Evidence that bean golden mosaic virus invades non-phloem tissue in double infections with tobacco mosaic virus

Bean leaves that had been doubly infected systemically with the legume strain of tobacco mosaic virus (CP-TMV) and bean golden mosaic virus (BGMV) were studied ultrastructurally. Virus particles and the cytopathological changes associated with each virus in single infections occurred within the same cell when plants were doubly infected, indicating that individual systemically infected host cells can multiply viruses of different nucleic acid composition. Although the cytopathic effects induced by BGMV are limited to phloem-associated c lls in singly infected plants, he same effects were found in most leaf cell types in mixedly infected plants. Mixed infections by plant viruses are common but have been relatively little studied (Matthews, 1981). Thus, information concerning the ultrastructure of mixed virus infections is sparse, although recent reports by Gill & Chong (1981) and Carr & Kim (1983), indicate that ultrastructural features in mixedly infected cells may be useful in discriminating related viruses or strains of the same virus. This paper describes cytopathological effects occurring in leaf cells infected with the legume strain of tobacco mosaic virus (CP-TMV), an RNA virus with rod-shaped particles, and bea