Colletotrichum siamense causing anthracnose-twister disease of onion (Allium cepa) in Sri Lanka

Abstract

Symptomatic samples of anthracnose-twister disease of cultivated onion (Allium cepa) were collected from heavily infected fields at Matale district, Sri Lanka during a severe outbreak that occurred through late July to August in 2020. The pathogen was identified as Colletotrichum siamense based on morphology and combined gene sequence analysis of nuclear ribosomal internal transcribed spacers 1 and 2 with 5.8S region (ITS), glyceraldehyde-3-phosphate dehydrogenase gene (GPDH) and beta-tubulin (TUB) regions. C. siamense is a species with global distribution and a wide host range. This is the first report of C. siamense infecting onion in Sri Lanka.