Using bud pollinations to avoid self-incompatibility: implications from studies of three mustards

Abstract

Bud pollinations are frequently used to produce selfed progeny in species that have self-incompatible mature flowers. While this technique is useful for generating inbred lines of self-incompatible species, examining the effects of close inbreeding by producing selfed seeds from bud pollinations may potentially be confounded by the consequences of fertilizing immature ovules. We examined this issue in three species of self-incompatible mustards: Lesquerella fendleri, Brassica rapa, and Raphanus sativus. We performed three types of pollinations on five maternal plants of each species: bud self, bud outcross, and mature flower outcross. For Raphanus, we also planted the seeds produced by these crosses and compared their germination percentages and dry mass 6 weeks after planting. In all three species, outcrossed flowers produced significantly more seeds per fruit than either selfed or outcrossed buds. In each species there were no significant differences among the three crosses in mean individual seed mass per fruit. In Raphanus, the dry mass of plants grown from the selfed bud seeds was marginally less (p = 0.079) than that from seeds from the two outcrosses. As a whole, our results indicate that comparing progeny from mature flower pollinations with progeny from selfed buds can be misleading, particularly when comparing seeds per fruit. Keywords: bud pollination, inbreeding, self-incompatible, flower maturity, selfed seeds.