TITLE:
Variation in 5-Enolpyruvylshikimate-3-Phosphate Synthase (EPSPS) Coding Sequences and Glyphosate Response among Cyperus rotundus L. Populations
AUTHORS:
William T. Molin, Charles T. Bryson
KEYWORDS:
Purple Nutsedge, Glyphosate Tolerance, Genetic Diversity, 5-Enolpyruvylshikimate-3-Phosphate
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.10 No.12,
December
31,
2019
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 single nucleotide polymorphisms (SNPs) only a few of which were predicted
to cause an amino acid change 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-2, 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 mechanism such as differences in sequestration,
translocation or cuticle thickness rather than alterations in EPSPS.