Colletotrichum siamense is associated with post‐harvest anthracnose of red onion in the Philippines.

Onion (Allium cepa L.) is an important crop widely cultivated in the Philippines. In the Philippines, Colletotrichum gloeosporioides sensu lato and C. circinans have been reported to cause anthracnose twister disease and onion smudge, respectively. This study reports C. siamense from anthracnose‐infected onion bulbs. The fungus was identified using morpho‐cultural characterization and multi‐locus analyses of the nuclear ribosomal internal transcribed spacer with 5.8S region (ITS) glyceraldehyde‐3‐phosphate dehydrogenase gene (GAPDH) and beta‐tubulin (TUB2). Koch's postulates were established in pathogenicity assays where the fungus caused diseases in wounded and non‐wounded onion bulbs. This study is the first scientific report of C. siamense as a post‐harvest anthracnose pathogen of onion bulbs in the Philippines. [ABSTRACT FROM AUTHOR]