First Report of Colletotrichum atlanticum Associated With Anthracnose of Torch Ginger (Etlingera elatior) in Southern Thailand

Abstract

Torch ginger (Etlingera elatior), a herbaceous plant in the family Zingiberaceae, is commonly cultivated in the tropical climate of southern Thailand. However, its cultivation faces significant challenges from anthracnose, a destructive disease caused by the Colletotrichum genus. This study aimed to identify and characterise Colletotrichum species associated with anthracnose on torch ginger. Field surveys were conducted in a major torch ginger-growing area in Phatthalung Province, southern Thailand, and symptomatic flower samples were collected for pathogen isolation and identification. Fungal isolates were subjected to pathogenicity tests, revealing that five isolates—EeR01.1, EeR01.2, EeR02.1, EeR02.2 and EeW01—caused symptoms similar to those observed in natural infections. The fungi were re-isolated, and their morphological characteristics matched those of Colletotrichum. Morphological characteristics, coupled with DNA sequences of actin (act), calmodulin (cal), glyceraldehyde-3-phosphate dehydrogenase (gapdh), internal transcribed spacer (ITS) and β-tubulin2 (tub2) regions identified five isolates as Colletotrichum atlanticum. Based on the results of this study, this is the first report of torch ginger as a new host of C. atlanticum in Thailand. This research highlights the precise diagnosis of pathogens and the necessity to find effective disease management strategies to control anthracnose on torch ginger production in southern Thailand.