This invention relates generally to the detection of genetic differences among soybeans. More particularly, the invention relates to soybean quantitative trait loci (QTL) for tolerance to protoporphyrinogen oxidase inhibitors, to soybean plants possessing these QTLs, which map to a novel chromosomal region, and to genetic markers that are indicative of phenotypes associated with protoporphyrinogen oxidase inhibitor tolerance. Methods and compositions for use of these markers in genotyping of soybean and selection are also disclosed.