A modified green-grafting technique for large-scale virus indexing of grapevine (Vitis vinifera L.)

A modified method of green-grafting was investigated for use in viral indexing of grapevine stock. Cabernet franc and Cabernet sauvignon scions infected with grapevine leafroll-associated virus 3 (GLRaV3) were cleft-grafted on to virus-free indicator rootstocks LN33 and C. sauvignon, and were maintained in polystyrene containers containing vermiculite soaked with Huglin and Julliard solution. Using this method plants could be transferred to soil 3–4 weeks following grafting. Leafroll symptoms: reddening of leaves, leaf rolling, and interveinal discolouration, were scored at 3–4 weeks and again at 12 weeks. Double antibody sandwich–enzyme linked immunosorbent assay (DAS–ELISA) was used to validate the visual symptoms of disease. At both times it was clear that C. sauvignon was a more sensitive indicator of GLRaV3 than LN33, with 80% of grafts showing symptoms at 3–4 weeks and 90% showing symptoms at 12 weeks. The results indicate that the technique described here is effective and suitable for large-scale indexing of grapevine stock for viral contamination.