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Pea Streak Virus Transmission from Alfalfa to Peas: Virus-Aphid and Virus-Host Relationships. R. O. Hampton, Research Plant Pathologist, U.S. Department of Agriculture, Agricultural Research Service, Oregon State University, Corvallis 97331. K. A. Weber, Research Assistant, Department of Botany and Plant Pathology, Oregon State University. Plant Dis. 67:305-307. Accepted for publication 21 August 1982. 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, 1983. DOI: 10.1094/PD-67-305.

Isolates of pea streak virus (PSV) derived from pea aphids (Acyrthosiphon pisum) occurring naturally on field-grown alfalfa (Medicago sativa) plants were indistinguishable serologically and by particle morphology from the Wisconsin type isolate PSV-W, differing only in pathogenicity to a few hosts. Pea aphids given acquisition access on PSV-infected alfalfa plants transmitted PSV to pea test plants (three aphids per plant) at frequencies of 2535%, which was about half the rate of aphids fed on PSV-infected pea (Pisum sativum) or bell bean (Vicia faba var. minor) plants. After acquisition access periods of 1.5 0.5 min on PSV-infected pea plants, apterous pea aphids retained PSV inoculativity for at least 2 hr of postacquisition fasting at 22 C. These results supported field observations of PSV spread to peas by alate pea aphids presumed to have migrated from alfalfa fields over a distance of 12.2 km. The incubation period of PSV in alfalfa plants after mechanical inoculation was 2 mo, whereas pea aphids fed on inoculated pea or bell bean plants 1015 days after plant inoculation transmitted PSV. Aphids were unable to acquire PSV from infected alfalfa plants growing in the greenhouse or field when daytime maximum temperatures of 3540 C prevailed. Although PSV was readily obtained from natural aphid populations on field-grown alfalfa plants, aphids removed from other proximal legume species did not transmit PSV.