INBREEDING DEPRESSION AND DOMINANCE SUPPRESSION COMPETITION AFTER INBREEDING IN RAPESEED (BRASSICA-NAPUS)

Rapeseed plants, of the summer annual variety Topas, that had been sel fed twice consecutively were compared to outcrossed half-sibs for inbr eeding depression in a rapeseed population at mating equilibrium. The effect of dominance-suppression competition was included in the effect of inbreeding. Both female- and male-fitness characters showed signif icant inbreeding depression. Biomass decreased 17% with inbreeding and was highly correlated with seed weight. The total number of flowers d ecreased 15% with inbreeding. There was a significant effect of lines. The possible importance of experimental design in studies that estima te inbreeding depression is discussed.