Location: Grain, Forage, and Bioenergy ResearchTitle: Reduced translocation is associated with tolerance of common lambsquarters (Chenopodium album) to glyphosate) Author
|De leon, Natalia|
Submitted to: Weed Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/29/2013
Publication Date: 7/1/2013
Publication URL: http://handle.nal.usda.gov/10113/57057
Citation: Yerka, M.K., Wiersma, A.T., Lindenmayer, R.B., Westra, P., Johnson, W.G., De Leon, N. 2013. Reduced translocation is associated with tolerance of common lambsquarters (Chenopodium album) to glyphosate. Weed Science. 61(3):353-360. Interpretive Summary: Common lambsquarters is one of the world’s worst weeds due to its worldwide distribution, its ability to compete with crops to reduce their yield, and its ability to evolve resistance to multiple herbicides. Some common lambsquarters plants in Indiana were recently shown to be tolerant to glyphosate. This is a major concern, since glyphosate is the most commonly used herbicide in the world. To identify the physiological basis for glyphosate tolerance in common lambsquarters, researchers from the University of Wisconsin-Madison and Colorado State University teamed up to identify how glyphosate response among tolerant plants differed from that of sensitive plants. They observed that tolerant plants translocated less glyphosate to the area where the growing point is located than sensitive plants did. If a sufficient amount of glyphosate does not reach the growing point, it cannot kill the plant. The means by which tolerant common lambsquarters plants do this has yet to be discovered.
Technical Abstract: Common lambsquarters tolerance to glyphosate is problematic because of the species’ widespread distribution, competitive ability with many crop species, the widespread use of glyphosate in agriculture, and the weed’s potential to develop decreased sensitivity to multiple herbicide sites of action. The mechanism that confers common lambsquarters tolerance to glyphosate is not known. Therefore, we conducted experiments to determine the mechanism of tolerance to glyphosate in an accession of common lambsquarters from Indiana relative to a sensitive accession from Wisconsin. The ED50 (the effective dose that reduced shoot mass 50% relative to nontreated plants) value for the tolerant accession (1.6 kg ae ha-1 ± 0.4 standard error of the mean [SEM]) was eightfold greater than the ED50 for the sensitive accession (0.2 kg ae ha-1 ± 0.2 SEM) 28 d after treatment. The glyphosate target site (EPSPS) DNA sequence at proline 106, shikimate accumulation as an estimate of EPSPS sensitivity, and EPSPS protein abundance did not differ between accessions. Absorption of 14C-glyphosate was slightly greater in the tolerant accession than it was in the sensitive accession at 48 and 72 HAT. However, the tolerant accession translocated a smaller percentage of absorbed 14C-glyphosate to the tissue above the treated leaf, which included the shoot apical meristem, at 24, 48, and 72 HAT (P = 0.05, 0.01, and 0.10, respectively). These results suggest an important role of reduced translocation in conferring tolerance of common lambsquarters to glyphosate.