The weeds fight back: Individual-based simulation of evolution of polygenic resistance to herbicides

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7 Citations (Scopus)

Abstract

The management of weeds is often described in military terms, such as 'winning the war against weeds' or 'fighting the green invaders', with weeds described as a 'green menace' or 'alien invaders' and those trying to manage them as 'weed warriors'. Is this a war that the humans can win? Weeds are evolving to be resistant to the herbicides on which world agricultural production relies. The problem appears to be being exacerbated by the wide spread adoption of genetically modified herbicide resistant crops. Weeds are even becoming resistant to herbicides that were previously thought to be difficult to evolve resistance to, such as the world's most important herbicide: glyphosate. It is difficult to fully understand how weeds evolve resistance in field situations and thus determine optimal strategies for avoiding, minimising or delaying the development of resistance in these situations. To investigate these questions through realistic field trials would require huge experimental areas and long time frames - by the time the answers had been found, it is likely they might no longer be useful as the weeds could already be resistant. Simulation modelling provides a tool for predicting how resistance evolves in field situations and thus for finding optimal control strategies. In this paper, a modelling approach for predicting the possibility and rate of weeds developing polygenic resistance is presented. The approach taken is a stochastic individual-based approach that explicitly takes into account the fact that weed populations consist of individual organisms each of a particular genotype, and that some genotypes may be very rare or absent in a particular population. The overall model dynamics (illustrated in Figure 1) are discussed, followed by explanations of the way the model represents genotype and resistance status, and how it determines death or survival of individual plants, total seed set, and the genotype of new seeds. Two alternative approaches for representing populations and implementing simulation processes are described. One approach represents the population as a list of individuals' genotypes, and the other represents the population as a list of total numbers of individuals of each genotype. These approaches are then compared in terms of efficiency and usefulness. An example related to polygenic herbicide resistance is presented that deals with the question: does using lower herbicide doses in cropping systems leads to faster or slower rates of development of herbicide resistance in weeds? A description of how the polygenic herbicide resistance model was used to analyse this problem is provided, together with some preliminary results. The paper finishes with some concluding remarks including a list of possible future extensions and additions to the model that would increase the range of questions and situations to which the model could be applied. A list of interesting and important issues and questions that this model of polygenic herbicide resistance could be used to address in future is also provided.

Original languageEnglish
Title of host publication18th World IMACS Congress and MODSIM 2009 - International Congress on Modelling and Simulation
Subtitle of host publicationInterfacing Modelling and Simulation with Mathematical and Computational Sciences, Proceedings
EditorsR.S. Anderssen, R.D. Braddock, L.T.H. Newham
PublisherModelling and Simulation Society of Australia and New Zealand Inc. (MSSANZ)
Pages574-580
Number of pages7
ISBN (Electronic)9780975840078
Publication statusPublished - 2009
Event18th World IMACS Congress and International Congress on Modelling and Simulation: Interfacing Modelling and Simulation with Mathematical and Computational Sciences, MODSIM 2009 - Cairns, Australia
Duration: 13 Jul 200917 Jul 2009

Publication series

Name18th World IMACS Congress and MODSIM 2009 - International Congress on Modelling and Simulation: Interfacing Modelling and Simulation with Mathematical and Computational Sciences, Proceedings

Conference

Conference18th World IMACS Congress and International Congress on Modelling and Simulation: Interfacing Modelling and Simulation with Mathematical and Computational Sciences, MODSIM 2009
Country/TerritoryAustralia
CityCairns
Period13/07/0917/07/09

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