Dr. Surya SankarSRUTHY CHANDRAN B.2024-03-262024-03-262022-03-08https://krishikosh.egranth.ac.in/handle/1/5810207714Infectious bronchitis virus (IBV) is the aetiological agent of infectious bronchitis (IB), an acute and contagious disease with high economic significance in the global poultry industry. Circulation of diverse variants of IBV make the control of the disease difficult, despite extensive vaccination programmes. In Kerala, vaccination against the disease is not strictly followed and the occurrence has been proved in earlier studies. In this scenario, the present study is contemplated on genotypic characterisation of IBV isolates across the state, focusing on the sequencing of whole S1 subunit of S gene, N and M genes followed by restriction fragment length polymorphism (RFLP) on representative amplicons of S1 subunit of S gene. Out of the 103 samples collected, 32 were found to be positive for the disease with detection primers that targeted the hypervariable region 3 of S1 subunit of S gene. The tissue homogenate from positive samples were inoculated in 9-11 day-old embryonated chicken eggs via., allantoic route. Allantoic fluid was harvested after 48 h and reverse transcriptase polymerase chain reaction (RT-PCR) with the same detection primers was done to confirm the presence of the virus. All the 32 samples were positive for RT-PCR targeting S1 subunit of S gene, N and M genes. The representative amplicons of the above mentioned genes were sequenced, analysed and compared with current vaccine strain H120 and sequences of other Indian IBV isolates available in the GenBank. On nucleotide sequence and amino acid profile analysis, it was found that variations exist among isolates as well as with vaccine strain and other Indian isolates. On phylogenetic analysis based on these genes, the isolates clustered with each other and also with isolates from different parts of India. The representative amplicons of S1 subunit of S gene when subjected to RFLP, generated restriction patterns similar to the vaccine strain, Massachusetts type.EnglishThesis