Developing a Herbicide Tolerant Red Clover

Adding red clover into grass-based pastures has many benefits but red clover is highly susceptible to herbicides, such as 2,4-D, used for broadleaf weed management in pastures.  In 2005, Dr. Norman Taylor began a project to create a 2,4-D tolerant red clover for Kentucky by crossing a 2,4-D tolerant red clover line from the University of Florida with Kenland red clover.  Dr. Mike Barrett took over responsibility for the project when Dr. Taylor retired.  Over the next 9 years, the progeny from this cross were subject to further selection, treating them with ever higher rates of 2,4-D and preserving the best survivors.  To test the 2,4-D tolerance of the resulting red clover line, designated as UK2014, his research group conducted a field test comparing the 2,4-D tolerance of UK2014 to Kenland. 

While UK2014 is clearly more 2,4-D tolerant than Kenland, Dr. Barrett wanted to see if further selection, under very severe pressure (dipping plants into a 2,4-D solution), could raise the tolerance of UK2014 to 2 Lb. per acre of 2,4-D. Plants grown from seed of plants which survived this treatment through 2 rounds and are currently being grown in the field by Ray Smith and Gabriel Roberts to increase the seed from the selected population.  This involves growing the plants in cages to prevent cross-pollination from other red clover,  introducing bumble bees (the preferred bee species for pollinating red clover) to the cages, and harvesting the seed produced.  Initial greenhouse trials indicate the new selection is more 2,4-D tolerant than UK2014 and, when additional seed is available, this will be tested in field trials. ~ Dr. Mike Barrett

The Alliance for Grassland Renewal is a national organization focused on enhancing the appropriate adoption of novel endophyte tall fescue technology through education, incentives, self-regulation and promotion.  For more resources or to learn more about the Alliance for Grassland Renewal, go to

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