In situ detection of phytoplasma in spike-disease-affected sandal using DAPI stain

Free-hand sections of spike-disease-affected sandal (Santalum album L.) and its hosts were stained with the DNA-binding fluorochrome, 4,6,diamidino-2-phenyl indole (DAPI), to detect the presence of phytoplasma. Yellow-green fluorescence was detected in the phloem of diseased sandal. While the phloem tissue of healthy sandal and host plants growing close to the spike-disease-affected sandal in the field as well as in glass house did not show fluorescence. The intensity of fluorescence was high in the young stem and inner bark compared to the root, petiole and leaf. When the efficiency of the DAPI stain was compared with Dienes' stain to detect phytoplasma, the latter was found to be less efficient.