Population genetics of herbicide resistance in waterhemp

Waterhemp populations resistant to herbicides that inhibit protoporphyrinogen oxidase (PPO) have been identified throughout the Midwest and the mechanism of resistance in populations from Illinois was previously determined to result from a 3 base pair deletion in the protoporphyrinogen oxidase (PPO)-encoding gene, PPX2. The deletion results in the loss of glycine at position 210 (ΔG210). While resistance is becoming more widespread and waterhemp is becoming more problematic in corn and soybean fields, little is known about waterhemp’s population genetics. The general purpose of this thesis was to gain insight into the population genetics of waterhemp resistant to PPO-inhibiting herbicides. Do all resistant populations have the same mechanism for resistance to PPO-inhibiting herbicides? How did resistance spread? Chapter One reviews the literature surrounding these important issues. Chapter Two discusses research that was done to determine if ∆G210, the previously identified mutation, is responsible for resistance in waterhemp populations outside of Illinois and examines the possible mechanisms for the spread of resistance. These studies revealed that ∆G210 is the only resistance mechanism identified thus far in waterhemp resistant to PPO-inhibitors and the mutation correlates highly with resistance. However, the mechanism of the spread of resistance is not as clear-cut. Genetic analysis did not distinguish whether independent evolution or gene flow was responsible for the spread of resistance, possible due to recombination within the PPX2 gene. Chapter Three discusses the development of a set of microsatellite markers for use in waterhemp population genetics. Although these markers were not useful in determining the spread of herbicide resistant waterhemp in Illinois, they could be useful in a variety of other population studies. The fourth and final chapter discusses concluding remarks, future research, and drawbacks.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2010

Author dc:creator

• Thinglum, Kate A.

Contributors dc:contributor

• Tranel, Patrick J.

• protoporphyrinogen oxidase-inhibiting herbicide
• PPO-inhibitor
• herbicide resistance
• herbicide resistant weeds
• microsatellite markers
• waterhemp
• Amaranthus tuberculatus
• Amaranthus rudis
• Amaranth
• populations genetics
• protoporphyrinogen oxidase (PPO)
• simple sequence repeats (SSR)
• dose-response
• Midwest weeds

Statement dc:rights

• Copyright 2010 Kate A. Thinglum

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/16506

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/16506