Identification of Wheat Leaf Rust Races Present in Uruguay during

Abstract

Leaf rust (LR), caused by Puccinia triticina Ericks, is one of the most prevalent wheat diseases in Uruguay and other countries of the Southern Cone. The economic importance of the disease is clear considering that, in severe epidemics, grain yield losses of more than 50 % have been determined and that two or more fungicide applications are necessary to control the disease in susceptible cultivars. Studies on the pathogen variability are important to determine its range of virulence, infer the mechanism of its variation, determine the origin and spread of pathotypes, complement the knowledge of the resistance of commercial cultivars, confirm the presence of new races inferred by change of the host reaction, and identify races important for breeding and specific studies. The objective of this research was to study the diversity in the P. triticina population in Uruguay during 2011 and 2012. A total of 363 LR samples collected at different times from different cultivars and locations of the crop area were studied. The prevalence of 22 identified races (higher to lower frequency: MFP; TDT-10,20; MDP; MDT-10,20; TFT-10,20; MFP-20; MFP-10,20; MDP-20; DBB-10,20; MKD-10; TPR-20,39; MFT-10,20; MDP-10,20; MDR-10,20; MFT; MDT; MFP-10; MHJ-10; MJD-10; TMD-10,20; MCP; MFR-10,20), was related to the virulence on cultivars used by farmers. The presence or frequency of the races varied among years, zones and time of collection. Two races not previously reported were detected. This study confirmed that the pathogen population present in Uruguay is diverse and continues to evolve.