Virulence Factors Of Stem Rust And Responses Of Some Advanced Wheat Genotypes To Isolates Of The Pathogen At Seedling Stage

To determine virulence factors in the population of stem rust, several wheat leaf samples infected with Puccinia graminis f.sp. tritici were collected from different areas of Iran during 1996-1997. After purification and spore multiplication, Avirulence/Virulence formula of each isolate was determined in the greenhouse by inoculating them on 44 stem rust near isogenic lines. In another experiment, 20 wheat genotypes were also inoculated by spores of different isolates to evaluate their resistance to each isolate. Twenty different pathotypes were identified in the present study. All isolates were virulent on genes Sr9a, 9d, 9g, 11, 12, 14, 17, 19, 20, 21, 34, while gene Sr27 was resistant to all isolates. Isolate collected from Khorramabad, being virulent on 37 genes, and two isolates from Ahwaz and Busher, being virulent on 22 genes, were the most and the least aggressive isolates, respectively. Wheat genotypes, were classified into 3 groups based on their infection types. Group 1, including Atrak, Attila, Vee/Nac, N-75-2, N-75-4, S-75-14, S-75-19, S-75-4, S-75-16. S-75-2 and S-75-5 were resistant to all or majority of the isolates, group2, including lines N-75-3 , S-75-3 and Bolani (susceptible cheek) were susceptible to all or majority of the isolates, and group 3 which had different infection types to different isolates.