Bean is one of the most important species of leguminous family and one of the most important legumes in the world. Bean root rot caused by soil pathogenic fungus, F.solani f.sp. phaseoli, is considered one of the most important diseases of bean in the world and in Iran. It is very persistent disease in the soil and it lasts for a long time in the soil, and its control is very difficult. At the moment use of resistant cultivars is the most effective method of control. For this reason, the response of five cultivars and 14 lines of white beans were evaluated to fungus Fusarium root rot. Firstly, a morphological evaluation and then Real-time PCR quantification were performed. For morphological assessment of cultivars and lines of white beans to the disease in greenhouse conditions was evaluated by contamination of root plants. Experiment was conducted in a completely randomized design with three replicates and three observations in each replication under greenhouse conditions. The effect of infection with virulent isolate on growth factors of plant consisting foliage and root length, dried root and foliage weight, length of necrosis lesion on root, foliar disease severity and root disease severity was assayed. Based on the results the KBC42101 line and the Dorsa cultivar, they were found to be sensitive and tolerant, respectively. Then, in order to evaluate the quantitative assessment and growth trend of the pathogen, in sensitive and tolerant genotypes, the bean seedlings were inoculated by 107 suspension of relevant pathogen with Root dip method and DNA was extracted from root of inoculated and control seedlings at regular sampling intervals. The gradual increase in the amount of fungal DNA of roots was quantified by Real-time PCR technique and utilizing of SYBR Green system with specific primers for elongation factor 1-α gene. The results showed that there is a significant difference between the amount of pathogen DNA in the roots of susceptible and tolerant plants, so the Real-time PCR technique is a suitable for evaluating of bean genotypes resistance to Fusarium root rot.