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 discussed. The diseases are more serious during periods of cool wet weather and are more prevalent in northern Europe and North America. They are frequently associated with the planting of highly susceptible cultivars. The biotype of Stagonospora nodorum that infects barley differs significantly from the biotype that attacks wheat and is occasionally important in the southeastern U.S.A. and northern Europe. Stagonospora avenae f. sp. triticea infects barley, 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. Stagonospora avenae f. sp. avenaria causes stagonospora leaf blotch and black stem on oat. The black stem phase of the disease causes significant yield reduction and is frequently important in eastern Canada. Morphological characteristics and host range are similar among the Stagonospora species. Teleomorphs of these fungi are in Phaeosphaeria, and the epidemiological importance of this state varies with each pathogen. Septoria passerinii causes speckled leaf blotch on barley. It has become increasingly important in recent years in north central North America and may be associated with reduced tillage. Septoria tritici f. avenae occurs infrequently on oat, and Septoria secalis causes a minor disease on rye. Teleomophic states of these Septoria species have not been identified. Resistance to Stagonospora nodorum has been identified in barley and to Stagonospora avenae f. sp. avenaria and Septoria passerinii in the cultivated hosts and wild relatives. Race-specific resistance has not been identified and resistance is primarily partial resistance. Recent use of molecular genetics is providing a clearer understanding of the relationships among these and related pathogens on wheat and grasses.