Occurrence of new races and virulence changes of the wheat stripe rust pathogen (Puccinia striiformisf. sp.tritici) in Egypt

Wheat stripe rust, caused byPuccinia striiformistritici(Pst), is a widespread disease of wheat, and causing significant losses in yield. Twenty-five races were identified from 160 samples in greenhouse tests. Samples were collected from wheat fields in governorates; Kafrelsheikh, Al-Sharqia, Dakahlia and Gharbia were tested. The most important commercial wheat cultivars,i.e.Misr1, Misr2, Giza171, and Sakha61, which were resistant to the previously characterised races in Egypt, became susceptible under field conditions. Also, infections of stripe rust were observed on some wheat lines withYrgenes previously known to be resistant,i.e.Yr1, Yr17, Yr27, Yr32andYrSpin trap nurseries. The results confirmed a new race that is virulent toYr1, which was first detected in Egypt. In addition, a race very similar to the Warrior race with virulence toYr1, Yr2, Yr3, Yr4, Yr6, Yr7, Yr9, Yr17, Yr25, Yr32, YrSpandYrAmbwas also confirmed in the 2015/2016 growing season. The detection of the new races indicated continual changes of virulence in thePstpopulation. Due to these new races, some wheat cultivars previously known to be resistant have become susceptible. This is the first report of the Warrior race of wheat stripe rust in Egypt.