Post-pollination hybridization barriers in <Emphasis Type="Italic">Nicotiana</Emphasis> section <Emphasis Type="Italic">Alatae</Emphasis> |
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Authors: | Christopher B Lee Lawrence E Page Bruce A McClure Timothy P Holtsford |
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Institution: | (1) Division of Biological Sciences, 247 Life Sciences Center, University of Missouri, Columbia, MO 65211, USA;(2) Department of Biochemistry, 212 Rebstock Hall, Washington University, St Louis, MO 63130, USA;(3) Division of Biochemistry, 240a Life Sciences Center, University of Missouri, Columbia, MO 65211, USA;(4) Division of Biological Sciences, 105 Tucker Hall, University of Missouri, Columbia, MO 65211, USA |
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Abstract: | Nicotiana section Alatae contains eight species with variable flower sizes and morphologies. Section members readily hybridize in the glasshouse,
but no hybrids have been observed in natural sympatric and parapatric populations. To investigate interspecific crossing relationships
with respect to mechanisms preventing hybridization, all members of section Alatae were intercrossed in a complete diallel. We found positive correlation between the pistil length of the pollen donor and
interspecific seed set relative to the conspecific cross. Pollen tube growth rate and pollen donor pistil length were positively
correlated as well. Furthermore, pollen from short-pistil members of section Alatae could only grow a maximum distance proportional to, but greater than, their own pistil lengths. Our results show that pollen
tube growth capacity (i.e., rate and distance), provides a hybridization barrier in long-pistil species × short-pistil species
crosses. We also found another hybridization barrier not specifically related to pollen tube growth capacity in short-pistil
species × long-pistil species. Taken together, these barriers can generally be described by a ‘pistil-length mismatch’ rule;
in section Alatae, pollen has the most success fertilizing ovules from species with pistil lengths similar to their own. This rule could contribute
to hybridization barriers in Section Alatae because the species display dramatically different pistil lengths.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Nicotiana Seed set Hybridization barriers Pollen tube growth rates Pistil length |
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