Dissertation Research: Outcrossing Effects on Seed Development

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Plants produce many more ovules than develop into seeds. Some ovules may not develop into seeds because pollen tubes fail to reach the ovary and fertilize ovules; other ovules are fertilized and then aborted. The failure of an ovule to develop into a seed can also depend on the genotype of the pollen donor. In general, seeds sired by foreign pollen are more likely to be developed over seeds sired by self pollen when both types of seeds are competing in the same fruit. There have been few investigations attempting to determine the mechanism of preferential development of outcrossed seeds although many authors have hypothesized that variation in pollen tube growth is important. Pollen tubes of certain donors may simply not get to the ovary and fertilize any ovules. Patterns of preferential development could also be caused by selective abortion if seeds sired by self pollen are aborted with greater frequency than seeds sired by foreign pollen. Despite the possible role of seed abortion in determining patterns of preferential development, abortion of seeds sired by specific pollen donors has not been examined in any plant. The proposed work differs from previous studies because it will look at both variation in pollen tube growth and seed abortion. The PIs have developed a technique that enables them to determine the genetic makeup of ovules as they begin to abort. Preliminary data suggest that seeds sired by self pollen are aborted with greater frequency than seeds sired by foreign pollen.