Poul Lassen

IPM Strategies and Their Dilemmas Including an Introduction to www. eurowheat.org

Information about disease management in winter wheat (Triticum aestiva) in eight European countries was collated and analysed by scientists and extension workers within the European Network for the Durable Exploitation of Crop Protection Strategies (ENDURE). This included information about specific disease thresholds, decision support systems, host varieties, disease prevalence and pathogen virulence. Major differences in disease prevalence and economic importance were observed. Septoria tritici blotch (Mycosphaerella graminicola) was recognized as the most yield reducing disease in countries with intensive wheat production, but also rust diseases (Puccinia striiformis and Puccinia triticina), powdery mildew (Blumeria graminis) and Fusarium head blight (Fusarium spp.) were seen as serious disease problems. Examples of current integrated pest management (IPM) strategies in different countries have been reported. Disease management and fungicide use patterns showed major differences, with an average input equivalent to 2.3 full dose rates (TFI) in the UK and a TFI of 0.6 in Denmark. These differences are most likely due to a combination of different cropping systems, climatic differences, disease prevalence, and socio-economic factors. The web based information platform www.eurowheat.org was used for dissemination of information and results including information on control thresholds, cultural practices which can influence disease attack, fungicide efficacy, fungicide resistance, and pathogen virulence, which are all elements supporting IPM for disease control in wheat. The platform is open to all users. The target groups of Euro Wheat information are researchers, advisors, breeders, and similar partners dealing with disease management in wheat.

Yellow Rust epidemics worldwide were caused by Pathogen Races from divergent genetic lineages

We investigated whether the recent worldwide epidemics of wheat yellow rust were driven by races of few clonal lineage(s) or populations of divergent races. Race phenotyping of 887 genetically diverse Puccinia striiformis isolates sampled in 35 countries during 2009–2015 revealed that these epidemics were often driven by races from few but highly divergent genetic lineages. PstS1 was predominant in North America; PstS2 in West Asia and North Africa; and both PstS1 and PstS2 in East Africa. PstS4 was prevalent in Northern Europe on triticale; PstS5 and PstS9 were prevalent in Central Asia; whereas PstS6 was prevalent in epidemics in East Africa. PstS7, PstS8 and PstS10 represented three genetic lineages prevalent in Europe. Races from other lineages were in low frequencies. Virulence to Yr9 and Yr27 was common in epidemics in Africa and Asia, while virulence to Yr17 and Yr32 were prevalent in Europe, corresponding to widely deployed resistance genes. The highest diversity was observed in South Asian populations, where frequent recombination has been reported, and no particular race was predominant in this area. The results are discussed in light of the role of invasions in shaping pathogen population across geographical regions. The results emphasized the lack of predictability of emergence of new races with high epidemic potential, which stresses the need for additional investments in population biology and surveillance activities of pathogens on global food crops, and assessments of disease vulnerability of host varieties prior to their deployment at larger scales.