Non-additive variance in P. abies and its influence on tree breeding. By: Johan Weston

1. Non-additive variance in P. abies and its influence on tree breeding.By: Johan Weston • What is the level of additive & non-additive variance for early height growth in our clonal tests? • Are clonal tests suitable for a breeding strategy based on general combining ability? • Can we affect the level of non-additive variance?

2. Forestry Research InstituteSävar

3. Overview of Material & methods • Half-sib & full sib clones • Selection of ortets based on early height growth in the nursery • Clonal field-tests – 2 series, 10 tests • Complete randomisation, single tree plots • Assessment of height growth (10-11 yrs) • Estimation of variance components - ASReml

4. Conclusions • Overall, non-additive variance was substantial but smaller than additive variance • Non-additive variance was affected byclonal origin and test environment (”frost”) • Clonal tests are suitable in a breeding strategy based on general combining ability (GCA)- if non-additive variance is moderate • To increase trait heritability and selection accuracy a more distinct definition of the trait ”growth” is needed

5. Half-sib material Selected plustrees in natural stands and field tests ºN 68 66 64 62 60 58 56 • 2 clones selected in each family • clones divided insouthernand northern origins • 6 clonal field tests • assessment after 11 years Sävar

6. Full-sib material ºN 68 66 64 62 60 58 56 Selected plustrees in natural stands • partial diallel • 3-7 ortets selected in each family • 4 clonal field tests • assessment after 10 years Sävar

7. Test material Hedge archive at Sävar Rooting of cuttings in nursery

8. Field-tests A newly established field-test (1991) • completerandomisation • single-tree plots • ca.2 cuttings / clone • post-blocking

9. Statistics • ASReml [25 Jan 2001] • Model - half-sib clones Y= µ + Testsite + Block + (Fixed) Stand + Parent + Clone (Random) • Model - full-sib clones Y= µ + Testsite + Block + (Fixed) Parent + Fam + Clone (Random)

10. Estimation of additive and non-additive variation – half sib clones • Parent (mother) component of variance, σp2 • Clonal component of variance, σc2 • σA2 = 4σp2 • σNA2 = σc2 - 3σp2 • Stand component of variance, not included in σA2, a ”provenance” effect (Source: Snedden et al, 2000, In "Forest Genetics for the Next Millenium”, IUFRO 2.08.01)

11. Results half-sib clones

12. Half-sib clones - southern origins

13. Estimation of non-additive variance – full-sibs • Parent component of variance, GCA, σp2 • Family component of variance, SCA, σf2 • Clonal component of variance, σc2 • Additive variance, σA2 = 4σp2 • Total genetic variance, σG2 = 2σp2 + σf2 + σc2 • VNA= Total genetic variance – additive var. = σG2 - σA2(Source: Mullin et al, Can J For Res, 1992 )

14. Results full-sib clones

15. Full-sib clones

16. Hypothesis • NAV in height growth is influenced y genetic variation in other traits i.e. hardiness • Buds are more frost sensitive in genetic material with a long growth period • Genetic entries with a long growth period has a high growth potential • Occasional bud damages due to frost may be included in the trait ”height growth”

17. Conclusions • Overall, non-additive variance was substantial but smaller than additive variance • Non-additive variance was affected byclonal origin and test environment (”frost”) • Clonal tests are suitable in a breeding strategy based on general combining ability (GCA)- if non-additive variance is moderate • To increase trait heritability and selection accuracy a more distinct definition of the trait ”growth” is needed

18. Estimation of VNA with half-sib clones • Family component of the variance, σp2 = ¼ σA2 • Clonal component of the variance = total genetic variance minus the family component,σc2 = σG2 - σp2 • σc2 = (σA2 + σNA2) - σp2 σc2 = (σA2 + σNA2) - ¼ σA2σc2 = ¾ σA2 + kσNA)σc2 = ¾ σA2 + σNAk = proportion of non-additive variance segregating within families, k=1 in o.p. families (Park & Fowler, 1987) • σNA =σc2 - ¾ σA2σNA =σc2 - ¾ (4σp2 )σNA =σc2 – 3σp2 (Source: Snedden et al, 2000, In"Forest Genetics for the Next Millennium”, IUFRO 2.08.01)

19. Estimation of dominance and epistasis • Parent component of variance, GCA, σp2 • Family component of variance, SCA, σf2 • Clonal component of variance, σc2 • Dominance variance, σD2 = 4σf2 • Epistatic variance, σI2 = σc2 - 2σp2 - 3σf2 • Total genetic variance, σG2 = 2σp2 + σf2 + σc2 • NVA= Total genetic variance – additive var.(Source: Mullin et al, Can J For Res, 1992 )

20. Litterature • Snedden, C.L., Verryn, S.D. & Roux, C.Z. 2000, Broad- and narrow sense heritabilites in a cloned open pollinated Eucalyptus grandis breeding population, ProceedingsIn "Forest Genetics for the Next Millenium ”, IUFRO Working Party 2.08.01, Durban, South Africa, p 214-220. • Mboyi, W.M. & Lee S.J., 1999, Incidence of autumn frost damage and lamma growth in a 4-year-old clonal trial of Sitka spruce (Picea sitchensis) in Britain. Forestry vol 72, No 2 , 1999 • Mullin, T.J., Morgenstern, E.K., Park, Y.S & Fowler, D.P., 1992, Genetic parameters from a clonally replicated test of black spruce (Picea mariana), Can. J. For. Res. 22 : 24-36. • Mullin, T.J. & Park, Y.S. 1992, Genetic parameters and age-age correlations in a clonally replicated test of black spruce after 10 years, Can. J. For. Res. 24 : 2330-2341. • Samuel, C.J.A., 1991, The Estimation of Genetic Parameters for Growth and Stem-Form over 15 years in a Diallel Cross of Sitka Spruce, Silvae Genetica 40, 2. • Park, Y.S & Fowler, D.P., 1987, Genetic variances among clonally propagated populations of tamarack and the implications for clonal forestry, Can. J. For. Res. 17: 1175-1180