Patterns of Gene Flow between Crop and Wild Carrot, Daucus carota (Apiaceae) in the United States

PLoS One. 2016 Sep 7;11(9):e0161971. doi: 10.1371/journal.pone.0161971. eCollection 2016.

Abstract

Studies of gene flow between crops and their wild relatives have implications for both management practices for cultivation and understanding the risk of transgene escape. These types of studies may also yield insight into population dynamics and the evolutionary consequences of gene flow for wild relatives of crop species. Moreover, the comparison of genetic markers with different modes of inheritance, or transmission, such as those of the nuclear and chloroplast genomes, can inform the relative risk of transgene escape via pollen versus seed. Here we investigate patterns of gene flow between crop and wild carrot, Daucus carota (Apiaceae) in two regions of the United States. We employed 15 nuclear simple sequence repeat (SSR) markers and one polymorphic chloroplast marker. Further, we utilized both conventional population genetic metrics along with Shannon diversity indices as the latter have been proposed to be more sensitive to allele frequency changes and differentiation. We found that populations in both regions that were proximal to crop fields showed lower levels of differentiation to the crops than populations that were located farther away. We also found that Shannon measures were more sensitive to differences in both genetic diversity and differentiation in our study. Finally, we found indirect evidence of paternal transmission of chloroplast DNA and accompanying lower than expected levels of chloroplast genetic structure amongst populations as might be expected if chloroplast DNA genes flow through both seed and pollen. Our findings of substantial gene flow for both nuclear and chloroplast markers demonstrate the efficiency of both pollen and seed to transfer genetic information amongst populations of carrot.

MeSH terms

  • Crops, Agricultural / genetics*
  • DNA, Chloroplast / genetics
  • Daucus carota / genetics*
  • Gene Flow
  • Gene Frequency
  • Genetic Variation*
  • Genetics, Population
  • Microsatellite Repeats / genetics*
  • Plants, Genetically Modified
  • Seeds / genetics
  • United States

Substances

  • DNA, Chloroplast

Grants and funding

This work was supported by the United States Department of Agriculture—National Institute of Food and Agriculture Award 2014-33522-21826 to JRM; Nantucket Biodiversity Initiative Grant to AJR; and the W. Harry Feinstone Center for Genomic Research equipment support to JRM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.