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Abstract: A pot culture experiment was carried out to assay the behavior of different arbuscular mycorrhizal (AM) fungal inocula on plant growth and copper (Cu) uptake using two metallophytes (Oenothera picensis and Imperata condensata) and one agricultural plant (Helianthus annuus) grown at increasing Cu supply levels. Plants were established in a Cu polluted soil spiked with 0, 150, 300 or 450mg Cukg−1, and inoculated or not with: (i) Cu-adapted AM fungi (GA) or (ii) the Cu non-adapted strain Glomus claroideum (GC). Differences in plant biomass between inoculated and uninoculated plants were found, which were dependent on the AM fungal inocula used and the Cu level applied. Although the beneficial effect of AM fungi in promoting plant biomass production was not observed in metallophytes plants, a positive interaction between GA and H. annuus increased the shoot growth, especially at higher Cu levels. In addition, the Cu transfer from the roots to the shoots was low, remaining mostly at root level, especially in non-mycorrhizal plants; however AM fungi produced changes in Cu distribution increasing the translocation to the shoots. Differences in AM fungal parameters (root colonization, spore number and glomalin production) were strictly dependent on the Cu level and the AM fungal inoculum, suggesting the existence of certain compatibility, which was dependent on the particular combination AM-plant used. Specifically, the glomalin accumulation and Cu-bound to glomalin were significantly higher in AM colonized H. annuus plants, which could suggest a highly efficient way to reduce the Cu toxicity levels in soil. Therefore the use of H. annuus with AM fungal could promote phytostabilization processes. [Copyright &y& Elsevier]

Abstract: Arbuscular mycorrhizal spores and glomalin-related soil protein (GRSP) isolated from acid soils were analyzed using confocal laser scanning microscopy (CLSM) for Al detection. Mycorrhizal structures of Glomus intraradices produced under in vitro conditions as well as spores and GRSP from neutral and Cu-polluted soils were used as contrasting criteria. Spores and GRSP from soils with 7 and 70% Al saturation showed autofluorescence which increased especially at the highest soil Al level and when Al3+ solution was added. G. intraradices spores showed fluorescence only when exogenous Al3+ was added. On the contrary, spores and GRSP from neutral and Cu-polluted soils showed little or no significant fluorescence. This fluorescence shown by fungal structures and GRSP when subjected to high Al (of endogenous or exogenous origin) suggest a high capacity for Al immobilization, which could be an effective way to reduce Al activity and phytotoxicity in acid soils. [Copyright &y& Elsevier]

This study aimed to examine how interactions at both plant genotype and arbuscular mycorrhizal fungus species levels affected the expression of root traits and the subsequent effect on plant nutrition and growth. We used two wheat cultivars with contrasting phosphorus (P) acquisition efficiencies (Tukan and Crac) and two arbuscular mycorrhizal (AM) fungi (Rhizophagus intraradices and Claroideoglomus claroideum). Plant growth, as well as morphological and architectural root traits, were highly dependent on the myco-symbiotic partner in the case of the less P-acquisition efficient cultivar Tukan, with mycorrhizal responses ranging from -45 to 54 % with respect to non-mycorrhizal plants. Meanwhile, these responses were between only -7 and 5 % in the P-acquisition efficient cultivar Crac. The AM fungal species produced contrasting mechanisms in the improvement of plant nutrition and root trait responses. Colonization by R. intraradices increased Ca accumulation, regardless of the cultivar, but reduced root growth on Tukan plants. On the other hand, C. claroideum increased P content in both cultivars, with a concomitant increase in root growth and diffusion-based nutrient acquisition by Tukan. Moreover, plants in symbiosis with R. intraradices showed greater organic acid concentration in their rhizosphere compared to C. claroideum -colonized plants, especially Tukan (24 and 35 % more citrate and oxalate, respectively). Our results suggest that the responses in plant-AM fungal interactions related to nutrient dynamics are highly influenced at the fungus level and also by intra-specific variations in root traits at the genotype level, while growth responses related to improved nutrition depend on plant intrinsic acquisition efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] AM fungal diversity was characterized in six Al tolerant wheat cultivars. [•] Acaulospora and Scutellospora were the most dominant AM fungal genera. [•] AM fungal S and D could be a tool for the selection of Al tolerant wheat cultivars. [•] Wheat cultivar can determine the AM fungal diversity in soil with high Al levels. [ABSTRACT FROM AUTHOR]

Wheat ( Triticum aestivum L.) cultivars vary extensively in their response to acidic soils. In southern Chile, wheat genotypes have been selected for growth on acidic Andisols where high concentrations of phytotoxic aluminum (Al) limit plant growth. Previous work indicates that arbuscular mycorrhizal (AM) fungi play an important role protecting plant roots against the deleterious effects of Al. To understand interactions between AM fungi and cultivar Al phytotoxicity, six locally used wheat cultivars (‘Bakan’, ‘Crac’, ‘Invento’, ‘Maxi’, ‘Otto’, and ‘Porfiado’) were cultivated in a non-limed and limed Andisol (74 and 5% Al saturation, respectively). Plant harvests were carried out at two phonological stages: tillering (60 days after sowing, DAS) and physiological maturity (150 DAS). Plant growth was limited on non-limed soil, but varied by cultivar. Among the cultivars, ‘Porfiado’ and ‘Crac’ exhibited growth traits consistently associated with acidic soil resistance, including greater biomass and root length and higher P/Al and Ca/Al ratios in plants grown in non-limed soil. Wheat growth was positively correlated with AM colonized root length and Al bound to glomalin related soil protein (Al-GRSP). In addition, root Al concentration was negatively correlated with colonized root length and Al-GRSP across all wheat cultivars grown under high Al saturation. The significantly better performance of wheat cultivars and their association with AM fungal traits on non-limed soils indicates that indigenous AM fungal populations in acidic soils may contribute to Al tolerance of some wheat cultivars when growing at high Al levels. [ABSTRACT FROM AUTHOR]

Agricultural activities produce vast amounts of organic residues including straw, unmarketable or culled fruit and vegetables, post-harvest or post-processing wastes, clippings and residuals from forestry or pruning operations, and animal manure. Improper disposal of these materials may produce undesirable environmental (e.g. odors or insect refuges) and health impacts. On the other hand, agricultural residues are of interest to various industries and sectors of the economy due to their energy content (i.e., for combustion), their potential use as feedstock to produce biofuels and/or fine chemicals, or as a soil amendments for polluted or degraded soils when composted. Our objective is review new biotechnologies that could be used to manage these residues for land application and remediation of contaminated and eroded soils. Bibliographic information is complemented through a comprehensive review of the physico-chemical fundamental mechanisms involved in the transformation and stabilization of organic matter by biotic and abiotic soil components. [ABSTRACT FROM AUTHOR]

Abstract: The alleviation of copper (Cu) toxicity in the pseudometallophyte Oenothera picensis via arbuscular mycorrhizal fungi (AMF) inoculation and/or sugar beet agrowaste (SB) application was evaluated at increasing soil Cu levels. Plants were grown in Cu-treated soils (0, 100 or 500mgCukg−1), either with or without SB application, and inoculated with: (i) Cu-adapted Glomeromycotan fungi (GA); (ii) Glomus claroideum (GC); or (iii) no fungus (uninoculated). Application of SB amendment increased shoot biomass 2–8-fold with respect to the unamended soils, and allowed the survival of non-mycorrhizal- and GC-inoculated plants, even at the highest Cu level. Additionally, SB application increased shoot Cu content at higher Cu levels and shoot P content especially at lower Cu levels. In general, compared to GC-inoculated plants, GA inoculation caused a decrease in both superoxide dismutase and ascorbate peroxidase antioxidant enzyme activities in shoots (up to levels of 100mgCukg−1), as well as glutathione reductase and catalase activities (up to 500mgCukg−1). Finally, in SB treated plants, GA colonization was higher as compared to GC-inoculated plants, especially at the highest Cu level. These results suggest a relevant role of Glomeromycotan fungal populations isolated from Cu-polluted environments in the alleviation of Cu toxicity that could allow their use in remediation programs for Cu-polluted soils. [Copyright &y& Elsevier]

Abstract: Increasing evidence suggests that accretion of microbial turnover products is an important driver for isotopic carbon (C) and nitrogen (N) enrichment of soil organic matter (SOM). However, the exact contribution of arbuscular mycorrhizal fungi (AMF) to soil isotopic patterns remains unknown. In this study, we compared 13C and 15N patterns of glomalin-related soil protein (GRSP), which includes a main fraction derived from AMF, litter, and bulk soil in four temperate rainforests. GRSP was an abundant C and N pool in these forest soils, showing significant 13C and 15N enrichment relative to litter and bulk soil. Hence, cumulative accumulation of recalcitrant AMF turnover products in the soil profile likely contributes to 13C and 15N enrichment in forest soils. Further research on the relationship between GRSP and AMF should clarify the exact extent of this process. [Copyright &y& Elsevier]

The amount of glomalin-related soil protein (GRSP), a glycoprotein produced by arbuscular mycorrhizal fungi (AMF), its contribution to the sequestering of Cu and Zn in the soil, and the microsite variation of other soil traits (pH, water-stable aggregates—[WSA], soil organic carbon—[SOC]) was studied in a semi-arid Mediterranean ecosystem near a copper smelter and affected by deposit of metal-rich particles since 1964. Rhizospheric (R) and non-rhizospheric (NR) soil of four representative plants (Argemone subfusiformis, Baccharis linearis, Oenothera affinis and Polypogon viridis) was analyzed. The results showed a strong variability in GRSP (6.6–36.8 mg g−1), Cu content (62–831 mg kg−1 for the total Cu and 5.8–326 mg kg−1 for the available Cu) and pH (4.2–5.5) in the different plant and rhizospheric zones analyzed. A strong relationship between the GRSP with the soil Cu and Zn contents was found (r =0.89 and 0.76 for Cu and Zn respectively, p <0.001). The GRSP-bound Cu ranged from 3.76 to 89.0 mg g−1 soil and represents 1.44–27.5% of the total Cu content in soil. Moreover, the WSA reached 89% in P. viridis R. For this plant, the C contained in GRSP represented up to 89% of SOC, and this coincided with the most extreme conditions of soil degradation within the ecosystem (the highest content of heavy metals and low pH values). This study provides evidence on the role of the GRSP in Cu and Zn sequestration and suggests a highly efficient mechanism of AMF to mitigate stress leading to stabilization of soils highly polluted by mining activities. [Copyright &y& Elsevier]