Field performance of a red clover germplasm selected for increased tolerance to 2,4-D

Authors: ARAUJO, LUCAS - University Of Kentucky; BURKE, TARA - University Of Kentucky; Dinkins, Randy; BARRETT, MICHAEL - University Of Kentucky

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2022
Publication Date: 12/15/2022
Citation: Araujo, L.P., Burke, T., Dinkins, R.D., Barrett, M. 2022. Field performance of a red clover germplasm selected for increased tolerance to 2,4-D. Weed Technology. 36(6):831-837. https://doi.org/10.1017/wet.2022.89.
DOI: https://doi.org/10.1017/wet.2022.89

Interpretive Summary: The objective of this study was to compare the field performance of the red clover germplasm, UK2014, selected for 2,4-D tolerance to the well-adapted Kenland red clover variety grown in the transition zone of the United States. Genetic mapping of the tolerance phenotype derived from the initial 2,4-D resistance found in red clover demonstrated that inheritance is quantitative, and that selection is required to obtain adapted varieties. Our results indicated that the UK2014 line produces similar yields to the Kenland cultivar. While we found a surprising level of tolerance to 2,4-D in Kenland, particularly in terms of sustaining its season total yield under the recommended 2,4-D field rate, UK2014’s total season yield was less impacted by 2,4-D treatments indicating a higher field tolerance to the herbicide. Most importantly, a substantial gain was obtained in improving 2,4-D tolerance in UK2014 line, particularly in terms of season total yields, regrowth after harvest, and second-year spring regrowth. Our study demonstrated that significant progress has been made towards developing a 2,4-D tolerant red clover cultivar that would be adapted to the transition zone of the United States. Future efforts will be directed towards assessing the persistence of UK2014 under pasture-based settings.

Technical Abstract: This study compared the field performance of red clover germplasm UK2014, selected for 2,4-D tolerance, to Kenland, a standard variety grown in the transition zone of the United States. UK2014 and Kenland were seeded in the spring of 2017 and 2018. Single applications of 0, 1.12, or 2.24 kg ae ha-1 2,4-D-amine were made in June, August, or October. One week after the treatments, yields were determined. Visible herbicide injury ratings were made prior to harvest and regrowth was visibly assessed 1 wk after harvest. Red clover stands were visibly assessed the following spring. Kenland, across all application timings, was injured by 2,4-D more than UK2014, with mean injury ratings of 39% and 63% compared with 26% and 37% at 1.12 and 2.24 kg 2,4-D ae ha-1, respectively. At equivalent rates, Kenland regrowth was less than UK2014 at all application timings. UK2014 regrowth after 2,4-D treatment ranged from 65% to 91%, whereas Kenland regrowth ranged from 12% to 72%. Applications of 2,4-D in October were the most damaging to stands of both UK2014 and Kenland the following spring, but Kenland stands were reduced much more than those of UK2014. Kenland and UK2014 had similar season total yields when not treated with 2,4-D (means of 7,550 and 7,880 dry matter kg ha-1, respectively in 2017 and 5,280 dry matter kg ha-1 for both in 2018). Kenland season total yield in 2017 was reduced by both 2,4-D rates applied in June or August and at all timings in 2018. UK2014 season total yield in 2017 was reduced only when 2.24 kg 2,4-D ae ha-1 was applied in August. In 2018, 2.24 kg ae ha-1 2,4-D resulted in reduced UK2014 season total yield across application timings. UK2014 has greater 2,4-D tolerance than Kenland, but additional selection might be beneficial.