Variation in 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) coding sequences and glyphosate response among Cyperus rotundus L. populations

Authors: Molin, William; Bryson, Charles

Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2019
Publication Date: 12/31/2019
Citation: Molin, W.T., Bryson, C.T. 2019. Variation in 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) coding sequences and glyphosate response among Cyperus rotundus L. populations. American Journal of Plant Sciences. 10(12):2366-2381. https://doi.org/10.4236/ajps.2019.1012164.
DOI: https://doi.org/10.4236/ajps.2019.1012164

Interpretive Summary: Purple nutsedge is considered to reproduce by clonal propagation and as such one may expect the clones to be genetically identical. Scientists in the USDA-ARS Crop Production Systems Research Unit, Stoneville, MS conducted research to sequence the gene encoding 5-enolpyruvylshikimate-3-phosphate synthase, EPSPS, the target site of glyphosate herbicide, from purple nutsedge from different countries and one yellow nutsedge (Cyperus esculentus) population. The results showed that the sequences were distinct from one another and contained minor alterations. These results indicate that purple nutsedge from different countries has slightly different genetic backgrounds which probably arose from low frequency sexual reproduction.

Technical Abstract: The gene sequence encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), the enzymatic target site of the herbicide glyphosate, was determined for several purple nutsedge (Cyperus rotundus L.) accessions from geographically distant locations and these were aligned to generate a consensus sequence. The EPSPS sequences each had one to several single nucleotide polymorphisms (SNPs) some of which resulted in amino acid changes in the EPSP synthase. None had the proline to serine substitution or other substitutions responsible for glyphosate resistance reported in other species. A dendrogram generated from the cluster analysis of the EPSPS gene sequences indicated similarities between accessions from Tanzania, Indonesia, California*, Greece, Brazil, Argentina and Iran much like cluster analysis previously reported based on RAPD scores and morphological traits possibly indicating a common genetic background or origin. Considering the differences in EPSPS sequences, the response of these purple nutsedge accessions to 0.84 kg ae ha-1 of glyphosate was assessed to determine whether differential tolerance was present. At 7 days after the first application control ranged from 9% for the accession from Greece to 73% for the accession from Tanzania. Control of these accessions increased to 45 and 93 % respectively by 14 days after the second application. The I50’s for glyphosate inhibition of growth for four accessions from geographically distant countries (Mississippi, Brazil, Indonesia and Tanzania) were 0.21, 0.10, 0.25 and 0.06 kg ha-1, respectively, which represented a 4-fold difference. The difference in sensitivity to glyphosate may be a result of a non-target site mechanisms such as differences in sequestration, translocation or cuticle thickness rather than alterations in EPSPS.