NATURAL OUTCROSSING IN COMMON BUCKWHEAT

Common buckwheat is an obligate cross pollinating crop because of its sporophytic self-incompatibility system. Therefore a study to assess t he extent of natural outcrossing was undertaken for two years at Morde n and Portage la Prairie, Manitoba using the semi-dwarf character, whi ch is due to a homozygous genotype with regard to a single recessive g ene, as a marker. The semi-dwarf genotype was grown in 100 m rows runn ing in four directions at 90 degrees from a central 36 m(2) plot of a normal, tall variety. At maturity, seed samples were taken from the se mi-dwarf population at designated intervals. At least 200 F-1 seeds fr om each sample were grown in the greenhouse to the 3-4 leaf stage and the proportion of tall plants was used to determine the percentage of outcrossing. Approximately 50% outcrossing occurred where the semi-dwa rf plants were immediately next to the normal plants and then the prop ortion decreased with increasing distance. Although outcrossing occurr ed throughout the distance tested, there were no significant differenc es from 12 m onward from the pollen source. Lack of directional influe nce in outcrossing and a sharp reduction in the proportion of tall pla nts within a 3 m distance from the pollen source suggested that wind w as not a major factor in dispersing the buckwheat pollen over long dis tances. Although a substantial cross pollination was limited to a few metres from the pollen source, nearly 1% outcrossing occurred even at 100 m. Since the distance in this experiment was limited to 100 m from the pollen source, the present results do not allow us to recommend t he minimum isolation distance required to meet certain standards for b uckwheat seed production.