Run-Peng Wei, Dag Lindgren. (1991). Selection effects on diversity and genetic gain. Silva Fennica vol. 25 no. 4 article id 5461. https://doi.org/10.14214/sf.a15619

Keywords: tree breeding; phenotypic selection; truncation selection; combined index; in-breeding

Abstract | View details | Full text in PDF | Author Info

Four different methods of truncation selection were studied in a population consisting of a large number of unrelated full sib families of equal size: phenotype selection, family selection, within-family selection and combined index selection (optimal weighting of individual and family performance to get the best prediction of breeding value). Methods were developed for calculating diversity (”relative effective family number”) for the different selection methods. Numerical calculations were made for genetic gain and diversity. Model assumptions are additive gene control and normal distribution. Phenotypic was good at high heritabilities and between family at low heritabilities. Loss of diversity was strongly dependent on selection method and selection strength. Compared at the same diversity, genetic gain was lower for combined index compared to phenotypic. There is a need for methods combining the goals gain and diversity.

The PDF includes an abstract in Finnish.

Wei, E-mail: rw@mm.unknown
Lindgren, E-mail: dl@mm.unknown

Category : Research article

article id 689, category Research article

Erik W. Andersson, Kostas A. Spanos, Timothy J. Mullin, Dag Lindgren. (1998). Phenotypic selection compared to restricted combined index selection for many generations. Silva Fennica vol. 32 no. 2 article id 689. https://doi.org/10.14214/sf.689

Keywords: genetic diversity; heritability; status number; phenotypic selection; index selection

Abstract | View details | Full text in PDF | Author Info

A breeding population has been subjected to repeated selection and crossing by simulation. Unrestricted phenotypic selection and restricted combined index selection were compared at the same effective number for five generations. Results show that phenotypic selection often achieves the gain and diversity possible to achieve by combined index selection but the relative efficiency is different for different family sizes and heritabilities. When phenotypic selection was compared with restricted combined index method at low heritabilities, both methods performed almost equally in terms of gain at the same effective number in small family sizes, although in large families, phenotypic selection was less efficient. At high heritabilities phenotypic selection was as efficient as combined index selection. Phenotypic selection was more efficient in conserving additive variance than combined index selection over five generations compared at the same gain and effective number. The introduction of a dominance component to the total variance had little effect. An increased breeding population size by a factor of ten resulted in an increased additive gain by app. 15%. The conclusion is that even though combined index selection is superior in identifying and extracting the potential for breeding achievements, it is generally not performing better than mass selection when compared at the same effective population size in small families.

Andersson, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, S-901 83, Umeå, Sweden E-mail: erik.andersson@genfys.slu.se
Spanos, N.AG.RE.F.-Forest Research Institute, 57006 Vassilika, Thessaloniki, Greece E-mail: kas@nn.gr
Mullin, Genesis Forest Science Canada Inc., C.P. 64 Succursale Haute-Ville, Québec, QC G1R 4M8 Canada E-mail: tjm@nn.ca
Lindgren, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, S-901 83, Umeå, Sweden E-mail: dl@nn.se

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