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.

International audienceThe gene Yr17, conferring resistance to Puccinia striiformis f.sp.tritici, was introduced into northern European wheat cultivars in the mid 1970s. Virulence for Yr17 was not detected until 1994, when it was identified in the UK and Denmark. In both countries, susceptible Yr17 cultivars were grown on an increasingly large area over the next four years and this was followed by a rise in the frequency of corresponding virulence to 100% . Elsewhere in northern Europe Yr17 cultivars were grown on a relatively small scale during this period. However, virulence for Yr17 was detected in France and Germany in 1997 and reached a frequency in excess of 70% by 1999, suggesting an influx of pathogen spores from UK or Denmark. Migration of pathogen spores around northern Europe clearly plays an important role in determining the virulence composition of local populations of Puccinia striiformis f. sp. tritici. It is vital that this should be reflected in cooperation between national virulence monitoring projects.Contournement du gène de résistance Yr17 à la rouille jaune du blé en Europe du Nord. Le gène de résistance Yr17 vis-à-vis de Puccinia striiformis f. sp. tritici, agent de la rouille jaune du blé, a été introduit dans les cultivars Nord-Européens à partir de 1975. La virulence correspondante n'a été détectée qu'en 1994 en Angleterre et au Danemark. Dans ces deux pays, la superficie des terres emblavées par des cultivars portant Yr17 et sensibles à la rouille jaune a augmenté de 1994 à 1997 et est restée très importante jusqu'en 1998. La virulence vis-à-vis de Yr17 a atteint 100 % . Dans les autres pays du Nord de l'Europe, les cultivars Yr17 sensibles à la rouille jaune ont été cultivés sur de petites surfaces. Toutefois la virulence vis-à-vis de Yr17 a été détectée en France et en Allemagne en 1997 avec une fréquence de plus de 70 % en 1999, suggérant une migration des spores du parasite à partir de l'Angleterre ou du Danemark. La migration des spores joue un rôle déterminant dans la composition des populations locales de P. striiformis f. sp. tritici. Il est impératif que des projets de coopération de suivi des virulences soient coordonnés à l'échelle européenne

No abstract

An unusual stem rust infestation occurred in German wheat fields in summer 2013. This study analysed 48 isolates derived from 17 Puccinia graminis f. sp. tritici (Pgt) samples and six races were identified: TKTTF, TKKTF, TKPTF, TKKTP, PKPTF and MMMTF. Infection type and genotypic data confirmed that none of these races belonged to the TTKS (Ug99) race group. German isolates of race TKTTF are phenotypically different to the ones responsible for the stem rust epidemic in Ethiopia in 2013–2014. Forty isolates were genotyped using a custom SNP array. Phylogenetic analysis showed that these 40 isolates represented two distinct lineages (clade IV and clade V). Thirty‐eight isolates clustered into clade IV, which previously was defined by Ethiopian isolates of race TKTTF. Race TKKTP is of special concern due to its combined virulence to stem rust resistance genes Sr24, SrTmp and Sr1RSAmigo. The vulnerability to race TKKTP in US and international winter wheat was confirmed as 55% of North American and international cultivars and breeding lines resistant to race TTKSK (Ug99) became susceptible to TKKTP. Races identified in Germany in 2013 confirmed the presence of virulence to important resistance genes that are effective against race TTKSK. This information should be useful for breeders to select diverse and effective resistance genes in order to provide more durable stem rust resistance and reduce the use of fungicides.

Key messageIdentification of resistance genes to potato wart disease caused bySynchytrium endobioticumis the key for developing diagnostic markers for breeding resistant cultivars. We present an overview on the current knowledge of this host-pathogen system and molecular advances while highlighting future research focus.AbstractPotato wart is a quarantined disease of cultivated potato (Solanum tuberosum L.) caused by the obligate biotrophic, soil-borne fungus Synchytrium endobioticum (Schilb.) Perc. Since its discovery by Schilberszky in 1896, the management of wart disease was enabled by research efforts focusing on understanding and classifying the causative agent, its mode of infection, pathogenesis, geographical distribution, detection and chemical control, on developing screening methods for host resistance and on genetic analyses, which led to the development of resistant cultivars. These early successes are currently challenged by new S. endobioticum pathotypes evolving and the increased risk of dissemination by potato tuber trade. New research efforts are therefore required to ensure continuation of effective and sustainable management of the potato wart disease. Advances in molecular biology and genomic tools offer potential for innovations. This review presents an overview on what we know about this complex host-pathogen interaction, highlights recent molecular work and embarks on an outlook towards future research directions.