Abstract: To assess the variation and evolution of S1 gene of the prevailing Infectious Bronchitis Virus(IBV) strains. 17 IBV isolates were identified from several Provinces including Shandong,Sichuan et al in China during 1992-2008,wherein the S1 genes were sequenced. Phylogenetic analysis and HVR I of these IBV isolates were compared and analyzed,together with the IBV reference strains published in GenBank. 58 IBV strains were divided into six genotypes on account of different times,areas and clinical pathologies. There were at least five genotypes in China up to now. In detail,genotype Ⅴand Ⅳ were the most important prevailing IBV genotypes in China recently. Genotype Ⅴ included most isolates from North area during 1992-2008,while the genotype Ⅳ were mainly isolated from South area during 2000-2008. Two kinds IBV strains were intercrossed mutually and displayed different epidemical forms,which would be a serious problem due to poultry transport. Importantly,the amino acid substitutions,insertions were also found in HVR I of these IBV isolates. Alignment analysis of the S1 nucleotide and deduced amino acids sequences showed that there were amounts of variations among circulating IBV strains,which indicated that the evolutions of IBV S1 genes were diverse. Nonetheless,there were good relationships among different segments of IBV strains (r = 0. 968) ,which could help us to have a better understanding to IBV. Furthermore,the distinctions among the prevailing strains and vaccine became more and more evident,which implied that there would be great variations in IBV isolates under the immune pressure due to the continuing H120 vaccination.

Key words: Infectious bronchitis virus, Genetic variation, S1 gene, Genotype

CLC Number: 

• Q8