<em>Grapevine fleck virus</em> (GFkV) elimination in a selected clone of <em>Vitis vinifera</em> L. cv. Manto Negro and its effects on photosynthesis

Aims: The use of healthy propagating material is required to control grapevine viruses. The aim of this work was to eliminate Grapevine fleck virus (GFkV) from a Manto Negro clone, a local grapevine variety, in order to include this material in certification programs. Additionally, the effects of virus elimination on photosynthesis and related parameters were evaluated. Methods and results: Two method combinations for virus elimination were evaluated: (1) field thermotherapy and shoot tip culture and (2) chamber thermotherapy and shoot tip culture. GFkV elimination was tested by double antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). The results suggest that a natural field thermotherapy prior to shoot tip culture is effective, making unnecessary the chamber thermotherapy treatment. Additionally, the effects of virus elimination on gas exchanges, chlorophyll fluorescence, electron transport rate (ETR), protein and pigment content were evaluated. The results indicate that GFkV infection affects physiological processes, especially stomatal conductance (gs), whereas photosynthesis, protein, pigment content, ETR, and fluorescence parameters were not significantly changed.  Conclusion: This study described a simple and rapid method that requires only one medium for virus elimination (GFkV). Beyond its sanitation potential, the use of larger explants (1-3 mm) ensures the integrity of the clone. The presence of the virus affects physiological processes, especially gs, demonstrating the beneficial effect of eliminating GFkV. Significance and impact of the study: The described method has the potential to produce GFkV-free rooted plantlets faster than other methods while being potentially safer in maintaining the genetic and phenotypic stability of the regenerated clone. The beneficial effects of GFkV elimination provide evidence for the importance to detect this virus prior to the inclusion of clones in certification programs.