Some causes of variation in the proportion of selfed seed present in F1 hybrid seed lots of Brussels sprouts

Summary A series of field experiments on F₁ hybrid seed production was performed, using two parent inbred lines known to have incomplete self-incompatibility and thus to be susceptible to the production of some selfed seed. The experiments compared different ratios of plants of the two parents, different sub-lines, plant sizes and pollinating agents; and showed that all these treatments could cause changes in the ratio of selfed seed to crossed seed produced. The results are discussed in relation to the search for a mathematical model to express the basic factors likely to determine the rate of selfing in an F₁ hybrid seed production situation.