Phenotypic assessment and quantitative genetic analysis of two Douglas-fir progeny tests
By Jaroslav Klápšte, Mari Suontama, Charlie Low, Toby Stovold, Mark Miller, Kane Fleet and Heidi Dungey, June 2017.
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Two Douglas-fir progeny trials planted in Kaingaroa and Gowan Hill in 1996 were assessed in 2007 and re-assessed in February 2017. These two progeny trials are also training populations in a genomic selection project for Douglas-fir. A portion of the selections made after the 2007 assessment at Gowan Hill were no longer acceptable in terms of tree form, especially for stem straightness. Therefore an additional re-assessment was proposed to update knowledge of the quality of trees at these sites.
Information on the heritability for DBH and stem straightness at both sites indicated that good genetic gains will be achieved for these traits. Selection for improved needle retention would be possible by indirect selection using DBH because of a high genetic correlation between these two traits. Generally, genetic correlations between DBH and tree form indicated that selecting for tree growth does not result in improved tree form. Considerable differences among the performance of provenances were observed for all traits at both sites. Oregon and Washington provenances showed superior quality for an overall breeding goal compared with Californian provenances. Genotype by environment interaction was noticeable for DBH and stem straightness.
Application of genomic selection is expected to increase accuracy of selections from this population, which were highest at 0.65 for stem straightness at Gowan Hill using pedigree-based methods. Genetic correlations between traits at age 11 years and again at age 21 years indicated that age 11 year data are adequate for selecting the next generation of trees. Only a limited amount of additional information for genetic evaluation was obtained at age 21 years. However, this study, produced a considerable amount of new information for planning a Douglas-fir breeding strategy regarding early selection (age 11 years), genetic associations of selection criteria and provenance performances that can be utilised in future work.
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