Inoculation of Native Arbuscular Mycorrhizae and Bacillus subtilis Can Improve Growth in Vegetable Crops.

Arbuscular mycorrhizal fungi (AMF) and some rhizobacteria are known as plant growth-promoting microorganism (PGPM) as they play significant roles in improving soil fertility structure, plant nutrition, growth, and health. However, little is known about the PGPM potential of AMF and rhizobacteria native to the Rift Valley and highland regions of Ethiopia. Hence, this study aimed to investigate the PGPM effect of single and co-inoculation of AMF and the Bacillus subtilis ALCR46 strain, on tomato (Lycopersicum esculentum L.), onion (Allium cepa L.), and squash (Cucurbita pepo L.) plants. The experimental setup was a randomized complete block design with three replications of the following treatments: (i) inoculation with a consortium of AMF, (ii) co-inoculation with a consortium of AMF and the Bacillus subtilis, (iii) inoculation with Rhizophagus clarus, (iv) co-inoculation with R. clarus and B. subtilis, (v) inoculation with B. subtilis, (vi) plants without inoculation (negative control), and (vii) plants treated with chemical fertilizer (positive control). Plants were maintained in a greenhouse for 60 days, and after harvest, plant growth parameters, percentage of AMF root colonization, and spore number were analyzed. The result shows that the growth of crops significantly increased by co-inoculation with the consortium of AMF and B. subtilis. AMF spore density and root colonization rate were also increased in co-inoculated plants. Highest root colonization, spore number, and mycorrhizal dependency were observed in A. cepa. Our results suggest that there is a synergistic effect between the AMF and B. subtilis ALCR46, and between AMF inoculants. However, the application of present findings under field conditions is required to be confirmed by further studies.

Datathons: fostering equitability in data reuse in ecology.

Approaches to rapidly collecting global biodiversity data are increasingly important, but biodiversity blind spots persist. We organized a three-day Datathon event to improve the openness of local biodiversity data and facilitate data reuse by local researchers. The first Datathon, organized among microbial ecologists in Uruguay and Argentina assembled the largest microbiome dataset in the region to date and formed collaborative consortia for microbiome data synthesis.

Reporte de caso: reabsorción cervical externa

La reabsorción cervical externa es una patología poco frecuente y difícil de detectar, lo que complica el diagnóstico y pronóstico. El proceso destructivo provoca pérdida progresiva de tejido, comenzando en la superficie radicular y avanzando hacia la pulpa. Este tipo de reabsorción ocurre principalmente en la región cervical de la raíz dental pudiendo confundirse con lesión de caries radicular. El objetivo del reporte de caso es ilustrar al equipo de salud la existencia de esta condición y destacar la importancia del diagnóstico temprano y diferencial para evitar llegar a la pérdida del diente afectado.

External cervical resorption is a rare and difficult-to-detect condition, which complicates diagnosis and prognosis. The destructive process causes progressive loss of tissue, starting at the root surface and advancing towards the pulp. This type of resorption primarily occurs in the cervical region of the dental root and can be confused with root caries. The case report aims to inform the healthcare team about the presence of this condition and emphasizes the significance of early and differential diagnosis to prevent the loss of the affected tooth.

Environmental response of arbuscular mycorrhizal fungi under soybean cultivation at a regional scale.

Climate change, the shortage of fertilizers and reduced land for cultivation have drawn attention to the potential aid provided by soil-borne organisms. Arbuscular mycorrhizal fungi (AMF) offer a wide range of ecosystem benefits and hence, understanding the mechanisms that control AMF occurrence and maintenance is essential for resilient crop production. We conducted a survey of 123 soybean fields located across a 75,000-km2 area of Argentina to explore AMF community composition and to quantify the impact of soil, climate, and geographical distance on these key soil organisms. First, based upon morphological identification of spores, we compiled a list of the AMF species found in the studied area and identified Acaulospora scrobiculata and Glomus fuegianum as the most frequent species. G. fuegianum abundance was negatively correlated with precipitation seasonality and positively correlated with mean annual precipitation as well as mycorrhizal colonisation of soybean roots. Second, we observed that species richness was negatively correlated with soil P availability (Bray I), clay content and mean annual precipitation. Finally, based on partitioning variation analysis, we found that AMF exhibited spatial patterning at a broad scale. Therefore, we infer that geographical distance was positively associated with spore community composition heterogeneity across the region. Nevertheless, we highlight the importance of precipitation sensitivity of frequent species, overall AMF richness and community composition, revealing a crucial challenge to forthcoming agriculture considering an expected change in global climate patterns.

Arbuscular Mycorrhizal Fungi from Argentinean Highland Puna Soils Unveiled by Propagule Multiplication.

Low arbuscular-mycorrhizal (AM) sporulation in arid field soils limits our knowledge of indigenous species when diversity studies are based only on spore morphology. Our aim was to use different approaches (i.e., spore morphological approach and PCR-SSCP (single-strand-conformation-polymorphism) analysis after trap plant multiplication strategies to improve the knowledge of the current richness of glomalean AM fungi (Glomerales; Glomeromycota) from the Argentine Puna. Indigenous propagules from two pristine sites at 3870 and 3370 m of elevation were multiplied using different host plants; propagation periods (2-6 months), and subculture cycles (1; 2; or 3) from 5 to 13 months. The propagule multiplication experiment allowed the detection of different glomoid taxa of Funneliformis spp. and Rhizoglomus spp., which were considered cryptic species since they had never been found in Puna soils before. On the other hand; almost all the generalist species previously described were recovered from cultures; except for Glomus ambisporum. Both plant host selection and culture times are critical for Glomerales multiplication. The SSCP analysis complemented the morphological approach and showed a high variability of Glomus at each site; revealing the presence of Funneliformis mosseae. This study demonstrates that AMF trap culture (TC) is a useful strategy for improving the analysis of AM fungal diversity/richness in the Argentinean highlands.

Microbial community analysis of soils under different soybean cropping regimes in the Argentinean south-eastern Humid Pampas.

Soil microbial communities are key players of ecosystem processes and important for crop and soil health. The Humid Pampas region in Argentina concentrates 75% of the national soybean production, which is based on intensive use of agrochemicals, monocropping and no-till. A long-term field experiment under no-till management in the southeast of the Argentinean Pampas provides a unique opportunity to compare soybean under monocropping with cultivation including alternating cover crops or in a three-phase rotation. We hypothesized that cropping regimes and season affect soil microbial community composition and diversity. Amplicon sequencing of 16S rRNA genes and internal transcribed spacer fragments showed a stronger microbial seasonal dynamic in conservation regimes compared to monocropping. In addition, several bacterial (e.g. Catenulispora, Streptomyces and Bacillus) and fungal genera (e.g. Exophiala) with cropping regime-dependent differential relative abundances were identified. Despite a temporal shift in microbial and chemical parameters, this study shows that long-term cropping regimes shaped the soil microbiota. This might have important implications for soil quality and soybean performance and should therefore be considered in the development of sustainable agricultural managements.

El poder del diagnóstico clínico en las prácticas de terapeutas ocupacionales que trabajan en contextos educativos / O poder do diagnóstico clínico nas práticas de terapeutas ocupacionais que atuam em contextos educacionais / The power of clinical diagnosis in the practices of occupational therapists working in educational contexts

Resumen La Terapia Ocupacional es una disciplina emergente dentro de los equipos educativos multidisciplinarios, por lo que, resulta relevante indagar sobre su rol dentro del contexto educativo chileno. Este artículo presenta una investigación cualitativa cuyo objetivo es analizar desde una perspectiva crítica, cómo influye el diagnóstico clínico en las prácticas de terapeutas ocupacionales que trabajan en contextos educativos, considerando como ejes principales para la investigación, el marco normativo inclusivo vigente en Chile, el discurso de terapeutas ocupacionales a cerca de sus prácticas y las relaciones que se establecen con el diagnóstico clínico en este contexto. La muestra corresponde a diez terapeutas ocupacionales que se desempeñan en establecimientos educativos del sur de Chile, a quienes se les aplicaron entrevistas semi-estructuradas. Los resultados permiten visualizar que las políticas educativas influyen significativamente en las prácticas de terapeutas ocupacionales, aún cuando la normativa no especifica el rol disciplinar. Además, el diagnóstico circula fuertemente en el discurso de terapeutas ocupacionales, funcionando como un dispositivo de poder al interior de las prácticas profesionales, especialmente con el fin de validar el rol profesional dentro del contexto educativo. Se discute el uso del diagnóstico en relación a la identidad profesional y los efectos que tiene sobre los sujetos de intervención. El artículo concluye con la propuesta de adoptar una visión crítica del propio quehacer de la disciplina, basándose en la acción transformadora que ésta busca generar a través de la práctica.

Resumo A Terapia Ocupacional é uma profissão emergente nas equipes educacionais multidisciplinares, portanto, é relevante indagar sobre seu papel, no âmbito educacional, em contexto chileno. Este artigo apresenta uma pesquisa qualitativa cujo objetivo foi analisar, a partir de uma perspectiva crítica, como o diagnóstico clínico influencia nas práticas de terapeutas ocupacionais que atuam em contextos educacionais, considerando como eixos principais para a pesquisa, o marco normativo de inclusão vigente no Chile, o discurso dos profissionais sobre suas práticas e as relações estabelecidas com o diagnóstico clínico. A amostra foi composta de dez terapeutas ocupacionais que atuam em estabelecimentos de ensino no sul do Chile, aos quais foram aplicadas entrevistas semiestruturadas. Os resultados demonstraram que as políticas educacionais influenciam significativamente as práticas dos terapeutas ocupacionais, mesmo quando os regulamentos não especificam seu papel disciplinar. Além disso, o diagnóstico circula fortemente no discurso dos terapeutas ocupacionais, atuando como um dispositivo de poder nas práticas profissionais, com o objetivo de validar o papel profissional no contexto educacional. Discute-se sobre o uso do diagnóstico em relação à identidade profissional e seus efeitos nos sujeitos da intervenção. O artigo conclui com a proposta de adotar uma visão crítica do próprio papel do terapeuta ocupacional, a partir da ação transformadora que esta profissional busca gerar através da prática.

Abstract Occupational Therapy is an emerging discipline within multidisciplinary educational teams, therefore, it's relevant to inquire about its role in the Chilean educational context. This article presents research whose aim was to analyze, from a critical perspective, how clinical diagnosis influences the practices of occupational therapists that work in the school system, considering as the main axes for research, the normative framework that governs the educational system in Chile, the discourse of occupational therapists on their practices and the relationships established with the diagnosis in this context. The sample was ten occupational therapists who work in schools from the south of Chile, to whom semi-structured interviews were applied. The results allow us to visualize that educational policies significantly influence the practices of occupational therapists, even when the regulations do not specify the disciplinary role. In addition, clinical diagnosis emerges strongly in the discourse of occupational therapists, functioning as a device of power within professional practices, especially to validate the professional role within the educational context. The use of diagnosis concerning the professional identity and the effects it has on the people they work with is discussed. This article concludes with the proposal of adopting a critical vision of the discipline's task, based on the transformative action that it seeks to generate through practice.

Extracting DNA of nematodes communities from Argentine Pampas agricultural soils.

We examined four strategies (Tris/EDTA, sodium dodecyl sulfate, Chelex 100 resin and cetyltrimethylammonium bromide -CTAB-) for extracting nucleic acid (DNA) from communities of nematodes. Nematodes were isolated from an agricultural area under different management of long-term crop rotation experiment from Argentina during three seasons. After DNA extraction, Polymerase Chain Reaction-amplifications were performed and considered as indicators of successful DNA extraction. The CTAB combined with proteinase K and phenol-chloroform-isoamyl alcohol was the unique successful method because positive amplifications were obtained by using both eukaryotic and nematode specific primers. This work could contribute to biodiversity studies of nematodes on agroecosystems.

Functionality of arbuscular mycorrhizal fungi in three plant communities in the Managed Floristic Reserve San Ubaldo-Sabanalamar, Cuba / Funcionalidad de hongos micorrízicos arbusculares en tres comunidades vegetales de la Reserva Florística Manejada de San Ubaldo-Sabanalamar, Cuba

Despite the ubiquity and importance of indigenous arbuscular mycorrhizal fungi (AMF) for plant ecosystems; functioning of indigenus mycorrhizal symbiosis (IMS) and related environmental factors at coastal Caribbean ecosystems remains still scarce. In order to determine functionality of IMS under contrasting land uses and wet seasons from Cuba, the influence of the water stress on some AMF functionality parameters from a semi-natural savannah (NS), a recovered savannah (RS) and an agro-ecosystem (AG) from the Managed Floristic Reserve San Ubaldo-Sabanalamar, Pinar del Rio, Cuba were assessed during two-years. Soil and root samples were collected in April and October, during the dry and wet seasons, respectively, in 2008 and 2010. Four plots in each ecosystem were selected, and five soil sub-samples were randomly collected, bulked, mixed homogeneously and used as the composite sample per plot. The host plant root biomass, arbuscular mycorrhizal colonization of the host plant, density of the intraradical and extraradical AMF mycelia, fungal endophyte biomass and AMF spore density were assessed. The host plant root biomass increased in the NS environment during the dry season, and approximately 12.85g root/dm³ dry soil was recorded. The colonization degree were significantly higher in all environments during the wet season of the second year, with means ranging from 79% to 89%. The extraradical mycelia were significantly more abundant in the dry season of the second year in all environments, with a maximum of 279mg/dm³ in the RS ecosystem. The density of AMF spores was highest in the dry season of the second year for the three studied ecosystems. The RS ecosystem hosted 5 670 spores/100g dry soil. In general, the influence of rainfall seasonality on the function of AMF was stronger than the influence of ecosystem management. The root biomass and extraradical mycelia were high in the dry seasons, suggesting strategies to increase the volume of soil for the mutual benefit of the symbionts. The increase in spore density during the dry seasons appears as an adaptation allowing AMF to survive period of water shortage. This study improves our understanding of the adaptative responses of arbuscular mycorrhizal symbiosis to seasonal variations in soil water availability. Rev. Biol. Trop. 63 (2): 341-356. Epub 2015 June 01.

En el presente estudio se evaluó, durante dos años, la influencia de los períodos seco y lluvioso sobre el funcionamiento de hongos formadores de micorrizas arbusculares (HFMA) simbiontes de plantas nativas de una sabana semi natural, una sabana recuperada de la actividad agrícola y un agroecosistema, ubicados en la Reserva Florística Manejada San Ubaldo-Sabanalamar, Pinar del Río, Cuba. Se recolectaron muestras de suelo en abril y octubre (período seco y húmedo de 2008 y 2010, respectivamente). Dentro de cada ecosistema se seleccionaron cuatro parcelas y se recolectaron cinco submuestras al azar, las que fueron homogeneizadas para formar una muestra compuesta por parcela. Se cuantificó la biomasa de raicillas, la colonización micorrízica de las plantas hospedadoras en el campo, el micelio extrarradical, el micelio endófito y la densidad de esporas. La biomasa de raicillas en la sabana semi natural incrementó durante los períodos secos, la cual alcanzó hasta 12.85 g/dm3 de suelo. En todos los ecosistemas, la mayor colonización micorrízica ocurrió en la época lluviosa del segundo año con valores que oscilaron entre 79 y 89 %. Las mayores biomasas de micelio externo fueron registradas en los tres ecosistemas durante el período seco del segundo año, con un valor máximo de 279 mg/dm3 de suelo en la sabana recuperada. La mayor densidad de esporas de HFMA fue determinada en el periodo seco del segundo año para los tres ecosistemas estudiados, con el valor más alto en la sabana recuperada con 5 670 esporas/100 g de suelo seco. De manera general, se evidenció un efecto de la estacionalidad de la lluvia más que del manejo de ecosistema sobre el funcionamiento de los HFMA. La mayor actividad colonizadora se evidenció en períodos húmedos, mientras que mayor biomasa de raicillas y micelio externo durante los períodos secos, lo que sugiere estrategias de incremento del volumen del suelo explorado por parte de los HFMA como de las plantas hospedadoras. La proliferación de esporas evidenció la formación de estructuras de resistencia de los HFMA ante condiciones adversas. Los resultados obtenidos pondrían en evidencia la plasticidad de la simbiosis micorrízica ante variaciones en la disponibilidad de agua.

[Physical and chemical methods for eliminating propagules of indigenous mycorrhizal fungi from soil samples]. / Métodos físicos y químicos para la eliminación de propágulos de hongos formadores de micorrizas nativos de muestras de suelo.

The objective of this work was to evaluate methods to eliminate or reduce the number of indigenous arbuscular mycorrhizal fungi (AMF) from soil samples without affecting their edaphic or microbiological properties. At an early trial we evaluated moist heat (autoclaving), dry heat (oven), sodium hypochlorite (NaClO) and formaldehyde at a range of 100.0-3.3µl/g and 16.7-3.3µl/g respectively. There was no germination in plants of ryegrass (Lolium multiflorum Lam.) sown on substrates receiving NaClO (100.0-33.3µl/g), whereas autoclaving significantly increased the available soil phosphorous content. Both treatments failed to eradicate AMF colonization at 9 weeks; therefore, they were discarded. In a second trial, oven and formaldehyde (10.0µl/g) treatments were analyzed to assess the effects of seed decontamination and AMF reinoculation. Both procedures were effective in reducing or eliminating indigenous AMF at a range of soil P availability of 12-29mg/kg. However, the time between soil treatment and AMF multiplication and safety requirements were greater in the case of formaldehyde application.

Métodos físicos y químicos para la eliminación de propágulos de hongos formadores de micorrizas nativos de muestras de suelo / Physical and chemical methods for eliminating propagules of indigenous mycorrhizal fungi from soil samples

El objetivo de este trabajo fue evaluar métodos para eliminar hongos nativos formadores de micorrizas arbusculares (HMA) o reducir su número en muestras de suelo, sin afectar sus propiedades edáficas y microbiológicas. Se estudió la aplicación de calor húmedo (autoclave), de calor seco (estufa), de hipoclorito de sodio (NaClO) y de formaldehído, en concentraciones entre 100,0 y 3,3 µl/g y 16,7 y 3,3 µl/g, respectivamente. Las semillas de raigrás (Lolium multiflorum Lam.) sembradas en sustratos que recibieron NaClO (100,0-33,3 µl/g) no germinaron y el autoclave incrementó el contenido de fósforo en el sustrato. Estos tratamientos no eliminaron la micorrización por HMA y ambos fueron descartados. En un segundo ensayo se analizaron los tratamientos estufa y formaldehído (10,0 µl/g), asociados o no a la descontaminación de las semillas y a la reinoculación con HMA. Ambos procedimientos redujeron o eliminaron la micorrización por HMA nativos en suelos con 12 a 29 mg/kg de fósforo y permitieron la multiplicación de inóculos de HMA. El tiempo de ventilación de las muestras y los requisitos de seguridad fueron mayores con la aplicación de formaldehído

The objective of this work was to evaluate methods to eliminate or reduce the number of indigenous arbuscular mycorrhizal fungi (AMF) from soil samples without affecting their edaphic or microbiological properties. At an early trial we evaluated moist heat (autoclaving), dry heat (oven), sodium hypochlorite (NaClO) and formaldehyde at a range of 100.0-3.3 µl/g and 16.7-3.3 µl/g respectively. There was no germination in plants of ryegrass (Lolium multiflorum Lam.) sown on substrates receiving NaClO (100.0-33.3 ul/g), whereas autoclaving significantly increased the available soil phosphorous content. Both treatments failed to eradicate AMF colonization at 9 weeks; therefore, they were discarded. In a second trial, oven and formaldehyde (10.0 µl/g) treatments were analyzed to assess the effects of seed decontamination and AMF reinoculation. Both procedures were effective in reducing or eliminating indigenous AMF at a range of soil P availability of 12-29 mg/kg. However, the time between soil treatment and AMF multiplication and safety requirements were greater in the case of formaldehyde application

[Mycotrophic capacity and efficiency of microbial consortia of arbuscular mycorrhizal fungi native of soils from Buenos Aires province under contrasting management]. / Capacidad micotrófica y eficiencia de consorcios con hongos micorrícicos nativos de suelos de la provincia de Buenos Aires con manejo contrastante.

We characterized the infective and sporulation capacities of microbial consortia of arbuscular mycorrhizal fungi (AMF) native of Buenos Aires province (Argentina) and determined if some soil characteristics and mycorrhizal parameters could allow to select potentially beneficial inocula. Soil samples were selected from seven locations in Buenos Aires province all under agricultural (A) and pristine (P) conditions. The AMF were multiplied and mycorrhizal root colonization of trap plants was observed at 10 weeks of growth. Spore number in field was low; however, after multiplication spore density accounted for 80-1175 spores per 100g of soil. The principal component analysis showed that the P and Fe soil contents are the main modulators of infectivity and sporulation capacity. The mycorrhizal potential was determined in three locations, being high in Pristine Lobería and Agricultural Trenque Lauquen and low in Junín. Agricultural Lobería (AL) and Pristine Lobería (PL) inocula were selected and their efficiency was evaluated under controlled conditions. Even though shoot dry matter increases after inoculation was not significant (p>0.05) mycorrhizal response was greater than 40% for tomato and 25% for corn, particularly after inoculation with inocula from the agricultural management. These results could be associated to the incipient development of mycorrhizae in both species. Additional research should be conducted to further develop our findings in order to determine the factors involved in the selection of efficient inocula.

Capacidad micotrófica y eficiencia de consorcios con hongos micorrícicos nativos de suelos de la provincia de Buenos Aires con manejo contrastante / Mycotrophic capacity and efficiency of microbial consortia of arbuscular mycorrhizal fungi native of soils from Buenos Aires province under contrasting management

Se evaluó la capacidad micotrófica y de esporulación de consorcios microbianos con hongos micorrícicos arbusculares (HMA) nativos de suelos de la provincia de Buenos Aires (Argentina), y se determinó si las características edáficas y los parámetros micorrícicos podrían permitir seleccionar inóculos potencialmente benéficos. Se seleccionaron muestras de suelo provenientes de 7 localidades, cada una bajo manejo agrícola (A) y prístino (P). Se instalaron plantas trampa y a las 10 semanas de crecimiento se evidenció colonización micorrícica en la raíces. El número de esporas del suelo de campo fue bajo, mientras que en el sustrato donde crecieron las plantas trampa varió entre 80-1175 esporas/100 g. El análisis de componentes principales indicó que los contenidos de P y Fe en el suelo fueron los principales moduladores de la capacidad micotrófica y de esporulación. Se determinó el potencial micorrícico (PM) de muestras provenientes de tres localidades: Lobería, Junín y Trenque Lauquen. Se verificó un PM elevado en las muestras provenientes de Lobería con suelo prístino y en las de Trenque Lauquen bajo manejo agrícola, mientras que fue bajo en las de Junín. Finalmente, se evaluó la eficiencia en condiciones controladas de suelos-inóculo de Lobería bajo manejo agrícola o prístino en plantas de maíz y de tomate. Si bien los incrementos en la materia seca asociados a la inoculación fueron no significativos (p > 0,05), la respuesta micorrícica fue superior al 40 % en tomate y al 25 % en maíz, particularmente con el inóculo proveniente del sitio agrícola. Los bajos incrementos de crecimiento estarían asociados con la incipiente micorrización en ambas especies. Se plantea la necesidad de profundizar los estudios a efectos de determinar los factores involucrados que permitirían seleccionar inóculos eficientes.

We characterized the infective and sporulation capacities of microbial consortia of arbuscular mycorrhizal fungi (AMF) native of Buenos Aires province (Argentina) and determined if some soil characteristics and mycorrhizal parameters could allow to select potentially beneficial inocula. Soil samples were selected from seven locations in Buenos Aires province all under agricultural (A) and pristine (P) conditions. The AMF were multiplied and mycorrhizal root colonization of trap plants was observed at 10 weeks of growth. Spore number in field was low; however, after multiplication spore density accounted for 80-1175 spores per 100 g of soil. The principal component analysis showed that the P and Fe soil contents are the main modulators of infectivity and sporulation capacity. The mycorrhizal potential was determined in three locations, being high in Pristine Lobería and Agricultural Trenque Lauquen and low in Junín. Agricultural Lobería (AL) and Pristine Lobería (PL) inocula were selected and their efficiency was evaluated under controlled conditions. Even though shoot dry matter increases after inoculation was not significant (p > 0.05) mycorrhizal response was greater than 40% for tomato and 25% for corn, particularly after inoculation with inocula from the agricultural management. These results could be associated to the incipient development of mycorrhizae in both species. Additional research should be conducted to further develop our findings in order to determine the factors involved in the selection of efficient inocula.

Capacidad micotrófica y eficiencia de consorcios con hongos micorrícicos nativos de suelos de la provincia de Buenos Aires con manejo contrastante / Mycotrophic capacity and efficiency of microbial consortia of arbuscular mycorrhizal fungi native of soils from Buenos Aires province under contrasting management

Se evaluó la capacidad micotrófica y de esporulación de consorcios microbianos con hongos micorrícicos arbusculares (HMA) nativos de suelos de la provincia de Buenos Aires (Argentina), y se determinó si las características edáficas y los parámetros micorrícicos podrían permitir seleccionar inóculos potencialmente benéficos. Se seleccionaron muestras de suelo provenientes de 7 localidades, cada una bajo manejo agrícola (A) y prístino (P). Se instalaron plantas trampa y a las 10 semanas de crecimiento se evidenció colonización micorrícica en la raíces. El número de esporas del suelo de campo fue bajo, mientras que en el sustrato donde crecieron las plantas trampa varió entre 80-1175 esporas/100 g. El análisis de componentes principales indicó que los contenidos de P y Fe en el suelo fueron los principales moduladores de la capacidad micotrófica y de esporulación. Se determinó el potencial micorrícico (PM) de muestras provenientes de tres localidades: Lobería, Junín y Trenque Lauquen. Se verificó un PM elevado en las muestras provenientes de Lobería con suelo prístino y en las de Trenque Lauquen bajo manejo agrícola, mientras que fue bajo en las de Junín. Finalmente, se evaluó la eficiencia en condiciones controladas de suelos-inóculo de Lobería bajo manejo agrícola o prístino en plantas de maíz y de tomate. Si bien los incrementos en la materia seca asociados a la inoculación fueron no significativos (p > 0,05), la respuesta micorrícica fue superior al 40 % en tomate y al 25 % en maíz, particularmente con el inóculo proveniente del sitio agrícola. Los bajos incrementos de crecimiento estarían asociados con la incipiente micorrización en ambas especies. Se plantea la necesidad de profundizar los estudios a efectos de determinar los factores involucrados que permitirían seleccionar inóculos eficientes.(AU)

We characterized the infective and sporulation capacities of microbial consortia of arbuscular mycorrhizal fungi (AMF) native of Buenos Aires province (Argentina) and determined if some soil characteristics and mycorrhizal parameters could allow to select potentially beneficial inocula. Soil samples were selected from seven locations in Buenos Aires province all under agricultural (A) and pristine (P) conditions. The AMF were multiplied and mycorrhizal root colonization of trap plants was observed at 10 weeks of growth. Spore number in field was low; however, after multiplication spore density accounted for 80-1175 spores per 100 g of soil. The principal component analysis showed that the P and Fe soil contents are the main modulators of infectivity and sporulation capacity. The mycorrhizal potential was determined in three locations, being high in Pristine Lobería and Agricultural Trenque Lauquen and low in Junín. Agricultural Lobería (AL) and Pristine Lobería (PL) inocula were selected and their efficiency was evaluated under controlled conditions. Even though shoot dry matter increases after inoculation was not significant (p > 0.05) mycorrhizal response was greater than 40% for tomato and 25% for corn, particularly after inoculation with inocula from the agricultural management. These results could be associated to the incipient development of mycorrhizae in both species. Additional research should be conducted to further develop our findings in order to determine the factors involved in the selection of efficient inocula.(AU)

Capacidad micotrófica y eficiencia de consorcios con hongos micorrícicos nativos de suelos de la provincia de Buenos Aires con manejo contrastante. / [Mycotrophic capacity and efficiency of microbial consortia of arbuscular mycorrhizal fungi native of soils from Buenos Aires province under contrasting management].

We characterized the infective and sporulation capacities of microbial consortia of arbuscular mycorrhizal fungi (AMF) native of Buenos Aires province (Argentina) and determined if some soil characteristics and mycorrhizal parameters could allow to select potentially beneficial inocula. Soil samples were selected from seven locations in Buenos Aires province all under agricultural (A) and pristine (P) conditions. The AMF were multiplied and mycorrhizal root colonization of trap plants was observed at 10 weeks of growth. Spore number in field was low; however, after multiplication spore density accounted for 80-1175 spores per 100g of soil. The principal component analysis showed that the P and Fe soil contents are the main modulators of infectivity and sporulation capacity. The mycorrhizal potential was determined in three locations, being high in Pristine Lobería and Agricultural Trenque Lauquen and low in Junín. Agricultural Lobería (AL) and Pristine Lobería (PL) inocula were selected and their efficiency was evaluated under controlled conditions. Even though shoot dry matter increases after inoculation was not significant (p>0.05) mycorrhizal response was greater than 40

for tomato and 25

for corn, particularly after inoculation with inocula from the agricultural management. These results could be associated to the incipient development of mycorrhizae in both species. Additional research should be conducted to further develop our findings in order to determine the factors involved in the selection of efficient inocula.

Métodos físicos y químicos para la eliminación de propágulos de hongos formadores de micorrizas nativos de muestras de suelo. / [Physical and chemical methods for eliminating propagules of indigenous mycorrhizal fungi from soil samples].

The objective of this work was to evaluate methods to eliminate or reduce the number of indigenous arbuscular mycorrhizal fungi (AMF) from soil samples without affecting their edaphic or microbiological properties. At an early trial we evaluated moist heat (autoclaving), dry heat (oven), sodium hypochlorite (NaClO) and formaldehyde at a range of 100.0-3.3Al/g and 16.7-3.3Al/g respectively. There was no germination in plants of ryegrass (Lolium multiflorum Lam.) sown on substrates receiving NaClO (100.0-33.3Al/g), whereas autoclaving significantly increased the available soil phosphorous content. Both treatments failed to eradicate AMF colonization at 9 weeks; therefore, they were discarded. In a second trial, oven and formaldehyde (10.0Al/g) treatments were analyzed to assess the effects of seed decontamination and AMF reinoculation. Both procedures were effective in reducing or eliminating indigenous AMF at a range of soil P availability of 12-29mg/kg. However, the time between soil treatment and AMF multiplication and safety requirements were greater in the case of formaldehyde application.