Involved in defensive oleoresin formation in conifers in response to insect attack or other injury. Involved in sesquiterpene (C15) olefins biosynthesis (By similarity). (2E,6E)-farnesyl diphosphate = (E,R)-alpha-bisabolene + diphosphate Terpene metabolism; oleoresin biosynthesis. Belongs to the terpene synthase family. Tpsd subfamily.