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

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 springs 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 one week after harvest. Red clover stands were visibly assessed the following spring. Kenland, across all application timings, was injured more by 2,4-D than UK2014 with mean injury ratings of 39% and 63% compared to 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% while 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 7.55 and 7.88 dry matter ton ha-1, respectively in 2017 and 5.28 dry matter ton 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 only reduced 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 reduced UK2014 season total yield across application timings. UK2014 has greater 2,4-D tolerance than Kenland, but additional selection might be beneficial.

Comparative Gene Expression following 2,4-D Treatment in Two Red Clover (Trifolium pratense L.) Populations with Differential Tolerance to the Herbicide

“…Overall, measured by the number of DEGs at each time point in each year, the response of 'UK2014' to 2,4-D was less than that of 'Kenland'. This result was similar to that observed for the phenotypic response between 'Kenland and 'UK2014' by Araujo et al [41] and between the more and less 2,4-D sensitive genotypes of Eurasian watermilfoil (Myriophyllum spicatum) [45].…”

“…Two red clover populations were used in this study: 'Kenland', 2,4-D sensitive, (Victory Seed Company, PO Box 192, Molalla, OR, USA) and 'UK2014', a 2,4-D tolerant selection (University of Kentucky, Lexington, KY, USA) [41]. Plants were grown in a field setting at the University of Kentucky's Spindletop Research Farm in Lexington, Kentucky (38 • 07 ′ 44 ′′ N, 84 • 29 ′ 46 ′′ W).…”

“…2,4-D was applied at the bud to the early-flowering stage, corresponding to 25% of the plants flowering, on 10 August 2015, and 18 August 2018 [41]. Each field plot was sprayed once, either with a mock treatment (water only) or 2,4-D amine (Loveland Products Inc.®P.O.…”