Virulence diversity of the yellow rust pathogen population in Dagestan

Abstract

Background. Yellow rust incidence on Triticum L. has been observed to surge up in Dagestan in recent years, facilitating selection of highly resistant genotypes. Information on the effectiveness of Yr genes and the pathogen’s virulence and racial composition is needed to interpret field assessment data correctly. The objective of this study was to describe the virulence of the Dagestan population of Puccinia striiformis West. at the seedling stage, evaluate the resistance of differentiators to yellow rust in the field, and identify invasive PstS1 and PstS2 races.Materials and methods. Leaves with urediniopustules were collected from bread wheat accessions at Dagestan Experiment Station of VIR (DЕS VIR) in 2020–2022. Virulence was analyzed in the laboratory using 14 AvYr lines (Avocet NIL) and 15 differential wheat cultivars. Age-specific resistance of virulence testers under high natural infection pressure was studied in the field of DES VIR. A set of SCAR markers (SCP19M24a1, SCP19M24a2, SCP19M26a1, and SCP19M26a2) were used to identify invasive races.Results and discussion. Avocet lines with Yr5, Yr10, Yr15, Yr24, and Yr26, and cv. ‘Moro’ (Yr10, YrMor) manifested resistance to all isolates. Virulence to Yr17 was detected only in the isolates from cvs. ‘Graf’ and ‘Svarog’ carrying this gene, and ‘Siete Ceros’. The Dagestan collection demonstrated high genetic diversity. Common phenotypes were identified on cv. ‘Graf’ in 2021 and 2020. There was no temporal differentiation between pathogen collections in the years of testing. High field resistance to yellow rust was recorded in lines with Yr5, Yr8, Yr10, Yr15 and Yr24, and in cvs. ‘Moro’, ‘Compair’, ‘Carstens’ and ‘Spaldings Prolific’. Cvs. ‘Reichersberg 42’ and ‘Heines Peko Vilmorin 23’ were resistant in 2020 and 2022, and moderately affected (up to 10%) in 2021. Molecular analysis identified all three isolates belonging to the invasive PstS2 group on cv. ‘Siete Cerros’ and L 650 in 2021, and cv. ‘Vassa’ in 2022.