Qué papel juega el hongo Phytophthora cinnamomi en el desarrollo de la regeneración natural y repoblaciones de encina y alcornoque

Se presentan los resultados resumidos de tres trabajos realizados para conocer el papel que juega el hongo Phytophthora cinnamomi en el desarrollo de plántulas de encina (Quercus ilex) y alcornoque (Quercus suber). Se realizaron dos prospecciones para detectar la presencia de P.cinnamomi en focos de seca en dehesas de encina y alcornoque de Extremadura en 1991-1992 y 1999-2000. El porcentaje de focos en los que se detectó la presencia de P. cinnamomi ha permanecido relativamente estable entre las dos prospecciones. También se determinó la tasa de crecimiento relativo para nueve aislados de P. cinnamomi a diferentes temperaturas, observando una elevada variabilidad tanto en la temperatura óptima de crecimiento como en el valor de la propia tasa diaria de crecimiento máxima. También se estudió la emergencia y supervivencia de plántulas de encina y alcornoque procedentes de dos dehesas ecológicamente diferentes, cultivadas en condiciones controladas en suelos de estas dehesas infectados naturalmente con P. cinnamomi y en estos mismos suelos previamente desinfectados en autoclave. Un factor limitante en los procesos de regeneración natural y en las repoblaciones por siembra directa de encinas y alcornoque puede ser su alta susceptibilidad a las infecciones por P. cinnamomi.Por último, se estudió durante dos años consecutivos, la supervivencia de las plantas de encina de una repoblación sobre un suelo naturalmente infectado con P. cinnamomi en la provincia de Badajoz (SO de España). Los resultados obtenidos se discuten teniendo en cuenta el déficit hídrico, los daños por P. cinnamomi, la competencia con otras especies y las posibles medidas sanitarias que amortigüen los daños en las repoblaciones con encinas._______________________________Three different studies were performed with the aim to determine the role of Phytophthora cinnamomi in the early development of seedlings of holm oak (Quercus ilex) and cork oak (Quercus suber). Two surveys, for the presence of Phytophthora cinnamomi in declining holm oak and cork oak stands in Extremadura (SW Spain) were performed in 1991-1992 and 1999-2000. The percentage of decline foci where P. cinnamomi is envolved has remained relatively stable in the lapse of time between the two surveys. Growth rates were determined for 9 P. cinnamomi isolates. Considerable variation in optimum growth temperatures and in daily growth rates occurred among isolates. The emergence and survival of pregerminated holm oak and cork oak acorns from two ecologically different dehesas (Mediterranean open woodlands) were studied in two soils from these stands naturally infected with P. cinnamomi, and in the same soils previously sterilized in the autoclave. The demonstrated high susceptibility of holm and cork oak young seedlings to P. cinnamomi could be a limiting factor in mediterranean opend woodlands (dehesas) not only in natural regenerationprocesses but also when reforestation by direct sowing is implemented. Finally, the viability of 1 year old holm oak seedlings in a soil naturally infected with P. cinnamomi was studied during two consecutive years in a plot located in SW Spain. Results obtained are discussed in the framework of seasonal water deficit, P. cinnamomi damage, weed competition and sanitation thechniques to be used in declined holm oak stands in Spain

Climate change in Central and South America: Recent trends, future projections, and impacts on regional agriculture

This report investigates the climate of two target regions of the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS): Central and South America (CA and SA, respectively). The report assesses the implications of climate change for agriculture, with a particular focus on those aspects of climate change that will have greatest impact on the crops currently grown in each region. The study investigated the ability of General Circulation Models (GCMs) and downscaled climate change scenarios to reproduce already observed climates, to establish the reliability of future climate projections, as well as projections of how associated crops might grow under future conditions

Bioensayos de insecticidas con el trips del trigo, Haplothrips tritici (Kurdjumov)

[ESP] Para estudiar las materias activas más adecuadas para el control del trips del trigo, Haplothrips tritici (Kurdjumov), se realizaron una serie de bioensayos sobre cinco poblaciones naturales, recogidas de diferentes localidades de Castilla-La Mancha y Badajoz. Se ensayaron dos insecticidas clorados (endosulfan y lindano), dos carbamatos (carbaril y metomilo), ocho fosforados (acefato, clorpirifos, diazinón, dimetoato, fenitrotión, fosalone, malatión y triclorfón) y cuatro piretroides (cipermetrín, deltametrín, fenvalerato y lambda cihalotrín). Todos los insecticidas ensayados se mostraron activos sobre las larvas II. Sin embargo, comparando con las dosis recomendadas en campo, los carbamatos y fosforados mostraron las eficacias más altas, excepto fosalone que dio una eficacia media. Los piretroides mostraron una eficacia media, excepto para deltametrín que fue baja y fenvalerato que fue muy baja. En los clorados, endosulfan mostró una eficacia baja y lindano muy baja. Aunque se encontraron diferencias significativas en la concentración letal 50 entre las poblaciones, su magnitud no fue importante. [ENG] In an insecticide bioassays carried out on natural populations of five localities of Castilla-La Mancha and Badajoz, all the insecticides tested showed activity on larvae II. However, comparing with the recommended field dose, the carbamates and phosphates showed the highest efficiencies, except phosalone that gave an average efficiency. The pyretroids showed an average efficiency, except deltametrin which was low and emphasized fenvalerate which was very low. In the chlorinates, endosulfan showed a low efficiency and lindane was very low. Thought significant differences were found in the lethal concentration 50 between populations, they were not important

Bacterial Communities And Species-specific Associations With The Mucus Of Brazilian Coral Species.

We investigated the existence of species-specific associations between Brazilian coral species and bacteria. Pyrosequencing of the V3 region of the 16S rDNA was used to analyze the taxonomic composition of bacterial communities associated with the mucus of four coral species (Madracis decactis, Mussismilia hispida, Palythoa caribaeorum, and Tubastraea coccinea) in two seasons (winter and summer), which were compared with the surrounding water and sediment. The microbial communities found in samples of mucus, water, and sediment differed according to the composition and relative frequency of OTUs. The coral mucus community seemed to be more stable and resistant to seasonal variations, compared to the water and sediment communities. There was no influence of geographic location on the composition of the communities. The sediment community was extremely diverse and might act as a "seed bank" for the entire environment. Species-specific OTUs were found in P. caribaeorum, T. coccinea, and M. hispida.3162

Macroclumping as solution of the discrepancy between Hα and P v mass loss diagnostics for O-type stars

Context. Recent studies of O-type stars have demonstrated that discrepant mass-loss rates are obtained when different diagnostic methods are employed. Fitting the unsaturated UV resonance lines (e.g., P v) gives drastically lower values than obtained from the Hα emission. Wind inhomogeneity (so-called "clumping") may be the main cause of this discrepancy. Aims. In a previous paper, we presented 3D Monte-Carlo calculations for the formation of scattering lines in a clumped stellar wind. In the present paper we select five O-type supergiants (from O4 to O7) and test whether the reported discrepancies can be resolved this way. Methods. In the first step, the analyses started with simulating the observed spectra with Potsdam Wolf-Rayet (PoWR) non-LTE model atmospheres. The mass-loss rates are adjusted to fit to the observed Hα emission lines best. For the unsaturated UV resonance lines (i.e., P v) we then applied our 3D Monte-Carlo code, which can account for wind clumps of any optical depths ("macroclumping"), a non-void interclump medium, and a velocity dispersion inside the clumps. The ionization stratifications and underlying photospheric spectra were adopted from the PoWR models. The properties of the wind clumps were constrained by fitting the observed resonance line profiles. Results. Our results show that with the mass-loss rates that fit Hα (and other Balmer and He ii lines), the UV resonance lines (especially the unsaturated doublet of P v) can also be reproduced with no problem when macroclumping is taken into account. There is no need to artificially reduce the mass-loss rates or to assume a subsolar phosphorus abundance or an extremely high clumping factor, unlike what was claimed by other authors. These consistent mass-loss rates are lower by a factor of 1.3 to 2.6, compared to the mass-loss rate recipe from Vink et al. Conclusions. Macroclumping resolves the previously reported discrepancy between Hα and P v mass-loss diagnostics.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Macroclumping as solution of the discrepancy between Hα and P v mass loss diagnostics for O-type stars

Context. Recent studies of O-type stars have demonstrated that discrepant mass-loss rates are obtained when different diagnostic methods are employed. Fitting the unsaturated UV resonance lines (e.g., P v) gives drastically lower values than obtained from the Hα emission. Wind inhomogeneity (so-called "clumping") may be the main cause of this discrepancy. Aims. In a previous paper, we presented 3D Monte-Carlo calculations for the formation of scattering lines in a clumped stellar wind. In the present paper we select five O-type supergiants (from O4 to O7) and test whether the reported discrepancies can be resolved this way. Methods. In the first step, the analyses started with simulating the observed spectra with Potsdam Wolf-Rayet (PoWR) non-LTE model atmospheres. The mass-loss rates are adjusted to fit to the observed Hα emission lines best. For the unsaturated UV resonance lines (i.e., P v) we then applied our 3D Monte-Carlo code, which can account for wind clumps of any optical depths ("macroclumping"), a non-void interclump medium, and a velocity dispersion inside the clumps. The ionization stratifications and underlying photospheric spectra were adopted from the PoWR models. The properties of the wind clumps were constrained by fitting the observed resonance line profiles. Results. Our results show that with the mass-loss rates that fit Hα (and other Balmer and He ii lines), the UV resonance lines (especially the unsaturated doublet of P v) can also be reproduced with no problem when macroclumping is taken into account. There is no need to artificially reduce the mass-loss rates or to assume a subsolar phosphorus abundance or an extremely high clumping factor, unlike what was claimed by other authors. These consistent mass-loss rates are lower by a factor of 1.3 to 2.6, compared to the mass-loss rate recipe from Vink et al. Conclusions. Macroclumping resolves the previously reported discrepancy between Hα and P v mass-loss diagnostics.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Collective effects of stellar winds and unidentified gamma-ray sources

We study collective wind configurations produced by a number of massive stars, and obtain densities and expansion velocities of the stellar wind gas that is to be target, in this model, of hadronic interactions. We study the expected $\gamma$-ray emission from these regions, considering in an approximate way the effect of cosmic ray modulation. We compute secondary particle production (electrons from knock-on interactions and electrons and positrons from charged pion decay), and solve the loss equation with ionization, synchrotron, bremsstrahlung, inverse Compton, and expansion losses. We provide examples where configurations can produce sources for GLAST satellite, and the MAGIC, HESS, or VERITAS telescopes in non-uniform ways, i.e., with or without the corresponding counterparts. We show that in all cases we studied no EGRET source is expected

Incidencia cualitativa y cuantitativa de Haplothrips tritici Kurd. (Thysanoptera: Phlaeothripidae) en la producción de trigo

[ESP] Durante las campañas 1993/94 y 1994/95 se ha realizado un estudio en Santa Olalla (Toledo) sobre los daños que realiza Haplothrips tritici Kurd, en el trigo. Las infestaciones [ENG] Investigations were carried out in 1993-95 on injuriousness of Haplothrips tritici on wheat in Toledo (central Spain). Natural infestations reached very high levels, over 200 larvae per ear. Yield was decreased over 50%, compared with plots with low population levels, reducing grains per ear and weight grain. In addition wheat thrips had a negative impact on grain quality (hectolitre weight) and baking quality, reducing the grain worth. naturales registradas alcanzaron niveles muy altos, superiores a 200 larvas por espiga. La producción disminuyó en más de un 50% respecto a las parcelas con densidades bajas, consecuencia de la reducción del número de granos por espiga y el peso de mil granos. Tanto la calidad física del grano (peso específico) como la calidad harinera (porcentaje de degradación de la fuerza panadera) se vieron afectados, reduciendo el valor comercial del grano.Queremos agradecer a Carlos Lacasta su ayuda y aportaciones en el desarrollo de los ensayos, así como al resto del personal de lafinca "La Higueruela". También a Manuela Gómez, por el laborioso trabajo realizado en el laboratorio. Nuestro agradecimiento al Servicio de Investigación Agraria de la Consejería de Agricultura y Medio Ambiente de la J. CC. de Castilla-La Mancha por el apoyo y financiación de este proyecto

Efecto del laboreo en la supervivencia de las larvas invernantes de Haplothrips tritici Kurd. (Thysanoptera: Phlaeothripidae)

[ESP] Durante la campaña 1994/95 se realizó un estudio en Santa Olalla (Toledo) sobre la influencia de las labores en la mortalidad de las larvas invernantes de Haplothrips tritici, así como de la pauta de emergencia de los adultos en primavera. Esta mostró una buena sincronización con la fenología del trigo, produciéndose desde el estado de hoja bandera hasta la formación del grano, con un pico en torno a la emergencia de la espiga. El ratio sexual varió con el ciclo, apareciendo primero sólo hembras, aumentando progresivamente la proporción de machos. Aunque se observó una tendencia en la disminución de las poblaciones de adultos que emergieron en primavera, en el sentido: barbecho químico > no-laboreo > vertedera > cultivador > quema+cultivador, sólo la labor de quema del rastrojo más cultivador mostró diferencias significativas. [ENG]Investigations were carried out in 1994-95 on effect of cultivations on mortality of overwintering larvae of Haplothrips tritici in Toledo (central Spain). Adult emerging path showed a perfect synchronization with wheat growth, occurring since last leaf stage until end of flowering, with a peak around boot stage. Sex ratio varied along the cycle, with only females at the beginning, increasing male number forward. The number of Haplothrips tritici emerging in spring decreased with cultivations: fallow > no-tillage > ploughing > cultivator > burning stuble+cultivator, although only the last one showed significant differences.Queremos agradecer a Carlos Lacasta su ayuda y aportaciones en el desarrollo del ensayo, así como al resto del personal de la finca "La Higueruela". También a Manuela Gómez, por el laborioso trabajo realizado en el laboratorio. Nuestro agradecimiento al Servicio de Investigación Agraria de la Consejería de Agricultura y Medio Ambiente de la J. CC. de Castilla-La Mancha por el apoyo y la financiación de este proyecto