First disease report of Cladosporium colocasiae causing leaf spot disease of taro in Thailand

Taro (Colocasia esculenta) is widely cultivated in tropical and subtropical regions in Thailand and is presently grown in almost every area of the humid tropics. In Thailand, people like to consume taro of its unique aroma and good taste. However, taro has been subjected to significant losses from pests and diseases. In October 2022, a severe brown leaf spot disease was observed taro cultivations at the Mae-Hia Agricultural Training and Research Center in the Faculty of Agriculture, Chiang Mai University, Thailand. The symptoms began as brown leaf spots on older leaves. The lesions were observed to be  less evident on the opposite surface of the leaves.  The potential pathogen was obtained from the diseased leaf using single-spore isolation. morphological studies and multilocus phylogenetics analyses with the internal transcribed spacers (ITS) Translation elongation factor 1-alpha (TEF-1α) and actin (ACT) were conducted for the identification and verification of the fungal isolates. the The gene regions were amplified with primer pairs ITS5/ITS4, EF728F/EF986R and Act-512F/Act-783R respectively.The isolates were identified as Cladosporium colocasiae. Pathogenicity assay on detached leaves and seedling roots confirmed the pathogenicity of C. colocasiae. Re-isolation of the pathogen and confirmation studies were done to fulfill Koch’s postulates. Our study provides the, provides the first report of C. colocasiae causing taro leaf spot disease in Thailand.