عنوان مقاله [English]
Plants showing root and crown rot were collected from 48 bean fields in the Khuzestan and Markazi provinces During 2005-2006. Using specific primers (FsphR/FsphF) for these forma specialis, three isolates were identified as F.s. f.sp. phaseoli. Conidial suspension of one of these isolates were irradiated (in a 60Co- gamma cell with activity of 2500 curi and 0.38 grey per second dose rates) with 130 Gy. Pathogenicity and root colonization tests confirmed two avirulent mutants. Molecular comparison using 10 primers between avirulent mutants and wild type showed that, avirulent mutants M22 and M23 have 73% and 50% similarity with wild type kh12. These results showed that, avirulent mutants were produced due to genetical differences. This is the first step to induce mutation and screening for avirulent mutants which are promising prerequisite for biological control of this important disease in bean.