Beet black scorch virus (BBSV) infection has been reported from several sugar beet production regions of Iran. There is little data about biological properties of Iranian BBSV isolates particularly regarding their role in inducing of root beard (root madness), very similar to the symptoms caused by Beet necrotic yellow vein virus (BNYVV) in Rhizomania disease. In our previous observations, BNYVV was not detected in some sugar beet samples showing rhizomania like root symptoms (root beard), whereas, they showed BBSV infection. In this study, a total of 267 sugar beet samples (each plant with its surrounding root soil) were collected from Azarbaijan-e-Gharbei, Isfahan, Khorasan-e-Razavei, Kermanshah and Fars provinces and tested for BNYVV and BBSV using ELISA method. Results showed infections of BNYVV (41.9%), BBSV (20.9%), and BNYVV+BBSV (15.4%). According to the results, four soil treatments including BNYVV infected, BBSV infected, BNYVV+BBSV infected soil, and soil without BNYVV and BBSV (negative control) were prepared using soil samples. Sugar beet cv. Jolgeh, a susceptible cultivar to BNYVV infection, were sown in the soil treatments and they were evaluated for inducing of root madness (beard) symptoms based on a completely randomized design (CRD) experiment with four replications in greenhouse condition. Root bearding (rhizomania) symptoms severity was evaluated using a score of 0 to 9 scale (0: without symptoms and 9: severe bearding with root necrosis and plant death) and data was statically analyzed. Root bearding symptom severity was determined as 87.2, 80.6, 39.4 and 0.0 percent for BNYVV+BBSV, BNYVV, BBSV, and negative control, respectively. These results revealed that Iranian BBSV isolates alone are able to induce root bearding symptoms in the tested sugar beet cultivar.