Abstract
BackgroundForest trees can occupy extensive geography and environmentally highly variable areas which result in high genetic variability in the direction of pressure from natural selection. At the same time, the majority of conifer species are wind-pollinated from both short and long distances, resulting in wide-spread gene flow, which can lead to maladaptation to local conditions. Quantitative analyses of provenance/progeny tests correct for genetic differences between populations to ensure unbiased genetic parameters are obtained. Commonly, the provenance effect is fitted as a fixed term or can be implemented as a contemporary group in the pedigree.ResultsThe use of a provenance effect, either as a fixed term or as the same contemporary groups in both maternal and paternal sides of the pedigree, resulted in fairly similar precision of genetic parameters in our case. However, when we developed a phantom contemporary group for the paternal side of the pedigree that considered a different genetic quality of pollen compared with the maternal contribution from trees in the local environment, the model fit and accuracy of breeding values increased.ConclusionConsideration of the mating dynamics and the vector of gene flow are important factors in modelling contemporary genetic groups, particularly when implementing pedigrees within a mixed model framework to obtain unbiased estimates of genetic parameters. This approach is especially important in traits involved in local adaptation.
Highlights
Forest trees can occupy extensive geography and environmentally highly variable areas which result in high genetic variability in the direction of pressure from natural selection
Forest tree breeding populations are mostly in the initial stage of domestication, and the history of evolutionary processes involved in local adaptation such as migration, genetic drift, mutations and selection greatly affect the results of any initial genetic evaluations
Our study found a positive impact on model fit and accuracy of breeding values from biologically relevant modelling of population structure through contemporary groups implemented in the pedigree
Summary
Forest trees can occupy extensive geography and environmentally highly variable areas which result in high genetic variability in the direction of pressure from natural selection. Forest tree species usually occupy large geographical areas and are exposed to a wide range of environmental conditions. These large geographical ranges predetermine large genetic changes along the environmental gradients, such as latitude or altitude, through natural selection. Forest tree breeding populations are mostly in the initial stage of domestication, and the history of evolutionary processes involved in local adaptation such as migration, genetic drift, mutations and selection greatly affect the results of any initial genetic evaluations. The geographical differences in these processes should be included in these evaluations through the inclusion of a provenance effect, fitted either as a fixed or random. Since geographical structure in populations of forest tree species is present [9], the non-random contribution of males should be considered. The assumption that the models must capture all factors contributing to the explanation of a phenotype’s variance to be considered close to the true model and obtain robust, unbiased estimates is often under question
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