WINETECH Technical Yearbook 2020

Grapevine rupestris stem pitting-associated virus (GRSPaV) is the most prevalent virus in vineyards and well characterised molecularly, but still relatively unknown. Vast amounts of virus genome sequence data were accumulated recently for viruses infecting grapevines and this trend continues. The reason for this rapid accumulation of data is that the molecular analysis of virus populations in plants DARIUSZ GOSZCZYNSKI: Plant Health and Protection, Agricultural Research Council, Pretoria KEYWORDS: Grapevine rupestris stem pitting-associated virus, GRSPaV Grapevine rupestris stem pitting- associated virus JANUARY/FEBRUARY 2020

PHOTO 1. Severe RSPD symptoms in Vitis rupestris cv. St. George. GRSPaV status is unknown. (Courtesy of Tobie Oosthuizen, Vititec.)

differs between various countries: Very high (90.4%) of tested grapevines in Australia, relatively very low in countries like South Africa (14.4%), or, as in Iran, the virus is not present at all (Habili, 2015). However, these rather surprising data need careful investigation. As no insect vector was identified, it is believed that the wide presence of the virus in V. vinifera vineyards is the result of the worldwide exchange of GRSPaV-infected grapevines and transmission of this virus by grafting. All tested Iranian samples were collected from native grape cultivars that were growing from their own roots. The very

disappointed. The industry needs solid information on how harmful these viruses are to grapevines. Sometimes this information is lacking and is difficult to obtain. The classical example is grapevine rupestris stem pitting-associated virus (GRSPaV). The discovery of the virus was reported in 1998 (Meng & Rowhani, 2017). Soon investigations revealed that GRSPaV is the most widely spread virus in Vitis vinifera vineyards worldwide. Recorded infections amount to 100% of tested grapevines (Xiao et al ., 2018). Data from Waite Diagnostics, Australia, suggest that the incidence of the virus

is relatively easy. It is just a matter of purifying nucleic acids, amplifying the genome of viruses, sequencing and computer-assisted analysis of obtained sequences. This has led to the development of molecular methods, such as High- Throughput Sequencing (HTS), that precisely evaluate the virus status of investigated grapevines. Although this is a great achievement from a scientific perspective, the application of these techniques, and revealing that virus infections of grapevines are common in vineyards, cause the average grapevine farmer to become confused and somewhat

WINETECH TECHNICAL YEARBOOK 2020 7