First report of the southern corn rust pathogen Puccinia polysora on Zea mays in North Dakota

Abstract

Southern corn rust, caused by Puccinia polysora, is a yield-limiting disease on corn (Zea mays). As a biotrophic fungal pathogen, P. polysora requires a living host for its survival. Southern corn rust is favoured by high-temperatures and humid environmental conditions, and therefore is more prevalent in the southern United States. In August 2020, corn plants displaying signs and symptoms of southern rust were collected in a field in Grand Forks County, North Dakota. Due to its rare occurrence in the region, spores of the pathogen were isolated and analyzed morphologically, and found to be consistent with P. polysora. This identification was confirmed by PCR analysis and Sanger sequencing, and demonstrated further using Koch’s postulates. The discovery of P. polysora poses a potential threat to corn yields across North Dakota, and surveillance must be enhanced to predict possible epidemics in the future.