Zingiberene, a sesquiterpene, was detected in the foliage extract of L. hirsutum f. hirsutum Humb. and Bonp1. (hir), and confirmed by GC-MS. Zingiberene does not exist in L. hirsutum f. glabratum C. H. Mull (gla), which instead contains 2-tridecanone. 2-Tridecanone confers resistance to gla against Colorado Potato Beetle. The Presence of Zingiberene is associated with resistance against Colorado Potato Beetle in hir, which does not contain 2-tridecanone. The gene that conditions zingiberene acts differently in two different genetic backgrounds. In gla × hir this gene acts as a single recessive gene, while in L. esculentum × hir it acts as a single dominant gene. This situation, which has been studied in F 2 and backcross populations of crosses in both directions are examined and discussed.