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Transmission Interference Between Two Isolates of Barley Yellow Dwarf Virus in Macrosiphum avenae. F. E. Gildow, Graduate research assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; W. F. Rochow, research plant pathologist, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and professor of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 70:122-126. Accepted for publication 24 August 1979. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1980. DOI: 10.1094/Phyto-70-122.

Fewer aphids (Macrosiphum avenae) transmitted the PAV isolate of barley yellow dwarf virus (BYDV) if they had first acquired the MAV isolate, than if they had previously fed on healthy oats or on oats infected with other BYDV isolates. The reduction in transmission of PAV by previous acquisition of MAV was consistent in each of 30 experiments done over a period of 3 yr, regardless of varying length of feeding times, temperatures, or age of aphid used. When aphids acquired virus by feeding, the reduction in transmission was 66% in 22 experiments that utilized 905 aphids per treatment. No interference in transmission of PAV by M. avenae occurred in tests with any of three other BYDV isolates, nor was PAV transmission by Rhopalosiphum padi reduced by previous acquisition of other BYDV isolates. The interference by MAV in the transmission of PAV also occurred in M. avenae when MAV was injected into aphids at a concentration of at least 170 μg/ml. When MAV and PAV were injected simultaneously into M. avenae, transmission of PAV decreased as the MAV concentration was increased. A possible mechanism to explain these data, based on competition between the MAV and PAV isolates for virus specific receptor sites on aphid salivary glands, is discussed.