First Report of Colletotrichum siamense Causing Anthracnose Disease of Coffee Berry in Indonesia

Colletotrichum species are fungal pathogens that cause anthracnose in coffee berries across producing regions globally. These pathogens have been reported to infect both Coffea arabica and Coffea canephora , but the molecular identification of Colletotrichum species affecting coffee in Indonesia has remained largely uncharacterized. This study aimed to identify and characterize the Colletotrichum species associated with coffee crops. Colletotrichum isolates were obtained from symptomatic berries and leaves collected from C. arabica and C. canephora plantations in seven districts in Indonesia. Identification and characterization of Colletotrichum spp. consisted of morphological characterization, DNA sequencing, and phylogenetic analysis of the internal transcribed spacer (ITS), actin (ACT), and β-tubulin (TUB2) regions. Eleven Colletotrichum isolates were selected for further study based on their morphological characteristics and geographical origins. The results of the multi-locus phylogenetic analysis clustered all eleven isolates within the C. siamense species group. The morphological characteristics of C. siamense generally include grey to dark-grey colony pigmentation. Colony growth rates on potato dextrose agar (PDA) ranged from 7.28 to 12.88 mm/day, and colony diameters were approximately 52–89 mm. A pathogenicity assay confirmed that the isolates were virulent, successfully inducing symptoms on coffee tissues (leaves and berries of Arabica and Robusta coffee). By integrating morphological characterization, molecular identification, and pathogenicity testing, this study identifies C. siamense as the causative agent of coffee berry anthracnose disease in Indonesia. This study presents the first report of C. siamense infection in both Arabica ( C. arabica ) and Robusta ( C. canephora ) in Indonesia.