Characterization of the Northwestern Population of <i>Puccinia striiformis</i> f. sp. <i>tritici</i> on the Basis of Virulence and Representation of Invasive <i>PstS1</i> and <i>PstS2</i> Races

Abstract

The expansion of the area of significance of yellow rust was observed in the last years. Until recently, in the conditions of the North-West, the disease occurred sporadically. However, in recent years, its strong development has been observed on wheat samples studied on the collection fields of scientific research institutes and State variety plots, as well as on some commercial fields in the Leningrad region. The aim of this work is to study the virulence and racial composition of the yellow rust pathogen in the Northwest and to conduct a molecular analysis of population samples for the presence of invasive races PstS1 and PstS2. Leaves of common wheat samples with of Puccinia striiformis urediniopustules were collected on commercial fields, State variety plots and experimental fields of the Research Institutes in 2020–2022. Near isogenic Avocet lines (Av NIL) with genes Yr1, Yr5, Yr6, Yr7, Yr8, Yr9, Yr10, Yr15, Yr17, Yr18, Yr24, Yr26, YrSp, Yr27 and differential varieties from international [Chinese 166 (Yr1), Lee (Yr7, Yr+), Heines Kolben (Yr6, Yr+), Vilmorin 23 (Yr3), Moro (Yr10, YrMor), Strubes Dickkopf (YrSD, Yr25, Yr+), Suwon 92/Omar) (YrSu, Yr+)] and European [Hybrid 46 (Yr4, Yr+), Reichersberg 42 (Yr7, Yr+), Heines Peko (Yr2, Yr6, Yr25, Yr+), Nord Desprez (Yr3, YrND, Yr+), Compair (Yr8, Yr19), Carstens V (Yr32, Yr25, Yr+), Spaldings Prolific (YrSP, Yr+), Heines VII (Yr2, Yr25, Yr+)] sets used for characteristic of pathogen virulence. Set of SCAR markers (SCP19M24a1, SCP19M24a2, SCP19M26a1, SCP19M26a2) used for identification of invasive races. A total 92 isolates were studied. High effectiveness at the seedling stage had genes Yr5, Yr10, Yr15, Yr24, Yr26. Isolates virulent to differential varieties Moro (Yr10, YrMor) and Nord Desprez (Yr3, YrND, Yr+) was not determined. Virulence to wheat genotypes with Yr17 gene was rare. Twenty-four virulence phenotypes identified using 29 virulence testers. The number of virulence alleles varied from 7 to 21. At the same time, differences between the phenotypes of P. striiformis on the studied common wheat varieties were insignificant. Most of them have united in a common group. Two groups of isolates slightly differentiated from them. The first included isolates from varieties characterized by a smaller number of virulence alleles, the second – with the maximum number of virulence alleles. Molecular analysis of the northwestern po-pulation revealed isolates belonging to the invasive PstS2 group in 2020 and 2022. Their virulence did not differ significantly from other northwestern phenotypes. The high evolutionary potential predetermines the need for annual monitoring of pathogen populations based on virulence and representation of invasive races.