Investigating the origins and evolution of a glyphosate-resistant weed invasion in South America

A - Papers appearing in refereed journals

Gaines, T., Slavov, G., Hughes, D. J., Kupper, A., Sparks, C., Oliva, J., Vila-Aiub, M., Alejandro Garcia, M., Aldo Merotto Jr and Neve, P. 2021. Investigating the origins and evolution of a glyphosate-resistant weed invasion in South America. Molecular Ecology. 30 (21), pp. 5360-5372. https://doi.org/10.1111/mec.16221

AuthorsGaines, T., Slavov, G., Hughes, D. J., Kupper, A., Sparks, C., Oliva, J., Vila-Aiub, M., Alejandro Garcia, M., Aldo Merotto Jr and Neve, P.
Abstract

The global invasion, and subsequent spread and evolution of weeds provides unique opportunities to address fundamental questions in evolutionary and invasion ecology. Amaranthus palmeri is a widespread glyphosate-resistant (GR) weed in the USA. Since 2015, GR populations of A. palmeri have been confirmed in South America, raising questions about
introduction pathways and the importance of pre- versus post-invasion evolution of GR traits. We used RAD-Seq genotyping to characterize genetic structure of populations from Brazil, Argentina, Uruguay and the USA. We also quantified gene copy number of the glyphosate target, 5-enolpyruvyl-3-shikimate phosphate synthase (EPSPS) and the presence of an extra chromosomal circular DNA (eccDNA) replicon known to confer GR in USA populations. Populations in Brazil, Argentina, and Uruguay were only weakly differentiated (pairwise FST £0.043) in comparison to USA populations (mean pairwise FST = 0.161, range = 0.068-0.258), suggesting a single major invasion event. However, elevated EPSPS copy number and the EPSPS replicon were identified in all populations from Brazil and Uruguay, but only in a single Argentinean population. These observations are consistent with independent in situ evolution of glyphosate resistance in Argentina, followed by some limited recent migration of the eccDNA based mechanism from Brazil to Argentina. Taken together, our results are consistent with an initial introduction of A. palmeri into South America sometime before the 1980s, and local evolution of GR in Argentina, followed by a secondary invasion of GR A. palmeri with the unique eccDNA based mechanism from the USA into Brazil and Uruguay during the 2010’s.

KeywordsPalmer amaranth; Amaranthus palmeri; Herbicide resistance; RAD-Seq; Population genomics
Year of Publication2021
JournalMolecular Ecology
Journal citation30 (21), pp. 5360-5372
Digital Object Identifier (DOI)https://doi.org/10.1111/mec.16221
PubMed ID34637174
Open accessPublished as green open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeUnited States: Harnessing next-generation sequencing technologies for eco-evolutionary studies of herbicide resistance and weed biology
BBSRC Strategic Programme in Smart Crop Protection
Publisher's version
Output statusPublished
Publication dates
Online12 Oct 2021
Publication process dates
Accepted15 Sep 2021
PublisherWiley
ISSN0962-1083

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