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Selective Virus Transmission by Rhopalosiphum padi Exposed Sequentially to Two Barley Yellow Dwarf Viruses. W. F. Rochow, Research Plant Pathologist, Northeast Region, Agricultural Research Service, U.S. Department of Agriculture and Professor of Plant Pathology, Cornell University, Ithaca, New York 14850; Phytopathology 63:1317-1322. Accepted for publication 10 April 1973. DOI: 10.1094/Phyto-63-1317.

Although Rhopalosiphum padi does not regularly transmit the MAV isolate of barley yellow dwarf virus from MAV-infected oats, it often transmits MAV, together with the serologically unrelated RPV isolate, from plants doubly infected by MAV and RPV. Attempts were made during a 10-year period to duplicate this dependent transmission of MAV from plants by permitting interaction of the two viruses within R. padi. No evidence for dependent transmission of MAV was found in any of 31 experiments when R. padi fed on plants infected by one virus and then was exposed to the other virus by feeding on infected leaves, by injection with concentrated virus, or by feeding through membranes on virus preparations. No evidence for dependent transmission of MAV occurred in 15 experiments based on allowing R. padi to feed through membranes on, or injecting the vectors with, inocula made by mixing concentrated virus preparations of each of the separate viruses. These data strengthen the conclusion based on previous indications that dependent transmission of MAV by R. padi results from simultaneous synthesis of the two viruses in the doubly infected plant and not from interaction of the viruses within the vector.