Native Arbuscular Mycorrhizal Fungi Research Articles

Development of a taxon-discriminating molecular marker to trace and quantify a mycorrhizal inoculum in roots and soils of agroecosystems.

Crop inoculation with Glomus cubense isolate (INCAM-4, DAOM-241198) promotes yield in banana, cassava, forages, and others. Yield improvements range from 20 to 80% depending on crops, nutrient supply, and edaphoclimatic conditions. However, it is difficult to connect yield effects with G. cubense abundance in roots due to the lack of an adequate methodology to trace this taxon in the field. It is necessary to establish an accurate evaluation framework of its contribution to root colonization separated from native arbuscular mycorrhizal fungi (AMF). A taxon-discriminating primer set was designed based on the ITS nrDNA marker and two molecular approaches were optimized and validated (endpoint PCR and quantitative real-time PCR) to trace and quantify the G. cubense isolate in root and soil samples under greenhouse and environmental conditions. The detection limit and specificity assays were performed by both approaches. Different 18 AMF taxa were used for endpoint PCR specificity assay, showing that primers specifically amplified the INCAM-4 isolate yielding a 370bp-PCR product. In the greenhouse, Urochloa brizantha plants inoculated with three isolates (Rhizophagus irregularis, R. clarus, and G. cubense) and environmental root and soil samples were successfully traced and quantified by qPCR. The AMF root colonization reached 41-70% and the spore number 4-128 per g of soil. This study demonstrates for the first time the feasibility to trace and quantify the G. cubense isolate using a taxon-discriminating ITS marker in roots and soils. The validated approaches reveal their potential to be used for the quality control of other mycorrhizal inoculants and their relative quantification in agroecosystems.

Symbiosis of isoetid plant species with arbuscular mycorrhizal fungi under aquatic versus terrestrial conditions.

Arbuscular mycorrhizal fungi (AMF) colonize the roots of numerous aquatic and wetland plants, but the establishment and functioning of mycorrhizal symbiosis in submerged habitats have received only little attention. Three pot experiments were conducted to study the interaction of isoetid plants with native AMF. In the first experiment, arbuscular mycorrhizal (AM) symbiosis did not establish in roots of Isoëtes echinospora and I. lacustris, while Littorella uniflora roots were highly colonized. Shoot and root biomass of L. uniflora were, however, not affected by AMF inoculation, and only one of nine AMF isolates significantly increased shoot P concentration. In the second experiment, we compared colonization by three Glomus tetrastratosum isolates of different cultivation history and origin (aquatic versus terrestrial) and their effects on L. uniflora growth and phosphorus nutrition under submerged versus terrestrial conditions. The submerged cultivation considerably slowed, but did not inhibit mycorrhizal root colonization, regardless of isolate identity. Inoculation with any AMF isolate improved plant growth and P uptake under terrestrial, but not submerged conditions. In the final experiment, we compared the communities of AMF established in two cultivation regimes of trap cultures with lake sediments, either submerged on L. uniflora or terrestrial on Zea mays. After 2-year cultivation, we did not detect a significant effect of cultivation regime on AMF community composition. In summary, although submerged conditions do not preclude the development of functional AM symbiosis, the contribution of these symbiotic fungi to the fitness of their hosts seems to be considerably less than under terrestrial conditions.

Levantamento de fungos micorrízicos arbusculares em associação a espécie vegetal Manihot esculenta Crantz

Cassava production in the state of Alagoas is mostly carried out by small rural producers who adopt little management technology, and who routinely do not replace nutrients due to the high cost of chemical inputs. In this agricultural production model, the knowledge and use of strategies that include natural biological processes in the soil, mainly of the microbiota present in this environment, such as arbuscular mycorrhizal fungi (AMF), can be presented as an alternative for biofertilization, since, Arbuscular mycorrhizae are symbiotic associations established between the roots of most plants and non-pathogenic fungi in the soil that have beneficial effects, which can improve plant growth and productivity and soil structure. Thus, the aim of this study was to evaluate the density of glomerospores and the native AMF genera present in the rhizosphere of cassava, Sergipana variety, as well as to determine mycorrhizal colonization in the evaluated culture. Soil collections were made in the cassava rhizosphere, at 90, 180, 270 and 360 days after planting (DAP). The average number of glomerospores in each treatment was evaluated at 90, 180, 270 and 360 DAP, and the main AMF genera present, and an evaluation of mycorrhizal colonization of the roots at 360 DAP was performed. Cassava cultivation showed an increase of approximately 174.46% at 360 DAP, showing a significant difference in the density of AMFs when compared to the 90 DAP period. The genera Diversispora sp, Entrophospora sp, Acaulospora sp, Scutellospora sp, and Racocetra sp. in cultivation, and a positive result for mycorrhizal colonization, with a 61% rate of colonization of the roots of the evaluated species.

Effect of bacterial biofertilizers, native arbuscular mycorrhizal fungi and soil amendments on soil and grain phosphorus availability of flooded rice in dry zone, Sri Lank

Rice is considered as the most important food crop in Sri Lanka and most of the Asian countries. Over the past three decades, rice farmers have become increasingly dependent on synthetic chemical phosphorous fertilizers, mainly triple super phosphate (TSP) as a source of phosphorous (P). However, dramatically increasing costs, serious environmental and health issues attached to chemical fertilizers, forced researchers to develop supplementary or alternate sources of P for rice. Hence, this study was done to evaluate the potential use of biofertilizers and natural soil amendments as alternatives to chemical P fertilizers in rice (Oryza sativa L.) farming in the dry zone of Sri Lanka. A field trial was carried out at Ranpathwela in Anuradhapura, North Central Province, Sri Lanka, during the Yala season in 2016. The experiment was designed as follows: CON: control; AMF: AMF inoculants (2 Mg ha-1); RAMF: ERP (153.3 kg ha-1) with the AMF inoculants (2 Mg ha-1); MC: mixed microbial culture (5 kg ha-1); RMC: ERP (153.3 kg ha-1) with a mixed microbial culture [consortium of Azospirillum sp., Pseudomonas sp. and Bacillus sp. (5 L ha-1)]; BC: biochar (6 Mg ha-1); CP: standard compost (10 Mg ha-1) and IF: inorganic synthetic fertilizer (125 N kg ha-1, 62.5 P2O5 kg ha-1 and 50 K2O kg ha-1). Three indigenous and two improved rice varieties were used. The experiment comprised of 24 plots and three replicates. Soil, roots and grains of rice were analyzed for phosphorus. Some other elements were shown to have an effect on plant available soil P such as aluminum and iron, were also estimated. It was revealed that significant differences (p<0.05) in variety, treatment and V x T interaction was observed in plant available soil phosphorus. The highest mean of available soil P was observed in TRSP2 x AMF (14.64 ± 0.12 mg kg-1) followed by TRSP3 x MC (8.87 ± 0.001 mg kg-1) interactions. The multifunctional microbial consortium in amended soil, including Azospirillum sp., Pseudomonas sp. Bacillus sp. and arbuscular mycorrhizal fungi, were capable of potentially increasing soil phosphorus. Furthermore, the addition of rock phosphate did not always make a difference in soil P availability for rice farming systems.

Bacillus subtilis CP4, isolated from native soil in combination with arbuscular mycorrhizal fungi promotes biofortification, yield and metabolite production in wheat under field conditions.

The aim of this study was to identify the best combination of plant growth promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) for biofortification and enhancing yield in wheat as well as improve soil health under field conditions. Another aim was to get insights into metabolite dynamics in plants treated with PGPB and AMF. Different combinations of PGPB and AMF that gave good results in greenhouse study were used in a field study. The combined application of Bacillus subtilis CP4 (native PGPB) and AMF gave the best results with a significant increase in biomass, macronutrient and micronutrient content in wheat grains and improvement in yield-related parameters relative to the untreated control. PGPB and AMF treatment increased antioxidant enzymes and compounds and decreased the level of an oxidation marker. Metabolite profiling performed using Gas Chromatography-Mass Spectrometry (GC-MS) showed significant upregulation of specific organic acids, amino acids, sugars and sugar alcohols in plants treated with CP4 and AMF. The altered pathways due to CP4 and AMF inoculation mainly belong to carbohydrate and amino acid metabolism. A positive correlation was observed between some organic acids, sugars and amino acids with wheat growth and yield parameters. The activities of soil enzymes increased significantly with the best results shown by native PGPB and AMF combination. A native bacterial isolate Bacillus subtilis CP4 in combination with AMF showed exceptional ability for biofortification and yield enhancement under field conditions. The upregulation of a number of metabolites showed correlation plant growth promotion and nutrients. The combined application of native B. subtilis CP4 and AMF could offer a more sustainable approach for the development of a biofertilizer to enhance wheat nutrient content and production and soil health thereby advancing agriculture.

Physiological and Biochemical Behaviors of Date Palm Vitroplants Treated with Microbial Consortia and Compost in Response to Salt Stress

The main challenge of the agricultural sector is to develop new ecological technologies that increase the yields and the tolerance of crops to abiotic constraints, especially in arid areas. The objective of this study was to test the potential roles of biofertilizers, namely, arbuscular mycorrhizal fungi (AMF), a native AMF consortium (AMF1) and an exotic AMF strain (AMF2); plant growth-promoting rhizobacteria (PGPR); and compost (comp), applied separately or in combination, in improving the tolerance of date palm vitroplants to salt stress. Plants were grown under non-stressed (0 mM NaCl) or stressed conditions (120 and 240 mM NaCl). Salt stress negatively affected growth and physiological parameters. However, biofertilizers used alone or in combination increased these traits in either the presence or absence of salinity. The two tripartite combinations PGPR+AMF1+Comp and PGPR+AMF2+Comp efficiently increased plant height compared to the controls, with respective enhancements of 47% and 48% under non-stressed conditions (0 mM), 44% and 43% under 120 mM NaCl and 42% and 41% under 240 mM NaCl. Moreover, under 240 mM NaCl level, the PGPR, AMF1+Comp and PGPR+AMF1+Comp treatments improved the shoot dry weight by 128%, 122% and 113% respectively compared to the stressed control plants submitted to 240 mM NaCl. The tripartite combinations PGPR+AMF1/AMF2+Comp improved salt stress tolerance of plants by increasing plant growth, accumulation of osmotic adjustment compounds and antioxidant enzyme activity compared to control plants and the other treatments.

Potential of Native Arbuscular Mycorrhizal Fungi, Rhizobia, and/or Green Compost as Alfalfa (Medicago sativa) Enhancers under Salinity.

Salinity is one of the devastating abiotic stresses that cause reductions in agricultural production. The increased salinization affects alfalfa growth, metabolism, and rhizobium capacity for symbiotic N2 fixation negatively. This study was undertaken to investigate the efficiency of green compost (C; made from green waste), arbuscular mycorrhizal fungi (M; field-sourced native consortium), and/or rhizobium (R; a salt-tolerant rhizobium strain) individually or in combination as an effective strategy to improve alfalfa productivity under non-saline and high-saline (120 mM NaCl) conditions. In addition, we aimed to understand the agro-physiological and metabolic basis as well as glomalin content in the soil of biofertilizers-induced salt tolerance in alfalfa. Here, we show that mycorrhizal infection was enhanced after MR inoculation, while C application decreased it significantly. Salinity reduced growth, physiological functioning, and protein concentration, but the antioxidant system has been activated. Application of the selected biofertilizers, especially C alone or combined with M and/or R improved alfalfa tolerance. The tri-combination CMR mitigated the negative effects of high salinity by stimulating plant growth, roots and nodules dry matters, mineral uptake (P, N, and K), antioxidant system, synthesis of compatible solutes, and soil glomalin content, sustaining photosynthesis-related performance and decreasing Na+ and Cl− accumulation, lipid peroxidation, H2O2 content, and electrolyte leakage.

Growth, heavy metal uptake, and photosynthesis in 'Paulsen 1103' (Vitis berlandieri x rupestris) grapevine rootstocks inoculated with arbuscular mycorrhizal fungi from vineyard soils with high copper contents

Soils in old vineyards in southern Brazil have high copper accumulation due to fungicide applications over the years, which can affect physiology and growth of young grapevine plants. Arbuscular mycorrhizal fungi (AMF) alleviate toxic effects of metals and increase photosynthesis and plant growth. We evaluated whether inoculation with Rhizophagus clarus (Rh) from a mining area or with a trap-culture-enriched AMF community (Tc) isolated from a high-copper vineyard soil, improved growth and photosynthesis in grapevine rootstocks planted in young ( 60 years) vineyards soils of Vale da Uva Goethe, SC, Brazil. Mycorrhizal colonization was higher in grapevines installed in young vineyard soil than those planted in old vineyard soil. Plants grew more in the old vineyard soil than in the soil from a young vineyard, and that was related to plant nutrient concentration in the soil. In both soils, Tc-inoculated grapevines had higher photosynthetic activity, while those inoculated with R. clarus had higher carbon assimilation. In conclusion, grapevines showed a positive response to AMF inoculation in different soil conditions, and the native AMF community from high copper soils are promising for inoculation of grapevines.

Impacts of Organic and Conventional Management on the Nutritional Level of Vegetables

The nutrient concentration of fruits and vegetables in the U.S.A. has declined in the past 50–70 years. Crop management practices utilizing on-farm inputs are thought to increase crop nutritional quality, but few studies have evaluated this under long-term side-by-side trials. An experiment was conducted from 2004 to 2005 at Rodale Institute’s long-term Farming Systems Trial to investigate the nutritional quality of vegetables under organic manure (MNR) and conventional (CNV) farming systems, with or without arbuscular mycorrhizal fungi (AMF) treatment. AMF reduced the vitamin C content in carrots in both systems in 2004, but the reduction was 87% in CNV and 28% in MNR. AMF also reduced antioxidants in carrots in both CNV and MNR. This trend was likely due to the suppression of native AMF colonization by the non-native AMF inoculum used. Between 2004 and 2005, MNR increased the vitamin C in green peppers by 50% while CNV decreased the vitamin C in red peppers by 48%. Tomatoes under MNR had a 40% greater vitamin C content compared to CNV in 2005. The vegetable yield declined between 2004 and 2005, except for tomato, where the yield increased by 51% and 44% under CNV and MNR, respectively. In general, MNR tended to increase the nutrient concentration of vegetables compared with CNV, while the AMF effects were inconclusive.

Biofertilizers as Strategies to Improve Photosynthetic Apparatus, Growth, and Drought Stress Tolerance in the Date Palm.

Rainfall regimes are expected to shift on a regional scale as the water cycle intensifies in a warmer climate, resulting in greater extremes in dry versus wet conditions. Such changes are having a strong impact on the agro-physiological functioning of plants that scale up to influence interactions between plants and microorganisms and hence ecosystems. In (semi)-arid ecosystems, the date palm (Phoenix dactylifera L.) -an irreplaceable tree- plays important socio-economic roles. In the current study, we implemeted an adapted management program to improve date palm development and its tolerance to water deficit by using single or multiple combinations of exotic and native arbuscular mycorrhizal fungi (AMF1 and AMF2 respectively), and/or selected consortia of plant growth-promoting rhizobacteria (PGPR: B1 and B2), and/or composts from grasses and green waste (C1 and C2, respectively). We analyzed the potential for physiological functioning (photosynthesis, water status, osmolytes, mineral nutrition) to evolve in response to drought since this will be a key indicator of plant resilience in future environments. As result, under water deficit, the selected biofertilizers enhanced plant growth, leaf water potential, and electrical conductivity parameters. Further, the dual-inoculation of AMF/PGPR amended with composts alone or in combination boosted the biomass under water deficit conditions to a greater extent than in non-inoculated and/or non-amended plants. Both single and dual biofertilizers improved physiological parameters by elevating stomatal conductance, photosynthetic pigments (chlorophyll and carotenoids content), and photosynthetic efficiency. The dual inoculation and compost significantly enhanced, especially under drought stress, the concentrations of sugar and protein content, and antioxidant enzymes (polyphenoloxidase and peroxidase) activities as a defense strategy as compared with controls. Under water stress, we demonstrated that phosphorus was improved in the inoculated and amended plants alone or in combination in leaves (AMF2: 807%, AMF1+B2: 657%, AMF2+C1+B2: 500%, AMF2+C2: 478%, AMF1: 423%) and soil (AMF2: 397%, AMF1+B2: 322%, AMF2+C1+B2: 303%, AMF1: 190%, C1: 188%) in comparison with controls under severe water stress conditions. We summarize the extent to which the dual and multiple combinations of microorganisms can overcome challenges related to drought by enhancing plant physiological responses.

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.

English

Mycorrhizae are symbiotic associations between fungi and host plants, which confer several advantages, including good mineral nutrition. Arbuscular mycorrhizal fungi (AMF) then present an effective alternative in order to develop a sustainable agriculture that is less dependent on mineral fertilizers. The objective of this study was to assess the impact of organic fertilizers based on native arbuscular mycorrhizal fungi on increasing maize productivity and improving soil health in North Benin. For this study, three mycorrhizal fungi strains (Glomeraceae sp., Acaulosporaceae sp. and Diversisporaceae sp.) were used with or without mineral fertilizers. The corn variety 2000 SYN EE-W was used. The experimental design is a randomized complete block of nine treatments with three replicates. After 65 days, the endomycorrhizal infection was evaluated. The results showed that mycorhizal fungi had a positive impact on the different plant growth parameters (height, leaf area, and yield). At the height level, Acaulospora + ½ dose of N15P15K15 recommended + urea produced good results compared to the control, an increase of 24.9%. The same observations were made for leaf area and yield, an increase of 70.4 and 39.04%, respectively. However, the results show that the rate of endomycorrhizal infection is high with Diversisporaceae sp. + 50% of recommended N15P15K15 + urea followed by Glomeraceae sp. + 50% of recommended N15P15K15 + urea and Acaulosporeacea sp.+ 50% of recommended N15P15K15 + urea. In terms of spore number, the treatment Glomeraceae sp. gave the best result. Key words: Mycorrhizal fungi, organic fertilizer, corn, Benin.

Genotypic variation in response and dependency of Cajanus cajan (L.) Millsp., on arbuscular mycorrhizal fungi in a tropical Alfisol

Plant genotypes significantly differ in their growth characteristics and dependence on arbuscular mycorrhizal (AM) fungi for maximum growth and productivity at a given soil fertility level. Therefore, we examined the mycorrhizal dependency and response of seven pigeon pea (Cajanus cajan) genotypes (BRG–1, BRG–2, BRG–3, BRG–4, BRG–5, TRG–7 and Vamban–3) on native AM fungi. Plants of pigeon pea genotypes were grown in the presence and absence of native AM fungi for 45 days. At harvest, plant growth characteristics, root architecture, nodulation, AM fungal colonization, and plant nutrients were measured and nutrient uptake, nutrient use efficiencies and mycorrhizal dependency were calculated. The plant growth, root architecture, nodulation, and nutrient characteristics varied significantly among pigeon pea genotypes and were positively (except nutrient usage) influenced by AM fungi. The mycorrhizal dependency significantly varied among pigeon pea genotypes and ranged from 30.54% to 65.02%. The genotypes BRG–3 and BRG–4 were highly mycorrhizal dependent and accumulated maximum biomass under mycorrhizal conditions. Our results show that AM fungi in addition to improving plant growth and nutrient uptake can also modify the proportional allocation of biomass to shoot and root, root architecture, and nutrient use among pigeon pea genotypes.

Morpho-physiology and Pht1 gene expressions in native maize plants with AM fungi and phosphorus

Maize is a crop important worldwide, but its production is limited to phosphorus availability in soil. Plants form a symbiotic association to improve their nutrition with arbuscular mycorrhizal fungi (AMF), which increase to absorption phosphorus (P) and the expression of transporters of the family Pht1. Few studies have focused on native maize plants and AMF. Thus, the objective of this study was to determine the morpho-physiological response and expression of phosphate Pht1 transporters in two native maize plants inoculated with Claroideoglomus etunicatum and P concentrations. The height, leaf area, dry biomass, CO2 assimilation rate, stomatal conductance, transpiration rate, intercellular CO2, water potential, greenness index, total chlorophyll, and ZEAma; Pht1;3 and ZEAma; Pht1;6 transporter expressions in maize plants under P (0.01 and 1 mM) concentrations were evaluated. The results showed that each native maize plant had a differential response in morpho-physiology and transporter expressions when they were inoculated with AMF and P. The response of maize plant was related with its genotype and phenotype plus environmental factor that influenced the AMF-host interaction, mycorrhizal colonization and soil nutrient absorption.

Impact of chemical properties of soil on spore density, colonization, and distribution of native arbuscular mycorrhizal fungi associated with Capsicum annuum L.

Impact of chemical properties of soil on spore density, colonization, and distribution of native arbuscular mycorrhizal fungi associated with Capsicum annuum L.

Hongos micorrízicos nativos como promotores de crecimiento en plantas de guayaba (Psidium guajava L.)

En esta investigación se evaluaron diferentes consorcios micorrízicos arbusculares nativos, en el crecimiento de plantas de guayaba (Psidium guajava L.). Se estableció un experimento totalmente al azar con siete inóculos de hongos micorrízicos arbusculares (HMA) denominados: Las Campesinas (LC), Carlos Rojas (CR), Paso Ancho (PA), El limón (EL), Cerro del Metate (CM) (consorcios nativos), una cepa comercial (INIFAP®), y un control sin HMA, en una mezcla de arena-suelo esterilizada y bajo condiciones de invernadero. Semillas de guayaba fueron germinadas en arena esterilizada y posteriormente, las plántulas fueron trasplantadas a bolsa de vivero con una mezcla de arena-suelo esterilizada, donde fueron inoculadas con los diferentes tratamientos de HMA. Después de 125 días, se realizó un muestreo destructivo donde se registró, la altura de planta, el diámetro del tallo, el área foliar, la materia fresca y seca de cada órgano. Así como, la relación materia seca de la parte aérea/materia seca de la raíz, el índice de robustez y el índice de Dickson, como variables de calidad de planta. Cómo variables microbiológicas se determinó, la micorrización radicular y la cantidad de esporas en el sustrato. Los resultados mostraron un efecto diferencial en el crecimiento en las plantas de guayaba, cuando se inocularon con algún consorcio nativo de HMA. Entre los diferentes consorcios evaluados, EL promovió el mejor desarrollo y calidad de planta, y fue donde se alcanzó la mayor colonización y producción de esporas en el sustrato. La mayor tasa de mortalidad se registró en las plantas sin HMA, o inoculadas con el inóculo INIFAP. Los porcentajes de colonización fueron superiores al 60%, excepto en el consorcio CM. Por lo anterior se puede mencionar que, el uso de HMA podría ser una práctica recomendable para el cultivo sustentable de guayabas en invernadero.

The influence of mycorrhization on the growth of Zea mays L. and the sclerification of foliar tissues susceptible to chewing insect attacks

The interrelationships between arbuscular mycorrhizal fungi (AMF) and plants have been the subject of numerous studies; however, whether these mutualistic associations are capable of producing structural defenses in plants for pest control remains to be determined. The present study evaluated the influence of AMF on the sclerification of foliar tissues of corn and related it to insect attack. Corn plants were grown in 5.5-L pots containing soil/sand (sterile, fertilized, pH corrected) in a greenhouse. Mycorrhized plants received propagules of native AMF; non-mycorrhized plants received soil filtrate of AMF-free soil. Some of the plants of both treatments were collected at 40 days post-emergence, while others were collected at 50 days and 60 days. Height and dry mass of the aerial part and dry mass of radicular part were evaluated. The median region of leaves of the fourth (basal) and seventh (cartridge) leaf nodes was transversally sectioned, and the sections stained, mounted in semi-permanent medium and analyzed under a microscope to measure variables related to tissue organization and sclerification. Mycorrhized plants had greater height and aerial-part dry mass. Mycorrhization influenced nine of the 15 anatomical variables analyzed with increased lignified tissue in at least one of the growth stages. It can be concluded that colonization of corn roots by AMF promotes sclerification of leaf tissues and, thus, may interfere indirectly with the plant–pest relationship by altering the quality of phytomass available for insects.

Contrasting effects of commercial and native arbuscular mycorrhizal fungal inoculants on plant biomass allocation, nutrients, and phenolics

Societal Impact StatementAs the global population increases, the need to feed more people must be met while simultaneously conserving the long‐term sustainability of our agroecosystems. There is mounting interest and discussion around the application of arbuscular mycorrhizal fungal (AMF) inoculants to enhance crop growth, nutrient uptake, and pest resistance. However, the effects of AMF inoculation are variable and context dependent. This study found that a multi‐species AMF inoculant had a stronger effect on plant biomass allocation and chemistry than a single AMF species inoculant, however, neither of these had a stronger effect than re‐inoculating plants with a field‐sourced native AMF community.

Abiotic and biotic context dependency of perennial crop yield.

Perennial crops in agricultural systems can increase sustainability and the magnitude of ecosystem services, but yield may depend upon biotic context, including soil mutualists, pathogens and cropping diversity. These biotic factors themselves may interact with abiotic factors such as drought. We tested whether perennial crop yield depended on soil microbes, water availability and crop diversity by testing monocultures and mixtures of three perennial crop species: a novel perennial grain (intermediate wheatgrass—Thinopyrum intermedium-- that produces the perennial grain Kernza®), a potential perennial oilseed crop (Silphium intregrifolium), and alfalfa (Medicago sativa). Perennial crop performance depended upon both water regime and the presence of living soil, most likely the arbuscular mycorrhizal (AM) fungi in the whole soil inoculum from a long term perennial monoculture and from an undisturbed native remnant prairie. Specifically, both Silphium and alfalfa strongly benefited from AM fungi. The presence of native prairie AM fungi had a greater benefit to Silphium in dry pots and alfalfa in wet pots than AM fungi present in the perennial monoculture soil. Kernza did not benefit from AM fungi. Crop mixtures that included Kernza overyielded, but overyielding depended upon inoculation. Specifically, mixtures with Kernza overyielded most strongly in sterile soil as Kernza compensated for poor growth of Silphium and alfalfa. This study identifies the importance of soil biota and the context dependence of benefits of native microbes and the overyielding of mixtures in perennial crops.

Plant Performance and Metabolomic Profile of Loquat in Response to Mycorrhizal Inoculation, Armillaria mellea and Their Interaction

A greenhouse experiment was established with loquat plants to investigate the role of arbuscular mycorrhizal fungi (AMF) in the control of the white root rot fungus Armillaria mellea and to determine the changes produced in the plant metabolome. Plants inoculated with two AMF, Rhizoglomus irregulare and a native AMF isolate from loquat soils, were infected with Armillaria. Although mycorrhization failed to control the Armillaria root infection, the increased growth of infected plants following inoculation with the native mycorrhizal isolate suggests an initial tolerance towards Armillaria. Overall, metabolomics allowed highlighting the molecular basis of the improved plant growth in the presence of Armillaria following AMF colonization. In this regard, a wide and diverse metabolic response was involved in the initial tolerance to the pathogen. The AMF-mediated elicitation altered the hormone balance and modulated the production of reactive oxygen species (mainly via the reduction of chlorophyll intermediates), possibly interfering with the reactive oxygen species (ROS) signaling cascade. A complex modulation of fucose, ADP-glucose and UDP-glucose, as well as the down-accumulation of lipids and fatty acids, were observed in Armillaria-infected plants following AMF colonization. Nonetheless, secondary metabolites directly involved in plant defense, such as DIMBOA and conjugated isoflavone phytoalexins, were also involved in the AMF-mediated plant response to infection.