Variation in sporophytic and gametophytic vigor in wild and cultivated varieties of Cucurbita pepo and their F1 and F2 generations |
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Authors: | M H Jóhannsson A G Stephenson |
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Institution: | (1) The Soil Conservation Service of Iceland, Gunnarsholt, 851 Hella, Iceland, IS;(2) Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA e-mail: as4@psu.edu Tel: +1-814-863-1553; Fax: +1-814-865-9131, US |
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Abstract: | This study examines sporophytic and gametophytic vigor in wild and cultivated varieties of Cucurbita pepo L. and their hybrids in order to determine whether hybrid vigor extends to the microgametophyte generation. It also examines
the variation in sporophytic and gametophytic vigor to discern the non-genetic influences of pollen provisioning by the sporophyte
on pollen performance from the genetic influences of the microgametophyte’s own genotype on pollen performance. A cultivated
and a wild C. pepo and their F1 and the F2 generations were grown under field conditions and flower and fruit production were monitored over
one summer. We found that the four types of plants differed significantly in the number of male and female flowers and the
number of fruits they produced. The F1 plants produced significantly more male flowers and marginally more female flowers
and fruits than the parental lines. To estimate gametophytic vigor pollen was germinated in vitro and pollen tube length measured
after 30 min. We found that pollen tubes from the F1 plants had significantly greater growth than tubes from the parental
lines or the F2 generation, indicating that hybrid vigor extends to the microgametophytic generation. By partitioning the
variance of pollen tube growth into ’within’ and ’among’ plant components of variation, we were able to show that the genotype
of the microgametophyte influences pollen performance in vitro, but that expression of hybrid vigor in the microgametophyte
is likely to be due to an environmental effect related to provisioning of the pollen grains during development.
Received: 16 April 1998 / Revision accepted: 18 August 1998 |
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Keywords: | Cucurbita Pollen tube growth Pollen performance Hybridization Variation |
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