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，经常会脱落(败育)很大一部分果树。最近对常见和重要的饲料作物鸟脚三叶草的果实败育研究表明，这种植物不仅选择性地败育种子最少的果实，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，放置在花柱上的花粉粒数量各不相同。同样，那些种子最少的水果最有可能败育。此外，与种子较少的果实相比，种子最多的果实产生的后代萌发更快，幼苗更健壮，成年后花果产量更大。斯蒂芬森博士建议检验一种假设，即这些观察到的种子质量差异是由于种子所在花粉粒的遗传差异造成的。也就是说，当花粉管比卵子多时，只有最好的花粉父亲才能成熟种子。相反，当花粉管比卵子少时，好的和一般的花粉父亲都会成熟种子。因此，通过败育那些种子很少的果实(当花粉管比卵子少时产生的)，植物就会淘汰那些由平庸的花粉产生的后代，同时保留那些只有最好的花粉产生的果实。这些发现不仅应该对基础进化生物学和生态学产生深远的影响，而且还将对植物科学的应用领域具有重要意义。例如，仅用有限的空间就能快速筛选大量花粉粒以寻找农业上想要的特征，这对植物育种者来说是巨大的潜在收益。这样的筛选可能被证明比许多其他最先进的技术，如重组DNA和组织培养，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.