reaction of some wheat cultivars to bipolaris sorokiniana the causal agent of common root rot

abstract common root rot induced by bipolaris sorokiniana, is one of the most important diseases of wheat. chemical control of this disease is difficult because of it is a soil-born pathogen, so that, application of other methods is useful to reduce disease level especially resistance cultivars. in this research, were examined reaction of some wheat cultivars and lines against common root rot in greenhouse condition, at summer of 1384. nine isolates of the fungus were isolated from infected wheat fields in markazi province and their pathogenicity was examined on wheat. the pathogenicity of two isolates (kh and sh) were more than others, so they were selected and used to compare reaction of fifteen wheat cultivars and lines. the plants were harvested at two times of 4 & 7 weeks after planting. the study was planned in a factorial arrangement in the basis of completely randomized design with 4 replications per treatment. the parameters of patterns were measured were including: 1) dry weight of aerial part and root, 2) percentage of infection at subcrown internodes. the results were analyzed whit sas & mstatc. the results showed: that sh isolate had more pathogenicity rather than kh isolate and there is significant difference between disease reactions among cultivars. the cultivars sabalan, zarrin and niknejad were most resistance in comparison to other cultivars to common root rot. the maroon, bakkras-roshan and kavir were more susceptible cultivars. the pishtaz, alvand, gaspard, alamoot, darab2, marvdasht cultivars, c-78-14 and m-79-6 lines were graded between these two groups.