Abstracts of the conference 'phytoplasma and virus diseases of forest trees' (IUFRO-WP 07.04.02), College of Environmental Science and Forestry, State University of New York, Syracuse, NY, USA, June 11-13, 1997

Tomato mosaic tobamovirus (ToMV) infects red spruce (Picea rubens Sarg.) throughout its range in the north-eastern United States, and causes significant changes in the growth and physiology of seedlings. Knowledge of virus distribution in infected individuals is essential for accurate and precise assessment of infection. Therefore, our objective was to determine the location of ToMV in infected red spruce seedling roots using indirect immunolocalization of the vital coat protein. Roots of infected seedlings were fixed in FAA (formaldehyde-acetic acid-alcohol) and embedded in paraffin. Longitudinal sections (8 μm thick) were stained using anti-ToMV IgG followed by an FITC-labelled goat anti-rabbit IgG conjugate. Several sections were stained using rabbit normal serum, and served as a negative control. Healthy and ToMV-infected tobacco (Nicotiana tabacum L. cv. Turkish) leaves also were used as positive and negative controls, respectively. No fluorescence was observed in healthy or infected tobacco leaves or red spruce roots using rabbit normal serum. Fluorescence also was not observed in healthy tobacco leaves or red spruce roots using anti-ToMV IgG. However, virus-specific fluorescence was observed in ToMV-infected tobacco leaves and red spruce roots using anti-ToMV IgG. ToMV-specific fluorescence was observed in cortical cells of infected red spruce roots, and was associated with vesicles in these cells. The nature of these vesicles is unknown, but they may represent stress-induced degradation-products of the cytoplasm, possibly due to virus infection. A low level of ToMV-specific fluorescence also was observed in the root cap of infected seedlings. Virus-specific fluorescence was not observed in the meristematic zone of infected roots. These data represent the first report of immunolocalization of a plant virus in conifer tissue.