Isolates of recently spreading races of yellow rust from wheat and triticale in Europe were analysed using virulence phenotypic data of 2605 isolates sampled in 12 countries between 2000 and 2014. A subset of 239 isolates was investigated by microsatellite markers. At least three races of non-European origin, termed 'Warrior', 'Kranich' and 'Triticale aggressive', were identified in the post-2011 population. The Warrior race was already present in high frequencies in the first year of detection in most European countries and to a large extent it replaced the pre-2011 European population. In contrast, the two other exotic races were localized to certain regions and/or crop type. The presence already of at least six multilocus genotypes of the Warrior race and five genotypes of the Kranich race in the first year of detection and across large areas is consistent with a hypothesis of aerial spread from genetically diverse source populations. A comparison with reference isolates sampled from six continents suggested that the Warrior and Kranich races originated from sexually recombining populations in the centre of diversity of the yellow rust fungus in the near-Himalayan region of Asia. However, the Triticale aggressive race was most similar to populations in the Middle East/Central Asia. The study illustrated the potential role of sexual Puccinia striiformis populations as a reservoir for new races replacing distant clonal populations.

The presence of foliar pathogens often leads to yield losses in winter wheat (Triticum aestivum L.), the most important crop in Germany. In this study the efficacy of different host resistance levels of eight wheat cultivars and three fungicide strategies on fungal disease control was studied in terms of yield and net return in field trials at five sites over three crop years. Fungicide treatments included a situation-related strategy in which cultivars were treated individually based on disease control thresholds, a practice-related strategy in which all cultivars were treated after disease thresholds had been exceeded in one cultivar, and an untreated control. Disease severity and incidence differed between cultivars and were reduced by fungicide treatments compared to the untreated control. On average over all locations and years, the Fungicide Treatment Frequency Index (TFI) of all cultivars treated with the situation-related strategy was significantly lower than those treated with the practice-related strategy, except the highly susceptible cultivar JB Asano. A reduction of the TFI by up to 82% was possible in the situation-related strategy. Despite slightly increased yields in the practice-related strategy compared to the situation-related strategy, these could not compensate for the higher fungicide costs in most cases and led to lower net returns. The cultivars with multi-disease resistance showed clear advantages. Their potential benefits are not only demonstrated by the attainment of high yields, but also in fungicide savings without reducing net returns, provided that their disease resistance characteristics are taken into account.