Simultaneous detection of all possible combinations among SPLCV, SPFMV, SPVG, and SPLV by multiplex RT-PCR. Lane M: 100 bp ladder; Lane 1: SPLV; Lane 2: SPVG; Lane 3: SPFMV; Lane 4: SPLCV; Lane 5: SPLV and SPVG; Lane 6: SPLV and SPFMV; Lane 7: SPLV and SPLCV; Lane 8: SPVG and SPFMV; Lane 9: SPVG and SPLCV; Lane 10: SPFMV and SPLCV; Lane 11: SPLV, SPVG, and SPFMV; Lane 12: SPLV, SPVG, and SPLCV; Lane 13: SPLV, SPFMV, and SPLCV; Lane 14: SPVG, SPFMV, and SPLCV; Lane 15: SPLV, SPVG, SPFMV, and SPLCV.