New races of Tilletia laevis and T. caries, the causal agents of wheat common bunt in Khuzestan province, Iran1

In Iran, common bunt of wheat is one of the most important diseases of wheat and using resistant varieties is the best strategy against it. In order to find resistance sources against the disease for effective breeding programs, determining races of the pathogen is critical. In this study, spikes infected with common bunt of wheat were collected from different farms of Khuzestan province in 2005-2006. Tilletia laevis and T. caries were identified as the causal agents of the disease. Twenty selected isolates were inoculated on differential genotypes and planted in farm condition. Fifteen different pathogenic races were identified in this study; L-19, L-21, and L-1 (for T. laevis) T-11, T-1, T-2 and T-31 (for T. caries). Except L-21 and L-1, other races were reported for the first time in Iran until 2008. Also eight pathogenic races were identified based on virulence/avirulence patterns in this study. Results showed that host resistance genes Bt6 and Bt14 were effective against races of T. laevis, and host resistance genes Bt5, Bt6, Bt10 and Bt14 were effective against races of T. caries in Khuzestan province.