Technical Yearbook 2023

FIGURE 7. European and Mediterranean Plant Protection Organisation (EPPO) map of the worldwide distribution of grapevine pinot gris virus (updated 2022-09). Yellow dots represent reported occurrence within the country.

from GPGV-affected countries. It is now reported from various European countries, South Korea, Eastern Europe, China, Chile, USA, Canada, Uruguay, Brazil, Pakistan, and Australia (figure 7). No tests have previously been conducted to determine whether GPGV occurs in South Africa but its vector, an eriophyid mite, is reported here. As it has not been reported from here, it is considered an exotic virus to South Africa. To add it to the list of phytosanitary requirements for the import of grape material into South Africa, it is important to confirm its absence in South Africa. We did this by analysing 229 accessions of Vitis housed at the Vitis germplasm vineyard in Nietvoorbij using the next-generation sequencing (NGS) technique. We also tested 50 accessions of Vitis planting material imported into South Africa during the last 10 years, provided by three plant improvement organisations (PIOs). GPGV was not observed in any of the 229 long established Vitis accessions housed in the Vitis germplasm collection, but was confirmed to occur in four of the 50 accessions recently imported into South Africa. The presence of this virus allowed us to attempt to optimise the GPGV polymerase chain reaction (PCR) test for this virus after the commercially available ELISA kit was found to perform sub-optimally. All vines derived from the confirmed GPGV-infected accessions were destroyed by the relevant PIOs and we still consider the South African grape industries (wine, table and raisin) to be free of this virus. As it is not possible to test all the grapevine planting

material imported into South Africa retroactively, we invite any grower who observes symptoms as illustrated by figure 6, to inform us as quickly as possible of this, as speed would be of the essence to prevent further spread. The phytosanitary authorities at Department of Agriculture, Land Reform and Rural Development (DALRRD) have been requested to consider the addition of GPGV to the list of exotic viruses which imported Vitis planting material must test free of, or be accompanied by a phytosanitary certificate from the exporting country declaring the material free of GPGV. Conclusion These two projects, funded by Winetech, have provided material outcomes toward improved control of viruses of grapevines in South Africa. In the first instance it has provided a validated protocol for the detection, and hence control, of grapevine fleck virus within the Vine Improvement Association grape certification scheme. Furthermore, the absence of grapevine pinot gris virus, the cause of an important emerging disease of grapevines in well-established South African Vitis stocks was demonstrated. In addition, the virus was intercepted and this prevented introduction into the South African grape industry of the virus by four instances of newly imported Vitis material.  Reference https://www.wineland.co.za/winetech-funds-research towards-improved-vitis-planting-material/

For more information, contact Gerhard Pietersen at gerhard@pathsol.co.za.

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TECHNICAL YEARBOOK 2023