Breakdown of the Yr17 resistance to yellow rust of wheat in northern Europe

Abstract

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

Genetic Variability in Puccinia striiformis f. sp. tritici Populations Sampled on a Local Scale during Natural Epidemics

“…Bayles et al (1) also reported that v17 isolates reached a frequency higher than 70% in 1999 in these countries. For each year and field, presence and proportions of pathotypes as defined by virulence genes were consistent with other regional surveys (1,7). We found that pathotypes 233E137V17 and 169E136V17 represented, respectively, 88.7 and 11.3% of the sampled isolates for years 1998 and 1999 ( AFLP reproducibility.…”

“…In France, natural epidemics occur usually in the northwest and occasionally in the south and are especially damaging when springs are cool and rainy (6,7,38). In most cases, the use of specific resistance genes as a disease control method has been unsuccessful because the pathogen population evolves rapidly and is able to overcome a newly introduced resistance gene within only a few years (1,32,36). Other methods have been investigated, such as pathotypenonspecific resistance or cultivar mixtures (37), but more detailed data about the genetic structure of natural populations are needed to understand and predict their efficacy.…”

Advanced Breeding Strategies to Mitigate the Threat of Yellow Stripe Rust of Wheat

“…Recently, YR has become a serious threat to wheat, causing 50-100 % yield losses due to the breakdown of existing resistance genes and gradual adaptation of new strains in warmer regions, particularly the Central and West Asia and North Africa (CWANA) region (ICARDA, 2011). The breakdown of the widely used race-specific genes (R-genes) Yr17 (Bayles et al, 2000;Wan et al, 2004;Chen 2007), Yr27 (Singh et al, 2004;Wan et al, 2004), Yr31 Rosewarne et al, 2012), and Lr24 (Park et al, 2002) has created a serious challenge for wheat scientists and growers worldwide. Introducing genetic resistance into cultivars is the most economic and environmentally safe measure of rust disease management in wheat.…”

Emergence of new virulence in Plasmopara halstedii (sunflower downy mildew)

“…Both the resistance and virulence are inherited as single genes (Pedley and Martin, 2003). There are many recorded examples of directional selection leading to invasion of pathogen populations by virulent isolates, and hence resistance breakdown (Jacobs and Parlevliet, 1993;Bayles et al, 2000). However, there are some cases demonstrating that single R gene can conifer highly durable resistance (Kolmer, 1993;Parisi et al, 1993).…”