Development of a one-step RT-qPCR assay for the detection of Grapevine leafroll-associated virus 7

Grapevine leafroll disease (GLD) is one of the most economically important viral diseases of grapevines. GLD is caused by a complex of several ssRNA (+) viruses referred to as Grapevine leafroll-associated viruses (GLRaVs). To date, five different GLRaV species have been identified. One of those species, GLRaV-7, was first reported from a symptomless white-fruited wine grape cultivar from Albania. Since its discovery, GLRaV-7 has been reported from 14 countries. Although serological assays have been developed to detect GLRaV-7, commercially available antibodies produce high background signals making them unsuitable for regulatory testing. Furthermore, while molecular detection assays have been shown to be more sensitive when compared to the serological assays, published molecular assays, except the one Reverse Transcription-quantitaive Polymerase Chain Reaction (RT-qPCR) assay based on heat shock protein 70 homologue (HSP70h) gene, have been reported to be inadequate in detecting all reported isolates of GLRaV-7. Availability of multiple assays provides flexibility to diagnostic laboratories in cases where the chosen assay fails to detect a strain or an isolate of a pathogen due to variation in its targeted region or where additional confirmation of the results is required. In this study, we developed a sensitive and specific RT-qPCR assay, based on a region of p61 gene of GLRaV-7, which detected all available isolates.