POINSETTIA LEAF CURL, A NEW DISEASE CAUSED BY A GEMINIVIRUS

A serious disorder of unknown aetiology was found on the poinsettia cv . Angelica, a recent introduction to Taiwan. The symptoms of downward leaf curling and vein enation were similar to those of leaf curl disea se on tobacco. The causal agent of the disease was transmitted to heal thy plants of 'Angelica' poinsettia, common poinsettia and tobacco by whiteflies. Twinned particles measuring 16-18 x 30-32 nm were detected in a purified preparation obtained from diseased leaf tissues of 'Ang elica' poinsettia, indicating that the disease is caused by a geminivi rus. An earlier introduction of common poinsettias also showed mild le af curl symptoms under natural condition. When the causal agent of thi s disease was transmitted to healthy 'Angelica' poinsettia plants by w hiteflies or bud grafting, these plants also developed severe leaf cur l symptoms, indicating that the disease is not a new introduction to T aiwan.