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Etiology

A Lethal Disease of Tomato Experimentally Induced by RNA-5 Associated with Cucumber Mosaic Virus Isolated from Commelina from El Salvador. H. E. Waterworth, Research Plant Pathologist, Science and Education Administration, U. S. Department of Agriculture, Plant Introduction Station, Glenn Dale, MD 20769; M. E. Tousignant(2), and J. M. Kaper(3). (2)Chemist, Science and Education Administration, U. S. Department of Agriculture, Plant Introduction Station, Glenn Dale, MD 20769; (3)Research Chemist, Plant Virology Laboratory, Plant Protection Institute, Beltsville, MD 20705. Phytopathology 68:561-566. Accepted for publication 21 September 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-561.

The virus which causes a mosaic disease in Commelina diffusa in El Salvador was identified as cucumber mosaic virus (CMV) by host range, serology, and electrophoresis of the ribonucleic acid in polyacrylamide gels. Newly isolated virus from commelina (CMV-Com) did not contain detectable amounts of the nongenomic RNA-5 (cucumber mosaic virus associated RNA-5 = CARNA 5). However, CMV-Com was capable of producing substantial amounts of CARNA 5 when CARNA 5 from the CMV-S strain was added to the inoculum; CMV-Com also produced by itself CARNA 5 when passed serially through ‘Xanthi’ tobacco plants. CMV-Com without detectable CARNA 5 (one transfer in tobacco) incited only a mild systemic mosaic in Lycopersicon esculentum ‘Rutgers’ tomato plants, which developed a fernleaf condition without necrosis or death of the plants. Plants inoculated with CMV-Com that contained CARNA 5 (6 transfers in tobacco) developed necrosis, collapsed, and died. Seedlings inoculated when 8 cm tall (20 days old) were dead after 18 to 20 days; those that were 45 cm tall (60 days old and in flower) died within another 60 days. They did not bear fruit, whereas, noninoculated control plants and plants infected with RNA 1-2-3 did bear fruit. This disease appears to be identical to that which devastated the tomato crop in the French Alsace in 1972. Production of CARNA 5 is supported by French and South African strains of CMV. This is the first report of CARNA 5 in the Western Hemisphere.