title: Interspecific reproductive barriers between sympatric populations of wild tomato species (Solanum section Lycopersicon).
abstract: OBJECTIVE
  Interspecific reproductive barriers (IRBs) often prevent hybridization between closely related species in sympatry. In the tomato clade (Solanum section Lycopersicon), interspecific interactions between natural sympatric populations have not been evaluated previously. In this study, we assessed IRBs between members of the tomato clade from nine sympatric sites in Peru.
  
  
  METHODS
  Coflowering was assessed at sympatric sites in Peru. Using previously collected seeds from sympatric sites in Peru, we evaluated premating prezygotic (floral morphology), postmating prezygotic (pollen-tube growth), and postzygotic barriers (fruit and seed development) between sympatric species in common gardens. Pollen-tube growth and seed development were examined in reciprocal crosses between sympatric species.
  
  
  RESULTS
  We confirmed coflowering of sympatric species at five sites in Peru. We found three types of postmating prezygotic IRBs during pollen-pistil interactions: (1) unilateral pollen-tube rejection between pistils of self-incompatible species and pollen of self-compatible species; (2) potential conspecific pollen precedence in a cross between two self-incompatible species; and (3) failure of pollen tubes to target ovules. In addition, we found strong postzygotic IRBs that prevented normal seed development in 11 interspecific crosses, resulting in seed-like structures containing globular embryos and aborted endosperm and, in some cases, overgrown endothelium. Viable seed and F1hybrid plants were recovered from three of 19 interspecific crosses.
  
  
  CONCLUSIONS
  We have identified diverse prezygotic and postzygotic IRBs that would prevent hybridization between sympatric wild tomato species, but interspecific hybridization is possible in a few cases.
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA.
authors.forename: You Soon
authors.initials: YS
authors.lastname: Baek
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA.
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Royer
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA.
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Broz
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Covey
authors.affiliation: Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Gloria
authors.initials: G
authors.lastname: López-Casado
authors.affiliation: Department of Horticulture and Crop Science, Ohio State University, Wooster, Ohio 44691, USA.
authors.forename: Reynaldo
authors.initials: R
authors.lastname: Nuñez
authors.affiliation: Quality and Nutrition Laboratory, Centro Internacional de la Papa, Perú Postal 1558, Lima, Peru.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Kear
authors.affiliation: Quality and Nutrition Laboratory, Centro Internacional de la Papa, Perú Postal 1558, Lima, Peru.
authors.forename: Merideth
authors.initials: M
authors.lastname: Bonierbale
authors.affiliation: Quality and Nutrition Laboratory, Centro Internacional de la Papa, Perú Postal 1558, Lima, Peru.
authors.forename: Matilde
authors.initials: M
authors.lastname: Orillo
authors.affiliation: Department of Horticulture and Crop Science, Ohio State University, Wooster, Ohio 44691, USA.|Department of Horticulture, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: Esther
authors.initials: E
authors.lastname: van der Knaap
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Stack
authors.affiliation: Department of Biochemistry, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
authors.forename: Bruce
authors.initials: B
authors.lastname: McClure
authors.affiliation: Department of Plant Sciences, University of California Davis, Davis, California 95616, USA.
authors.forename: Roger T
authors.initials: RT
authors.lastname: Chetelat
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA bedinger@colostate.edu.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Bedinger
mesh_terms: D035264:Flowers / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D005638:Fruit / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D005843:Geography; D006824:Hybridization, Genetic; D010568:Peru; D011058:Pollen / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D053205:Pollen Tube / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D054817:Pollination; D012098:Reproduction; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D060436:Self-Incompatibility in Flowering Plants; D032322:Solanum / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D061350:Sympatry
keywords: Solanum; interspecific reproductive barriers; interspecific seed development; pollen–pistil interactions; postzygotic barriers; prezygotic barriers; self-incompatibility; sympatry; unilateral incompatibility; wild tomato species