Study detected glyphosate-resistant Palmer amaranth at ports

1. Glyphosate-resistant weed from the US invades Japan through GM grain imports (commentary from Third World Network)
2. Initial invasion of glyphosate‐resistant Amaranthus palmeri around grain‐import ports in Japan (peer-reviewed paper)
---

1. Glyphosate-resistant weed from the US invades Japan through GM grain imports

Third World Network, 30 Nov 2020
https://biosafety-info.net/articles/assessment-impacts/ecological/glyphosate-resistant-weed-from-the-us-invades-japan-through-gm-grain-imports/

More than 80% of the area planted to GM crops in the US has been planted with herbicide-resistant crops, the most common being glyphosate-resistant. The intensive use of glyphosate has resulted in the evolution of resistance by some 48 weed species in the US, one of the most problematic being Amaranthus palmeri.

Internationally traded grain commodities are recognized as a pathway for the introduction of weed seeds into new areas because similarities in shape and size to crop seeds hinder removal of contaminant weed seeds. The contaminants sometimes include herbicide‐resistant seeds, which can later spill during the transport of grain commodities and become naturalized in importing countries.

The US is the largest source to Japan of corn, soybean, and cotton crops genetically modified to be glyphosate-resistant. A study detected A. palmeri resistant to glyphosate at Kashima, Hakata, and Mizushima ports. The individuals collected from the ports were genetically similar to the US accessions, with no genetic isolation by distance among Japanese and US individuals. Because GM plants have not been commercially cultivated in Japan, their feral occurrence is evidence of spillage during transport of GM grain commodities.

Glyphosate-resistant A. palmeri was first reported in Georgia in 2004. Less than 10 years later, it has become established in Japan, where it has the potential to become a troublesome weed because glyphosate is one of the most widely used herbicides. Another concern is interspecific hybridization within the Amaranthus genus, resulting in more problematic weeds that may serve as conduits for further inter‐population spread of the glyphosate resistance gene.
---

2. Initial invasion of glyphosate‐resistant Amaranthus palmeri around grain‐import ports in Japan

Shimono, A., Kanbe, H., Nakamura, S., Ueno, S., Yamashita, J., & Asai, M.
Plants, People, Planet, 24 September 2020
https://doi.org/10.1002/ppp3.10156
https://nph.onlinelibrary.wiley.com/doi/full/10.1002/ppp3.10156

Societal Impact Statement

The dispersal of alien species is tightly coupled to human activities such as trade and transport. Trade is known to spread troublesome weeds from countries exporting, to those importing, grain. Glyphosate resistant (GR) Amaranthus palmeri is one of the most problematic weeds in the US, which is the largest grain exporter to Japan. We demonstrate that GR A. palmeri has become established in a Japanese port in less than 10 years from the first report of GR A. palmeri in the US. The initial detection of alien species is critical to enable effective control measures to be undertaken, before problematic species are able to spread more widely.

Summary

The US is the largest source to Japan of crops genetically modified to be glyphosate resistant (GR). The intensive use of glyphosate in the US has led to the evolution of GR Amaranthus palmeri, one of the most problematic weeds in the US. Here, we investigated the initial invasion and establishment of GR A. palmeri at grain-importing ports in Japan.

The primary glyphosate resistance mechanism is a copy-number amplification of the 297kb region containing the herbicide target site gene 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). We used quantitative PCR to measure the EPSPS genomic copy number and used PCR to confirm the presence of the other amplified region. We used microsatellite marker analysis to compare the genetic similarities between Japanese populations and US accessions.

We detected GR A. palmeri at three ports: although present as a casual plant at two of the three ports, GR populations were established at one of the ports investigated. The port populations were found to be genetically similar to the US accessions and showed no geographical genetic structure.

This study shows that GR A. palmeri has naturalized in Japan in less than 10 years from the first report of GR A. palmeri in the US.