C. Arriagada

Crop residue stabilization and application to agricultural and degraded soils: A review

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.

Contribution of the saprobic fungi Trametes versicolor and Trichoderma harzianum and the arbuscular mycorrhizal fungi Glomus deserticola and g. claroideum to arsenic tolerance of Eucalyptus globulus.

The presence of high concentrations of arsenic (As) decreased the shoot and root dry weight, chlorophyll and P and Mg content of Eucalyptus globulus colonized with the arbuscular mycorrhizal (AM) fungi Glomus deserticola or G. claroideum, but these parameters were higher than in non-AM plants. As increased the percentage of AM length colonization and succinate dehydrogenase (SDH) activity in the root of E. globulus. Trichoderma harzianum, but not Trametes versicolor, increased the shoot and root dry weight, chlorophyll content, the percentage of AM root length colonization and SDH activity of E. globulus in presence of all As concentrations applied to soil when was inoculated together with G. claroideum. AM fungi increased shoot As and P concentration of E. globulus to higher level than the non-AM inoculated controls. The contribution of the AM and saprobe fungi to the translocation of As from root to shoot of E. globulus is discussed.

Improvement of growth of Eucalyptus globulus and soil biological parameters by amendment with sewage sludge and inoculation with arbuscular mycorrhizal and saprobe fungi.

Sewage sludge is widely used as an organic soil amendment to improve soil fertility. We investigated the effects of sewage sludge (SS) application on certain biological parameters of Eucalyptus globulus Labill. The plant was either uninoculated or inoculated with saprobe fungi (Coriolopsis rigida and Trichoderma harzianum) or arbuscular mycorrhizal (AM) fungi (Glomus deserticola and Gigaspora rosea). Sewage sludge was applied to the surface of experimental plots at rates of 0, 2, 4, 6 and 8 g 100 g(-1) of soil. Inoculation with both AM and saprobe fungi in the presence of SS was essential for the promotion of plant growth. The AM, saprobe fungi and SS significantly increased dry shoot weight. The AM fungi induced a significant increase in Fluorescein diacetate (FDA) activity but did not increase beta-glucosidase activity. Addition of SS to AM-inoculated soil did not affect either FDA or alpha-glucosidase activities in plants from soil that was either uninoculated or inoculated with the saprobe fungi. SS increased beta-glucosidase activity when it was applied at 4 g 100 g(-1). SS negatively affected AM colonization as well as the mycelium SDH activity for both mycorrhizal fungi. SS increased Eucalyptus shoot biomass and enhanced its nutrient status. Inoculation of the soil with G. deserticola stimulated significant E. globulus growth and increases in shoot tissue content of N, P, K, Ca, Mg and Fe. Dual inoculation with G. deserticola and either of the saprobe fungi had positive effects on K, Ca, Mg and Fe contents. The application of 8 g 100 g(-1) of SS had no positive effects on plant nutrition. The experimental setup provided a suitable tool for evaluating SS in combination with saprobe and AM fungi as a biological fertiliser for its beneficial effects on E. globulus plant growth.

The effects of the arbuscular mycorrhizal fungus Glomus deserticola on growth of tomato plants grown in the presence of olive mill residues modified by treatment with saprophytic fungi.

Olive oil extraction generates large amounts of olive mill residues (DOR) which may be used as fertilizer. The influence of arbuscular mycorrhizal (AM) on the phytotoxicity of dry olive residue (DOR) transformed with saprophytic fungi was studied. Aqueous extraction of DOR gave an (ADOR) fraction and an exhausted (SDOR) fraction, both of which had less phytotoxicity for tomato than the original DOR. The saprophytic fungiTrametes versicolor andPycnoporus cinnabarinus further decreased the phytotoxicity of ADOR and SDOR on tomato. The decrease of phenols concentration and the differences in the level of laccase activity caused by these fungi suggest did not account fully for the reduced phytoxicity but the fact that the higher hydrolytic enzyme activity ofP. cinnabarinus, paralleled the decrease of phytotoxicity, indicates that these enzymes seem to be involved. The AM fungusGlomus deserticola increased or exacerbated the beneficial effect of SDOR incubated with saprophytic fungi, in terms of dry weight of tomato plants. The percentage of root length colonized byG. deserticola strongly decreased in presence of DOR, but the level of mycorrhization was higher in presence of ADOR or SDOR. Our results suggest that the combination of aqueous extraction and incubation with saprophytic fungi will open the way for the use of olive oil extraction residues as organic amendment in agricultural soils.

Interactions of Trametes versicolor, Coriolopsis rigida and the arbuscular mycorrhizal fungus Glomus deserticola on the copper tolerance of Eucalyptus globulus

The presence of high levels of Cu in soil decreases the shoot and root dry weights of Eucalyptus globulus. However, higher plant tolerance of Cu has been observed in the presence of the arbuscular mycorrhizal (AM) fungus Glomus deserticola. The hyphal length of G. deserticola was sensitive to low Cu concentrations, and the percentage of AM root colonisation and the metabolic activity of the AM fungus were also decreased by Cu. Therefore, a direct effect of Cu on the development of the AM fungus inside and outside the root cannot be ruled out. E. globulus colonised by G. deserticola had higher metal concentrations in the roots and shoots than do non-mycorrhizal plants; however, the absence of a higher root to shoot metal ratio in the mycorrhizal plants (1.70+/-0.11) indicated that G. deserticola did not play a filtering/sequestering role against Cu. The saprobe fungi Coriolopsis rigida and Trametes versicolor were able to remove Cu ions from the asparagine-glucose growth media. However, plants inoculated with C. rigida and T. versicolor did not accumulate more Cu than non-inoculated controls, and the growth of the plant was not increased in the presence of these fungi. However, C. rigida increased the shoot dry weight, AM root length colonisation, and metabolic mycelial activity of plants colonised with G. deserticola in the presence of Cu; only this saprobe-AM fungus combination increased the tolerance of E. globulus to Cu. Inoculation with G. deserticola and C. rigida increased the E. globulus Cu uptake to levels reached by hyperaccumulative plants.

Synergistic interactions between a saprophytic fungal consortium and Rhizophagus irregularis alleviate oxidative stress in plants grown in heavy metal contaminated soil

Background and aimAccumulation of heavy metals in soil causes loss of cover vegetation and increases the production of reactive oxygen species (ROS). ROS accumulation induces the expression of genes encoding antioxidant enzymes and other proteins involved in redox homeostasis. This study aimed to evaluate the interaction between a saprophytic fungal consortium and mycorrhizal Rhizophagus irregularis with regard to the oxidative stress and molecular responses of Solanum lycopersicum L. grown in a soil contaminated with heavy metals.MethodsWe determined the effects of the saprophytic fungal consortium (Bjerkandera adusta and Mortierella sp) and the mycorrhizal fungus Rhizophagus irregularis on the plant antioxidant response and the expression levels of genes encoding metallothioneins (MT), phytochelatins (PC), the NRAMP transporter and heat shock protein (HSP) in Solanum lycopersicum cultivated in a heavy metal-contaminated soil.ResultsThe fungal consortium increased plant growth, and the co-inoculation with R. irregularis synergistically improved soil biochemical activities. Superoxide dismutase activity decreased in all treatments. Peroxidase activity (ascorbate and guaiacol) increased in plants inoculated with R. irregularis and the fungal consortium. Dual inoculation decreased the malondialdehyde content in the leaves and increased transcription of the NRAMP, GR, MT2b, PCS and HSP90 genes.ConclusionsOur results demonstrate that co-inoculation contributes to reduced plant stress by improving defence mechanisms and homeostasis

Influence of an organic amendment comprising saprophytic and mycorrhizal fungi on soil quality and growth of Eucalyptus globulus in the presence of sewage sludge contaminated with aluminium

The single application of either sewage sludge with high aluminium concentration, wheat straw or the mixture of both residues to soil did not increase the growth of Eucalyptus globulus Labill. However, inoculation with either the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis, the saprobe fungi Coriolopsis rigida (Berk. Et Mont.) Murrill and Phanerochaete chrysosporium Burds or the combination of each saprobe with the AM fungus increased both the P concentration and dry weight of E. globulus shoots. These effects were greater in the presence of wheat straw or sewage sludge, but were greatest in the presence of the mixed residue. Phanerochaete chrysosporium had the greatest effect on plant dry weight when co-inoculated with R. irregularis in the treatment with mixed residue. The co-inoculation of AM and saprobe fungi increased fluorescein diacetate and β-glucosidase activities in the bulk soil of E. globulus grown in the treatment with mixed residue. However, only the AM fungus increased dehydrogenase activity, and phosphatase activity was similar in all treatments tested. Our results showed that sewage sludge with high aluminium concentration could be used as a soil amendment to improve the growth of E. globulus when mixed with wheat straw and co-inoculated with saprobe and arbuscular fungi.

EFFECT OF ARBUSCULAR MYCORRHIZAL FUNGAL INOCULATION ON Eucalyptus globulus SEEDLINGS AND SOME SOIL ENZYME ACTIVITIES UNDER APPLICATION OF SEWAGE SLUDGE AMENDMENT

The sewage sludge (SS) represents a source of organic matter although its increasing accumulation need a suitable environmental treatment. Our study analyzed the effect of the interaction between sewage sludge (doses 0, 2, 4, 6 and 8 g per 100 g of soil) and Eucalyptus globulus nursery seedlings inoculated with arbuscular mycorrhizal (AM) fungi as a fertilizers alternative and evaluate its effect on some soil enzyme activities. The seedlings were inoculated with Glomus claroideum, Glomus viscosum, Glomus intraradices and Glomus constrictum, establishing a uninoculated control. The sewage sludge application increased the shoot dry weight and the inoculation with G. viscosum was more effective at 6 g of SS in 100 g soil. The root colonization and succinate dehydrogenase activity was decreased by all doses of SS used. The Fluorescein diacetate activity was increased by the AM inoculation but not by sewage sludge. The β-glucosidase activity was increased in presence of SS at 6 g 100 g -1 . The N and P uptake by the E. globulus plants was higher in presence of sewage sludge and more effective with G. viscosum plant inoculation. In conclusion the application of these amounts of SS promoted the plant growth and can be regarded as a successful biotechnological tool for the greenhouse plant production.

Suppressive effect of olive residue and saprophytic fungi on the growth of Verticillium dahliae and its effect on the dry weight of tomato (Solanum lycopersicum L.)

The saprophytic fungi Aspergillus niger, Coriolopsis rigida, Fusarium lateritium, F. oxysporum, Mucor racemosus, Paecilomyces farinosus, Penicillium chrysogenum, P. restrictum, Trametes versicolor, Trichoderma harzianum, T. pseudokoningii and T. viride were able to decrease the growth in vitro of Verticillium dahlie in the presence of aqueous extract of olive residue. The conidia number of V. dahliae decreased when grown on aqueous extract of olive residue, autoclaved or filtered through 0.45 micron filters after culture of the fungi. These results suggest not only the predominance of suppressive substances of a biological nature, but also the existence of non-biological inhibitory substances. The olive residue decreased the negative effect of V. dahliae on shoot and root dry weight of tomato (Solanum lycopersicum L.), by the antifungal compounds present in the olive residue and by the antifungal substances produced by the antagonistic saprophytic fungi grown in this residue.

Reduced dry olive residue phytotoxicity in the field by the combination of physical and biological treatments

Olive oil extraction generates large amounts of olive mill residues (DOR) which may be used as organic fertilizer. The influence of a combination of physical fractionation and saprobe fungal incubation on the phytotoxicity of DOR was studied. The physical fractions of DOR, obtained following extraction using ethyl acetate (EDOR) and wa- ter (ADOR) were less phytotoxic than DOR with respect to the shoot dry weight of to- mato. There was no relationship between the total phenol content of the different DOR physical fractions and their phytotoxicity. The saprophytic fungus Coriolopsis rigida reduced DOR and ADOR phytotoxicity and eliminated the phytotoxicity of EDOR. However, unlike the physical treatments of DOR, the decrease in the phenol content of EDOR and ADOR caused by C. rigida was closely paralleled to the decrease in their phytotoxicity. After 30 days of incubation, C. rigida was able to eliminate the phytotoxicity of EDOR on tomato plants grown in the field.