The interactive effect of root disease and climate on wood properties in halfsibling Douglas-fir families

- Biotic and abiotic stressors affected wood properties in all trees and families.
- Increased in wood density was highest in infected families designated as disease resistant.
- Halfsibling families also had inherent wood properties regardless of infection status.
- Wood density may coincide with drought tolerance and disease resistance.
- Combining these traits could encourage adaptation to environmental variation.

Certain tree phenotypes enhance wood value properties and promote adaptation to climate extremes. However, the disciplines of wood science, physiology, and pathology rarely intersect to elucidate how survival, productivity, and wood property traits relate. Reaction to biotic and abiotic stress agents expressed in trees as disease resistance or tolerance were studied at the cell and tissue level. Five field-grown 21-22-year-old maternal halfsibling Douglas-fir Pseudotsuga menziesii var. glauca (Beissn.) Franco families were inoculated with Armillaria ostoyae (Romagn.) Herink to determine the interaction between disease, climate, and family on wood properties obtained from cores. The families originated from a lower elevation ecosystem and were categorized a priori as fungal disease resistant, tolerant or susceptible from a field study. Cell property changes suggestive of hydraulic adaptation to low precipitation were similar but lesser than the changes resulting from fungal root infection. The greatest increase in wood density occurred in disease resistant families after infection through a combination of thicker cell walls, smaller tracheid radial diameter, and reduced earlywood width. Microfibril angle and modulus of elasticity were affected differently with respect to changes in atmospheric relative humidity. Disease resistant compared to susceptible and tolerant families had inherent differences regardless of infection status. The sudden and localized changes in wood density associated with a disease resistance response could negatively impact on product quality, uniformity, and growth; on the other hand, denser wood and reduced growth associated with disease resistance may enhance drought survival. Understanding the interaction of these traits is important for adaptation to environmental stressors.