Within and among family variation of orchard and wild-stand progeny of interior spruce in British Columbia

A common garden study was conducted with seedlings of the interior spruce complex Picea glauca (Monch) Voss and Picea. engelmannii Parry and their hybrids], comparing seedling height growth using open-pollinated orchard families and wild-stand (WS) families from the same breeding zone. Phenotypic variances of three bulked orchard seedlots and three WS seedlots did not differ. Orchard seedlots had generally higher within-family variance components than WS families. To examine year-to-year variation in orchard seedlots, three seedlots, composed of the same 18 orchard families collected in three different years, were evaluated in the same common garden study. Family mean heights within the three crop years were statistically not different; however, large rank changes in family mean heights and family variances were observed. This study shows that orchard seed derived from breeding programs does not reduce phenotypic variability in commercial plantations. In spite of the moderate to high selection intensities applied to the selection of orchard parents, large amounts of phenotypic variation are maintained because of the lack of coancestry in the orchard pollen cloud and large temporal variation in mating success and fecundity of the various parents contributing to the crop.