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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Production Systems Research » Research » Publications at this Location » Publication #312188
Title: Possible glyphosate tolerance mechanism in pitted morningglory (Ipomoea lacunosa L.)

Author
item RIBEIRO, DANIELA - Mississippi State University
item Nandula, Vijay
item Dayan, Franck
item Rimando, Agnes
item Duke, Stephen
item Reddy, Krishna
item SHAW, DAVID - Mississippi State University

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2015
Publication Date: 1/27/2015
Citation: Ribeiro, D.N., Nandula, V.K., Dayan, F.E., Rimando, A.M., Duke, S.O., Reddy, K.N., Shaw, D.R. 2015. Possible glyphosate tolerance mechanism in pitted morningglory (Ipomoea lacunosa L.). Journal of Agricultural and Food Chemistry. 63:1689-1697.

Interpretive Summary: Glyphosate is the most historic herbicide ever developed. Aminomethylphosphonic acid (AMPA) is the most frequently detected metabolite of glyphosate in higher plants. The natural tolerance of Ipomoea lacunosa to glyphosate has made these plants among the most common and troublesome weeds in the southeastern U.S. since the adoption of glyphosate-resistant crops. Scientists from Mississippi State University, Crop Production Systems Research Unit (USDA-ARS), and Natural Products Utilization Research Unit (USDA-ARS) conducted greenhouse and laboratory and studies to determine (1) the variability in tolerance to glyphosate among accessions, (2) if there is any correlation between metabolism of glyphosate to AMPA and/or sarcosine and the level of tolerance, and (3) the possible involvement of differential uptake and/or translocation in tolerance to glyphosate. Fourteen I. lacunosa accessions were selected for dose-response assays that resulted in GR50 values ranging from 58 to 151 g ae ha-1 glyphosate, a 2.6-fold variability in tolerance to glyphosate among the accessions. Subsequently, the most tolerant (MT) and the least tolerant (LT) accessions were selected for a differential metabolism study. There was no evidence of the MT accession metabolizing glyphosate to AMPA more rapidly than the LT accession. No metabolism to sarcosine was found. 14C-glyphosate absorption was similar in the MT and LT accessions. The LT accession translocated more (41 and 53% of absorbed at 24 and 48 hours after treatment (HAT), respectively) 14C-glyphosate than the MT accession (26 and 38% of absorbed at 24 and 48 HAT, respectively) out of the treated leaf. Differential translocation may explain, at least in part, tolerance to glyphosate in the MT accession. The above results provide valuable information to growers of Mississippi and the Southeastern US that glyphosate is no longer effective on pitted morningglory populations and alternative control strategies should be implemented.

Technical Abstract: Glyphosate is the most historic herbicide ever developed. Aminomethylphosphonic acid (AMPA) is the most frequently detected metabolite of glyphosate in higher plants. The natural tolerance of Ipomoea lacunosa to glyphosate has made these plants among the most common and troublesome weeds in the southeastern U.S. since the adoption of glyphosate-resistant crops. Experiments were conducted to determine (1) the variability in tolerance to glyphosate among accessions, (2) if there is any correlation between metabolism of glyphosate to AMPA and/or sarcosine and the level of tolerance, and (3) the possible involvement of differential uptake and/or translocation in tolerance to glyphosate. Fourteen I. lacunosa accessions were selected for dose-response assays that resulted in GR50 values ranging from 58 to 151 g ae ha-1 glyphosate, a 2.6-fold variability in tolerance to glyphosate among the accessions. Subsequently, the most tolerant (MT) and the least tolerant (LT) accessions were selected for a differential metabolism study. There was no evidence of the MT accession metabolizing glyphosate to AMPA more rapidly than the LT accession. No metabolism to sarcosine was found. 14C-glyphosate absorption was similar in the MT and LT accessions. The LT accession translocated more (41 and 53% of absorbed at 24 and 48 hours after treatment (HAT), respectively) 14C-glyphosate than the MT accession (26 and 38% of absorbed at 24 and 48 HAT, respectively) out of the treated leaf. Differential translocation may explain, at least in part, tolerance to glyphosate in the MT accession.