title: Response to low-dose herbicide selection in self-pollinated Avena fatua.
abstract: BACKGROUND
  When applied at the correct plant stage and dose, herbicides are highly toxic to plants. At reduced, low herbicide doses (below the recommended dose) plants can survive and display continuous and quantitative variation in dose-survival responses. Recurrent (directional) selection studies can reveal whether such a phenotypic variation in plant survival response to low herbicide dose is heritable and leads to herbicide resistance. In a common experimental garden study, we have subjected a susceptible population of self-pollinated hexaploid Avena fatua to low-dose recurrent selection with the ACCase-inhibiting herbicide diclofop-methyl for three consecutive generations.
  
  
  RESULTS
  Significant differences in response to low-dose diclofop-methyl selection were observed between the selected progenies and parent plants, with a twofold diclofop-methyl resistance and cross-resistance to ALS-inhibiting herbicides. Thus, the capacity of self-pollinated A. fatua to respond to low-dose herbicide selection is marginal, and it is much lower than in cross-pollinated L. rigidum. Lolium rigidum in the same experiment evolved 40-fold diclofop-methyl resistance by progressive enrichment of quantitative resistance-endowing traits.
  
  
  CONCLUSIONS
  Cross-pollination rate, genetic variation and ploidy levels are identified as possible drivers affecting the contrasting capacity of Avena versus Lolium plants to respond to herbicide selection and the subsequent likelihood of resistance evolution at low herbicide dose usage.
authors.affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, The University of Western Australia, Crawley, WA, Australia.
authors.forename: Roberto
authors.initials: R
authors.lastname: Busi
authors.affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, The University of Western Australia, Crawley, WA, Australia.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Girotto
authors.affiliation: Australian Herbicide Resistance Initiative, School of Plant Biology, The University of Western Australia, Crawley, WA, Australia.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Powles
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors*; D018554:Avena / Q000187:drug effects / Q000235:genetics*; D014644:Genetic Variation; D055768:Halogenated Diphenyl Ethers / Q000494:pharmacology*; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology*; D054817:Pollination
chemical_list: D055768:Halogenated Diphenyl Ethers; D006540:Herbicides; C012891:dichlorfop-methyl; D000103:Acetyl-CoA Carboxylase
keywords: cross-pollination; experimental evolution; herbicide resistance; low dose; reproductive system; self-pollination