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Resumen Introducción: El café es una planta altamente micotrófica, por lo que la interacción con los hongos micorrízicos arbusculares (HMA) se ha estudiado en distintos países tropicales. La mayoría de los trabajos publicados indican que el café se beneficia de la asociación micorrízica, donde los HMA confieren protección ante patógenos y enfermedades, incrementa la absorción de agua, así como la adaptación de la planta durante el trasplante de vivero al campo. Objetivo: Se realizó una revisión donde se resumieron y analizaron trabajos reportados por la asociación de HMA y café de los últimos 10 años, enfocada en la distribución global de especies de HMA, beneficio nutricional de la asociación y su interacción con patógenos. Métodos: Se revisaron diferentes bases de datos que reportaron trabajos realizados en los principales países productores de café. La revisión se centró principalmente en los trabajos publicados entre el 2000 y el 2019, sin embargo, en algunos casos se incluyeron artículos clásicos en el tema, que no corresponden al periodo señalado, principalmente los realizados en Brasil desde 1986. Se organizó el número de especies reportadas por país, se buscaron sinonimias y agruparon por familia, género y especie. Los trabajos donde solo se reportan géneros o las especies presentaron ambigüedad, se usaron como referencia, pero no se incluyeron en el análisis final. Se resumieron los reportes de los beneficios de la interacción de HMA con café, así como la tolerancia a patógenos. Resultados: Los datos recabados muestran que hay más de 100 especies de HMA asociadas con el café, lo cual representa más de la tercera parte del total de las especies reportadas en el mundo. En Colombia se reportó la mayor riqueza de especies de HMA, lo cual puede deberse a que es el país con más reportes en el tema. Conclusiones: Esta información muestra los beneficios de la incorporación de HMA en los programas de replantación de fincas de café, pues estos hongos son un elemento clave en la nutrición de los cafetos, sin embargo, se debe considerar la variedad de café cultivada y la introducción de HMA, pues no en todas hay una asociación exitosa.
Abstract Introduction: Coffee is a highly mycotrophic plant, its interaction with arbuscular mycorrhizal fungi has been studied among different tropical countries. The majority of the published works indicates that coffee is benefited from the mycorrhizal association, where the AMF confers protection against pathogens and diseases, increases water absorption, as well as it increases the adaptation of the plant at transplant from nurseries to the main plantation. Objective: A review was made where we summarized and analyze the research reports of AMF with coffee from at least the past 10 years, focused on AMF global species distribution, nutritional benefits of the association and interaction with pathogens. Methods: We retrieved available bibliographic data from coffee producer countries in public databases. We considered published works from 2000 to 2019, nevertheless, we included classic papers on the topic, outside that period, mainly the ones performed in Brazil since 1986. We organized the number of reported species per country, we look for synonyms, grouped them by family, genera and species. The reports that only reported genera or where ambiguous were used as reference but not considered for the final analysis. We summarized the reports of the benefits of the AMF interaction in coffee, as well as pathogen tolerance. Results: The collected data shows that there are more than 100 AMF species associated with coffee, which represents more than a third part of the total of reported species worldwide. We found that Colombia has the highest richness, but it also has the highest number of published reports. Conclusions: This information shows the benefits of the incorporation of AMF to coffee plantation programs, because these fungi are a key element in coffee plant nutrition, nevertheless, the coffee variety should be considered when introducing AMF, as not all associations has been efficient.
Subject(s)
Coffee , Mycorrhizae , Fungi , MexicoABSTRACT
Abstract Rhizosphere microorganisms and endophytes can help their hosts absorb nutrients and regulate the levels of plant hormones. Moreover, they can modulate the expressions of host genes, assist hosts in eliminating reactive oxygen species (ROS) and secreting volatile organic compounds. Therefore, rhizosphere microorganisms and endophytes are considered as determinant factors driving processes involved in the growth of host plants. However, the physiological and ecological functions, as well as the molecular mechanism underlying the behavior of rhizosphere microorganisms and endophytes in their role in the adaptive capacity of host plants in the karstic high-calcium environment have not been systematically studied. This review summarizes the physiological and molecular mechanisms of rhizosphere microorganisms and endophytes which help host plants to adapt to various kinds of adverse environments. The adaptive capacities of plants growing in adverse environments, partly, or totally, depends on microorganisms co-existing with the host plants.
Resumo Os microorganismos e endófitos da rizosfera podem ajudar seus hospedeiros a absorver nutrientes e regular os níveis de hormônios vegetais. Além disso, eles podem modular as expressões dos genes hospedeiros, auxiliar os hospedeiros na eliminação de espécies reativas de oxigênio (ROS) e secretar compostos orgânicos voláteis. Portanto, microorganismos e endófitos da rizosfera são considerados determinantes dos processos envolvidos no crescimento de plantas hospedeiras. No entanto, as funções fisiológicas e ecológicas, bem como o mecanismo molecular subjacente ao comportamento dos microrganismos e endofíticos da rizosfera no seu papel na capacidade adaptativa das plantas hospedeiras no ambiente cárstico de alto teor de cálcio, não foram sistematicamente estudados. Esta revisão resume os mecanismos fisiológicos e moleculares de microrganismos e endófitos da rizosfera que ajudam as plantas hospedeiras a se adaptarem a vários tipos de ambientes adversos. As capacidades adaptativas das plantas que crescem em ambientes adversos, em parte ou totalmente, dependem de microrganismos coexistentes com as plantas hospedeiras.
Subject(s)
Symbiosis , Calcium , Plants , Rhizosphere , EndophytesABSTRACT
Introduction: The sustainable production of pastures has become a fundamental challenge for the livestock sector where research with plant growth-promoting rhizobacteria as a viable solution, has nearly not been reported. Objective: In this study, we aimed to examine the potential to stimulate growth in Pennisetum clandestinum grass using four isolated bacterial strains from soils obtained from a Colombian tropical silvopastoral system. Methods: We previously identified genetically the strains and characterized two plant growth promoting activities. In addition, we evaluated the growth-promoting effect of the strains in Kikuyo grass under greenhouse conditions. Results: We found that the four bacterial strains were phylogenetically associated with Klebsiella sp. (strains 28P and 35P), Beijerinka sp. (37L) and Achromobacter xylosoxidans (E37), based on partial 16S rRNA gene sequencing. Moreover, the in vitro biochemical assays demonstrated that the strains exhibited some plant growth promoting mechanisms such as 1-aminocyclopropane-1-carboxylic acid deaminase activity and indole compound synthesis. Notably, bacterial inoculation under greenhouse conditions showed a positive influence on P. clandestinum growth. We found a significant (P < 0.05) effect on root and shoot length and shoot dry weight. Shoot length increased by 52 % and 30 % with 37L and 35P compared to those without inoculation treatment. Similarly, the use of 37L and 28P raised shoot dry weight values by 170 % and 131 %, respectively. In root development, inoculation with strains 37L and E37 increased root length by 134 % and 100 %, respectively. Conclusion: Beijerinckia sp. 37L was the most effective of the four strains at increasing P. clandestinum biomass and length.
Introducción: La producción sostenible de pastos se ha convertido en un desafío fundamental para el sector ganadero, donde investigaciones con bacterias promotoras de crecimiento vegetal, como una solución viable, han sido poco reportadas. Objetivo: El objetivo de este estudio fue examinar el potencial para estimular el crecimiento del pasto Pennisetum clandestinum utilizando cuatro cepas bacterianas aisladas de suelos obtenidos de un sistema silvopastoril tropical colombiano. Métodos: Anteriormente identificamos genéticamente las cepas y caracterizamos dos actividades que promueven el crecimiento de las plantas. Además, evaluamos el efecto promotor del crecimiento de las cepas en el pasto Kikuyo en condiciones de invernadero. Resultados: Encontramos que las cuatro cepas bacterianas se asociaron filogenéticamente con Klebsiella sp. (cepas 28P y 35P), Beijerinka sp. (37L) y Achromobacter xylosoxidans (E37), basados en la secuenciación parcial del gen 16S rRNA. Además, los ensayos bioquímicos in vitro demostraron que las cepas exhibían algunos mecanismos que promueven el crecimiento de las plantas tales como la actividad de la enzima desaminasa del ácido 1-aminociclopropano-1- carboxílico, y la síntesis del compuesto indol. En particular, la inoculación bacteriana bajo condiciones de invernadero mostró una influencia positiva en el crecimiento de P. clandestinum. Encontramos un efecto significativo (P < 0.05) en la longitud de la raíz y el tallo, y el peso seco del tallo. La longitud del tallo aumentó en un 52 % y 30 % con 37L y 35P, respectivamente, en comparación con aquellos sin tratamiento de inoculación. Igualmente, el uso de las cepas 37L y 28P aumentó los valores de peso seco del tallo en un 170 y un 131 %, respectivamente. En el desarrollo de la raíz, la inoculación con las cepas 37L y E37 aumentó la longitud de la raíz en 134 y 100 %, respectivamente. Conclusión: Beijerinckia sp. 37L fue la más efectiva de las cuatro cepas al aumentar la biomasa y la longitud de P. clandestinum.
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RESUMEN La producción orgánica de seda incluye la aplicación de compost como practica de cultivo en morera (Morus alba), sin embargo, el efecto de la fertilización orgánica en las poblaciones de bacterias rizosféricas no siempre es positivo. Para evaluar el efecto del compost en la diversidad de bacterias rizosféricas en cultivos de morera (Morus alba), se aplicaron 0, 0.25, 0.5 y 1 kg.m-2 de compost a parcelas con morera dispuestas en un diseño en bloques completos al azar. De cada parcela se extrajo ADN del suelo rizosférico a los 0, 5, 10 y 90 días de aplicado el compost y se amplificó la región V4 del gen ADNr 16S para su secuenciación y asignación taxonómica de los OTUS. Los índices de diversidad alpha mostraron la dominancia de algunos grupos taxonómicos, como los phyla Proteobacteria y Acidobacteria y los géneros Pseudomonas, Opitutus, Luteolibacter y Nitrospir. La diversidad beta indicó similitud entre las muestras influenciadas por la aplicación compost y el incremento de la diversidad en las parcelas muestreadas al final del experimento (90 días). Los grupos taxonómicos dominantes se caracterizan por su función en el ciclo del nitrógeno. Así, se concluyó que la aplicación de 1 kg.m-2 llevó al aumento de la humedad del suelo, el pH y la disponibilidad de nutrientes, lo que incremento la diversidad de bacterias rizosféricas con cambios positivos en composición, riqueza y abundancia en los niveles de orden, familia y género.
ABSTRACT The organic silk production includes the application of compost as cultivation practice to the mulberry crop. However, the effect of the organic fertilization on populations of rhizospheric bacteria is not always positive. To evaluate the effect of compost on the diversity of rhizospheric bacteria in mulberry crops (Morus alba), 0, 0.25, 0.5 and 1 kg.m-2 of compost was applied to mulberry plots arranged in a completely randomized blocks design. From each plot, DNA was extracted from the rhizospheric soil at 0, 5, 10 and 90 days after compost was applied and the V4 region of the 16S rDNA gene was amplified for its sequencing and taxonomic assignment of the OTUS. Alpha diversity indices showed the dominance of some taxonomic groups, such as the phyla Proteobacteria and Acidobacteria, and the genera Pseudomonas, Opitutus, Luteolibacter and Nitrospira. The beta diversity indicated similarity between the samples influenced by the compost application and the increase of the biodiversity in the plots sampled at the end of the experiment (90 days). The taxonomic groups dominated are characterized by their role in the nitrogen cycle. Thus, it was concluded that the application of 1 kg.m-2 of compost led to the increase of ground humidity, soil pH and nutrient availability which increased the rhizospheric bacteria diversity with positive changes in composition, richness and abundance at order, family and genera levels.
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En el presente trabajo estudiamos el grado de tolerancia a metales pesados de hongos y bacterias aisladas de suelos con y sin rizósfera, con el propósito de conocer su potencial para aplicaciones en biorremediación. Las muestras procedían del pasivo minero de Santa Rosa de Jangas. Los hongos y bacterias aislados fueron identificados taxonómicamente mediante el análisis de la región ITS y 16S ADNr, respectivamente. El índice de tolerancia a metales pesados se calculó usando medio salino suplementado con 1 mM a plomo (II), cobre (II), niquel (II) o zinc (II), y 0.1 mM a plata (I), cromo (VI) o cadmio (II). En total se aislaron 23 hongos y 18 bacterias. Las cepas de hongos con mejores índices de tolerancia fueron: Fusarium temperatum CTLM05 (Pb+2), Fusarium temperatum CTLM08 (Zn+2), Fusarium oxysporum CTLM18 (Ni+2 y Cd+2), Fusarium oxysporum CTLM12 (Ag+1), Fusarium inflexum CTLM22 (Cu+2) y Penicillium vanluykii CTLM11 (Cr+6). Las cepas de bacterias con mayores índices de tolerancia fueron Bacillus licheniformis SSR18 (Cd+2, Ni+2 y Zn+2), Bacillus subtilis SSR3 (Pb+2), Serratia sp. SSR15 (Cu+2), Serratia sp. SSR13 (Ag+1) y Bacillus cereus SSR01 (Cr+6). También se encontró que los hongos mostraron mejores índices de tolerancia que las bacterias. Finalmente, los suelos del pasivo ambiental minero de Santa Rosa de Jangas poseen una microflora interesante, probablemente con mecanismos para su adaptación, crecimiento y desarrollo sobre metales pesados y pueden ser de utilidad para el desarrollo de procesos biotecnológicos y biorremediación.
In this work, we studied the degree of tolerance to heavy metals of fungi and bacteria isolated from soils with and without rhizosphere, in order to know its potential for applications in bioremediation. The samples came from Santa Rosa de Jangas mining liability. The fungi and bacterial strains were taxonomically identified by ITS region and 16S rDNA analysis, respectively. Heavy metal tolerance indices were calculate using salt medium supplemented with 1mM of lead (II), cupper (II), nickel (II) or zinc (II); and 0.1 mM of silver (I), chromium(VI) or cadmium (II). It was isolated 23 fungi and 18 bacteria strains. The fungi with better tolerance indices were Fusarium temperatum CTLM05 (Pb+2), Fusarium temperatum CTLM08 (Zn+2), Fusarium oxysporum CTLM18 (Ni+2 and Cd+2), Fusarium oxysporum CTLM12 (Ag+1), Fusarium inflexum CTLM22 (Cu+2), and Penicillium vanluykii CTLM11 (Cr+6). Likewise, the bacterial strains with better tolerance indices were Bacillus licheniformis SSR18 (Cd+2, Ni+2 and Zn+2), Bacillus subtilis SSR3 (Pb+2), Serratia sp. SSR15 (Cu+2), Serratia sp. SSR13 (Ag+1) and Bacillus cereus SSR01 (Cr+6). Too, it was found that fungi showed better tolerance indices than bacterial strains. Finally, the soil from Santa Rosa waste mine have an interesting microflora, probably with mechanisms for their adaptation, growth, and development were heavy metals are present and they could be useful to perform biotechnology and bioremediation processes.
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RESUMEN La agricultura moderna enfrenta nuevos desafíos, integrando enfoques ecológicos y moleculares, para lograr mayores rendimientos de los cultivos y reducir al mínimo los impactos sobre el ambiente. Para generar mayores rendimientos se han incrementado significativamente las dosis de fertilizantes sintéticos por unidad de superficie, los cuales pueden provocar contaminación, daños a la salud y pérdida de la fertilidad de los suelos, convirtiéndose en una de las preocupaciones más importantes en la producción agrícola. Para mejorar la producción sin el uso de fertilizantes de origen sintético, las investigaciones se han orientado hacia el desarrollo de nuevas biotecnologías: provocando que exista un interés creciente en los microorganismos benéficos del suelo ya que éstos pueden promover el crecimiento de las plantas y, en algunos casos, evitar infecciones del tejido vegetal por patógenos. Las interacciones de las rizobacterias promotoras del crecimiento vegetal (RPCV) con el medio biótico - plantas y microorganismos - son muy complejas y utilizan diferentes mecanismos de acción para promover el crecimiento de las plantas. Estos mecanismos se agrupan en: 1) Biofertilización; 2) Fito-estimulación; y 3) Biocontrol. Inocular los cultivos con RPCV reduce sustancialmente el uso de fertilizantes sintéticos y los impactos negativos al suelo, aumenta el rendimiento de los cultivos, contribuyendo a la economía del productor y a la alimentación de la población. Esta revisión describe aspectos básicos inherentes a la interacción entre las RPCV y las especies vegetales, centrándose en los beneficios que aportan las RPCV a la actividad agrícola.
ABSTRACT Modern agriculture faces new challenges, integrating ecological and molecular approaches, to achieve higher crop yields and to minimize negative impacts on the environment. To generate higher yields, the doses of synthetic fertilizers per unit area have been significantly increased, which can cause contamination, damage to the health and loss of soil fertility, making this one of the most important concerns in agricultural production. To improve production without the use of fertilizers of chemical origin, research has been oriented towards the development of new biotechnologies: causing a growing interest in beneficial microorganisms in the soil, as these can promote plant growth and, in some cases, avoid infections of plant tissue by pathogens. The interactions of plant growth promoting rhyzobacteria (PGPR) with the biotic medium - plants and microorganisms - are very complex and use different mechanisms of action to promote plant growth. These mechanisms are grouped into: 1) Biofertilization; 2) Phytostimulation and 3) Biocontrol. Inoculating the crops with PGPR could substantially reduce the use of synthetic fertilizers and the negative impacts to the soil, increase crop yields, contributing to the producer's economy and the population's nutrition. This review describes basic aspects inherent to the interaction between PGPR and plant species, focusing on the benefits of PGPR to the agricultural activity.
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ABSTRACT: Soils which are cultivated with grapevines have high available copper (Cu) content, which can be toxic to cover crops cohabiting vineyards, such as black oats. This study aimed to assess the effect of liming in reducing Cu toxicity in black oats grown in sandy soils. Samples of a Typic Hapludalf were collected at 0-20cm, dried and subjected to the addition of Cu (0 to 50Mg kg-1) and limestone (0, 1.5, and 3.0Mg ha-1). The soil was placed in a rhizobox and black oats were grown for 30 days. We assessed root and shoot dry matter production, copper (Cu), calcium (Ca) and magnesium (Mg) contents in the tissues; Cu content in the root symplast and apoplast, as well as Cu, carbon and pH values in the rhizosphere and bulk soil. Liming reduced Cu toxicity in black oats. Cu was preferentially accumulated in the roots, mostly in the apoplast, which may be the result of a plant tolerance mechanism to prevent the transport of Cu to the shoots.
RESUMO: Solos cultivados com videiras possuem alto teor de cobre (Cu) disponível, que pode ser tóxico às plantas de cobertura do solo que coabitam vinhedos, como a aveia preta. O estudo objetivou avaliar o efeito da calagem na redução da toxidez por Cu em plantas de aveia preta cultivadas em solo arenoso. Amostras de um Argissolo Vermelho foram coletadas na camada de 0-20cm, secas e submetidas à adição de duas doses de Cu (0 e 50Mg kg-1) e três de calcário (0, 1,5 e 3,0Mg ha-1). O solo foi acondicionado em rhizobox e submetido ao cultivo de aveia preta durante 30 dias. Avaliaram-se a produção de matéria seca das raízes e da parte aérea, o teor de cobre (Cu), cálcio (Ca) e magnésio (Mg) nos tecidos; o teor de Cu no simplasto e apoplasto das raízes, e os teores de Cu, de carbono e valores de pH no solo rizosférico e não rizosférico. A aplicação de calcário reduziu a toxidez por Cu na aveia preta. O Cu foi preferencialmente acumulado nas raízes, especialmente no apoplasto, o que pode ser resultado de mecanismo de tolerância das plantas para evitar o transporte de parte do elemento para a parte aérea.
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Resumen El uso de Rizobacterias promotoras de crecimiento vegetal (PGPR, por sus siglas en ingles) constituye una alternativa al uso de fertilizantes químicos favoreciendo el rendimiento de los cultivos. La presente investigación tuvo como objetivo la búsqueda, selección y caracterización de PGPB de los géneros Azotobacter, Azospirillum y Pseudomonas nativas de la rizósfera de cultivos de Ipomoea batatas de zonas productoras representativas del Caribe Colombiano. Los aislados seleccionados se caracterizaron molecularmente y realizaron pruebas de solubilización de fósforo, producción de índoles y reducción de acetileno. Las cepas fueron probadas a nivel de invernadero en plántulas de Ipomoea batatas producidas in vitro en las que se evaluó la altura, longitud radicular, masa seca de la parte aérea y radicular. Asociada a la rizósfera de Ipomoea batatas se obtuvieron cepas de Azotobacter vinelandii, Azotobacter chroococcum, Azospirillum lipoferum, Azospirillum brasilense y Pseudomonas denitrificans, las cepas fueron capaces de solubilizar fósforo, producir índoles y reducir acetileno. Se obtuvo incrementos en parámetros de crecimiento como longitud radicular, altura, peso seco aéreo y radicular en plántulas de Ipomoea batatas en invernadero con la inoculación de las bacterias seleccionadas frente a plántulas sin inocular. Los resultados catalogan a los aislados obtenidos como posibles microorganismos con potencial como biofertilizantes en batata.
Abstract The use of plant growth promoting Rhizobacteria (PGPR) is an alternative to replace chemical fertilizers for the cultivation of agricultural crops. The aim of this research was to search, selection and characterization of PGPR from the genus Azotobacter, Azospirillum and Pseudomonas natives from sweet potato (Ipomoea batatas) plants and rhizosphere of representative production regions of the Colombian Caribbean. Selected isolates were identified by molecular methods and they were screenedin vitrofor activities related to plant growth such as phosphate solubilization, indole production and acetylene reduction. The strains were tested in the greenhouse on plants of Ipomoea batatas produced in vitro. The height, root length, dry mass of the shot and root were evaluated. Associated with sweet potato crop us finded strains identificated as Azotobacter vinelandii, Azotobacter chroococcum, Azospirillum lipoferum, Azospirillum brasilense and Pseudomonas denitrificans. The strains were able to solubilize phosphate, synthesize indole-3-acetic acid (IAA) and reduce acetylene. The inoculation of bacteria selected increased growth parameters such as root length, height, dry weight root and shoot in plants of sweet potato in greenhouse. Those results catalog to the isolated obtained as possible microorganisms with potential as biofertilizers in sweet potato.
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Abstract Rhizosphere microorganisms and endophytes can help their hosts absorb nutrients and regulate the levels of plant hormones. Moreover, they can modulate the expressions of host genes, assist hosts in eliminating reactive oxygen species (ROS) and secreting volatile organic compounds. Therefore, rhizosphere microorganisms and endophytes are considered as determinant factors driving processes involved in the growth of host plants. However, the physiological and ecological functions, as well as the molecular mechanism underlying the behavior of rhizosphere microorganisms and endophytes in their role in the adaptive capacity of host plants in the karstic high-calcium environment have not been systematically studied. This review summarizes the physiological and molecular mechanisms of rhizosphere microorganisms and endophytes which help host plants to adapt to various kinds of adverse environments. The adaptive capacities of plants growing in adverse environments, partly, or totally, depends on microorganisms co-existing with the host plants.
Resumo Os microorganismos e endófitos da rizosfera podem ajudar seus hospedeiros a absorver nutrientes e regular os níveis de hormônios vegetais. Além disso, eles podem modular as expressões dos genes hospedeiros, auxiliar os hospedeiros na eliminação de espécies reativas de oxigênio (ROS) e secretar compostos orgânicos voláteis. Portanto, microorganismos e endófitos da rizosfera são considerados determinantes dos processos envolvidos no crescimento de plantas hospedeiras. No entanto, as funções fisiológicas e ecológicas, bem como o mecanismo molecular subjacente ao comportamento dos microrganismos e endofíticos da rizosfera no seu papel na capacidade adaptativa das plantas hospedeiras no ambiente cárstico de alto teor de cálcio, não foram sistematicamente estudados. Esta revisão resume os mecanismos fisiológicos e moleculares de microrganismos e endófitos da rizosfera que ajudam as plantas hospedeiras a se adaptarem a vários tipos de ambientes adversos. As capacidades adaptativas das plantas que crescem em ambientes adversos, em parte ou totalmente, dependem de microrganismos coexistentes com as plantas hospedeiras.
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Esta investigación tuvo como objetivo cuantificar bacterias diazótrofas y comparar fisicoquímicamente suelos rizosféricos de tres cacaotales (Theobroma cacao L.) del Departamento Norte de Santander, Colombia; para lo cual se caracterizaron, diferenciándose en área cultivada, manejo agronómico y edad del cultivo. A partir de diluciones seriadas de las muestras y empleando la técnica de Número Más Probable (NMP), en medios de cultivo semiselectivos (NFb, JMV, LGI, JNFb) semisólidos, se cuantificaron las diazótrofas, evaluando como positivo la formación de una película subsuperficial en el medio contenido en viales sellados; muestras pares se enviaron al laboratorio Bioambiental (UNET) para los análisis fisicoquímicos. Como resultado, las muestras evaluadas mostraron deficiencias en el porcentaje de materia orgánica y elementos como Potasio, Fósforo y Magnesio. Se reportaron estadísticamente diferencias altamente significativas en NMP. La mayor cuantificación de diazótrofas se reportó en la finca Florilandia, que se caracterizó por tener riego por goteo. La mayor cuantificación de diazotrófas se registró en los medios NFb y JMV, demostrándose una mayor presencia de los presuntos géneros Azospirillum sp. y Burkholderia sp. los cuales son fácilmente aislados de suelos rizosféricos, a diferencia de los géneros Herbaspirillum sp. y Gluconacetobacter sp. que por su carácter endófito suelen ser menos predominantes en este tipo de muestras. Se concluye además, que las características fisicoquímicas del suelo, la humedad y las relaciones climáticas al momento de la toma de las muestras, condicionan la cantidad de exudados de las raíces y por tanto son factores que condicionaron la presencia de diazótrofas en las muestras.
The objective of this research was to quantify diazotrophic bacteria and compare physicochemically rhizospheric soils of three cocoa plantations (Theobroma cacao L.) in Norte de Santander Department, Colombia; for which they were characterized, differing in cultivated area, agronomic management and crop age. From serial dilutions of the samples and using the technique of Most Probable Number (MPN), In semisolid culture media (NFb, JMV, LGI, JNFb), the diazotrophs were quantified, evaluating as positive the formation of a subsurface film in the medium contained in sealed vials; equal samples were sent to the Bioambiental laboratory (UNET) for physicochemical analyzes. As a result, the evaluated samples showed deficiencies in the percentage of organic matter and elements such as Potassium, Phosphorus and Magnesium. Statistically highly significant differences in MPN were reported. The highest quantification of diazotrophs was reported in the Florilandia farm, which was characterized by drip irrigation. The highest quantification of diazotrophs was recorded in the media NFb and JMV, demonstrating a greater presence of the presumed genera Azospirillum sp. and Burkholderia sp. which are easily isolated from rhizospheric soils, unlike the genera Herbaspirillum sp. and Gluconacetobacter sp. which by their endophytic character tend to be less predominant in this type of samples. It is also concluded that the physicochemical characteristics of the soil, humidity and climatic relationships at the moment of sampling, condition the amount of root exudates and therefore are factors that conditioned the presence of diazotrophs in the samples.
ABSTRACT
AbstractRhizosphere microbial communities are important for phytoremediation, plant nutrition, health and metabolism. Many factors, including plant species, pH and nutritional factors influence rhizosphere microbiology. In this study, we analysed the effects of different forms of nitrogen on the structures of rhizosphere microbial communities of E. crassipes. Using a conventional culture method with special media, bacteria, actinobacteria and molds were cultured. We found that the numbers of bacteria were largely similar across the three culture conditions, while the numbers of actinobacteria and molds from the rhizosphere of E. crassipes cultured in NH4Cl solution were two orders of magnitude higher than those from the rhizospheres of plants cultured in distilled water and KNO3 solution. Using a culture-independent method of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of 16S rDNA, we found that the form of nitrogen could influence the components of the rhizosphere microbial community. Pseudoxanthomonas, Enterobacter and Citrobacter were present in all of the samples cultured under the three different experimental conditions. The genus Reyranella was found only in samples cultured in KNO3 solution; Acinetobacter and Streptomyces were unique to samples cultured in NH4Cl solution, and Pseudomonas, Pseudacidovorax and Methylosinus were found only in samples cultured in distilled water. Pseudoxanthomonas and Acidovorax were the dominant genera in the rhizosphere microbial community of E. crassipes cultured in KNO3 solution, while Novosphingobium was the dominant genus in the sample cultured in a nitrogen-deficient medium. Our results provide a theoretical foundation for using E. crassipes as a phytoremediation plant and controlling the widespread distribution of E. crassipes around the world using principles of nutrient metabolism.
ResumenComunidades microbianas de la rizósfera son importantes para la fitorremediación, nutrición vegetal, salud y metabolismo. Muchos factores, incluyendo la especie de planta, el pH y los factores nutricionales influyen en la microbiología de la rizósfera. En este estudio, se analizaron los efectos de las diferentes formas del nitrógeno en la estructura de las comunidades microbianas de la rizósfera de E. crassipes. Mediante métodos de cultivo convencional con medios especiales se cultivaron: bacterias, actinobacterias y mohos. Se encontró que el número de bacterias era en gran parte similar a través de las tres condiciones de cultivo, mientras que el número de actinobacterias y mohos de la rizósfera de E. crassipes cultivadas en solución de NH4Cl era dos órdenes de magnitud superior a los de las rizósferas de plantas cultivadas en agua destilada y solución de KNO3. Utilizando un método de cultivo independiente de electroforesis en gel con gradiente de desnaturalización (PCR-DGGE) del ADNr 16S, se encontró que la forma de nitrógeno podría influir en los componentes de la comunidad microbiana de la rizósfera. Pseudoxanthomonas, Enterobacter y Citrobacter estaban presentes en todas las muestras cultivadas en las tres condiciones experimentales. El género Reyranella se encontró sólo en muestras cultivadas en solución de KNO3; Acinetobacter y Streptomyces eran las únicas muestras cultivadas en solución de NH4Cl, y Pseudomonas, Pseudacidovorax y Methylosinus se encontraron sólo en muestras cultivadas en agua destilada. Pseudoxanthomonas y Acidovorax eran los géneros dominantes en la comunidad microbiana de la rizósfera de E. crassipes cultivadas en solución de KNO3, mientras que Novos phingobium fue el género dominante en la muestra cultivada en un medio deficiente de nitrógeno. Nuestros resultados proporcionan una base teórica para el uso de E. crassipes como planta fitorremediadora y para controlar la distribución generalizada de E. crassipes en todo el mundo a través de los principios del metabolismo de nutrientes.
Subject(s)
Soil Microbiology , Bacteria/drug effects , Eichhornia/microbiology , Rhizosphere , Fungi/drug effects , Nitrogen/pharmacology , Polymerase Chain Reaction , Actinobacteria/drug effects , Denaturing Gradient Gel ElectrophoresisABSTRACT
El frailejón cuyo nombre científico es Espeletia spp., es considerado el arbusto emblema de los páramos, un ecosistema de importancia debido a que son fuente de agua y de materia orgánica, donde se han registrado un alto número de especies biológicas endémicas. Considerando la relevancia de la microbiota en la estructuración del suelo y en la disponibilidad de los nutrientes como soporte para el crecimiento vegetal, se determinaron las poblaciones microbianas cultivables de importancia funcional como dinamizadora de nutrientes en el suelo rizosférico de Espeletia spp. en el páramo de Santa Inés y en el de Frontino-Urrao en Antioquia. Los suelos se caracterizaron por ser ácidos y en el páramo de Frontino-Urrao se reportaron los mayores contenidos de materia orgánica y nitrógeno. La abundancia de microorganismos fue similar en los dos páramos y se registró únicamente variación en la abundancia de bacterias formadoras de endospora, que superaron en Frontino-Urrao 3,8 veces el contenido respecto al de Santa Inés. En ambos páramos se reportaron bacterias y hongos solubilizadores de fosfato y degradadores de celulosa que pueden ser empleados en procesos de restauración de suelos paramunos degradados por la minería, la ganadería o la agricultura.
The frailejón (Espeletia spp.) is the emblematic shrub of the paramo. This is an important ecosystem because they are sources of water and organic matter, and are inhabited by a high number of endemic biological species. Considering the importance of the microbiota in soil structure and nutrients availability to support plant growth, we assessed the cultivable microbial populations in Espeletia spp. rhizosphere in Santa Inés and Frontino-Urrao paramos, including functional groups with important role in cycling nutrients. The soil pH was strongly acid in both sites and the organic matter and nitrogen contents were highest in Frontino-Urrao soil. Nevertheless, the microbial abundance was similar in these sites except the content of endospore-forming bacteria, which was 3.8 fold large in Frontino-Urrao. Phosphate solubilizing and cellulolytic microorganisms were found in both sites. Those microorganisms would be used for soil restoration processes in paramos degraded by mining, livestock or agriculture.
ABSTRACT
RESUMOO objetivo desse trabalho foi verificar o efeito do solo pré-cultivado com plantas aromáticas na germinação e no desenvolvimento inicial de plântulas de alface cv. Simpson. A pesquisa foi realizada na Embrapa Hortaliças, Brasília, em bandejas mantidas em casa de vegetação. O experimento foi conduzido em delineamento experimental inteiramente casualizado, com três repetições e onze tratamentos: solo pré-cultivado com hortelã-comum (Mentha x villosa), hortelã-brava (Mentha arvensis), hortelã-pimenta (Mentha piperita), Mentha spp., capim-citronela (Cymbopogon winterianus), capim-limão (Cymbopogon citratus), manjericão de folha larga (Ocimum basilicum), manjericão de folha roxa (Ocimum gratissimun), tomilho (Thymus vulgaris), sálvia (Salvia officinalis) e solo da mesma área sem cultivo prévio de planta aromática (controle). Aos 30 dias após o semeio, foram avaliadas: índice de velocidade de emergência (IVE), taxa de sobrevivência (TS), número de folhas (NF), comprimento da raiz principal (CRP) e da parte aérea (CPA), massa fresca da raiz (MFR) e da parte aérea (MFPA) e massa seca da raiz (MSR) e da parte aérea (MSPA). Os dados foram submetidos à análise de variância e teste de Tukey a 5% de probabilidade. Houve diferença significativa em relação ao IVE, sendo que o tratamento com C. citratus afetou negativamente a emergência das plântulas. O tratamento com M. arvensis apresentou uma TS de apenas 16% das plantas aos 30 dias após a semeadura. O NF foi menor no tratamento com M. arvensis, diferentemente de todos os demais, exceto S. officinalis. A MRF e MFF foram estimuladas pelo tratamento com T. vulgaris sendo superior a todos os outros tratamentos. Os resultados obtidos permitem concluir que houve efeito negativo de M. arvensis e positivo de T. vulgaris no desenvolvimento inicial de plântulas de alface.
ABSTRACTThis study aimed to verify the outcomesof the soil previously treated with aromatic plants in the germination and early seedling growth of lettuce var. Simpson under greenhouse conditions. The trial was developed at Embrapa Vegetables, in Brasília, Brazil in a completely randomized design with three replications and composed by eleven treatments as follow: soil cultivated with apple-mint (Mentha x villosa), wild mint (Mentha arvensis), peppermint (Mentha piperita), Mentha spp., citronella (Cymbopogon winterianus), lemon grass (Cymbopogoncitratus), basil (Ocimum basilicum), african basil (Ocimum gratissimun), thyme (Thymus vulgaris), sage (Salvia officinalis) and soil from the same area without prior cultivation of aromatic plant (control). The emergence velocity index (IVE), the survival rate (SR), the number of leaves (NL), the length of the main root (CRP) and the shoot (CPA), the fresh mass of the root (MFR) and the shoot (MFPA) and the dry mass of the root (MSR) and the shoot (MSPA), were evaluated 30 days after the sowing. The data were submitted to analysis of variance and Tukey's test at 5% probability. There was a significant difference regarding the IVE, in which the treatment with C.citratus negatively affected seedlingappearance. The treatment with M. arvensis showeda TS of only 16%at 30 days after the sowing. The NF was lower in the treatment with M. arvensis, differently from all the others, excepting the cultivation withS. officinalis. The MFR and the MFPA were stimulated by the treatment with T. vulgaris, which was higher than all the other cultivations. The obtained results showed that M. arvensis had a negative influence,while T.vulgaris presented a positive outcome in the early development of lettuce seedlings.
Subject(s)
Plants, Medicinal/anatomy & histology , Soil Analysis , Lactuca/classification , Germination , Plant Exudates/analysis , Rhizosphere , AllelopathyABSTRACT
A fitoestimulação é uma das técnicas de fitorremediação que pode ser utilizada para a redução da concentração dos herbicidas no solo. Para tanto é necessário a seleção de plantas que estimulem a atividade dos microrganismos degradadores da rizosfera. O objetivo deste trabalho foi avaliar a biodegradação de cinco doses do herbicida composto pela mistura formulada de imazetapir+imazapique (75 + 25 g e.a. L-1) em solo rizosférico proveniente de seis espécies vegetais com potencial para a fitoestimulação. A biodegradação do herbicida nas doses de 0, 250, 500, 1.000 e 4.000mL ha-1 no solo rizosférico de Canavalia ensiformis, Glycine max, Lolium multiflorum, Lotus corniculatus, Stizolobium aterrimum, Vicia sativa e no solo sem cultivo foi avaliada através da quantificação da produção de C-CO2 do solo e da degradação do herbicida no solo por cromatografia líquida acoplada à espectrometria de massa. A produção de C-CO2 do solo após a contaminação com a mistura de imazetapir+imazapique foi maior nos solos rizosféricos das seis espécies vegetais se comparado ao solo não cultivado. O solo rizosférico de Stizolobium aterrimum apresentou a maior degradação do herbicida imazetapir nas maiores doses avaliadas, sendo uma espécie promissora para a fitoestimulação.
Phytostimulation is a technique of phytoremediation that can be used to reduce the concentration of herbicides in the soil. It is necessary to select plants that stimulate the activity of the rizosphere degrading microorganism. The aim of this study was to evaluate the activity of the biodegradation of the herbicide compound formulated mixture of imazethapyr + imazapic (75 + and 25 g L-1) in rhizosphere soil from six plant species with potential for phytostimulation. Biodegradation of the herbicide in the rhizosphere soil of Canavalia ensiformis, Glycine max, Lolium multiflorum, Lotus corniculatus, Stizolobium aterrimum and Vicia sativa, and a control (soil without plant) was evaluated at doses of 0, 250, 500, 1.000 and 4.000mL 1 ha, by quantifying the production of C-CO2 of the soil and the degradation of the herbicide from the soil by liquid chromatography coupled to mass spectrometry. The production of C-CO2 of the soil after the contamination with the mixture imazethapyr + imazapic was higher in the rhizosphere soil of the six plant species when compared to soil not cultivated. The rhizospheric soil from Stizolobium aterrimum shouwed the highest degradation of the herbicide imazetapyr on the highest doses evaluated, being a promising specie for phytostimulation.
ABSTRACT
Objetivo. El presente estudio consistió en caracterizar el porcentaje de colonización de hongos formadores de micorrizas arbusculares (HMA); asociados a la rizósfera del pasto Angleton (Dichanthium aristatum) Benth de fincas ganaderas del municipio de Tolú, departamento de Sucre, Colombia. Materiales y métodos. Se muestrearon en total 35 fincas ganaderas, de las cuales se tomaron 10 muestras de suelo con raíces por finca a una profundidad de 20 cm. De cada muestra se aislaron esporas de HMA, se hizo separación de morfotipos y su respectiva identificación a través de claves taxonómicas. De las raíces colectadas se determinó el porcentaje de colonización utilizando métodos de coloración. Resultados. Los ANAVA multifactorial entre las variables densidad de esporas/100 g de suelo y porcentaje de colonización en función a zonas y corregimiento mostraron diferencias altamente significativas. Los resultados obtenidos indican que el 92% de las especies encontradas corresponden a características de hongos HMA similares al género Glomus, el 4% al género Gigaspora y el 4% restante a Paraglomus. Conclusiones. Este estudio preliminar realizado en el Caribe colombiano muestra la diversidad, densidad poblacional y el porcentaje de colonización de HMA asociadas al pasto Angleton en condiciones de siete corregimientos pertenecientes a dos zonas agrológicas del municipio de Tolú, departamento de Sucre.
Objective. The present study was carried out to isolate, identify and determine the colonization rate of arbuscular mycorrhizal fungi (AMF) associated with rhizosphere of Dichanthium aristatum Benth grass, in livestock farms of the municipality of Tolú, department of Sucre. Materials and methods. Soil samples and roots from the different farms were picked up. Of each sample AMF spores were isolated, morphotype separation and identification was done by taxonomic keys. From the collected roots colonization rate were measured and calculated through staining methods. Results. 35 livestock farms were sampled, distributed throughout 7 areas of the municipality. The multifactorial ANOVA between the flux density of spores per 100 g soil and colonization percentage in terms of areas and farm factors showed highly significant differences. The results indicate that 92% of the species found are characteristic of fungi similar to the genus Glomus AMF, 4% to the genus Gigaspora, and the remaining 4% to ParaGlomus. Conclusions. This preliminary study carried out in the Colombian Caribbean shows diversity, population density and the percentage of colonization of HMA Associated to Angleton grass in conditions of seven townships belonging to two agrological areas of the municipality of Tolú, Department of Sucre.
Subject(s)
Animals , Dietary Fiber , Fungi , Mycorrhizae , RhizosphereABSTRACT
O uso de micro-organismos na agricultura é uma alternativa amplamente pesquisada e disseminada, que busca a diminuição no uso de fertilizantes químicos com consequente redução da degradação do meio ambiente. O objetivo deste trabalho foi avaliar a capacidade de solubilização de fosfato inorgânico (SFI) e o crescimento bacteriano em meio de cultura livre de fonte nitrogenada sob diferentes concentrações de NaCl de isolados bacterianos diazotróficos, associados a raízes de plantas de cana-de-açúcar. Foram avaliados 30 isolados, 15 endofíticos de raiz e 15 da rizosfera. A seleção de bactérias SFI foi realizada em meio sólido contendo fosfato insolúvel, avaliando-se o índice de solubilização (IS). Para a avaliação da influência de sal sobre o crescimento bacteriano em meio livre de nitrogênio, as bactérias foram cultivadas em meio NFb semi-sólido, acrescido de 0; 2,5; e 5% de NaCl. Foi possível observar que 90% dos isolados diazotróficos foram capazes de solubilizar fosfato inorgânico e que os isolados da rizosfera apresentaram os maiores IS. Quanto ao crescimento em meio NFb, foi observado que na ausência do sal todas as bactérias foram capazes de crescer. Contudo, 60% dos isolados foram capazes de crescer em meio NFb acrescido de 2,5% de NaCl e 17% em 5% de NaCl. Quando considerado o nicho do qual as bactérias foram isoladas, observou-se que as bactérias diferiram quanto à capacidade de crescer em meio NFb sob diferentes concentrações de NaCl. Os resultados permitem inferir que esses isolados bacterianos têm aplicações tecnológicas como promotores de crescimento vegetal, inclusive em solos salinos.
Subject(s)
Sodium Chloride , Saccharum , Fertilizers , Rhizosphere , NitrogenABSTRACT
Rizósfera de árboles acumuladores de fósforo en la amazonia Brasilera. Objetivo: Con el propósito de conocer estrategias de tolerancia de dos especies acumuladoras de fósforo (P) (Neea macrophylla y Cecropia palmate) y una no acumuladora (Casearia arborea) en suelos deficientes en fósforo, se buscó caracterizar la rizosfera de estas especies con análisis multivariado y matrices de correlación en lo referente a las concentraciones de P orgánico, de P disponible, de carbono (C) orgánico del suelo, de C orgánico de la biomasa microbiana, de actividad de la enzima fosfatasa ácida y de infección de la raíz por hongos micorrícicos. Materiales y métodos. La investigación fue desarrollada en el municipio de Igarapé-Açú, estado de Pará, Brasil en bosques secundarios con cinco años de regeneración, donde los parámetros arriba mencionados fueron monitoreados. Resultados. Los resultados no revelaron diferencias significativas entre las especies en referencia a las características del suelo próximo a las rizosferas, lo que sugiere homogeneidad de condiciones. La actividad enzimática fue ligeramente superior en la especie con menor potencial en acumular P (Casearia arborea), sugiriendo que la eficiencia del uso del P no está determinada por la actividad enzimática. Conclusiones. Neea macrophylla presentó un número ligeramente mayor de infecciones micorrícicas en comparación con las otras especies, indicando que ésta podría ser una estrategia de tolerancia en estos ambientes, mientras que para Cecropia palmata y Casearia arborea parece ser la actividad enzimática la estrategia usada...
Rhizosphere of tress that accumulate phosphorus in the Brazilian Amazon. Objective. With the purpose of knowing the strategies of tolerance of two phosphorus-accumulating species (Neea macrophylla and Cecropia palmate) and a non-accumulating species (Casearia arborea) to phosphorus-deficient soils, we characterized the rhizosphere of these species using a multivariate analysis and correlation matrices in relation to the concentrations of organic phosphorus, available phosphorus, soil organic carbon, organic carbon from microbial biomass, acid phosphatase enzyme activity, and root infection by mycorrhizal fungi. Materials and methods. The research was carried out in the Igarapé-Açú town, state of Pará, Brazil in secondary forests with five years of regeneration, where the parameters above mentioned were monitored. Results. Results did not reveal significant differences between the species depending on the characteristics of the soil next to the rhizospheres, suggesting homogeneous conditions. The enzymatic activity was slightly higher in the species with less potential in accumulating P (Casearia arborea) suggesting that efficiency in P use is not determined by the enzymatic activity. Conclusions. Neea macrophylla presented a slightly higher number of mycorrhizal root infections in comparison to the other species, indicating that this could be a tolerance strategy in those environments, while in Cecropia palmata and Casearia arborea it seems that enzymatic activity is the strategy employed...
Objetivo. Com a finalidade de conhecer possíveis estratégias de tolerância de duas espécies acumuladoras de fósforo (P), Neea macrophylla e Cecropia palmata e uma não acumuladora de P, Casearia arborea, a solos deficientes em P, esta pesquisa buscou caracterizar às rizosferas dessas espécies através de Análises Multivariadas e Matrizes de Correlação quanto às concentrações de P orgânico, P disponível, Carbono (C) orgânico do solo, C orgânico da Biomassa microbiana, Atividade da Enzima fosfatase Ácida e Infecção de Raízes por fungos micorrízicos. Materiais e métodos. A pesquisa se desenvolveu no Município de Igarapé-Açú, no estado do Pará, Brasil, em florestas secundárias com cinco anos de regeneração, onde os parâmetros acima comentados foram monitorados. Resultados. Os resultados revelaram não haver diferença significativa entre as espécies quanto as características do solo próximo às rizosferas sugerindo homogeneidade de condições. A atividade enzimática foi ligeiramente superior na espécie com menor potencial em acumular P, Casearia arborea, sugerindo que a eficiência de utilização de P não é determinada pela atividade enzimática. O grau de correlação entre as variáveis diferiu entre as espécies, sendo que Cecropia palmata melhor expressou a correlação positiva entre o P orgânico e Atividade da enzima fosfatase ácida. Conclusões. Neea macrophylla apresentou um número discretamente maior de infecções micorrízicas do que as outras espécies, sinalizando ser esta uma estratégia de tolerância nestes ambientes, enquanto para Cecropia palmata e, sobretudo Casearia arborea pareceu ser a atividade enzimática a estratégia usada.
Subject(s)
Acid Phosphatase , Rhizosphere , BrazilABSTRACT
This study evaluated the synergism between several P-solubilizing fungi isolates and arbuscular mycorrhizal fungi to improve clover ( Trifolium pratense) growth in the presence of Araxá apatite. Clover was sown directly in plastic pots with 300g of sterilized washed sand, vermiculite and sepiolite 1:1:1 (v:v:v) as substrate, and grown in a controlled environment chamber. The substrate was fertilized with 3 g L-1 of Araxá apatite. A completely randomized design, in 8×2 factorial scheme (eight P-solubilizing fungi treatments with or without arbuscular mycorrhizal fungi)and four replicates were used. The P-solubilizing fungi treatments consisted of five Brazilian P-solubilizing fungi isolates (PSF 7, 9, 20, 21 and 22), two Spanish isolates ( Aspergillus niger and the yeast Yarowia lipolytica) and control (non-inoculated treatment). The greatest clover growth rate was recorded when Aspergillus niger and PSF 21 were co-inoculated with arbuscular mycorrhizal fungi. Aspergillus niger, PSF 7 and PSF 21 were the most effective isolates on increasing clover growth in the presence of arbuscular mycorrhizal fungi. Greater mycorrhizal colonization resulted in greater clover growth rate in most PSF treatments. PSF 7 was the best isolate to improve the establishment of mycorrhizal and rhizobia symbiosis.
Este estudo avaliou o sinergismo entre diversos isolados defungos solubilizadores de fosfato e micorrízicos arbusculares para beneficiar o crescimento de trevo ( Trifolium pratense) na presença de apatita de Araxá. A cultura foi semeada diretamente em potes plásticos com 300 g de substrato esterilizado formado por areia lavada, vermiculita e sepiolita 1:1:1 (v:v:v) e cultivada em câmara climática. O substrato foi fertilizado com 3 g L-1 de apatita de Araxá. O experimento foi instalado em delineamento completamente casualizado, esquema fatorial 8×2 (oito tratamentos de inoculação de fungos solubilizadores de fosfato com ou sem fungos micorrízicos arbusculares) e quatro repetições. Os tratamentos de fungos solubilizadores de fosfato consistiram em cinco isolados brasileiros de fungos solubilizadores de fosfato (FSF 7, 9, 20, 21 e 22), dois isolados procedentes da Espanha ( Aspergillus niger e a levedura Yarowia lipolytica) e o controle (tratamento não inoculado). A maior taxa de crescimento da cultura foi obtida quando Aspergillus niger e FSF 21 foram co-inoculados com fungos micorrízicos arbusculares. Aspergillus niger, FSF 7 e o FSF 21 foram os isolados mais efetivos para incrementar o crescimento de trevo na presença de fungos micorrízicosarbusculares. A maior taxa de colonização micorrízica resultou em alta taxa de crescimento de trevo na maioria dos tratamentos com fungos solubilizadores de fosfato. O isolado FSF 7 foi o melhor para favorecer o estabelecimento das simbioses com fungos micorrízicos e com rizóbio.
Subject(s)
Fertilizers , Fungi/physiology , Medicago/growth & development , Medicago/drug effects , Mycorrhizae/physiology , Phosphorus , Solubility , SymbiosisABSTRACT
Plant-bacteria interactions result from reciprocal recognition between both species. These interactions are responsible for essential biological processes in plant development and health status. Here, we present a review of the methodologies applied to investigate shifts in bacterial communities associated with plants. A description of techniques is made from initial isolations to culture-independent approaches focusing on quantitative Polymerase Chain Reaction in real time (qPCR), Denaturing Gradient Gel Electrophoresis (DGGE), clone library construction and analysis, the application of multivariate analyses to microbial ecology data and the upcoming high throughput methodologies such as microarrays and pyrosequencing. This review supplies information about the development of traditional methods and a general overview about the new insights into bacterial communities associated with plants.
As interações planta-bactéria resultam de um reconhecimento recíproco de ambas espécies. Estas interações são responsáveis por processos biológicos essenciais para o desenvolvimento e a proteção das plantas. Este trabalho revisa as metodologias aplicadas na investigação de alterações nas comunidades bacterianas associadas às plantas. Uma descrição das técnicas é feita, desde o isolamento até a aplicação de técnicas independentes de cultivo, destacando as técnicas de qPCR, Gel de Eletroforese em Gradiente Desnaturante (DGGE), construção e análise de bibliotecas de clones, a aplicação de análise multivariada em dados de ecologia microbiana, e as novas metodologias de alto processamento de amostras como microarranjos e pirosequenciamento. Em resumo, esta revisão fornece informações sobre o desenvolvimento das técnicas tradicionais e uma visão geral sobre as novas tendências dos estudos de comunidades bacterianas associadas às plantas.
ABSTRACT
The genetic diversity of siderophore-producing bacteria of tobacco rhizosphere was studied by amplifiedribosomal DNA restriction analysis (ARDRA), 16S rRNA sequence homology and phylogenetics analysis methods. Studies demonstrated that 85% of the total 354 isolates produced siderophores in iron limited liquid medium. A total of 28 ARDRA patterns were identified among the 299 siderophore-producing bacterial isolates.The 28 ARDRA patterns represented bacteria of 14 different genera belonging to six bacterial divisions, namely β-, γ-, α-Proteobacteria, Sphingobacteria, Bacilli, and Actinobacteria. Especially, γ- Proteobacteria consisting of Pseudomonas, Enterobacter, Serratia, Pantoea, Erwinia and Stenotrophomonas genus encountered 18 different ARDRA groups. Results also showed a greater siderophore-producing bacterial diversity than previous researches. For example, Sphingobacterium (isolates G-2-21-1 and G-2-27-2), Pseudomonas poae (isolate G-2-1-1), Enterobacter endosymbiont (isolates G-2-10-2 and N-5-10), Delftia acidovorans (isolate G-1-15), and Achromobacter xylosoxidans (isolates N-46-11HH and N-5-20) were reported to be able to produce siderophores under low-iron conditions for the first time. Gram-negative isolates were more frequently encountered, with more than 95% total frequency. For Gram-positive bacteria, the Bacillus and Rhodococcus were the only two genera, with 1.7% total frequency. Furthermore, the Pseudomonas and Enterobacter were dominant in this environment, with 44.5% and 24.7% total frequency, respectively. It was also found that 75 percent of the isolates that had the high percentages of siderophore units (% between 40 and 60) belonged to Pseudomonas. Pseudomonas sp. G-229-21 screened out in this study may have potential to apply to low-iron soil to prevent plant soil-borne fungal pathogen diseases.
A diversidade genética de bactérias de rizosfera de tabaco produtoras de sideróforos foi estudada por meio da técnica de análise de restrição do DNA ribossomal amplificado (ARDRA), homologia de seqüência de 16s rRNA e métodos de análise filogenética. Observou-se que 85% do total de 354 isolados produziram sideróforos em meio liquido com restrição de ferro.Entre os 299 isolados produtores de sideróforos identificou-se 28 padrões ARDRA, que representaram 14 gêneros bacterianos diferentes, pertencentes a seis divisões bacterianas: β-, γ-, α-Proteobacteria, Sphingobacteria, Bacilli e Actinobacteria. γ- Proteobacteria, consistindo de Pseudomonas, Enterobacter, Serratia, Pantoea, Erwinia e Stenotrophomonas, pertenceram a 18 grupos ARDRA. Os resultados também mostraram uma diversidade maior de bactérias produtoras de sideróforos doque a relatada em outros estudos. Por exemplo, Sphingobacterium (isolados G-2-21-1 e G-2-27-2), Pseudomonaspoae (isolado G-2-1-1), Enterobacter endosymbiont (isolados G-2-10-2 e N-5-10), Delftia acidovorans (isolado G-1-15) e Achromobacter xylosoxidans (isolados N-46-1HH e N-5-20), capazes de produzir sideróforos em condições de baixa disponibilidade de ferro, foram relatados pela primeira vez. Isolados Gram negativos foram encontrados com maior freqüência, correspondendo a mais de 95% da freqüência total. Entre as bactérias Gram positivas, foram encontrados apenas os gêneros Bacillus e Rhodococcus, com 1,7% da freqüência total. Além disso, neste ambiente houve predominância de Pseudomonas e Enterobacter, com 44,5% e 24,7% da freqüência total, respectivamente. Verificou-se também que 75% dos isolados com alta porcentagem de unidades de sideróforos (% entre 40 e 60) pertenceram a Pseudomonas. Pseudomonas sp. G- 229-21, selecionado neste estudo, apresenta potencial de aplicação em solos com baixo teor de ferro para prevenção dedoenças fúngicas em plantas.