Arbuscular Mycorrhizal Fungi Association Research Articles

Arbuscular mycorrhizal fungi association and root rot disease in mungbean (<i>Vigna radiata</i>) growing areas of Haryana

The study was carried out during rainy (kharif) seasons of 2021 and 2022 at Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana to provide a comprehensive understanding of how the presence and activity of arbuscular mycorrhizal (AM) fungi may influence the development of root rot in mungbean (Vigna radiata L.) crops in different mungbean-growing areas of Haryana. Root colonization by AM fungi in Hisar, Bhiwani, Mahendragarh, and Charkhi Dadri districts of Haryana ranged from 16.45 to 24.07%, 7.71 to 16.73%, 7.02 to 21.43% and 7.59 to 22.28%, respectively. This variability underscores the diverse interactions between mungbean plants and AM fungi in these distinct geographical regions, reflecting the influence of environmental factors and local soil conditions on mycorrhizal associations. Sporocarp numbers in these districts ranged from 76.5 to 131.5, 37 to 102, 54 to 119.5 and 65.5 to 118 per 100 g of soil, respectively. These findings emphasize the dynamic nature of AM fungal populations and their potential impact on the overall soil health and plant-microbe interactions in mungbean cultivation. Similarly, root rot incidence in these districts varied from 6.59 to 11.62%, 7.48 to 11.29%, 7.05 to 11.43% and 5.88 to 11.76%, while root rot intensity ranged from 2.77 to 4.82%, 2.70 to 4.61%, 2.06 to 4.61% and 2.43 to 4.85% in Hisar, Bhiwani, Mahendragarh, and Charkhi Dadri districts, respectively. This variability in root rot incidence and intensity highlights the susceptibility of mungbean crops to this detrimental disease and emphasizes the importance of region-specific strategies for disease management.

Arbuscular mycorrhizal fungi enhance yield and photosynthesis of switchgrass (Panicum virgatum L.) under extreme drought and alters the biomass composition of the host plant

Drought is one of the major environmental stressors that affect plant growth and performance. To cope with such stresses most plants utilize belowground association with arbuscular mycorrhizal fungi (AMF). The AMF provide plants with nutrients and water in exchange for carbon fixed by their hosts. Very little is known about how this mutualism affect plant growth and physiology under extreme drought and in the context of lignocellulosic crops such as switchgrass. We investigated how AMF association affects switchgrass growth and physiology when under extreme drought (droughted to just above the permanent wilting point) in a factorial greenhouse experiment. This extreme drought was imposed at a level slightly above the permanent wilting point of switchgrass, which we measured. Although drought significantly depressed mycorrhizal colonization by ∼37%, the aboveground biomass in mycorrhizal plants increased by more than 3-fold under drought as compared to non-mycorrhizal plants. The increase in biomass was accompanied by a significant increase in net CO2 assimilation, stomatal conductance, and an enhanced intrinsic Water Use Efficiency. Drought increased aboveground lignin, starch, and sucrose by 9%, 151% and 16% respectively whereas AMF decreased total starch by 43%. Drought also decreased total cellulose by 10% as compared to the no-drought plants. AMF and drought also altered the composition of matrix polysaccharides. In this study, we found evidence that AMF are mostly beneficial to switchgrass under extreme drought and both the factors affect switchgrass biomass quality.

Contrasting mycorrhizal growth responses in native and invasive woody species are associated with distinct root trait syndromes

Abstract Invasive plant species often express resource‐acquisitive leaf traits that support rapid growth, but associated fine root traits and the role of microbial mutualists in invader whole‐plant functioning remain poorly understood. We performed an experiment of 12 phylogenetically grouped native and non‐native, invasive woody species, grown with or without a common inoculum of arbuscular mycorrhizal fungi (AMF) across two nutrient levels. We measured 10 fine root traits associated with nutrient uptake and suitability of AMF colonization. The presence of AMF increased the growth rate of all species, but native species were significantly more dependent on AMF than invaders. Furthermore, invaders expressed a distinct syndrome of first‐order root traits, including longer, thinner roots of high specific root length, greater branching intensity and lower tissue density, which are traits associated with rapid nutrient uptake and low AMF association. This syndrome was independent of phylogeny, AMF inoculation and soil fertility. An acquisitive fine root trait syndrome for invaders supports high photosynthetic and growth rates, linking above‐ and below‐ground functioning. The occurrence of this syndrome across phylogenetic groups indicates that lineages of woody invaders typically associated with arbuscular mycorrhizas may be generally less dependent on AMF than native species. Read the free Plain Language Summary for this article on the Journal blog.

Effects of Carbon Amendments, Tillage and Cover Cropping on Arbuscular Mycorrhizal Fungi Association and Root Architecture in Corn and Cotton Crop Sequence

A field experiment was conducted to study the effects of carbon amendments, tillage, and cover cropping on arbuscular mycorrhizal fungi (AMF) association and root architecture at Farm Services at Texas A&M University. Three levels of carbon amendments at the rate of 500 kg C ha−1 (biochar, composted biosolid, and control (no carbon amendment)), two levels of tillage (conventional disking (CT) and no tillage (NT)), and two levels of cover crop (a mixture of oat, mustard, and pea (CC) and no cover crop (NCC)) were arranged in a split-split plot design with four replications. Over a two-year crop sequence of corn followed by cotton, AMF colonization of roots was 4.43% greater in biochar-treated soil than in the control treatment. Colonization in cotton was 5.17% and 6.09% greater under NT and CC treatments, respectively, compared to CT and NCC. Carbon amendments did not alter corn root length but did alter root angle at 20–30 cm. Carbon amendments did not affect root angle under CC. However, tillage did affect CC root length and angle. Root length and root angle were found to differ among the cover crop species. The results imply that farmers may combine certain practices to optimize and harness the benefits of AMF.

Nutrition vs association: plant defenses are altered by arbuscular mycorrhizal fungi association not by nutritional provisioning alone

BackgroundWhile it is known that arbuscular mycorrhizal fungi (AMF) can improve nutrient acquisition and herbivore resistance in crops, the mechanisms by which AMF influence plant defense remain unknown. Plants respond to herbivory with a cascade of gene expression and phytochemical biosynthesis. Given that the production of defensive phytochemicals requires nutrients, a commonly invoked hypothesis is that the improvement to plant defense when grown with AMF is simply due to an increased availability of nutrients. An alternative hypothesis is that the AMF effect on herbivory is due to changes in plant defense gene expression that are not simply due to nutrient availability. In this study, we tested whether changes in plant defenses are regulated by nutritional provisioning alone or the response of plant to AMF associations. Maize plants grown with or without AMF and with one of three fertilizer treatments (standard, 2 × nitrogen, or 2 × phosphorous) were infested with fall armyworm (Spodoptera frugiperda; FAW) for 72 h. We measured general plant characteristics (e.g. height, number of leaves), relative gene expression (rtPCR) of three defensive genes (lox3, mpi, and pr5), total plant N and P nutrient content, and change in FAW mass per plant.ResultsWe found that AMF drove the defense response of maize by increasing the expression of mpi and pr5. Furthermore, while AMF increased the total phosphorous content of maize it had no impact on maize nitrogen. Fertilization alone did not alter upregulation of any of the 3 induced defense genes tested, suggesting the mechanism through which AMF upregulate defenses is not solely via increased N or P plant nutrition.ConclusionThis work supports that maize defense may be optimized by AMF associations alone, reducing the need for artificial inputs when managing FAW.

Nitrogen addition altered the plant-arbuscular mycorrhizal fungi network through reducing redundant interactions in an alpine meadow

Interactions between plants and arbuscular mycorrhizal fungi (AMF) are pivotal in linking belowground soil nutrients with plant-derived carbon in terrestrial ecosystems. However, little is known about the effect of variation in soil nutrients (i.e., nitrogen enrichment) on the structure and phylogenetic characteristics of the mutualistic network. With a 7-year nitrogen addition experiment in an alpine meadow, we built networks for 20 plant species that all occur along the nitrogen addition gradient and their AMF by sequencing 314 root samples. We investigated the responses of association degree (i.e., the number of links of plant or AMF species), network connectance, nestedness, modularity and specialization to different concentrations of nitrogen addition. Phylogenetic signal was calculated to evaluate if the phylogenetically closely related plant species or AMF taxa share similar symbiosis partners. We found that nitrogen addition significantly reduced the plant and AMF association degree, with the generalist (with high association degree) and abundant AMF taxa in nature significantly decreasing association degree and relative abundance (sequencing reads). Therefore, the network connectance and nestedness decreased, but modularity increased with nitrogen addition. Phylogenetic signal of plants (i.e., phylogenetically related plants had similar AMF partners) was always stronger than that of AMF, but the signal vanished with nitrogen addition. The shifted soil properties after nitrogen addition, especially pH, played an important role in regulating the network structures. Our results discover a non-random plant-AMF network shaped by both phylogeny and soil environments in an alpine meadow, and suggest that global nitrogen addition may result in a non-random loss or switch of plant-fungal associations, changes in network structures and phylogenetic relationships, which may have ramification to nutrient exchange and symbiotic performance.

New Record of Arbuscular Mycorrhizal Fungi (AMF) Association with Kebar Grass (<i>Biophytum petersianum</i> Klotzsch.) in the Grassland Area of Kebar, Tambrauw Regency, West Papua, Indonesia

Arbuscular mycorrhizal fungi (AMF) are an important form of symbiosis between fungi and plants in an ecosystem. One of the medicinal plants used by the people in West Papua is kebar grass (Biophytum petersianum Klotzsch.). This study aims to determine the AMF association in the rhizosphere of B. petersianum in grasslands. Survey method was used in this study. The presence of AMF was observed by examining root colonization and spore diversity. The results showed that the percentage of AMF colonization in roots was between 46.7–90.0% with an average of 71.66%. Meanwhile, the number of spores found in the plant rhizosphere averaged 119.8 spores per 10 grams of soil sample. There were 18 species of AMF dominated by the genus Glomus (7 species), Acaulospora (3 species), while the genus Claroideoglomus, Entrophospora, Gigaspora, and Scutellospora were dominated each with 2 species. This finding is the first record on the presence of AMF on B. petersianum in West Papua.

Cotton waste‐derived biochar and compost improve early growth and AMF association in cotton

Improving the sustainability of cotton (Gossypium hirusutum L.) production can be achieved by returning organic matter and nutrients to degraded soils. Amendment with biochar prepared from locally available feedstocks has been suggested as a pathway to sustainability. A greenhouse study collaboratively conducted by Malian and Texas A&M investigators evaluated the effect of biochar prepared from two feedstocks readily available in northwestern Africa: cotton field residue and rice (Oryza sativa L.) hulls, on cotton plants grown to 6 wk. A composted municipal biosolid was included for comparison with the more carbon (C)-stable biochars. Four soils of contrasting properties were included in the study. Plant growth response variables were all affected by soil type (p < .0001). Shoot height was improved by biochars and composts in all soils. Root mass was improved by amendment only in the soil with the greatest clay content. Nitrogen (N) uptake was significantly depressed, and phosphorus (P) uptake was increased under biochar and compost amendment in the most coarsely textured soil. No effect on N and P uptake was observed in the soil with the greatest clay content. Ridge regression analysis showed that arbuscular mycorrhizal fungi (AMF) root colonization was positively related to the P content of the amendments (1.41*Pamend), negatively related to soil P (–0.49*Psoil) and positively related to both soil pH (2.15*pH) and clay content (1.130*clay%). Results indicate that degraded soils may be restored through amendment with biochar created from locally available feedstock to improve sustainability of cotton production. Soil properties will determine the degree of benefit.

Mycorrhizal fungi-mediated uptake of tree-derived nitrogen by maize in smallholder farms

Trees within farmers’ fields can enhance systems’ longer-term productivity, for example, via nutrient amelioration, which is indispensable to attain sustainable agroecosystems. While arbuscular mycorrhizal fungi (AMF) are known to improve plant access to soil nutrients, the potential of AMF to mediate nutrient uptake of tree-derived nitrogen (N) by crops from beyond the crops’ rooting zones is unclear. We hypothesized that AMF quantitatively contribute to the crop uptake of tree-derived N. We set up root- and AMF-exclusion and control plots around faidherbia trees (Faidherbia albida) and used the 15N natural abundance technique to determine the magnitude of AMF-mediated uptake of tree-derived N by maize from beyond its rooting zone in smallholder fields. We further tested whether AMF-mediated N uptake decreases with distance from tree. We show that within one cropping season, maize obtained approximately 35 kg ha–1 biologically fixed N from faidherbia. One-third of tree-derived N in maize leaves was attributed to AMF-mediated N uptake from beyond the maize rooting zone and two-thirds to N from tree leaf litter, regardless of distance from tree. As hypothesized, maize grown close (1 m) to faidherbia obtained significantly more tree-derived N than that at farther distances (4 and 5 m). Thus, the faidherbia–AMF association can enhance agroecosystem functioning.

Arbuscular mycorrhizal colonization rate of an exotic plant, Galinsoga quadriradiata, in mountain ranges changes with altitude.

Arbuscular mycorrhizal fungi (AMF) are suggested to be important for invasions by many exotic plants. However, it is not yet known how associations between AMF and invasive plant populations change in mountains ranges and how changed associations affect further expansion of different populations in new habitats. We conducted a field survey to detect AMF colonization rate of the invasive Galinsoga quadriradiata along an elevational gradient ranging from 223 to 1947masl in the Qinling and Bashan Mountains, China. Additionally, a greenhouse experiment was conducted to compare plant growth performance among five elevational populations. In the field, total plant mass and seed production, as well as root AMF colonization rate, significantly decreased with elevation. When populations were grown in a novel soil environment in the greenhouse, the high-altitude populations achieved higher seed and total mass at lower AMF colonization rate than the low-altitude populations. Moreover, high AMF association was related to high intraspecific competition within low-altitude populations and limited seed production. Our results revealed that the associations between AMF and G. quadriradiata decrease with altitude in mountain ranges, and this may indicate that differentiation of association between AMF and elevational populations occurs during range expansion of G. quadriradiata. The results of the greenhouse experiment suggest that the high-altitude populations are more aggressive than the low-altitude populations in a non-stressful environment.

Metabarcoding of Soil Fungal Communities Associated with Alpine Field-Grown Saffron (Crocus sativus L.) Inoculated with AM Fungi.

Soil fungi strongly influence ecosystem structure and functioning, playing a key role in many ecological services as decomposers, plant mutualists and pathogens. Arbuscular mycorrhizal fungi (AMF) establish mutualistic symbiotic associations with plant roots and act as biofertilizers by enhancing plant nutrients and water uptake. Information about the AMF association with Crocus sativus L. (saffron) and their impact on crop performances and spice quality has been increasing in recent years. Instead, there is still little data on the biodiversity of soil microbial communities associated with this crop in the Alpine environments. The aims of this study were to investigate the fungal communities of two Alpine experimental sites cultivated with saffron, and to rank the relative impact of two AMF inocula, applied to soil as single species (R = Rhizophagus intraradices, C. Walker & A. Schüßler) or a mixture of two species (M = R. intraradices and Funneliformis mosseae, C. Walker & A. Schüßler), on the resident fungal communities which might be influenced in their diversity and composition. We used Illumina MiSeq metabarcoding on nuclear ribosomal ITS2 region to characterize the fungal communities associated to Crocus sativus cultivation in two fields, located in the municipalities of Saint Christophe (SC) and Morgex (MG), (Aosta Valley, Italy), treated or not with AMF inocula and sampled for two consecutive years (Y1; Y2). Data analyses consistently indicated that Basidiomycota were particularly abundant in both sites and sampling years (Y1 and Y2). Significant differences in the distribution of fungal taxa assemblages at phylum and class levels between the two sites were also found. The main compositional differences consisted in significant abundance changes of OTUs belonging to Dothideomycetes and Leotiomycetes (Ascomycota), Agaricomycetes and Tremellomycetes (Basidiomycota), Mortierellomycetes and Mucoromycetes. Further differences concerned OTUs, of other classes, significantly represented only in the first or second year of sampling. Concerning Glomeromycota, the most represented genus was Claroideoglomus always detected in both sites and years. Other AMF genera such as Funneliformis, Septoglomus and Microdominikia, were retrieved only in MG site. Results highlighted that neither sites nor inoculation significantly impacted Alpine saffron-field fungal communities; instead, the year of sampling had the most appreciable influence on the resident communities.

Changes in Arbuscular Mycorrhizal Fungal Community Structure in Soybean Rhizosphere Soil Assessed at Different Growth Stages of Soybean

Arbuscular mycorrhizal fungi (AMF) is the most common type of AMF association colonizing the rhizosphere of soybean [Glycine max (L.) Merrill] plants. However, the extent of AMF formation, AMF species composition and diversity at different stages of soybean penology have not yet studied. The current study was aimed to determine AMF species community composition, species distribution and its affinity in the rhizosphere soil of soybean at the different growth stages of soybean. Root and rhizosphere soil samples were collected at different growth stage pre-sowing, nodulation, maturation and harvesting stage from soybean (cultivar JS-335) and were analysed for AMF root colonization, spore diversity, species richness, and relative occurrence of AMF species. The AMF species principally contributing to the crop growth stage was also examined through principal component analysis (PCA). The extent of root length colonized by native AMF (mainly formed arbuscules) in soybean roots was higher at maturation (79.76%) and lowest (25.33%) at nodulation stages, whereas the spore density showed opposite trend. Irrespective of growth stages, a total of 40 AMF morphotypes were observed from which species, viz. Glomus aggregatum, Rhizophagus fasciculatum, Glomus coronatum, Glomus etunicatum, Glomus sp (76.92%), were found to be the most frequent and abundant species followed by species of Acaulospora (12.82%) and Gigaspora (10.25%). The Shannon–Weaver index was the range of 3.22, whereas Simpson’s index was 0.95, which indicates the higher diversity of AMF at pre-sowing. The PCA explains the maximum contribution of all AMF species observed at pre-sowing followed by harvesting concludes that AMF diversity and colonization pattern are greatly affected with the soybean phenological growth stages where rhizosphere was found to be mainly dominated by Glomus morphotypes than the Acaulospora and Gigaspora; hence these can be selected for further exploitation in soybean.

Cacao – Arbuscular Mycorrhizal Fungi Association: A Review on Its Increased Potential in Improving the Ecology of Cacao Plantations in the Philippines

Cacao (Theobroma cacao) is both an economically and ecologically important crop worldwide especially in the Philippines, a tropical country suitable for its growth and cultivation. The association of this crop with arbuscular mycorrhizal fungi (AMF) is an understudied field but the benefits reported from this symbiosis highlights their irreplaceable role in enhancing growth conditions by facilitating the uptake of phosphorus, increasing yield through increased plant health and productivity, and in several ecological aspects such as soil biological dynamics and ecological processes that are carried out in cacao plant community. This paper proposed the different areas of improving cacao ecology that need to gain attention in the Philippines to augment the measures being undertaken to boost the country’s cacao plantations. This includes more research on areas of soil physicochemical properties, AMF genetic and functional diversity in cacao communities, and resistance to diseases of AMF-associated cacao trees. The ecology of the AMF-cacao association is an essential part of developing effective AMF inocula for the ultimate purpose of increasing the yield of cacao. Appropriate application of AMF could increase the overall yield of the country’s cacao plantations and can be translated to improving food security and many other economic gains.

The effects of arbuscular mycorrhizal inoculation to growth and survivability of micropropagated Eucalyptus pellita and Acacia crassicarpa in nursery

Inoculation of arbuscular mycorrhizal (AM) fungi into micropropagated Eucalyptus pellita and Acacia crassicarpa, that may have poor root structures, was conducted. The study aimed to investigate the effects of Acaulospora sp., Acaulospora tuberculata, Entrophospora sp., Gigaspora sp., and two different isolates of Glomus maculosum inoculations on the growth parameters of 21-days old plantlets of Eucalyptus pellita and Acacia crassicarpa. After 120 days of acclimatization in the nursery, E. pellita seems to be more responsive to mycorrhizal inoculation than A. crassicarpa. The survival rate of E. pellita was almost three times of the control. Although there was no significant difference between treatments, inoculation of Glomus maculosum RD.1.5.1 and Acaulospora sp. GB.10.A2 showed the highest impact on plant height (54-56 cm), stem diameter (4.3-4.4 mm), and root dry-weight (2.03-2.05 gr) of E. pellita; and Entrophospora sp. RB.10.3.1 on plant height, stem diameter, and root dry-weight of A. crassicarpa (41.46 cm, 2.96 mm, and 1.34 gr, respectively). This study also revealed that the benefits of AM fungi association were not always related to the level of root colonization.

AM fungi mediated bioaccumulation of hexavalent chromium in Brachiaria mutica-a mycorrhizal phytoremediation approach

The experiment was designed to evaluate the roles of Rhizophagus irregularis on chlorophyll fluorescence and chromium bioaccumulation in a grass species (Brachiaria mutica) by supplementing Cr+6 at different concentrations. Arbuscular Mycorrhizal Fungi (AMF) association facilitated lessening of chromium level in contaminated soil and enhanced chromium bioavailability in Brachiaria mutica. The mycorrhizal inoculated increased the chlorophyll (0.925 mg/g), carotenoid (0.127 mg/g), protein (2.883 mg/g), proline (0.889 mg/g) contents and activities of antioxidant enzymes like catalase, ascorbate peroxidase and glutathione peroxidase. The mycorrhizal inoculated plants also showed enhanced overall photosynthetic performance (PIϕ = 2.473) and enhanced PS–II to PS–I electron transport as evident from yield parameter (0.712) and TR0/RC (2.419) for 60 mg/kg Cr+6 treatment. The observations suggest that AMF association could defend the plants from chromium stress by elevating the number of antioxidants in plants. Rhizophagus irregularis was found to maintain a successful symbiotic relationship with Brachiaria mutica in chromium contaminated soil. The observations recommended that Rhizophagus irregularis in association with Brachiaria mutica would be an innovative approach for decontamination of Cr+6.

Genetic and phenotypic associations between root architecture, arbuscular mycorrhizal fungi colonisation and low phosphate tolerance in strawberry (Fragaria \xd7 ananassa)

BackgroundPhosphate is an essential plant macronutrient required to achieve maximum crop yield. Roots are able to uptake soil phosphate from the immediate root area, thus creating a nutrient depletion zone. Many plants are able to exploit phosphate from beyond this root nutrient depletion zone through symbiotic association with Arbuscular Mycorrhizal Fungi (AMF). Here we characterise the relationship between root architecture, AMF association and low phosphate tolerance in strawberries. The contrasting root architecture in the parental strawberry cultivars ‘Redgauntlet’ and ‘Hapil’ was studied through a mapping population of 168 progeny. Low phosphate tolerance and AMF association was quantified for each genotype to allow assessment of the phenotypic and genotypic relationships between traits.ResultsA “phosphate scavenging” root phenotype where individuals exhibit a high proportion of surface lateral roots was associated with a reduction in root system size across genotypes. A genetic correlation between “root system size” traits was observed with a network of pleiotropic QTL found to represent five “root system size” traits. By contrast, average root diameter and the distribution of roots appeared to be under two discrete methods of genetic control. A total of 18 QTL were associated with plant traits, 4 of which were associated with solidity that explained 46% of the observed variation. Investigations into the relationship between AMF association and root architecture found that a higher root density was associated with greater AMF colonisation across genotypes. However, no phenotypic correlation or genotypic association was found between low phosphate tolerance and the propensity for AMF association, nor root architectural traits when plants are grown under optimal nutrient conditions.ConclusionsUnderstanding the genetic relationships underpinning phosphate capture can inform the breeding of strawberry varieties with better nutrient use efficiency. Solid root systems were associated with greater AMF colonisation. However, low P-tolerance was not phenotypically or genotypically associated with root architecture traits in strawberry plants. Furthermore, a trade-off was observed between root system size and root architecture type, highlighting the energetic costs associated with a “phosphate scavenging” root architecture.

Dissimilar Responses of Ancient Grapevines Recovered in Navarra (Spain) to Arbuscular Mycorrhizal Symbiosis in Terms of Berry Quality

The exploitation of genetic diversity within agricultural plants, including grapevine, is suggested as a valuable tool to cope with the negative impacts of climate change on yield and crop quality. In some winegrowing regions of Europe, there is a renewed interest in knowing the grapevine genetic resources available, focusing on the prospection, recovery, and study of ancient cultivars typical of every zone. Grapevines are naturally associated with arbuscular mycorrhizal fungi (AMF), which provide some benefits to the host plant, although such effects depending on many factors, including variety. Therefore, the aim of this research was to characterize the potential fruit quality of eight old grapevine varieties recovered in Navarre (northeastern of the Iberian Peninsula), associated or not with AMF. The study was carried out on fruit-bearing cuttings grown under controlled conditions (greenhouse). Overall, AMF inoculation reduced bunch and berry mass, as well as phenolic content in fruits. In some varieties, AMF association improved some berry traits by increasing the concentrations of soluble solids and anthocyanins; in others, berry colour, total phenolic and anthocyanin content were diminished in AMF-inoculated plants. The results, therefore, suggest that intraspecific diversity of old grapevines could include different abilities to respond to arbuscular mycorrhizal symbiosis.

Root flavonoids are related to enhanced AMF colonization of an invasive tree.

Arbuscular mycorrhizal fungi (AMF) are important mutualistic microbes in soil, which have capacity to form mutualistic associations with most land plants. Arbuscular mycorrhizal fungi play an important role in plant invasions and their interactions with invasive plants have received increasing attention. However, the chemical mechanisms underlying the interactions of AMF and invasive plants are still poorly understood. In this study we aim to test whether root secondary chemicals are related to enhanced AMF colonization and rapid growth in an invasive tree. We conducted a common garden experiment in China with Chinese tallow tree (Triadica sebifera) to examine the relationships among AMF colonization and secondary metabolites in roots of plants from introduced (USA) and native (China) populations. We found that AMF colonization rate was higher in introduced populations compared to native populations. Roots of plants from introduced populations had lower levels of phenolics and tannins, but higher levels of flavonoids than those of plants from native populations. Flavonoids were positively correlated with AMF colonization, and this relationship was especially strong for introduced populations. Besides, AMF colonization was positively correlated with plant biomass suggesting that higher root flavonoids and AMF colonization may impact plant performance. This suggests that higher root flavonoids in plants from introduced populations may promote AMF spore germination and/or attract hyphae to their roots, which may subsequently increase plant growth. Overall, our results support a scenario in which invasive plants enhance their AMF association and invasion success via genetic changes in their root flavonoid metabolism. These findings advance our understanding of the mechanisms underlying plant invasion success and the evolutionary interactions between plants and AMF. Understanding such mechanisms of invasive plant success is critical for predicting and managing plant invasions in addition to providing important insights into the chemical mechanism of AMF–plant interactions.

Influences of plant interspecific competition and arbuscular mycorrhizal fungi on nitrogen form preference of an invasive plant

Invasive plant species are often able to alter soils in a way that benefits their own fitness over that of native species. While interspecific competitions may drive species to acquire different forms of nitrogen (N) to avoid intensive competition, plant-mycorrhizal interactions can also influence plant nutrient acquisition. Yet, it is unclear whether a variation in N acquisition by an invasive species is driven by interspecific resource partitioning due to competition with native species or by its symbiosis with arbuscular mycorrhizal (AM) fungi. We conducted a pot experiment to examine the effects of competition and fungicide on the uptake of different N forms by Flaveria bidentis, an invasive plant having symbiotic relationships with AM fungi, and two coexisting native species, mycotrophic Bidens maximowicziana and non-mycotrophic Amaranthus retroflexus (referred to by genus hereafter), by growing them either in two-species mixtures or in monocultures. We found that the growth of Flaveria was suppressed by its association with AM fungi regardless of the presence of competing native species, but the degree of suppression was related to the native species with which Flaveria competed. When growing in monocultures, all three species showed a strong preference for NO3−-N over NH4+-N and glycine-N regardless of mycorrhizal status. However, under competition conditions, Flaveria increased 15N recovery in any form of N available (in particular NH4+-15N), depending on neighboring plant identity and AM fungi association, whereas Amaranthus specially tended to decrease NH4+-15N uptake when competing with Flaveria, suggesting a niche complementarity in the utilization of N between two species. Our findings suggested that AM fungi may have the potential to limit the invasion of Flaveria, in the short term, and that interspecific competition plays an important role in partitioning soil N acquisition between plant species.

Salinity tolerance and sodium localization in mycorrhizal strawberry plants

ABSTRACT Salinity stress alleviation through arbuscular mycorrhizal fungi (AMF) application and sodium (Na) localization in strawberry plants were investigated. A greenhouse experiment in a completely randomized design with three replications revealed AMF (Gigaspora margarita) association alleviated salinity stress (200 mM NaCl). AMF inoculated plants had greater dry weight, maintained chlorophyll content, and decreased leaves browning compared to the control under salinity stress. The Na+ concentration and Na+/K+ ratio were found lower in the following organs, young and old leaflets and petioles, main roots and lateral roots of mycorrhizal plants than the control. The scanning electron microscope and energy dispersive x-ray spectroscopy (SEM-EDX) analysis of Na in old petiole and main root tissues revealed, excess Na localized in the vascular bundle margin of old petioles and main roots of both the control and mycorrhizal plants. So, suppression of Na absorption through roots might be the mechanism of salt stress alleviation in mycorrhizal plants than to the control Na localization. The higher cellulose and lignin contents in the cell wall of mycorrhizal roots act as the apoplastic barrier which might be suppressing Na influx.