Genetic variation in decay resistance and its correlation to wood density and growth in white spruce

This study investigated the genetic variation of white spruce (Picea glauca (Moench) Voss) in decay resistance and its correlation with wood density and growth. Three fungi were examined, a brown-rot fungus (Gloeophyllum trabeum), a white-rot fungus (Trametes versicolor), and a standing-tree-decay fungus (Fomitopsis pinicola). The decay resistance was inversely related to the growth rate of the fungi on heartwood blocks. A total of 270 trees of 35 families were harvested from 36-year-old provenance-progeny trials at two sites through a thinning operation. The narrow-sense heritabilities of white spruce decay resistance to brown rot and white rot were 0.21 and 0.27, respectively. There were no significant differences in resistance to standing-tree-decay fungus among the families. The phenotypic and genetic correlations between the growth rate of brown rot on heartwood blocks and wood density were positive, but the genetic correlation between wood density and the growth rate of white rot on heartwood blocks was negative but not significant. The results indicate that the different species of fungi have different relationships with the annual growth of trees and wood density, and suggest that selection for wood density in white spruce might lead to an increase in resistance to white rot, but a decrease in resistance to brown rot.