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Comparative Study of Five Mosaic Virus Isolates Infecting Corn, Johnson Grass, and Sorghum in the United States. Natale Zummo, Plant Pathologist, Crops Research Division, ARS, USDA, Meridian, Mississippi; Donald T. Gordon, Associate Professor of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster, and The Ohio State University, Columbus. Phytopathology 61:389-394. Accepted for publication 12 November 1970. DOI: 10.1094/Phyto-61-389.

Five mosaic virus isolates infecting corn (Zea mays), Johnson grass (Sorghum halepense), or sweet sorghum (S. bicolor) from California, Virginia, Frankfort and Quicksand, Kentucky, and Mississippi, were related serologically on the basis of their reaction with maize dwarf mosaic virus strain A (MDMV-A) antiserum. They were distinct from each other in their effect on plant growth and severity of leaf symptoms on several sweet sorghum cultivars. The Frankfort, Ky., isolate generally produced the most severe leaf chlorosis on cultivars. The Virginia isolate caused a distinctive purplish-black discoloration of leaves of Rio sorghum. The Virginia and Quicksand isolates caused severe stunting of Rio sorghum with frequent killing of the growing points. The California, Quicksand, and Virginia isolates stunted Sugar Drip and Hay Grazer sorghums. Dilution end points distinguished the California, Mississippi, and Virginia isolates, while the thermal death points distinguished the Frankfort and Quicksand isolates. The five isolates were distinct from known strains of sugarcane mosaic virus (SCMV) based on infectivity in Johnson grass and reactivity with MDMV-A antiserum cross-absorbed so that it no longer reacted with strains A, B, D, E, and H of SCMV.