3.4. Evaluation of multiplex RT-PCR3.4.1. Efficiency of multiplex RT-PCR for the detection of pearvirusesTo validate the reliability of the optimized mRT-PCR, pear sam-ples infected by the three target viruses were tested by mRT-PCRusing different primer combination (Fig. 4). The mRT-PCR resultsFig confirmed that the mRT-PCR could amplify all possible combina-tions of three pear viruses and was effective for the simultaneousdetection of three viruses. Meanwhile, the detection efficiency ofuRT-PCR and mRT-PCR was compared by testing three viruses in36 pear samples collected randomly from different fields. The tar-get viruses were detected in 25 out of the 36 samples (69.4%)as indicated by the detection results of both uRT-PCR and mRT-PCR (Table 2). ASGV and ASPV were detected in 19 (52.8%) and21 (58.3%) samples by uRT-PCR, and in 18 (50%) and 21 (58.3%)samples by mRT-PCR, respectively. Four and three samples werepositive for ACLSV as detected by uRT-PCR and mRT-PCR, respec-tively. The co-efficiency rates between uRT-PCR and mRT-PCR forthe detection of ASGV, ASPV and ACLSV were up to 97.2%, 100% and97.2%, respectively. The result indicated that uRT-PCR and mRT-PCR had good agreement for the detection of those three viruses.Mixed infections were common, and 17 out of 25 positive sampleswere infected with ASGV and ASPV, two were infected with all threeviruses as that revealed by uRT-PCR.