Arbuscular Mycorrhizal Fungi Isolates Research Articles

Inoculation with arbuscular mycorrhizal fungi has a more significant positive impact on the growth of open-pollinated heirloom varieties of carrots than on hybrid cultivars under organic management conditions

To meet the high demand for organic produce, farmers must select crop cultivars that perform well under the low-input conditions of organic production systems. Most cultivars grown on organic farms are genotypes selected through conventional breeding programs, which may impact responsiveness to microbial symbionts. The use of biological inputs such as mycorrhizal inoculants offers the promise of improving yield, quality, and stress-responsiveness of crops, but evidence of efficacy in the field remains elusive. Moreover, interspecific and intraspecific variability may impact the ability of mycorrhizal inoculants to provide benefits. This work evaluated four cultivars (two heirlooms and two hybrids) of carrots and their propensities to benefit from inoculation with isolates of arbuscular mycorrhizal fungi in organic field conditions with and without late-season water restriction. Inoculants included geographically-distinct isolates from four species (Funneliformis mosseae, Rhizophagus clarus, Rhizophagus intraradices, and Septoglomus deserticola). Heirloom cultivars demonstrated a higher propensity to benefit compared to hybrid cultivars from inoculation with arbuscular mycorrhizal fungi. We observed benefits and costs with respect to yield associated with inoculation within four experiments over twoditions. Breeding histories of plant genotypes likely contribute to their mycorrhizal responsiveness.

Sensitivity to AMF species is greater in late-successional than early-successional native or nonnative grassland plants.

Sensitivity of plant species to individual arbuscular mycorrhizal (AM) fungal species is of primary importance to understanding the role of AM fungal diversity and composition in plant ecology. Currently, we do not have a predictive framework for understanding which plant species are sensitive to different AM fungal species. In two greenhouse studies, we tested for differences in plant sensitivity to different AM fungal species and mycorrhizal responsiveness across 17 grassland plant species of North America that varied in successional stage, native status, and plant family by growing plants with different AM fungal treatments including eight single AM fungal isolates, diverse mixtures of AM fungi, and non‐inoculated controls. We found that late successional grassland plant species were highly responsive to AM fungi and exhibited stronger sensitivity in their response to individual AM fungal taxa compared to nonnative or early successional native grassland plant species. We confirmed these results using a meta‐analysis that included 13 experiments, 37 plant species, and 40 fungal isolates (from nine publications and two greenhouse experiments presented herein). Mycorrhizal responsiveness and sensitivity of response (i.e., variation in plant biomass response to different AM fungal taxa) did not differ by the source of fungal inocula (i.e., local or not local) or plant family. Sensitivity of plant response to AM fungal species was consistently correlated with the average mycorrhizal response of that plant species. This study identifies that AM fungal identity is more important to the growth of late successional plant species than early successional or nonnative plant species, thereby predicting that AM fungal composition will be more important to plant community dynamics in late successional communities than in early successional or invaded plant communities.

Experimental evaluation of the potential of arbuscular mycorrhiza to modify nutrient leaching in three arable soils located on one slope

Arbuscular mycorrhizal fungi (AMF) were previously shown to decrease nutrient losses by leaching from grassland soils, but no information is available for arable soils. Therefore, the objective of our study was to evaluate the potential of arbuscular mycorrhiza to modify nitrogen and phosphorus cycling including nitrate and phosphate leaching in arable soils. To this end, we established a pot experiment with maize (Zea mays L.) grown in three soils sampled along a sloping field and differing in phosphorus availability and texture. The plants were either inoculated with the native microbial community of the soil, with a pot-cultured AMF isolate, or grown without AMF.Phosphate and nitrate leaching varied among the three soils according to phosphorus availability and plant growth, both being highest in the soil with the highest sand and phosphorus contents. Nitrate leaching was significantly increased by the soils' native microbial communities, which induced higher net nitrification rates as compared to the treatments inoculated with the pot-cultured microbial communities. Mycorrhiza was formed in all three soils after AMF inoculation, with low to intermediate root colonization levels. However, it had no effect on plant growth or nutrient uptake in any of the three soils, which was consistent with a significant nitrogen deficiency of the maize plants. The absence of mycorrhizal effects on nitrate and phosphate leaching is discussed within this context, and the potential of arbuscular mycorrhiza to reduce nutrient leaching from arable soils is concluded low.

Changes in some characters of soybean leaves inoculated with mycorrhiza in salinity stress

Increasing soybean production can be done by expanding the planting area on suboptimal land such as saline soils. Leaves which are an important part of plants where the photosynthesis takes place also experience disturbances due to salinity stress. Efforts can be made to overcome salinity stress, among others by planting salinity tolerant soybean genotypes and mycorrhiza inoculation. This study aims to analyse changes in leaf morphology characters in two soybean genotypes inoculated with mycorrhiza in salinity stress. The study used split-plot design with the main plot of soybean genotype (Grobogan variety and Grobogan soybeans selected for salinity tolerance) and subplots arbuscular mycorrhizal fungi isolates (control, Glomus sp. 1, Glomus sp. 2, Glomus sp. 3, Glomus sp. 4, Glomus sp. 5, and isolates the mixture of all isolates) in the experimental field of Paluh Merbau Village Deli Serdang with 1.5 m above sea level and salinity level of 5-6 dS/m in February-May 2013. The results showed the number of leaves, leaf area, chlorophyll a, and chlorophyll b were significantly affected by the interaction of soybean genotype and mycorrhizal inoculation. While the treatment of soybean genotypes and mycorrhizal inoculation showed significant differences in the number of stomata and thickness of cuticles.

Diversity and distribution of arbuscular mycorrhizal fungi in pome and stone Fruit orchards of North Western Himalayan State of Jammu & Kashmir

A study was conducted to assess the diversity and distribution of arbuscular mycorrhizal fungi (AMF) in pome (apple and pear) and stone (cherry) fruit orchards in North Western Himalayan Kashmir. A total of 222 AMF isolates were isolated from the rhizosphere of apple, pear and cherry plants from the four districts of Kashmir valley viz., Srinagar, Ganderbal, Baramulla and Shopian. The maximum number of AMF isolates were found in district Baramulla (60) followed by Ganderbal (57), Srinagar (53) and Shopian (52) with Simpson’s species diversity index of 0.58. Twenty-nine AMF species, belonging to 7 genera were identified, besides 16 species belonging to three genera were identified up to genus level. Out of these, six species viz., Glomus xanthium, Scutellospora tricalypta, S. armeniaca, Dentiscutata erythropa, Septoglomus deserticola and S. constrictum have not been reported from India so far so these are the first records from India. Glomus species was the most common and predominant AM fungus with frequency occurrence of 60.75%, followed by Acaulospora spp. (22.82%), Scutellospora spp. (8.05%) and Septoglomus spp. (4.69%). However, Dentiscutata spp., Fumneliformis spp. and Gigaspora spp. were rarely encountered.

Dual RNA-seq reveals large-scale non-conserved genotype\u2009\xd7\u2009genotype-specific genetic reprograming and molecular crosstalk in the mycorrhizal symbiosis

Arbuscular mycorrhizal fungi (AMF) impact plant growth and are a major driver of plant diversity and productivity. We quantified the contribution of intra-specific genetic variability in cassava (Manihot esculenta) and Rhizophagus irregularis to gene reprogramming in symbioses using dual RNA-sequencing. A large number of cassava genes exhibited altered transcriptional responses to the fungus but transcription of most of these plant genes (72%) responded in a different direction or magnitude depending on the plant genotype. Two AMF isolates displayed large differences in their transcription, but the direction and magnitude of the transcriptional responses for a large number of these genes was also strongly influenced by the genotype of the plant host. This indicates that unlike the highly conserved plant genes necessary for the symbiosis establishment, most of the plant and fungal gene transcriptional responses are not conserved and are greatly influenced by plant and fungal genetic differences, even at the within-species level. The transcriptional variability detected allowed us to identify an extensive gene network showing the interplay in plant–fungal reprogramming in the symbiosis. Key genes illustrated that the two organisms jointly program their cytoskeleton organization during growth of the fungus inside roots. Our study reveals that plant and fungal genetic variation has a strong role in shaping the genetic reprograming in response to symbiosis, indicating considerable genotype × genotype interactions in the mycorrhizal symbiosis. Such variation needs to be considered in order to understand the molecular mechanisms between AMF and their plant hosts in natural communities.

Dynamic Phosphate Uptake in Arbuscular Mycorrhizal Roots Under Field Conditions

Many crops are colonized with arbuscular mycorrhizal fungi (AMF), which can efficiently absorb nutrients such as phosphate from the soil. The utilization of mycorrhizal roots is one of the most promising options for developing resource-saving and sustainable agricultural systems. Most laboratory studies have illustrated the roles of AM symbiosis by inoculating plants with limited AMF isolates. In the field, however, the roots of crops are co-colonized with multiple AMF species, which are difficult to separate and identify and may have different abilities regarding phosphate uptake. Given advances in high-throughput sequencing technologies, such multi-component phosphate uptake systems under field conditions are the new frontier in mycorrhizal research and are crucial for managing the phosphate nutrition of crops. However, it is still difficult to understand which AMF are functional due to the dynamics of AMF colonization processes and the largely unknown genomic structure. This review summarizes key discoveries supporting the importance of the dynamics of AM colonization and genomic structure, which potentially influence the characteristics of AM phosphate uptake. Moreover, this review aims to identify the research direction necessary to obtain a better understanding of the phosphate uptake systems of crops in the field.

Mycorrhizal inoculation and application of cattle manure in field-grown maize in semiarid conditions

AbstractWe evaluated the effects of cattle manure and inoculation with arbuscular mycorrhizal fungi (AMF) in maize plants growing in a semiarid area of Brazilian north-east in 2012 and 2013. Three isolates of AMF (Acaulosporalongula URM-FMA 07 and URM-FMA 03, Claroideoglomusetunicatum UNIVASF 06A) were used, with or without the application of cattle manure, during two growing cycles. In the first year, significant effects of inoculation were detected for straw yield only when the manure was applied. In the second year, there was an interaction between fertilisation and inoculation for plant height and grain yield, with the highest values in the fertilised treatments. Inoculation with A. longula demonstrated that mycorrhizal inoculation in field-grown plants could be an alternative management for improving plant growth and grain yield, reducing the use of cattle manure. The AMF sporulation and mycorrhizal colonisation were improved after inoculation, and A. longula URM-FMA 07 increased sporulation by more than 15 times while inoculation with C. etunicatum increased sporulation by more than 3 times. The mycorrhizal inoculation is a management practice that can be useful for recovering or maintaining AMF infective propagules in soil, showing potential to be used in large-scale field conditions in Brazilian semiarid. Although mycorrhisation presents high agricultural relevance due to benefits promoted to the soil and plants, the knowledge about the factors influencing the interactions among microorganisms, soil and plants need to be broadened aiming to achieve successful crop management in semiarid regions.

Within-species phylogenetic relatedness of a common mycorrhizal fungus affects evenness in plant communities through effects on dominant species.

Arbuscular mycorrhizal fungi (AMF) have been shown to influence plant community structure and diversity. Studies based on single plant–single AMF isolate experiments show that within AMF species variation leads to large differential growth responses of different plant species. Because of these differential effects, genetic differences among isolates of an AMF species could potentially have strong effects on the structure of plant communities. We tested the hypothesis that within species variation in the AMF Rhizophagus irregularis significantly affects plant community structure and plant co-existence. We took advantage of a recent genetic characterization of several isolates using double-digest restriction-site associated DNA sequencing (ddRADseq). This allowed us to test not only for the impact of within AMF species variation on plant community structure but also for the role of the R. irregularis phylogeny on plant community metrics. Nine isolates of R. irregularis, belonging to three different genetic groups (Gp1, Gp3 and Gp4), were used as either single inoculum or as mixed diversity inoculum. Plants in a mesocosm representing common species that naturally co-exist in European grasslands were inoculated with the different AMF treatments. We found that within-species differences in R. irregularis did not strongly influence the performance of individual plants or the structure of the overall plant community. However, the evenness of the plant community was affected by the phylogeny of the fungal isolates, where more closely-related AMF isolates were more likely to affect plant community evenness in a similar way compared to more genetically distant isolates. This study underlines the effect of within AMF species variability on plant community structure. While differential effects of the AMF isolates were not strong, a single AMF species had enough functional variability to change the equilibrium of a plant community in a way that is associated with the evolutionary history of the fungus.

Controlling Powdery Mildew; Use of Arbuscular Mycorrhizal Fungi as Biocontrol Agent instead of Chemical Fungicides

Plant protection based solely on modern fungicides could lead to genetic changes in neurons of animal and humans that contribute to cases of autism and Alzheimer disease, unless the bio control agents is applied or replaced. Most researches is focused on the strongest chemical fungicides, dangerous to human health, for effective plant disease control and we believe that non-chemical control methods such as biological agents like AMF are of great importance. The aim of study was to investigate whether the soil inoculation with Glomus isolates of arbuscular mycorrhizal fungi (AMF) affected control of powdery mildew disease of apple MM111 and its survival and growth instead of use of chemical fungicides such as Flint and Stroby. Twenty apple seedlings were randomly arranged to 4 treatments, each with 5 replicates (T1, control = no AMF, no fungicide, T2= Flint fungicide, T3= Stroby fungicide and T4 = only AMF mixture) and were monitored throughout 9 weeks. All seedlings were exposed to powdery mildew on week 6 and only T2 and T3 plants treated by fungicides after developing mildew colonies on the leaves. Results showed that, seedling length in plants cultivated in AMF-inoculated-soil was significantly higher than other treatments especially in weeks 1-4 and weeks 6-9. Leaf growth rate of all plants during the experimental growth period non-significantly increased between treatments with the exception of first week that did show a significant increase in leaf growth rate of group 4 plants, even after exposure to disease. T4 samples showed a high average of leaves numbers (P < 0.05) in compared to other groups followed by T3 samples during the experimental growth period. The data from this study confirmed the response of seedling and leaf growth rates of apple seedlings to mycorrhizal colonization. It was concluded that plants cultivated in soil inoculated to AMF throughout 6 weeks had higher resistance and growth rates against Podosphaera leucotricha fungi as an agent of powdery mildew disease in apple seedling and it can be considered as an applicable strategy in biocontrol measures against pathogens when most researches is focused on chemical fungicides.

Arbuscular mycorrhizal fungi and sewage sludge enhance growth and adaptation of Metrosideros laurifolia on ultramafic soil in New Caledonia: A field experiment

The ecological restauration of nickel mining-degraded areas in New Caledonia is strongly limited by soil mineral nutrient deficiencies, heavy metal toxicity and slow growth rate of the native plant species. The improvement of revegetation technics needs multidisciplinary knowledge. A field experiment with relocated topsoil was assessed to test plant inoculation with a mix of three selected arbuscular mycorrhizal fungi (AMF) combined with sewage sludge amendment of the soil. Metrosideros laurifolia seedlings, an endemic Myrtaceae, were inoculated with the mixed AMF isolates and grown in a nursery for 18 months before being planted. 528 days after plantation, the dry weight of inoculated plants was 4 times higher than non-inoculated ones. AMF inoculated plants growing in sewage sludge amended soil showed a dry weight more than seven times higher than control plants. These differences were positively correlated with mycorrhizal colonization. However at this stage, AMF inoculated isolates were reduced in roots of M. laurifolia and replaced by several AMF indigenous species. This AMF diversity was higher in inoculated plants and in non-amended plots. Inoculated plants were characterized by a better mineral nutrition, a higher Ca/Mg ratio and a lower heavy metal translocation. In conclusion, this study showed that AMF inoculation combined with sewage sludge amendment of soil can improve ecological restoration of ultramafic mine-degraded areas.

Keragaman Fungi Mikoriza Arbuskula Pada Tumbuhan Pokem [Setaria italica (L.) Beauv.] dengan Metode Traping

Arbuscular Mycorrhizal Fungi (AMF) plays important role in increasing plant growth and plant protection against pathogen. Its diversity depends on their habitat, including the abundance and distribution of the host plant on agricultural area. This research has aim to explore the diversity of AMF from the rhizosphere of Pokem (Setaria italica) using trapping methods. Soil samples were collected from Numfor Island, Biak Numfor, Papua. The isolation of AMF from the soil sample was elucidated by wet sieving method. Every different spore then was inoculated to the root of Desmodium heterocarpon to propagate and monosporic culture was grown on Shorgum bicolor.  The result showed that the number of the spore that was obtained by traping method increased up to 63,63%. Single spores inoculation of AMF on D. heterocarpon was high percentage (85%) of success. On average, Monosporic culture of single spore inoculation on S. bicolor reached up to 30,53 spores/10g soil sample.  There are 6 genera (9 species) were obtain in this study, namely Glomus, Claroideoglomus, Scutellospora, Gigaspora, Ambispora and Acaulospora. Furthermore, identification using molecular method should be done for proper identification.Key words: AMF, plant rhizosfer, S. italica, trapping methods

Direct effects of soil cadmium on the growth and activity of arbuscular mycorrhizal fungi

A compartment cultivation system was developed to study the effect of cadmium (Cd) in soil on the development of arbuscular mycorrhizal fungi (AMF) under the same host conditions. Fungal compartments consisting of four levels of Cd addition rate (0, 5, 25 and 50 mg kg−1) were inserted into each porcelain pot in the greenhouse. Mycorrhizal development by Glaroideoglomus etunicatum and Glaroideoglomus claroideum was determined at three growth stages of Cucumis sativus. Both AMF isolates showed good root colonization during plant growth. Total extraradical mycelium (ERM) length and active ERM length reached a maximum at low Cd addition rate (5 mg kg−1) and were inhibited at the higher Cd addition rate (25 and 50 mg kg−1). The two AMF isolates showed different responses to Cd addition at the three growth stages and G. claroideum seemed to be more tolerant to Cd toxicity. These results showed a potential to use this technique to study the function of soil-grown AMF hyphae.

Effects of two contrasted arbuscular mycorrhizal fungal isolates on nutrient uptake by Sorghum bicolor under drought.

Drought is a limiting factor for crop production, especially in arid and semi-arid climates. In this study, Sorghum bicolor plants were inoculated, or not, with Rhizophagus irregularis, an arbuscular mycorrhizal (AM) strain typical for temperate climates, or Rhizophagus arabicus, a strain endemic to hyper-arid ecosystems. Plants were grown under well-watered or drought conditions in compartmented microcosms. Transpiration rates, plant growth, and nutrient uptake (using 15N as a tracer) were determined to assess the impact of drought stress on sorghum plants in AM symbiosis. Although AM colonization did not affect the bulk biomass of host plants, R. arabicus improved their transpiration efficiency and drought tolerance more than R. irregularis. Moreover, R. arabicus was able to extract more 15N from the soil under both water regimes, and AM-driven enhancement of the nitrogen and phosphorus content of sorghum, especially when water was limiting, was greater for R. arabicus-inoculated plants than for R. irregularis-inoculated plants. Our work demonstrates close links between AM hyphal phosphorus and nitrogen transport and uptake by AM plants for both AM fungal species. It also underscores that, under the drought stress conditions we applied, R. arabicus transfers significantly more nitrogen to sorghum than R. irregularis.

MICROBIAL INTERACTIONS IN THE DEVELOPMENT OF THE BIOMASS OF GLIRICIDIA

ABSTRACT The objective of this work was to evaluate the interaction of microorganisms and phosphorus dosages in the development of gliricidia. The experimental design was completely randomized with six treatments (control, native microbial inoculant, and four arbuscular mycorrhizal fungi isolates: UFLA05 - Gigaspora albida, UFLA351 - Rhizoglomus clarum, UFLA372 - Claroideoglomus etunicatum, and UFLA401 - Acaulospora morrowiae), with four replicates. The parameters evaluated were: height plant, the number of branches, shoot and root dry mass matter, root length and volume, leaf phosphorus, mycorrhizal colonization, the number of spores of the arbuscular mycorrhizal fungi, the number of nodules of nitrogen fixing bacteria, and the presence of endophytic dark septate fungi, after 95 days of inoculation. The high mycorrhizal colonization of gliricidia does not guarantee an increase in biomass, which depends on the interaction of the arbuscular mycorrhizal fungi, the endophytic dark septate fungi, the nitrogen fixing bacteria, and the endophytic bacteria. Gliricidia was responsive to the inoculation of the native microbiota, UFLA372 and UFLA401. Mycorrhizal colonization by UFLA401 was influenced by the presence of nitrogen fixing bacteria. Gliricidia was not responsive to the inoculation of UFLA05 and UFLA351. The presence of the endophytic dark septate fungi did not inhibit mycorrhization and the formation of nodules of nitrogen fixing bacteria in gliricidia.

Mycorrhiza-Induced Alleviation of Plant Disease Caused by Clavibacter michiganensis Subsp. Michiganensis and Role of Ethylene in Mycorrhiza-Induced Resistance in Tomato

The protective role of arbuscular mycorrhizal fungi (AMF) against the phytopathogen Clavibacter michiganensis subsp. michiganensis (Cmm) was examined in tomato plants. Seven different AMF isolates were used to determine which ones were able to induce effectively resistance against Cmm. Stems of seven-week tomato plants were infected with Cmm, then a disease severity index (DSI) was determined during the next three weeks. In addition to different responses to mycorrhizal inoculation, three levels of responses to the bacterial disease were recognized in treatments. Plants inoculated with Rhizophagus irregularis (Ri) showed both the highest colonization and the highest induced resistance to Cmm while the effect of Funneliformis mosseae, Gigaspora margarita and Claroideoglomus claroideum on mycorrhizal colonization and on the induced resistance were intermediate and high, respectively. Subsequently, Ri was chosen to inoculate ethylene-insensitive tomato mutant line Never ripe (Nr) and its background (Pearson) to investigate the possible role of ethylene (ET) in the mycorrhiza-induced resistance (MIR). The results showed that Ri could induce systemic resistance against Cmm in the Pearson background, whereas ET-insensitivity in Nr plants impaired MIR. These results suggest that ET is required for Ri-induced resistance against Cmm. To our knowledge, this is the first study to examine the effect of different AMF isolates on the response of tomato plants to Cmm and involvement of ET in MIR against Cmm.

Placing arbuscular mycorrhizal fungi on the risk assessment test battery of plant protection products (PPPs).

Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts considered a key group in soil systems involved in the provision of several ecosystem services. Recently they have been listed by EFSA as organisms to be included in the test battery for the risk assessment of plant protection product (PPPs). This study aimed to contribute to improve the ISO Protocol (ISO 10832: 2009) by assessing the feasibility of using other AMF species under different test conditions. Overall, results showed that AMF species Gigaspora albida and Rhizophagus clarus (selected out of five AMF species) are suitable to be used in spore germination tests using the ISO protocol (14 days incubation with sand or artificial soil as substrate) to test PPPs. However, several modifications to the protocol were made in order to accommodate the use of the tested isolates, namely the incubation temperature (28 °C instead of 24 °C) and the change of reference substance (boric acid instead of cadmium nitrate). The need for these changes, plus the results obtained with the three fungicides tested (chlorothalonil, mancozeb and metalaxyl-M) and comparisons made with literature on the relevance of the origin of AMF isolates in dictating the adequate test conditions, emphasize the importance of adjusting test conditions (AMF species/isolates and test temperature) when assessing effects for prospective risk assessment targeting different climatic zones. So, further studies should be conducted with different AMF species and isolates from different climatic regions, in order to better define which species/isolate and test conditions should be used to assess effects of a particular PPP targeting a given climatic zone.

Growth of typha grass (Typha angustifolia) on gold-mine tailings with application of arbuscular mycorrhiza fungi

Setyaningsih L, Wulandari AS, Hamim H. 2018. Growth of typha grass (Typha angustifolia) on gold-mine tailings with application of arbuscular mycorrhiza fungi. Biodiversitas 19: 504-509. Gold mine tailings contain extreme physical and chemical properties, which inhibit plant growth due to lower nutrition and higher heavy metal contaminants. Typha (Typha angustifolia) is type of grass growing well on waterlogged area including tailing dam. The objective of this study was to investigate the effect of arbuscular mycorrhizal fungi (AMF) in combination with compost and soil on the typha growth in gold mine tailings. The study was conducted in greenhouse by inoculating two AMF isolates (Glomus etunicatum and G. manihotis) to typha seedlings grown in pure tailing media, mixed tailing-compost media, and mixed tailing-compost-soil media. The compatibility and growth of typha grass were analysed after 1 month. Results showed that G. etunicatum and G. manihotis application significantly increased AMF colonization of typha roots up to 16.6% and 21.8% respectively. The length, number of leaves and biomass of typha also increased up to 90%, 50% and 97% respectively compared to those without AMF inoculation. G. etunicatum contributed the best growth of typha grown in mixed compost-soil-tailings, resulting in double increase of its length and biomass. The application of G. manihotis did not significantly increase the growth of typha in mixed media; however, under pure tailing, this mycorrhiza had the best induction for typha biomass and leaf number. In general, AMF application increased growth of typha grass in tailings media.

Effectiveness of Arbuscular Mycorrhizal Fungal Isolates from the Land Uses of Amazon Region in Symbiosis with Cowpea.

Arbuscular mycorrhizal fungi provide several ecosystem services, including increase in plant growth and nutrition. The occurrence, richness, and structure of arbuscular mycorrhizal fungi communities are influenced by human activities, which may affect the functional benefits of these components of the soil biota. In this study, 13 arbuscular mycorrhizal fungi isolates originating from soils with different land uses in the Alto Solimões-Amazon region were evaluated regarding their effect on growth, nutrition, and cowpea yield in controlled conditions using two soils. Comparisons with reference isolates and a mixture of isolates were also performed. Fungal isolates exhibited a wide variability associated with colonization, sporulation, production of aboveground biomass, nitrogen and phosphorus uptake, and grain yield, indicating high functional diversity within and among fungal species. A generalized effect of isolates in promoting phosphorus uptake, increase in biomass, and cowpea yield was observed in both soils. The isolates of Glomus were the most efficient and are promising isolates for practical inoculation programs. No relationship was found between the origin of fungal isolate (i.e. land use) and their symbiotic performance in cowpea.

High intraspecific genome diversity in the model arbuscular mycorrhizal symbiont Rhizophagus irregularis.

Arbuscular mycorrhizal fungi (AMF) are known to improve plant fitness through the establishment of mycorrhizal symbioses. Genetic and phenotypic variations among closely related AMF isolates can significantly affect plant growth, but the genomic changes underlying this variability are unclear. To address this issue, we improved the genome assembly and gene annotation of the model strain Rhizophagus irregularis DAOM197198, and compared its gene content with five isolates of R.irregularis sampled in the same field. All isolates harbor striking genome variations, with large numbers of isolate-specific genes, gene family expansions, and evidence of interisolate genetic exchange. The observed variability affects all gene ontology terms and PFAM protein domains, as well as putative mycorrhiza-induced small secreted effector-like proteins and other symbiosis differentially expressed genes. High variability is also found in active transposable elements. Overall, these findings indicate a substantial divergence in the functioning capacity of isolates harvested from the same field, and thus their genetic potential for adaptation to biotic and abiotic changes. Our data also provide a first glimpse into the genome diversity that resides within natural populations of these symbionts, and open avenues for future analyses of plant-AMF interactions that link AMF genome variation with plant phenotype and fitness.