Endophytic bacteria promote growth and increase the aloin content of Aloe vera / Las bacterias endofíticas promueven el crecimiento y aumentan el contenido de aloína del Aloe vera

Aloe vera is among the world's economically most important medicinal plants, but as the growth of this plant and, consequently, the accumulation of metabolites is slow, we tested the hypothesis that root endophytic bacteria isolated from A. vera plants can promote growth and increase the accumulation of aloin in the gel and latex. For this, we inoculate seedlings with four endophytic bacteria and a combination of them. We confirmed the hypothesis and identified two strains with potential for the formulation of inoculants to improve the cultivation of A. vera. The bacterium 149H Paraburkholderiasp. increases the number of leaves and the accumulation of biomass, but on the other hand, 35V Enterobacter ludwigii inoculation increased the content of aloin in the gel and in the latex. Further research should focus on the association of these two strains in a single inoculant, to both promote growth and increase the synthesis of metabolites.

Aloe vera se encuentra entre las plantas medicinales económicamente más importantes del mundo, pero como el crecimiento de esta planta y, en consecuencia, la acumulación de metabolitos es lento, probamos la hipótesis de que las bacterias endofíticas de raíces aisladas de las plantas de A. vera pueden promover el crecimiento y aumentar la acumulación de aloína en el gel y látex. Para ello, inoculamos plántulas con cuatro bacterias endofíticas y una combinación de ellas. Confirmamos la hipótesis e identificamos dos cepas con potencial para la formulación de inoculantes para mejorar el cultivo de A. vera. La bacteria 149H Paraburkholderia sp. aumenta el número de hojas y la acumulación de biomasa, pero, por otro lado, la inoculación con Enterobacter ludwigii 35V aumentó el contenido de aloína en el gel y en el látex. La investigación adicional debe centrarse en la asociación de estas dos cepas en un solo inoculante, tanto para promover el crecimiento como para aumentar la síntesis de metabolitos

Combining Ability for Resistance to White Mold in a Diallel Cross of Soybean

Abstract The white mold, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is one of the most important diseases of soybean. The objective of the present work was to evaluate the soybean reaction to the fungus S. sclerotiorum, which causes white mold, in a partial diallel with 50 crosses. The Group I of parents was composed of ten experimental lines with high grain yield and the group II consisted in five genotypes with possible resistance to white mold. Ten plants of each cross in the F4 generation and the parents were evaluated for reaction to fungus infection using the method of inoculation in detached leaves in order to assess the severity of the disease and to later estimate the combining abilities. Estimates of the specific combining ability (SCA) was a significant reaction to S. sclerotiorum, indicating that there is variability for fungus resistance due to non-additive genes action.

Changes induced by co-inoculation in nitrogen-carbon metabolism in cowpea under salinity stress

ABSTRACT To mitigate the deleterious effects of abiotic stress, the use of plant growth-promoting bacteria along with diazotrophic bacteria has been increasing. The objectives of this study were to investigate the key enzymes related to nitrogen and carbon metabolism in the biological nitrogen fixation process and to elucidate the activities of these enzymes by the synergistic interaction between Bradyrhizobium and plant growth-promoting bacteria in the absence and presence of salt stress. Cowpea plants were cultivated under axenic conditions, inoculated with Bradyrhizobium and co-inoculated with Bradyrhizobium sp. and Actinomadura sp., Bradyrhizobium sp. and Bacillus sp., Bradyrhizobium sp. and Paenibacillus graminis, and Bradyrhizobium sp. and Streptomycessp.; the plants were also maintained in the absence (control) and presence of salt stress (50 mmolL-1 NaCl). Salinity reduced the amino acids, free ammonia, ureides, proteins and total nitrogen content in nodules and increased the levels of sucrose and soluble sugars. The co-inoculations responded differently to the activity of glutamine synthetase enzymes under salt stress, as well as glutamate synthase, glutamate dehydrogenase aminating, and acid invertase in the control and salt stress. Considering the development conditions of this experiment, co-inoculation with Bradyrhizobium sp. and Bacillus sp. in cowpea provided better symbiotic performance, mitigating the deleterious effects of salt stress.

Genomic identification and characterization of the elite strains Bradyrhizobium yuanmingense BR 3267 and Bradyrhizobium pachyrhizi BR 3262 recommended for cowpea inoculation in Brazil

ABSTRACT The leguminous inoculation with nodule-inducing bacteria that perform biological nitrogen fixation is a good example of an "eco-friendly agricultural practice". Bradyrhizobium strains BR 3267 and BR 3262 are recommended for cowpea (Vigna unguiculata) inoculation in Brazil and showed remarkable responses; nevertheless neither strain was characterized at species level, which is our goal in the present work using a polyphasic approach. The strains presented the typical phenotype of Bradyrhizobium with a slow growth and a white colony on yeast extract-mannitol medium. Strain BR 3267 was more versatile in its use of carbon sources compared to BR 3262. The fatty acid composition of BR 3267 was similar to the type strain of Bradyrhizobium yuanmingense; while BR 3262 was similar to Bradyrhizobium elkanii and Bradyrhizobium pachyrhizi. Phylogenetic analyses based on 16S rRNA and three housekeeping genes placed both strains within the genus Bradyrhizobium: strain BR 3267 was closest to B. yuanmingense and BR 3262 to B. pachyrhizi. Genome average nucleotide identity and DNA-DNA reassociation confirmed the genomic identification of B. yuanmingense BR 3267 and B. pachyrhizi BR 3262. The nodC and nifH gene analyses showed that strains BR 3267 and BR 3262 hold divergent symbiotic genes. In summary, the results indicate that cowpea can establish effective symbiosis with divergent bradyrhizobia isolated from Brazilian soils.

Rizobacterias promotoras de crecimiento en Guarianthe skinneri (Orchidaceae) / Growth-promoting rhizobacteria from Guarianthe skinneri (Orchidaceae)

Resumen La orquídea Guarianthe skinneri está incluida en la norma NOM-059-ECOL-2010 de México como una especie amenazada. Con el fin de estudiar las BPCV (bacterias promotoras del crecimiento vegetal) en esta orquídea, se recolectaron 10 raíces de diferentes plantas para aislar bacterias asociadas a las raíces, que se analizaron mediante pruebas in vitro como: producción de AIA, fijación de nitrógeno, interacción con el hongo micorrízico Thanatephorus sp. cepa RG26 y solubilización de fosfato. De los 71 aislados bacterianos se caracterizaron 10 cepas mediante secuenciación con el marcador 16s rADN y se identificaron seis cepas: Sphingomonas sp., Sinorhizobium sp., Bacillus sp., Nocardia cerradoensis, Bacillus megaterium y Burkholderia phytofirmans. Se observó que la bacteria Sinorhizobium sp. produjo mayor cantidad de AIA (69.189 µg/ml) y Bacillus sp. presentó mayor reducción de acetileno (10.251 nmol cultivo/96 h). En las interacciones de las bacterias y el hongo RG26 se presentaron cuatro categorías (sumamente positivo, positivo, antagonismo 50-50 e inhibición). En relación a la solubilización de fosfato, la bacteria Burkholderia phytofirmans presentó mayor IS a las 48 y 96 hr con IS de 3.11 y 3.48, respectivamente. Los resultados indican que Bacillus sp. pudiera tener las mejores características para promover el desarrollo de la orquídea G. skinneri mediante la inoculación de semillas y plántulas.

Abstract The Guarianthe skinneri orchid is included in NOM-059-ECOL-2010, Mexico standard as an endangered species. In order to study PGPR (promoting growth plant rhizobacteria) from this orchid, 10 roots were collected from different plants to isolate bacteria associated with the roots, which were analyzed by in vitro tests such as: production of AIA, nitrogen fixation, interaction with the mycorrhizal fungus Thanatephorus sp. strain RG26 and phosphate solubilization. We obtain 71 bacterial isolates, 10 strains of them were characterized by sequencing with the 16d rDNA marker identifying six bacteria: Sphingomonas sp. Sinorhizobium sp. Bacillus sp. Nocardia cerradoensis, Bacillus megaterium and Burkholderia phytofirmans. We observed that the bacterium Sinorhizobium sp. produced a greater amount of AIA (69.189 μg/ml) and Bacillus sp. performed greater acetylene reduction (10.251 nmol cultivo/96h). In the interactions of the bacteria and the fungus RG26, four categories were presented (extremely positive, positive, antagonism 50-50 and inhibition). In relation to the solubilization of phosphate, Burkholderia phytofirmans presented higher IS after 48 and 96 hr with an IS of 3.11 and 3.48, respectively. The results indicate that Bacillus sp. it could have the best characteristics to promote the development of the G. skinneri orchid by inoculating seeds and seedlings. Rev. Biol. Trop. 66(3): 953-968. Epub 2018 September 01.

Antioxidant response of cowpea co-inoculated with plant growth-promoting bacteria under salt stress

Abstract Soil salinity is an important abiotic stress worldwide, and salt-induced oxidative stress can have detrimental effects on the biological nitrogen fixation. We hypothesized that co-inoculation of cowpea plants with Bradyrhizobium and plant growth-promoting bacteria would minimize the deleterious effects of salt stress via the induction of enzymatic and non-enzymatic antioxidative protection. To test our hypothesis, cowpea seeds were inoculated with Bradyrhizobium or co-inoculated with Bradyrhizobium and plant growth-promoting bacteria and then submitted to salt stress. Afterward, the cowpea nodules were collected, and the levels of hydrogen peroxide; lipid peroxidation; total, reduced and oxidized forms of ascorbate and glutathione; and superoxide dismutase, catalase and phenol peroxidase activities were evaluated. The sodium and potassium ion concentrations were measured in shoot samples. Cowpea plants did not present significant differences in sodium and potassium levels when grown under non-saline conditions, but sodium content was strongly increased under salt stress conditions. Under non-saline and salt stress conditions, plants co-inoculated with Bradyrhizobium and Actinomadura or co-inoculated with Bradyrhizobium and Paenibacillus graminis showed lower hydrogen peroxide content in their nodules, whereas lipid peroxidation was increased by 31% in plants that were subjected to salt stress. Furthermore, cowpea nodules co-inoculated with Bradyrhizobium and plant growth-promoting bacteria and exposed to salt stress displayed significant alterations in the total, reduced and oxidized forms of ascorbate and glutathione. Inoculation with Bradyrhizobium and plant growth-promoting bacteria induced increased superoxide dismutase, catalase and phenol peroxidase activities in the nodules of cowpea plants exposed to salt stress. The catalase activity in plants co-inoculated with Bradyrhizobium and Streptomyces was 55% greater than in plants inoculated with Bradyrhizobium alone, and this value was remarkably greater than that in the other treatments. These results reinforce the beneficial effects of plant growth-promoting bacteria on the antioxidant system that detoxifies reactive oxygen species. We concluded that the combination of Bradyrhizobium and plant growth-promoting bacteria induces positive responses for coping with salt-induced oxidative stress in cowpea nodules, mainly in plants co-inoculated with Bradyrhizobium and P. graminis or co-inoculated with Bradyrhizobium and Bacillus.

Valor nutritivo da Coastcross-1 inoculada com Azospirillum brasilense / Nutritive value of Coastcross-1 inoculated with Azospirillum brasilense

Objetivou-se com este trabalho avaliar a taxa de produção de forragem e o valor nutritivo da Coastcross-1, inoculada com Azospirillum brasilense, fertilizada com diferentes doses de N e submetida ao regime de corte. O delineamento experimental foi o de blocos ao acaso, com três repetições, em esquema fatorial. Os fatores foram o uso da inoculação (não inoculada, inoculada somente no plantio e reinoculada no segundo ano), níveis de N (0, 100 e 200kg/ha/ano de N) e os períodos do ano. Avaliaram-se a taxa de produção e a composição botânica da forragem, a composição morfológica, o teor de proteína bruta, a digestibilidade in situ da matéria orgânica e os nutrientes digestíveis totais da Coastcross-1. A inoculação, quando não associada ao adubo nitrogenado, ocasionou aumento na taxa de produção de forragem, na participação da Coastcross-1 e na produção de nutrientes digestíveis totais. Houve redução nos teores de proteína bruta da Coastcross-1, quando a gramínea adubada com 200kg/ha/ano de N foi inoculada. A inoculação tem efeito positivo na Coastcross-1 não submetida à adubação nitrogenada.(AU)

The objective of this study was to evaluate the forage yield rate and nutritive value of Coastcross-1 inoculated with Azospirillum brasilense and fertilized with different levels of nitrogen subjected to cut. The experimental design was randomized blocks with three replications, in a factorial scheme. The factors were the inoculation (without inoculation, inoculated just in the implantation and reinoculated in the second year), levels of nitrogen (0, 100 and 200kg/ha/year of N) and periods of the year. Forage yield rate and botanical composition; morphological composition, crude protein content, in situ digestibility of organic matter and the total digestible nutrients of Coastcross-1 were evaluated. Inoculation increased the forage yield rate, Coastcross-1 contribution and production of total digestible nutrients, when the pasture was not fertilized with N. There was reduction in Coastcross-1 crude protein content when fertilized with 200kg/ha/yr of N. The inoculation has a positive effect on Coastcross-1 not submitted to nitrogen fertilization.(AU)

Efecto de inoculantes bacterianos edáficos mixtos en el desarrollo temprano de cultivares mejorados de cacao (Theobroma cacao L.) en un sistema agroforestal tradicional del norte de Oaxaca, México / Effect of mixed edaphic bacterial inoculants in the early development of improved cocoa cultivars (Theobroma cacao L.) in a traditional agroforestry system of Oaxaca, Mexico

El cacao (Theobroma cacao L.) es nativo de América del Sur y representa uno de los recursos «bioculturales¼ más significativos de Mesoamérica, ya que es una región donde se domesticó y tuvo relevancia como bebida ritual y como moneda en muchas culturas prehispánicas hasta la llegada de los españoles, quienes difundieron su uso en el mundo y lo convirtieron en una de las mercancías «commodity¼ más consumidas. Mediante este trabajo se propone una alternativa para atender la problemática de las plantaciones a través de la introducción de una diversidad amplia de cultivares de cacao en sistemas agroforestales tradicionales, en sinergia con la inoculación de bacterias edáficas fijadoras de nitrógeno y solubilizadoras de fósforo insoluble. En una parcela agroforestal tradicional se introdujeron plantas de cacao injertadas de cuatro cultivares y se dispusieron 3 tratamientos: aplicación de biofertilizante, aplicación de fertilizante químico y testigo. Se registraron la altura, el diámetro basal, el número de hojas y el número de ramas a los 2 y 12 meses, y se caracterizó la población de microorganismos asociada alrededor del tallo bajo la copa de las plantas. Los resultados de crecimiento muestran un buen potencial para los 4 cultivares estudiados y se observó que la biofertilización generó efectos significativos en algunos de los indicadores de crecimiento de las plantas de cacao. Así, las asociaciones vegetales en un sistema agroforestal podrían ser favorables para potenciar el desarrollo de frutos y resistencia a plagas y enfermedades.

Cocoa plant (Theobroma cacao L.) is native from South America and it represents one of the most significant "bio-cultural" resources of Mesoamerica, since it is a region where it was domesticated and had a relevance as ritual drink and as currency in many pre-hispanic cultures until the arrival of the Spaniards who spread its use worldwide, and became it one of the most consumed commodity goods. Through this research, an alternative is proposed to address the problem of cultivars through the introduction of a wide variety of cocoa plants in traditional agroforestry systems, in synergy with the inoculation of nitrogen-fixing and insoluble phosphor solubilizing edaphic bacterial consortia. Four cultivars of improved grafted cocoa plants were introduced in a traditional agroforestry plot and three fertilization treatments were applied: application of biofertilizer, application of chemical fertilizer and control. Measurements of height, stem diameter, number of leaves and branches were recorded at 2 and 12 months after planting and rhizosphere microbial populations were characterized. Growth results showed good potential for all studied cultivars and it was observed that biofertilization foresees significant effects in some of the growth indicators of cocoa plant. Thereby, plant associations in an agroforestry system could be favorable to promote fruit development and resistance to pests and diseases.

Promotion of iron nutrition and growth on peanut by Paenibacillus illinoisensis and Bacillus sp. strains in calcareous soil

ABSTRACT This study aimed to explore the effects of two siderophore-producing bacterial strains on iron absorption and plant growth of peanut in calcareous soil. Two siderophore-producing bacterial strains, namely, YZ29 and DZ13, isolated from the rhizosphere soil of peanut, were identified as Paenibacillus illinoisensis and Bacillus sp., respectively. In potted experiments, YZ29 and DZ13 enhanced root activity, chlorophyll and active iron content in leaves, total nitrogen, phosphorus and potassium accumulation of plants and increased the quality of peanut kernels and plant biomass over control. In the field trial, the inoculated treatments performed better than the controls, and the pod yields of the three treatments inoculated with YZ29, DZ13, and YZ29 + DZ13 (1:1) increased by 37.05%, 13.80% and 13.57%, respectively, compared with the control. Based on terminal restriction fragment length polymorphism analysis, YZ29 and DZ13 improved the bacterial community richness and species diversity of soil surrounding the peanut roots. Therefore, YZ29 and DZ13 can be used as candidate bacterial strains to relieve chlorosis of peanut and promote peanut growth. The present study is the first to explore the effect of siderophores produced by P. illinoisensis on iron absorption.

Agronomic efficiency of Rhizobium strains from the Amazon region in common bean / Eficiência agronômica de estirpes de Rhizobium isoladas da Amazônia sobre o feijoeiro-comum

To maximize the contribution of biological nitrogen fixation in common bean, it is necessary to use bacterial strains that are more adapted, competitive, and efficient in the symbiotic process. In this regard, the aim of this study was to evaluate the agronomic efficiency (AE) of three bacterial strains isolated from acid soils with high Al content from the Amazon region in an Argissolo Vermelho Distrófico típico soil (Typic Rhodustults - USDA Classification) from the municipality of Formiga, MG, Brazil. We compared their AE to that of the reference strain CIAT 899T and of two controls without inoculation (one without and another with 80 kg ha-1 of N-urea). The results indicated that inoculation with the strains UFLA 02-100 and UFLA 02-127 provides grain yield equivalent to inoculation with the reference strain and to the control with mineral N. Thus, both have potential for recommendation as inoculants for common bean.

Para maximizar a contribuição da fixação biológica de nitrogênio no feijoeiro-comum é necessária a utilização de estirpes de bactérias mais adaptadas, competitivas e eficientes no processo simbiótico. Nesse sentido, objetivou-se avaliar, em um Argissolo Vermelho Distrófico típico do município de Formiga-MG, a eficiência agronômica (EA) de três estirpes isoladas de solos ácidos e com alto teor de Al da Amazônia e comparar suas EA à da estirpe referência CIAT 899T e à de dois controles sem inoculação (um sem e outro com 80 kg ha-1 of N-ureia). Os resultados indicaram que a inoculação com as estirpes UFLA 02-100 e UFLA 02-127 propicia rendimento de grãos equivalente ao da estirpe referência e ao do controle com N mineral e que por isso, ambas têm potencial para ser recomendadas como inoculantes para o feijoeiro-comum.

Aislados de Bacillus provenientes de la rizósfera de cactus incrementan la germinación y la floración en Mammillaria spp. (Cactaceae) / Bacillus isolates from rhizosphere of cacti improve germination and bloom in Mammillaria spp. (Cactaceae)

Las cactáceas son la vegetación característica de las zonas áridas en México, donde las lluvias son escasas, la evapotranspiración es elevada y la fertilidad de los suelos es baja. Las plantas han desarrollado estrategias fisiológicas como la asociación con microorganismos en la zona de la rizósfera para incrementar la captación de nutrientes. En el presente trabajo se obtuvieron 4 aislados bacterianos de la rizósfera de Mammillaria magnimamma y Coryphantha radians, los que fueron nombrados como QAP3, QAP19, QAP22 y QAP24 e identificados genéticamente como pertenecientes al género Bacillus. Estos aislados exhibieron in vitro propiedades bioquímicas como solubilización de fosfatos, producción de ácido indolacético y actividad ACC deaminasa, que se relacionan con la promoción del crecimiento de las plantas. Dicha promoción fue ensayada inoculando semillas de M. magnimamma y evaluando luego algunos parámetros. Se encontró que todos los aislados incrementaron la germinación desde un 17% hasta un 34,3% (con respecto a las semillas testigo sin inocular); el aislado QAP24 fue el que presentó el mayor efecto en este sentido y permitió la germinación de todas las semillas viables (84,7%) 3 días antes que en el testigo. La inoculación de este aislado en plantas de Mammillaria zeilmanniana mostró un efecto positivo sobre la floración: en 2 meses dentro del período de un año se detectó un incremento en el número de plantas en floración con respecto a las plantas testigo, de hasta el 31,0% en uno de ellos. Se concluye que los aislados de Bacillus spp. caracterizados poseen potencial para ser empleados en programas de conservación de especies vegetales de zonas áridas.

Cacti are the most representative vegetation of arid zones in Mexico where rainfall is scarce, evapotranspiration is high and soil fertility is low. Plants have developed physiological strategies such as the association with microorganisms in the rhizosphere zone to increase nutrient uptake. In the present work, four bacterial isolates from the rhizosphere of Mammillaria magnimamma and Coryphantha radians were obtained and named as QAP3, QAP19, QAP22 and QAP24, and were genetically identified as belonging to the genus Bacillus, exhibiting in vitro biochemical properties such as phosphate solubilization, indoleacetic acid production and ACC deaminase activity related to plant growth promotion, which was tested by inoculating M. magnimamma seeds. It was found that all isolates increased germination from 17 to 34.3% with respect to the uninoculated control seeds, being QAP24 the one having the greatest effect, accomplishing the germination of viable seeds (84.7%) three days before the control seeds. Subsequently, the inoculation of Mammillari zeilmanniana plants with this isolate showed a positive effect on bloom, registering during two months from a one year period, an increase of up to 31.0% in the number of flowering plants compared to control plants. The characterized Bacillus spp. isolates have potential to be used in conservation programs of plant species from arid zones.

Induction of in vitro shoots of Billbergia euphemiae E. Morren (Bromeliaceae) from leaf explants / Indução in vitro de brotos de Billbergia euphemiae E. Morren (Bromeliaceae) a partir de explantes foliares

Bromeliads are an important group for the maintenance of the Atlantic Forest, with many threatened species due to exacerbated extraction and destruction of their natural habitats. Considering the need of developing protocols for the conservation of these species, the aim of this work was to evaluate the effect of different growth regulators in the in vitro induction of shoots of Billbergia euphemiae. Leaf explants were excised from seedlings derived from in vitro germination and grown on MS medium supplemented with NAA (0, 1 or 2 µM) and BA (0, 2, 4 or 6 µ M) combinations. The evaluation of the number of shoots per explant, shoot length, number of leaves per shoot and longest leaf length average was carried out after 30 and 60 days of culture. The best in vitro responses were observed in the presence of 1 µM NAA after 60 days of culture, which induced the best production of shoots per explant (16.39), as well as the highest rates of shoot length (1.08 cm), number of leaves per shoot (5.00) and the longest leaf length (0.56 cm). This work determined the best conditions for shoot production from leaf explants of B. euphemiae, being the first report on micropropagation of this species.

As bromélias constituem um importante grupo para a manutenção da Floresta Atlântica, com várias espécies ameaçadas de extinção pelo extrativismo exacerbado e a destruição dos habitats naturais. Considerando a necessidade do desenvolvimento de protocolos para a conservação destas espécies, este trabalho teve como objetivo avaliar o efeito de diferentes reguladores de crescimento na indução de brotos de Billbergia euphemiae. Explantes foliares foram excisados de plântulas derivadas da germinação in vitro e inoculados em meio MS suplementado com combinações de ANA (0, 1 ou 2 µM) e BA (0, 2, 4 ou 6 µM). O número de brotos por explantes, comprimento dos brotos, número médio de folhas por broto e comprimento médio da maior folha foram avaliados após 30 e 60 dias de cultura. As melhores respostas foram observadas na presença de ANA a 1 µM, após 60 dias de cultura, que induziu a maior produção de brotos por explante (16,39), assim como as maiores taxas de comprimento dos brotos (1,08 cm), número médio de folhas por broto (5,00) e comprimento da maior folha (0,56 cm). Este trabalho determinou as melhores condições para produção de brotos de B. euphemiae a partir de explantes foliares, representando o primeiro relato de micropropagação desta espécie.

Interrogantes en la tecnología de la inoculación de semillas de soja con Bradyrhizobium spp / Queries related to the technology of soybean seed inoculation with Bradyrhizobium spp

With the aim of exploiting symbiotic nitrogen fixation, soybean crops are inoculated with selected strains of Bradyrhizobium japonicum, Bradyrhizobium diazoefficiens or Bradyrhizobium elkanii (collectively referred to as Bradyrhizobium spp.). The most common method of inoculation used is seed inoculation, whether performed immediately before sowing or using preinoculated seeds or pretreated seeds by the professional seed treatment. The methodology of inoculation should not only cover the seeds with living rhizobia, but must also optimize the chances of these rhizobia to infect the roots and nodulate. To this end, inoculated rhizobia must be in such an amount and condition that would allow them to overcome the competition exerted by the rhizobia of the allochthonous population of the soil, which are usually less effective for nitrogen fixation and thus dilute the effect of inoculation on yield. This optimization requires solving some queries related to the current knowledge of seed inoculation, which are addressed in this article. I conclude that the aspects that require further research are the adhesion and survival of rhizobia on seeds, the release of rhizobia once the seeds are deposited in the soil, and the movement of rhizobia from the vicinity of the seeds to the infection sites in the roots

Con el fin de aprovechar la fijación simbiótica de nitrógeno, el cultivo de soja se inocula con cepas seleccionadas de Bradyrhizobium japonicum, Bradyrhizobium diazoefficiens o Bradyrhizobium elkanii (conjuntamente referidas como Bradyrhizobium spp.). El método más común de hacerlo es la inoculación en semillas, ya sea que esta se realice en el momento previo a la siembra o que se utilicen semillas preinoculadas o pretratadas mediante el tratamiento profesional de semillas. La metodología de inoculación no debe limitarse a recubrir las semillas con rizobios vivos, sino que también debe optimizar las chances de esos rizobios para infectar las raíces y nodular. Para ello los rizobios inoculados deben estar en una cantidad y un estado tales que les permitan superar la competición ejercida por los rizobios de la población alóctona del suelo, los cuales usualmente son menos eficaces para la fijación de nitrógeno y así diluyen el efecto de la inoculación sobre el rendimiento. Esta optimización requiere resolver algunos interrogantes, que son abordados en el presente artículo. Concluyo que los aspectos que requieren más investigación son la adhesión y supervivencia de los rizobios en las semillas, la liberación de los rizobios una vez que las semillas se depositan en el suelo y el movimiento de los rizobios desde las inmediaciones de las semillas hasta los sitios de infección en las raíces

Bioprospection of marine microorganisms: biotechnological applications and methods

Bioprospección de microorganismos marinos: aplicaciones biotecnológicas y métodos. Los microorganismos ambientales constituyen una reserva prácticamente inagotable de diversidad genética, acumulada durante millones de años de evolución adaptativa a varias presiones selectivas. En particular, la magnitud de la biodiversidad microbiana en hábitats marinos parece crecer al emerger nuevas técnicas para medirla. Como resultado, se han comenzado a utilizar enfoques novedosos y más complejos para la búsqueda de moléculas y actividades de interés biotecnológico en estos ambientes. En este artículo de revisión, nosotros exploramos los diferentes campos de la biotecnología que utilizan microorganismos, los cuales se superponen parcialmente, y describimos los diferentes hábitats marinos que resultan particularmente atractivos para la bioprospección. Además, revisamos los enfoques metodológicos actualmente utilizados para la bioprospección microbiana, desde las técnicas de cultivo tradicionales hasta modernos enfoques metagenómicos, con énfasis en el medio ambiente marino.

Environmental microorganisms constitute an almost inexhaustible reserve of genetic and functional diversity, accumulated during millions of years of adaptive evolution to various selective pressures. In particular, the extent of microbial biodiversity in marine habitats seems to grow larger as new techniques emerge to measure it. This has resulted in novel and more complex approaches for the screening of molecules and activities of biotechnological interest in these environments. In this review, we explore the different partially overlapping biotechnological fields that make use of microorganisms and we describe the different marine habitats that are particularly attractive for bioprospection. In addition, we review the methodological approaches currently used for microbial bioprospection, from the traditional cultivation techniques to state of the art metagenomic approaches, with emphasis in the marine environment.

effects of Lactobacillus plantarum on chemical composition, rumen degradability, in vitro gas production and energy content of whole-plant corn ensiled at different stages of maturity

This study was carried out to determine the effects of Lactobacillus plantarum on chemical composition and nutritive value of whole-plant corn [WPC] ensiled at different stages of maturity. Based on local routine practice, WPC was harvested at three stages of maturity as follows: [1] two weeks before routine harvesting time; [2], one week before routine harvesting time and [3], routine harvesting time. Bacterial inoculant [Ecosyl] was used as homofermentive lactic acid bacteria. The inoculant was applied at the recommended level of 1 x 10[5] CFu/g of fresh forage which was ensiled for 25 days in plastic polyethylene bags. Three untreated silages were prepared for each harvesting time and considered as controls [C]. At the end of the ensiling period, all silages were subjected to chemical analysis, DM degradability and in vitro gas production. All silages underwent good fermentation and pH values decreased to below 4. WPC ensiled one week before routine harvesting time and treated with bacterial inoculant, had the lowest pH, ADF [P<0.05] content and the highest CP content, total gas production, IVOMD, DOMD [P<0.05], ME [P<0.05], fraction "a" [P<0.05] and ED [P<0.05] compared with other treatments. The results indicated that application of bacterial inoculant [Lactobacillus plantarum] at the recommended level to WPC harvested at one week before routine harvesting time was more effective in enhancing chemical composition and nutritive value of silages, and provide a well-preserved and high nutritive value feedstuff for ruminants

Growth response of maize plantlets inoculated with Enterobacter spp., as a model for alternative agriculture / Respuesta de plántulas de maíz inoculadas con Enterobacter spp. como un modelo de agricultura alternativa

A maize rhizosphere isolate was phenotypically and genotypically characterized and identifed as Enterobacter spp. bacterium. Germinated seeds were inoculated, the plantlets were sown in vermiculite and in soil and grown under laboratory and feld conditions, respectively. The adherence, colonization and plant growth promotion capability of Enterobacter sp. UAPS03001 was evaluated in "Rojo-Criollo" maize under laboratory conditions. Twenty days after inoculation, the treated plantlets showed larger biomass than non-inoculated ones. In feld grown plants, the kernel biomass was also greater in inoculated than in non-inoculated plants. The inoculation of maize sprouts with plant growth- promoting bacteria before their sowing in the feld would be an alternative practice for achieving successful yield in temporal agriculture.

En este trabajo se aisló una bacteria de la rizósfera de maíz, que fue caracterizada mediante métodos fenotípicos y genotípicos e identifcada como Enterobacter sp. UAPS03001. La bacteria fue inoculada en semillas de maíz "Rojo-Criollo" germinadas en forma axénica. Las semillas germinadas e inoculadas se plantaron en vermiculita y posteriormente las plántulas fueron cultivadas en vermiculita o en suelo, para evaluar el efecto promotor del crecimiento vegetal de dicha bacteria, bajo condiciones de laboratorio y de campo. Bajo condiciones de laboratorio, también se evaluó la capacidad de esta cepa para adherirse a las plantas de maíz y colonizarlas. Veinte días después de la inoculación, las plántulas inoculadas mostraron una biomasa mayor con referencia a las no inoculadas. En campo, la biomasa de la mazorca fue también mayor en las plantas inoculadas respecto de las plantas no inoculadas. La inoculación de germinados de maíz con una bacteria promotora del crecimiento vegetal y su posterior transferencia a campo podría ser una práctica alternativa para llevar a cabo una producción exitosa en agricultura de temporal.