Colletotrichum graminicola (Cg) causes anthracnose stalk rot and anthracnose leaf blight of maize and other graminaceous hosts. Anthracnose has been found to occur in the United States since 1855 and occurs in the Americas, Europe, Africa, Asia, and Australia. In the United States alone over 37.5 million acres are infested annually with average yield losses of 6.6 %. Resistance to anthracnose stalk rot in the tropical maize line MP305 was previously localized to a QTL region on chromosome 4 by RFLP mapping by Jung et al. (1994). Utilizing a BC7 segregating population of approximately 5000 genotyped individuals, 856 BC7 individuals were selected as recombinants within the region of interest. The selfed progeny of those 856 individuals were phenotyped to obtain family means and a high-resolution genetic-linkage map was constructed to further resolve the previously described QTL. Initial markers identified two physical contigs within the region of interest. Using public and private physical and genetic integrated maps the gap between the contigs was closed and a complete tiling path through the region was constructed. Additional PCR-based fragment length polymorphic markers were created from BAC end sequences, overgoes and ESTs present on the BAC clones. Subsequent analysis of phenotypic data integrated with the BC7 genetic-linkage map resolved the QTL location to an approximate 3 cM region (~400kb physical distance) with a peak LOD score of approximately 55. This 400kb region was sequenced using the corresponding BACs from a library made from the resistant parent and a candidate gene for resistance to Cg was discovered in the region. In subsequent analysis four independent Mu insertion events were identified in putative susceptible mutants derived from a targeted Mu-transposon population containing the resistance gene. Sequence data confirmed the presence of the Mu element within the candidate gene causing these plants to be susceptible to Cg.