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.
