For over 20 years, trees of Aesculus spp. have been attacked by the larvae of Cameraria ohridella, which causes damage to the leaves. It has been observed that members of the genus Aesculus are characterized by diverse susceptibility to C. ohridella. Four specimens of the Aesculus genus which differ in susceptibility to this leaf miner-Aesculus turbinata (susceptible), Aesculus 9 neglecta (resistant) and two specimens of Aesculus hippocastanum (relatively susceptible and relatively resistant)-were examined. The levels of substances which may function as attractants (chloroplast pigments, anthocyanins), deterrents or repellents (flavonols, phenols), or a source of nutrients (free a-amino acids and carbohydrates) were determined in leaves of these four trees during two growing seasons. The results showed that the more pestsusceptible A. turbinata had, in both growing seasons, significantly higher levels of leaf carbohydrates and anthocyanins than the resistant Ae. 9 neglecta. Thus, anthocyanins and carbohydrates may be the traits which affect oviposition preference and favor the feeding of C. ohridella in the susceptible Ae. turbinata. The relatively susceptible specimen of Ae. hippocastanum contained slightly higher carbohydrate and anthocyanin levels than the relatively resistant one, but only in one growing season. Therefore, it does not explain the causes of their different susceptibility to the pest. The concentration of phenolics in the susceptible Ae. turbinata tree and the relatively susceptible Ae. hippocastanum individual was higher than in the resistant Ae. 9 neglecta and relatively resistant Ae. hippocastanum, respectively. This may suggest that leaf phenolic composition, but not overall concentration, is responsible for different susceptibility of examined trees of Aesculus spp. to the horse-chestnut leaf miner. The present results also demonstrate that the determined chemical compounds do not constitute a complete description of the biochemical relationships between C. ohridella and the examined horse-chestnut trees.

The cellulolytic activity (exoglucanase, endoglucanase and b-glucosidase) of Ophiostoma ulmi (four isolates), O. novo-ulmi (19 isolates) and Ôfast-waxyÕ (five isolates) was determined in growth media containing carboxymethylcellulose (CMC) and cellulose powder. Differences in enzyme activities were observed among isolates, irrespective of the species and substrate used. Inoculation experiments on Ulmus minor with randomly selected isolates of O. ulmi (two isolates), O. novo-ulmi (five isolates) and Ôfast-waxyÕ (two isolates) were also performed. Disease was assessed as the percentage of leaves showing yellowing and browning. Ophiostoma novo-ulmi and Ôfast-waxyÕ isolates exhibited a great variability in their capacities to cause the disease. In the presence of CMC, a significant correlation between the activity of exoglucanase and b-glucosidase in vitro and virulence was found.

Horses bred nowadays are characterized by high variability of the body build. The variability concerns exterior features and skeleton features. From among the skeleton parts the skull is an element influenced by selection and environmental adaptation. The aim of these investigations was to find whether cranial traits exhibit variability in relation to the body build of horses. To do this, metric parameters of skulls of 43 horses used in the investigations were analysed with various statistical techniques. On the basis of ANOVA, Principal Components Analysis and Canonical Discriminant Analysis it was found that horses of various constitutional types exhibit differences in cranial morphology. Warm blood horses of the respiratory constitutional type have more complex nasal cavity from horses of heavier body build. A meaningful effect on craniometric variability was observed in the length and breadth of the viscerocranium. Also the height of the viscerocranium--a cranial feature of the respiratory tract, showed a high discriminating power.

SummaryData arranged in a two-way contingency table can be obtained as a result of many experiments in the life sciences. In some cases the categorized trait is in fact conditioned by an unobservable continuous variable, called liability. It may be interesting to know the relationship between the Pearson correlation coefficient of these two continuous variables and the entropy function measuring the corresponding relation for categorized data. After many simulation trials, a linear regression was estimated between the Pearson correlation coefficient and the normalized mutual information (both on a logarithmic scale). It was observed that the regression coefficients obtained do not depend either on the number of observations classified on a categorical scale or on the continuous random distribution used for the latent variable, but they are influenced by the number of columns in the contingency table. In this paper a known measure of dependency for such data, based on the entropy concept, is applied.

Abstract. Some binary traits are determined by a large number of loci. The standard approach, in this case, is to model an unobservable variable (liability) with a fixed threshold. We present a method for the estimation of the genetic additive variance component under a threshold animal model with fixed effects included. The method can be applied to data with repeated measurement per animal. The unknown parameters of the model have been estimated by Gibbs sampling. The numerical properties of the method are investigated on simulated data for a large real pedigree of breeding stock of laying hens. The algorithm shows good mixing properties, producing consistent estimates from many distinct runs. The application of the method is exemplified on fertility data recorded for the same pedigree.