Time of cross- and self-pollination affects the amount of self-seed set by partially self-incompatible plants of Brassica oleracea

Abstract

The relative ability of cross- and self-pollen to achieve fertilisation in Brassica was studied by making double pollinations using cross-pollen carrying a dominant seedling marker gene. With simultaneous self- and crosspollination 12–40% self-seed was set, but when cross-pollen was applied to the stigma four hours before self-pollen, only 2–4% self-seed was obtained. In two plants to which cross-pollen was applied at various time intervals after self-pollen there was a tendency for the percentage of self-seed to increase as the time interval increased. In a third plant this trend was not apparent, probably because of a greater degree of self-incompatibility. The competitive advantage of the first pollen to arrive on the stigma is discussed in relation to the strength of the self-incompatibility and the sib problem in F₁ hybrid brassicas.