University of Hohenheim

About: University of Hohenheim is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Population & Soil water. The organization has 8585 authors who have published 16406 publications receiving 567377 citations.

Assessing non-specificity of resistance in wheat to head blight caused by inoculation with European strains of Fusarium culmorum, F. graminearum and F. nivale using a multiplicative model for interaction.

Abstract: To determine whether resistance to Fusarium head blight in winter wheat is horizontal and non-species specific, 25 genotypes from five European countries were tested at six locations across Europe in the years 1990, 1991, and 1992. The five genotypes from each country had to cover the range from resistant to susceptible. The locations involved were Wageningen, Vienna, Rennes, Hohenheim, Oberer Lindenhof, and Szeged. In total, 17 local strains of Fusarium culmorum, F. graminearum, and F. nivale were used for experimental inoculation. One strain, F. culmorum IPO 39-01, was used at all locations. Best linear unbiased predictions (BLUPs) for the head blight ratings of the genotypes were formed within each particular location for each combination of year and strain. The BLUPs over all locations were collected in a genotype-by environment table in which the genotypic dimension consisted of the 25 genotypes, while the environmental dimension was made up of 59 year-by-strain-by-location combinations. A multiplicative model was fitted to the genotype by-environment interaction in this table. The inverses of the variances of the genotype-by-environment BLUPs were used as weights. Interactions between genotypes and environments were written as sums of products between genotypic scores and environmental scores. After correction for year-by-location influence very little variation in environmental scores could be ascribed to differences between strains. This provided the basis for the conclusion that the resistance to Fusarium head blight in winter wheat was of the horizontal and non-species specific type. There was no indication for any geographical pattern in virulence genes. Any reasonable aggressive strain, a F. culmorum strain for the cool climates and a F. graminearum strain for the warmer humid areas, should be satisfactory for screening purposes.

Migration, Self-Selection and Income Inequality: An International Analysis

Abstract: In the context of an emerging focus on highly skilled migration throughout the OECD area, the question under which circumstances migrants can be expected to be relatively skilled is of particular importance. Borjas has analysed the relation between the income distribution and the skills of migrants. His self-selection model predicts that immigrants from countries with a higher income inequality tend to be negatively selected (i.e., less skilled than the average worker in both host and source countries). According to other models based on the human capital theory of migration, however, migrants can be expected to be relatively skilled. Empirical tests of Borjas' much-disputed negative self-selection hypothesis generally rely on immigration data, particularly to the US, and may therefore be biased due to host-country specifics such as network migration and the impact of migration policy. This paper analyses the relationship between country-specific emigration propensities and each country's score on various indices of income inequality with a rich international microdata set. The main result is that highly-skilled persons are more inclined to migrate, though a higher income inequality attenuates the positive selectivity.