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Factors Affecting Aphid Transmission of Maize Dwarf Mosaic Virus to Corn. J. C. Tu, Postdoctoral Research Associate, Department of Botany and Plant Pathology, Iowa State University, Ames 50010, Present address of senior author: Electron Microscope Laboratory of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada; R. E. Ford, Professor, Department of Botany and Plant Pathology, Iowa State University, Ames 50010. Phytopathology 61:1516-1521. Accepted for publication 27 July 1971. DOI: 10.1094/Phyto-61-1516.

The transmission of maize dwarf mosaic virus (MDMV) from corn by Myzus persicae to corn was closely associated with MDMV concentration in situ. The transmission rate of MDMV with a dilution end point of 1/2,000 was 15% for single aphids and up to 85% for 20 aphids/plant. The maximal MDMV retention time was 25 min, identical for both single and group aphids, whether fasted or nonfasted. However, single-fasted aphids transmitted MDMV more efficiently (15%) than single nonfasted aphids (5%) shortly after (10-min) acquisition. Implications of single versus group aphid transmission of MDMV in nature are discussed. There was no difference in susceptibility of corn to MDMV by aphid transmission when corn was grown under different temperatures when the corn was of uniform size at the time of transmission, and when transmission was done at one temperature. However, the rate of transmission of MDMV differed considerably at different temperatures if corn seedlings were grown under identical conditions except that they were incubated for 1 hr at different temperatures before transmission. Transmission of MDMV was positively related to leaf age and MDMV concentration in vivo. MDMV concentration was lower in older leaves, resulting in decreased aphid transmission. Aphids fed on the mosaic areas of infected leaves transmitted more MDMV (13%) than those fed on nonmosaic areas (3%).