PCRIn mRT-PCR tests, primer pairs ASGV-U/ASGV-2and ASPV247-F/ASPV247-R were combined with eachof the three primer pairs specific for ACLSV in sepa-rated assays. Results showed that primer combinationASGV-U/ASGV-2+ACLSV-52/ACLSV-53+ASPV247-F/ASPV247-R(Table 1) gave more clear and specific bands of target products asit was compared to two other combinations, and then the primercombination was selected for further mRT-PCR tests. Meanwhile,different amplification efficiencies as indicated by different bandintensities were obtained when equal concentrations (0.08 M)of the three primer pairs were used in mRT-PCR (Fig. 1, Lane 1).To optimize the multiplex PCR system, combinations of differentconcentrations of three primer pairs were tested in mRT-PCR byusing the mixture of equal amounts of plasmids containing the cpgenes of three viruses. The results showed that the amplificationefficiencies of ASPV and ACLSV varied at different combinationsof primer concentrations and that of ASGV remained reliable. Abalanced amplification, with a similar fluorescence intensity of thebands corresponding to the three expected cDNAs, was achievedwhen the primer concentrations at 0.08 M for ASGV, 0.24 M forASPV and 0.16 M for ACLSV were used in the mRT-PCR (Fig. 1,Lane 5).