VIEW ARTICLE

Etiology

Cytopathology of Leafroll-Diseased Grapevines and the Purification and Serology of Associated Closteroviruslike Particles. F. Zee, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456; D. Gonsalves(2), A. Goheen(3), K. S. Kim(4), R. Pool(5), and R. F. Lee(6). (2)Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456; (3)USDA, University of California, Davis 95616; (4)University of Arkansas, Fayetteville 72701; (5)Department of Horticultural Sciences, New York State Agricultural Experiment Station, Cornell University, Geneva 14456; (6)University of Florida, Citrus Experiment Station, Lake Alfred 33850. Phytopathology 77:1427-1434. Accepted for publication 20 April 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1427.

Thin-section electron microscopy of grapevines infected with two leafroll isolates from California (CA-1 and CA-2) and another from New York (NY-1) revealed the presence of flexuous rod-shaped viruslike particles in the cytoplasm of phloem parenchyma cells and in the sieve elements. Particles about 10–12 nm in diameter, of undetermined length, were associated with membranous vesicles containing fibrils and electron-dense granular material characteristic of closteroviruses. Viruslike particles purified from mature symptomatic leaves of grapevines infected with NY-1 and CA-1 leafroll isolates were between 1,800 and 1,900 nm long. In sodium dodecyl sulfate immunodiffusion tests, NY-1 antiserum reacted with CA-1, CA-2, and NY-1 isolates. With indirect enzyme-linked immunosorbent assay (ELISA), NY-1 antiserum reacted more strongly to homologous than heterologous antigens, thus indicating serological differences among the isolates. With direct ELISA, the NY-1 antiserum reacted with homologous but not with the CA-2 or CA-1 antigens. The consistent association of closteroviruslike particles with the leafroll disease supports previous suggestions that closteroviruses are the causal agents of the disease. However, final proof will require the reproduction of the disease by these viruslike particles.