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The Evolution and Genetics of Herbicide Resistance in Weeds

Published online by Cambridge University Press:  12 June 2017

Marie Jasieniuk ,
Anita L. Brûlé-Babel  and
Ian N. Morrison
Marie Jasieniuk
Affiliation:
Dep. Plant Sci., Univ. Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2
Anita L. Brûlé-Babel
Affiliation:
Dep. Plant Sci., Univ. Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2
Ian N. Morrison
Affiliation:
Dep. Plant Sci., Univ. Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2
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Abstract

The importance of various factors influencing the evolution of herbicide resistance in weeds is critically examined using population genetic models. The factors include gene mutation, initial frequency of resistance alleles, inheritance, weed fitness in the presence and absence of herbicide, mating system, and gene flow. Where weed infestations are heavy, the probability of selecting for resistance can be high even when the rate of mutation is low. Subsequent to the occurrence of a resistant mutant, repeated treatments with herbicides having the same mode of action can lead to the rapid evolution of a predominantly resistant population. At a given herbicide selection intensity, the initial frequency of resistance alleles determines the number of generations required to reach a specific frequency of resistant plants. The initial frequency of resistance alleles has a greater influence on the evolutionary process when herbicides impose weak selection, as opposed to very strong selection. Under selection, dominant resistance alleles increase in frequency more rapidly than recessive alleles in random mating or highly outcrossing weed populations. In highly self-fertilizing species, dominant and recessive resistance alleles increase in frequency at approximately the same rate. Gene flow through pollen or seed movement from resistant weed populations can provide a source of resistance alleles in previously susceptible populations. Because rates of gene flow are generally higher than rates of mutation, the time required to reach a high level of resistance in such situations is greatly reduced. Contrary to common misconception, gene flow from a susceptible population to a population undergoing resistance evolution is unlikely to slow the evolutionary process significantly. Accurate measurements of many factors that influence resistance evolution are difficult, if not impossible, to obtain experimentally. Thus, the use of models to predict times to resistance in specific situations is markedly limited. However, with appropriate assumptions, they can be invaluable in assessing the relative effectiveness of various management practices to avoid, or delay, the occurrence of herbicide resistance in weed populations.

Keywords

Gene mutationinitial frequencyselectionfitnessinheritancemating systemgene flowpopulation genetic models
Type
Special Topics
Information
Weed Science , Volume 44 , Issue 1 , March 1996 , pp. 176 - 193
Copyright
Copyright © 1996 by the Weed Science Society of America 

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References

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