Arbuscular mycorrhizal fungal communities in the rhizosphere of a continuous cropping soybean system at the seedling stage

Abstract Arbuscular mycorrhizae (AM) fungi play a crucial role in the growth of soybean; however, the planting system employed is thought to have an effect on AM fungal communities in the rhizosphere. This study was performed to explore the influence of continuous soybean cropping on the diversity of Arbuscular mycorrhizal (AM) fungi, and to identify the dominant AM fungus during the seedling stage. Three soybean cultivars were planted under two and three years continuous cropping, respectively. The diversity of AM fungi in the rhizosphere soil at the seedling stage was subsequently analyzed using polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). The results showed that an increase in cropping years improved the colonization rate of AM in all three soybean cultivars. Moreover, the dominant species were found to be Funneliformis mosseae and Glomus species. The results of cluster analysis further confirmed that the number of years of continuous cropping significantly affected the composition of rhizospheric AM fungal communities in different soybean cultivars.

Physiological response of Cucurbita pepo var. pepo mycorrhized by Sonoran desert native arbuscular fungi to drought and salinity stresses

ABSTRACT Plants response to symbiosis with arbuscular mycorrhizal fungi (AMF) under water stress is important to agriculture. Under abiotic stress conditions native fungi are more effective than exotics in improving plant growth and water status. Mycorrhization efficiency is related to soil fungi development and energy cost-benefit ratio. In this study, we assessed the effect on growth, water status and energy metabolism of Cucurbita pepo var. pepo when inoculated with native AMF from the Sonoran desert Mexico (mixed isolate and field consortium), and compared with an exotic species from a temperate region, under drought, low and high salinity conditions. Dry weights, leaf water content, water and osmotic potentials, construction costs, photochemistry and mycorrhization features were quantified. Under drought and low salinity conditions, the mixed isolate increased plant growth and leaf water content. Leaf water potential was increased only by the field consortium under drought conditions (0.5-0.9 MPa). Under high salinity, the field consortium increased aerial dry weight (more than 1 g) and osmotic potential (0.54 MPa), as compared to non-mycorrhized controls. Plants inoculated with native AMF, which supposedly diminish the effects of stress, exhibited low construction costs, increased photochemical capacity, and grew larger external mycelia in comparison to the exotic inoculum.

Tripartite symbiosis of Sophora tomentosa, rhizobia and arbuscular mycorhizal fungi

ABSTRACT Sophora tomentosa is a pantropical legume species with potential for recovery of areas degraded by salinization, and for stabilization of sand dunes. However, few studies on this species have been carried out, and none regarding its symbiotic relationship with beneficial soil microorganisms. Therefore, this study aimed to evaluate the diversity of nitrogen-fixing bacteria isolated from nodules of Sophora tomentosa, and to analyze the occurrence of colonization of arbuscular mycorrhizal fungi on the roots of this legume in seafront soil. Thus, seeds, root nodules, and soil from the rhizosphere of Sophora tomentosa were collected. From the soil samples, trap cultures with this species were established to extract spores and to evaluate arbuscular mycorhizal fungi colonization in legume roots, as well as to capture rhizobia. Rhizobia strains were isolated from nodules collected in the field or from the trap cultures. Representative isolates of the groups obtained in the similarity dendrogram, based on phenotypic characteristics, had their 16S rRNA genes sequenced. The legume species showed nodules with indeterminate growth, and reddish color, distributed throughout the root. Fifty-one strains of these nodules were isolated, of which 21 were classified in the genus Bacillus, Brevibacillus, Paenibacillus, Rhizobium and especially Sinorhizobium. Strains closely related to Sinorhizobium adhaerens were the predominant bacteria in nodules. The other genera found, with the exception of Rhizobium, are probably endophytic bacteria in the nodules. Arbuscular mycorrhizal fungi was observed colonizing the roots, but arbuscular mycorhizal fungi spores were not found in the trap cultures. Therefore Sophora tomentosa is associated with both arbuscular mycorhizal fungi and nodulating nitrogen-fixing bacteria.

Occurrence of arbuscular mycorrhizal fungi on King George Island, South Shetland Islands, Antarctica

ABSTRACT Arbuscular mycorrhizal fungi make up an important ecological niche in ecosystems, and knowledge of their diversity in extreme environments is still incipient. The objective of this work was to evaluate the density and diversity of arbuscular mycorrhizal fungi in the soil of King George Island in the South Shetland Islands archipelago, Antarctica. For that, soil and roots of Deschampsia antarctica were collected at the brazilian research station in Antarctica. The spore density, species diversity and mycorrhizal colonization in the roots were evaluated. There was a low density of spores (27.4 ± 17.7) and root mycorrhizal colonization (6 ± 5.1%), which did not present statistical difference. Four species of arbuscular mycorrhizal fungi were identified, distributed in two genera: three species of the genus Glomus (Glomus sp1, Glomus sp2 and Glomus sp3) and one of the genus Acaulospora, which was identified at species level (Acaulospora mellea). Greater soil diversity was verified with pH 5.9 and phosphorus concentration of 111 mg dm-3, occurring two species of genus Glomus and A. mellea. Based on literature data, this may be the first record of this species of Acaulospora mellea in Antarctic soils, colonizing D. antarctica plants.

Enrichment of arbuscular mycorrhizal fungi in a contaminated soil after rehabilitation

Abstract Spore counts, species composition and richness of arbuscular mycorrhizal fungi, and soil glomalin contents were evaluated in a soil contaminated with Zn, Cu, Cd and Pb after rehabilitation by partial replacement of the contaminated soil with non-contaminated soil, and by Eucalyptus camaldulensis planting with and without Brachiaria decumbens sowing. These rehabilitation procedures were compared with soils from contaminated non-rehabilitated area and non-contaminated adjacent soils. Arbuscular mycorrhizal fungi communities attributes were assessed by direct field sampling, trap culture technique, and by glomalin contents estimate. Arbuscular mycorrhizal fungi was markedly favored by rehabilitation, and a total of 15 arbuscular mycorrhizal fungi morphotypes were detected in the studied area. Species from the Glomus and Acaulospora genera were the most common mycorrhizal fungi. Number of spores was increased by as much as 300-fold, and species richness almost doubled in areas rehabilitated by planting Eucalyptus in rows and sowing B. decumbens in inter-rows. Contents of heavy metals in the soil were negatively correlated with both species richness and glomalin contents. Introduction of B. decumbens together with Eucalyptus causes enrichment of arbuscular mycorrhizal fungi species and a more balanced community of arbuscular mycorrhizal fungi spores in contaminated soil.

Arbuscular mycorrhizal fungi in Mimosa tenuiflora (Willd. ) Poir from Brazilian semi-arid

Abstract Many plant species from Brazilian semi-arid present arbuscular mycorrhizal fungi (AMF) in their rhizosphere. These microorganisms play a key role in the establishment, growth, survival of plants and protection against drought, pathogenic fungi and nematodes. This study presents a quantitative analysis of the AMF species associated with Mimosa tenuiflora, an important native plant of the Caatinga flora. AMF diversity, spore abundance and root colonization were estimated in seven sampling locations in the Ceará and Paraíba States, during September of 2012. There were significant differences in soil properties, spore abundance, percentage of root colonization, and AMF diversity among sites. Altogether, 18 AMF species were identified, and spores of the genera Acaulospora, Claroideoglomus, Dentiscutata, Entrophospora, Funneliformis, Gigaspora, Glomus, Racocetra, Rhizoglomus and Scutellospora were observed. AMF species diversity and their spore abundance found in M. tenuiflora rhizosphere shown that this native plant species is an important host plant to AMF communities from Brazilian semi-arid region. We concluded that: (a) during the dry period and in semi-arid conditions, there is a high spore production in M. tenuiflora root zone; and (b) soil properties, as soil pH and available phosphorous, affect AMF species diversity, thus constituting key factors for the similarity/dissimilarity of AMF communities in the M. tenuiflora root zone among sites.

Morphotype-based characterization of arbuscular mycorrhizal fungal communities in a restored tropical dry forest, Margarita island-Venezuela / Caracterización basada en morfotipos de las comunidades de hongos micorrízicos arbusculares en un bosque seco tropical restaurado, Isla de Margarita-Venezuela

The mycorrhizal component of revegetated areas after ecological restoration or rehabilitation in arid and semiarid tropical areas has been scarcely assessed, particularly those made after mining disturbance. We evaluated and compared the presence of arbuscular mycorrhizal fungi of a small area of restored tropical dry for est destroyed by sand extraction, with a non-restored area of similar age, at the peninsula of Macanao, Margarita Island (Venezuela). Our study was undertaken in 2009, four years after planting, and the mycorrhizal status was evaluated in four restored plots (8 x 12.5 m) (two were previously treated with hydrogel (R2 and R2'), and two were left untreated (R1 and R1'), and four non-restored plots of similar size (NR1 and NR1' with graminoid physiognomy with some scattered shrubs; and NR2 and NR2', with a more species rich plant community). Apparently the restoration management promoted higher arbuscular mycorrhizal fungi (AMF) species richness and diversity, particularly in restored soils where the hydrogel was added (R2 treatment). Soil of the NR1 treat ment (with a higher herbaceous component) showed the highest spore density, compared to samples of soils under the other treatments. Considering species composition, Claroideoglomus etunicatumand Rhizophagus intraradiceswere found in all treatments; besides, Diversispora spurcaand Funneliformis geosporumwere only found in non-restored plots, while members of the Gigasporaceae (a family associated with little disturbed sites) were commonly observed in the plots with restored soils. Mycorrhizal colonization was similar in the restored and non-restored areas, being a less sensitive indicator of the ecosystem recovery. The trend of higher richness and diversity of AMF in the restored plot with hydrogel suggests that this management strategy contributes to accelerate the natural regeneration in those ecosystems where water plays an essential role.

Pocos estudios han evaluado el estado mico-rrízico de áreas tropicales áridas y semi-áridas sujetas a restauración o rehabilitación, en particular después de actividades de minería. Evaluamos y comparamos la presencia de hongos micorrízicos arbusculares en una pequeña área de un bosque seco restaurado que había sido destruido por la extracción de arena, con un área no res taurada de edad similar en la península de Macanao, Isla de Margarita (Venezuela). En Mayo 2005 fueron plantadas cinco especies de árboles nativos (Tecoma stans, Bulnesia arborea, Piscidia carthagenensis, Prosopis julifloraand Parkinsonia praecox)en las áreas deforestadas, con la aplicación de hidrogel como tratamiento más exitoso en términos de sobrevivencia y crecimiento de las plantas. En el presente estudio fue evaluado el estatus micorrízico de cuatro parcelas restauradas (8 x 12.5 m) y cuatro par celas no restauradas de edad similar. Dos de las parcelas restauradas habían sido tratadas previamente con hidrogel (R2 y R2') y a las otras dos no se les agregó hidrogel (R1 y R1'). Las parcelas no restauradas (NR1 y NR1') tenían una fisonomía graminoide con algunos arbustos dispersos, mientras que las otras dos parcelas (NR2 y NR2') mostra ron una comunidad de plantas más diversa. Los resultados indican que aparentemente la restauración promueve una mayor riqueza y diversidad de hongos micorrízicos arbus culares (HMA), particularmente en los suelos restaurados donde fue empleado un hidrogel (tratamiento R2). El suelo del tratamiento NR1 (con un alto componente herbáceo) presentó la mayor densidad de esporas comparado con los suelos de los otros tres tratamientos, lo cual es consistente con los resultados de otros estudios donde las condiciones ambientales estresantes (alta temperatura e intensidad lumínica) promueven una mayor esporulación de HMA. La composición de especies de HMA difirió entre suelos no restaurados y restaurados. Clareidoglomus etunicatumy Rhizophagus intraradicesfueron encontrados en todos los tratamientos, Diversispora spurcay Funneliformis geosporumfueron encontrados sólo en las parcelas no restauradas, mientras que especies pertenecientes a la familia Gigasporaceae, una familia que está asociada con sitios poco alterados, fue observada en mayor proporción en los suelos de las parcelas restauradas. La colonización micorrízica fue similar en las áreas restauradas y no restau radas, y es un indicador menos sensible de la recuperación del ecosistema. La mayor riqueza y diversidad de los HMA en las parcelas restauradas con el hidrogel, sugiere que esta estrategia de manejo podría contribuir con la aceleración de la regeneración natural en un ecosistema donde el agua juega un papel esencial.

Mycorrhizal fungi isolated from native terrestrial orchids of pristine regions in Córdoba (Argentina) / Hongos micorrízicos aislados de orquídeas terrestres nativas de regiones pristinas en Córdoba (Argentina)

Orchidaceae is a highly dependent group on the Rhizoctonia complex that includes Ceratorhiza, Moniliopsis, Epulorhiza and Rhizoctonia, for seed germination and the development of new orchid plants. Thus, the isolation and identification of orchid mycorrhizal fungi are important to understand the orchid-fungus relationship, which can lead to the development of efficient conservation strategies by in vivo germination of seeds from endangered orchid plants. The aim of our work was to isolate and characterize the different mycorrhizal fungi found in roots of terrestrial orchids from Córdoba (Argentina), and, to learn about the natural habit and fungal associations in the Chaco Serrano woodland pristine region. In this study, bloomed orchid root and rhizosphere soil samples were obtained in two times from Valle de Punilla during spring of 2007; samples were kept in plastic bags until processed within 48 hours, and mycorrhizal condition confirmed assessing peloton presence. A total of 23 isolates of the orchideous mycorrhizal Rhizoctonia complex were obtained. The isolates were studied based on morphological characters and ITS-rDNA sequences. Morphological characteristics as color of colonies, texture, growth rate, hyphal diameter and length and presence of sclerotia were observed on culture media. To define the number of nuclei per cell, the isolates were grown in Petri dishes containing water-agar (WA) for three days at 25°C and stained with Safranine-O solution. The mycorrhizal fungi were grouped into binucleate (MSGib, 10 isolates) and multinucleate (MSGim, 13 isolates) based on morphological characteristics of the colonies. We obtained the ITS1-5.8s-ITS4 region that was amplified using primers ITS1 and ITS4. Based on DNA sequencing, isolates Q23 and Q29 were found to be related to species of Ceratobasidium. Isolates Q24 and Q4 were related to the binucleated anastomosis group AG-C of Rhizoctonia sp. The rest of the isolates grouped in the Ceratobasidium clade without grouping. From our knowledge this is the first report of the association of the AG-C testers with terrestrial orchids. A high specificity was observed in the symbiotic relationship. As the mycorrhizal fungal isolates were obtained from native orchids, they could be incorporated in conservation programes of endangered orchids in Argentina.

La Familia Orchidaceae se encuentra estrechamente relacionada con hongos micorrízicos que pertenecen al complejo Rhizoctonia, e incluyen los géneros Ceratorhiza, Moniliopsis, Epulorhiza y Rhizoctonia. Esta asociación es esencial para el desarrollo de nuevas plantas ya que favorecen el proceso de germinación de las semillas. Por lo tanto, el conocimiento de la naturaleza de esta interacción es importante para que los resultados de los programas de conservación de orquídeas sean efectivos. La fragmentación del bosque Chaqueño Serrano en el centro de Argentina, ha alcanzado un punto crítico en los últimos años, afectando el funcionamiento del ecosistema. El objetivo de este trabajo fue: a) aislar y caracterizar hongos micorrízicos presentes en orquídeas terrestres de la provincia de Córdoba (Argentina) y b) conocer el hábitat natural y las asociaciones fúngicas que se establecen en esta región prístina. A partir de las raíces de orquídeas terrestres, se obtuvieron 23 aislamientos de hongos micorrízicos que pertenecen al complejo Rhizoctonia. Estos aislamientos fueron caracterizados con base en caracteres morfológicos y moleculares. Las características morfológicas (color y textura de las colonias, cinética de crecimiento, diámetro y largo de la hifa y presencia de esclerocios) fueron observados en PDA y MEA a 25ºC. El número de núcleos por célula se observó en cultivos crecidos en AA (agar-agua) y teñidos con una solución de Safranine-O. La región ITS se amplificó usando los primers ITS1 e ITS4. Con base en las características morfológicas de la colonia, los aislamientos fueron agrupados en binucleados (MSGib) y multinucleados (MSGim). De acuerdo al cladograma obtenido con las secuencias de ADN, los aislamientos Q23 y Q29 están relacionados a especies de Ceratobasidium, aisladas de raíces de orquídeas. Los aislamientos Q24 y Q4 se asocian con el grupo de anastomosis de Rhizoctonia AG-C. Finalmente, se observó una alta variabilidad en el grado de especificidad existente en la simbiosis que se establece entre las raíces de estas orquídeas terrestres y los aislamientos obtenidos a partir de ellas. Este es el primer reporte de la asociación entre el grupo de anastomosis AG-C y orquídeas terrestres. Dado que estos aislamientos se obtuvieron de orquídeas terrestres nativas, podrían ser incorporados como nuevos patrones para micorrizas de orquídeas terrestres en Argentina. Este trabajo contribuye al conocimiento de la relación simbiótica que se establece entre orquídeas y hongos micorrízicos, así como también al desarrollo de estrategias de conservación de orquídeas terrestres nativas del bosque Chaco Serrano.

Colonización y estructura de la comunidad de hongos micorrízicos arbusculares en Alsophila firma (Cyatheaceae) en bosque mesófilo de montaña en Veracruz, México / Colonization and structure of arbuscular mycorrhizal fungi community in Alsophila firma (Cyatheales: Cyatheaceae) from a tropical montane cloud forest in Veracruz, México

Alsophila firma is a tree fern that is distributed mainly in tropical montane cloud forest (TMCF) and is considered as a threatened species. Arbuscular mycorrrhizal fungi (AMF) have been proposed as an alternative in rescue programs of endangered species. However, our knowledge about diversity of AMF and mycorrhizal status of the species of TMCF is limited. In Mexico TMCF shows different degrees of conservation because of fragmentation and land use change. In this study, we evaluated the level of colonization, richness and abundances of spores of AMF in three fragments with different conservation status: conserved (100 years), secondary vegetation (17 years) and disturbed. For this, soil samples and roots were collected from five individuals of A. firma per site, with at least 100m away from each other; a total of 100cm of roots were analysed per site. Root samples showed AMF and occasionally dark septate fungi (DSF) colonizations. For the overall study, 19 species of AMF were recorded: Gigaspora (7), Acaulospora (4), Glomus (4), Funneliformis (2), Sclerocystis (1) and Scutellospora (1). The dominant species in the three sites were Funneliformis geosporum and Acaulospora scrobiculata. The highest diversity (H’) and evenness (J’) (p<0.05) were found in the conserved site (H’=1.7, J’=0.66), when compared to the secondary vegetation (H’=1.5, J’=0.61), and the disturbed site (H’=0.74, J’=0.41). Statistical analysis showed that the AMF degree of colonization was significantly higher (p<0.05) in the conserved site; although, the disturbed site showed low richness and abundances of AMF, the degree of root colonization did not differ statistically (p<0.05) with the secondary vegetation site. Chao2 (Richness estimation model) showed that the number of analysed samples were sufficient to represent the structure of the AMF communities with values >90%. The present study confirmed that A. firma is a mycorrhizal species that exhibits high levels of colonization even in disturbed sites. We suggest that F. geosporum and A. scrobiculata may have the potential to inoculate the gametophyte and young sporophyte of A. firma, to support restoration programs, because of their abundances and high tolerance to disturbed sites.

Alsophila firma es un helecho arborescente que crece principalmente en bosque mesófilo de montaña (BMM) y se encuentra en la categoría de riesgo. Los hongos mico- rrízicos arbusculares (HMA) se han propuesto como una alternativa para programas de recuperación de especies nativas en peligro. Sin embargo, sabemos poco sobre la diversidad de HMA y del estatus micorrízico de las espe- cies vegetales del BMM. En México el BMM presenta diferentes grados de conservación debido a la fragmentación y el cambio de uso de suelo. Se evaluó el grado de colonización, riqueza y abundancia de esporas de los HMA presentes en fragmentos de BMM con diferente historia de manejo: conservado (100 años), en recuperación (17 años) y alterado. Se estudiaron muestras de suelo y raíces toma- das de 5 individuos de A. firma por cada sitio, con al menos 100m de distancia entre individuos. Se analizaron en total 100cm de raíz por cada sitio. Las muestras de raíz presentaron colonización principalmente de HMA y ocasionalmente por hongos septados oscuros (HSO). Se encontraron 19 especies: Gigaspora (7), Acaulospora (4), Glomus (4), Funneliformis (2), Sclerocystis (1) y Scutellospora (1). Las especies dominantes en los tres sitios fueron Funneliformis geosporum y Acaulospora scrobiculata. La mayor diversidad (H’) y equitatividad (J’) (p<0.05) se presentaron en el sitio conservado (H’=1.7; J’ 0.66) con respecto al sitio en recuperación (H’=1.5, J’ 0.61) y alterado (H’=0.74, J’=0.41). Los niveles de colonización micorrízica total de raíz fueron estadísticamente mayores (p<0.05) en el sitio conservado. Aunque el sitio alterado presenta una baja riqueza y abundancia de HMA la colonización micorrízica total de raíz no fue estadísticamente diferente (p<0.05) respecto al sitio en recuperación. El estimador Chao2 indica que las muestras analizadas reflejan la estructura general de la comunidad de HMA con valores superiores al 93%. El presente estudio confirma que A. firma es una especie micorrízica con altos niveles de colonización incluso en sitios alterados. Se sugiere que las especies F. geosporum y A. scrobiculata por su alta tolerancia a sitios alterados pueden tener potencial para inocular gametofitos y esporofitos de A. firma para incrementar la supervivencia en programas de restauración.

Early changes in arbuscular mycorrhiza development in sugarcane under two harvest management systems

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.

Arbuscular mycorrhizal fungi in saline soils: vertical distribution at different soil depth

Arbuscular mycorrhizal fungi (AMF) colonize land plants in every ecosystem, even extreme conditions such as saline soils. In the present work we report for the first time the mycorrhizal status and the vertical fungal distribution of AMF spores present in the rhizospheric soil samples of four species of Chenopodiaceae (Allenrolfea patagonica, Atriplex argentina, Heterostachys ritteriana and Suaeda divaricata) at five different depths in two saline of central Argentina. Roots showed medium, low or no colonization (0-50%). Nineteen morphologically distinctive AMF species were recovered. The number of AMF spores ranged between 3 and 1162 per 100 g dry soil, and AMF spore number decreased as depth increased at both sites. The highest spore number was recorded in the upper soil depth (0-10 cm) and in S. divaricata. Depending of the host plant, some AMF species sporulated mainly in the deep soil layers (Glomus magnicaule in Allenrolfea patagonica, Septoglomus aff. constrictum in Atriplex argentina), others mainly in the top layers (G. brohultti in Atriplex argentina and Septoglomus aff. constrictum in Allenrolfea patagonica). Although the low percentages of colonization or lack of it, our results show a moderate diversity of AMF associated to the species of Chenopodiaceae investigated in this study. The taxonomical diversity reveals that AMF are adapted to extreme environmental conditions from saline soils of central Argentina.

Fungos micorrízicos arbusculares, biomassa e atividade microbiana de solo sob banana, braquiária e degradado / Abuscular mycorrhizal fungi, microbial soil biomass and activity under banana, brachiaria and degraded soil / Hongos micorrízicos arbusculares, actividad y biomasa microbiana en suelo cultivado con banana, brachiaria y degradado

O uso e manejo adequado do solo podem ser medidos por meio de bio-indicadores de qualidade do solo. Os objetivos deste trabalho foram determinar a densidade de esporos de fungos micorrízicos arbusculares (FMAs), carbono da biomassa microbiana do solo (C-BMS), respiração basal do solo (RBS) e quociente metabólico (qCO2) de áreas com cultivo orgânico com banana e com braquiária sem pastejo, comparativamente com uma área próxima degradada com palmeiras imperiais em Umuarama, PR. O solo foi coletado na profundidade de 0-10 cm com 4 repetições em cada área e analisadas em duplicata no laboratório. Os resultados foram submetidos à análise de variância (ANOVA) e teste de Tukey (p ? 0,05), usando o programa SPSS v.16. A densidade de esporos de FMAs foi significantemente menor na área degrada. O C-BMS foi significantemente maior na área com braquiária, comparativamente com o solo cultivado com banana e degradado. Na área com banana o C-BMS foi maior que na área degradada. A análise química do solo revelou na área degradada apresentou baixo teor de fósforo, carbono, cálcio e potássio, o que pode ter contribuído para o baixo C-BMS, devido ao estresse elevado neste solo. Não houve diferença significativa na RBS entre as áreas, mas o qCO2 foi significantemente maior no solo degradado, indicando novamente um nível de estresse elevado neste solo. Manejo e uso adequado do solo como o cultivo orgânico de bananas e/ou braquiária aumentou a densidade de esporos de FMAs e C-BMS, além disso, diminuiu o qCO2 comparado com a área degradada.(AU)

The sustainable use and management of soil can be measured using soil quality bioindicators. The objectives of this study were to determine arbuscular mycorrhizal fungi (AMF) spore density, carbon in soil microbial biomass (MB-C), soil basal respiration (SBR) and metabolic quotient (qCO2) in different areas under organic cultivation of banana and brachiaria without grazing compared to nearby degraded area growing imperial palms in the city of Umuarama, in the state of Parana. Soil samples were collected at 0-10 cm depth with four repetitions in each area and analyzed in duplicate. All the results were submitted to the analysis of variance (ANOVA) and Tukey?s test (p ? 0.05), utilizing the statistical program SPSS, version 16.0 for Windows. The results showed that AMF spore density was significantly lower in the degraded area. MB-C was significantly higher in the area cultivated with brachiaria in comparison with banana and degraded areas. However, in the banana area, the MB-C was higher than that in the degraded area. Soil chemical analysis showed that the degraded area had low soil phosphorus, carbon, calcium and potassium content, which could have contributed to the decrease in MB-C, due to a high stress condition in this soil. No significant differences were found for SBR among the analyzed areas. However, qCO2 increased significantly in the degraded area, indicating high stress under this condition. Soil use and management under organic cultivation with banana and/or brachiaria increased AMF spore density and MB-C, as well as decreasing qCO2 when compared to the degraded area.(AU)

El uso y manejo adecuado del suelo pueden ser medidos mediante indicadores biológicos de calidad del suelo. Los objetivos de este estudio fueron determinar la densidad de esporas de hongos micorrízicos arbusculares (HMA), carbono de la biomasa microbiana del suelo (C-BMS), respiración basal del suelo (RBS) y cociente metabólico (qCO2) en áreas con cultivo orgánico de banana, brachiaria sin pastoreo, comparativamente con una zona cercana degradada con palmeras imperiales en Umuarama, PR. Se ha recogido suelo a una profundidad de 0-10 cm con 4 repeticiones en cada área y analizados por duplicado en el laboratorio. Los resultados han sido sometidos a análisis de varianza (ANOVA) y la prueba de Tukey (p ? 0,05), utilizando el programa SPSS v.16. La densidad de esporas de HMA fue significativamente menor en el área degradada. El C-BMS fue significativamente mayor en el área con brachiaria en comparación con el suelo cultivado con banana y degradado. En el área con banana C-BMS fue mayor que en el área degradada. El análisis químico del suelo reveló en el área degradada bajo tenor en fósforo, carbono, calcio y potasio, lo que puede haber contribuido a la baja C-BMS, debido al estrés elevado en el suelo. No hubo diferencia significativa en RBS entre las áreas, pero el qCO2 fue significativamente mayor en el suelo degradado, indicando nuevamente alto nivel de estrés en ese suelo. Manejo y uso adecuado del suelo como el cultivo de bananas y/o brachiaria aumentaron la densidad de esporas de HMAs y C-BMS, además disminuyó el qCO2 en comparación con el área degradada.(AU)

Molecular approach to characterize ectomycorrhizae fungi from Mediterranean pine stands in Portugal

Stone pine (Pinus pinea L.), like other conifers, forms ectomycorrhizas (ECM), which have beneficial impact on plant growth in natural environments and forest ecosystems. An in vitro co-culture of stone pine microshoots with pure mycelia of isolated ECM sporocarps was used to overcome the root growth cessation not only in vitro but also to improve root development during acclimation phase. Pisolithus arhizus (Scop.) Rauschert and Lactarius deliciosus (L. ex Fr.) S.F. Gray fungi, were collected, pure cultured and used in in vitro co-culture with stone pine microshoots. Samples of P. arhizus and L. deliciosus for the in vitro co-cultures were collected from the pine stands southwest Portugal. The in situ characterization was based on their morphotypes. To confirm the identity of the collected material, ITS amplification was applied using the pure cultures derived from the sporocarps. Additionally, a molecular profile using PCR based genomic fingerprinting comparison was executed with other genera of Basidiomycetes and Ascomycetes. Our results showed the effectiveness of the techniques used to amplify DNA polymorphic sequences, which enhances the ­characte­rization of the genetic profile of ECM fungi and also provides an option to verify the fungus identity at any stage of plant mycorrhization.

Microflora cultivable y endomicorrizas obtenida en hojarasca de bosqueParamo Guerrero Finca Puente de Tierra) Zipaquirá, Colombia / Cultivable Microflora and Endomycorrhizas Obtained in Litter Forest (Paramo Guerrero Finca Puente de Tierra) Zipaquirá, Colombia

Se realizó el recuento de microorganismos cultivables (bacterias y hongos), microorganismos celulolíticos y endomicorrizas presentes en la hojarasca de bosque (finca Puente de Tierra) en el páramo Guerrero, Colombia. Los microorganismos aislados con mayor frecuencia pertenecían a los géneros Staphylococcus, Bacillus, Pseudomonas, Micrococcus, Penicillium, Rhodotorula y se aisló una cepa de Cladosporium sp. en un medio selectivo con carboximetil celulosa. Así mismo, se encontraron ocho morfotipos de endomicorrizas, entre los cuales predominaron especies de Glomus y Acaulospora. Este estudio contribuye con el conocimiento de la microbiota cultivable de hojarasca, que ha sido poco explorada en ecosistemas de páramo.

Communities of P-solubilizing bacteria, fungi and arbuscular mycorrhizal fungi in grass pasture and secondary forest of Paraty, RJ - Brazil

Avaliaram-se as comunidades de bactérias, fungos solubilizadores de fosfato e fungos micorrízicos arbusculares em dois diferentes ecossistemas. Foram feitas amostragens em duas áreas de Mata Atlântica, em Paraty - RJ, Brasil, uma de floresta secundária e outra de pastagem. Foram avaliados quatro meios de cultura: GL (glicose e extrato de levedura), GES (glicose, extrato de solo, KNO3, CaCl2, MgSO4, NaCl, FeEDTA solução de micronutrientes), GAGES (glicose, extrato de solo, arabinose, glicerol, CaCl2, MgSO4 e NaCl) e GELP (glicose, extrato de solo, extrato de levedura, peptona, CaCl2, MgSO4 e NaCl) para isolamento de microrganismos solubilizadores de fosfato. A identificação das bactérias solubilizadoras foi baseada na análise do 16 S rDNA, enquanto que os fungos solubilizadores e os micorrízicos arbusculares foram identificados pela sua morfologia. O maior número de bactérias solubilizadoras foi obtido usando os meios GL e GELP. O maior número de fungos solubilizadores foi obtido com os meios GAGES e GES. As bactérias solubilizadoras foram identificadas como Enterobacteriaceae e Bacillus sp., e os fungos como Aspergillus sp. Glomus macrocarpum e Glomus etunicatum foram as espécies de fungos micorrízicos dominantes nas áreas de floresta secundária e pastagem, respectivamente.

Interacción micorrizas arbusculares-Trichoderma harzianum (Moniliaceae) y efectos sobre el crecimiento de Brachiaria decumbens (Poaceae) / Arbuscular Mycorrhizae-Trichoderma harzianum (Moniliaceae) Interaction and Effects on Brachiaria decumbens (Poaceae)’s Growth

Se efectuó un ensayo en condiciones controladas utilizando hongos formadores de micorrizas arbusculares (HFMA) nativos, provenientes de un suelo rizosférico de Pennisetum clandestinum de la Universidad Nacional de Colombia (Bogotá), manteniéndolos en plantas de Brachiaria decumbens creciendo sobre sustrato arenoso suplementado con solución nutritiva. Se evaluaron diferentes tratamientos: plantas con inóculo de HFMA, plantas con Trichoderma harzianum, plantas con HFMA+T. harzianum y plantas control no inoculadas, con el fin de determinar las posibles interacciones entre dichos microorganismos, así como su efecto sobre el crecimiento de B. decumbens. La presencia de T. harzianum disminuyó la colonización radicular por HFMA, aunque no afectó la cantidad de esporas de HFMA/g suelo seco, en tanto que la población de T. harzianum (UFC/g suelo seco) disminuyó significativamente en presencia de HFMA. Estos resultados mostraron que existen interacciones entre HFMA y T. harzianum que afectan tanto el desarrollo de HFMA como la densidad poblacional de T. harzianum. Los valores obtenidos para los parámetros del crecimiento de la planta evaluados sugieren que el efecto de la interacción entre los microorganismos sobre la planta hospedera es de tipo neutral.