OCCURRENCE OF PHYTOPLASMAS IN HAWAII

Using nucleic acid hybridization, polymerase chain reaction (PCR), and transmission electron microscopy (TEM), phytoplasmas were detected in Dodonaea viscosa afflicted with Dodonaea yellows disease in Hawaii. In hybridization tests, a phytoplasma-specific probe for conserved 16S ribosomal RNA genomic sequences of phytoplasmas was used to detect phytoplasmas in diseased plants from the field and greenhouse and a few symptomless plants near diseased ones in the field, but not in healthy plants raised from seed in the greenhouse. PCR amplification and direct sequencing of the PCR products were used to show that the phytoplasma from diseased D. viscosa is closely related to western X-disease phytoplasmas. Pleomorphic bodies resembling phytoplasmas were observed in diseased but not in healthy plants using TEM. These results, and the witches'-broom symptoms of diseased D. viscosa, suggest that phytoplasmas might be involved in the etiology of this disease in Hawaii. This is the first report demonstrating the presence of plant-pathogenic phytoplasmas in the Hawaiian Islands.