Inclusión del género Paspalum en mezclas forrajeras efectos sobre la disponibilidad de forraje, la resistencia a la invasión, y la estabilidad

Una de las principales limitantes de la producción ganadera en Uruguay es la corta vida útil de sus pasturas sembradas. El origen templado de las especies sembradas determina una disminución de su producción en verano y consumo de recursos del ambiente, favoreciendo la colonización de especies invasoras. En consecuencia, las pasturas perennes deben ser re-implantadas cada 3-4 años. Una de las alternativas para solucionar este problema es la inclusión de gramíneas perennes estivales. El género Paspalum presenta buena adaptación a las condiciones ambientales regionales y buen potencial forrajero. Sin embargo la investigación nacional previa ha sido de pequeña escala y por cortos períodos de tiempo, lo cual ha limitado la inclusión de este género en mezclas comerciales. El objetivo de esta investigación fue evaluar la inclusión de dos gramíneas perennes estivales, P. dilatatum y P. notatum, sobre la disponibilidad de forraje, la resistencia a la invasión, y la estabilidad de una mezcla convencional de leguminosas y gramíneas invernales en parcelas de 1 hectárea bajo pastoreo de ganado lechero, durante 4 años. Las mezclas no mostraron diferencias en su disponibilidad de forraje, ni biomasa de especies invasoras. Las mezclas con Paspalum presentaron mayor cobertura en otoño y las mezclas con P. notatum presentaron menor cobertura en invierno. Las mezclas no mostraron diferencias para los indicadores de estabilidad temporal utilizados. El componente invernal de la mezcla (Festuca) disminuyó en mezclas con P. notatum, lo cual no ocurrió en mezclas con P. dilatatum. El denso tapiz de generado por P. notatum puede aumentar la cobertura en otoño pero disminuir la disponibilidad en invierno debido a una reducción en la abundancia de Festuca. Para maximizar los beneficios de la inclusión de una gramínea perenne estival es recomendable que las especies presenten una habilidad competitiva moderada, como P. dilatatum, de forma de evitar impactos negativos sobre el componente templado

Invasive Listeriosis at Intensive Care Units: Review of a series of cases

Darwin Tejera: . Centro de Tratamiento Intensivo, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Uruguay.-- Fernanda Alonso: Asociación Española Primera de Socorros Mutuos, Uruguay.-- Mario Silva: Asociación Española Primera de Socorros Mutuos, Uruguay.-- Jorge Modernel: Asociación Española Primera de Socorros Mutuos, Uruguay.-- Gino Limongi: Asociación Española Primera de Socorros Mutuos, Uruguay -- Mauricio Bertullo: Asociación Española Primera de Socorros Mutuos, Uruguay.-- Fernando Villalba: Asociación Española Primera de Socorros Mutuos, Uruguay.-- Mario Cancela: Asociación Española Primera de Socorros Mutuos, Uruguay. Contacto: Darwin Tejera. E-mail: [email protected] describen las características clínicas de una serie de casos de infecciones por Listeria monocytogenes en una Unidad de Terapia Intensiva polivalente, en Montevideo, Uruguay. Se trata de un estudio retrospectivo, de una serie de casos de Listeriosis Invasiva ingresadas entre julio 2010 y julio 2013 a dicha Unidad. Se incluyeron todos los casos confirmados. Se realizó un análisis descriptivo de las variables de interés. Se encontraron 11 casos de Listeriosis Invasiva. En relación al sexo fueron 6 hombres y 5 mujeres, la media de edad fue de 62 años con un desvío estándar ± 12 años y un rango de 22 a 83 años. La media de APACHE II fue de 23 con un desvío estándar ± 9. La mediana del tiempo de estadía en UTI fue de 8 días con un rango intercuartílico de 6. El requerimiento de asistencia respiratoria mecánica fue de 81,8%. Los factores predisponentes detectados fueron diabetes mellitus, enfermedad neoplásica, alcoholismo, inmunosupresión y/o corticoides y edad avanzada. Las presentaciones clínicas fueron: cinco meningitis, tres sepsis, una paciente obstétrica, una bacteremia por infección por catéter y una peritonitis espontánea. En todos los casos se detectaron factores predisponentes. El antibiótico más utilizado fue la ampicilina. La mortalidad global fue de 63% con una mortalidad estandarizada de 1.36. Se concluyó que la Listeriosis Invasiva se presentó en pacientes con uno o más factores predisponentes. El cuadro clínico más frecuente fue secundario a la infección del sistema nervioso central. Se asoció con una elevada mortalidad .Clinical characteristics of patients admitted to a general Intensive Care Unit in Montevideo (Uruguay) due to Listeria monocytogenes infections are described. It is a retrospective study of cases admitted at the mentioned intensive care unit, during a period of three years from July 2010 to July 2013. All confirmed cases of invasive listeriosis were included. A descriptive analysis of the variables of interest was performed. Eleven cases of invasive listeriosis were identified, 6 were men, 5 women. Mean age was 62 years with a standard deviation (SD) ± 12 years ranged from 22 to 83 years. Mean APACHE II was 23 with SD ± 9. The median length of stay at ICU was 8 days with an interquartile range of 6. Mechanical ventilation was required in 81.8% cases. Diabetes mellitus, neoplasic disease, alcoholism, immunosuppression, prior corticosteroids therapy and age were predisposing factors detected in these patients. The presenting forms were five as meningoencephalitis, three primary bacteremia, one with a central venous catheter infection, one in an obstetric patient and one as a spontaneous peritonitis in a cirrhotic patient. At least one of the predisposing factors mentioned previously were identified in all of the cases. The most commonly used antibiotic was ampicillin. Overall mortality was 63%. We concluded that Invasive Listeriosis is an opportunistic infectious disease that usually appears in patients with one or more associated risk factors. The most common presentation is as a central nervous system infection and it is associated with high mortality rates

Seasonal decline in leaf photosynthesis in perennial switchgrass explained by sink limitations and water deficit

Leaf photosynthesis of perennial grasses usually decreases markedly from early to late summer, even when the canopy remains green and environmental conditions are favorable for photosynthesis. Understanding the physiological basis of this photosynthetic decline reveals the potential for yield improvement. We tested the association of seasonal photosynthetic decline in switchgrass (Panicum virgatum L.) with water availability by comparing plants experiencing ambient rainfall with plants in a rainfall exclusion experiment in Michigan, USA. For switchgrass exposed to ambient rainfall, daily net CO2 assimilation ( Anet') declined from 0.9 mol CO2 m-2 day-1 in early summer to 0.43 mol CO2 m-2 day-1 in late summer (53% reduction; P<0.0001). Under rainfall exclusion shelters, soil water content was 73% lower and Anet' was 12% and 26% lower in July and September, respectively, compared to those of the rainfed plants. Despite these differences, the seasonal photosynthetic decline was similar in the season-long rainfall exclusion compared to the rainfed plants; Anet' in switchgrass under the shelters declined from 0.85 mol CO2 m-2 day-1 in early summer to 0.39 mol CO2 m-2 day-1 (54% reduction; P<0.0001) in late summer. These results suggest that while water deficit limited Anet' late in the season, abundant late-season rainfalls were not enough to restore Anet' in the rainfed plants to early-summer values suggesting water deficit was not the sole driver of the decline. Alongside change in photosynthesis, starch in the rhizomes increased 4-fold (P<0.0001) and stabilized when leaf photosynthesis reached constant low values. Additionally, water limitation under shelters had no negative effects on the timing of rhizome starch accumulation, and rhizome starch content increased ~ 6-fold. These results showed that rhizomes also affect leaf photosynthesis during the growing season. Towards the end of the growing season, when vegetative growth is completed and rhizome reserves are filled, diminishing rhizome sink activity likely explained the observed photosynthetic declines in plants under both ambient and reduced water availability

The impact of stand age and fertilization on the soil microbiome of Miscanthus × giganteus

Yield of the perennial grass Miscanthus × giganteus has shown an inconsistent and unpredictable response to nitrogen (N) fertilizer, yet fertilization underpins the crop’s environmental and economic sustainability. The interactions among soil microbial communities, N availability, and Miscanthus × giganteus and management may explain changes in plant productivity. In this study, soil samples from different stand ages of Miscanthus × giganteus in a replicated chronosequence field trial were used to investigate the effects of stand age and N fertilizer rates on microbial community structure. We hypothesized that there is a definable Miscanthus × giganteus soil microbiome and that this community varies significantly with stand age and fertilization. Our results showed that the main phyla in soil microbial communities, regardless of plant age, are similar but microbial community structures are significantly different. The variation in observed microbial communities generally decreases with older stand ages. The amount of N fertilizer applied also affected the microbial community structure associated with different aged Miscanthus × giganteus. Specifically, the relative abundance of Proteobacteria (Alphaproteobacteria and Gammaproteobacteria) and Acidobacteria (subgroup Gp1) increased shortly after fertilization and was more associated with younger Miscanthus × giganteus. Furthermore, our results show a significant relationship between bacterial α diversity and fertilization rates and that this response is also affected by stand age. Overall, our results emphasize linkages between microbial community structure, plant age, and fertilization in Miscanthus × giganteus

Age and nitrogen effects on Miscanthus × giganteus growth and development

Perennial grasses have received increased attention in the last few decades for their potential to mitigate global energy and climate change challenges, however, basic aspects of their physiology and aging remain poorly understood. In addition, research on perennial grasses is underpinned by conventional field experiments whose designs still neglect important aspects of plant-age dynamics in these long-lived species. We used a REpeated PLAnting Year (REPLAY), also known as staggered-start, experimental design to study Miscanthus × giganteus nitrogen (N) needs and age-related changes in physiology and phenology. We conducted a REPLAY experiment with three planting years and five N rates during the M. × giganteus yield-building phase at three sites across Iowa, USA. Miscanthus × giganteus reached peak yields (~27.1 Mg dry matter (DM) ha-1) after the third year, and N fertilization effects changed with establishment conditions, but not with plant age (Chapter 2). To make stand comparisons on a common time scale rather than thermal time or calendar days, I developed a unified morphological development scale (Chapter 3). Older M. × giganteus stands usually started development earlier and developed further in a given growing season. Nitrogen fertilization did not change phenology in one-year-old stands and mainly affected emergence and senescence in older (two- and three-year-old) stands (Chapter 4). Older stands also had lower photosynthetic rates and leaf N contents, suggesting potential N dilution in older, larger plants (Chapter 5). However, N fertilization increased leaf N in older stands up to juveniles’ levels but did not compensate for the age-related photosynthetic decline, suggesting that N was not a limiting factor for carbon assimilation. These results could be a consequence of life strategy shifts from a competitor strategy that prioritizes resource acquisition in juvenile stands to a stress-tolerant strategy that prioritizes nutrient remobilization and winter survival in older stands. Further research is needed to study other potential hypotheses.</p

Age and nitrogen effects on Miscanthus × giganteus growth and development

Perennial grasses have received increased attention in the last few decades for their potential to mitigate global energy and climate change challenges, however, basic aspects of their physiology and aging remain poorly understood. In addition, research on perennial grasses is underpinned by conventional field experiments whose designs still neglect important aspects of plant-age dynamics in these long-lived species. We used a REpeated PLAnting Year (REPLAY), also known as staggered-start, experimental design to study Miscanthus × giganteus nitrogen (N) needs and age-related changes in physiology and phenology. We conducted a REPLAY experiment with three planting years and five N rates during the M. × giganteus yield-building phase at three sites across Iowa, USA. Miscanthus × giganteus reached peak yields (~27.1 Mg dry matter (DM) ha-1) after the third year, and N fertilization effects changed with establishment conditions, but not with plant age (Chapter 2). To make stand comparisons on a common time scale rather than thermal time or calendar days, I developed a unified morphological development scale (Chapter 3). Older M. × giganteus stands usually started development earlier and developed further in a given growing season. Nitrogen fertilization did not change phenology in one-year-old stands and mainly affected emergence and senescence in older (two- and three-year-old) stands (Chapter 4). Older stands also had lower photosynthetic rates and leaf N contents, suggesting potential N dilution in older, larger plants (Chapter 5). However, N fertilization increased leaf N in older stands up to juveniles’ levels but did not compensate for the age-related photosynthetic decline, suggesting that N was not a limiting factor for carbon assimilation. These results could be a consequence of life strategy shifts from a competitor strategy that prioritizes resource acquisition in juvenile stands to a stress-tolerant strategy that prioritizes nutrient remobilization and winter survival in older stands. Further research is needed to study other potential hypotheses

Description and Codification of Miscanthus × giganteus Growth Stages for Phenological Assessment

Triploid Miscanthus × giganteus (Greef et Deu. ex Hodkinson et Renvoize) is a sterile, perennial grass used for biomass production in temperate environments. While M. × giganteus has been intensively researched, a scale standardizing description of M. × giganteus morphological stages has not been developed. Here we provide such a scale by adapting the widely-used Biologische Bundesanstalt, Bundessortenamt, CHemische Industrie (BBCH) scale and its corresponding numerical code to describe stages of morphological development in M. × giganteus using observations of the “Freedom” and “Illinois” clone in Iowa, USA. Descriptive keys with images are also presented. Because M. × giganteus plants overlap in the field, the scale was first applied to individual stems and then scaled up to assess plants or communities. Of the 10 principal growth stages in the BBCH system, eight were observed in M. × giganteus. Each principal stage was subdivided into secondary stages to enable a detailed description of developmental progression. While M. × giganteus does not have seed development stages, descriptions of those stages are provided to extend the scale to other Miscanthus genotypes. We present methods to use morphological development data to assess phenology by calculating the onset, duration, and abundance of each developmental stage. This scale has potential to harmonize previously described studyspecific scales and standardize results across studies. Use of the precise staging presented here should more tightly constrain estimates of developmental parameters in crop models and increase the efficacy of timing-sensitive crop management practices like pest control and harvest.This article is published as Tejera, Mauricio Diego, and Emily Anne Heaton. "Description and codification of Miscanthus× giganteus growth stages for phenological assessment." Frontiers in Plant Science 8 (2017): 1726. doi: 10.3389/fpls.2017.01726. Posted in permission.</p

Description and Codification of Miscanthus × giganteus Growth Stages for Phenological Assessment

Triploid Miscanthus × giganteus (Greef et Deu. ex Hodkinson et Renvoize) is a sterile, perennial grass used for biomass production in temperate environments. While M. × giganteus has been intensively researched, a scale standardizing description of M. × giganteus morphological stages has not been developed. Here we provide such a scale by adapting the widely-used Biologische Bundesanstalt, Bundessortenamt, CHemische Industrie (BBCH) scale and its corresponding numerical code to describe stages of morphological development in M. × giganteus using observations of the “Freedom” and “Illinois” clone in Iowa, USA. Descriptive keys with images are also presented. Because M. × giganteus plants overlap in the field, the scale was first applied to individual stems and then scaled up to assess plants or communities. Of the 10 principal growth stages in the BBCH system, eight were observed in M. × giganteus. Each principal stage was subdivided into secondary stages to enable a detailed description of developmental progression. While M. × giganteus does not have seed development stages, descriptions of those stages are provided to extend the scale to other Miscanthus genotypes. We present methods to use morphological development data to assess phenology by calculating the onset, duration, and abundance of each developmental stage. This scale has potential to harmonize previously described study-specific scales and standardize results across studies. Use of the precise staging presented here should more tightly constrain estimates of developmental parameters in crop models and increase the efficacy of timing-sensitive crop management practices like pest control and harvest