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Phytoplasmas were extracted from flavescence dorée‐infected broadbean (Vicia faba) using a vacuole isolation medium, and were immunoaffinity purified from infected leafhoppers. Purified phytoplasmas from both host sources were immunolabelled and observed under the electron microscope. The infectivity of the purified phytoplasmas from leafhoppers was checked by injecting healthy leafhoppers which were then allowed to feed on healthy V. faba seedlings. The appearance of typical symptoms in these plants, and the positive results obtained in ELISA with extracts of some of the injected leafhoppers and with symptomatic V. faba, indicated that the purified phytoplasmas had retained their infectivity and had multiplied in the injected leafhoppers which had become infective. These results support a previous report that phytoplasmas purified by immunoaffinity chromatography are well preserved.

Eleven stable hybridoma cell lines secreting monoclonal antibodies specific for FD-phytoplasma, the pathogenic agent of grapevine Flavescence dor6e, were produced by fusing a non-secreting myeloma cell line with spleen cells from Balb/c mice immunized with Flavescence dor6e phytoplasma purified by immunoaffinity. These monoclonal antibodies were characterized for their recognition of phytoplasma proteins by western blot. Six of eleven reacted specifically in ELISA and immunoblotting with Elm-yellows phytoplasma. These antibodies did not react either in ELISA or in western blot with preparations from periwinkles infected with phytoplasmas that cause GYU (Grapevine Yellows from Udine), AP (Apple Proliferation), EAY (European Aster Yellows) and Stoic (Stolbur from France). Two of these hybridoma lines were used routinely for the immunodiagnosis of Flavescence dor6e phytoplasma in diseased grapevines.Abbreviations: ELISA -Enzyme linked immunosorbent assay; FD -Flavescence dor6e; MLO -Mycoplasmalike organism; EY -Elm yellows.

Five stable hybridoma cell lines secreting monoclonal antibodies (Mabs) specific for GLRaV-1, one of the agents involved in the aetiology of grapevine leafroll disease, were produced by fusing a nonsecreting myeloma cell line with spleen cells from BALB/c mice immunized with purified GLRaV-1. The Mabs were characterized for their recognition of virus coat protein by DAS-ELISA and Western blotting. Mab (1G10) reacted specifically in ELISA, immunoelectron microscopy and immunoblotting with both GLRaV-1 and GLRaV-3 coat proteins. Mab 1C4 detected 25 of the 33 GLRaV-1 isolates, while Mab 1B7 reacted with 32 isolates including the eight isolates not recognized by Mab 1C4. Two of these hybridoma lines (2F11 and 2F3) are now used routinely for the immunodiagnosis of GLRaV-1.

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