Colletotrichum truncatum pathosystem on Capsicum spp: Infection, colonization and defence mechanisms

Abstract

The disease cycle of the chili (Capsicum annuum) anthracnose fungus Colletotrichum truncatum (formerly C. capsici) was elucidated from a study of infection and colonization of seed, leaves and fruit. Microscopic observations of detached leaves and fruit inoculated with a virulent pathotype (F83B), revealed direct cuticle penetration and, intramural, endophytic and necrotrophic phases of colonization. Seedling and fruit ripening stages were very susceptible to infection with the pathogen causing pre- and post-emergence damage and postharvest fruit rot. Furthermore, a quiescent stage, following leaf infection during the vegetative phase of plant growth served as a potential primary inoculum source for fruit infection. Leaf epidermal cells of the resistant C. chinense PBC932 expressed a strong hypersensitive response 48 h after infection (HAI) to both highly virulent (F83B) and less virulent (BRIP 26,974) pathotypes. Infected cells had thickened cell walls, cytoplasm aggregation, and high levels of reactive oxygen species produced 12 HAI. In contrast, the infected epidermal cells of the susceptible C. annuum cultivar Bangchang showed necrosis and rapid cell death after infection by either pathotype. Knowledge of the disease cycle of C. truncatum will be helpful in understanding the behaviour of the pathogen in chili fields which will lead to more efficient application of control measures.