Cytopathology in the identification and classification of tombusviruses

Ten recognized members of the tombusvirus group, including two strains of tomato bushy stunt virus, were compared for their ultrastructural effects in Nicotiana clevelandii, Gomphrena globosa, and Chenopodium quinoa. The cytopathic inclusions known as multivesicular bodies and tonoplast evaginations containing virus particles were induced by all the viruses in all three hosts. Some of the viruses could be differentiated from each other (especially in C. quinoa) by other characters, such as the accumulation of membranes in cell nuclei, or the type of organelle (chloroplasts, mitochondria or peroxisomes) from which multivesicular bodies developed. The usefulness of these characters for virus identification and grouping is discussed.