Herbicide tolerance developed in cell suspension cultures of perennial white clover

Abstract

Cell suspension cultures of perennial white clover (Trifolium repens L. cv. Regal Ladino) were selected for tolerance to the phenoxy analogs (2,4-dichlorophenoxy)acetic acid (2.4-D), 2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), and 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB). Cells demonstrating up to 6.2-fold increase in tolerance to 4 μg/ml 2,4-D, 7.7-fold increase in tolerance to 8 μg/ml 2,4,5-T, and 3.0-fold increase in tolerance to 2 μg/ml 2,4-DB were obtained within 5 days under the selection procedures. The selection pressures were the phenoxy analogs applied at phytotoxic levels. Whereas the cells that survived each pressure subsequently demonstrated tolerance to all analogs, the cells selected with 2,4-DB as the pressure were more tolerant to all three analogs than were cells selected with 2,4-D or 2,4,5-T. Tolerance, thus gained, was transmitted through succeeding asexually propagated cell generations.