عنوان مقاله [English]
Background and Objectives
The stem rust of wheat (Puccinia graminis f.sp. tritici) is one of the most important diseases of wheat in Iran causing severe yield loss in some years in the case of favourable condition for disease epidemic. In the recent years, a new race of stem rust (Ug99) and its new variants have been emerged, which are virulent on most resistance genes, such as Sr31, Sr38, etc., and have potential to spread rapidly and cause severe yield loss. The Ug99 race was first reported in 2009 from Lorestan and Hamadan provinces of Iran.
Materials and Methods
Results of a recent study conducted during 2011-2013 in Iran showed virulence on Sr36, Sr38, SrMcN and SrTmp genes and since, these genes have been used widely in genotypes resistant to Ug 99, there is a possibility of breakdown of these genes in Iran. Therefore, genetic variability of pathogen should be continuously investigated and resistance sources should be developed based on this information. For achieving this aim, 56 stem rust differential cultivars/lines obtained from the Cereal Research Center, Manitoba State, in Canada were planted in Ardabil Province, northwestern Iran under natural field conditions. The seeds of each cultivar/line were planted in two rows with 1 m of length and were irrigated every 10 days to promote disease development. Disease severity and type of infection of each cultivar/line were recorded based on the standard protocol at late flowering stage.
Results and Discussion
In the first year, the disease was developed only in Ardabil region. The SrMcN gene was the most susceptible gene, however, there was no virulence on Sr5, Sr21, Sr9e, Sr7b, Sr11, Sr6, Sr36, Sr9b, Sr30, Sr9a, Sr9d, Sr24, Sr31, Sr38, Sr8b, Sr9h, Sr12, Sr16, Sr19, Sr20, Sr22, Sr26, Sr27, Sr28, Sr32, Sr37, Sr39, Sr40, Sr41, Sr42, Sr43, Sr44, Sr45, Sr47, Sr50 ,and Sr53 genes. Other genes were moderately susceptible to virulence. In the second year, the disease was also developed. SrMcN, Sr9h, and Sr42 genes were the most susceptible genes. However, no virulence was observed on Sr24 and Sr47 genes. The genes of Sr31 and Sr36 were resistant and susceptible, respectively. It seems that Sr36 and Sr38 genes have no potential to be used in breeding for achieving resistance against stem rust disease in Iran. However, Sr24 and Sr47 genes, which were resistant in the study area, are recommended to be incorporated in breeding wheat for obtaining resistance against stem rust disease. In addition, Sr31, Sr26, Sr27, and Sr28 genes, which were relatively resistant in most areas, were found to have potential to be combined with Sr24 and Sr47 genes in wheat breeding programs.