Partial Suppression of Hair Development Indirectly Affecting Fruitfulness and the Proportion of Cross-Pollination in a Tomato Mutant

Abstract

A single recessive gene, dl, affects the development of epidermal hairs on stems, petioles, peduncles, and pedicels in the following manner the larger trichomes are reduced in size but not in number; the glandular hairs and the shorter trichomes are reduced both in size and number. The unicellular hairs that in the normal type bind anthers together to form the staminal tube are absent, permitting the anthers to diverge. Under field conditions dl dl plants yield only about 10% as many fruits as dl + and ++ plants, thus accounting for the discovery of this mutant. Artificial self-pollination restores normal fertility. The proportion of hybrid offspring indicates that nearly half of the seeds set by the dl type under open-pollination develop from outcrossing, whereas in the normal type outcrossing amounts to only 1 or 2%. Since seed production is greatly diminished, this increase in the proportion of hybrid offspring probably reflects a reduction in the amt. of self-pollination to a much greater extent than an increase in the amt. of cross-pollination. These changes in fertility relations of the mutant are attributed to the disruption of the normal mechanism for self-pollination wrought by the separation of anthers. Certain results can be explained if it is assumed that dl dl flowers set fruit only after pollen is transferred to them by insects.