Raheleh Majdani - Institute of Bioscience and Biotechnology, Urmia University, Urmia, Iran
Karim Mardani - Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
Ahmad Morshedi - Department of Microbiology, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
Mehdi Vasfi Marandi - Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
Alireza Talebi - Department of Clinical Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran

Rapid detection and differentiation of infectious bronchitis virus (IBV) involved in the disease outbreak is very important for controlling disease and developing new vaccines. In the present study, three regions of the genome of IBV vaccine and field isolates including S۱ gene, gene ۳ and nucleocapsid (N) gene along with ۳' untranslated region (۳' UTR) were amplified and subjected to restriction fragment length polymorphism (RFLP) using three different endonucleases. Amplicons from S۱ gene and N-۳’UTR generated four RFLP patterns, grouping IBV strains into four similar groups, while amplicons of gene ۳ generated three RFLP patterns classifying examined IBVs in different groups from those of S۱ and N-۳' UTR. ۴/۹۱ strain and MNS-۷۸۶۲-۱field isolate both belong to ۷۹۳/B serotype were differentiated from each other based on gene ۳, N-۳’UTR and S۱gene. IBVs belonged to different serotypes showed different RFLP patterns based on RFLP patterns of all three regions. S۱ gene and N-۳’UTR RFLP analysis differentiated IB۸۸, MNS-۷۸۶۲-۱ and ۴/۹۱ from each other. This is the first report on the molecular analysis of the gene ۳ for IBV strain differentiation. Our results revealed that RFLP analysis of N-۳’UTR and S۱ gene had the higher discriminatory power than gene ۳. None of the RFLP patterns of different regions differentiated ۴/۹۱ vaccine strain from its field isolate.

Infectious bronchitis virus, RT-PCR, RFLP, Gene ۳, N gene, ۳’UTR