Maximizing gain per effort by using clonal replicates in genetic tests

Shaw, David; Hood, J V

doi:10.1007/bf00251178

Cited by 44 publications

(25 citation statements)

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“…The effect of clonal testing was more important than the inclusion of the multigeneration relationship data set to the genetic evaluation by BLUP. This supports the benefits of clonal assessment in progeny testing for forest tree breeding programs described by other authors (e.g., Shaw and Hood 1985;Russell and LooDinkins 1993;Mullin and Park 1994;Danusevicius and Lindgren 2002;Isik et al 2003).…”

Section: Resultssupporting

confidence: 86%

Positive Assortative Mating With Family Size as a Function of Predicted Parental Breeding Values

et al. 2005

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While other investigations have described benefits of positive assortative mating (PAM) for forest tree breeding, the allocation of resources among mates in these studies was either equal or varied, using schemes corresponding only to parental rank (i.e., more resources invested in higher-ranking parents). In this simulation study, family sizes were proportional to predicted midparent BLUP values. The distribution of midparent BLUP values was standardized by a constant, which was varied to study the range of distributions of family size. Redistributing progenies from lower-to higher-ranking families to a point where an equal number of progenies were still selected out of each family to the next generation caused minimal change in group coancestry and inbreeding in the breeding population (BP), while the additive genetic response and variance in the BP were both greatly enhanced. This generated additional genetic gains for forest plantations by selecting more superior genotypes from the BP (compared to PAM with equal family sizes) for production of improved regeneration materials. These conclusions were verified for a range of heritability under a polygenic model and under a mixed-inheritance model with a QTL contributing to the trait variation. E ARLIER studies by computer simulation have demonstrated that positive assortative mating (PAM) applied in a long-term forest tree breeding program has the potential to generate extra genetic improvement in forest plantations (e.g., dissertations by Mahalovich 1990; Rosvall 1999). This is due to the enhancement of the additive genetic response and variance in the breeding population (BP), enabling the selection of more extreme genotypes from the BP. These genotypes can be established in orchards to produce seeds for production of reforestation nursery stock or alternatively can be vegetatively propagated and directly planted as clones. When both genetic gain and diversity are considered in a single selection criterion, PAM does not much alter the effective population size compared with that achieved under random mating, but increases the average inbreeding in the BP as a consequence of mating among more related individuals .Ideally, the contribution of individuals in the BP to the next generation should correlate with their breeding values (Lindgren 1986). Various weighting schemes have been proposed to assign mating frequencies to individuals in the BP. These are built on different assumptions about the distribution of breeding values and the function used to assign the corresponding mating frequencies Kang 1989;Wei and Lindgren 1995). Two approaches for controlling parental contributions during PAM were investigated by , using a stochastic model of a forest-tree breeding program. In the first approach, balanced mating (each individual involved in an equal number of combinations) was followed by unbalanced selection (more progenies selected from higher-ranking families and fewer from lower-ranking families). In the second, unbalanced mating (individuals of high...

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Section: Resultssupporting

confidence: 86%

Positive Assortative Mating With Family Size as a Function of Predicted Parental Breeding Values

et al. 2005

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“…In addition, using clonal replicates in progeny tests can improve the accuracy of selection for additive genetic merit (Shaw and Hood 1985;Shelbourne 1991), and thus act to increase gain for both breeding and production populations.…”

Section: Discussionmentioning

confidence: 99%

Additive and non-additive genetic parameters from clonally replicated and seedling progenies of Eucalyptus globulus

Silva¹,

Borralho²,

Potts

2003

Theor Appl Genet

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The first estimates of the importance of epistatic effects within Eucalyptus globulus were obtained from analysis of clonally replicated full-sib progeny tests grown in Portugal. Parents comprised diverse selections from the Portuguese landrace. Variance components were estimated for 4-year-old diameter growth and pilodyn penetration, an indirect measure of wood density, both key traits in the pulpwood breeding objective. The experimental components of variance were used to estimate heritabilities and proportions of the phenotypic variance due to dominance and epistasis. The additive variance was the only significant genetic component affecting either diameter or pilodyn. Estimates of the additive, dominance and epistatic effects accounted for 8-10%, 0-4% and 0.4% of the phenotypic variance in diameter, and for 11-17%, 0% and 5% of the phenotypic variance in pilodyn, respectively. A comparison of residual coefficients of variation within seedling and cloned progenies indicated that C effects within clones were not a serious source of random variability. Despite the test sites encompassing a diverse range of locations, no important genotype by environment interaction was detected. The results suggested that an improvement strategy combining both recurrent selection for additive genetic merit and clonal testing may be adequate for optimizing genetic gains from this genetic base.

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“…In addition, as discussed by KUMAR (2006), various simulation studies had indicated the advantages of cloning in the breeding population (SHAW and HOOD, 1985;JEFFERSON and WEAVER, 1997;ROSSVALL et al, 1998;DANUSEVICIUS and LINDGREN, 2002). These studies were followed by SHELBOURNE et al's (2007) empirical simulations.…”

Section: Influence and Experience From Other Programmesmentioning

confidence: 99%

A New Breeding Strategy for Pinus radiata in New Zealand and New South Wales

et al. 2009

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A new breeding strategy is presented for the Radiata Pine Breeding Company, a New Zealand based research consortium, that drives the breeding program for Pinus radiata for both the New Zealand and New South Wales based Australian forest plantation industry. The new strategy builds on the existing base for P. radiata, and on the last strategy review in 2000. The new strategy comprises a large open-pollinated (OP) Main Population (MP) with 500 female parents and two sublines (250 female parents per subline). The MP will be tested using alpha designs, single-tree plots and incomplete blocks to maximise efficiency. Each subline will be tested on four sites, geographically distant from the other subline. The MP will be managed in discrete generations. Selection of the next generation will be using a combination of backward and forward selection, but the strict control of inbreeding with identified lineage will rely on the development of parental reconstruction for OP progeny. There are alternatives to this, however, such as estimating the group coancestry and accepting some additional increase in inbreeding. This is a new and significant departure from previous breeding strategies for P. radiata in New Zealand. There will also be a single, small Elite Population (EP), tested 50% as progeny and 50% as clones. Twenty four parents will be tested each year as clones and 24 as seedling progeny with some overlap between the two. It is expected that the clonal population will capture the greatest gains in traits with low heritabilities, and the half-sib progeny will capture the greatest gains in traits with high heritabilities. The two sublines will be maintained in the EP, and breeding will be managed as a rolling front with trials established every year, while trials of the MP will be established every 10 years.

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Maximizing gain per effort by using clonal replicates in genetic tests

Cited by 44 publications

References 1 publication

Positive Assortative Mating With Family Size as a Function of Predicted Parental Breeding Values

Positive Assortative Mating With Family Size as a Function of Predicted Parental Breeding Values

Additive and non-additive genetic parameters from clonally replicated and seedling progenies of Eucalyptus globulus

A New Breeding Strategy for Pinus radiata in New Zealand and New South Wales

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