Occurrence and Characterization of a Potexvirus Infecting Arctium minus. L. W. Stobbs, Research Scientist, Research Station, Agriculture Canada, Vineland Station, Ontario L0R 2E0. J. G. Van Schagen, Research Assistant, Research Station, Agriculture Canada, Vineland Station, Ontario L0R 2E0. Plant Dis. 72:314-317. Accepted for publication 22 October 1987. Copyright 1988 Department of Agriculture, Government of Canada. DOI: 10.1094/PD-72-0314.

A previously unidentified potexvirus was isolated from common burdock (Arctium minus) in the Niagara peninsula of Ontario, Canada. Infected plants showed a bright yellow mosaic mottling and stunting of growth. The virus was readily transmitted mechanically but was not seedborne. On the basis of host range studies, no similarity could be found between this virus and other described potexviruses, although immunodiffusion tests revealed serological relatedness with potato aucuba mosaic and clover yellow mosaic viruses. The virus in crude sap from Chenopodium quinoa was infective to a dilution end point of 10^-6 The thermal inactivation point was 58 C, and longevity in vitro at 20 C was up to 13 wk. The virus was characterized by a single sedimenting nucleoprotein (510–540 nm long and 13 nm in diameter), a buoyant density (in CsCl) of 1.304 g/cm³ , an ultraviolet extinction coefficient of 2.47, and an A_260:280 ratio of 1.22. Polyacrylamide gel electrophoresis revealed two proteins with relative molecular masses of 28,300 and 30,500 daltons. Viral RNA, identified by both orcinol and ribonuclease tests, could not be resolved by electrophoresis. The hyperchromic profile (T_m = 74 C) fits that of a single-stranded RNA. Purified viral nucleoprotein had an isoelectric point between pH 4.0 and 4.5.