Relationship of Seed Quality to Genetic Variation in Pollen

许多植物物种，包括许多经济上重要的物种，定期掉（流产）它们的大部分果实。最近对常见的重要饲料作物鸟足三叶草果实败育的研究表明，这种植物不仅选择性地使种子最少的果实败育，而且通过这样做，它提高了种子（后代）的平均质量。在另一项对普通西葫芦的研究中，放置在花柱头上的花粉粒的数量是不同的。同样，那些种子最少的果实最有可能流产。此外，与种子较少的果实相比，种子最多的果实产生的后代发芽更快，幼苗更旺盛，成年后的花和果实产量更高。斯蒂芬森博士建议检验这样一种假设，即这些观察到的种子质量差异是由于形成种子的花粉粒的遗传差异造成的。也就是说，当花粉管比卵多时，只有最好的花粉父亲成熟种子。相比之下，当花粉管比卵少时，好的和一般的花粉父亲都能成熟种子。因此，通过流产那些种子少（当花粉管少于卵时产生）的果实，植物消除了那些由平庸花粉所育的后代，而保留了仅由最好花粉所育的果实。这些发现不仅对基础进化生物学和生态学具有深远的意义，而且对植物科学的应用领域也具有重要意义。例如，能够在有限的空间内快速筛选大量花粉粒以获得农业上理想的性状，这对植物育种者来说代表着巨大的潜在收益。与重组DNA和组织培养等其他先进技术相比，这种筛选可能更便宜、更快速、更容易实施。

Many plant species, including numerous economically important ones, regularly shed (abort) a large portion of their fruit crop. Recent study of fruit abortion on the common and important forage crop, birdsfoot trefoil, shows that this plant not only selectively aborts those fruits with the fewest seeds but, by doing so, it improves the average quality of its seed (progeny). In another study of common zucchini squash, the number of pollen grains placed onto the stigmas of the flowers were varied. Again those fruits with the fewest seeds were the most likely to abort. Moreover, the fruits with the most seeds produced progeny that germinated more rapidly, were more vigorous as seedlings, and had greater flower and fruit production as adults than did the fruits with fewer seeds. Dr. Stephenson proposes to examine the hypothesis that these observed differences in seed quality are due to genetic differences in the pollen grains that fathered the seed. That is, when there are more pollen tubes than eggs, only the best pollen fathers mature seed. In contrast, when there are fewer pollen tubes than eggs, both the good and the mediocre pollen fathers mature seed. Therefore, by aborting those fruits with the few seeds (produced when there were fewer pollen tubes than eggs) the plants eliminate those progeny fathered by the mediocre pollen while retaining the fruits fathered only by the best pollen. These findings should not only far reaching implications for basic evolutionary biology and ecology but will also have significance for applied areas of plant science. For example, the ability to rapidly screen large numbers of pollen grains for agriculturally desirable traits, using only limited space, represents enormous potential gains for plant breeders. Such screening could prove to be less expensive, more rapid, and easier to implement than many of the other state-of-the-art techniques, such as recombinant DNA and tissue culture.