Impact of selection and breeding on the genetic diversity in Douglas-fir

Abstract

Genetic changes following domestication of Douglas-fir were studied using isozyme data derived from two generations of seed orchards and their 49 wild progenitor populations. In addition, the breeding, production, and infusion populations used in the seed orchards were compared to their wild counterparts. Several parameters of gene diversity were measured (number of alleles per locus N a, per cent of polymorphic loci PLP, and expected heterozygosity H, and population divergence D). These measures were similar or higher in the domesticated populations compared to their natural progenitors, indicating that early selection and breeding of a highly polymorphic species does not significantly reduce genetic variation. The two generations of seed orchards also did not differ, indicating that genetic variation may remain stable over future generations of forest plantations. Interestingly, compared to the natural populations, heterozygosity was higher in the seed orchards, probably due to pooling of widely distributed natural populations; however, rare localized or private alleles seemed to be less frequent in the domesticated populations. Differentiation values were not significant between the first generation orchards and the natural populations, but significant differences were observed between the second generation orchards and the wild progenitor populations, probably due to the interbreeding that forms the advanced generation seed orchards.

Genetic variability of Scots pine maternal populations and their progenies

“…The genetic and life history characteristics of forest trees result in populations, which are robust and resilient to genetic change. Consequently, many studies have found that artificial selection, breeding, and silviculture have had minor genetic effects on most tree species (Yazdani et al 198, Muona et al 1987, El-Kassaby and Ritland 1996, Savolainen 2000, Wellman et al 2003. Despite similar levels of genetic diversity reported in this study, differences in the distribution of alleles between maternal and progeny populations were observed (Table 4), mainly among rare alleles with frequencies ranging from 0.00 to 0.036.…”

Pollination dynamics variation in a Douglas-fir seed orchard as revealed by microsatellite analysis

“…Notably, the linear deployment concept also assumes that the gametic contribution is representative of the orchard's parental linear representation. Finally, irrespective of which breeding strategy is implemented or seed orchard design is used, the main goal of the tree improvement endeavour is to reach an ideal balance between genetic gain and genetic diversity (Chaisurisri and El-Kassaby 1994;El-Kassaby and Ritland 1996).…”

Genetic diversity and forest reproductive material - from seed source selection to planting

“…The above results indicate that phenotypic selection at the early stage of breeding of highly polymorphic species does not significantly reduce genetic variability, likely due to the sampling of trees for plantation establishment from widely distributed natural populations (El-Kassaby & Ritland 1996). These results are confirmed in more recent study for Picea glauca (Namroud et al 2012), where single-nucleotide polymorphisms (SNPs) were used to assess the potential impact of artificial selection for height growth on the genetic diversity.…”