Overwintering potential of the stripe rust pathogen (Puccinia striiformis) in central Alberta

Abstract

In central Alberta, stripe rust (Puccinia striiformis) of wheat and barley has become more prevalent and this disease is generally more severe on winter wheat than spring wheat. This study was carried out to determine the potential role of winter wheat in overwintering and transmission of inoculum to subsequent spring crops. Field plants of winter wheat, infected in the autumn, were sampled during January to May from 2008 to 2011 in central Alberta. The pathogen's viability was established using in vivo growth parameters and pathogen detection was determined using PCR. Approximately 4–20% of urediniospores sampled from pustules on winter wheat during January to March–April of each year were viable. Latent mycelia were intermittently observed on winter wheat sampled from January to May in each of 2008 and 2010. The fungus was detected using PCR intermittently from winter to early spring. Persistent snow cover was found to be critical for the survival of overwintering inoculum, as viable pustules and urediniospores rarely survived after snow melt. There was higher stripe rust severity in spring wheat or barley seeded near winter wheat compared with the same crops seeded near spring wheat, for all years of field testing. The epidemiological significance of overwintering inoculum is discussed in relation to stripe rust management in central Alberta.