Suresh, P.rajeswar, J. JohnsonSukumar, K.Harikrishnan, T.J.Srinivasan, P.TANUVAS2017-12-182017-12-182015-11http://krishikosh.egranth.ac.in/handle/1/5810037726TNV_KVSC_Y2015_14-15Nov_Pg426-436A study was undertaken to characterize the oncogene and oncogenecity associated genes at molecular level for three serotype 1 Marek’s Disease Virus (MDV) field isolates isolated from vaccinat- ed poultry flocks which had encountered the l\/Iarek’s Disease (MD) outbreak in Tamil Nadu and Kar- nataka. The isolates were named as Ind/TN/11/01, Ind/KA/12/02 and Ind/ TN/ 12/03. The oncogen- eMegand oncogenecity associated genes like pp38 and V[L8were amplified by PCR and sequenced. Amplified product size was 1081 bp, 1006 bp and 887 bp for Meg, pp38 and VIL8 genes respectively. The isolates were shown to have a homology of 99.1-99.8, 97.3-98.3 and 94.6-95.1 per cent with vari- ous isolates of China for Meg, pp38, and I/[L8 genes respectively and 98.5 - 99.2, 98.4 - 100 and 96.6 - 99.5 per cent with isolates of Europe and USA for Meg, pp38 and I/[L8 genes respectively. Alignment analysis of the nucleotide sequences showed that nucleotide mutations at five different positions in Meg gene, two different positions in pp38 gene and three different positions in I/[L8 gene displayed perfect regularity in MDVs circulating in southern part of India, which could be considered as features of field MDVs prevalent in this area recently. In addition, the mutation in Meg gene at positions 251, 260 and 437 were unique and coincides with very virulent strains from China GX0101, GXY2 and a Hungarian strain ATE. The mutation at positions 283 and 300 were unique and coincides only with very virulent strain ATE of Hungary There isalso a single nucleotide mutation at positions 155 (A to T), 369 (A to C), 462 (C to A) and 548 (C to T) observed in the isolate Ind/TN/ 12/03. The nucleotide mutation in pp38 gene displayed regularity at two positions, including 477 and 640 and the I/[L8 gene displayed regularity at three positions, including 112 (T to C), 329 (T to C) and 368 (A to G) in en- tire field MDV isolates of this study. Phylogenetic analysis of Meg, pp38 and I/[L8 protein sequences revealed that field MDVs in this area evolved independently but have similarities with very virulent strains of China and primary oncogene Meghas got more similarities with very virulent Hungarian strain.enVeterinary ScienceArticle