New record of anthracnose disease in leaves of <em>Plumeria pudica</em> in Sri Lanka

Abstract

Plumeria pudica L. is a deciduous ornamental shrub that belongs to the family Apocynaceae and is widely cultivated in Sri Lanka as a cosmopolitan ornamental plant. It has been reported that the anthracnose disease affects many tropical and subtropical fruits, vegetables, and foliage plants. Colletotrichum gloeosporioides or C. acutatum were reported as pathogens presently accepted as species complexes. In January 2021, a new fungal disease was observed on P. pudica, within the premises of the Eastern University, Sri Lanka, Vantharumoolai, Sri Lanka. Symptoms initiated as irregular necrotic spots that enlarged with pale brown borders. Later, the spots turned grayish-black, nearly rounded without lesions and haloes on the adaxial side of the matured leaves. Diseased leaf samples (10) were collected from three different trees inside the premises. Small pieces of infected leaves were used to isolate the pathogen on Potato dextrose Agar ( PDA) following the standard protocols. Forty colonies with similar morphology were obtained from diseased leaves. The colonies were white to gray and olivaceous in reverse after seven days of incubation under 27 °C. The morphological characters of fungal colonies, conidia, and appressoria were consistent with those of Colletotrichum sp., isolated from several other ornamental plants. Thus, based on these morphological characteristics, the pathogen was identified as Colletotrichum sp. Pathogenicity of the fungus was confirmed by performing Koch’s postulates using healthy detached leaves of P. pudica. This is the first report of Colletotrichum sp. causing anthracnose in P. pudica in Sri Lanka. This finding warrants the species-level identification of the pathogen using molecular data. The present work also lays the foundation for future studies on managing the disease in P. pudica under nursery or marketing conditions.