Highly Aggressive Invasive Race Group PstS2 in Russian Populations of the Wheat Yellow Rust Pathogen

Abstract

Abstract The expansion of the area of harmfulness of the wheat yellow rust pathogen (Puccinia striiformis) (Pst) has be observed all over the world in the 2000s. This is due to the emergence of new highly aggressive invasive groups of races PstS1 and PstS2, adopted to the high temperatures, and also as a result of virulence mutations of regional pathogen populations. SCAR-markers were developed for identification of invasive races, and pathogen collections from many countries were studied. In these studies in first in Russia, the analysis of regional populations of P. striiformis for the presence of invasive races PstS1 and PstS2 was carried out. Single pustule isolates were obtained from urediosamples collected from common and durum wheat, triticale and wild grasses in seven regions of the Russian Federation (North Caucasian, Northwestern, Central Black Earth, Lower Volga, Middle Volga, Volga–Vyatka, West Siberian) in 2019–2020. In total 82 isolates were studied. Using SCAR markers, three genotypes were identified in the studied collection of P. striiformis, and one of which belongs to the invasive group PstS2. The other two genotypes had a different origin (other). Isolates of PstS2 group were received from pathogen population samples collected in the Russian Northwest in 2020. Virulence analysis revealed two phenotypes among them: PstS2_R1 (3 isolates) and PstS2_R2 (1 isolate). According to information from the Global Rust Reference Center (http://www.wheatrust.org/), the main characteristic of isolates from invasive PstS2 group is virulence to wheat lines with resistance genes Yr2, Yr6, Yr7, Yr8, Yr9, and Yr25. The Russian R1 phenotype PstS2 was also characterized by virulence to these genes, as well as to Yr1, Yr32, and YrSp. The PstS2_R2 phenotype differed from PstS2_R1 for avirulence to Yr25 and virulence to Yr3 and Yr4. The main difference of Russian PstS2 isolates with detected in other countries is virulence to wheat lines with genes Yr4, Yr32, and YrSp. The first detection of invasive races in the Northwest of Russia indicates the relevance of annual monitoring of regional populations of P. striiformis.