2.5. Evaluation of multiplex RT-PCRThis optimized mRT-PCR was compared with each of the uniplexRT-PCR assays to determine its sensitivity for the detection of eachtarget virus using a series of 10-fold dilutions of the cDNAs gener-ated from total RNA of virus infected pear plants and of plasmidscontaining virus-specific inserts.The reliability of the optimized mRT-PCR was firstly validatedby using different primer combinations and three pear samplesinfected with three target viruses (Table 1). The assay was fur-ther evaluated using 36 field samples collected from three differentregions in China. Finally, the mRT-PCR was adapted to virus detec-tions in young leaves and dormant budwoods of pear and appleplants.