Distinct colonization patterns and cDNA-AFLP transcriptome profiles in compatible and incompatible interactions between melon and different races of Fusarium oxysporum f. sp. melonis

Background: Fusarium oxysporum f. sp. melonis Snyd. & Hans. (FOM) causes Fusarium wilt, the most important infectious disease of melon (Cucumis melo L.). The four known races of this pathogen can be distinguished only by infection on appropriate cultivars. No molecular tools are available that can discriminate among the races, and the molecular basis of compatibility and disease progression are poorly understood. Resistance to races 1 and 2 is controlled by a single dominant gene, whereas only partial polygenic resistance to race 1,2 has been described. We carried out a large-scale cDNA-AFLP analysis to identify host genes potentially related to resistance and susceptibility as well as fungal genes associated with the infection process. At the same time, a systematic reisolation procedure on infected stems allowed us to monitor fungal colonization in compatible and incompatible host-pathogen combinations. Results: Melon plants (cv. Charentais Fom-2), which are susceptible to race 1,2 and resistant to race 1, were artificially infected with a race 1 strain of FOM or one of two race 1,2 w strains. Host colonization of stems was assessed at 1, 2, 4, 8, 14, 16, 18 and 21 days post inoculation (dpi), and the fungus was reisolated from infected plants. Markedly different colonization patterns were observed in compatible and incompatible host-pathogen combinations. Five time points from the symptomless early stage (2 dpi) to obvious wilting symptoms (21 dpi) were considered for cDNA-AFLP analysis. After successful sequencing of 627 transcript-derived fragments (TDFs) differentially expressed in infected plants, homology searching retrieved 305 melon transcripts, 195 FOM transcripts expressed in planta and 127 orphan TDFs. RNA samples from FOM colonies of the three strains grown in vitro were also included in the analysis to facilitate the detection of in planta-specific transcripts and to identify TDFs differentially expressed among races/strains. Conclusion: Our data suggest that resistance against FOM in melon involves only limited transcriptional changes, and that wilting symptoms could derive, at least partially, from an active plant response. We discuss the pathogen-derived transcripts expressed in planta during the infection process and potentially related to virulence functions, as well as transcripts that are differentially expressed between the two FOM races grown in vitro. These transcripts provide candidate sequences that can be further tested for their ability to distinguish between races. Sequence data from this article have been deposited in GenBank, Accession Numbers: HO867279-HO867981

Environmental Product Differentiation and Environmental Awareness

In this paper, we have considered a duopolistic model of environmental product differentiation with two types of consumers (green and brown) to analyze how environmental awareness affects the environment. "Green" consumers value the physical and environmental attributes of the good they purchase while "brown" consumers only value the physical attributes. We find that more environmental awareness may not be good news for the environment as the firm that produces the good without environmental attributes may increase its sales. The result depends on the degree of product differentiation and the cost to achieve it. Social welfare can also be inversely related to environmental awareness if the negative environmental effect dominates the positive market effect. © 2006 Springer Science+Business Media, Inc

A Hybrid Equilibrium in Segmented Markets: The 3-Firm Case

In this paper, we characterize two hybrid equilibria for the three-firm case in segmented markets in which consumers not only value the product itself but also the environment within which the consumption takes place. In equilibrium, the firm with the larger population of loyal consumers chooses the monopoly price while the remaining two firms play a mixed strategy. In the duopoly case, the unique equilibrium is in mixed strategies and no firm focuses only on its loyal consumers

Honesty in Environmental Regulation

This paper analyzes the determination of the optimal environmental regulatory policy under imperfect competition when the firms differ in their polluting technologies and degree of honesty. We show that more honesty does not necessarily imply lower social losses. The effect of honesty in social welfare depends not only on the degree of honesty measured by the proportion of honest firms and their particular cost features but also on the industry structure

El medio en que vivimos. Segundo ciclo, módulo 2

Existe otra edición revisada del año 1994 con ISBN 84-369-2094-5Libro de texto que corresponde al segundo módulo del segundo ciclo del programa de educación de adultos propuesto por el Centro Nacional de Educación Básica a Distancia (CENEBAD). Consta de cuatro unidades didácticas sobre el aire, el suelo y el paisaje, con ejercicios y actividades, tratadas de forma interdisciplinar, abarcando contenidos de las áreas de lengua, matemáticas, ciencias naturales y ciencias sociales. El alumno debe leer una obra literaria de entre varias recomendadas.MadridBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín 5 -3 Planta; 28014 Madrid; Tel. +34917748000; [email protected]

Medio y sociedad. Segundo ciclo, módulo 3

Libro de texto correspondiente al tercer módulo del segundo ciclo de educación a distancia de adultos propuesta por el Centro Nacional de Educación Básica a Distancia (CENEBAD). Consta de cuatro unidades didácticas sobre los beneficios que nos proporciona el medio físico en las que se trabajan de un modo interdisciplinar contenidos de las áreas de lengua, matemáticas, ciencias naturales y ciencias sociales. Se recomiendan varios libros de lectura como complemento, de los cuales el alumno debe leer uno y elaborar una ficha técnica.MadridBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín 5 -3 Planta; 28014 Madrid; Tel. +34917748000; [email protected]