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Pathogens of bark beetles (Coleoptera: Curculionidae) in Bulgarian forests

The occurrence and prevalence of bark beetle pathogens in forest stands in Bulgaria were investigated in 944 specimens belonging to 21 bark beetle species. Protozoa, microsporidia, fungi and nematodes occurred in 19 of all investigated species. The infections were found in the gut (nematodes, gregarines, microsporidia), gonads (microsporidia) and hemolymph (nematodes) of the infected insects. Protozoan species (Gregarina typographi, Gregarina spp.) were detected in eight bark beetle species. Morphometric data about G. typographi and Gregarina spp. are presented. The prevalence of the gregarines varied between 1.4% and 64.2%. Microsporidia of the genera Nosema and Chytridiopsis were revealed in three bark beetle species. The prevalence of microsporidia ranged between 1.5% and 11.8%. This is the first report of a microsporidium in Taphrorychus villifrons and of gregarines in T. villifrons, Pityogenes bistridentatus, P. conjunctus, and Orthotomicus erosus. The fungus Beauveria bassiana was found in 3.4% of Hylurgops palliatus specimens. Nematodes (in gut and haemolymph) were revealed in 19 bark beetle species and their prevalence varied between 10% and 98.5%.     

Gesunde Pflanzen unter zukünftigem Klima

Predicted changes in average values of global climate variables (increased temperatures, altered precipitation patterns, increased concentrations of atmospheric CO₂) and changes in the frequency, duration, and degree of extremes (frost, heat, drought, hail, storms, floods, etc.) will affect agricultural crops, agroecosystems, and agricultural productivity. Although forecasts of regional climate changes are still imprecise, mean temperature increases in Europe are expected to be greater in the north (2.5–4.5°C) than in the south (1.5–4.5°C). Regional forecasts for precipitation changes are also very far from precise; however, problems with drought are expected to increase, especially in Mediterranean countries. Overall, shortage of water will be the predominant factor affecting plant growth. As higher temperatures are known to enhance plant development and especially the grain-filling duration of cereals, grain yield losses are possible in a warmer climate. On the other hand, elevated atmospheric CO₂ concentrations are known to stimulate photosynthesis and enhance growth and yield (“CO₂ fertilization”); concomitantly, leaf transpiration is reduced, resulting in improved water use efficiency. Total biomass and yield were enhanced by 20–30% in experiments with elevated CO₂ exposure (550–700 ppm) under more or less ideal growth conditions. Elucidating the interactions between positive and negative effects of climate change is of crucial importance for any prediction of future crop yields. The present paper is a brief summary mainly of the potential effects of elevated temperatures and atmospheric CO₂ on crop growth, quality, and yield. Also, adaptation measures, possible interactive effects of different climate variables, and interactions of climate change components with other growth variables (pathogens, air pollutants) are briefly described.     

Die Breitadrigkeit des Salats — ein Komplex aus zwei Viren

Since many years lettuce big-vein disease (LBVD) occurring in lettuce (Lactuca sativa) and endivia (Cichorium endivia) is a well known disease. It is widely spread all over the world and can cause important economical losses. For more than 20 years the lettuce big-vein virus (LBVV) was thought to be the causal agent. New results indicate that another virus, named “Mirafiori lettuce big-vein ophiovirus” (MLBVV), is responsible for the typical symptoms. Mostly both viruses are detected together in diseased plants. But also the presence of only one virus can be observed as shown in a sample which was sent to the Bavarian State Research Center for Agriculture (LfL), Freising, in the spring of 2005. In further investigations at the German Federal Authority and Federal Research Centre (BBA), Braunschweig, only the MLBVV was found. Like any other virus disease LBVD cannot be controlled directly. Therefore prevention is of utmost importance. If LBVD is already present integrated disease management strategies combining cultural and phytosanitary measures as well as growing tolerant lettuce cultivars are the only way to minimize economical damage.     

Giftpulver und Trägerstaub in der Flugzeugstäubung zur Malariabekämpfung

Zusammenfassung In der Flugzeugstäubung zur Brutplatzsanierung in der Malariamückenbekämpfung setzt sich das Streugemisch aus zwei Komponenten zusammen: Gift und Verteilerstoff. Die Giftpartikelchen sollen möglichst lange auf dem Wasser liegenbleiben, damit sie recht lange als Fraß- oder Berührungsgift wirken können. Der Verteilerstoff (in der Praxis am besten Straßenstaub) soll das gleichmäßige Ausstreuen des Giftes ermöglichen, er soll jedoch nicht auf der Wasseroberfläche liegenbleiben, sondern alsbald absinken. Erfahrungen mit der Einführung einer dritten Komponente in Gestalt verölter Staubpartikelchen, die dann als eigentlicher Trägerstoff für die Giftpartikelchen dienen, versprechen durch diese Methodik sowohl eine Giftersparnis infolge höherer Wirkung wie auch gleichzeitig längere Wirkungsdauer, d. h. Vergrö ßerung der zeitlichen Abstände der Wiederholungen der Streuflüge.     

Is single-step genomic REML with the algorithm for proven and young more computationally efficient when less generations of data are present?

Efficient computing techniques allow the estimation of variance components for virtually any traditional dataset. When genomic information is available, variance components can be estimated using genomic REML (GREML). If only a portion of the animals have genotypes, single-step GREML (ssGREML) is the method of choice. The genomic relationship matrix (G) used in both cases is dense, limiting computations depending on the number of genotyped animals. The algorithm for proven and young (APY) can be used to create a sparse inverse of G (GAPY~-1) with close to linear memory and computing requirements. In ssGREML, the inverse of the realized relationship matrix (H⁻¹) also includes the inverse of the pedigree relationship matrix, which can be dense with a long pedigree, but sparser with short. The main purpose of this study was to investigate whether costs of ssGREML can be reduced using APY with truncated pedigree and phenotypes. We also investigated the impact of truncation on variance components estimation when different numbers of core animals are used in APY. Simulations included 150K animals from 10 generations, with selection. Phenotypes (h² = 0.3) were available for all animals in generations 1–9. A total of 30K animals in generations 8 and 9, and 15K validation animals in generation 10 were genotyped for 52,890 SNP. Average information REML and ssGREML with G⁻¹ and GAPY~-1 using 1K, 5K, 9K, and 14K core animals were compared. Variance components are impacted when the core group in APY represents the number of eigenvalues explaining a small fraction of the total variation in G. The most time-consuming operation was the inversion of G, with more than 50% of the total time. Next, numerical factorization consumed nearly 30% of the total computing time. On average, a 7% decrease in the computing time for ordering was observed by removing each generation of data. APY can be successfully applied to create the inverse of the genomic relationship matrix used in ssGREML for estimating variance components. To ensure reliable variance component estimation, it is important to use a core size that corresponds to the number of largest eigenvalues explaining around 98% of total variation in G. When APY is used, pedigrees can be truncated to increase the sparsity of H and slightly reduce computing time for ordering and symbolic factorization, with no impact on the estimates.     

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