OBJECTIVETo classify the Chinese isolates of Coltiviruses.

METHODSThree sets of primers were selected among them two were specific to the 9th and 12th segments of subgroup B2, and one was for the 12th segment of subgroup B1-All the Chinese isolates of Coltivirus selected in the experiment were classified according to the lengths of different amplicons of the reverse transcriptase-polymerase Chain reaction (RT-PCR). The homogenicity of the nucleic acids of the isolates BJ95-75 and YN-6 was also compared with other Coltivirus strains belonging to subgroup B2.

RESULTSWith the primers 12-854-S/12-B2-R, which were specific to the 12th segment of Coltivirus subgroup B2-850 bp amplicons were obtained from Beijing isolate BJ95-75 and all the Yunnan isolates such as YN-6, -67-1, -68-1, -69, -70-1, -70-2, -90, -92-2, -93 of Coltivirus 492 bp DNA fragments were also amplified from all of them with the segment 9th specific primers 9-JKT-S/9-JKT-R. However no positive results were obtained from Northeast isolates NE97-12, NE97-31 and control viruses YN-99(Orbivirus),YN-151-1(JEV) with the same two sets of primers. With 12-B1-S/12-B1R primers specific to the 12th segment of subgroup B1, no amplicons of right length were obtained from any of the Chinese isolates of Coltivirus and the control viruses. When compared the nucleic acid sequences of BJ95-75 and YN-6 with other Coltivirus strains such as Bannavirus, JKT6423, JKT6969, JKT7043, the amplicons from segment 12th of these two strains had more than 89.4% homology with the other strains, especially to the earlier Chinese isolate Bannavirus, the homolog was more then 98.9%. Nearly 96.5% and 99.2% of the nucleic acids of the amplicons from segment 9th of the two strains were being homologous to Bannavirus and about 84.0% to JKT6423, which had been classified into type B2a. But the maximal homogenicity was about 53% when compared with the other two coltivirus strains. JKT6969 and JKT7043 which had been classified into type B2b.

CONCLUSIONGenotyping the recent Chinese isolates of coltivirus for the first time in our country. Most of the Chinese isolates belong to subgroup B2, more exactly type B2a. The Northeast isolates NE97-12 and NE97-31 were not correctly grouped with the available primers.