Arbuscular Mycorrhizal Fungus Funneliformis Mosseae Research Articles

Coordinated influence of Funneliformis mosseae and different plant growth-promoting bacteria on growth, root functional traits, and nutrient acquisition by maize.

Rhizospheric interactions among plant roots, arbuscular mycorrhizal fungi, and plant growth-promoting bacteria (PGPB) can enhance plant health by promoting nutrient acquisition and stimulating the plant immune system. This pot experiment, conducted in autoclaved soil, explored the synergistic impacts of the arbuscular mycorrhizal fungus Funneliformis mosseae with four individual bacterial strains, viz.: Cronobacter sp. Rz-7, Serratia sp. 5-D, Pseudomonas sp. ER-20 and Stenotrophomonas sp. RI-4A on maize growth, root functional traits, root exudates, root colonization, and nutrient uptake. The comprehensive biochemical characterization of these bacterial strains includes assessments of mineral nutrient solubilization, plant hormone production, and drought tolerance. The results showed that all single and interactive treatments of the mycorrhizal fungus and bacterial strains improved maize growth, as compared with the control (no fungus or PGPB). Among single treatments, the application of the mycorrhizal fungus was more effective than the bacterial strains in stimulating maize growth. Within the bacterial treatments, Serratia sp. 5-D and Pseudomonas sp. ER-20 were more effective in enhancing maize growth than Cronobacter sp. Rz-7 and Stenotrophomonas sp. RI-4A. All bacterial strains were compatible with Funneliformis mosseae to improve root colonization and maize growth. However, the interaction of mycorrhiza and Serratia sp. 5-D (M + 5-D) was the most prominent for maize growth improvement comparatively to all other treatments. We observed that bacterial strains directly enhanced maize growth while indirectly promoting biomass accumulation by facilitating increased mycorrhizal colonization, indicating that these bacteria acted as mycorrhizal helper bacteria.

Genetic and functional traits limit the success of colonisation by arbuscular mycorrhizal fungi in a tomato wild relative.

To understand whether domestication had an impact on susceptibility and responsiveness to arbuscular mycorrhizal fungi (AMF) in tomato (Solanum lycopersicum), we investigated two tomato cultivars ("M82" and "Moneymaker") and a panel of wild relatives including S. neorickii, S. habrochaites and S. pennellii encompassing the whole Lycopersicon clade. Most genotypes revealed good AM colonisation levels when inoculated with the AMF Funneliformis mosseae. By contrast, both S. pennellii accessions analysed showed a very low colonisation, but with normal arbuscule morphology, and a negative response in terms of root and shoot biomass. This behaviour was independent of fungal identity and environmental conditions. Genomic and transcriptomic analyses revealed in S. pennellii the lack of genes identified within QTLs for AM colonisation, a limited transcriptional reprogramming upon mycorrhization and a differential regulation of strigolactones and AM-related genes compared to tomato. Donor plants experiments indicated that the AMF could represent a cost for S. pennellii: F. mosseae could extensively colonise the root only when it was part of a mycorrhizal network, but a higher mycorrhization led to a higher inhibition of plant growth. These results suggest that genetics and functional traits of S. pennellii are responsible for the limited extent of AMF colonisation.

Seven-year long-term inoculation with Funneliformis mosseae increases maize yield and soil carbon storage evidenced by in situ 13C-labeling in a dryland

Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with roots of most plants, contributing to plant water uptake and soil carbon (C) sequestration. However, the interactive contribution and of long-term field AMF inoculation and water conservation on maize yield and soil organic carbon (SOC) sequestration in drylands remain largely unknown. After 7-year long-term field inoculation with AMF Funneliformis mosseae, AMF suppression by fungicide benomyl, and no-AMF/no-benomyl control, and two water conservation practices of half-film and full-film mulching (∼50 % and ∼100 crop planted area covered with plastic film), this study thus applied in situ 13CO2-C labeling and high-throughput sequencing to quantify newly photosynthetically assimilated C into different soil C pools including soil aggregates and respiration, and their effects on maize growth and productivity. Results showed that 7-year long-term AMF inoculation significantly increased the relative abundance of F. mosseae in rhizosphere soil and root AMF colonization, indicating that F. mosseae successfully dominated in AMF communities. Compared to no-AMF/no-benomyl control, AMF colonization significantly increased shoot biomass and maize yield by 17.9 % and 20.3 % while mitigated the less water conservation effects of half-film mulching on maize performance. The SOC content under field AMF inoculation SOC was increased from 7.9 to 8.4 g kg−1 and also the mean weight diameter of aggregates (1.21 to 1.35), e.g. aggregate stability. After 1 and/or 40 days 13C labeling, the enhanced 13C translocations into macro-aggregates with decreased 13C emissions from microbial decomposition under field AMF inoculation had contributed to SOC conservation in bulk soil. These results suggest that AMF inoculation in dryland crops is promising to increase crop yield while promoting more atmospheric CO2 fixation in soil aggregates. A long-term field AMF inoculation will enhance our understanding of applying beneficial mycorrhizal fungi to enhance soil C sequestration and also crop yield via plant-fixed atmospheric CO2 in semi-arid and arid farmlands.

Arbuscular mycorrhizal fungi improve selenium uptake by modulating root transcriptome of rice (Oryza sativa L.).

Although selenium (Se) is an essential trace element in humans, the intake of Se from food is still generally inadequate throughout the world. Inoculation with arbuscular mycorrhizal fungi (AMF) improves the uptake of Se in rice (Oryza sativa L.). However, the mechanism by which AMF improves the uptake of Se in rice at the transcriptome level is unknown. Only a few studies have evaluated the effects of uptake of other elements in rice under the combined effects of Se and AMF. In this study, Se combined with the AMF Funneliformis mosseae (Fm) increased the biomass and Se concentration of rice plants, altered the pattern of ionomics of the rice roots and shoots, and reduced the antagonistic uptake of Se with nickel, molybdenum, phosphorus, and copper compared with the treatment of Se alone, indicating that Fm can enhance the effect of fertilizers rich in Se. Furthermore, a weighted gene co-expression network analysis (WGCNA) showed that the hub genes in modules significantly associated with the genes that contained Se and were related to protein phosphorylation, protein serine/threonine kinase activity, membrane translocation, and metal ion binding, suggesting that the uptake of Se by the rice roots may be associated with these genes when Fm and Se act in concert. This study provides a reference for the further exploration of genes related to Se uptake in rice under Fm treatment.

Arbuscular Mycorrhizal Fungus Funneliformis mosseae Improves Soybean Growth Even in Soils with Good Nutrition

Arbuscular mycorrhizal fungi (AMF) improve plant growth and may be useful in maintaining and even restoring soil. However, data on the latter function are sparse and only indirect, which is especially true for conventional management conditions with adequate nutrient availability. Our study focused on utilizing the prevalent AMF species, Funneliformis mosseae, to enhance Glycine max production, while also exploring its partly explored impact on soil aggregation. Working in greenhouse conditions, we examined whether, in a nutrient-sufficient environment, AMF would improve crop biomass accumulation and nutrition, as well as the stability of soil aggregates (SAS). We also looked for a synergistic effect of dual inoculation using AMF and symbiotic rhizobium. Plants were or were not inoculated with AMF or Bradyrhizobium japonicum in a two-factorial design. AMF inoculation increased soybean biomass, but AMF inoculation had no impact on P and N input to the shoots. Mycorrhiza did not affect either glomalin abundance or SAS. All the impacts were, however, independent from rhizobial inoculation, which was ineffective in this nutrient-available environment. Our assay suggests that arbuscular mycorrhiza may have a positive effect on soybean growth even under conventional management with adequate nutrition. The positive effects of AMF on soybean growth, together with the fact that AMF generally do not thrive in good nutrient availability, should be taken into account when planning mineral fertilization levels.

Epigenetic control is involved in molecular dialogue in plant-microbe symbiosis.

This article is a Commentary on Vigneaud et al. (2023), 238: 2561–2577.

Arbuscular Mycorrhizal Fungi Increase Nutritional Quality of Soilless Grown Lettuce while Overcoming Low Phosphorus Supply.

Lettuce is widely used for its healthy properties, and it is of interest to increase them with minimal environmental impact. The purpose of this work was to evaluate the effect of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae in lettuce plants (Lactuca sativa L. cv. Salinas) cultivated in a soilless system with sub-optimal phosphorus (P) compared with non-inoculated controls at two different P concentrations. Results show that lettuce inoculation with the selected AMF can improve the growth and the nutritional quality of lettuce even at sub-optimal P. Leaf content of chlorophylls, carotenoids, and phenols, known as important bioactive compounds for human health, was higher in mycorrhizal lettuce plants compared with non-mycorrhizal plants. The antioxidant capacity in AMF plants showed higher values compared with control plants grown at optimal P nutrition level. Moreover, leaf gas exchanges were higher in inoculated plants than in non-inoculated ones. Nitrogen, P, and magnesium leaf content was significantly higher in mycorrhizal plants compared with non-mycorrhizal plants grown with the same P level. These findings suggest that F. mosseae can stimulate plants growth, improving the nutritional quality of lettuce leaves even when grown with sub-optimal P concentration.

Mycorrhizae enhance drought tolerance of trifoliate orange by regulating circadian clock response patterns

Either arbuscular mycorrhizal fungus or circadian clock plays an important role in enhancing the tolerance of plants to soil drought, whereas it is not known whether the change of circadian rhythm is involved in mycorrhiza-enhanced drought tolerance in host plants. The purpose of this study was to investigate effects of an arbuscular mycorrhizal fungus Funneliformis mosseae on biomass production, root morphology, and expressions of circadian clock genes and drought-responsive genes in roots of trifoliate orange plants under drought stress conditions. After 8 weeks of soil drought, root mycorrhizal colonization rate and the length of soil mycelium significantly decreased, together with improved leaf, stem, and root biomass production and root morphology by mycorrhizal fungus. Expressions of six circadian clock genes (PtPRR7, PtCCA1, PtLHY, PtGI, PtPIF3, and PtSRR1) and three drought-responsive genes (PtMn-SOD, PtPOD, and PtCAT1) showed obvious circadian rhythm during the day. Under soil drought, F. mosseae induced the expression of PtPRR7, PtGI, and PtSRR1 at 17:00, PtPIF3 and PtSRR1 at 21:00, and PtPRR7, PtPIF3, and PtSRR1 at 1:00, whereas decreased the expression of PtLHY at all the tested time points. F. mosseae also up-regulated expressions of drought-responsive gene (PtFe-SOD, PtMn-SOD, PtCu/Zn-SOD, PtPOD, and PtLEA) at 17:00, 21:00 and 1:00 under drought conditions. Correlation analysis indicated the significant correlation between circadian clock gene expressions and drought-responsive gene expressions. These results conclude that mycorrhizal fungi regulate the circadian rhythm of trifoliate orange to respond to drought.

Combined effects of root-associated entomopathogenic and mycorrhizal fungi on the foliar pathogen Botrytis cinerea in tomato

Many fungi live intimately associated with plants and may benefit or harm the host plant. Improved knowledge of such interactions is needed for increasing plant health and crop productivity by implementation of fungal inoculants. Co-inoculations of different beneficial fungi offer the possibility to understand complex plant–microbe interactions that may be functionally complementary for improved plant production and protection. Here, we studied the individual and combined effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae with three isolates of entomopathogenic fungi (EPF), representing Metarhizium brunneum, M. robertsii and Beauveria bassiana, on protection against the foliar phytopathogen Botrytis cinerea and on plant growth. Seedlings of tomato (Solanum lycopersicum L. var. Moneymaker) were inoculated in the substrate with AMF or EPF alone and in dual combinations under greenhouse conditions. Inoculation with the different EPF isolates reduced lesion sizes of B. cinerea on inoculated tomato leaves, but only in the experimental repetition that showed highest level of disease severity. The AMF F. mosseae had no additional effect on B. cinerea lesion size in combinations with EPF. In the experimental repetition with least disease severity, the AMF treatment led to limited increase of B. cinerea lesion sizes. In general, F. mosseae caused an increase in plant biomass, and the co-inoculations of AMF and EPF did in some combinations increase plant growth. Below-ground interactions between AMF and EPF were observed, as the presence of AMF in the roots was associated with a decrease of EPF root colonization densities. However, AMF colonization rates were unaffected by EPF presence. The study indicated a functional complementarity between EPF and AMF by suppressing phytopathogens and increasing plant growth, respectively. However, it further revealed the challenge of obtaining consistent results of plant–microbe-phytopathogen interactions, which must be overcome for future implementation of beneficial fungi as inoculants in plant production.

Impact of the Arbuscular Mycorrhizal Fungus Funneliformis mosseae on the Physiological and Defence Responses of Canna indica to Copper Oxide Nanoparticles Stress.

Copper oxide nanoparticles (nano-CuO) are recognized as an emerging pollutant. Arbuscular mycorrhizal fungi (AMF) can mitigate the adverse impacts of various pollutants on host plants. However, AMF’s mechanism for alleviating nano-CuO phytotoxicity remains unclear. The goal of this study was to evaluate how AMF inoculations affect the physiological features of Canna indica seedlings exposed to nano-CuO stress. Compared with the non-AMF inoculated treatment, AMF inoculations noticeably improved plant biomass, mycorrhizal colonization, leaf chlorophyll contents, and the photosynthetic parameters of C. indica under nano-CuO treatments. Moreover, AMF inoculation was able to significantly mitigate nano-CuO stress by enhancing antioxidant enzyme activities and decreasing ROS levels in the leaves and roots of C. indica, thus increasing the expression of genes involved in the antioxidant response. In addition, AMF inoculation reduced the level of Cu in seedlings and was associated with an increased expression of Cu transport genes and metallothionein genes. Furthermore, AMF inoculations increased the expression levels of organic acid metabolism-associated genes while facilitating organic acid secretion, thus reducing the accumulation of Cu. The data demonstrate that AMF–plant symbiosis is a feasible biocontrol approach to remediate nano-CuO pollution.

Impact of Phosphatic Nutrition on Growth Parameters and Artemisinin Production in Artemisia annua Plants Inoculated or Not with Funneliformis mosseae.

Artemisia annua L. is a medicinal plant appreciated for the production of artemisinin, a molecule used for malaria treatment. However, the natural concentration of artemisinin in planta is low. Plant nutrition, in particular phosphorus, and arbuscular mycorrhizal (AM) fungi can affect both plant biomass and secondary metabolite production. In this work, A. annua plants were ino- culated or not with the AM fungus Funneliformis mosseae BEG12 and cultivated for 2 months in controlled conditions at three different phosphatic (P) concentrations (32, 96, and 288 µM). Plant growth parameters, leaf photosynthetic pigment concentrations, artemisinin production, and mineral uptake were evaluated. The different P levels significantly affected the plant shoot growth, AM fungal colonization, and mineral acquisition. High P levels negatively influenced mycorrhizal colonization. The artemisinin concentration was inversely correlated to the P level in the substrate. The fungus mainly affected root growth and nutrient uptake and significantly lowered leaf artemisinin concentration. In conclusion, P nutrition can influence plant biomass production and the lowest phosphate level led to the highest artemisinin concentration, irrespective of the plant mineral uptake. Plant responses to AM fungi can be modulated by cost–benefit ratios of the mutualistic exchange between the partners and soil nutrient availability.

Single and coinoculation of Serendipita herbamans with arbuscular mycorrhizal fungi reduces Fusarium wilt in tomato and slows disease progression in the long-term

Soil-borne plant pathogens are difficult to control, and the application of individual biocontrol agents is often limited. This limitation calls for an integrated approach, and the combination of microorganisms might result in more effective control than individual inoculations. In our study, we investigated the effects of single inoculation and coinoculation of the endophytic fungus Serendipita herbamans and the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae in protecting tomato plants from the soil-borne pathogen Fusarium oxysporum f. sp. lycopersici (Fol). We conducted two independent greenhouse experiments in which plants were grown for either eight or sixteen weeks. Plants cultivated for eight weeks received Fol chlamydospores on the day of transplanting (simultaneous Fol inoculation), whereas plants grown for sixteen weeks obtained Fol either simultaneously or two weeks later (delayed Fol inoculation). S. herbamans was inoculated via root dipping for 24 h, while AMF was applied on the day of transplanting. The disease incidence was reduced by 67% when S. herbamans was inoculated individually or by 53% when it was coinoculated with AMF in the eight-week cultivation period. Even until sixteen weeks, a reduction in disease incidence by 25% and 42%, respectively, was evident. Delayed inoculation with Fol did not affect the disease incidence, but the disease severity was increased in plants treated solely with AMF. With regard to the other parameters, the AMF partner colonized the roots readily, enhanced the phosphorus status and compensated for the growth of tomato plants challenged with Fol. In combination with the bioprotective effect mediated by the endophyte, AMF strengthened the morphological and nutritional features, providing tomato plants a long-term protective advantage when challenged with Fol.

Stimulation of Hyphal Ramification and Sporulation in Funneliformis mosseae by Root Extracts Is Host Phosphorous Status-Dependent.

A simulation of the environment inhabited by arbuscular mycorrhizal (AM) fungi could provide clues as to how to cultivate these obligate biotrophs axenically. Host intraradical and rhizospheric environments, root extracts and exudates in particular, would be crucial for AM fungi to complete their life cycles. In this study, we analyzed and compared the effects of root exudates (RE) and root extracts (RET) of white clover (Trifolium repens) on the asymbiotic growth of the AM fungus Funneliformis mosseae in vitro, and furtherly analyzed the chemical components of different RET with the LC-MS/MS technique in order to establish an asymbiotic cultivation system for this important and hardly domesticated AM fungus. RET is superior to RE in stimulating spore germination, hyphal elongation and branching, and secondary spore formation (p < 0.05). RET-induced effects were dependent on phosphate supplement levels, and the RET obtained following the treatment with low levels of phosphorus significantly promoted hyphal growth and sporulation (p < 0.05). A few newly formed secondary spores showed limited colonization of white clover roots. The low phosphorus-induced effects could be ascribed to the metabolic adjustment (mainly lipids and organic acids) of white clover roots under low phosphate conditions. Our findings demonstrate that the low phosphate-induced RET boosts the asymbiotic growth of AM fungus, and thus offers an alternative way to fulfill the life cycle of AM fungi asymbiotically.

Cadmium transfer between maize and soybean plants via common mycorrhizal networks

More than 80% terrestrial plants establish mutualistic symbiosis with soil-borne arbuscular mycorrhizal fungi (AMF). These fungi not only significantly improve plant nutrient acquisition and stress resistance, but also mitigate heavy metal phytotoxicity, Furthermore, the extraradical mycorrhizal mycelia can form common mycorrhizal networks (CMNs) that link roots of multiple plants in a community. Here we show that the networks mediate migration of heavy metal cadmium (Cd) from maize (Zea mays L.) to soybean (Glycine max (Linn.) Merr.) plants. CMNs between maize and soybean plants were established after inoculation of maize plants with AMF Funneliformis mosseae. Application of CdCl2 in maize plants led to 64.4% increase in the shoots and 48.2% increase in the roots in Cd content in CMNs-connected soybean plants compared to the control without Cd treatment in maize. Meanwhile, although the CMNs-connected soybean plants did not directly receive Cd supply, they upregulated transcriptional levels of Cd transport-related genes HATPase and RSTK 2.13- and 5.96-fold, respectively, induced activities of POD by 44.8% in the leaves, and increased MDA by 146.2% in the roots. Furthermore, Cd addition inhibited maize growth but mycorrhizal colonization improved plant performance in presence of Cd stress. This finding demonstrates that mycorrhizal networks mediate the transfer of Cd between plants of different species, suggesting a potential to use CMNs as a conduit to transfer toxic heavy metals from main food crops to heavy metal hyperaccumulators via intercropping.

Effect of an arbuscular mycorrhizal fungus on maize growth and cadmium migration in a sand column

The ecological role of arbuscular mycorrhizal fungi (AMF) on altering cadmium (Cd) migration in polluted soil is still unresolved. The present experiment aimed to clarify whether AMF can reduce Cd loss due to leaching at different Cd concentrations (0, 5, 10, and 15 mg L−1) with maize as a host plant cultured in a sand column. The effects of the arbuscular mycorrhizal fungus Funneliformis mosseae on the root morphology, exudate content, and Cd uptake by maize and Cd loss due to leaching were investigated. The AMF altered the root morphology and exudate content of the maize, resulting in increases in the root length, volume, surface area, tips and branch number and in the contents of soluble sugars, proteins, and amino acids in the root exudates, and the AMF increased maize biomass and Cd uptake by 22.0–31.0%. Moreover, the AMF significantly increased the contents of total and easily extractable glomalin-related soil protein (GRSP), increased Cd adsorption by sand particles and decreased the Cd concentration in the solution at a depth of 20 cm, resulting in a 67.5–97.2% decrease in the Cd loss due to leaching from the sand column. Furthermore, the root exudate content was very significantly positively correlated with Cd adsorption by the sand particles. Root length was significantly positively correlated with Cd uptake by the maize roots, but the average root diameter was very significantly negatively correlated with Cd uptake by maize. Thus, the AMF altered Cd migration by increasing the contents of GRSP and exudates and root morphology, which contributed to reducing the Cd concentration in the solution and Cd loss due to leaching from the sand column. Taken together, these results indicated that AMF serve an ecological function in reducing Cd loss due to leaching from polluted soil.

Mycorrhiza and Iron Tailings Synergistically Enhance Maize Resistance to Arsenic on Medium Arsenic-Polluted Soils Through Increasing Phosphorus and Iron Uptake.

Agricultural arsenic (As, CAS. No. 7440-38-2) over the issue of pollution has been related to people's livelihood, security and moderate use of As contaminated soil is an important aspect of contaminated soil remediation. In this potted plant experiment, synergistic effects of arbuscular mycorrhizal fungi (AMF) Funneliformis mosseae and iron (Fe, CAS. No. 7439-89-6) oxides on plant growth and phosphorus (P, CAS. No. 7723-14-0), As and Fe uptake by maize (Zea mays L.) were studied on simulating medium As-polluted soils in greenhouse. Different amounts (0, 5, 10, 20, 40gkg- 1) of iron tailings (IT) were added. The results showed that IT20 and IT40 addition significantly increased mycorrhizal infection rate, plant biomass, root length and P, Fe uptake under FM treatment; IT40 addition decreased As concentration in roots. In addition, FM inoculation increased biomass, root length and P uptake by shoots, but decreased Fe and As concentration in shoots. Therefore, the combined FM inoculation and IT40 addition promoted maize growth and decreased As concentration in shoots by decreasing As absorption efficiency, increasing P and Fe uptake and P/As ratio.

Mycorrhizal symbiosis primes the accumulation of antiherbivore compounds and enhances herbivore mortality in tomato.

Plant association with arbuscular mycorrhizal fungi (AMF) can increase their ability to overcome multiple stresses, but their impact on plant interactions with herbivorous insects is controversial. Here we show higher mortality of the leaf-chewer Spodoptera exigua when fed on tomato plants colonized by the AMF Funneliformis mosseae, evidencing mycorrhiza-induced resistance. In search of the underlying mechanisms, an untargeted metabolomic analysis through ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS) was performed. The results showed that mycorrhizal symbiosis had a very limited impact on the leaf metabolome in the absence of stress, but significantly modulated the response to herbivory in the damaged area. A cluster of over accumulated metabolites was identified in those leaflets damaged by S. exigua feeding in mycorrhizal plants, while unwounded distal leaflets responded similar to those from non-mycorrhizal plants. These primed-compounds were mostly related to alkaloids, fatty acid derivatives and phenylpropanoid-polyamine conjugates. The deleterious effect on larval survival of some of these compounds, including the alkaloid physostigmine, the fatty acid derivatives 4-oxododecanedioic acid and azelaic acid, was confirmed. Thus, our results evidence the impact of AMF on metabolic reprograming upon herbivory that leads to a primed accumulation of defensive compounds.

Interactive Effects of Mycorrhizae, Soil Phosphorus, and Light on Growth and Induction and Priming of Defense in Plantago lanceolata.

Increasing demands to reduce fertilizer and pesticide input in agriculture has triggered interest in arbuscular mycorrhizal fungi (AMF) that can enhance plant growth and confer mycorrhiza-induced resistance (MIR). MIR can be based on a variety of mechanisms, including induction of defense compounds, and sensitization of the plant’s immune system (priming) for enhanced defense against later arriving pests or pathogens signaled through jasmonic acid (JA). However, growth and resistance benefits of AMF highly depend on environmental conditions. Low soil P and non-limiting light conditions are expected to enhance MIR, as these conditions favor AMF colonization and because of observed positive cross-talk between the plant’s phosphate starvation response (PSR) and JA-dependent immunity. We therefore tested growth and resistance benefits of the AMF Funneliformis mosseae in Plantago lanceolata plants grown under different levels of soil P and light intensity. Resistance benefits were assessed in bioassays with the leaf chewing herbivore Mamestra brassicae. Half of the plants were induced by jasmonic acid prior to the bioassays to specifically test whether AMF primed plants for JA-signaled defense under different abiotic conditions. AMF reduced biomass production but contrary to prediction, this reduction was not strongest under conditions considered least optimal for carbon-for-nutrient trade (low light, high soil P). JA application induced resistance to M. brassicae, but its extent was independent of soil P and light conditions. Strikingly, in younger plants, JA-induced resistance was annulled by AMF under high resource conditions (high soil P, ample light), indicating that AMF did not prime but repressed JA-induced defense responses. In older plants, low soil P and light enhanced susceptibility to M. brassicae due to enhanced leaf nitrogen levels and reduced leaf levels of the defense metabolite catalpol. By contrast, in younger plants, low soil P enhanced resistance. Our results highlight that defense priming by AMF is not ubiquitous and calls for studies revealing the causes of the increasingly observed repression of JA-mediated defense by AMF. Our study further shows that in our system abiotic factors are significant modulators of defense responses, but more strongly so by directly modulating leaf quality than by modulating the effects of beneficial microbes on resistance.

Influence of Microbial Consortium in the Production of China Aster and Gaillardia Seedlings

Abstract China aster and gaillardia are flowering plants with high economic importance in floriculture. In the present investigation, response of China aster and gaillardia seedlings to inoculation with the arbuscular mycorrhizal fungus Funneliformis mosseae + the plant growth-promoting rhizobacterium Bacillus sonorensis was studied by growing in multipots (pro trays). The germination percentage and plant growth parameters: length of shoots, roots and whole seedlings, stem diameter, biovolume index, plant strength, vigor index, dry weight and nutrient uptake, were analyzed 60 days after sowing. The microbial parameters, mycorrhizal root colonization and spore count, and the population of B. sonorensis in the substrate were also determined. The results brought out that growth of inoculated seedlings was significantly improved as compared to uninoculated seedlings. Based on the plant growth and microbial parameters studied, it was concluded that inoculating the substrate in pro trays with the microbial consortium results in producing vigorously growing seedlings.

Effects of beneficial endophytic fungal inoculants on plant growth and nutrient absorption of trifoliate orange seedlings

Citrus plants heavily depend on soil arbuscular mycorrhizal fungi (AMF), while the application of AMF in citrus is limited because of no propagation in vitro. The present work tried to apply a culturable (in vitro) endophytic fungus Piriformospora indica into trifoliate orange (Poncirus trifoliata) and to compare the role of P. indica in plant growth and nutrient acquisition especially phosphorus (P), relative to an arbuscular mycorrhizal fungus Funneliformis mosseae. After 20 weeks, roots of trifoliate orange could be colonized by P. indica, and both P. indica and F. mosseae existed in roots together. Root fungal colonization and soil easily extractable, difficultly extractable, and total glomalin-related protein concentrations were higher under single F. mosseae inoculation than under single P. indica and dual inoculation of F. mosseae and P. indica. Single or dual microbial inoculant collectively improved plant growth including plant height, leaf number, and leaf, stem, and root biomass, compared with non-inoculation. In addition, single fungal treatment raised the content of root N, P, and Mg, and dual inoculation increased only Mg and B contents. The improvement of P by single microbial inoculant was associated with the fungi-accelerated soil phosphatase activity and the fungi-induced root phosphate transporter genes (PT3, PT5, and PT6) expression levels. The positive effects on growth and nutrients were more significant under single F. mosseae than under single P. indica and dual inoculations. It concluded that P. indica has the stimulated roles in plant growth and P acquisition of trifoliate orange, and thus has more applied potentiality in citriculture than AMF as a biofertilizer.