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.

Comparison of Resistance Rates and Detection of Five Resistance Genes (Bts) in Ten Local Wheat Varieties against Common Bunt Disease

“…foetida and T. caries fungal pathogens are the major actors for common bunt disease [2]. This disease is very dangerous seedborne disease for wheats and causes heavy losses in yield quality and quantity [1][2]. At present, Tilletia species can be effectively controlled using fungicide treated seeds, however, due to the distribution difficulties and high costs of the chemical treated seeds, use of pathogen resistant cultivars is preferred in most of the seed breeding programs world-wide [3,8].…”

“…Resistance genes in wheat served to select the virulent types from the pathogen population [9]. These resistance genes are named bt and include fifteen genes (bt1-bt15) [1,10]. The availability of the microsatellite markers (SSRs) transmitted in linkage with some common bunt resistance genes could accelerate the process of breeding and selection.…”

“…However, due to the availability of effective chemical treatments, resistance to bunt was not important for breeders and farmers in past decades [5]. The disease has re-emerged and has caused enormous yield losses, especially when susceptible cultivars have been grown [1].…”

“…Common bunt is the major seedborne disease posing a threat to wheat production. [1,3]. The disease is still a major problem, especially in North Africa and West Asia [3][4][5].…”

“…The disease is still a major problem, especially in North Africa and West Asia [3][4][5]. Recent bunt outbreaks, contamination especially with T. foetida and T. caries spores of wheat has become a problem resulting in losses in yield and seed quality [1,[5][6]. Common bunt is easily controlled by chemical seed treatments, and has reduced the disease to an insignificant problem in worldwide, but the disease continues to cause serious losses in areas of North Africa and West Asia [1-2, 4-5, 7].…”