Infection process of Colletotrichum coccodes tagged with GFP on Solanum tuberosum

Abstract

Potato Black Dot, caused by the fungal pathogen Colletotrichum coccodes, is a severe disease of potato (Solanum tuberosum). To study the pathogenicity process, we developed a C. coccodes transformant tagged with green fluorescent protein (GFP) and used it to infect the potato. The results showed that three transformants with strong fluorescence, which were chosen for molecular and microscopic analyses. No obvious differences in colonical morphology, growth rate or pathogenicity were observed between the wild-type isolate and transformants. According to microscopic observations, mycelia infected stems by 12 h after inoculation and extended into the periderm and epidermis, vascular bundle, and myeloid cells within 24 h; abundant mycelia were produced on the surfaces of diseased stems after 48 h. Moreover, the mycelia extended to surrounding cells along cell walls and intercellular spaces, subsequently, the fungus disrupted cell structure by forming a hyphal network. In stems, the fastest speed of expansion occurred in vascular bundle cells and the slowest in myeloid cells. The results of this work may be useful for studying the infection mechanisms of C. coccodes.