The ever more frequent and severe large-scale epidemics of wheat yellow/stripe rust disease (caused by Puccinia striiformis) pose a severe threat to the world’s wheat production (Hovmøller et al. 2010). The onset of a new series of world-wide wheat yellow rust epidemics in 2000 has been linked to the emergence of two high temperature-adapted aggressive P. striiformis strains (named PstS1 and PstS2), first detected in 2000 (Hovmøller et al. 2008). The origin however of these aggressive strains was unknown. Here we report the development of rapid-to-use SCAR markers for PstS1 and/or PstS2 from previously detected AFLP polymorphisms, which uniquely separate these strains from any other P. striiformis isolate. The aggressive strain-specific SCARs, as well as 20 SSR markers (Enjalbert et al. 2002, Bahri et al. 2009), were applied on 570 isolates of P. striiformis collected from 41 countries on six continents to assess genetic association with strains PstS1 and PstS2. Comparison of the microsatellite profile of these isolates with the previously genotyped worldwide populations (Ali et al., in prep.) suggested the Middle East/Red Sea Area as the origin of the aggressive strains. The combination of SCAR and microsatellite data provided insights to the evolution of these two strains. Based on the marker screening we will provide an update about the global status of the occurrence and virulence spectra of aggressive strains and close relatives.
Proceedings of the 13th International Cereal Rusts and Powdery Mildews Conference: Beijing, China, 28 August-1 September 2012, 2012