Dissertation Research: Late-Acting Self-Incompatibility and Post-Pollination Selection in Milkweeds (Asclepias: Asclepiadaceae)

9623925怀亚特大多数开花植物是两性的，既产生雄性生殖器官，也产生雌性生殖器官。因此，自花授粉和异花授粉都是可能的。自花授粉的花通常比异花授粉的花不太可能结实。造成种子产量损失的机制包括遗传自交不亲和系统的作用和早期作用的近亲繁殖衰退的影响。区分这两种不育的原因很有挑战性，特别是对于表现出迟发性自交不亲和性或授粉后选择异交后代而不是自交后代的物种。这项由该奖项资助的研究利用实验杂交，在两种黄花(Asclepias)中解决了这些不同的机制。首先，实验将测试自交不育是由于早期作用的近亲繁殖抑制而导致的自交胚胎的流产，还是由于晚作用的自交不亲和而导致的自交受精卵的排斥。如果涉及到迟发性自交不亲和性，其遗传基础将被确定。其次，授粉后选择在自我繁殖的乳草中引起非随机交配的作用将被解决。这些研究将有助于阐明近亲繁殖、抑郁和自交不亲和在交配系统进化中的重要性。由于近亲繁殖衰退在应用农业系统和濒危植物种群中都是一个问题，了解缓解近亲繁殖的机制可以为作物改良和本土植物保护提供信息。

9623925 Wyatt Most flowering plants are hermaphroditic, producing both male and female reproductive organs. Consequently, self-pollination as well as cross-pollination is possible. Self-pollinated flowers often are less likely to set seed than cross-pollinated flowers. Mechanisms responsible for the loss of seed production include the action of genetic self-incompatibility systems and the effects of early-acting inbreeding depression. Distinguishing between these two causes of sterility is challenging, especially for species that exhibit either late-acting self-incompatibility or post- pollination selection of outcrossed offspring over selfed ones. The research funded by this award resolves these different mechanisms in two species of milkweeds (Asclepias), using experimental crosses. First, experiments will test whether self sterility results from either the abortion of selfed embryos due to early-acting inbreeding depression or the rejection of selfed zygotes based on late-acting self-incompatibility. If late-acting self-incompatibility is implicated, its genetic basis will be determined. Second, the role of post-pollination selection in causing non random mating in a self-fertile milkweed will be resolved. These studies will help to clarify the importance of inbreeding depression and self-incompatibility in mating system evolution. Because inbreeding depression is a problem in both applied agricultural systems and endangered plant populations, understanding mechanisms that alleviate inbreeding can inform efforts for crop improvement and native plant conservation.