Determine the transmission dynamics of plants infected with mixed GLRaV-3 variants
Jooste, A E C
ARC Plant Protection Research Institute
Jooste, A E C
Maree, H J
Previously, an extensive survey revealed the dominant occurrence of GLRaV-3 variants II and VI in South African vineyards. Further investigations, that included variant-vector interactions, followed. In this study the transmission dynamics of mixed variant infections in selected source plants were determined. The overall objective of the project was to assist in identifying any biological and transmission differences among the various variants of GLRaV-3. A transmission experiment using Planococcus ficus was carried out using source plants that were infected with seven different combinations of GLRaV-3 variants. The selected plants were co-infected with other grapevine-infecting viruses. A RT-PCR HRM analysis was done to determine the transmission efficiency of individual GLRaV-3 variants from the mixed variant infections in source plants. Detection of the presence of other grapevine infecting viruses, i.e. Grapevine virus A (GVA), Grapevine virus B (GVB) and Grapevine rupestris stem pitting virus (GRSPaV), was carried out using virus-specific primers. The study demonstrated that GLRaV-3 variants from groups I and II established better in recipient plants during transmission either as single transmission or in combination with each other. The exact interaction between variants in a plant is still unknown but it is clear that competition between variants exists, either in the mealybug vector or in the recipient plant after transmission. GVA was transmitted in higher frequencies than GVE. The interaction between GVA and the group II variant needs to be investigated in more detail.
Impact on industry:
Not all grapevine farmers have the financial means to remove and replace infected plants or blocks and therefore the problem of leafroll will continue to pose a serious economic problem in certain grape-producing regions. This study aimed to support the management strategies of the industry through gaining knowledge of GLRaV-3 variants and their transmission that will help to solve future management problems, for instance when resistance breeding may be considered in future.
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