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A consortium of fungal isolates may improve phytoremediation by stimulating root growth whereas biochar reduces metal leaching in contaminated soils. We combined these treatments to evaluate to what extent Jacaranda mimosifolia D. Don seedlings extract metals (Cu, Mn, and Zn) and reduce leaching in soil columns. Contamination treatments were established by combining Cu (200 mg dm−3), Mn (450 mg dm−3), and Zn (450 mg dm−3). A spore suspension of five fungal isolates (Beauveria bassiana, Metarhizium anisopliae, Pochonia chlamydosporia, Purpureocillium lilacinum, and Trichoderma asperella) was sprayed on plant shoots and the soil surface. Biochar (1% m/v) was produced by the pyrolysis of wood sawdust and applied to the soil surface. Finally, control treatments were established in a completely randomized block design. The consortium of fungal isolates increased shoot and root mass, improved the translocation potential of Cu (translocation factor (TF) of 0.25), Mn (TF of 2.93), and Zn (TF of 1.79) from roots to shoots, and increased the total accumulated mass of Mn and Zn in shoots and roots. Biochar applications improved Cu, Mn, and Zn translocation and increased the total accumulated mass of shoot Mn. Moreover, a combination of fungal isolates and biochar increased the translocation factor to 0.44 for Cu, 1.70 for Mn, and 1.34 for Zn relative to the treatment with J. mimosifolia in contaminated soil (CJ); increased shoot Cu concentration; and reduced total leached Cu by a factor of 22.9, Mn by 5.5, and Zn by 22.9 relative to the CJ treatment. A photochemical profile, based on chlorophyll a fluorescence, showed that Jacaranda mimosifolia was tolerant to contaminated soil and is a potential phytoremediator of Cu, Mn, and Zn. Overall, the consortium of fungal isolates and biochar improved the efficiency of phytoremediation by concentrating metals in plant tissue and reducing the risks of leaching.

Some fungal isolates affect soil by solubilizing nutrients and promoting plant growth; however, little is known about the effects of applications of these isolates on soil biology and fertility. Thus, the aim of the present study was to identify the effect of five well-known fungal endophytes, namely, Beauveria bassiana, Trichoderma asperellum, Metarhizium anisopliae, Purpureocillium lilacinum and Pochonia chlamydosporia on plant growth and the biological and chemical properties of the rhizosphere soil under Phaseolus vulgaris L. Spore suspensions from each of the five fungal isolates and three consortia (T. asperellum/P. lilacinum; B. bassiana/M. anisopliae; and a consortium of all five species) were applied to seeds, soil and shoots of common bean plants in a greenhouse assay. All fungal treatments resulted in greater root colonization by arbuscular mycorrhizal fungi (53.6% of root length in control and 66.6%–77.0% in the remaining treatments), concentration of rhizosphere soil magnesium (10%–33% higher than the control) and base saturation of cation exchange capacity (48.5% in control and 50.7%–55.1% in all other treatments). Applications of B. bassiana/M. anisopliae and of the consortium of five fungal isolates increased fluorescein diacetate hydrolysis (FDA) by 63% and 72% respectively, relative to the control. β-Glucosidase activity was lower in the applications of T. asperellum (20% lower), P. chlamydosporia (15% lower) and B. bassiana/M. anisopliae (18% lower) than in the control. Acid phosphatase was lower in the M. anisopliae (29%), P. chlamydosporia (22%) and T. asperellum/P. lilacinum (21%) and B. bassiana/M. anisopliae consortia (27%) treatments. Some fungal isolate applications stimulated shoot accumulations of N, P, B, Cu, Fe, Mn and Zn (mass). Applications of B. bassiana, T. asperellum, M. anisopliae, P. chlamydosporia and the consortium of five fungal isolates resulted in higher root dry mass relative to the control, while treatments of P. lilacinum, the B. bassiana/M. anisopliae consortium and the five fungal isolates resulted in higher dry shoot weight. Arylsulfatase activity and phosphate solubilizing fungi were not affected by the treatments. The values of the rhizosphere soil chemical and biological, accumulated nutrient mass and plant growth variables were highest in the (A) five fungi consortium, followed, in descending order, by (B) the B. bassiana/M. anisopliae consortium; (C) T. asperellum, B. bassiana and M. anisopliae; and (D) the T. asperellum/P. lilacinum consortium, P. lilacinum and P. chlamydosporia. These findings may benefit sustainable agricultural management systems that use fungal isolate treatments to eliminate or reduce the environmental impacts of mineral fertilizers and pesticides.

The Araucaria forest is a sub-type of Atlantic Forest and it is critically endangered because of deforestation. Despite significant researchers’ attention, little is known about the microbial and functional soil diversity of this ecosystem. Our aim was to assess structural diversity (phospholipid fatty acid; PLFA), functional diversity (Biolog ecoplates) and physicochemical soil properties to identify which indicators are the most sensitive to alterations in the Araucaria ecosystems. Soils of three different areas (disturbed, reforested, and native Araucaria forest soils), in two parks of Southeast Brazil, were collected in contrasting seasons (dry and rainy). Principal components analysis (PCA) showed that fatty acid profiles, Biolog and physicochemical properties in Araucaria forest soils were more dissimilar between the different park geographic locations than by forest disturbance levels. However, discriminant analysis identified several variables with greater power to discriminate among forest disturbance levels (native, disturbed, and reforested) within each season. Reforested soils were lower in pH, Al+3, and base cation content compared to disturbed and native soils. Soils disturbed by recreational and understory deforestation were sandier in texture and elevated in P compared to native and deforested soils. Native soil microbial communities utilized certain Biolog substrates to a greater extent, depending on season, compared to communities of disturbed and reforested soils. The best discriminating variable among native, disturbed, and reforested soils for both seasons was γ-hydroxybutyric acid consumption, which was positively related to native, and negatively correlated to disturbed and reforested soils. Thus, γ-hydroxybutyric acid consumption may be a useful indicator to monitor the recovery of reforested and disturbed Araucaria soils in reference to its native state.

Processed organic agricultural byproducts such as liquid organic fertilizer (LOF) are promising alternatives that can improve crop productivity while reducing mineral fertilizer use and improving sustainability. The effects on beneficial soil organisms, such as arbuscular mycorrhizal (AM) fungi and phosphate solubilizing microorganisms (PSM), caused by LOF spraying on shoots is poorly understood. Therefore, we evaluated how AM colonization and soil PSM are affected by LOF spraying on common beans (Phaseolus vulgaris L.) grown in a greenhouse. The LOF was obtained by anaerobically fermenting a mixture of fresh water, cattle manure, bovine milk, sugarcane molasses and mineral salts. LOF was applied twice on the plant shoots. Fresh and dry mass of root and shoot, P content, P accumulation in the shoots and AMF spore counts in the soil were not LOF dose dependent. However, we found that a 5% LOF application stimulated AM colonization and led to dose-dependence for calcium and aluminium phosphate solub...

Plant growth and arbuscular mycorrhizal colonization were studied in sugarcane, corn and soybean by applying five plant growth promoting fungi: Beauveria bassiana, Metarhizium anisopliae, Pochonia chlamydosporia, Purpureocillium lilacinum, and Trichoderma asperella. Sugarcane, corn and soybean were grown in pots under two treatments: (1) inoculation with the fungal consortium and (2) control without inoculation. In the inoculated treatment, fungal spore suspension were applied to the seeds and shoots were sprayed every 28 days. Means were analyzed by analysis of variance and Tukey’s test at 5% probability level. The experiment was arranged in a completely randomized design, with six replications. Fungi consortium mediate root growth in soybean and corn, and arbuscular mycorrhizal colonization in soybean and sugarcane. These findings are probably caused by the fungi producing phytohormones and inducing the plants to synthesize phytohormones: auxins for root growth; and jasmonic, abscisic, and salicylic acids with a role in the regulation of mycorrhizal colonization. These effects are important when seeking conservation strategies in agriculture and livestock production, since Fungi consortium can better mediate soil resource acquisition, promoting greater absorption of nutrients and water.

Arbuscular mycorrhizal fungi (AMF) play an important role in plant community productivity and structure, and so studying the factors that affect the diversity and structure of this fungal community is important for understanding their ecology in tropical forests. We investigated AMF spore communities and root colonization under three forest phytophysiognomies (Restinga Forest, REF; Lowland Ombrophilous Dense Forest, LLF; and Montane Ombrophilous Dense Forest, MTF). Spore abundance was lowest in LLF and highest in REF, with no statistical differences relative to MTF. Spore diversity indices and root colonization rates were not statistically different among the phytophysiognomies. However, principal components analysis revealed that AMF community structure differed according to forest phytophysiognomy. Hierarchical partitioning analysis indicated that most of the AMF community variables were better explained by phytophysiognomy than by chemical and physical attributes of the soil. In addition to the plant community, clay content, pH, Boron, P, S and CEC best explained some of the AMF community variables. Thus, we conclude that while several factors determine AMF community structure in the Atlantic Forest, phytophysiognomy is the most significant.

Statistical approaches, especially multivariate techniques such as hierarchical partitioning analysis (HP) and redundancy analysis (RDA), can be used to select appropriate variables for soil quality assessment. HP is usually applied to ecological data from plants and animals, but has not been applied to chemical and microbial properties such as those used as indicators of soil quality. Our aim was to show how these methods can be employed to find soil quality indicators, using soil microbiological, chemical and physical data to compare two forest types (native and reforested Brazilian Araucaria forests) in two locations in Southeast Brazil. We used RDA to investigate relationships among variables. Additionally, we quantified the independent effects of predictor variables: location, forest type, two specific seasons and some soil properties and used HP to examine how these environmental variables interact to influence soil microbial and chemical attributes. RDA showed that acid phosphatase and dehydrogenase activity, NO2− oxidizer numbers, basal respiration, metabolic quotient, pH, P and sand content were positive and significantly correlated with the native Araucaria forest, whereas arylsulphatase activity, denitrifier numbers, microbial biomass carbon, microbial quotient, TOC, S and clay levels were positively correlated with the reforested Araucaria. These preliminary results suggest that these variables are the best indicators of soil quality for Araucaria forests. However, HP, used as a complementary tool, showed that only dehydrogenase activity, pH and S variations were due more to forest type than to physical and chemical soil properties, and were resistant to the variation in the two seasons. Overall, our results indicated that dehydrogenase activity, pH and S are potential indicators that can be used to assess or monitor soil health in Araucaria forests. In conclusion, we demonstrated the usefulness of HP to find soil quality indicators. Similarly, other statistical methods, as RDA, could complement HP and increase the reliability of studies that consider simultaneous variables in soil science.

Sugarcane (Saccharum spp.) is grown on over 8 million ha in Brazil and is used to produce ethanol and sugar. Some sugarcane fields are burned to facilitate harvesting, which can affect the soil microbial community. However, whether sugarcane pre-harvest burning affects the community of arbuscular mycorrhizal fungi (AMF) and symbioses development is not known. In this study, we investigated the early impacts of harvest management on AMF spore communities and root colonization in three sugarcane varieties, under two harvest management systems (no-burning and pre-harvest burning). Soil and root samples were collected in the field after the first harvest of sugarcane varieties SP813250, SP801842, and RB72454, and AMF species were identified based on spore morphology. Diversity indices were determined based on spore populations and root colonization determined as an indicator of symbioses development. Based on the diversity indices, spore number and species occurrence in soil, no significant differences were observed among the AMF communities, regardless of harvest management type, sugarcane variety or interactions between harvest management type and sugarcane variety. However, mycorrhiza development was stimulated in sugarcane under the no-burning management system. Our data suggest that the sugarcane harvest management system may cause early changes in arbuscular mycorrhiza development.

Considered as one of the most biodiverse biomes, the Amazon has a featured role in the discovery of new species of plants, animals and microorganisms, which may be important for the functionality of different ecosystems. However, studies on the impacts resulted from changes in the Amazon land use on microbial communities and their functions are still limited. In this context, the soil fungal diversity can act as an important indicator of environmental stress caused by land use of the Amazon. This study describes changes in soil fungal communities caused by different systems of land use (primary forest, secondary forest, agroforestry, agriculture and pasture). Communities were observed in each of the areas using denaturing gradient gel electrophoresis (DGGE) of 18S rRNA gene combined with the non-metric multidimensional scaling (NMDS). Unique bands indicated the dominance of particular fungal groups in each of the specific treatments, mainly in areas converted to pasture, which differed greatly from samples of other systems of land use (SLU). The analysis of partial sequence of the 18S rRNA gene of fungi in soils under primary forest, agriculture and pasture showed differences (p = 0.001), evidencing the fungal community response to such changes. Most abundant phyla were the Zygomycota in the soil under primary forest and agricultural land, and Basidiomycota in the soil under pasture. The results show that the Amazon soil is an ecosystem susceptible to environmental changes in regarding the fungi community inhabiting this niche.

It is well-known that Amazon tropical forest soils contain high microbial biodiversity. However, anthropogenic actions of slash and burn, mainly for pasture establishment, induce profound changes in the well-balanced biogeochemical cycles. After a few years the grass yield usually declines, the pasture is abandoned and is transformed into a secondary vegetation called "capoeira" or fallow. The aim of this study was to examine how the clearing of Amazon rainforest for pasture affects: (1) the diversity of the Bacteria domain evaluated by Polymerase Chain Reaction and Denaturing Gradient Gel Electrophoresis (PCR-DGGE), (2) microbial biomass and some soil chemical properties (pH, moisture, P, K, Ca, Mg, Al, H + Al, and BS), and (3) the influence of environmental variables on the genetic structure of bacterial community. In the pasture soil, total carbon (C) was between 30 to 42 % higher than in the fallow, and almost 47 % higher than in the forest soil over a year. The same pattern was observed for N. Microbial biomass in the pasture was about 38 and 26 % higher than at fallow and forest sites, respectively, in the rainy season. DGGE profiling revealed a lower number of bands per area in the dry season, but differences in the structure of bacterial communities among sites were better defined than in the wet season. The bacterial DNA fingerprints in the forest were stronger related to Al content and the Cmic:Ctot and Nmic:Ntot ratios. For pasture and fallow sites, the structure of the Bacteria domain was more associated with pH, sum of bases, moisture, total C and N and the microbial biomass. In general microbial biomass in the soils was influenced by total C and N, which were associated with the Bacteria domain, since the bacterial community is a component and active fraction of the microbial biomass. Results show that the genetic composition of bacterial communities in Amazonian soils changed along the sequence forest-pasture-fallow. Os solos da floresta tropical amazônica supostamente abrigam elevada biodiversidade microbiana. Entretanto, as ações antrópicas de corte e queima, especialmente para o estabelecimento de pastagens, induzem mudanças profundas nos ciclos biogeoquímicos. Após alguns anos de uso, a produtividade da gramínea declina, a pastagem é abandonada, tornando-se uma vegetação secundária, denominada "capoeira" ou pousio. O objetivo deste trabalho foi avaliar como o desmatamento da floresta amazônica para o estabelecimento de pastagem altera: a diversidade do domínio Bacteria avaliada por PCR-DGGE; a biomassa microbiana e alguns atributos químicos do solo (pH, umidade, P, K, Ca, Mg, Al, H + Al e SB); e a influência de variáveis ambientais na estrutura genética de comunidades bacterianas. A pastagem continha entre 30 e 42 % mais carbono total (C) do que a capoeira e aproximadamente 47 % mais C do que a floresta ao longo do ano. O mesmo padrão foi observado para o nitrogênio total (N). A biomassa microbiana na pastagem foi 38 e 26 % maior do que nas áreas de capoeira e floresta, respectivamente, durante a estação chuvosa. O padrão de bandas em DGGE revelou menor número de bandas por área na estação seca, porém as diferenças na estrutura de comunidades bacterianas entre as áreas de estudo foram mais bem definidas do que na estação chuvosa. O perfil de bandas encontrado na floresta esteve mais associado ao teor de Al e às taxas Cmic:Ctot e Nmic:Ntot. Em relação às áreas de pastagem e capoeira, a estrutura do domínio Bacteria esteve mais associada a pH, soma de bases, umidade, C e N totais e à biomassa microbiana. De modo geral, a biomassa microbiana em solos é influenciada pelos teores de C e N totais, os quais estiveram associados ao domínio Bacteria, visto que a comunidade bacteriana é uma fração componente e ativa da biomassa microbiana. Os resultados indicam que a composição genética das comunidades microbianas dos solos da Amazônia mudou ao longo da sequência floresta-pastagem-capoeira.

Preharvest burning is widely used in Brazil for sugarcane cropping. However, due to environmental restrictions, harvest without burning is becoming the predominant option. Consequently, changes in the microbial community are expected from crop residue accumulation on the soil surface, as well as alterations in soil metabolic diversity as of the first harvest. Because biological properties respond quickly and can be used to monitor environmental changes, we evaluated soil metabolic diversity and bacterial community structure after the first harvest under sugarcane management without burning compared to management with preharvest burning. Soil samples were collected under three sugarcane varieties (SP813250, SP801842 and RB72454) and two harvest management systems (without and with preharvest burning). Microbial biomass C (MBC), carbon (C) substrate utilization profiles, bacterial community structure (based on profiles of 16S rRNA gene amplicons), and soil chemical properties were determined. MBC was not different among the treatments. C-substrate utilization and metabolic diversity were lower in soil without burning, except for the evenness index of C-substrate utilization. Soil samples under the variety SP801842 showed the greatest changes in substrate utilization and metabolic diversity, but showed no differences in bacterial community structure, regardless of the harvest management system. In conclusion, combined analysis of soil chemical and microbiological data can detect early changes in microbial metabolic capacity and diversity, with lower values in management without burning. However, after the first harvest, there were no changes in the soil bacterial community structure detected by PCR-DGGE under the sugarcane variety SP801842. Therefore, the metabolic profile is a more sensitive indicator of early changes in the soil microbial community caused by the harvest management system. A queima da cana-de-açúcar previamente à colheita é amplamente utilizada no Brasil. Entretanto, em razão das restrições ambientais, a colheita sem queima vem ganhando espaço. Consequentemente, espera-se que o acúmulo de resíduos da cultura na superfície do solo altere a comunidade microbiana, iniciando mudanças na diversidade metabólica do solo desde a primeira colheita. Uma vez que os atributos biológicos respondem rapidamente e podem ser úteis para o monitoramento de mudanças ambientais, o objetivo deste trabalho foi avaliar as mudanças iniciais na diversidade metabólica do solo e na estrutura da comunidade bacteriana com a eliminação da queima, quando comparada ao manejo com queima prévia à colheita da cana-de-açúcar. Amostras de solo foram coletadas sob as variedades de cana-de-açúcar SP813250, SP801842 e RB72454, colhidas sem a queima e com queima prévia. O carbono da biomassa microbiana (MBC), os perfis de utilização de substratos de C, a estrutura da comunidade bacteriana com base nos perfis de amplicos do gene 16S rRNA e as propriedades químicas do solo foram determinados. O MBC não se diferenciou entre os tratamentos. A utilização de substratos de C e a diversidade metabólica foram menores no solo sem queima, exceto para o índice de equitabilidade de uso dos substratos. As amostras de solo sob a variedade SP801842 apresentaram as maiores mudanças na utilização de substratos e na diversidade metabólica, mas não diferiram na estrutura da comunidade bacteriana, independentemente do sistema de manejo de colheita. Em conclusão, a análise conjunta de dados químicos e microbiológicos do solo permite detectar alterações iniciais na capacidade e diversidade metabólica microbiana, com menores valores no manejo sem queima. Entretanto, após a primeira colheita, não houve mudanças na estrutura da comunidade bacteriana do solo detectada por PCR-DGGE sob a variedade SP801842. Portanto, o perfil metabólico é o indicador mais sensível para mudanças iniciais na comunidade microbiana do solo, causadas pelo sistema de manejo de colheita.

As micorrizas arbusculares (MAs) são associações simbióticas mutualistas entre fungos do filo Glomeromycota e a maioria das plantas terrestres. A formação e o funcionamento das MAs depende de um complexo processo de troca de sinais, que resulta em mudanças no metabolismo dos simbiontes e na diferenciação de uma interface simbiótica no interior das células das raízes. Os mecanismos que regulam a formação das MAs são pouco conhecidos, mas sabe-se que a concentração de fosfato (P) na planta é um fator determinante para o desenvolvimento da simbiose. A disponibilidade de P na planta pode afetar o balanço de açúcares e de fitormônios (FHs), além da expressão de genes de defesa vegetal. Com o advento da genômica e proteômica, vários genes essenciais para o desenvolvimento das MAs já foram identificados e seus mecanismos de regulação estão sendo estudados. Até o presente, sabe-se que as plantas secretam substâncias que estimulam a germinação de esporos e o crescimento de fungos micorrízicos arbusculares (FMAs). Há evidências também de que os FMAs sintetizam moléculas sinalizadoras, que são reconhecidas pelas plantas hospedeiras. Pelo menos três genes são essenciais para o reconhecimento dessa molécula e a transdução do sinal molecular. Discutem-se os papéis desses genes e os possíveis mecanismos que regulam sua expressão, bem como os papéis dos FHs na regulação de MAs são discutidos.