ABSTRACT
The development of improved strategies for deployment of host resistance and of fungicides for disease control requires knowledge of the composition of the pathogen population. This is of particular importance for wind-dispersed diseases like Erysiphe graminis f. sp. hordei, causing mildew of barley. By means of a Schwarzbach jet spore sampler representative samples of spores have been taken from the atmosphere along transects through important barley growing areas from France and Italy to Denmark and from Scotland to Austria. Progenies of single spores were analysed both for virulence against the main resistance genes present in European commercial varieties and for resistance against the most important groups of systemic fungicides. Distinct patterns of frequencies of virulence and of different levels of fungicide resistance were obtained. The results can be used as a basis for cultivar diversification and for the choice of appropriate fungicides. General rules of evolution could be recognised during the recent past and might be used to direct the future evolution. Besides the influence of the regional barley cultivation, basic features of the drift of mildew populations throughout Europe were detected, demonstrating large parts of Europe to be an epidemiologic unit. A system for the Europe-wide use of host resistance and of fungicides is described to provide a demonstration of the basic principles involved.
