Genotypic and phenotypic diversity in Colletotrichum acutatum, a cosmopolitan pathogen causing anthracnose on a wide range of hosts.

SUMMARY Colletotrichum acutatum causes anthracnose on a wide range of hosts including woody and herbaceous crops, ornamentals, fruits and conifers. Almond, citrus, lupin, olive and strawberry are some of the crops in which C. acutatum diseases are economically important. With the application of molecular markers and diagnostic PCR over the last 10-15 years, C. acutatum was identified as a major pathogen on a number of hosts instead of or along with C. gloeosporioides. C. acutatum displays high levels of genotypic and phenotypic diversity. The global populations of this cosmopolitan pathogen fit into at least eight distinct molecular groups, A1-A8, which show some degree of correlation with the morphological characteristics and varying patterns of host association and geographical distribution. The pathogen has complex epidemiology, exhibiting pathogenic and non-pathogenic lifestyles on target hosts, non-target crops and weeds. C. acutatum populations also show pathogenic variability and cross-infection potential in relation to a number of hosts. Molecular genetic tools are being developed to investigate the pathogenicity mechanisms of this key pathogen. This article mainly focuses on the global population diversity in C. acutatum, pathogen epidemiology and diagnosis, host colonization processes, and the development of tools for the identification and analysis of genes associated with pathogenicity. Background information on the pathogen origin, host range, disease symptoms and disease management strategies is also provided.