title: Pollen-mediated transfer of herbicide resistance in Echinochloa crus-galli.
abstract: BACKGROUND
  Pollen-mediated gene flow (PMGF) can facilitate the dispersal and spread of herbicide resistance from one weed population to another within an agricultural landscape. The aim of this study was to quantify the extent of PMGF in Echinochloa crus-galli (barnyardgrass), an important herbicide-resistant weed species in the United States and across the world.
  
  
  RESULTS
  Gene flow declined exponentially with distance, and the double exponential decay model predicted an average gene flow of 5.6% when the pollen donor and recipient plants were at a close distance of 0.25 m from each other (12.5% at 0 m). Gene flow declined by 90% at 0.9 m from the pollen source, yet gene flow was detected as far as 50 m (the farthest distance studied). The farthest gene flow occurred in directions of the fastest wind events, but mean gene flow levels were similar among the directions.
  
  
  CONCLUSIONS
  Results indicate that long-distance, landscape-scale PMGF is unlikely in barnyardgrass, but gene flow is likely to occur between adjacent fields at levels greater than initial frequencies of resistance alleles in natural, unselected populations. Thus, any resistance management strategy should consider the likelihood that PMGF can contribute to the spread of herbicide resistance between production fields.
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, USA.
authors.forename: Muthukumar V
authors.initials: MV
authors.lastname: Bagavathiannan
authors.forename: Jason K
authors.initials: JK
authors.lastname: Norsworthy
mesh_terms: D018556:Crops, Agricultural; D031747:Echinochloa / Q000235:genetics*; D051456:Gene Flow; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides; D057685:Plant Weeds / Q000235:genetics*; D011058:Pollen / Q000235:genetics*; D014919:Wind
chemical_list: D006540:Herbicides
keywords: barnyardgrass; gene flow; herbicide resistance; outcrossing; pollen movement; resistance spread