Levels of Outcrossing and Contamination in Two Pinus sylvestris L. Seed Orchards in Northern Sweden

The joint levels of outcrossing and contamination in two young northern Swedish Scots pine (Pinus sylvestris L.) seed orchards were studied with the aid of allozyme markers. High levels of contamination (21-36%) were estimated and were attributed to the observed low within orchard pollen production. Outcrossing rate estimates were high (0.957-0.961), though they departed significantly from complete outcrossing (t=1.0) in spite of the observed high contamination levels. These results confirmed reported relationships between outcrossing and contamination levels in open-pollinated seed orchards. It was concluded that a crop management option relying on supplemental mass-pollination would be effective in reducing both contamination and inbreeding levels.