Abstract
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 cells in singly infected plants, the same effects were found in most leaf cell types in mixedly infected plants.