Engelbrecht, D.J., & Kasdorf, G.G.F. 1984 Association of a closterovirus with grapevines indexing positive for grapevine leafroll disease and evidence for its natural spread in grapevine.. Proceedings of the 8th Meeting of the International Council for the Study of Viruses and Virus Diseases of the Grapevine

Notes: [Conference held in Bari, Ital, September 3-7, 1984.] Electron microscope examination of negative stained preparations of root extracts of grapevine sources showed an association of grapevine leafroll disease with the presence of closterovirus-like particles. Similar particles were present in root extracts of LN 33 indicators showing leafroll disease symptoms two seasons following planting healthy vines in a leafroll-infected 'Tinta Barocca' vineyard. No closterovirus-like particles were observed from vines infected with grapevine stem grooving (legno riccio) disease. Virus transmitted from leafroll infected vines by Planococcus ficus to Nicotiana clevelandii was shown to be serologically similar or identical to grapevine virus A. This virus was also demonstrated in root extracts of grapevines infected with leafroll disease, root extracts of interplanted LN 33 vines, showing leafroll symptoms, and extracts of P. ficus that had fed on a leafroll source. Grapevine virus A and serologically distinct closterovirus-like particles were transmitted by P. ficus from a Shiraz vine infected with the so-called "Shiraz disease" to N. clevelandii. Lack of spread of a severe strain of grapevine leafroll disease over a five year period to 'Waltham Cross' vines, carrying a mild strain, suggests a form of cross-protection similar to that operating for Citrus tristeza virus.