Engelbrecht, D.J., & Kasdorf, G.G.F. 1987 Occurrence and transmission of grapevine virus A in South African grapevines.. South African Journal of Enology and Viticulture 8(1): 23-29.

Notes: Antiserum prepared to a local isolate of GVA was used in immunosorbent EM (ISEM) with decoration and in an unlabelled antibody ELISA for screening grapevine sources for the presence of virus. GVA occurred extensively in vineyards showing visual symptoms of leafroll or indexing positive for leafroll. It was not found to be associated with either stem pitting or fleck symptoms. It occurred mostly in association with undecorated closterovirus (CV)-like particles. Limited ISEM with decoration of the CV-like particles using antiserum to a Swiss isolate of CV 2 200 nm, (CV type 1) confirmed the presence of a second CV in local grapevine sources. In addition, it indicated the presence of a third CV-like particle longer than GVA. GVA together with undecorated CV-like particles were also detected in initially GVA-free LN-33 grapevines growing under field conditions and naturally infected with leafroll. GVA and CV type I were also present in the vine mealybug, Planococcus ficus, following exposure to a grapevine source carrying these viruses. However, due to lack of CV type 1 antiserum, only GVA was confirmed in grapevine following controlled transmissions with P. ficus although undecorated CV-like particles were present. The reliability of the ELISA detection procedure appears to be influenced by seasonal fluctuations in GVA concn.