Dynamics of infection-related morphogenesis and pathogenesis in Colletotrichum orbiculare

Colletotrichum orbiculare (syn. C. lagenarium) is the causal agent of anthracnose disease on cucurbit plants. This fungus forms dome-shaped, melanized appressoria as a host invasion structure. Strain 104-T (MAFF240422) of C. orbiculare, which was originally isolated from a cucumber plant in 1951 by Dr. Yasumori, Kyoto University, has proven to be an excellent experimental model for the study of fungal pathogenesis and morphogenesis because of its stable pathogenicity and synchronous infection-related morphogenesis. This review considers the discoveries made during 60 years of study on C. orbiculare. In particular, we focus on advances made in the last two decades, which have provided a basis for the molecular analysis not only of fungal morphogenesis, but also of plant–microbe interactions, including plant immunity to adapted and nonadapted Colletotrichum fungi. This substantial body of innovative research was originated by the Phytopathological Society of Japan and represents a major contribution to the international research communities working on plant pathology, plant–microbe interactions, and fungal molecular genetics. This review deals with the past achievements and future prospects in the study of Colletotrichum biology, focusing on the molecular genetics of C. orbiculare with regard to four aspects: (1) metabolic and functional development of infection structures, (2) signaling pathways required for fungal pathogenesis, (3) pathogen-associated molecular patterns (PAMPs) and host basal resistance, and (4) establishment of host specificity.