A novel Kentucky adapted red clover line displays increased 2,4-D tolerance

Authors: ARAUJO, LUCAS - University Of Kentucky; WILLIAMS, LINDA - University Of Kentucky; OLSON, GENE - University Of Kentucky; Dinkins, Randy; PFEIFFER, TODD - University Of Kentucky; BARRETT, MICHAEL - University Of Kentucky

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/28/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Incorporation of a legume, such as red clover (Trifolium pratense), into grass-based pasture systems offers many benefits. However, available red clover lines are highly susceptible to herbicides, including 2,4-D (2,4-dichlorophenoxyacetic acid), which is used for broadleaf weed management in pastures. A novel red clover line, UK2014, was developed at the University of Kentucky through conventional breeding and it expresses higher tolerance to 2,4-D than Kenland, a common variety used by Kentucky’s forage producers. Adopting this new tolerant line would broaden weed management options in a legume-grass mixed pasture. The objective of this study was to assess the field performance of UK2014, in terms of yield and 2,4-D tolerance level, and to evaluate the tolerance of UK2014 to grazing in a clover-grass mixture following 2,4-D treatments. UK2014 and Kenland were seeded in April 2017 in Lexington, KY. Treatments consisted of 2,4-D at a low and a high rate (1.12 and 2.24 kg/ha, respectively), applied either early (July), mid (August) or late (October) season. Each plot received only one 2,4-D treatment and treated plots were compared to controls that were not treated with 2,4-D. The entire experiment was repeated in 2018. Visual herbicide injury was evaluated one week after spraying. A visual injury rating was used from 0 (no observed injury) to 100 (death of all plants in the plot). Plots were harvested one week after treatment. Visual regrowth estimates were taken 14 days after treatment, also using a visual rating scale from 0 to 100. Both individual harvest and total season yields (dry matter ton/a) were determined. In April 2018, a grazing tolerance study was estabilished in Lexington, KY. UK2014 and Kenland were interseeded in a tall fescue (Festuca arundinacea) pasture. In May 2018, 2,4-D treatments were applied at 1.68 kg/ha. The plots were submitted to mob grazing in July 19, August 9, and September 11. Red clover and fescue heights, clover stand, and clover dry weight in mixture were measured at grazing dates. Clover stands were evaluated in a 0 (weak) to 5 (very strong) visual scale. Clover dry weights were determined in two subsamples of each plot and expressed as a percentage of the total subsample weight. Data was subjected to analysis of variance and means were separated by Fisher’s Protected LSD at a = 0.05. In the first year of the study, visual injury one week after 2,4-D treatment was less for UK2014 than Kenland, at all treatment dates. Similarly, in plots treated with 2.24 kg/ha 2,4-D, visual estimates of regrowth were higher for UK2014 than Kenland. However, there were no differences in yield between UK2014 and Kenland at individual harvests or in the season total. While this indicated that the performance of UK2014 is equal to Kenland in terms of yield, it also indicated that the 2,4-D injury to Kenland was not enough to reduce its yield. In 2018, preliminary data show that UK2014 had lower injury ratings and higher regrowth ratings than Kenland treated plots. However, unlike in 2017, the early 2,4-D early treatment reduced Kenland yield compared to the untreated Kenland. In the grazing study, 2,4-D treatment did not reduce either the fescue or the clover heights, but sampling date differences were observed indicating larger height means in later dates. The clover stand was reduced in 2,4-D treated Kenland plots, and this reduction was even larger in the percentage of clover dry weight in the mixture.