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Disease Note

First Report of Tomato Spotted Wilt Virus in Peppermint (Mentha piperita). D. M. Sether, Department of Entomology, Oregon State University, Corvallis 97331-2907. J. D. DeAngelis, and P. A. Rossignol. Department of Entomology, Oregon State University, Corvallis 97331-2907. Plant Dis. 75:644. Accepted for publication 21 January 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0644C.

The impatiens serotype of tomato spotted wilt virus (TSWV-I) was found infecting peppermint (Mintha X piperita L. 'Black Mitcham') in a research greenhouse in Corvallis, Oregon, in August 1990. The plants were rooted cuttings taken from a nearby outdoor propagation bed. Enzyme-linked immunosorbent assays (ELISAs) against the TSWV-1 serotype (Agdia, Inc., Mishawaka, IN) were positive for samples of midstem leaf tissue (replicate samples assayed on 25 August). Subsequent assays (3 September) detected TSWV-I virus in midstem leaves, rhizomes, and roots from symptomatic plants. Stem tissues from otherwise virus-positive plants were always ELISA-negative. Plants positive to TSWV-I and assayed against the lettuce serotype (TSWV-L, Agdia, Inc.) also were negative. Transmission electron microscopy of leaf tissue revealed spherical particles with diameters varying between 77 and 87 nm. Leaves of Chenopodium quinoa Willd. that were sap-inoculated from leaves of symptomatic peppermint developed brownish gray lesions after 4 days and were TSWV-I ELISA-positive after 14 days. Symptoms of peppermint plants with positive reactions included stunting and general decline. Newly mature, dark green leaves developed bright yellow, irregular mottling. Older leaves became bronze then, often, completely yellow and developed irregular, brownish gray, sunken lesions. Serological results indicated highest virus titers in rhizome tissue and mature, dark green leaves showing a bright yellow mottling; titers were generally low in stem tissue and completely yellow leaves. Detection of virus in rhizomes and roots may indicate systemic spread of infection in peppermint.

Reference: (1) M. D. Law and J. W. Moyer. J. Gen. Virol. 71:933,1990.