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Figwort Mosaic Virus: Properties of the Virus and Its Adaption to a New Host. R. J. Shepherd, Department of Plant Pathology, University of Kentucky, Lexington 40546; R. D. Richins(2), J. E. Duffus(3), and Mary K. Handley(4). (2)Department of Plant Pathology, University of Kentucky, Lexington 40546; (3)U.S. Department of Agriculture, ARS Research Station, 1636 E. Alisal St., Salinas, CA 93905; (4)609 South Eleventh St., Salina, KS 67401. Phytopathology 77:1668-1673. Accepted for publication 11 March 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1668.

Properties and characterization of figwort mosaic (FMV), a caulimovirus, are described. The virus infects plants of the Scrophulariaceae, Chenopodiaceae, and Solanaceae, usually inducing chlorotic mottling symptoms. It is transmissible both mechanically and by aphids. Infected leaves contain amorphous inclusion bodies with an electron dense matrix in which isometric particles of about 50 nm are embedded. FMV is very distantly related serologically to cauliflower mosaic virus (CaMV). It has a slightly smaller sized DNA genome (about 7,750 base pairs vs. 8,031 for CaMV DNA), which exhibits the same conformational forms during gel electrophoresis as CaMV DNA. FMV DNA contains four single-stranded discontinuities as opposed to the three discontinuities in CaMV DNA. The discontinuities were mapped in relation to various restriction endonuclease cleavage sites. The physical map of the genome is distinctly different from that for any other caulimovirus. Virus maintained in Datura innoxia for a 2-yr period produced different symptoms on D. stramonium and reached a concentration in the latter nearly 10-fold higher than the original isolate from figwort. Nucleotide changes occurred in the gene VI portion of the genome of FMV. The gene VI sequence of FMV apparently mutates rapidly during adaptation of the virus to a new host.