Effect of the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum on the essential oil yield related characters and nutrient acquisition in the crops of different cultivars of menthol mint (Mentha arvensis) under field conditions

Variability in Chemical Composition and Biochemical Activities of Mentha x piperita L. Essential Oil, in Response to Mycorrhizal Symbiosis and Heavy Metal Stress

The present paper highlights the effect of Pb/Cd-stress and/or mycorrhizal colonization by Glomus Intraradices on yield, chemical composition, cytotoxicity and antimicrobial activity of Mentha x piperita L. essential oil. Our findings showed that mycorrhizal colonization could be used to improve the essential oil yield of M. x piperita, either in non-stressed or Pb/Cd-stressed plants. GC-MS analysis revealed three chemotypes: linalool/pulegone (32.6/30.8 %) chemotype in essential oils of non-mycorrhizal Pb-stressed plants, menthone/menthyl acetate (30.3/25.1 %) chemotype in essential oils of non-mycorrhizal Cd-stressed plants and menthol (44.6 %) chemotype in essential oils of non-mycorrhizal non-stressed plants, mycorrhizal non-stressed plants and mycorrhizal Pb/Cd-stressed plants. The cytotoxicity of M. x piperita essential oil, evaluated by brine shrimp lethality bioassay, was increased in presence of Pb/Cd-stress (from 379.58 to 72.84 μm/mL) and decreased in mycorrhizal plants (from 379.58 to 482.32 μm/mL). The antimicrobial activity of M. x piperita essential oil, evaluated by disc diffusion method and determination of Minimum Inhibitory Concentration against ten microorganisms, was enhanced by the mycorrhizal colonization and deceased by the Pb/Cd-stress. In conclusion, the inoculation of medicinal plants with mycorrhizal fungi is a real avenue for alleviating abiotic stress and/or increasing the quantity and quality of secondary metabolites in terms of biological activities.

Seaweed extract and arbuscular mycorrhiza co-application affect the growth responses and essential oil composition of Foeniculum vulgare L

The influence of arbuscular mycorrhiza fungi (AMF) inoculation, seaweed extract (SWE) foliar use, and their co-applications were evaluated on the growth-associated traits, antioxidant potential, essential oil profile, and the nutrients content of fennel plants. A factorial experiment was conducted as a completely randomized design with two factors and four replications in the greenhouse. The factors were: AMF inoculation (not inoculated and inoculated with 5 g kg^-1) and SWE foliar application (0, 0.5, 1.5, or 3 g L^-1). The highest root colonization percentage was recorded in plants treated with AMF + 3 g L^-1 of SWE. The top recorded plant height, leaf number, leaf dry weight, biomass, thousand seed weight (TSW), total soluble proteins and total soluble carbohydrates content, antioxidant activity, and essential oil content belonged to AMF + 3 g L^-1 of SWE. Furthermore, the co-application of AMF + SWE resulted in a considerable enhancement of the photosynthetic pigments content and, in N, P, K, Fe, Zn, and Mn contents in the shoots and roots. The GC-FID and GC-MS analysis revealed that (E)-anethole (73.28-76.18%), fenchone (5.94-8.26%), limonene (4.64-6.58%), methyl chavicol (2.91-3.18%), and (Z)-β-ocimene (1.36-2.01%) were the principal essential oil constituents. The top (E)-anethole and fenchone contents were obtained by AMF + SWE. Altogether, the simultaneous application of AMF and SWE could be introduced as an environment-friendly strategy to reach reliable growth responses, especially in fennel plants' enriched with some precious essential oil constituents.

Biochemical basis for the formation of organ-specific volatile blends in mint

Above-ground material of members of the mint family is commercially distilled to extract essential oils, which are then formulated into a myriad of consumer products. Most of the research aimed at characterizing the processes involved in the formation of terpenoid oil constituents has focused on leaves. We now demonstrate, by investigating three mint species, peppermint (Mentha ˣ piperita L.), spearmint (Mentha spicata L.) and horsemint (Mentha longifolia (L.) Huds.; accessions CMEN 585 and CMEN 584), that other organs - namely stems, rhizomes and roots - also emit volatiles and that the terpenoid volatile composition of these organs can vary substantially from that of leaves, supporting the notion that substantial, currently underappreciated, chemical diversity exists. Differences in volatile quantities released by plants whose roots had been dipped in a Verticillium dahliae-spore suspension (experimental) or dipped in water (controls) were evident: increases of some volatiles in the root headspace of mint species that are susceptible to Verticillium wilt disease (peppermint and M. longifolia CMEN 584) were detected, while the quantities of certain volatiles decreased in rhizomes of species that show resistance to the disease (spearmint and M. longifolia CMEN 585). To address the genetic and biochemical basis underlying chemical diversity, we took advantage of the newly sequenced M. longifolia CMEN 585 genome to identify candidate genes putatively coding for monoterpene synthases (MTSs), the enzymes that catalyze the first committed step in the biosynthesis of monoterpenoid volatiles. The functions of these genes were established by heterologous expression in Escherichia coli, purification of the corresponding recombinant proteins, and enzyme assays, thereby establishing the existence of MTSs with activities to convert a common substrate, geranyl diphosphate, to (+)-α-terpineol, 1,8-cineole, γ-terpinene, and (-)-bornyl diphosphate, but were not active with other potential substrates. In conjunction with previously described MTSs that catalyze the formation of (-)-β-pinene and (-)-limonene, the product profiles of the MTSs identified here can explain the generation of all major monoterpene skeletons represented in the volatiles released by different mint organs.

Arbuscular mycorrhizal fungi: Effects on secondary metabolite accumulation of traditional Chinese medicines

Traditional Chinese medicine (TCM) has played a pivotal role in maintaining the health of people, and the intrinsic quality of TCM is directly related to the clinical efficacy. The medicinal ingredients of TCM are derived from the secondary metabolites of plant metabolism and are also the result of the coordination of various physiological activities in plants. Arbuscular mycorrhizal fungi (AMF) are among the most ubiquitous plant mutualists that enhance the growth and yield of plants by facilitating the uptake of nutrients and water. Symbiosis of AMF with higher plants promotes growth and helps in the accumulation of secondary metabolites. However, there is still no systematic analysis and summation of their roles in the application of TCM, biosynthesis and accumulation of active substances of herbs, as well as the mechanisms. AMF directly or indirectly affect the accumulation of secondary metabolites of TCM, which is the focus of this review. First, in this review, the effects of AMF symbiosis on the content of different secondary metabolites in TCM, such as phenolic acids, flavonoids, alkaloids and terpenoids, are summarized. Moreover, the mechanism of AMF regulating the synthesis of secondary metabolites was also considered, in combination with the establishment of mycorrhizal symbionts, response mechanisms of plant hormones, nutritional elements and expression of key enzyme their activities. Finally, combined with the current application prospects for AMF in TCM, future in-depth research is planned, thus providing a reference for improving the quality of TCM. In this manuscript, we review the research status of AMF in promoting the accumulation of secondary metabolites in TCM to provide new ideas and methods for improving the quality of TCM.

Arbuscular mycorrhizal fungi and production of secondary metabolites in medicinal plants

Medicinal plants are an important source of therapeutic compounds used in the treatment of many diseases since ancient times. Interestingly, they form associations with numerous microorganisms developing as endophytes or symbionts in different parts of the plants. Within the soil, arbuscular mycorrhizal fungi (AMF) are the most prevalent symbiotic microorganisms forming associations with more than 70% of vascular plants. In the last decade, a number of studies have reported the positive effects of AMF on improving the production and accumulation of important active compounds in medicinal plants.In this work, we reviewed the literature on the effects of AMF on the production of secondary metabolites in medicinal plants. The major findings are as follows: AMF impact the production of secondary metabolites either directly by increasing plant biomass or indirectly by stimulating secondary metabolite biosynthetic pathways. The magnitude of the impact differs depending on the plant genotype, the AMF strain, and the environmental context (e.g., light, time of harvesting). Different methods of cultivation are used for the production of secondary metabolites by medicinal plants (e.g., greenhouse, aeroponics, hydroponics, in vitro and hairy root cultures) which also are compatible with AMF. In conclusion, the inoculation of medicinal plants with AMF is a real avenue for increasing the quantity and quality of secondary metabolites of pharmacological, medical, and cosmetic interest.

Biofertilizer Application Enhances Drought Stress Tolerance and Alters the Antioxidant Enzymes in Medicinal Pumpkin (Cucurbita pepo convar. pepo var. Styriaca)

The effects of mycorrhiza, Thiobacillus and Nitroxin (Azotobacter and Azospirillum sp.) biofertilizers under drought stress conditions with four levels of field capacity (FC) (control(100%), 85%, 70%, and 50%) on the antioxidant enzyme activities of medicinal pumpkin (Cucurbita pepo convar. pepo var. Styriaca) were evaluated during the years 2018–2019. Irrigation levels exhibited significant effects on all studied variables, except for the catalase (CAT) enzyme. A significant correlation was observed between the effects of irrigation levels and biofertilizers on antioxidant enzymes, soluble protein content, and grain yield. The highest activity of catalase and ascorbate peroxidase (APX) enzymes was achieved using mycorrhiza in 50% FC. Increasing drought intensity and mycorrhiza stimulated glutathione reductase (GR) and guaiacol peroxidase (GPX) activities by 32% and 66%, while Nitroxin increased them by 16% and 43%, respectively. Under severe drought stress conditions, only mycorrhiza exhibited a positive effect on GR and GPX enzymes. Under moderate and severe drought stress conditions, Nitroxin increased grain yield by 13% and 12.6%, respectively. The irrigation regimes and bio-fertilizers had a significant effect on β-sitosterol percentage. The highest amount was observed at the highest level of drought stress. Among the various bio-fertilizers treatments, the application of Thiobacillus yielded the highest percentage of β-sitosterol. The results of the present study demonstrate that the application of biofertilizers is beneficial in coping with drought stress.

Effects of Irrigation with Different Sources of Water on Growth, Yield and Essential Oil Compounds in Oregano

Aromatic plants can benefit from the use of treated wastewater to satisfy their water requirements, but the effects on the essential oil yield and quality need an assessment. The aims of this study were to assess the effects of freshwater and treated wastewater obtained from a Sicilian (Italy) pilot-scale horizontal subsurface flow constructed wetland system on plant growth and yield, essential oil yield and composition of oregano (Origanum vulgare ssp. hirtum (Link) Ietswaart) and soil characteristics. The system had a total surface area of 100 m2 and was planted with giant reed and umbrella sedge. An experimental open field of oregano was set up close to the system. Two years and two different sources of irrigation water were tested in a split-plot design for a two-factor experiment. Treated wastewater was characterized by higher values of mineral and organic constituents than freshwater. The results highlight that short-term irrigation with freshwater and treated wastewater, in both years, led to increased plant growth, dry weight and essential oil yield of oregano plants. However, it did not significantly affect the essential oil content and composition in comparison with the control. Furthermore, the year and source of irrigation water did not significantly vary the chemical composition of the soil. Our results suggest that treated wastewater can be considered an alternative to freshwater for the cultivation of oregano due to the fact that it does not greatly influence the yield quality and quantity of this species in the short-term.

Yield, Essential Oil and Quality Performances of Artemisia dracunculus, Hyssopus officinalis and Lavandula angustifolia as Affected by Arbuscular Mycorrhizal Fungi under Organic Management

Utilization of arbuscular mycorrhizal fungi (AMF) for enhancing growth and development as well as production of essential oil in aromatic plants has been increasingly drawing research interest. In order to assess the AMF effects on different aromatic species, an open-field experiment was carried out using Artemisia dracunculus (tarragon), Lavandula angustifolia (lavender) and Hyssopus officinalis (hyssop). AMF stimulated the growth of tarragon and lavender plants, whereas hyssop showed a slight developmental slowing; nonetheless, a significant increase in essential oil content in the three species was seen. AMF application increased the biomass of A. dracunculus and H. officinalis by 20–35%. No differences in antioxidant activity and phenolics content were recorded at harvest between the control and AMF-inoculated plants, but the latter showed a significant increase in antioxidant status upon storage at high temperature and humidity compared to the untreated control. The enhancement of abiotic stress resistance during storage in plants inoculated with AMF was the highest in A. dracunculus, and the lowest in H. officinalis, while the untreated control plants showed a significant decrease in phenolics, ascorbic acid and chlorophyll content, as well as antioxidant activity, upon the abiotic stress. AMF inoculation differentially affected the mineral composition, increasing the accumulation of Se, I and Zn in A. dracunculus, and decreasing the levels of heavy metals and Co, Fe, Li, Mn in H. officinalis. Based on the outcome of the present research, AMF inoculation resulted in a significant enhancement of the overall performances of A. dracunculus, L. angustifolia and H. officinalis, and also in the improvement of plant antioxidant status upon storage in stress conditions.

(Co)polymerization of (−)-menthide and β-butyrolactone with yttrium-bis(phenolates): tuning material properties of sustainable polyesters

Sustainable thermoplastic elastomers derived from block copolymers of syndiotactic poly(3-hydroxybutyrate) and poly((−)-menthide) were synthesized via yttrium-mediated ring-opening polymerization.

Induction of essential oil production in Mentha x piperita by plant growth promoting bacteria was correlated with an increase in jasmonate and salicylate levels and a higher density of glandular trichomes

Plant growth promoting bacteria (PGPB) are agriculturally important soil bacteria that increase plant growth. We subjected peppermint to inoculation with three species of PGPB. After inoculation, the plants were sprayed with methyl jasmonate solution (MeJA) or SA (salicylic acid). Then, the plants were harvested and the plant growth parameters, trichome density, EO content and endogenous phytohormones were measured. Shoot fresh weight was reduced in plants inoculated and treated with MeJA whereas EO content varied depending on the MeJA concentration applied. Plants inoculated and treated with MeJA 2 mM showed the maximum increase in EO production, revealing a synergism between PGPB and MeJA. SA treatments also enhanced EO yield. The increased growth and EO production observed upon PGPB application were at least partly due to an increase in the JA and SA concentrations in the plant, as well as to an associated rise in the glandular trichome density.

Chemical Characterization and Biological Activities of Essential Oil Obtained from Mint Timija Cultivated under Mineral and Biological Fertilizers

Cultivation of mint timija (Mentha suaveolens subsp. timija (Briq.) Harley) constitutes a promising solution to the conservation and sustainable utilization of this Moroccan endemic and threatened species. Optimized agronomic practices require mineral and/or biological fertilizer applications. The aim of this study was to determine the effects of application of a complete (N, P, and K) mineral fertilizer and vesicular arbuscular mycorrhizae (VAM) inoculation on the composition, antioxidant, and insecticidal properties of mint timija essential oils (EOs). The GC-MS analyses identified 27 components representing more than 99.9% of the total oils. Menthone (40.7-49.3%), pulegone (31.3-36.5%), and isomenthone (2.5-4.4%) were found to be the main constituents. Cultivation of mint timija with mineral fertilizer and VAM inoculation induced an increase in menthone content and a parallel decrease of pulegone. Both treatments enhanced the antioxidant activity of the investigated EOs in all assays (IC₅₀ ranged from 2.34 ± 0.03 mg/mL to 6.82 ± 0.25 mg/mL), while no significant difference in the toxicities of these oils against Tribolium confusum du Val. has been observed. Overall, we conclude that cultivation using complete mineral fertilizer and VAM inoculation could be useful in modulating the chemical composition and enhancing the antioxidant activity of the EO of this endemic Moroccan species.

Arbuscular Mycorrhizal Fungi Increase the Phenolic Compounds Concentration in the Bark of the Stem of Libidibia Ferrea in Field Conditions

Background

Libidibia ferrea is a species particular to the caatinga presenting medicinal properties for containing bioactive compounds. The use of Arbuscular Mycorrhizal Fungi (AMF) can increase the production of biomolecules in the legume leaves; however, no light has been shed on the role of symbiosis in maximizing metabolites production in the bark of L. ferrea stem.

Objective

The aim was to select AMF that are efficient at increasing the production of phenolic compounds with medicinal properties in the bark of the L. ferrea stem.

Methods

The experiment was designed in randomized blocks with four inoculation treatments (plants pre-inoculated with Claroideoglomus etunicatum, with Gigaspora albida, with Acaulospora longula, and non-inoculated plants - control) with six repetitions. Thirteen months after the transplanting, the plants were pruned and the bark of the stem was collected; subsequently, this plant material was dried in a chamber. After the drying process, fractions of the bark of the stem were macerated in methanol. The extracts were further used for analyses of the biomolecules.

Results

The flavonoids concentration had an increase of, respectively, 236% and 186% in relation to the control for the treatments with A. longula and C. etunicatum; plants inoculated with A. longula had an increase of 47% in total tannins concentration compared with the non-inoculated control - a benefit that the proanthocyanidins did not present.

Conclusion

Applying inoculation with A. longula may be an alternative to increase the production of biomolecules of the secondary metabolism in the bark of the L. ferrea stem in field conditions.

Engineering Mycorrhizal Symbioses to Alter Plant Metabolism and Improve Crop Health

Creating sustainable bioeconomies for the 21st century relies on optimizing the use of biological resources to improve agricultural productivity and create new products. Arbuscular mycorrhizae (phylum Glomeromycota) form symbiotic relationships with over 80% of vascular plants. In return for carbon, these fungi improve plant health and tolerance to environmental stress. This symbiosis is over 400 million years old and there are currently over 200 known arbuscular mycorrhizae, with dozens of new species described annually. Metagenomic sequencing of native soil communities, from species-rich meadows to mangroves, suggests biologically diverse habitats support a variety of mycorrhizal species with potential agricultural, medical, and biotechnological applications. This review looks at the effect of mycorrhizae on plant metabolism and how we can harness this symbiosis to improve crop health. I will first describe the mechanisms that underlie this symbiosis and what physiological, metabolic, and environmental factors trigger these plant-fungal relationships. These include mycorrhizal manipulation of host genetic expression, host mitochondrial and plastid proliferation, and increased production of terpenoids and jasmonic acid by the host plant. I will then discuss the effects of mycorrhizae on plant root and foliar secondary metabolism. I subsequently outline how mycorrhizae induce three key benefits in crops: defense against pathogen and herbivore attack, drought resistance, and heavy metal tolerance. I conclude with an overview of current efforts to harness mycorrhizal diversity to improve crop health through customized inoculum. I argue future research should embrace synthetic biology to create mycorrhizal chasses with improved symbiotic abilities and potentially novel functions to improve plant health. As the effects of climate change and anthropogenic disturbance increase, the global diversity of arbuscular mycorrhizal fungi should be monitored and protected to ensure this important agricultural and biotechnological resource for the future.

Analysis of Plant Growth-Promoting Effects of Fluorescent Pseudomonas Strains Isolated from Mentha piperita Rhizosphere and Effects of Their Volatile Organic Compounds on Essential Oil Composition

Many species or strains of the genus Pseudomonas have been characterized as plant growth promoting rhizobacteria (PGPR). We used a combination of phenotypic and genotypic techniques to analyze the community of fluorescent Pseudomonas strains in the rhizosphere of commercially grown Mentha piperita (peppermint). Biochemical techniques, Amplified rDNA Restriction Analysis (ARDRA), and 16S rRNA gene sequence analysis revealed that the majority of the isolated native fluorescent strains were P. putida. Use of two Repetitive Sequence-based PCR (rep-PCR) techniques, BOX-PCR and ERIC-PCR, allowed us to evaluate diversity among the native strains and to more effectively distinguish among them. PGPR activity was tested for the native strains and reference strain P. fluorescens WCS417r. Micropropagated M. piperita plantlets were exposed to microbial volatile organic compounds (mVOCs) emitted by the bacterial strains, and plant biomass parameters and production of essential oils (EOs) were measured. mVOCs from 11 of the native strains caused an increase in shoot fresh weight. mVOCs from three native strains (SJ04, SJ25, SJ48) induced changes in M. pierita EO composition. The mVOCs caused a reduction of metabolites in the monoterpene pathway, for example menthofuran, and an increase in menthol production. Menthol production is the primary indicator of EO quality. The mVOCs produced by native strains SJ04, SJ25, SJ48, and strain WCS417r were analyzed. The obtained mVOC chromatographic profiles were unique for each of the three native strains analyzed, containing varying hydrocarbon, aromatic, and alogenic compounds. The differential effects of the strains were most likely due to the specific mixtures of mVOCs emitted by each strain, suggesting a synergistic effect occurs among the compounds present.

Arbuscular mycorrhiza differentially affects synthesis of essential oils in coriander and dill

Research on the role of arbuscular mycorrhizal fungi (AMF) in the synthesis of essential oils (EOs) by aromatic plants has seldom been conducted in field-relevant conditions, and then, only limited spectra of EO constituents have been analyzed. The effect was investigated of inoculation with AMF on the synthesis of a wide range of EO in two aromatic species, coriander (Coriandrum sativum) and dill (Anethum graveolens), in a garden experiment under outdoor conditions. Plants were grown in 4-l pots filled with soil, which was either γ-irradiated (eliminating native AMF) or left non-sterile (containing native AMF), and inoculated or not with an isolate of Rhizophagus irregularis. AMF inoculation significantly stimulated EO synthesis in both plant species. EO synthesis (total EO and several individual constituents) was increased in dill in all mycorrhizal treatments (containing native and/or inoculated AMF) compared to non-mycorrhizal plants. In contrast, EO concentrations in coriander (total EO and most constituents) were increased only in the treatment combining both inoculated and native AMF. A clear positive effect of AMF on EO synthesis was found for both aromatic plants, which was, however, specific for each plant species and modified by the pool of AMF present in the soil.

Plant growth-promoting effects of native Pseudomonas strains on Mentha piperita (peppermint): an in vitro study

Plant growth-promoting rhizobacteria (PGPR) affect growth of host plants through various direct and indirect mechanisms. Three native PGPR (Pseudomonas putida) strains isolated from rhizospheric soil of a Mentha piperita (peppermint) crop field near Córdoba, Argentina, were characterised and screened in vitro for plant growth-promoting characteristics, such as indole-3-acetic acid (IAA) production, phosphate solubilisation and siderophore production, effects of direct inoculation on plant growth parameters (shoot fresh weight, root dry weight, leaf number, node number) and accumulation and composition of essential oils. Each of the three native strains was capable of phosphate solubilisation and IAA production. Only strain SJ04 produced siderophores. Plants directly inoculated with the native PGPR strains showed increased shoot fresh weight, glandular trichome number, ramification number and root dry weight in comparison with controls. The inoculated plants had increased essential oil yield (without alteration of essential oil composition) and biosynthesis of major essential oil components. Native strains of P. putida and other PGPR have clear potential as bio-inoculants for improving productivity of aromatic crop plants. There have been no comparative studies on the role of inoculation with native strains on plant growth and secondary metabolite production (specially monoterpenes). Native bacterial isolates are generally preferable for inoculation of crop plants because they are already adapted to the environment and have a competitive advantage over non-native strains.

Inoculation with arbuscular mycorrhizal fungi improves the nutritional value of tomatoes

Arbuscular mycorrhizal (AM) fungi can affect many different micronutrients and macronutrients in plants and also influence host volatile compound synthesis. Their effect on the edible portions of plants is less clear. Two separate studies were performed to investigate whether inoculation by AM fungi (Rhizophagus irregularis, Funneliformis mosseae, or both) can affect the food quality of tomato fruits, in particular common minerals, antioxidants, carotenoids, a suite of vitamins, and flavor compounds (sugars, titratable acids, volatile compounds). It was found that AM fungal inoculation increased the nutrient quality of tomato fruits for most nutrients except vitamins. Fruit mineral concentration increased with inoculation (particularly N, P, and Cu). Similarly, inoculated plants had fruit with higher antioxidant capacity and more carotenoids. Furthermore, five volatile compounds were significantly higher in AM plants compared with non-AM controls. Taken together, these results show that AM fungi represent a promising resource for improving both sustainable food production and human nutritional needs.

Arbuscular mycorrhiza increase artemisinin accumulation in Artemisia annua by higher expression of key biosynthesis genes via enhanced jasmonic acid levels

It is becoming increasingly evident that the formation of arbuscular mycorrhiza (AM) enhances secondary metabolite production in shoots. Despite mounting evidence, relatively little is known about the underlying mechanisms. This study suggests that increase in artemisinin concentration in Artemisia annua colonized by Rhizophagus intraradices is due to altered trichome density as well as transcriptional patterns that are mediated via enhanced jasmonic acid (JA) levels. Mycorrhizal (M) plants had higher JA levels in leaf tissue that may be due to induction of an allene oxidase synthase gene (AOS), encoding one of the key enzymes for JA production. Non-mycorrhizal (NM) plants were exogenously supplied with a range of methyl jasmonic acid concentrations. When leaves of NM and M plants with similar levels of endogenous JA were compared, these matched closely in terms of shoot trichome density, artemisinin concentration, and transcript profile of artemisinin biosynthesis genes. Mycorrhization increased artemisinin levels by increasing glandular trichome density and transcriptional activation of artemisinin biosynthesis genes. Transcriptional analysis of some rate-limiting enzymes of mevalonate and methyl erythritol phosphate (MEP) pathways revealed that AM increases isoprenoids by induction of the MEP pathway. A decline in artemisinin concentration in shoots of NM and M plants treated with ibuprofen (an inhibitor of JA biosynthesis) further confirmed the implication of JA in the mechanism of artemisinin production.

Impact of plant growth promoting Pseudomonas monteilii PsF84 and Pseudomonas plecoglossicida PsF610 on metal uptake and production of secondary metabolite (monoterpenes) by rose-scented geranium (Pelargonium graveolens cv. bourbon) grown on tannery sludge amended soil

Bacterial strains PsF84 and PsF610 were isolated from tannery sludge polluted soil, Jajmau, Kanpur, India. 16S rRNA gene sequence and phylogenetic analysis confirmed the taxonomic affiliation of PsF84 as Pseudomonas monteilii and PsF610 as Pseudomonas plecoglossicida. A greenhouse study was carried out with rose-scented geranium (Pelargonium graveolenscv. bourbon) grown in soil treated with tannery sludge in different proportions viz. soil: sludge ratio of 100:0, 25:75, 50:50, 75:25 and 0:100 to evaluate the effects of bacterial inoculation on the heavy metal uptake. The isolates solubilized inorganic phosphorus and were capable of producing indole acetic acid (IAA) and siderophore. The isolate PsF84 increased the dry biomass of shoot by 44%, root by 48%, essential oil yield 43% and chlorophyll by 31% respectively over uninoculated control. The corresponding increase with the isolate PsF610 were 38%, 40%, 39% and 28%, respectively. Scanning electron microscopic (SEM) studies reveal that the Cr(VI) accumulation resulted in breakdown of vascular bundles and sequesters Cr(VI) in roots. The glandular trichomes (GT) were investigated using SEM studies as these glands are probably the main site of essential oil synthesis. Owing to its wide action spectrum, these isolates could serve as an effective metal sequestering and bioinoculants due to the production of IAA, siderophore and solubilization of phosphate for geranium in metal-stressed soil. The present study has provided a new insight into the phytoremediation of metal-contaminated soil.

Arbuscular mycorrhizal symbiosis for sustainable cultivation of Chinese medicinal plants: a promising research direction

Arbuscular mycorrhizal (AM) are symbiotic systems in nature and have great significance in promoting the growth and stress resistance of medicinal plants. During our literature search from the Chinese Scientific Information Database (Chinese National Knowledge Infrastructure, CNKI) we obtained 65 articles with "AM fungi" and "medicinal plant" as the key words, which indicates that in China, research efforts on these topics have been increasing. The main purposes of this review are to discuss the effects of mycorrhiza on the active ingredients of Chinese medicinal plants in comparison with results obtained in other plants in studies conducted by the international research community, and to introduce works published in Chinese journals to international colleagues.

The greater effectiveness of Glomus mosseae and Glomus intraradices in improving productivity, oil content and tolerance of salt-stressed menthol mint (Mentha arvensis)

BACKGROUND

Mentha arvensis is cultivated in large parts of the world for its menthol-rich essential oil. The study investigates the potential of four mycorrhizal fungi, viz. Glomus mosseae (Gm), Glomus aggregatum (Ga), Glomus fasciculatum (Gf) and Glomus intraradices (Gi) in alleviating NaCl-induced salt stress in Mentha arvensis cv. Kosi and establishes the specificity of interaction between different mycorrhizal species and their effectiveness in mitigating salt stress in Mentha arvensis. Mycorrhizal and non-mycorrhizal Mentha plants were subjected to NaCl-induced salinity.

RESULTS

Among the four Glomus species, Gm and Gi reduced salt-induced herb yield losses: a loss of 27.53% and 25.58% respectively under salt stress in comparison to 51.00% in non-mycorrhizal M. arvensis salt-stressed plants. Gm- and Gi-inoculated plants also recorded higher leaf:stem ratio, oil content, and oil yield and menthol concentration in essential oil under both saline and non-saline conditions.

CONCLUSION

Better performance in terms of herb yield, and oil content and yield was observed in Gi- and Gm-inoculated M. arvensis plants, suggesting the capability of Gi and Gm in protecting plants from the detrimental effects of salt stress; beneficial effects of arbuscular mycorrhizal fungi, however, may vary with host and environment.

Arbuscular mycorrhizal symbiosis and active ingredients of medicinal plants: current research status and prospectives

Medicinal plants have been used world-wide for thousands of years and are widely recognized as having high healing but minor toxic side effects. The scarcity and increasing demand for medicinal plants and their products have promoted the development of artificial cultivation of medicinal plants. Currently, one of the prominent issues in medicinal cultivation systems is the unstable quality of the products. Arbuscular mycorrhiza (AM) affects secondary metabolism and the production of active ingredients of medicinal plants and thus influence the quality of herbal medicines. In this review, we have assembled, analyzed, and summarized the effects of AM symbioses on secondary metabolites of medicinal plants. We conclude that symbiosis of AM is conducive to favorable characteristics of medicinal plants, by improving the production and accumulation of important active ingredients of medicinal plants such as terpenes, phenols, and alkaloids, optimizing the composition of different active ingredients in medicinal plants and ultimately improving the quality of herbal materials. We are convinced that the AM symbiosis will benefit the cultivation of medicinal plants and improve the total yield and quality of herbal materials. Through this review, we hope to draw attention to the status and prospects of, and arouse more interest in, the research field of medicinal plants and mycorrhiza.

Preservation at ultra-low temperature of in vitro cultured arbuscular mycorrhizal fungi via encapsulation-drying

At present, over 300 species of arbuscular mycorrhizal fungi (AMF) have been identified, most of which being stored in international collections. Their maintenance is mostly achieved in greenhouse via continuous culture on trap plants or in vitro in association with excised root organs. Both methods are work-intensive and for the former present the risk of unwanted contaminations. The in vitro root organ culture of AMF has become an alternative preventing contamination. Nevertheless, the risk for somaclonal variation during the sub-cultivation process cannot be excluded. A method for the long-term conservation that guarantees the stability of the biological material is thus highly demanded to preserve the microorganisms and their genetic stability. Here, 12 AMF isolates cultured in vitro in association with excised carrot roots were encapsulated in alginate beads and subsequently cryopreserved. Several protocols were tested taking into consideration culture age, alginate bead pre-drying, and rate of decrease in temperature. The viability of the AMF isolates was estimated by the percentage of potentially infective beads (%PIB) that measure the % of beads that contain at least one germinated propagule. Thermal behaviour of alginate beads was analysed by a differential thermal calorimeter before and after drying to estimate the frozen and unfrozen water during the cryopreservation process. It was shown that the spore damage was directly related to ice formation during cryopreservation. The encapsulation and culture age were also determinant parameters for the successful cryopreservation. Irrespective of the AMF isolate, the optimal procedure for cryopreservation comprised five steps: (1) the encapsulation of propagules (i.e. spores and mycorrhizal root pieces) isolated from 5m old cultures, (2) the incubation overnight in trehalose (0.5M), (3) the drying during 48h at 27°C, (4) the cryopreservation in the freezer at -130°C following a two-step decrease in temperature: a fast decrease (∼12°Cmin(-1)) from room temperature (+20°C) to -110°C followed by a slow decrease in temperature (∼1°Cmin(-1)) from -110°C to -130°C, and (5) the direct thawing in a water bath (+35°C). The % PIB was above 70 % for all the isolates and even above 95% for 11 out of the 12 isolates after several months of storage at ultra-low temperature. All the isolates kept their capacity to associate to an excised carrot root in vitro and to reproduce the fungal life cycle with the production of several hundreds to thousands of spores after 2m. This method opens the door for the long-term maintenance at ultra-low temperature of AMF isolates within international repositories.

Influence of Inoculation with the Endomycorrhizal Fungi and Trichoderma viride on Morphological and Physiological Growth Parameters of Rauwolfia serpentina Benth. Ex. Kurtz

Two arbuscular mycorrhizal fungi, Glomus mosseae and Acaulospora laevis either alone or in combination with Trichoderma viride showed the dependence of Rauwolfia serpentina on endomycorrhizal fungi. After 60 days, G. mosseae singly or in combination with Trichoderma viride showed enhanced height increment compared to control plants. Maximum phosphorus content was shown by plants treated with G. mosseae plus T. viride (0.444 ± 2.62) in roots and (0.437 ± 4.71) in shoots. Phosphorus content in roots was more than that in shoots. Chlorophyll content and stomatal conductivity also showed similar trend.

Arbuscular mycorrhizal fungi associated with Artemisia umbelliformis Lam, an endangered aromatic species in Southern French Alps, influence plant P and essential oil contents

Root colonization by arbuscular mycorrhizal (AM) fungi of Artemisia umbelliformis, investigated in natural and cultivated sites in the Southern Alps of France, showed typical structures (arbuscules, vesicles, hyphae) as well as spores and mycelia in its rhizosphere. Several native AM fungi belonging to different Glomeromycota genera were identified as colonizers of A. umbelliformis roots, including Glomus tenue, Glomus intraradices, G. claroideum/etunicatum and a new Acaulospora species. The use of the highly mycorrhizal species Trifolium pratense as a companion plant impacted positively on mycorrhizal colonization of A. umbelliformis under greenhouse conditions. The symbiotic performance of an alpine microbial community including native AM fungi used as inoculum on A. umbelliformis was evaluated in greenhouse conditions by comparison with mycorrhizal responses of two other alpine Artemisia species, Artemisia glacialis and Artemisia genipi Weber. Contrary to A. genipi Weber, both A. umbelliformis and A. glacialis showed a significant increase of P concentration in shoots. Volatile components were analyzed by GC-MS in shoots of A. umbelliformis 6 months after inoculation. The alpine microbial inoculum increased significantly the percentage of E-β-ocimene and reduced those of E-2-decenal and (E,E)-2-4-decadienal indicating an influence of alpine microbial inoculum on essential oil production. This work provides practical indications for the use of native AM fungi for A. umbelliformis field culture.

Root colonisation by the arbuscular mycorrhizal fungus Glomus intraradices alters the quality of strawberry fruits (Fragaria x ananassa Duch.) at different nitrogen levels

BACKGROUND

Arbuscular mycorrhizal fungi (AMF) increase the uptake of minerals from the soil, thus improving the growth of the host plant. Nitrogen (N) is a main mineral element for plant growth, as it is an essential component of numerous plant compounds affecting fruit quality. The availability of N to plants also affects the AMF-plant interaction, which suggests that the quality of fruits could be affected by both factors. The objective of this study was to evaluate the influence of three N treatments (3, 6 and 18 mmol L(-1)) in combination with inoculation with the AMF Glomus intraradices on the quality of strawberry fruits. The effects of each factor and their interaction were analysed.

RESULTS

Nitrogen treatment significantly modified the concentrations of minerals and some phenolic compounds, while mycorrhization significantly affected some colour parameters and the concentrations of most phenolic compounds. Significant differences between fruits of mycorrhizal and non-mycorrhizal plants were found for the majority of phenolic compounds and for some minerals in plants treated with 6 mmol L(-1) N. The respective values of fruits of mycorrhizal plants were higher.

CONCLUSION

Nitrogen application modified the effect of mycorrhization on strawberry fruit quality.

Role of essential oils in control of Rhizoctonia damping-off in tomato with bioactive Monarda herbage

Plants in the genus Monarda produce complex essential oils that contain antifungal compounds. The objectives of this research were to identify selections of monarda that reduce Rhizoctonia damping-off of tomato, and to determine relationships between essential oil composition of 13 monarda herbages (dried and ground leaves) and disease suppression. Herbages were grouped into five chemotypes, based on essential oil composition and effective concentrations for reducing growth by 50% for Rhizoctonia solani. Replicated and repeated disease control assays were conducted with monarda herbages in greenhouse medium, with or without Rhizoctonia. Percent survival, seedling height, and stem diameter were evaluated at 8 weeks. Survival, seedling height, and stem diameter in herbage-only treatments were not different from the control (no-herbage, no-pathogen) for most herbage treatments. In the pathogen control (no-herbage + Rhizoctonia), seedling survival was 10% that of the control. In pathogen-infested media, seedling survival ranged from 65 to 80% for treatments with thymol chemotypes and 55 to 65% for carvacrol chemotypes. Effective control of Rhizoctonia damping-off was correlated with phenolic monoterpenes; herbages classified as carvacrol chemotypes effectively protected tomato seedlings from Rhizoctonia damping-off disease without phytotoxicity. This study provides evidence that monarda herbages have potential as growing media amendments for control of Rhizoctonia damping-off disease.

Essential Oil Content and Composition, Nutrient and Mycorrhizal Status of Some Aromatic and Medicinal Plants of Northern Greece

A field survey was conducted in three northern Greek mountain areas (Chortiatis, Ossa, and Pieria) to investigate the mycorrhizal and nutritional status, and the essential oil content and composition of common medicinal and aromatic plants. A range of values for nutrient status and essential oil contents and composition was established. All plants were found to be mycorrhizal, including Achillea coarctata Poir., Micromeria juliana (L.) Bentham ex Reichenb., and Salvia sclarea L.;. these three are reported as being mycorrhizal for the first time. Arbuscular mycorrhizal fungal root colonization was highest in Pieria, exceeding 80% for all 15 plants sampled, and lower in Chortiatis and Ossa.

Systemic induction of monoterpene biosynthesis in Origanumxmajoricum by soil bacteria

Italian oregano (Origanumxmajoricum) was subjected to root system inoculation with three species of plant growth-promoting rhizobacteria (PGPRs) (Pseudomonas fluorescens, Bacillus subtilis, Azospirillum brasilense), and essential oil (EO) content and plant growth were measured. Composition of monoterpenes, a major EO component, was analyzed qualitative and quantitatively by gas chromatography. Total EO yield for plants inoculated with P. fluorescens or A. brasilense was 3.57 and 3.41 microg/mg fresh weight, respectively, approximately 2.5-fold higher than controls, without change of quantitative oil composition. The major EO compounds, cis- and trans-sabinene hydrate, gamma-terpinene, carvacrol, and thymol, showed increased biosynthesis. Carvacrol was the only terpene showing significant increase of R% in plants inoculated with A. brasilense. Plant growth parameters (shoot and root fresh and dry weights, numbers of leaves and nodes) were evaluated. Shoot fresh weight was significantly increased by all three PGPR species, but only P. fluorescens and A. brasilense increased root dry weight. These two species have clear commercial potential for economic cultivation of O.xmajoricum. Knowledge of the factors affecting yield and accumulation of monoterpenes is essential for improving production of these economically important plant compounds.

Soil bacteria elevate essential oil accumulation and emissions in sweet basil

Plant growth-promoting rhizobacteria ameliorate environmental conditions for plants by facilitating nutrient uptake and mitigating disease susceptibility. While volatile chemicals from certain soil microbes are sufficient to elicit growth and defense responses in Arabidopsis, whether such volatile signals can induce essential oil accumulation and chemical emissions has yet to be reported. Here, we provide biochemical evidence that the plant growth-promoting soil bacterium Bacillus subtilis GB03 releases volatile chemicals that elevate fresh weight essential oil accumulation and emissions along with plant size in the terpene-rich herb sweet basil (Ocimum basilicum). The two major essential oil components from sweet basil, alpha-terpineol and eugenol, increased ca. 2- and 10-fold, respectively, in plants exposed to GB03 volatiles or with root inoculation as compared to water controls. On a fresh and dry weight basis, shoot and root biomass increases of ca. 2-fold were observed with GB03 volatile exposure or GB03 media inoculation as compared with controls. In testing the efficacy of GB03 volatiles to trigger plant growth and secondary compound production, a physical partition separating roots from bacterial media was provided to preclude nonvolatile microbial elicitors from contributing to GB03-stimulated basil responses. These results demonstrate that volatile bacterial elicitors can concomitantly increase essential oil production and biomass in an herbaceous species rich in commercially valued essential oils.

The effect of arbuscular mycorrhizal fungal isolates on the development and oleoresin production of micropropagated Zingiber officinale

We have investigated the effects of phosphate fertilization and inoculation with isolates of arbuscular mycorrhizal fungi Scutellospora heterogama SCT120E, Gigaspora decipiens SCT304A, Acaulospora koskei SCT400A, Entrophospora colombiana SCT115, and an assemblage (Mix) of all four isolates on growth, development and oleoresin production of micropropagated Zingiber officinale. After 120 and 210 d of growth, the Mix and phosphorus addition significantly increased shoot height relative to control plants. Phosphorus addition was the only treatment resulting in significantly large shoot dry biomass relative to control after 120 d. No statistical differences were observed between treatments for shoot dry biomass after 210 d and for fine and coarse root biomass at both harvests. Inoculation with S. herogama and G. decipiens resulted in larger yields of oleoresin, corresponding to 3.48% and 1.58% of rhizome fresh biomass respectively. Based on retention index and mass spectrometry, we have characterized the following constituents present in ginger rhizomes: ar-curcumene, zingiberene, γ-cadinene, bisabolene, δ- or α-cadinene and farnesol. Two other constituents were characterized as possible members of the gingerol class. Results suggest that the screening and inoculation of arbuscular mycorrhizal fungi in ginger plants is a feasible procedure to increase the oleoresin production of Z. officinale and consequently increase the aggregate value of ginger rhizome production.

INFLUÊNCIA DE FUNGOS MICORRÍZICOS ARBUSCULARES NO DESENVOLVIMENTO DE PLANTAS DE ALECRIM E MANJERICÃO

RESUMO O objetivo do presente trabalho foi avaliar a influência dos fungos micorrízicos arbusculares Glomus etunicatum Becker & Gerd. e Glomus clarum Nicol. & Schenck, no desenvolvimento de plantas de alecrim (Rosmarinusofficinalis L.) e manjericão (Ocimum basilicumL.) inoculadas, separadamente, em condições controladas. Utilizou-se substrato autoclavado composto por uma parte de areia e uma de terra; o inóculo constou de esporos [500 esporos de G. etunicatum (50mL-1) de solo e 700 esporos de G. clarum(50 mL-1) de solo] e ainda fragmentos de raízes infectadas e micélio. Em cada tipo de planta inoculada foram avaliados: altura das plantas (AP), peso da matéria seca da parte aérea (MSPA), peso da matéria fresca das raízes (MFR), esporulação (E) e colonização radicular (CR). O delineamento experimental foi inteiramente casualizado com três tratamentos (GE – G.etunicatum; GC – G.clarum e T - Testemunha), 16 repetições para o alecrim e 12 para o manjericão. Cada parcela foi representada por um vaso, contendo uma planta para o alecrim e três para o manjericão. No alecrim , G. clarum mostrou-se mais eficiente do que G. etunicatum em AP (24,15%), MSPA (67,16%) e E (48,16%); por outro lado, G. clarum apresentou CR menor do que G. etunicatum. Em relação às plantas testemunha, G. clarum diferiu destas em todas as variáveis analisadas, porém G. etunicatum não diferiu das plantas testemunha em AP e MSPA. No manjericão, em relação a todas as variáveis analisadas , G. clarum diferiu da testemunha e de G. etunicatum e, este, foi semelhante ao tratamento controle em todas as variáveis, exceto para CR e E. Comparado ao controle, G. clarum proporcionou ao manjericão aumentos de 45,49% em AP e 93,10% em MSPA.

Volatile terpenoids of endophyte-free and infected peppermint (Mentha piperita L.): chemical partitioning of a symbiosis

The study reports the effects on volatiles of an endophytic fungus inhabiting asymptomatically the leaves of peppermint. By means of headspace solid-phase microextraction (HS-SPME) and gaschromatography-mass spectrometry (GC-MS) terpenoids were sampled in time course from the head space of peppermint leaves and roots. After removal of the mycelium from peppermint tissues, fungal volatiles were analyzed and compared with those of pure fungal cultures. In the presence of the endophyte, the relative amount of all main compounds increased in leaves. Starting from the first 14 d of culture, (-)-menthone and (+)-neomenthol were consistently higher than in control plants. On the contrary, (+)-menthofuran increased only by 28 d of culture. Root volatiles were also dramatically altered by the presence of the fungus, with (+)-pulegone accounting for at least 44% of the total volatile emission. (+)-Pulegone was also the main compound of PGP-HSF mycelium isolated from peppermint roots. The sesquiterpenoid cuparene was found as a novel compound of peppermint leaf headspace and was a main volatile of ex planta and pure culture mycelia. The chemical spectrum of terpenoids and their distribution among peppermint roots, leaves, and mycelia are likely to account for a fine regulation of the mutualism in planta and for the acquisition by the fungus of novel metabolic competences.

Arbuscular mycorrhizal fungi can induce the production of phytochemicals in sweet basil irrespective of phosphorus nutrition

The potential of three arbuscular mycorrhizal fungi (AMF) to enhance the production of antioxidants (rosmarinic and caffeic acids, RA and CA) was investigated in sweet basil (Ocimum basilicum). After adjusting phosphorus (P) nutrition so that P concentrations and yield were matched in AM and non-mycorrhizal (NM) plants we demonstrated that Glomus caledonium increased RA and CA production in the shoots. Glomus mosseae also increased shoot CA concentration in basil under similar conditions. Although higher P amendments to NM plants increased RA and CA concentrations, there was higher production of RA and CA in the shoots of AM plants, which was not solely due to better P nutrition. Therefore, AMF potentially represent an alternative way of promoting growth of this important medicinal herb, as natural ways of growing such crops are currently highly sought after in the herbal industry.

Effects of three AM fungi on growth, distribution of glandular hairs, and essential oil production in Ocimum basilicum L. var. Genovese

The essential oils of basil are widely used in the cosmetic, pharmaceutical, food, and flavoring industries. Little is known about the potential of arbuscular mycorrhizal (AM) fungi to affect their production in this aromatic plant. The effects of colonization by three AM fungi, Glomus mosseae BEG 12, Gigaspora margarita BEG 34, and Gigaspora rosea BEG 9 on shoot and root biomass, abundance of glandular hairs, and essential oil yield of Ocimum basilicum L. var. Genovese were studied. Plant P content was analyzed in the various treatments and no differences were observed. The AM fungi induced various modifications in the considered parameters, but only Gi. rosea significantly affected all of them in comparison to control plants or the other fungal treatments. It significantly increased biomass, root branching and length, and the total amount of essential oil (especially alpha-terpineol). Increased oil yield was associated to a significantly larger number of peltate glandular trichomes (main sites of essential oil synthesis) in the basal and central leaf zones. Furthermore, Gi. margarita and Gi. rosea increased the percentage of eugenol and reduced linalool yield. Results showed that different fungi can induce different effects in the same plant and that the essential oil yield can be modulated according to the colonizing AM fungus.

Is plant performance limited by abundance of arbuscular mycorrhizal fungi? A meta-analysis of studies published between 1988 and 2003

We conducted meta-analyses of 290 published field and glasshouse trials to determine the effects of various agricultural practices on mycorrhizal colonization in nonsterile soils, and the consequence of those effects on yield, biomass, and phosphorus (P) concentration. Mycorrhizal colonization was increased most by inoculation (29% increase), followed by shortened fallow (20%) and reduced soil disturbance (7%). The effect of crop rotation depended on whether the crop was mycorrhizal. Increased colonization resulted in a yield increase in the field of 23% across all management practices. Biomass at harvest and shoot P concentration in early season were increased by inoculation (57 and 33%, respectively) and shortened fallow (55 and 24%). Reduced disturbance increased shoot P concentration by 27%, but biomass was not significantly affected. Biomass was significantly reduced in 2% of all trials in which there was a significant increase in colonization. Irrespective of management practice, an increased mycorrhizal colonization was less likely to increase biomass if either soil P or indigenous inoculum potential was high.

Seasonality of arbuscular mycorrhizal symbiosis and dark septate endophytes in a grassland site in southwest China

Arbuscular mycorrhizal and dark septate endophytic fungal colonization in a grassland in Kunming, southwest China, was investigated monthly over one year. All plant roots surveyed were co-colonized by arbuscular mycorrhizal and dark septate endophytic fungi in this grassland. Both arbuscular mycorrhizal and dark septate endophytic fungal colonization fluctuated significantly throughout the year, and their seasonal patterns were different in each plant species. The relationships between environmental (climatic and edaphic) factors and fungal colonization were also studied. Correlation analysis demonstrated that arbuscular mycorrhizal colonization was significantly correlative with environmental factors (rainfall, sunlight hours, soil P, etc.), but dark septate endophytic fungal colonization was only correlative with relative humidity and sunlight hours.

Improved growth and essential oil yield and quality in Foeniculum vulgare mill on mycorrhizal inoculation supplemented with P-fertilizer

Two arbuscular mycorrhizal (AM) fungi Glomus macrocarpum and Glomus fasciculatum significantly improved growth and essential oil concentration of Foeniculum vulgare Mill. However, AM inoculation of plants along with phosphorus fertilization significantly enhanced growth, P-uptake and essential oil content of plants compared to either of the components applied separately. Among the two fungal inoculants, G. fasciculatum registered the highest growth at both levels of phosphorus used with up to 78% increase in essential oil concentration of fennel seeds over non-mycorrhizal control. The essential oil characterization by gas liquid chromatography revealed that the level of anethol was significantly enhanced on mycorrhization.