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Occurrence of Panicle Necrosis and Small Seed as Manifestations of Maize Dwarf Mosaic Virus Infection in Otherwise Symptomless Grain Sorghum Plants. L. K. Edmunds, Research Plant Pathologist, ARS, USDA, Kansas State University, Manhattan 66506; C. L. Niblett, Assistant Professor, Department of Plant Pathology, Kansas State University, Manhattan 66506. Phytopathology 63:388-392. Accepted for publication 26 September 1972. DOI: 10.1094/Phyto-63-388.

In 1970 at Manhattan, Kan., underdeveloped seed were manifest in plots of RS 671 hybrid sorghum where greenbug, Schizaphis graminum biotype C, populations occurred after exsertion and where cool weather with temperature minimums of <16 C prevailed 4 or more consecutive days while seed was in milk to soft dough. Symptoms included development of pigmented necrotic lesions on panicle branches followed by excessive shrinkage of seed. No fungus was consistently isolated from those lesions. A virus, identified as maize dwarf mosaic, strain A, was recovered from affected panicles. We reproduced similar manifestations in the greenhouse by inoculating upper leaves of RS 610 hybrid sorghum plants at anthesis with this virus and then lowering the temperature from 28 C to <16 while seed was in milk to soft dough. The manifestations could not be reproduced without lowering the temperature. Results agree with observations made among irrigated fields in southwestern Kansas where in recent years, large populations of both greenbug and corn leaf aphid, Rhopalosiphum maidis, have occurred after exsertion.