Tomato Defense against Whiteflies under Drought Stress: Non-Additive Effects and Cultivar-Specific Responses.

Two of the main causes of losses in tomato production are the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), and drought, which is becoming a central problem in agriculture due to global climate change. The separate effects of whitefly infestation and drought have been amply studied in many crop systems. However, less is known about their combined effects. To evaluate whether drought stress (DS) affects plant defense against whiteflies, we assessed the joint effects of whitefly infestation and DS on plant vegetative and reproductive performance in four tomato cultivars, and assessed the effects of DS on plant resistance and tolerance (compensatory ability) to whiteflies in a greenhouse experiment. Generally, we found negative effects of DS and whiteflies on plant performance, but the combined effects of DS and herbivory were not worse than those of either stress alone. In fact, plant performance under the combined effect of both stresses was usually similar to that in the presence of whiteflies without DS. Plants growing under DS had greater trichome density. However, plant resistance-as measured by whitefly population growth-decreased under DS in two cultivars and was unaffected in the other two. Compensatory ability decreased under DS in all but one cultivar. These cultivar-specific responses suggest genetic variation in resistance and tolerance to whiteflies and could be associated with differences in drought tolerance among cultivars. Our findings underscore the difficulty in predicting the combined effects of DS and herbivory and point to the need for a better understanding of the mechanisms underlying plant responses to both stresses at the molecular, cellular, and organismal levels.

Lower Nitrogen Availability Enhances Resistance to Whiteflies in Tomato.

Soil nitrogen (N) supplementation via fertilizers may increase crop yields substantially. However, by increasing tissue N content, added N can make plants more attractive to herbivores, effectively reducing their resistance to herbivores (ability to avoid herbivore damage). In turn, greater pest infestation may cause more severe reductions in fruit production than a moderate N scarcity. In this study, we tested whether lower N supplementation results in greater resistance to whiteflies and lower fruit production in four tomato varieties. We assessed the effects of N availability on tolerance to herbivores (degree to which fitness is affected by damage) and tested for the long-hypothesized trade-off between resistance and tolerance. Plants grown at half of an agronomically recommended amount of N had greater resistance without a significant drop in fruit production. Tomato varieties differed in resistance and tolerance to whiteflies, and showed a clear trade-off between these modes of defense. Root:shoot ratios were greater at lower N, but had no clear relation to tolerance. We estimated that the economic benefit of decreasing N addition almost fully compensates for losses due to lower tomato production. Additionally, lower fertilization rates would contribute to reduce environmental costs of large-scale use of agrochemicals.

Identification of Virulences of the Rust Fungus Melampsora larici-populina Occurring in Chile.

Melampsora larici-populina Kleb. is a Eurasian species that causes leaf rust of many species of Populus from sections Tacamahaca and Aigeiros. This rust has been inadvertently introduced to many parts around the world affecting poplar species that grow naturally, which may be susceptible to this fungus. In Chile, early European settlers introduced poplars; rust, attributed to M. larici-populina, has been reported in these trees since 1918. However, a modern confirmation has been lacking, and pathogenic variation of the Chilean population of M. larici-populina has not been investigated. Using a morphological analysis of urediniospores and sequencing of internal transcribed spacer (ITS) regions, we confirmed the presence of M. larici-populina in Chile. ITS regions exhibited 100% homology with M. larici-populina. Scanning electron microscopy showed that spores were 26 to 47 µm in length, 13 to 16 µm in width, and echinulate except for apices, which are smooth, characteristics described for this species of rust. The variability of M. larici-populina is characterized by the presence of pathotypes, which allows the fungus to infect despite the resistance of certain poplar hybrids. We concluded that the identified spores belong to M. larici-populina, with virulences 1, 2, 3, 4, 5, and 6. These results describe variation in virulence of M. larici-populina, which suggests the presence of a sexual stage in Chile.

Trauma: un modelo de daño y su abordaje terapéutico / Trauma: a damage model and therapeutic approach

Se discute el concepto de trauma desde la perspectiva de Freud, Winincott y de los autores Kinston y Cohen. Se desarrolla el concepto de trauma de estos últimos. Ellos consideraron que la esencia del trauma es la falta de mediación de necesidades básicas del individuo por el objeto primario, en el sentido amplio del término, incluido el ambiente. Esto se puede producir durante la etapa del desarrollo como transcurso de la vida del individuo. Esta falta de mediación llevaría a una falla en el registro psíquico (representaciones mentales) produciendo lo que ellos llaman hoyo en la mente. De esta falta de estructuras se produciría un cuadro clínico característico. Para este cuadro ellos proponen un modelo terapéutico en fases, donde proponen que el analista y el analizando desarrollen una relación primaria en la cual se puede resignificar la falla y reparar el hoyo en la mente

Estudio exploratorio de un grupo de pacientes traumatizados extremos / Exploratory study in a group of patients with severe trauma

Estudio exploratorio-descriptivo que lleva a cabo una caracterización social, psicológica y médica,de un grupo de pacientes traumatizados extremos, víctimas de la represión política ejercida en Chile durante los años del gobierno militar. Las secuelas que sufren estas víctimas constituyen un grave problema que Chile debe encarar, ya que perduran en el tiempo, poseen un carácter crónico y severo, abarcan distintas áreas en la vida de estas personas (social, psicológica y médica) y afectan tanto a las víctimas directas como a sus generaciones futuras. Estas conclusiones hacen pensar en la urgencia de un plan de tratamiento integral para la población de víctimas de la represión política