Thesis
EPSPS gene amplification confers glyphosate resistance in downy brome (Bromus tectorum)
Washington State University
Master of Science (MS), Washington State University
08/2020
DOI:
https://doi.org/10.7273/000000067
Handle:
https://hdl.handle.net/2376/125228
Abstract
Glyphosate, a non-selective, systemic, broad-spectrum herbicide has had many commercial
applications for decades. Increased use of glyphosate has led to the evolution of its resistance, now
reported in 31 weed species worldwide. Three downy brome (Bromus tectorum L.) biotypes,
suspected of glyphosate resistance, were collected in Washington state. Glyphosate dose responses
performed at 420, 840, 1681, 3362, 6725, 13450 g ai ha-1 confirmed the suspected resistance
exhibited by the resistant biotypes, ranging between 10 to 25-fold increase in GR50 values
compared to a known field susceptible biotype with a GR50 of 498 g ai ha-1
. Quantitative
polymerase chain reaction (PCR) results supported 5-enolpyruvylshikimate-3-phosphate synthase
(EPSPS) gene amplification as the likely molecular mechanism conferring glyphosate resistance
in all the three resistant downy brome populations. No mutations in EPSPS were found in any
biotype. The EPSPS gene was amplified about 14 to 18 times more on an average with respect to
the EPSPS copy number in the resistant comparted to the known susceptible biotype. The
corresponding increase in EPSPS expression levels were found to be 7.5 to 9 times more in the
resistant biotype than the susceptible biotype. However, no strict correlation was observed between EPSPS copy number and expression levels in the resistant populations of B. tectorum. Glyphosate
resistance in B. tectorum will significantly impact the low-external input dryland wheat fallow
systems practiced in Washington.
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Details
- Title
- EPSPS gene amplification confers glyphosate resistance in downy brome (Bromus tectorum)
- Creators
- Pragya Asthana
- Contributors
- IAN BURKE (Degree Supervisor) - Washington State University, Crop and Soil Sciences, Department ofKAREN SANGUINET (Committee Member) - Washington State University, Crop and Soil Sciences, Department ofCAMILLE M STEBER (Committee Member) - Washington State University, Crop and Soil Sciences, Department of
- Awarding Institution
- Washington State University
- Academic Unit
- Crop and Soil Sciences, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Format
- pdf
- Number of pages
- 62
- Identifiers
- 99900590963301842
- Language
- English
- Resource Type
- Thesis