non additive variance in p abies and its influence on tree breeding by johan weston l.
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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 c lonal test s suitable for a breeding strategy based on general combining ability ?

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non additive variance in p abies and its influence on tree breeding by johan weston
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?
overview of material methods
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
conclusions
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
half sib material
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

full sib material
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

test material
Test material

Hedge archive at Sävar

Rooting of cuttings in nursery

field tests
Field-tests

A newly established field-test (1991)

  • completerandomisation
  • single-tree plots
  • ca.2 cuttings / clone
  • post-blocking
statistics
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)
estimation of additive and non additive variation half sib clones
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)

estimation of non additive variance full sibs
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 )
hypothesis
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”
conclusions17
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
estimation of vna with half sib clones
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)
estimation of dominance and epistasis
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 )
litterature
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