of Oat under Drought Conditions

Arbuscular mycorrhizal fungi (AMF) have established themselves as pivotal allies in the realm of plant physiology, renowned for their remarkable contributions to augmenting both growth and resilience against environmental stresses. In this study, we embarked on a comprehensive investigation into the discernible impact of two distinct AMF species on a widely planted oat cultivar, ‘Qingyan No. 1’, when subjected to the austere conditions of a drought. The experimental design included three distinct AMF treatments (inoculation with Rhiaophagus intraradices, Funneliformis mosseae, or not), and the three water treatments were 75% of field capacity (well watered), 50% of field capacity (moderate drought), and 30% of field capacity (severe drought). The obtained results showed that the rate of inoculation under 75% FC for both AMF species was over 74%. Drought stress limited the growth and osmotic regulation of the oat plants. However, AMF inoculation observably increased the above-ground biomass under 75% FC and increased the root biomass under 30% FC. AMF inoculation also increased the root traits under 75% FC and 50% FC. R. intraradices inoculation increased the above-ground soluble sugar and soluble protein concentrations, and both AMF species showed decreased malondialdehyde (MDA) concentrations in the roots. Furthermore, the pervasive influence of drought stress exerted a discernible stranglehold on nutrient uptake in the oat plants, profoundly impacting the distribution of nutrients within the shoots and roots. Regardless of the drought stress treatment, the inoculation with both AMF species increased the P concentrations in the roots and the K and Mg concentrations in the roots, and the inoculation with R. intraradices increased the Ca concentration in the whole oat plant. Under 75% FC, the N concentration of the whole oat plant was significantly reduced by both AMF species. However, under 50% FC and 30% FC, the N concentrations in the shoots inoculated with both AMF species were close to that of the non-inoculated shoots. In summary, AMF improved the osmotic regulation and nutrient absorption and distribution of oat plants under drought stress and thus promoted the growth and biomass accumulation of oat plants.

Rhizoglomus intraradices Is More Prominent in Improving Soil Aggregate Distribution and Stability Than in Improving Plant Physiological Activities

Arbuscular mycorrhizal fungi (AMF) confer positive and negative effects on many plants, but it is unclear whether AMF has an effect on soil fertility, aggregate distribution, and stability. The aim of this study was to analyze the effects of Rhizoglomus intraradices on plant growth, root morphology, leaf chlorophyll and gas exchange, sugar concentrations, and soil nutrients, aggregate distribution, and stability in marigold (Tagetes erecta L.), maize (Zea mays L.), white clover (Trifolium repens L.), and vetch (Vicia villosa Roth.) plants. Twelve weeks after R. intraradices inoculation, maize presented the highest mycorrhizal development, while mycorrhizal dependence was shown to be the decreasing trend in marigold > white clover > vetch > maize. AMF inoculation significantly increased the chlorophyll index of marigold and white clover, the net photosynthetic rate of white clover, the stomatal conductance of maize and white clover, and the transpiration rate of maize. Fructose, glucose, and sucrose in the four plants were differentially affected by R. intraradices. R. intraradices significantly increased the soil organic carbon (SOC) of marigold, maize, and white clover, the Olsen-P of white clover, the available K content of marigold, the easily extractable glomalin-related soil protein (GRSP) of maize, and the difficultly extractable and total GRSP levels of marigold and vetch. In addition, R. intraradices significantly increased the stability of soil water-stable aggregates (WSAs) in all four plants, plus it increased WSA at 0.5–4 mm sizes. Root AMF colonization was significantly positively correlated with WSA stability, SOC, difficultly extractable GRSP, and total GRSP. It is concluded that AMF-triggered changes in plant growth, physiological activities, and soil fertility depended on plant species, but AMF-improved WSA distribution and stability were not dependent on plant species.

Anatomical responses of leaf and stem of Catalpa bungei C.A.Mey. to nitrogen application and Rhizophagus intraradices inoculation

Plant morphology and anatomical structure are closely related to plant function, and their changes may affect physiological processes and may also be altered by nutrient availability or arbuscular mycorrhizal fungi (AMF) inoculation. To our knowledge, studies on the effect of AMF on plant anatomical characteristics under different nitrogen (N) levels are very scarce, especially in trees. Here, a pot experiment was carried out to evaluate the response of leaf and stem anatomy of Catalpa bungei using a two-factor completely randomized block design, including mycorrhizal inoculation (inoculation with Rhizophagus intraradices or not) and N application (low, medium, high). Regardless of the inoculation status, moderate N addition promoted leaf and stem development, while excessive N had a significant negative impact on the anatomical structure of seedlings. Compared with the non-inoculated treatments, AMF inoculation increased most of the leaf stomatal characteristic parameters and stem structural parameters of C. bungei seedlings, while significantly reduced leaf upper epidermis thickness (UET), lower epidermis thickness (LET), spongy tissue thickness (STT), and leaf thickness (LT) at low to medium N levels. In addition, the lenticel density (LD) at low N levels and the lenticel length (LL), width (LW), and area (SLA) at medium N levels in mycorrhizal seedlings were significantly higher than those in non-mycorrhizal seedlings. We concluded that AMF inoculation may significantly improve the water and gas exchange capacity of seedlings at least at low to medium N levels.

Beneficial effects of arbuscular mycorrhizae on Cu detoxification in Mimosa pudica L. grown in Cu-polluted soils.

Arbuscular mycorrhizal(AM) fungi are known to have beneficial effects on host plants growing on contaminated soils. The present study aimed at investigating the influence of two different AMfungi (Rhizophagus intraradices and Funneliformis mosseae) on the growth of plants and Cu uptake by Mimosa pudica L. grown in polluted soils containing various levels of Cu (Control, 400, 500, or 600mgkg-l soil) in pot experiments. Mycorrhizal colonisation rates by the two AMfungi decreased markedly with the increasing Cu levels in soils. This inhibition was more pronounced to F. mosseae than R. intraradices, indicating that R. intraradices was more tolerant to Cu than F. mosseae. Compared with non-mycorrhizal plants, R. intraradices inoculation increased plant growth (including shoot height, numbers of compound leaves and leaflets, and dry biomass) and P concentrations in the shoots and roots of M. pudica at all levels of Cu. Meanwhile, F. mosseae displayed a capability of growth promotion to M. pudica much later and lower than R. intraradices. F. mosseae and R. intraradices markedly decreased Cu concentration in shoots at 400-600mgkg-1 Cu levels. However, R. intraradices was more efficient than F. mosseae in decreasing the shootCu concentrations. As for the increasing Cu tolerance by R. intraradices, possibly it was reached though the improvement of phosphorus nutrition and the decline of Cu transportfrom roots to shoots of M. pudica. R. intraradices showed a good potential for improving medicinal plants growth and declining toxic effects in Cu-contaminated soils.

Rhizophagus intraradices improves arsenic tolerance in Sophora viciifolia Hance

PurposeArbuscular mycorrhizal fungi (AMF) are capable of protecting host plants against heavy metal toxicity, whereas rare knowledge has been acquired on the underlying effects of AMF on woody leguminous species under arsenic (As) stress. This study was aimed that whether AMF inoculation improves the As tolerance in Sophora viciifolia (a king of leguminous shrub).MethodsS. viciifolia seedlings were inoculated with AMF Rhizophagus intraradices, and then the seedlings were grown at three levels (0, 50, and 100 mg As kg−1 soil) of As-polluted soil by performing the potted experiments. The plant growth, photosynthetic parameter, oxidative damage, antioxidant enzyme activities and gene expression of phytochelatin synthase in R. intraradices- and non-inoculated S. davidii seedlings under the different levels of As stress were analyzed.ResultCompared with non-inoculated S. viciifolia at the identical As level, R. intraradices-inoculated S. viciifolia were higher in the shoot and root dry weight, plant height, root length, photosynthetic rate, stomatal conductance, transpiration rate, maximal photochemical efficiency of PSII photochemistry, actual quantum yield, and photochemical quenching values, while the intercellular CO2 concentration and non-photochemical quenching values were lower. As-induced oxidative stress generating malondialdehyde, hydrogen peroxide and superoxide in the S. viciifolia leaves and roots reduced significantly by R. intraradices inoculation, whereas the activities of antioxidative enzymes (e.g., superoxide dismutase, peroxidase, and catalase) in S. viciifolia leaves and roots were increased by R. intraradices inoculation. Notably, R. intraradices inoculation up-regulated the gene expression of S. viciifolia phytochelatins in the leaves and roots.ConclusionThese results demonstrated that R. intraradices inoculation enhanced the As tolerance in S. viciifolia seedlings by improving the plant growth, gas exchange, chlorophyll fluorescence, reactive oxygen species, antioxidant enzymes and gene expression of S. viciifolia phytochelatins. The present study verified a multifarious positive role of AMF for woody leguminous species under As stress.

Effects of arbuscular mycorrhizal inoculation on the growth, photosynthesis and antioxidant enzymatic activity of Euonymus maackii Rupr. under gradient water deficit levels.

The role of arbuscular mycorrhizal (AM) fungus (Rhizophagus intraradices) in the amelioration of the water deficit-mediated negative influence on the growth, photosynthesis, and antioxidant system in Euonymus maackii Rupr. was examined. E. maackii seedlings were subjected to 5 water deficit levels, soil water contents of 20%, 40%, 60%, 80% and 100% field capacity (FC), and 2 inoculation treatments, with and without AM inoculation. The water deficit increasingly limited the seedling height, biomass accumulation in shoots and roots, chlorophyll content, gas exchange and chlorophyll fluorescence parameters with an increasing water deficit level. In addition, water deficit stimulated the activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), in both shoots and roots, except under 20% FC conditions. E. maackii seedlings under all water deficit conditions formed symbiosis well with AM fungi, which significantly ameliorated the drought-mediated negative effect, especially under 40% and 60% FC conditions. Under 40% to 80% FC conditions, AM formation improved seedling growth and photosynthesis by significantly enhancing the biomass accumulation, chlorophyll content and assimilation. Mycorrhizal seedlings showed better tolerance and less sensitivity to a water deficit, reflected in the lower SOD activities of shoots and roots and CAT activity of shoots under 40% and 60% FC conditions. Downregulation of the antioxidant system in mycorrhizal seedlings suggested better maintenance of redox homeostasis and protection of metabolism, including biomass accumulation and assimilation. All the results advocated the positive role of R. intraradices inoculation in E. maackii against a water deficit, especially under 40% FC, which suggested the distinct AM performance in drought tolerance and the potential role of the combination of E. maackii-AM fungi in ecological restoration in arid regions.

A Growth and Phosphorus Uptake of Soybean (Glycine Max L.) in Response to Arbuscular Mycorrhizal Fungus Rhizophagus Intraradices Inoculation in Heavy Metal-contaminated Soils

ABSTRACT The present study investigated the effect of arbuscular mycorrhizal fungus (AMF) Rhizophagus intraradices on plant growth and phosphorus (P) uptake of soybean (Glycine max L.) in soils contaminated with different concentrations of heavy metals [copper (100 and 300 mg kg−1), lead (100 and 300 mg kg−1) and zinc (300 and 600 mg kg−1)] and combination (Cu100 + Pb100 + Zn300) in a pot experiment. The bioaccumulation characteristics of the heavy metals in the plant tissues in terms of bioabsorption coefficient (BAC), bioconcentration factor (BCF) and translocation factor (TF) were also evaluated. The results showed R. intraradices inoculation significantly (p < .01) enhanced soybean growth, P uptake and grain yield in all polluted soils compared to non-inoculated treatment. In addition, R. intraradices retained most of the heavy metals in the roots, with lesser translocation to the shoots and seeds. Exposure to 600 mg Zn kg−1 soil remarkably reduced the plant growth, P content and seed yield of the soybean. Copper uptake in the shoot was significantly increased in multi-metal contaminated soil with reduced lead and zinc compared to single polluted soils. This work suggests that Rhizophagus intraradices inoculation may be a potential and effective of AMF isolate for enhancing plant growth, P nutrition and stress tolerance in heavy metal-contaminated soil

Nodulation and biological nitrogen fixation in soybean (Glycine max L.) as influenced by phosphorus fertilization and arbuscular mycorrhizal inoculation

Abstract Arbuscular mycorrhizal fungi (AMF) can be used to promote the productivity of legumes on phosphorus- (P) deficient soils. The present study investigates the inoculation effects of three AMF species (Funneliformis mosseae, Rhizophagus intraradices, and Claroideoglomus etunicatum) and the control (uninoculated) on nitrogen fixation efficiency and growth performance of tropical soybean cultivar (TGx1448-2E) under varying P fertilizer rates (0, 20, and 40 kg P2O5 ha−1) in a derived savannah of Nigeria. The results showed that shoot and root dry matter, number of nodules, relative ureide abundance (RUA), nitrogen derived from atmosphere (Ndfa), total N fixed, shoot P uptake, grain, and biomass yield significantly increased with AMF inoculation, with better performance observed in plants inoculated with Rhizophagus intraradices and Funneliformis mosseae compared to Claroideoglomus etunicatum. Similarly, the soybean growth variables, P uptake, and nitrogen fixation activities increased with increasing P application rates. Conversely, AMF root colonization significantly reduced with increasing P rate. Interaction of AMF inoculation and P rates significantly influenced soybean growth and nitrogen fixation. R. intraradices inoculation with 20 kg P2O5 ha−1 resulted in the highest amount of RUA, Ndfa, N fixed, and grain yield. It could be concluded from this study that R. intraradices with moderate P rate could be used to enhance nodulation, nitrogen fixation, and soybean yield in P-deficient soils.

Rhizoglomus intraradices Improves Plant Growth, Root Morphology and Phytohormone Balance of Robinia pseudoacacia in Arsenic-Contaminated Soils

Arbuscular mycorrhizal fungi (AMF) are known to improve the resistance of host plants against various heavy metal stresses. However, the arsenic (As) resistance mechanism of AMF-inoculated woody legumes remains unclear. In this study, black locust (Robinia pseudoacacia L.) seedlings were cultivated in potted soils inoculated with or without AMF Rhizoglomus intraradices under three different levels of As stress (0, 100, and 200 mg As kg–1 soil) over 4 months. The objective of this paper was to investigate the effects of AMF on plant growth, root morphology, and the content and ratio of endogenous phytohormones and soil glomalin under As stress condition. As stress toxicity suppressed the AM spore germination and colonization, plant growth, and the content of soil glomalin and changed the morphological characteristics of the roots and the balance of endogenous hormone levels in plants. However, R. intraradices inoculation improved the shoot and root dry weights, total root length, root surface area, root volume, and the number of root forks and tips across all As treatments. R. intraradices inoculation obviously decreased the percentage of root length in the 0- to 0.2-mm diameter class and increased those in the 0.5- to 1.0-mm and >1.0-mm diameter classes; the percentages in the 0.2- to 0.5-mm diameter class were less affected by R. intraradices inoculation. The concentrations of the easily extractable glomalin-related (EE-GRSP) and total glomalin-related soil protein (T-GRSP) were higher in the of R. intraradices-inoculated seedlings than those in the non-inoculated seedlings. Furthermore, R. intraradices inoculation increased the concentrations of indole-3-acetic acid (IAA) and abscisic acid (ABA), but decreased the concentrations of gibberellic acid (GA) and zeatin riboside (ZR). The phytohormone ratios of IAA/ABA, GA/ABA, ZR/ABA, and (IAA + GA + ZR)/IAA in the R. intraradices-inoculated seedlings were lower than those in the non-inoculated seedlings. These results indicated that R. intraradices alleviated As toxicity in R. pseudoacacia seedlings by improving their plant growth, altering root morphology, regulating the concentrations and ratios of phytohormones, and increasing the concentration of soil glomalin. The results suggested that AMF-inoculated R. pseudoacacia seedlings would be a critical factor in successful vegetation restoration and soil development in As-contaminated soils.

Arbuscular mycorrhiza augments essential oil composition and antioxidant properties of Ocimum tenuiflorum L. – A popular green tea additive

The increasing interest and demand of Ocimum tenuiflorum L. and its products in different industrial sectors necessitate appropriate cultural practices for cultivation of the plant with increased herbage and essential oil yield. Studies on O. tenuiflorum in relation to arbuscular mycorrhiza are restricted to evaluation of diversity of the mycorrhizal fungi in its rhizosphere or assessment of the ability of different species to colonize its roots. Hence, the present study aimed to assess the effect of arbuscular mycorrhizal fungus (Rhizophagus intraradices) inoculation on the pharmaceutically desired parameters of two high yielding genotypes of O. tenuiflorum. Colonization by R. intraradices fungus resulted in significant increase in the leaf biomass and concentration of essential oil in both the genotypes. Formation of arbuscular mycorrhiza resulted in up to 59.01 % and 86.95 % increase in essential oil concentration in mycorrhizal genotype A and B plants, respectively, in comparison with control. The characterization of essential oils by Gas Chromatography-Mass Spectrometry showed significant effect of arbuscular mycorrhiza on their chemical profile. A total of 23 and 37 compounds were identified in essential oils of control genotype A and B, respectively, while 21 and 34 compounds were detected in essential oils of their respective mycorrhizal counterparts. Concentration of eugenol (a valued phenylpropanoid), and other medicinally important terpenoids (β-elemene, β-caryophyllene, germacrene A, and germacrene D) increased in essential oils of mycorrhizal plants.While genotype and mycorrhizal interaction significantly influenced biomass and essential oil concentration in leaves, the effect of R. intraradices on concentration of eugenol, β-elemene, and β-caryophyllene did not vary between the two genotypes. Additionally, principal component analysis also highlighted that the volatiles common in the essential oil of the four treatments contributed significantly to the variation in the essential oil composition. Phenol, flavonoid, and polyphenol contents in the leaves were also enhanced on formation of arbuscular mycorrhiza. The study also aimed to evaluate the ability of leaves (fresh and processed) to scavenge reactive oxygen and nitrogen species. Arbuscular mycorrhiza augmented the antioxidant capacity of fresh and processed leaves of both the genotypes. Thus, findings of the study demonstrate that R. intraradices inoculation enhances productivity of O. tenuiflorum and also improves the quality of the products.

Physiological Beneficial Effect of Rhizophagus intraradices Inoculation on Tomato Plant Yield under Water Deficit Conditions

Increasing drought, under current climate change scenarios, will reduce the sustainability of tomato cultivation in the Mediterranean region. The present study evaluates the effect of Rhizophagus intraradices inoculation on tomato plant physiology and yield in response to progressive water deficit conditions. Two commercial products (Prod1 and Prod2) containing only R. intraradices were tested at two different concentrations (1% and 5% of the substrate volume) using three methods of inoculation: (a) mixed to substrate, (b) dissolved in water, (c) spread on seedlings root blocks before transplant. The highest mycorrhization of root fragments (F%) was found with Prod2 at 1% w/w at 40 days after sowing (DAS); this product was therefore used in a second experiment to inoculate tomato plants and test their physiological response to progressive water deficit induced withholding irrigation. Phenology, plant height, stem diameter, chlorophyll content and fluorescence, whole canopy gas exchange, biomass production and partitioning and phosphorus content were investigated in inoculated and not inoculated tomato plants under well-watered and water stressed conditions. Vegetative period and plant height were shorter in inoculated than in control plants; moreover, inoculation with R. intraradices increased fruit production by enhancing chlorophyll content under water stress condition, PS2 efficiency, ETR, Fv/Fm, net photosynthetic rate and whole canopy WUE.

Establishment and traffic stress response of tall fescue as affected by Mycorrhiza fungi and Trinexapac-ethyl

Heavy traffic regularly causes damage of substantial aboveground parts to turf grasses. Several factors could affect the traffic stress severity, including the number of occasions per season and the soil moisture content during the traffic stress. Mycorrhiza results in numerous advantages to host plant like improving the turfgrass establishment, root structure and also abiotic stress tolerance of plants. Festuca arundinacea remains green during the playing season and it is the most popular turf grass for football. Trinexapacethyl (TE) might be influence the wear as growth retardant. Accordingly, mycorrhiza infection effect on tall fescue establishment, and TE effect on traffic stress after establishment were studied. The treatments, including traffic stress (traffic and non-traffic stress), TE (0 and 200 g 100 m-2) and mycorrhiza (Control; Glomus mosseae and Glomus intraradices) 50 g m-2 were evaluated on two cultivars of tall fescue in two growing season of 2017 and 2018. Both mycorrhizas were significantly colonized on turfgrass root during establishment. G. intraradices inoculation increased the establishment by passing 60 days from seeding in F. arundinacea cv. Barvado. After establishment, traffic stress reduced the relative water content (RWC) in 2017 and 2018, and also reduced the turf quality and soluble sugar content (SSC). TE improved the RWC, SSC, turf quality and also colonization percentage. Mycorrhiza inoculation enhanced tall fescue establishment. TE application at 200 g 100 m-2 had no influence on traffic stress, however, it improved turf quality, RWC, SSC and mycorrhiza colonization.

Arbuscular mycorrhizal fungi (Glomus intraradices) and diazotrophic bacterium (Rhizobium BMBS) primed defense in blackgram against herbivorous insect (Spodoptera litura) infestation

In the changing scenario of agriculture, plants are exposed to various biotic and abiotic stresses. Induction of both constitutive and inducible defense systems was noticed in plants exposed to stress. As a major defense response, production of phenolics and superoxide radicals quenching enzymes is accelerated in plants under stress. These metabolites production intensified further when arbuscular mycorrhizal fungi (AMF) infected plants are subjected to stress. With this background, we conducted experiments to explore the impacts of Glomus intraradices and Rhizobium on the stimulation of defense in blackgram against Spodoptera litura. Uninoculated plants accumulated considerable quantity of defense metabolites like phenolics, lignin and superoxide radicals quenching enzymes such as superoxide dismutase, peroxidase, catalase, phenylalanine ammonium lyase, and polyphenol oxidase constitutively. While production of these defense metabolites primed strongly due to G. intraradices inoculation. These defense responses augmented further when G. intraradices colonized plants were exposed to S. litura. Though the combined inoculation with G. intraradices and Rhizobium improved the defense response, the effect was more pronounced due to single inoculation with G. intraradices. Results of in vitro leaf feeding bioassay showed that the feeding capacity of S. litura reduced (36.32%) significantly due to feeding G. intraradices infected plants. These outcomes revealed that tolerance against S. litura in blackgram could be primed by mycorrhizal inoculation. This is the first report to state that G. intraradices besides improving nutrient use efficiency, also accelerates defense response in blackgram against S. litura. Hence, AMF could be recommended as a bioprotectant against S. litura in blackgram.

Phosphoproteomic changes in root cells of Poncirus trifoliata (L.) Raf. induced by Rhizophagus intraradices inoculation

Arbuscular mycorrhiza (AM) is a widespread endosymbiosis between terrestrial plants and AM fungi belonging to sub-phylum Glomeromycotina (Mycologia 108: 1028–1046, 2016). To date, many plant genes involved in establishing the AM symbiosis have been identified. Yet, the precise mechanisms governing the early signaling process are still not well understood. In this study, we employed the isotope tags for relative and absolute quantification (iTRAQ) and LC–MS/MS analysis to investigate the phosphoproteomic changes in the root cells of Poncirus trifoliata (L.) Raf. (a common citrus rootstock) during the establishment of the AM symbiosis. A total of 1920 unique phosphopeptides derived from 1016 phosphoproteins were identified, which collectively contained 2308 phosphorylation sites. Motif-X analysis of all the detected phosphopeptides showed that 25 phosphoserine motifs and 4 phosphothreonine motifs were overrepresented in phosphorylation processes. Among the phosphoserine motifs, [SDXE] and [PXSP] showed the highest fold increase upon colonization by Rhizophagus intraradices, suggesting that they may play potential roles in AM symbiosis. At 1 week post-inoculation of R. intraradices, the phosphorylation levels of 65 phosphopeptides were significantly changed (p value 1.35), with 39 upregulated and 26 downregulated, implying that at least some of the 65 phosphoproteins may be involved in the signal transduction during early events of the AM symbiosis. This study provides a comprehensive phosphoproteomic analysis in a citrus rootstock and the phosphoproteomic changes should shed light onto the signaling mechanisms involved in the establishment of AM symbiosis.

Identification of Arbuscular Mycorrhiza Fungi Responsive microRNAs and Their Regulatory Network in Maize.

Maize can form symbiotic relationships with arbuscular mycorrhiza (AM) fungus to increase productivity and resistance, but the miRNAs in maize responsible for this process have not been discovered. In this study, 155 known and 28 novel miRNAs were identified by performing high-throughput sequencing of sRNA in maize roots colonized by AM fungi. Similar to the profiles in other AM-capable plants, a large proportion of identified maize miRNAs were 24 nt in length. Fourteen and two miRNAs were significantly down- and up-regulated in response to AM fungus Glomus intraradices inoculation, respectively, suggesting potential roles of these miRNAs in AM symbiosis. Interestingly, 12 of 14 significantly down-regulated known maize miRNAs belong to the miR399 family, which was previously reported to be involved in the interaction between Medicago truncatula and AM fungi. This result indicated that the miR399 family should regulate AM symbiosis conservatively across different plant lineages. Pathway and network analyses showed that the differentially expressed miRNAs might regulate lipid metabolism and phosphate starvation response in maize during the symbiosis process via their target genes. Several members of the miR399 family and the miR397 family should be involved in controlling the fatty acid metabolism and promoting lipid delivering from plants to AM fungi. To the best of our knowledge, this is the first report on miRNAs mediating fatty acids from plant to AM fungi. This study provides insight into the regulatory roles of miRNAs in the symbiosis between plants and AM fungi.

Effects of arbuscular mycorrhizal fungus Rhizoglomus intraradices on active and passive pools of carbon in long-term soil fertility gradients of maize based cropping system

ABSTRACTA potculture study was conducted in soils collected from long-term fertilizer experiment (LTFE) being kept up as far the past 40 years to determine whether arbuscular mycorrhizal fungus (AMF) Rhizoglomus intraradices colonization changes the active and passive pools of carbon in a maize (Zea mays) – finger millet (Eleusine crocana)- cowpea (Vigna sinensis) cropping sequence in the Experimental Farm of the Tamil Nadu Agricultural University, Coimbatore, India. Soil samples were processed, sterilized and maize plants were grown in various fertility gradients in the absence (M-) or presence (M+) of AMF (Rhizoglomus intraradices) inoculation. The data have clearly shown that M+ soils had consistently higher active pools such as water soluble carbon, hot water soluble carbon and biomass carbon (M- 189; M + 305 mg kg−1), and passive pools such as soil organic carbon (M- 4.17; M + 4.31 mg g−1) and total glomalin. Among the fertility gradients, 100% NPK + Farm Yard Manure (FYM) with or without mycorrhizal fungal inoculation registered higher values for both active and passive pools of C but the response was more pronounced in the presence AMF inoculation. Overall, the data suggest that mycorrhizal fungal inoculation assists in effective carbon sequestration in an intensive cereal-legume cropping system.Abbreviations: AMF: Arbuscular mycorrhizal fungi; DAS: Days After Sowing; LTFE: Long-Term Fertilizer Experiment; WSC: Water soluble organic carbon; HA: Humic acid; FA: Fulvic acid; HWSC: Hot water soluble carbon

Mycorrhizal symbiosis and phosphorus fertilization effects on Zea mays growth and heavy metals uptake

ABSTRACTArbuscular mycorrhizal fungi (AMF) can promote plant growth and reduce plant uptake of heavy metals. Phosphorus (P) fertilization can affect this relationship. We investigated maize (Zea mays L.) uptake of heavy metals after soil AMF inoculation and P fertilization. Maize biomass, glomaline and chlorophyll contents and uptake of Fe, Mn, Zn, Cu, Cd and Pb have been determined in a soil inoculated with AMF (Glomus aggregatum, or Glomus intraradices) and treated with 30 or 60 µg P-K2HPO4 g−1 soil. Consistent variations were found between the two mycorrhizal species with respect to the colonization and glomalin content. Shoot dry weight and chlorophyll content were higher with G. intraradices than with G. aggregatum inoculation. The biomass was highest with 30 µg P g−1 soil. Shoot concentrations of Cd, Pb and Zn decreased with G. aggregatum inoculation, but that of Cd and Pb increased with G. intraradices inoculation. Addition of P fertilizers decreased Cd and Zn concentrations in the shoot. AMF with P fertilization greatly reduced maize content of heavy metals. The results provide that native AMF with a moderate application rate of P fertilizers can be exploited in polluted soils to minimize the heavy metals uptake and to increase maize growth.

The effect of Glomus intraradices on the physiological properties of Panax ginseng and on rhizospheric microbial diversity

BackgroundGlomus intraradices is a species of arbuscular mycorrhizal fungi that, as an obligate endomycorrhiza, can form mutually beneficial associations with plants. Panax ginseng is a popular traditional Chinese medicine; however, problems associated with ginseng planting, such as pesticide residues, reduce the ginseng quality. MethodsIn this experiment, we studied the effect of inoculating G. intraradices on several physiological properties and microbial communities of ginseng. UV-Visible Spectrum method was used to detect physical properties. Denaturing gradient gel electrophoresis method was used to analyze microbial communities. ResultsThe results indicated that inoculation with G. intraradices can improve the colonization rate of lateral ginseng roots, increase the levels of monomeric and total ginsenosides, and improve root activity as well as polyphenol oxidase and catalase activities. We also studied the bacterial and fungal communities in ginseng rhizospheric soil. In our study, G. intraradices inoculation improved the abundance and Shannon diversity of bacteria, whereas fungi showed a reciprocal effect. Furthermore, we found that G. intraradices inoculation might increase some beneficial bacterial species and decreased pathogenic fungi in rhizospheric soil of ginseng. ConclusionOur results showed that G. intraradices can benefit ginseng planting which may have some instructive and practical significance for planting ginseng in farmland.