Comparison of selection methods for optimizing genetic gain and gene diversity in a red pine (Pinus resinosa Ait.) seedling seed orchard

Abstract

Four selection methods, individual selection (IS), family selection (FS), family plus within-family selection (FWFS) and combined selection (CS), were used to estimate genetic gain [ E( g)] for stem volume and gene diversity ( GD) for ten theoretical selection intensities in a 108-family, 12-year-old red pine seedling seed orchard. Estimated genetic gain for stem volume ranged from 4.6% to 11.8% across all selection methods and intensities with CS consistently having the highest gains and FS the lowest for any given selection intensity. Genetic diversity ranged from 0.9797 to 0.9954 across all selection methods and intensities. Individual selection was the best selection method for retaining GD, especially at the higher selection intensities, while FWFS was more efficient at the lowest selection intensity. An optimization point, which maximized E( g) and GD relative to each other, was calculated for each selection method. In all cases the optimization point indicated that both E( g) and GD would be favorably high when optimized relative to each other. The implications for volume gain, genetic diversity and potential inbreeding in red pine, a species with inherently low levels of genetic variation, are discussed.

Estimation of genetic gain and diversity under various genetic thinning scenarios in a breeding seed orchard ofQuercus acutissima

“…To effectively utilize the breeding seed orchard as a seed orchard, strong selection intensity must be applied in order to produce seeds with high genetic gain, whereas the orchard size, the numbers of replication and their randomization patterns determine the quality of the progeny test and the genetic information required for improving selection precision (Barnes 1995;David et al 2003).…”

“…Accumulation of group coancestry means inbreeding in the next generation if successful gametes unite at random (Cockerham 1967;Lindgren & Mullin 1998). The group coancestry (Θ) of the breeding seed orchard, which describes the probability that two genes are identical by descent, was calculated based on the family representation David et al 2003).…”

“…To compare ΔG among the three thinning scenarios (see below), the thinning intensities were kept constant across all genetic thinning scenarios. The three thinning scenarios used were directed and applied as (Lindgren & Matheson 1986;David et al 2003;Kang et al 2007):…”

Genetic gain and diversity under different thinning scenarios in a breeding seed orchard of Quercus accutissima

“…Breeding seedling orchards (Barnes, 1995) represent a unique situation where both breeding and production populations are included in one location where progeny test evaluation and parental selections for seed production are done in a concurrent fashion. This model is ideal for the situation where resources are limited and/or the justification for a full traditional breeding-testing-selection cycle and seed production is difficult (Barnes, 1995;David et al, 2003).…”

Combining genetic gain and diversity under an individual selection method in a selected provenance of Eucalyptus cladocalyx

“…Among other factors, the genetic gain depends on selection intensity and heritability (a phenotypic variance ratio attributable to the genetic load of the individual) (Borrel, 2002). In addition, studies have shown the need to have a wide genetic basis (genetic diversity) for the long-term maintenance of the genetic gain in quantitative traits (Zheng, 1997;David et al, 2003;Kang et al, 2005). (Mora et al, 2007).…”