History on the biological nitrogen fixation research in graminaceous plants: special emphasis on the Brazilian experience

This review covers the history on Biological Nitrogen Fixation (BNF) in Graminaceous plants grown in Brazil, and describes research progress made over the last 40 years, most of whichwas coordinated by Johanna Döbereiner. One notable accomplishment during this period was the discovery of several nitrogen-fixing bacteria such as the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali), associative (Azospirillum lipoferum, A. brasilense, A. amazonense) and the endophytic (Herbaspirillum seropedicae, H. rubrisubalbicans, Gluconacetobacter diazotrophicus, Burkholderia brasilensis and B. tropica). The role of these diazotrophs in association with grasses, mainly with cereal plants, has been studied and a lot of progress has been achieved in the ecological, physiological, biochemical, and genetic aspects. The mechanisms of colonization and infection of the plant tissues are better understood, and the BNF contribution to the soil/plant system has been determined. Inoculation studies with diazotrophs showed that endophytic bacteria have a much higher BNF contribution potential than associative diazotrophs. In addition, it was found that the plant genotype influences the plant/bacteria association. Recent data suggest that more studies should be conducted on the endophytic association to strengthen the BNF potential. The ongoing genome sequencing programs: RIOGENE (Gluconacetobacter diazotrophicus) and GENOPAR (Herbaspirillum seropedicae) reflect the commitment to the BNF study in Brazil and should allow the country to continue in the forefront of research related to the BNF process in Graminaceous plants

Microorganisms that improve plant growth and soil quality

[ES] El presente artículo surge de la revisión de la teoría y temas prácticos desarrollados durante el curso”Caracterización y contribución de las plantas que promueven el crecimiento de microorganismos en la sostenibilidad de la agricultura”, llevado a cabo en el Laboratorio de Microbiología de Suelos de la Corporación Colombiana de Investigación Agropecuaria (Corpoica), ubicado en Mosquera (Cundinamarca), Colombia, en julio de 2010. Esta actividad fue desarrollada en el marco de la Red Dimiagri que incluye a investigadores de Argentina, Brasil, Colombia, España, Guatemala, México y Uruguay, reunidos en una acción de coordinación financiada por el Programa Iberoamericano de Ciencia y Tecnología para el Desarrollo (Cyted). Los aspectos inherentes al crecimiento y la sanidad vegetal, el sistema radical, el suelo circundante (rizósfera), los microorganismos asociados en ese sistema y su contribución al manejo sustentable del complejo suelo-planta fueron analizados en este trabajo. También se abordan temas como la biodiversidad microbiana y su efecto en la calidad del suelo; el ciclado de nutrientes del suelo por acción microbiológica; la importancia de los microorganismos en la promoción del crecimiento vegetal y su utilización biotecnológica como alternativa para favorecer la sustentabilidad y calidad de los suelos. Además se pretende interiorizar en los conceptos relacionados con el consorcio suelo-planta-microorganismo y el objetivo de mitigar el impacto ambiental negativo causado por el uso excesivo de insumos químicos en los cultivos agrícolas, mediante la utilización de microorganismos promotores del crecimiento vegetal, que incluyen tanto a bacterias como a hongos benéficos asociados con las raíces de las plantas.[EN] The present article of revision arise from theory and practical subjects developed during the course “Characterization and contribution of plant growth-promoting microorganisms in the agricultural sustainability” carried out in the Laboratory of Soil Microbiology of the Colombian Corporation of Agricultural Research (Corpoica) located in Mosquera (Cundinamarca), Colombia, in July 2010. This activity is in the framework of the Dimiagri network that includes researchers from Argentina, Brazil, Colombia, Spain, Guatemala, Mexico and Uruguay, gathered in a Coordination Action funded by the Iberoamerican Program of Science and Technology for the Development (Cyted). Aspects inherent to the growth and plant health, root system, the surrounding soil (rhizosphere), microorganisms that system partners and their contribution to sustainable management of soil-plant were analyzed in this work. Topics related to the microbial biodiversity and its effect on soil quality; nutrient cycling in the soil by microbiological activity; the importance of microorganisms in plant growthpromotion and their biotechnological application as an alternative to favor sustainability and soil quality were presented. The aim of this review is to show important concepts related to the soil-plant-microorganism system, which will allow to achieve the general objective: to mitigate the negative environmental impact due to the excessive use of chemical products on agricultural crops by using plant growth-promoting microorganisms, including bacteria and beneficial fungi associated to plant roots.Los autores agradecen el financiamiento del Cyted y CNPq (Proc. Nº 490013/2010-4) mediante la Red Dimiagri/Acción 409AC0379.Peer reviewe