GreenWood Resources proposes to develop hybrid poplar growing stock of improved water-use efficiency using a strategy of species selection, inter-specific hybridization, and varietal selection. The proposed work will lead to an increase in the cost-efficiency of current sawlog production and future biomass production at GreenWood's Boardman Tree Farm. Improvement in the physiology of varietal water use efficiency will also lead to reductions in greenhouse gas emission. Moreover, growing stock of improved water use efficiency will enable short-rotation forestry as a renewable source of cellulosic energy feedstock on sites of marginal agricultural quality using low-input silviculture in targeted regions of the western United States. The water-use efficient hybrid poplar energy varieties developed in this project will initially be used in developing biomass feedstock plantation support for a local cellulosic bio-refinery. OBJECTIVES: The following three objectives will be fulfilled during Phase I. Each objective addresses technical questions needed for the design of the Phase II proposal. 1. Phenotyping the 2008 Hybrid Population for Water Use Efficiency - Measure the water use efficiency of clonal varieties grown in the Boardman 2011 Stage II trial under deficit irrigation. (Assessment based on d13C measurements.) Fulfilling this objective will identify varieties for the Phase II irrigation management trial that will confirm the efficacy of using d13C methodology to identify WUE plant materials. 2. Covariance Analysis and Design of Phase II Trial - Determine the covariance structure of d13C and standard agronomic selection criteria presently in usage. Fulfillment of Objective II will provide insight into the tradeoffs in improving both WUE and growth and yield that will be investigated further in a Phase II irrigation management trial. 3. Investigation of Segregation for WUE within Inter-specific Hybrid Families. Quantify the degree of d13C segregation within hybrid families bred from standard breeding stock and breeding stock adapted to arid environments. Fulfillment of this objective is critical to the design of a Phase II breeding experiment for enhanced WUE and yield. APPROACH: Existing inter-specific hybrid progeny and clonal evaluation field trials containing multiple taxa will be assessed for genetic variation in water-use efficiency as quantified using carbon isotope discrimination methodology. This data will be combined with standard agronomic evaluation criteria (e. g. growth in stem height and diameter) to develop a multiple trait selection model during Phase I. The efficacy of index selection will be tested during Phase II in an irrigation management field trial in assessing the potential of carbon isotope discrimination in developing improved WUE plantation varieties. Additionally, transgressive segregation will be studied during Phase I within progeny populations of three inter-specific hybrid taxa developed in species and subspecies believed to be adapted to arid conditions (P. deltoides ssp. deltoides x P. fremontii, P. deltoides ssp. deltoides x deltoides ssp. wislizeni, P. deltoides ssp. deltoides x P. simonii)
