Molecular Identification of Colletotrichum Species Associated with Ornamental Curcuma Leaf Lpot in Northern Thailand
Rochelle Cagadas1, Sukanya Haituk1,2, Sirikanlaya Sittihan1, Supitchakorn Thungdee1 and Ratchadawan Cheewangkoon1*
1Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai50200, Thailand
2Office of the Research Administration, Chiang Mai University, Chiang Mai50200, Thailand
Colletotrichum is one of the economically important fungal pathogens that reduce the quality and yield of pre-to postharvest commodities including fruits and vegetables. It also expands the host range due to climate change which was recently observed in ornamental Curcuma (Pathumma) in Chiang Mai Province, Thailand. Necrotic lesions were apparent on the leaves and flowers that coalesced in the advanced stage. The study aimed to confirm the causal pathogen leaf spot of Curcuma through a pathogenicity test coupled with morpho-cultural and molecular characterization. The pathogenicity test on the Curcuma leaves showed similar symptoms with the diseased Curcuma in the field and it was re-isolated to fulfill Koch’s postulates. In addition, the conidia were hyaline, falcate, and aseptate which produced setae after 3 weeks of incubation on a plated PDA. Multi-locus phylogenetic analysis of the internal transcribed spacer regions with intervening 5.8S mrRNA gene (ITS), partial glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH), partial actin gene (ACT), partial beta-tubulin gene (TUB2) sequence data combined using primers pairs namely, ITS4/ ITS5, GDR1/GDF1, ACT-783R/ACT-512F, and Bt-2b/Bt-2a, respectively revealed the proximity of Colletotrichum truncatum species complex clade. This clade includes many important plant pathogens having a negative impact on tropical crops. The result of the study will facilitate the establishment of the management practice against the pathogen and prevent the further spread of the disease.