A New Pathogenic Race of Tilletia caries Possessing the Broadest Virulence Spectrum of Known Races

Abstract

Common bunt, caused by the fungi Tilletia caries and T. laevis, is one of the most destructive seedborne diseases of wheat. In conventional agriculture, common bunt is managed almost exclusively with chemical seed treatments. However, in organic farming, synthetic chemicals are prohibited. Because of this, there has been a resurgence of this disease in organic wheat. In order to maintain high yields and excellent seed quality, organic growers must rely heavily on resistant wheat cultivars. To breed cultivars with resistance against common bunt, and to effectively deploy resistance genes, it is necessary to identify and monitor the pathogenic races of the local pathogen population. Towards this goal, races of T. caries present in Washington, Oregon, California, and Idaho were identified by inoculating field collections of the pathogen on 13 differential wheat cultivars. Results of three years' testing show that there is a new pathogenic race in Washington State, which possesses the broadest virulence spectrum to date compared with known bunt races. Furthermore, two-year data indicates the presence of other new races in Washington, California, and Oregon. Accepted for publication 5 April 2011. Published 20 May 2011.