Maize Anthracnose Stalk Rot in the Genomic Era

Anthracnose stalk rot (ASR) of maize results in millions of dollars in losses annually in the United States. ASR, together with anthracnose leaf blight and anthracnose top dieback, is caused by the fungus Colletotrichum graminicola. Current ASR management recommendations emphasize host resistance and reduction of plant stressors (e.g., drought, heat, low fertility, or soil acidity). Stress reduction may be more difficult to achieve in the future due to more high-intensity production protocols and climate change. Moreover, cultural and chemical management practices may conflict with other important goals, including environmental sustainability and maximization of yield potential. Thus, future ASR management may rely more heavily on host resistance, for which there are relatively few highly effective sources. The last comprehensive review of C. graminicola and maize anthracnose was written over two decades ago. The genomic age has brought important new insights into mechanisms governing the host-pathogen interaction from the application of molecular and cytological technologies. This review provides a summary of our current model of maize anthracnose etiology, including how increased knowledge of molecular and cellular events could contribute to better ASR management. Improved understanding of C. graminicola taxonomy has confirmed that the fungus is specific to Zea mays, and that it colonizes living maize tissues via a critical biotrophic phase. Successful biotrophic establishment relies on an array of secreted protein effectors and secondary metabolites produced at different stages of infection and dispersed to multiple locations. These molecules could provide therapeutic targets for the next generation of transgenic or gene-edited ASR-resistant hybrids.