AOBPreview originally published online on June 30, 2009
Annals of Botany 2009 104(4):747-756; doi:10.1093/aob/mcp152
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© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
Simulating the evolution of glyphosate resistance in grains farming in northern Australia
Primary Industries and Fisheries, Department of Employment, Economic Development and Innovation, PO Box 2282, Toowoomba, 4350, Queensland, Australia
* For correspondence. Email david.thornby{at}deedi.qld.gov.au
Received: 16 April 2009 Returned for revision: 7 May 2009 Accepted: 12 May 2009 Published electronically: 30 June 2009
Background and Aims: The evolution of resistance to herbicides is a substantial problem in contemporary agriculture. Solutions to this problem generally consist of the use of practices to control the resistant population once it evolves, and/or to institute preventative measures before populations become resistant. Herbicide resistance evolves in populations over years or decades, so predicting the effectiveness of preventative strategies in particular relies on computational modelling approaches. While models of herbicide resistance already exist, none deals with the complex regional variability in the northern Australian sub-tropical grains farming region. For this reason, a new computer model was developed.
Methods: The model consists of an age- and stage-structured population model of weeds, with an existing crop model used to simulate plant growth and competition, and extensions to the crop model added to simulate seed bank ecology and population genetics factors. Using awnless barnyard grass (Echinochloa colona) as a test case, the model was used to investigate the likely rate of evolution under conditions expected to produce high selection pressure.
Key Results: Simulating continuous summer fallows with glyphosate used as the only means of weed control resulted in predicted resistant weed populations after approx. 15 years. Validation of the model against the paddock history for the first real-world glyphosate-resistant awnless barnyard grass population shows that the model predicted resistance evolution to within a few years of the real situation.
Conclusions: This validation work shows that empirical validation of herbicide resistance models is problematic. However, the model simulates the complexities of sub-tropical grains farming in Australia well, and can be used to investigate, generate and improve glyphosate resistance prevention strategies.
Key words: Crop weeds, modelling, glyphosate, herbicide resistance, awnless barnyard grass, Echinochloa colona, population dynamics