Abstract
Hitherto unreported witches' broom of Hibiscus heterophyllus, native rosella, was found in Toowoomba, Queensland, Australia. Petiole and stem tissues of both affected and normal plants were examined by light and electron microscopy. Mycoplasmalike organisms (MLOs) were detected in the phloem elements of diseased plants, but were absent from the control normal plants. In fluorescence microscopy with DAPI (4', 6-diamidino-2-phenyl-indole⋅2HCl), these MLO fluoresced specifically. After staining with aniline blue, abnormal accumulation of callose in affected phloem cells, as compared with healthy ones, was observed as strongly fluorescing spots. Phloem of diseased tissues displayed positive Dienes' staining.
