First report of rust caused by Coleosporium plumeriae on Plumeria alba in India

Plumeria alba (common name white frangipani) is a deciduous ornamental shrub, which belongs to the family Apocynaceae. The flowers are used in medicine (Gunasingh & Nagarajan, 1980) and in religious ceremonies in India. In June 2007, diseased leaves of P. alba found in Umiam, Meghalaya (North East India) were diagnosed with rust. Orange-yellow pustules were present on lower leaf surface (Fig.1) with corresponding small yellowish lesions on the upper surface (Fig.1). No symptoms were observed on either flowers or stem. Both mature and young leaves were found to be equally susceptible to the pathogen and severe infection often resulted in early leaf abscision.

Uredinia were hypophyllous, erumpent and yellowish in colour. Echinulate uredinospores were light yellow (22.4 - 29.6 x 16.4 - 23.8 µm) with walls 0.8 to 1.4 µm thick (Fig.2). Telia were hypophyllous and reddish orange (Fig.3). Teliospores were clavate, four celled and orange-yellow (76.3 - 93.4 x 17.3 - 22.7 µm). Based on these morphological characters the pathogen was identified as Coleosporium plumeriae (Traquiar & Kokko, 1980; Chung et al., 2006). The hyperparasite Cladosporium cladosporioides was also found associated with uredinia on some leaves (Nowsher et al., 1978). Parasitized pustules were greyish white (Fig.4) and urediniospore walls were collapsed.

Although this pathogen has been mentioned as part of a plant disease survey from Kerala (South India), it was not fully described (Hosagoudar et al., 1996). It has not been reported from anywhere else in India, or adjoining countries. Therefore, this is the first fully described record of C. plumeriae on Plumeria alba in India.