Objectives: Avian reoviruses (ARVs) are important causes of disease conditions in poultry, in particular, reovirus-induced arthritis, tenosynovitis. Materials & Methods: In this study, avian reoviruses causing tenosynovitis in breeder flocks of Iran was investigated by RT-PCR, (RFLP) and molecular characterization of the virus isolates. Extracted RNA from 800 fecal swab samples then were used in RT-PCR to amplify the selected parts of S1 (1023 bp) genes from ARV field isolates. The RT-PCR amplified products of positive samples were further analyzed by RFLP using five restriction enzymes of BcnΙ, DdeΙ, HaeΙΙΙ, HincΙΙ, and TaqΙ. Sequence analysis of the S1 genes of ARVs isolated. Results & Conclusion: The result of this study revealed that positive samples were closely related to the most ARVs inducing tenosynovitis with less than 2% nucleotide divergence. The homology was highest with the strain S1133, this strain is commonly strain that induced tenosynovitis and used in live and killed vaccine and this new strain had a 99/9 % nucleotide and amino acid identity.
