Red-fleshed dragon fruit (Hylocereus polyrhizus) is commonly cultivated in Thailand, especially in southern Thailand, where the weather favors plant growth and development. In 2021, stem canker of H. polyrhizus was observed in a dragon fruit plantation field in Phatthalung Province, southern Thailand. Small, orange circular spots developed on the stem of H. polyrhizus, which later became gray, and the lesion expanded with a mass of conidia. Scytalidium-like fungus was isolated from infected tissues. Based on morphology and phylogenetic analyses of internal transcribed spacer (ITS), nuclear large subunit (LSU) and β-tubulin (tub) sequences of fungal isolates, the fungus was identified as Neoscytalidium dimidiatum. Pathogenicity tests revealed that this isolate caused stem canker on the stem of H. polyrhizus, similar to that observed in the field. Knowledge of the diagnosis of plant diseases is an important step for managing plant diseases and therefore, this finding provides basic information for the development of appropriate strategies to manage stem canker disease on H. polyrhizus plants.
Keywords: molecular identification; morphology; pathogenicity test; pitaya.