Seasonal dynamics and spatial distribution of main Grapevine viruses in field-grown grapevine cultivars

Propagation of uninfected plant material is one of the most effective ways for controlling grapevine disease. Different diagnostic methods are available for testing viral infections, including serological techniques such as enzyme-linked immunosorbent assay (ELISA) and molecular techniques based on reverse transcription polymerase chain reaction (RT-PCR) and reverse transcription quantitative PCR (RT-qPCR). The objective of this study was to examine seasonal dynamics and spatial distribution of grapevine viruses within field-grown grapevine cultivars, in order to make more efficient virus detection by ELISA and RT-PCR, by identifying and selecting proper plant material and sampling time. For this purpose, a systematic investigation, considering different plant tissues and phenological stages, has been carried out through a multi-year study. Eight grapevine plants with single or multiple viral infections were selected and their state of infection was firstly monitored during the 2007 growing season, followed by a final infection assessment occurred after 5 years. Our results confirmed a strong erratic distribution of viruses within the vines, regardless of sampling stages, tissue type and/or different plant parts. For what concerns seasonal dynamics, our results on long-term infected grapevine plants corroborated the hypothesis that viruses behave differently from each other with respect to their irregular or rather homogeneous spatial distribution. Thus, an accurate sanitary status check of any grapevine must provide several random samples from different plant parts that have to be carried out several times both during a single growing season and through the years, removing infected vines, and taking vector populations under control.