Progress 07/01/06 to 07/01/11
Outputs
OUTPUTS: Objective 1 was to estimate potential genetic gains for direct measures of Douglas-fir wood stiffness (modulus of elasticity, MOE) and strength (modulus of rupture, MOR). We completed Objective 1 by measuring the stiffness of 25-year-old progeny test trees using static bending tests. Objective 2 was to determine which indirect measurements of MOE and MOR would be useful for improving wood stiffness in operational tree improvement programs, and to estimate the relative gain efficiencies of the various indirect measures tested. We completed Objective 2 by measuring bending MOE directly using lumber bending tests and indirectly using tools (HM200 and ST300) that can be used to measure acoustic velocity in logs (HM200) or standing trees (ST300). Acoustic MOEs in logs and standing trees were obtained from the acoustic velocities and green wood densities. We estimated genetic gains for bending MOE, and then estimated relative efficiencies (REs), which are the relative gains in bending MOE expected from indirect selection for correlated traits. These correlated traits included HM200 traits, ST300 traits, basic wood density of basal discs, and oven-dry density of logs estimated from lumber. In 2010, we initiated new work that addresses Objective 2 in progeny test trees of Douglas-fir and western hemlock aged 6 to 12 years. Objective 3 was to determine whether the wood properties of seed orchard parents can be used to predict the wood properties of their progeny. We completed Objective 3 by studying acoustic MOE in a clonal seed orchard of Douglas-fir. The main objectives of this study were to determine (1) whether the wood properties of seed orchard parents can be used to predict the wood properties of their progeny, and (2) whether clonal seed orchard trees can be used to reduce the costs of incorporating wood properties into breeding programs. Objective 4 was to identify molecular genetic markers that are associated with desirable wood properties. We addressed Objective 4 by assembling a consensus transcriptome from next-generation sequence data that consists of 25,002 unigenes and 102,623 singletons. We then identified 281,192 genetic markers (SNPs, or single nucleotide polymorphic markers) and constructed and tested an Illumina Infinium SNP genotyping array that can assay 8,769 SNPs. Our work has been disseminated in refereed publications, at the annual meeting at the Pacific Northwest Tree Improvement Research Cooperative (PNWTIRC), at other forestry research cooperative meetings, and through the Conifer Translational Genomics Network newsletter at the Dendrome webpage hosted by one of our collaborators at the University of California at Davis. PARTICIPANTS: Glenn T. Howe, Principal Investigator; Scott Kolpak, Research Coordinator; Jianbin Yu, Post-Doc; Keith Jayawickrama, Director of the Northwest Tree Improvement Cooperative; Terrance Ye, Quantitative Geneticist for the Northwest Tree Improvement Cooperative; David Briggs, Professor, University of Washington; David Neale, Professor, University of California at Davis; Brad St. Clair, USDA Forest Service, PNW Research Station; and David W. Cress, Olympic Resource Management. TARGET AUDIENCES: Douglas-fir and western hemlock tree breeders in public agencies and private industry. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Wood stiffness is the most important property of structural lumber. Because juvenile wood is less stiff than mature wood, the quality of Douglas-fir lumber may decline as rotation lengths decrease and proportionally more of the wood is derived from the juvenile core of the tree. Furthermore, because wood properties in conifers are often highly heritable and can be improved through selection and breeding, it may be valuable to incorporate wood stiffness into Douglas-fir breeding programs. Nonetheless, direct measures of wood stiffness are costly to obtain and require destructive sampling. Therefore, alternatives are needed to measure wood stiffness prior to harvest. Based on analyses of 25-year-old trees, we demonstrated that indirect and/or nondestructive methods of evaluating wood stiffness are useful in Douglas-fir breeding programs. We also developed methods for measuring wood stiffness on much younger trees (e.g., ages 6 to 12) of Douglas-fir and western hemlock. Furthermore, we developed molecular genetic markers to be used to increase the accuracy and efficiency of methods designed to improve Douglas-fir wood stiffness. For backward selection, we estimated genetic gains in bending MOE of 8.6% to 12.3%. Relative efficiencies (REs), the relative gains in bending MOE expected from indirect selection for correlated traits, were 78% to 93% for indirect selection using the HM200 tool, 57% to 58% using the ST300 tool, 38% using basic wood density, and 98% for the oven-dry density of logs estimated from lumber. These results demonstrate that the HM200 is an efficient tool for improving bending MOE, but gains will be lower using the ST300 on standing trees. Indirect selection on wood density should be used with caution because the RE was low and wood density was negatively correlated with growth (-0.49 to -0.73). Overall, we recommend that breeders measure and select for stress wave velocity to improve bending stiffness in Douglas-fir. Genetic gains can be increased by including wood density, but genetic selection for fewer or smaller knots will be ineffective. We also showed that these methods are effective in operational tree improvement programs. We measured acoustic velocity on 7,423 Douglas-fir trees drawn from 347 wind-pollinated families on 14 sites in four first-generation testing programs in Oregon. Families were measured on two or four sites at ages 23 to 41 years from seed using the Fakopp TreeSonic standing-tree tool. Across-site, individual-tree, narrow-sense heritabilities for acoustic velocity squared (AV2) ranged from 0.24 to 0.40 among first-generation programs, and across-site type B correlations for AV2 ranged from 0.85 to 0.95. AV2 was negatively correlated with HT in three programs (additive genetic correlation = 0.17 to -0.28), and negatively correlated with DBH (-0.12 to -0.46) and volume growth (-0.05 to -0.44) in all four programs. Selecting the top 10% of the families sampled based on AV2 gave predicted gains of 4.4% to 9.6% for AV2. Finally, our seed orchard research supports the hypothesis that seed orchard trees can be used to measure wood properties and select genotypes with superior wood stiffness.
Publications
- Jayawickrama, K.J.S., Ye, T.Z., and Howe, G.T. 2010. Heritabilities, intertrait genetic correlations, GxE interaction and predicted genetic gains for acoustic velocity in mid-rotation coastal Douglas-fir. Silvae Genet. 60(1):8-18.
- Vikram, V., Cherry, M.L., Briggs, D., Cress, D.W., Evans, R., and Howe, G.T. 2011. Stiffness of Douglas-fir lumber: Effects of wood properties and genetics. Can. J. For. Res. 41(6): 1160-1173.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Objective 1: We completed Objective 1 by measuring the stiffness of 25 year-old progeny test trees using static bending tests. The results from these studies were reported in Cherry et al. (2008) (Can. J. For. Res. 38: 2476-2486) and in Vikram et al. (in press) (see below). Objective 2: In 2010, we initiated new work that addresses Objective 2 in progeny test trees aged 6 to 12 years. We previously addressed Objective 2 in 25 year-old progeny test trees (see Vikram et al., in press, below), but information on much younger trees is also needed because selections in Douglas-fir breeding programs are often made on these much younger trees. Our first step is to determine which measurement tool and approach works best for estimating wood stiffness of standing trees. We are doing this by examining phenotypic correlations between indirect measures of wood stiffness on standing trees versus more accurate and precise measurements made on logs using the Hitman 200 acoustic measuring tool. We have already estimated standing tree stiffness in two plantations of Douglas-fir and western hemlock using 4 tools available from Fakopp Enterprise: (1) TreeSonic with standard sensors; (2) TreeSonic with smaller SD-02 sensors; (3) Microsecond Timer with SD-02 sensors; and (4) Ultrasonic Timer with SD-02 sensors. In addition to testing these 4 tools, we are also testing the effect of placing the sensors on the same side versus the opposite side of the tree, and the effect of spanning versus not spanning a whorl of branches. Once we determine the best measurement approach from this experiment, this approach will be used to estimate genetic parameters, heritabilities, and genetic gains for wood stiffness in young progeny test trees. These analyses will be used to determine whether indirect and/or nondestructive methods of evaluating wood strength will be useful in young progeny tests. Objective 4: During the past year, we completed the analysis of next-generation sequencing data obtained from 454 and Illumina sequencing of Douglas-fir mRNA. We assembled a consensus transcriptome from these data that consists of 25,002 unigenes and 102,623 singletons, and then identified 14,506 putative SNP (single nucleotide polymorphic) markers that were identified in each of the 4 independent data sets we analyzed. We will select a subset of these markers (e.g., 1536 SNPs) to construct a SNP genotyping chip. Our work has been disseminated to the academic and industrial communities through the Conifer Translational Genomics Network newsletter at the Dendrome webpage hosted by our collaborator at the University of California at Davis. Updated information is also provided at the Pacific Northwest Tree Improvement Research Cooperative (PNWTIRC) annual meeting and newsletter that is distributed to the PNWTIRC members. PARTICIPANTS: Glenn T. Howe, Principal Investigator; Scott Kolpak, Research Coordinator; Jianbin Yu, Post-Doc; David Briggs, Professor, University of Washington; David Neale, Professor, University of California at Davis; Brad St. Clair, USDA Forest Service, PNW Research Station; and David W. Cress, Olympic Resource Management. TARGET AUDIENCES: Douglas-fir tree breeders in public agencies and private industry. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Wood stiffness is the most important property of structural lumber. Because juvenile wood is less stiff than mature wood, the quality of Douglas-fir lumber may decline as rotation lengths decrease and proportionally more of the wood is derived from the juvenile core of the tree. Furthermore, because wood properties in conifers are often highly heritable and can be improved through selection and breeding, it may be valuable to incorporate wood stiffness into Douglas-fir breeding programs. Nonetheless, direct measures of wood stiffness are costly to obtain and require destructive sampling. Therefore, alternatives are needed to measure wood stiffness prior to harvest. Based on analyses of 25 year-old tree, we demonstrated that indirect and/or nondestructive methods of evaluating wood stiffness are useful in Douglas-fir breeding programs. We are now developing methods suitable for much younger trees (e.g., ages 6 to 12) Furthermore, we are developing molecular genetic markers to be used to increase the accuracy and efficiency of methods designed to improve Douglas-fir wood stiffness.
Publications
- Vikram, V., M.L. Cherry, D. Briggs, D.W. Cress, R. Evans and G.T. Howe. 2011. Stiffness of Douglas-fir lumber: effects of wood properties and genetics. Can. J. For. Res. (In Press).
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Graduate student Vikas Vikram complete his Master of Science in Forest Sciences on January 2009. The thesis project focused intensively on objectives 1 through 3. Based on our findings we have expanded our work on objectives 3 and 4. Another set of parental clones and progeny were evaluated for wood stiffness at the BLM's Lorane breeding unit at the Travis Tyrell Seed Orchard (Tyrell SO) and two progeny sites. Acoustic velocity was measured on standing trees using the Fakopp TreeSonic tool and on logs (after felling and processing) using the HM200. The TreeSonic device is similar in design to the ST300 (i.e., measuring the time-of-flight of sound waves traveling between two pins), but it is more rugged, reliable, and has a more user-friendly interface. TreeSonic measurements were recorded on 167 parents (528 trees) in two BLM seed orchards prior to harvesting. HM200 measurements were taken on logs from 407 trees of the same clones after the trees were harvested. Foliage was collected for upcoming DNA extractions and eventual genotyping. In addition, HM200 measurements were taken during the thinning of two first-generation progeny test sites representing BLM's Lorane breeding program. These tests include progeny (families) of 167 parents that were measured in the seed orchards: 437 progeny from 114 parents were measured at the Carpentar Bypass site, and 427 progeny from 119 parents were measured at Hawley Creek. Finally, stiffness measurements began on a second set of clones and progeny from BLM's breeding unit 33 (BU-33). We began taking TreeSonic measurements on 160 parents at BLM's Horning Seed Orchard, and measurements were completed on the progeny of 131 parents at two first-generation progeny test sites. We developed a menu-driven Java program for simulating tree phenotypes and SNP haplotypes. This program will be used to: (1) test alternative mating designs, field designs, and sampling strategies for QTL discovery; and (2) evaluate alternative analytical approaches, including genomic selection. In the near term, this program will guide decisions on the 2,500 Douglas-fir trees to genotype. Our work has been disseminated to the academic and industrial communities through the Conifer Translational Genomics Network newsletter at the Dendrome webpage hosted by our collaborator at the University of California at Davis. Updated information is also provided at the Pacific Northwest Tree Improvement Research Cooperative (PNWTIRC) annual meeting and newsletter that is distributed to the PNWTIRC members. PARTICIPANTS: Glenn T. Howe, Principal Investigator; Scott Kolpak, Research Coordinator; Jianbin Yu, Post-Doc; David Briggs, Professor, University of Washington; David Neale, Professor, University of California at Davis; Brad St. Clair, USDA Forest Service, PNW Research Station; and David W. Cress, Olympic Resource Management. TARGET AUDIENCES: Douglas-fir tree breeders in public agencies and private industry. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Wood stiffness is the most important property of structural lumber. Because juvenile wood is less stiff than mature wood, the quality of Douglas-fir lumber may decline as rotation lengths decrease and proportionally more of the wood is derived from the juvenile core of the tree. Furthermore, because wood properties in conifers are often highly heritable and can be improved through selection and breeding, it may be valuable to incorporate wood stiffness into Douglas-fir breeding programs. Nonetheless, direct measures of wood stiffness are costly to obtain and require destructive sampling. Therefore, alternatives are needed to measure wood stiffness prior to harvest. We demonstrated that indirect and/or nondestructive methods of evaluating wood stiffness are useful in Douglas-fir breeding programs. Furthermore, we are developing protocols and recommendations for using nondestructive test procedures and molecular genetic markers to improve Douglas-fir wood stiffness.
Publications
- Vikram, V. 2008. Stiffness of Douglas-fir lumber: Effects of wood properties and genetics. M.S. Thesis. Oregon State University, Corvallis. 78 p. Available from Scholars Archive database at Oregon State University.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: We are studying the genetics of Douglas-fir wood stiffness to determine if wood stiffness be genetically improved in Douglas-fir, whether acoustic tools be used to indirectly select for improved wood stiffness, and if molecular genetic markers be used to improve the efficiency of wood stiffness genetic improvement. This research is being conducted using a seed orchard and three associated Douglas-fir progeny tests. During seed orchard roguing, we measured the wood densities of disks taken from the base and top of every 17' butt log. Acoustic velocity was measured on logs using the Fibre-gen Director ST300 (ST300) and Director HM200 (HM200). Foliage was collected from all orchard trees for DNA isolation and candidate gene analysis. Prior to thinning the 25-year-old progeny tests, we measured diameter at breast height of all 130 families. Acoustic velocity was measured on a subset of 50 families (8 trees per family) at two of the test sites (Shine and Opsata) using the ST300. Data were also collected when the Shine and Watershed sites were thinned (50% removal). After felling and delimbing, we measured acoustic velocity with the HM200, collected a wood disk from the base of each log, and measured green wood density in the field. The wood disks were shipped to Corvallis, kiln-dried, and weighed again to obtain basic wood density. Acoustic modulus of elasticity (MOE) was estimated from the ST300 and HM200 acoustic velocities and green wood density. A subset of the logs from the Shine site (i.e., the trees measured with the ST300) were cut to 9' butt logs, shipped to Corvallis, milled into boards (1.5" x 3.5" x 7') using a portable WoodMizer sawmill, kiln-dried, and then used to directly measure wood stiffness via bending tests. During the past year, we isolated DNA from approximately 180 trees in the Hood Canal Seed Orchard, completed the development molecular genetic markers for wood property candidate genes, and genotyped the seed orchard parents. This work was done at the University of California, Davis in collaboration with Dr. David Neale. These wood property candidate genes play key roles in wood formation based on studies in loblolly pine. These genetic markers are single nucleotide polymorphisms (SNPs), which are single-letter changes in the DNA code that occur between different alleles (copies) of the same gene. We also completed quantitative genetic analyses and reported results during the past year. We demonstrated that genetic gains can be made in Douglas-fir wood stiffness, acoustic tools are valuable for assessing wood stiffness, there is only a modest genetic correlation between the density of basal wood disks and bending stiffness, clonal seed orchards (which are easily measured) can be used to assess wood quality in breeding programs, selection for increased growth will not adversely affect bending stiffness or acoustic velocity, selection for increased wood density will adversely affect growth, wood stiffness increases with increasing ring age, and wood stiffness was only weakly correlated with knots in these evenly-spaced progeny tests. PARTICIPANTS: Marilyn L. Cherry, Principal Investigator; Glenn T. Howe, Co-Principal Investigator; Vikas Vikram, Graduate Research Assistant; David Briggs, Professor, University of Washington; David Neale, Professor, University of California at Davis; Brad St. Clair, USDA Forest Service, PNW Research Station; and David W. Cress, Olympic Resource Management. TARGET AUDIENCES: Douglas-fir tree breeders in public agencies and private industry. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Wood stiffness is the most important property of structural lumber. Because juvenile wood is less stiff than mature wood, the quality of Douglas-fir lumber may decline as rotation lengths decrease and proportionally more of the wood is derived from the juvenile core of the tree. Furthermore, because wood properties in conifers are often highly heritable, and can be improved through selection and breeding, it may be valuable to incorporate wood stiffness into Douglas-fir breeding programs. Nonetheless, direct measures of wood stiffness are costly to obtain and require destructive sampling. Therefore, alternatives are needed to measure wood stiffness prior to harvest. We demonstrated that indirect and/or nondestructive methods of evaluating wood stiffness are useful in Douglas-fir breeding programs. Furthermore, we are developing protocols and recommendations for using nondestructive test procedures and molecular genetic markers to improve Douglas-fir wood stiffness.
Publications
- Cherry, M.L., V. Vikram, D. Briggs, D.W. Cress and G.T. Howe. 2008. Genetic variation in direct and indirect measures of wood stiffness in coastal Douglas-fir. Canadian Journal of Forest Research 38(9):2476-2486.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: We currently have two major research projects: (1) genetics of Douglas-fir wood stiffness and strength and (2) miniaturized seed orchards (MSOs). Our wood quality research combines a number of novel elements, including the evaluation of new acoustic tools that can be used to obtain indirect estimates of wood stiffness on standing trees and logs, comparisons of wood stiffness estimated indirectly from the acoustic tools with stiffness measured directly on lumber harvested from the same trees, evaluation of wood stiffness of seed orchard parents and their progeny growing in genetic test plantations, and discovery of genes associated with wood properties using genomic approaches. To accomplish these goals, we are collaborating with the Stand Management Cooperative at the University of Washington, scientists at the University of California at Davis, the Genetics Team at the USFS Pacific Northwest Research Station, and Olympic Resource Management. To date, we have determined that
gains can be made in wood stiffness. Acoustic tools are valuable for assessing wood quality, but basal wood density is not a good measure of bending stiffness. Clonal seed orchards, which are easily measured, can be used to assess wood quality in breeding programs. Selection for growth will not have adverse effects on bending stiffness or acoustic velocity, but will adversely affect wood density. Miniaturized seed orchards are orchards in which the trees are planted at close spacings in clonal rows, and then maintained at a height of only 2 to 4 m. We are undertaking experiments that are designed to help us develop methods for establishing and managing miniaturized seed orchards of Douglas-fir. Previous research demonstrated that male and female flowering can be stimulated on very young grafts using a combination of girdling and gibberellic acid. Because the treated trees had higher mortality than the untreated trees, the best approach would be to delay flower stimulation until the
grafts are 5 years old. Our largest MSO experiment is a long-term test of alternative MSO designs that was established at the Plum Creek Seed Orchard Complex in western Oregon. We completed the grafting for this experiment in 2004, and the trees should be large enough to begin testing crown management treatments as early as the summer of 2008. We also initiated a pruning study at the Roseburg Products Vaughn seed orchard in the spring of 2005. This experiment is designed to determine the best time to prune the crowns of MSO trees. Pruning is needed to keep the trees small, but is also expected to reduce the number of cones, thereby adversely affecting seed production. We hypothesize that the timing (season and frequency) of crown pruning can be physiologically optimized to maximize seed production. Eventually, we expect to test one or more of the best pruning treatments from this experiment at the Plum Creek MSO, in addition to other crown management treatments.
PARTICIPANTS: Marilyn N. Cherry, Principal Investigator; Glenn T. Howe, Co-Principal Investigator; Vikas Vikram, Graduate Research Assistant; David Briggs, Professor, University of Washington; Dave Neale, Professor, University of California at Davis; Brad St. Clair, USDA Forest Service, PNW Research Station; and Daniel W. Cress, Olympic Resource Management.
Impacts
The Pacific Northwest Tree Improvement Research Cooperative conducts genetics and breeding research in support of regional tree improvement programs. Our wood quality research will lead to ensuring Douglas-fir's niche in domestic and international timber markets by maintaining wood stiffness and strength. Our results will also assist the forest sector in cost-saving and increasing product value. We will identify wood properties that can be incorporated into breeding programs to improve wood stiffness and strength.
Publications
- Cherry, M.L., T.S. Anekonda, M.J. Albrecht and G.T. Howe. 2007. Flower stimulation in young miniaturized seed orchards of Douglas-fir (Pseudotsuga menziesii). Can. J. For. Res. 37:1-10.
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Progress 01/01/06 to 12/31/06
Outputs
To date, our work has mainly involved field and laboratory data collection. The seed orchard containing maternal parents of the study's progeny test material was rogued. During harvesting, we collected wood disks from the base and top of every 17' butt log, and measured wood specific gravity (SG) and counted annual rings of each disk. The acoustic modulus of elasticity (MOEa) of the 17' butt logs were measured using the Fibre-gen Director ST300 (ST300) and HM200 (HM200). Foliage was collected from all orchard trees for DNA isolation and candidate gene analysis. Prior to thinning the three progeny tests, we measured diameter at breast height (dbh25), stem form, and branching traits on the 25-year-old trees from all 129 families. MOEa was measured on standing trees on a subset of 50 families (8 trees per family) at two of the test sites (Shine and Opsata) using the ST300. After harvesting, tree heights on a subset of the remaining trees were measured at all three
progeny test sites. The Shine and Opsata progeny tests had been thinned during the fall, but data were collected at the time of harvesting only at the Shine site. Half of the trees at the Shine progeny test were felled by chainsaw, and the logs were skidded to a landing and processed by a Caterpillar 325B. After the logs were delimbed at the landing, acoustic velocities were measured with the HM200. Wood disks were collected from the base of every log, and SG, annual ring counts, and bark thicknesses were measured in the field. Wood disks were later shipped to Corvallis, kiln-dried, and weighed again. A subset of harvested trees from the Shine site (the same trees from which the ST300 measurements were taken) were cut to 9' butt logs and shipped to Corvallis for milling into lumber. A portable WoodMizer sawmill was used to mill each log into 1.5 in. x 3 in. x 7' boards. These boards were then kiln-dried at OSU, and are now being used to obtain direct measurements of wood stiffness.
Lumber stiffness testing includes bending tests, transverse vibration, and stress-wave timer studies. The Watershed progeny test was thinned in the spring using a Timberjack harvester. Trees were delimbed at the stump, laid on the ground, and HM200 measurements were taken. During the past year, we isolated DNA from approximately 180 trees in the Hood Canal Seed Orchard, and began developing molecular genetic markers for 19 wood property candidate genes. We are targeting these 19 genes because they play key roles in the formation of wood based on studies in loblolly pine. We are developing genetic markers called single nucleotide polymorphisms (SNPs), which are single-letter changes in the DNA code that occur between different alleles (copies) of the same gene. To date, we have identified 11 of our target genes in Douglas-fir, and have begun developing SNP markers for these genes. During the next year, we will continue developing the SNP markers, and then begin genotyping the parents.
As much of the test data has now been collected, our focus will be shifting to data analysis and reporting of results.
Impacts
Wood stiffness is the most important property of structural lumber. Because juvenile wood is less stiff than mature wood, the quality of Douglas-fir lumber may decline as rotation lengths decrease and proportionally more of the wood is derived from the juvenile core of the tree. Furthermore, because wood traits of coniferous species are often highly heritable, and can be improved through selection and breeding, it may be valuable to incorporate wood stiffness into Douglas-fir breeding programs. Nonetheless, direct measures of wood stiffness are costly and require destructive sampling. Therefore, alternatives to destructive testing are needed to measure wood stiffness prior to harvest. For these reasons, we are carrying out extensive research on the measurement, quantitative genetics, and molecular genetics of Douglas-fir wood stiffness and strength. This study will determine whether indirect and/or nondestructive methods of evaluating wood stiffness and strength will
be useful in genetic tests. Furthermore, we will develop protocols and recommendations for using nondestructive test procedures in tree improvement programs.
Publications
- No publications reported this period
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