Submitted to: Mississippi Academy of Sciences Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/20/1999
Publication Date: 1/10/2000
Technical Abstract: Colletotrichum acutatum is found worldwide on a number of strawberry hosts, and is increasing in importance as the cause of strawberry petiole, stolon, crown, and root infections. Colletotrichum fragariae is often associated with anthracnose crown rot in strawberry and seems to be restricted to the southeastern United States, while C. acutatum is usually the causal agent of anthracnose fruit rot. These pathogens infect strawberry petioles and stolons and cause the dark sunken lesions typical of anthracnose. We inoculated petioles and stolons by misting with conidial suspensions (1.5x 10x6 spores/ml) of C. acutatum and C. fragariae and incubating at 28 degrees C and 32 degrees C respectively and 100 percent RH. We observed at the light as well as the ultrastructural level the ontogeny of the infection process by both pathogens on the 'Chandler' strawberry cultivar. Following cuticular penetration via an appressorium, subsequent steps of invasion by both C. acutatum and C. fragariae involve growth within the cuticle and within the cell walls of epidermal, subepidermal, and subtending cells. Both fungi have a necrotrophic nature, but occasionally they are seen penetrating living cells. Acervuli (the reproductive structures) are formed once the cortical tissue has experienced moderate disruption and begins with the development of a stroma in the tips of the epidermal cells. The acervuli develop under the cuticle of the host and erupt through the cuticle to produce conidia.