The first report of Plumeria (Frangipani) rust disease caused by Coleosporium plumeriae in Taiwan

Plumeria rubra (common name: Frangipani), a member of Apocynaceae family, is grown as a popular ornamental tree in parks and landscaped establishments in Taiwan. It bears beautiful, big flowers of various colours and sizes that predominate especially during the summer. In December 2003, uredinia and telia stages of a rust fungus on were found leaves of Plumeria rubra, growing at the Taipei botanical garden in North of Taiwan and Pingtung in South Taiwan. The rust fungus produced orange to yellow spore sori in leaves and in severe infections caused early leaf abscision. Uredinia were hypophyllous, bright yellow or yellow-orange (Fig. 1a). Urediniospores were sub-globose, elliptical or angular (Fig. 1b) and measured 21.6-29.9 x 17.7 - 26.4 µm. Walls were 0.9-1.7 µm thick, light yellow or yellow and coarsely verrucose (Fig. 1c). Telia were hypophyllous, scattered between veins, punctiform, erumpent, smooth and gelatinous and orange-yellow or reddish orange (Fig. 1a). Teliospores were oblong or clavate (45.1 - 86.3 × 12.4 - 22.5 µm), round at the apex and narrow at the base (Fig. 1d). Teliospores were orange-yellow in colour, oily and refractile. Basidia were four-celled (63.7-102.9 x 15.7 -24.9 µm) including pedicel (Fig. 1e). Basidiospores were ellipsoid and smooth walled (20.5-35.8 x 9.6-15.3 µm) (Fig. 1f). Spermogonia and aecia were not found. The morphology of the uredinial and telial stages of the specimens observed on P. rubra is identical to previous descriptions of Coleosporium plumeriae (Traquair & Kokko, 1980).

The occurrence of rust disease on Plumeria was first noticed on P. alba on Guadaloupe Island, West Indies by Patouillard (1902, cited from Dizon et al., 1996); which then spread to Central America. Plumeria spp. was imported from South Asia more than two hundred years ago to Taiwan and there have been no reports of rust on these trees. The rust was noticed on South Pacific islands during 1990's and eight species of Plumeria, including P. rubra were found to be infected by this fungus (Kakishima et al., 1995). More recently, the rust was found affecting in Thailand (To-anum et al., 2004). This is however the first report of Plumeria rust in Taiwan.