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Etiology

Detection of Blueberry Shoestring Virus in Xylem and Phloem Tissues of Highbush Blueberry. L. A. Urban, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; D. C. Ramsdell(2), K. L. Klomparens(3), T. Lynch(4), and J. F. Hancock(5). (2)(4)Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; (3)Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, Director of the Center for Electron Optics, Pesticide Research Center, Michigan State University, East Lansing; (5)Department of Horticulture, Michigan State University, East Lansing. Phytopathology 79:488-493. Accepted for publication 6 December 1988. 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, 1989. DOI: 10.1094/Phyto-79-488.

To study the long-distance movement of blueberry shoestring virus (BBSSV) in highbush blueberry, 3-yr-old healthy bushes were inoculated with BBSSV-diseased buds. The stem was then either girdled below the bud, above the bud, or not girdled. After several months, leaves were tested from above and below the girdled area, using dot blot immunoassay, to determine virus movement. Also, cDNA dot-hybridization and fluorescent antibody labeling were used to determine whether BBSSV moves in the phloem, xylem, or both tissues. No virus was detected in leaves above or below the girdle, when they were tested 1 mo after budding. Two months after budding, one of 15 plants girdled above the diseased bud tested positive for BBSSV antigen. Three and four months after budding, eight and nine, respectively, of 15 plants girdled above the diseased bud tested positive for BBSSV antigen. Six months after budding, leaves above and below the girdled areas were positive for BBSSV antigen. Cross sections (6 µm thick) of young symptomatic stems, made with a cryostat and stained with fluorescent antibody-labeled anti-BBSSV IgG, revealed BBSSV antigen associated with xylem elements. Mechanically separated xylem and phloem tissue were taken from symptomatic stems, extracted, and spotted onto nitrocellulose membranes coated with anti-BBSSV IgG. When probed with ³²P-labeled cDNA to BBSSV RNA, BBSSV RNA was identified in the samples, indicating that whole virus was present as well as viral antigen in both phloem and xylem stem tissues.