Submitted to: APSnet Resource Center
Publication Type: Other
Publication Acceptance Date: 8/1/2000
Publication Date: N/A
Technical Abstract: This is one of a series of lesson plans in plant pathology intended for introductory graduate level courses in plant pathology. Each lesson plan in the series describes a plant disease of economic importance and historical significance that was chosen for its value in illustrating key principles of plant disease diagnosis and management. Stem rust has been the most destructive disease of wheat throughout most of the wheat producing regions of the world from the origin of cultivated wheat up to recent times. The lesson plan describes the life cycle of Puccinia graminis, the wheat stem rust fungus; symptoms of the disease; epidemiology including sources and spread of inoculum; methods of managing the disease including approaches to breeding stem rust resistant wheat; and economic significance of the disease historically and at the present time. Wheat stem rust is a classic example of a polycyclic disease with a rapid rate of increase over successive generations of pathogen reproduction. Epidemics of wheat stem rust can occur on a continental scale. The fungus has a classic rust life cycle with five spore stages on two distinct host types: urediniospores, teliospores, and basidiospores on wheat; and pycniospores and aeciospores on barberry, the alternate host, which are necessary for sexual reproduction by the fungus. Teliospores are dormant through the winter and germinate in the spring, producing basidiospores that infect barberry. Infections in barberry produce aeciospores that infect wheat. Where barberry is absent, urediniospores are the only spores that infect wheat. In the southern U.S., the fungus survives the winter in infected wheat and produces urediniospores that spread north and carry the epidemic to spring sown wheat.