South Africa Wine Research Projects

2. VITICULTURE RESEARCH COMPLETED PROJECT

DETECTION AND IDENTIFICATION OF VIRUSES IN NUCLEAR MATERIAL

GenUS GP 20-01 Prof Gerhard Pietersen, Patho Solutions Project completed: 2023

AIM AND INDUSTRY RELEVANCE: Certification schemes worldwide are used to prevent the spread of pathogens via planting material. This is achieved by starting with material of impeccable phytosanitary status, from which thou sands of progeny plants are derived. In the one-Vitis certification scheme of South Africa, only a few viruses, amongst the many known to infect grapevines globally, are tested for in nuclear material. It is unknown whether any of these viruses are present in nuclear plant material and in what incidence they occur. This project aimed to determine whether nuclear material used within the South African table and wine grape industries is free of viruses and viroids and, if not, to identify viruses still present in such material as a first step towards eliminating or managing them in accordance with the fundamental objectives of a certification scheme. South African vine nuclear material appears remarkably free of grapevine viruses despite only a few of the more than 80 known viruses being tested for locally. This is probably due to the man datory application of heat therapy and meristem tip culture to create nuclear plants. All remaining and future nuclear plants should be subjected to NGS analysis to confirm their virus/viroid status. Those found to be virus-infected must be subjected to secondary virus elimination processes. The common presence of viroids suggests that these agents are not eliminated by current elimination processes or spread exceptionally rapidly within the nuclear block facilities. A risk assessment of the importance of these agents must be made before deciding to eliminate these pathogens from nuclear material and whether to manage these agents.

SOUTH AFRICA WINE RESEARCH 2024

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