The 2010 ASHS Annual Conference

<i>Coreopsis leavenworthii</i> and <i>Coreopsis tinctoria</i> are Florida State Wildflowers, and there is considerable interest in production and planting of their seeds.  Because of their progenitor-descent relationship, it has been a major concern over their potential to cross-pollinate and the possible effects of such interspecific hybridization on their progeny's growth, development, and reproduction.  In this study controlled crosses were produced between the two species to assess the potential effects of interspecific hybridization on their progeny.  In controlled pollinations, interspecific crosses produced more seeds than either maternal-parent species and the interspecific seeds germinated as well as either species, indicating full compatibility between the two species.  The effects of interspecific hybridization were assessed by comparing F₁ and F₂ generations against the parental generation in plant height, plant dry weight, days to flower, and seeds per flower head.  In plant height, both F₁ and F₂ generations were between the parents.  The plant dry weight of the F₁ generation was between the parents, but higher than the mid-parent value.  The F₂ generation plant dry weight appeared to be on a declining trend.  No significant differences in days to flower were observed among parents and the F₁ and F₂ generations.  Seed production of the F₁ and F₂ generations was significantly lower than the parents.  These results seem to indicate that interspecific hybridization between <i>C. leavenworthii</i> and <i>C. tinctoria</i> could result in severe outbreeding depression in reproduction, especially in seed production.