Comparison of low-density arrays, RT-PCR and real-time TaqMan RT-PCR in detection of grapevine viruses.

Low-density arrays (LDA) have been designed based on the real-time RT-PCR (TaqMan) assays for the specific detection of 13 viruses that infect Grapevines in addition to the housekeeping gene 18S rRNA. The viruses included in the study are Grapevine leafroll associated viruses 1, 2, 3, 4, 5, and 9, Grapevine leafroll associated virus-2 Redglobe (GLRaV-2RG) strain, Ruspestris stem pitting associated virus, Grapevine vitivirus A, Grapevine vitivirus B, Grapevine fanleaf virus, Tomato ringspot virus (ToRSV), and Grapevine fleck virus (GFkV). This study includes three new TaqMan RT-PCR assays that have been developed for GLRaV-2RG, GFkV and ToRSV and have been included in the TaqMan RT-PCR and LDA detection. The LDAs were evaluated against a wide range of isolates distributed geographically. Geographical locations included Africa, Europe, Australia, Asia, Latin America and the United States. High-throughput detection of these viruses using LDAs was compared to RT-PCR and real-time TaqMan RT-PCR. The efficiency of different RNA extraction methodologies and buffers were compared for use in low-density array detection. In addition improving the RNA extraction technique and testing the quality of the RNA using the 18S ribosomal RNA TaqMan assay as an RNA specific internal control proved to generate better diagnostic assays. This is the first report on the use of LDA for the detection of plant viruses.