Development of Duplex-Immunocapture (Duplex-IC) RT-PCR for the Detection of Sugarcane streak mosaic virus and Sugarcane mosaic virus in Sugarcane

Mosaic a major disease of sugarcane caused either by Sugarcane streak mosaic virus (SCSMV) or Sugarcane mosaic virus (SCMV) either alone or in combination. Though many serological techniques are available for the detection of viruses, molecular methods are found to be more sensitive in case of low virus titre. For the conventional molecular assays in reverse transcriptase (RT)-PCR, RNA extraction from sugarcane leaves is a cumbersome process. Hence, we optimized immunocapture (IC) using recombinant antiserum (r-antiserum) developed against SCSMV-coat protein (CP) to trap the virus before reverse transcription and optimized a duplex immunocapture reverse transcription (IC-RT) PCR assay. Subsequently we found that the r-antiserum is found to be sensitive to detect both SCMV and SCSMV. Our study established that r-antiserum developed against SCSMV-CP, trapped both SCSMV and SCMV in IC-RT-PCR and it was sensitive enough to detect the two viruses causing mosaic. In ELISA, 12 of 18 sugarcane samples exhibiting varying mosaic symptoms were found to be negative to the virus(es), however they were positive in IC-RT-PCR. We conclude that although DAC-ELISA is simple and cost effective to diagnose these viruses, in samples with very low virus titre, IC-RT-PCR would be more sensitive. This is the first report on the detection of SCSMV and SCMV together in an IC-RT-PCR assay.