Development and application of a universal and simplified multiplex RT-PCR assay to detect five potato viruses

Potato virus X (PVX), Potato virus Y (PVY), Potato leafroll virus (PLRV), Potato virus M (PVM), and Potato virus A (PVA) commonly cause mixed infections and major economic losses in potato crops, so a multiplex reverse transcription polymerase chain reaction (RT-PCR) assay has been greatly needed to detect all five viruses simultaneously. Previously published primers were evaluated, and five pairs of highly specific primers were selected for use. The quintuplex RT-PCR assay was optimized for primer concentration, annealing temperature, number of PCR cycles, and extension time. Finally, the quintuplex RT-PCR assay was successfully established. The amplified target fragments of 711 base pairs (bp) for PVX, 447 bp for PVY, 336 bp for PLRV, 520 bp for PVM and 273 bp for PVA, and the viral origins of the PCR products were confirmed by sequencing. This system can be easily customized for simplex, duplex, triplex, tetraplex, and quintuplex RT-PCRs by changing only the primer pairs while keeping the final reaction volume and the concentrations of other reagents constant to detect any combination of PVX, PVY, PLRV, PVM, and PVA viruses. In this way, the detection systems can be customized to the characteristics of viral infections specific to China’s potato-producing regions for excellent detection efficiency and meeting the needs of potato producers. The detection limit of this assay was up to 10−3 dilution in tetraplex and quintuplex RT-PCR, and even higher in simplex, duplex, and triplex RT-PCR. The efficiency of the quintuplex RT-PCR was compared with that of a DAS-enzyme-linked immunosorbent assay to detect the five viruses in 320 field potato samples, 195 in vitro plantlets and pooled potato samples. This new multiplex RT-PCR method is not only effective but also faster, cheaper, more sensitive, and more reliable than DAS-ELISA. It is especially suitable for the testing of in vitro plantlets and pooled samples of postharvest seed tubers.