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Keywords:

  • conifers;
  • diplohaplontic life cycle;
  • embryo lethal system;
  • gametophytes;
  • inbreeding depression;
  • polyembryony;
  • programmed cell death;
  • selfing

Summary

  • • 
    Selective elimination of selfed embryos, or inbreeding depression, is shared among many members of the Pinaceae but it has not been fully characterized at the phenotypic level.
  • • 
    Here, two death pattern model hypotheses are tested using 10 621 Pinus taeda embryos sampled in two cohorts. Cones from a single pedigree based on selfed, outbred, parent–offspring and offspring–parent matings were destructively sampled weekly before, during and after fertilization.
  • • 
    Selfed embryo deaths adhered to two patterns over the course of development: death was linear with respect to days from fertilization; and a stage-specific death peak occurred during the early embryogeny stage. This death peak occurred from 23 to 36 d after fertilization in the 2004 cohort and from 27 to 34 d after fertilization in the 2006 cohort. Of those selfed embryos that died, 64–83% died at stages where a single dominant embryo was elongating inside the female gametophyte.
  • • 
    Additional genetic models are needed to account for the stage-specific death component of selfed P. taeda embryos.