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Component Ratio Differences in Strains of Alfalfa Mosaic Virus. F. W. Schwenk, Department of Plant Pathology, University of California, Berkeley 94720, Present address of senior author: Department of Plant Pathology, Kansas State University, Manhattan 66502; S. H. Smith(2), and H. E. Williams(3). (2)(3)California State Department of Agriculture, Sacramento 95820, (2)Present address: The Pennsylvania State University, Fruit Research Laboratory, Arendtsville 17303. Phytopathology 61:1159-1163. Accepted for publication 5 April 1971. DOI: 10.1094/Phyto-61-1159.

Viruses isolated from four woody ornamentals, Hebe (hybrid clone ‘Co-ed’), Ilex cornuta ‘Rotunda’, Viburnum opulus, and V. tinus, were shown to be related to alfalfa mosaic virus (AMV) by serology and particle morphology. This is the first known report of AMV isolation from naturally infected Hebe, I. cornuta, and V. tinus. The isolates from the two Viburnum species are considered distinct strains; due to lack of measurable differences, the isolates from Hebe and I. cornuta are considered to be a single strain. This latter strain was distinguishable from each of the other two. Each of the isolates was partially purified from tobacco by polyethylene glycol precipitation, then centrifuged through sucrose density gradients. Three prominent bands were visible in all cases. When gradients were removed through a continuously recording spectrophotometer measuring at 260 nm, three strong absorption peaks corresponding to the three visible bands appeared in the same place in the spectrum for each isolate, though the relative peak heights varied. The isolates from Hebe and I. cornuta produced similar patterns. Each of the strains tested, including one other known strain of AMV, was identifiable by its absorption pattern. This is suggested as a method of AMV identification and of strain differentiation.