GENOTYPIC VARIATION FOR REPRODUCTIVE CHARACTERS, AND THE INFLUENCE OFPOLLEN-OVULE RATIO ON SELFING RATE IN RAPE SEED (BRASSICA-NAPUS)

The variance component for genotypic effects and covariable plant vigo r were estimated for pollen production, number of ovules, the weight o f the flower without anther sacs and pistil, and the gender of the who le plant, in the rape seed variety Topas. There was a significant effe ct of the genotype for all measured characters. We did not find any tr ade-off between the male and female functions. Small plants were relat ively more male-biased than large plants. The weight of the flower wit hout anther sacs or pistil was positively correlated with pollen produ ction. The selfing rates of the lines were positively correlated with the pollen-ovule ratio, suggesting that the selfing rate of individual plants is positively correlated with pollen-ovule ratio, thus support ing the ''mass-action'' model. It is proposed that the observed increa se in the population selfing rate during the flowering season for some species, including rape seed, can be caused by an overall decrease in male investment.