DOI: 10.1111/jph.70374 ISSN: 0931-1785
First Report of
Colletotrichum siamense
Causing Leaf Anthracnose on
Indigofera tinctoria
in India
Arnab De, Goutam Mondal, Ankur Mukhopadhyay, Soumik Mukherjee, Dibyendu Ghosh, Pujan Mandal, Rabinath Murmu ABSTRACT
During November–January 2023–2024, severe anthracnose symptoms were observed on indigo (
Indigofera tinctoria
) plants in Kalyani, West Bengal, India, causing irregular necrotic lesions on leaves, pods and apical branches. A morphologically uniform fungal isolate (ITNK‐4) was consistently recovered from symptomatic tissues. On Potato Dextrose Agar, colonies exhibited whitish‐grey, woolly aerial mycelium with hyaline, smooth‐walled, cylindrical conidia and melanised appressoria. Based on these morphological characteristics and a multilocus maximum‐likelihood phylogenetic analysis of the internal transcribed spacer (
ITS
), beta‐tubulin (
TUB2
) and glyceraldehyde‐3‐phosphate dehydrogenase (
GAPDH
) regions, the isolate was identified as
Colletotrichum siamense
. Pathogenicity was confirmed by artificially inoculating healthy
I. tinctoria
leaves with a 14‐day‐old fungal spore suspension, resulting in symptoms identical to those observed in the field, thereby fulfilling Koch's postulates. To our knowledge, this is the first molecularly confirmed report of
C. siamense
causing leaf anthracnose on
I. tinctoria
in India. Given the high economic value of
I. tinctoria
in natural dye production and traditional medicine, the emergence of this pathogen poses a newly characterised threat to its commercial cultivation and warrants further epidemiological monitoring.