Yield Losses in Winter Barley Resulting from a New Race ofPuccinia hordeiin North America

Leaf rust resistance, derived from the barley cultivar Cebada Capa, has been effective in the southeastern United States since 1950, when it was first used in the Virginia barley breeding program. In 1990, races of Puccinia hordei virulent to barleys that possess the resistance gene Rph7 were identified for the first time in North America. This research assessed the potential impact of Rph7-virulent races of leaf rust on grain yield and quality in winter barley. Natural epidemics of leaf rust occurred in cultivar trials at Painter and Warsaw, Virginia, in 1991 and 1992. Mean leaf rust severities for barley lines observed over three environments ranged from 10% for the moderately resistant line VA 90-42-45 to 76% for the susceptible cultivar Barsoy