Occurrence and identification of Colletotrichum species in mangrove-associated anthracnose

Mangrove forests represent vital components of tropical and subtropical coastal wetland, yet recurrent anthracnose epidemics induce foliar necrosis and growth suppression in these ecosystems. To identify causative pathogens and establish a foundation for disease control, this study investigated anthracnose-affected mangrove species (Bruguiera gymnorrhiza, Excoecaria agallocha, Rhizophora stylosa, and Sonneratia apetala) in Guangdong Province, China. Through morphological and multilocus phylogenetic analyses (actin (ACT), chitin synthase (CHS-1), glyceraldehyde-3-phosphate d ehydrogenase (GAPDH), internal transcribed spacer (ITS), and β-tubulin (TUB2)), eight Colletotrichum isolates were identified: two C. karsti from the C. boninense species complex, and six from the C. gloeosporioides complex (C. endophyticum (two isolates), C. pandanicola (two), C. proteae (one), C. tropicale (one)). Pathogenicity assays confirmed all isolates were pathogenic, with C. endophyticum, C. karsti, and C. tropicale exhibiting the highest virulence. Notably, strains C. endophyticum Guangdong Microbial Culture Collection (GDMCC) 3.1264, C. endophyticum GDMCC 3.1271, C. karsti GDMCC 3.1266, and C. tropicale GDMCC 3.1265 caused the most severe lesions on Rhizophora stylosa. These findings elucidate the etiology of mangrove anthracnose and provide a foundation for targeted biocontrol strategies to conserve coastal ecosystems.