Occurrence and characterization of Puccinia triticina in Zimbabwe

Wheat leaf rust caused by Puccinia triticina (Pt) is an important disease of bread wheat in Zimbabwe. This study was carried out to determine the distribution, avirulence/virulence profile(s) and genotypic variation among isolates of the pathogen. In total, 104 single-pustule isolates were established from infected wheat samples that were collected from the main wheat production regions in Zimbabwe in surveys conducted from 2019 to 2021. Phenotyping of the isolates on a set of 46 differential and additional wheat lines revealed a single Pt race, MCDS. For genotypic assessment, 48 Pt isolates, including eight South African races, were genotyped with 19 microsatellite markers. Using the Bayesian model, isolates were subdivided into three clusters in both a DARwin neighbour-joining tree and STRUCTURE analysis. The results confirmed a high genetic similarity between the Zimbabwean Pt isolates and the South African races MCDS, MCPS and MFPS. Furthermore, Pt isolates from Zimbabwe were clonal, which was in accordance with all 104 isolates that typed to race MCDS.