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Electron Microscopy of Viruslike Particles From Shoestring-Diseased Highbush Blueberry, Vaccinium corymbosum L.. James X. Hartmann, Departments of Botany and Plant Pathology and Entomology, Michigan State University, East Lansing 48823, Present address of senior author: Department of Biological Sciences, Florida Atlantic University, Boca Raton 33432; James E. Bath(2), and Gary R. Hooper(3). (2)(3)Departments of Botany and Plant Pathology and Entomology, Michigan State University, East Lansing 48823. Phytopathology 63:432-436. Accepted for publication 20 October 1972. DOI: 10.1094/Phyto-63-432.

Viruslike particles measuring 26-28 nm in diam were found in ultrathin sections of leaf and root tissues from highbush blueberry affected by shoestring disease. Leaf epidermal, palisade, and spongy mesophyll cells contained characteristic particles. Particles were found in xylem but not in phloem vascular tissue. Epidermal leaf cells and root xylem cells contained crystalline arrays of particles. Larger masses of viruslike particles were seen in root than in leaf cells. Particles hexagonal in outline and 28-31 nm in diam were partially purified from diseased leaves. No such particles were either observed in, or isolated from, healthy blueberry tissue. Observation of viruslike particles in situ and their isolation from leaves exhibiting typical shoestring disease symptoms is presumptive evidence that they are the incitant of blueberry shoestring disease.