Development of a reverse transcription-droplet digital PCR method for absolute quantification of citrus tatter leaf virus

Tatter leaf disease caused by citrus tatter leaf virus (CTLV) is a serious threat to the citrus industry. In this study, a reverse transcription-droplet digital polymerase chain reaction (RT-ddPCR) assay for detection of CTLV was established by optimizing the reaction conditions. The dynamic range of the detection of CTLV RNA transcripts by RT-ddPCR was from 5 to 5 x 10(5) copies/mu L, and the sensitivity was 10 times higher than that of RT real-time PCR. Both techniques showed a high degree of linearity and quantitative correlation. The number of positive samples that was identified in field citrus samples using RT-ddPCR (62.3%) was higher than that of RT-qPCR (49.2%). The results demonstrated that the RT-ddPCR assay is a promising tool for improving CTLV detection.