Exploring variation in transcriptional profiles and hydraulic architecture in hybrid poplar clones

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Plantations of fast-growing tree species are used around the world to meet the increasing demand for wood fiber. This strategyis also being developed in Canada, as the forest industrylooks to marginal farmlands, located close to mill sites, to establish hybrid poplar plantations as a new source of wood supply. Hybrids of parents from different poplar species are among the most productive trees and are widelyplanted in commercial plantations. Due to their superior growth characteristics, hybrid poplars are a valuable new source of pulp, solid-wood products, and energyfor the Canadian forest industry.Trees must be able to cope with environmental stress including drought. In western Canada, regional droughts have been linked with tree mortalityand reduced productivityin aspen forests. Drought periods are predicted toincrease in frequencyand severityin this region. There is a need for a detailed understanding of the water relations of commerciallygrown poplar genotypes. Since poplars tend to be sensitive to water supply, much work has focused on increasing their water use efficiencyand drought tolerance while retaining adequate productivityon various drought-prone sites and to utilize the existing land base efficientlywithout irrigation.Although hybrid poplars are highlyproductive as a group, individual clones show considerable differences in growth and stress tolerance. 'Stable' clones show acceptable growth performance over a wide range of growing conditions and sites. 'Variable' clones exhibit acceptable growth on some sites and poor performance on other sites. We will use a wide range of methods to studythe water relations and selected wood anatomical traits of stable versus variable clones. The proposed research takes advantage of various molecular and genomic tools tostudyhow physiological and developmental adjustments to different environmental conditions are underpinnedbyreconfiguration of the transcriptome. The findings from this work will be applied to tree breeding and plantation management programs. Developing a strong scientific basis for clone selection on different sites is a strategic investment into the economic success of the forest industry.