Herbicide-Resistant Tall Fescue with Cytoplasmic Male Sterility Selected by a Mutated Rice Acetolactate Synthase Gene

Selectable markers are important in selecting transgenic cells from nontransgenic cells in genetic transformation. A rice (Oryza sativa L.) acetolactate synthase (ALS) gene containing a single point mutation [OsALS (sm)] can confer resistance to pyriminobac (PM) herbicide. We produced transgenic tall fescue (Festuca arundinacea Schreb.) using the OsALS (sm) gene as a selectable marker and evaluated its herbicide resistance. Calluses were selected by incubation with PM. All regenerated plants had the OsALS (sm) gene. Transgenic plants sprayed with PM were unaffected whereas wild-type plants stopped growing and eventually died in part. Acetolactate synthase activity in transgenic plants treated with PM was lower than that in wild-type plants without PM but higher than that of wild-type plants with PM. These results indicate that the transgenic plants produced OsALS (sm) protein, which conferred PM resistance. One of the transgenic plants was crossed with a cytoplasmic male-sterile plant to prevent the flow of transgenic pollen into the environment. All F₁ plants were male-sterile. The F₁ plants that inherited the OsALS (sm) gene were resistant to PM. Therefore, we used the OsALS (sm) gene not only as a plant-derived selectable marker but also for the production of herbicide-resistant plants. Introducing other agronomically important genes with the OsALS (sm) gene as a selectable marker into tall fescue and crossing with male-sterile plants should improve public acceptance of transgenic tall fescue.