The invention relates to methods and compositions for identifying maize plants that have newly conferred tolerance or enhanced tolerance to, or are susceptible to, Gray Leaf Spot (GLS). The methods use molecular genetic markers to identify, select and/or construct tolerant plants or identify and counter-select susceptible plants. Maize plants that display newly conferred tolerance or enhanced tolerance to GLS that are generated by the methods of the invention are also a feature of the invention.
