PCRSensitivities of uniplex RT-PCR and mRT-PCR for the detectionof three pear viruses were determined by using 10-fold serial dilu-tions of cDNAs generated from total RNA extracted from in vitrocultured pear plants infected by all three target viruses and plas-mids containing CP genes of three viruses, respectively. When theplasmids were used as templates (Fig. 3B), the detection limits ofthe uniplex RT-PCR assays were 10−4for all three viruses, and themRT-PCR assay raised the same detection limit of 10−4for ASPV andACLSV and a slightly lower limit of 10−3for ASGV. When the cDNAswere used as templates (Fig. 3A), the detection limits of the uniplexRT-PCR assays were 10−2for ASPV and ACLSV, respectively, and thedetection limit for ASGV was 10−1(Fig. 3A, a). All three viruses werewell detected at dilution of 10−1(equivalent to 100 g of plant tis-sue), and their detection limit was at dilution of 10−2in mRT-PCR.Those results indicated that the sensitivity of the mRT-PCR assayfor the three viruses was similar to that of the uniplex assays andsuitable for the simultaneous detection of those three viruses.