Formation of highly branched hyphae by Colletotrichum acutatum within the fruit cuticles of Capsicum spp.

Abstract

This study showed that Colletotrichum acutatum penetrates the cuticle layer of Capsicum spp. fruits by forming a previously uncharacterized structure from appressoria. This unusual structure was localized in the cuticle layer. The structure, formed within 24h post-inoculation (hpi), was a highly branched, well-differentiated hypha which penetrated the epidermal cell at 72hpi. The novel structure, with abnormally thick walls (about 250nm), often formed multiple branches in the affected chilli pepper. This dendroid structure, probably required for penetration, was formed exclusively in the cuticle layer of chilli pepper fruits and was not found when C. acutatum was inoculated onto pepper petals, mango leaves, or fruits of tomato and aubergine. Colletotrichum acutatum produced similar dendroid structures within resistant chilli pepper fruits, but eventually these structures turned dark brown and no further infection in the epidermal cells occurred, implicating the presence of inhibitors of the formation and development of the dendroid penetration structure in the resistant line. © 2011 The Authors. Plant Pathology © 2011 BSPP.