Stagonospora and Septoria diseases of barley, oat and rye

This paper presents a comprehensive review of the foliar diseases caused by Stagonospora and Septoria fungi on barley, oat, and rye. The relationship of the pathogens to related species that cause disease on wheat is discusse d. The diseases are more serious during periods of cool wet weather and are more prevalent in northern Europe and North America. They are frequently a ssociated with the planting of highly susceptible cultivars. The biotype of Stagonospora nodorum that infects barley differs significantly from the bi otype that attacks wheat and is occasionally important in the southeastern U.S.A. and northern Europe. Stagonospora avenae f. sp. triticea infects bar ley, rye, and wheat. It is usually a minor pathogen of barley and rye, but these hosts may serve as an inoculum reservoir for infection of wheat. Stag onospora avenae f. sp. avenaria causes stagonospora leaf blotch and black s tem on oat. The black stem phase of the disease causes significant yield re duction and is frequently important in eastern Canada. Morphological charac teristics and host range are similar among the Stagonospora species. Teleom orphs of these fungi are in Phaeosphaeria, and the epidemiological importan ce of this state varies with each pathogen. Septoria passerinii causes spec kled leaf blotch on barley. It has become increasingly important in recent years in north central North America and may be associated with reduced til lage. Septoria tritici f. avenae occurs infrequently on oat, and Septoria s ecalis causes a minor disease on rye. Teleomophic states of these Septoria species have not been identified. Resistance to Stagonospora nodorum has be en identified in barley and to Stagonospora avenae f. sp. avenaria and Sept oria passerinii in the cultivated hosts and wild relatives. Race-specific r esistance has not been identified and resistance is primarily partial resis tance. Recent use of molecular genetics is providing a clearer understandin g of the relationships among these and related pathogens on wheat and grass es.