Non-target-site glyphosate resistance in Conyza bonariensis is based on modified subcellular distribution of the herbicide.
BACKGROUND
Conyza spp. were the first broadleaf weeds reported to have evolved glyphosate resistance. Several mechanisms have been proposed for glyphosate resistance. In an effort to elucidate the mechanism of this resistance in Conyza bonariensis, possible target-site and non-target-site mechanisms were investigated in glyphosate-resistant (GR) C. bonariensis biotypes.


RESULTS
Using differential glyphosate applications and analyses of shikimate accumulation, we followed the herbicide effect in different plant organs and monitored the herbicide's apparent mobility. We found high shikimate levels in the roots and young leaves of glyphosate-sensitive (GS) plants, regardless of the site of application, whereas in GR plants, shikimate accumulated mainly in treated young leaves.14C-glyphosate studies, however, revealed the expected source-to-sink translocation pattern in both GS and GR plants. Sequencing of the appropriate EPSPS DNA fragments of GR and GS plants revealed no alteration at the Pro106 position.


CONCLUSIONS
These data support the hypothesis that the glyphosate resistance of our C. bonariensis GR biotypes is associated with altered subcellular distribution of glyphosate, which keeps the herbicide sequestered away from the EPSPS target site in the chloroplast. © 2016 Society of Chemical Industry.
Robert H Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel.
Ziv
Z
Kleinman
Robert H Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel.
Baruch
B
Rubin
D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D035401:Conyza / Q000187:drug effects* / Q000235:genetics; D005998:Glycine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides / Q000378:metabolism / Q000494:pharmacology*; D020539:Sequence Analysis, Protein; D000097797:Glyphosate
D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase; D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate
5-enolpyruvylshikimate-3-phosphate synthase; non-target-site resistance mechanism; sequestration; shikimate; translocation; uptake