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ARS Home » Pacific West Area » Logan, Utah » Forage and Range Research » Research » Publications at this Location » Publication #305862
Title: Natural glyphosate tolerance in sweetvetch Hedysarum boreale

Author
item Peel, Michael
item RANSOM, COREY - Utah State University
item Mott, Ivan
item Waldron, Blair

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2015
Publication Date: 6/26/2015
Citation: Peel, M., Ransom, C.V., Mott, I.W., Waldron, B.L. 2015. Natural glyphosate tolerance in sweetvetch Hedysarum boreale. Crop Science. 55:2368-2376.

Interpretive Summary: Sweetvetch (Hedysarum borealt Nutt.) a legume native to the western USA and Canada has been observed to tolerate glyphosate herbicide. The effect on forage yield and survival of eight rates of glyphosate on seedlings and mature plants were determined. Treatment rates were 0.0, 0.25X, 0.50X, 1X, 2X, 4X, 8X, and 16X times a rate of 841 g ae/ha (1 quart per acre roundup original). Tall fescue was included as a susceptible check. The estimated dose required to cause a 50% reduction (GR50) in sweetvetch seedling yield was 5,025 and 1,636 g ae/ha (2 to 4 qt per acre) at first and second harvests, respectively. Tall fescue seedling BMY GR50 values were 373 and 512 g ae/ha (1/2 qt per acre) at the first and second harvests, respectively. The dose estimated to cause 50% mortality (LD50) in sweetvetch seedlings was over four-fold higher than the highest treatment rate, compared to tall fescue at 918 g ae/ha (just over 1 qt per acre). Four weeks following a spring field treatment, sweetvetch and tall fescue mature plant yield GR50 values were 3,467 and 549 g ae/ha (4 and 3/4 qt per acre), respectively. Thirteen months following the spring treatments GR50 values averaged 11,596 g ae/ha (14 qt per acre) for sweetvetch and 886 g ae/ha (1 qt per acre) for tall fescue. Fall applied glyphosate yield GR50 values from harvests the following spring, nine months after treatment, were nearly three-fold greater than the highest treatment applied for sweetvetch and 413 g ae/ha (1/2 qt per acre) for tall fescue. The LD50 values for mature sweetvetch plants were over four-fold higher for spring treatments and over two-fold higher for fall treatments than the highest treatment rate. The average LD50 for mature tall fescue plants was 70% g ae/ha (just under 1 qt per acre). Based on the LD50 and GR50 values sweetvetch will easily withstand a typical glyphosate treatment rate of 841 g ae/ha (1 qt per acre) and should be considered glyphosate tolerant.

Technical Abstract: Sweetvetch (Hedysarum boreale Nutt.) a legume native to the western USA and Canada, is purported to have tolerance to glyphosate {N-(phosphonomethyl) glycine} herbide. Eight rates of glyphosate were tested for their effect on biomass yield (BMY) and survival of seedlings and mature plants. Treatment rates were 0, 210, 420, 841, 1,681, 3,363, 6,725, and 13,450 g ae ha-1. Tall fescue (Festuca arundinaceae Schreb.) was included as a susceptible check. The estimated dose required to cause a 50% reduction (GR50) in sweetvetch seedling BMY was 5,025 and 1,636 g ae ha-1 at first and second harvests, respectively. Tall fescue seedling BMY GR50 values were 373 and 512 g ae ha-1 at the first and second harvests, respectively. The dose estimated to cause 50% mortality (LD50) in sweetvetch seedlings was over four-fold higher than the highest treatment rate, compared to tall fescue at 918 g ae ha-1. Four weeks following a spring field treatment, sweetvetch and tall fescue mature plant BMY GR50 values were 3,467 and 549 g ae ha-1, respectively. Thirteen months following the spring treatments GR50 values averaged 11,596 g ae ha-1 for sweetvetch and 886 g ae ha-1 for tall fescue. Fall applied glyphosate BMY GR50 values from harvests the following spring, nine months after treatment, were nearly three-fold greater than the highest treatment applied for sweetvetch and 413 g ae ha-1 for tall fescue. The LD50 values for mature sweetvetch plants were over four-fold higher for spring treatments and over two-fold higher for fall treatments than the highest treatment rate of 13,450 g ae ha-1. The average LD50 for mature tall fescue plants was 708 g ae ha-1. Based on the LD50 and GR50 values sweetvetch wil easily withstand a typical glyphosate treatment rate of 841 g ae ha-1 and should be considered glyphosate tolerant.