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UBC Theses and Dissertations

Genetic variation in drought and cold tolerance in selectively bred and natural populations of coastal Douglas-fir Nuhu, Judith


Coastal British Columbia is experiencing warmer temperatures and spring and fall frosts which are predicted to worsen and adversely disrupt local adaptation, especially in long-lived species. In this study, 43 full-sib coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) families selectively bred for faster growth, along with 3 natural seedlots, 3 BC orchards seedlots and 4 US orchard seedlots from Oregon and Washington, were studied in a common garden at the University of British Columbia, to examine phenotypic traits related to cold and drought hardiness. Drought tolerance was monitored using chlorophyll fluorescence and cold hardiness was studied using an artificial freezing method. Absolute and relative height growth increments were measured, and the dates of vegetative budflush and budset were recorded. Best linear unbiased predictors were estimated for analyzing genetic variation in growth and stress tolerance traits across the genetic materials represented in the study. For all studied traits, substantial phenotypic variation existed among the different seed sources. Narrow-sense heritabilities were calculated, and the relationships among traits were compared using Pearson's correlation coefficient. There was no correlation between the two stress tolerance traits; cold hardiness and drought tolerance. Absolute growth was positively correlated with drought tolerance in the full-sib families; however, the selectively bred families lost their growth advantage in the drought treatment. The natural seedlots tended to have greater fall cold hardiness than the families and orchard seedlots. Budset and budflush were positively correlated with each other and with growth. These findings have relevance in assisted gene flow policies as breeders attempt to match reforestation seedlots with future climates by selecting best-adapted families for BC climate-based seed transfer projects.

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