Incursion of a new aggressive Puccinia striiformis f.sp. tritici race in Syria and Lebanon in 2010-2011

Stripe (yellow) rust is the most important disease of wheat in the Central, West Asia and North Africa (CWANA) region. Severe epidemics in 2010 caused more than 30% yield losses in Syria, and similar losses could have occurred in Turkey, Uzbekistan and Iraq. Extensive field surveys were conducted in major bread and durum wheat areas in Syria in 2011 using the BGRI surveillance protocols. Stripe rust was present in wheat growing areas in northern, northeastern, and eastern parts of the country. A total 223 samples were collected from 61 fields from which 55 isolates were used in seedling race analysis. A sub-set of Avocet-based differential lines, Avocet YrA, Yr8, Yr9, Yr15, Yr17, Yr25, Yr27 and Yr32, was used as a supplementary set to the world and European sets1 (de Vallavieille-Pope et al., 2012). The analysis indicated virulence for the widely deployed resistance genes Yr2, Yr6, Yr7, Yr9, Yr25 and Yr27. Resistance genes Yr1, Yr4, Yr5, Yr10, and Yr15 were effective against all isolates. Virulence for Yr3, Yr8, Yr17, YrSu, YrSD, YrSP, and Yr32 occurred at varying frequencies. Genotyping of 92 Pst isolates with 20 microsatellite markers2 (Ali et al., 2011) showed that relatively few genotypes were in Syria in 2011. These genotypes were closely related to previously reported aggressive races with high temperature adaptation which are widespread worldwide since 20003 and were less diverse than the population sampled earlier in Middle East