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50 years of tree breeding – Field progeny – Scots pine

Plot design

Initially, 16 (4 x 4) plant plots designs with 3 replications had been used for Scots pine testing. This design was closely linked to the system of nursery production used for material to be planted in progeny tests (Faulkner, 1967 and see Chapter 6). Later during the 1970s, the design was modified to that in use for Sitka spruce. Row plots of 8 trees, 5 replications and 3 test-sites were then commonly used. Selection was always based on 6 or 10-year height and stem straightness; wood density is sufficiently high in Scots pine not to be considered as a selection criterion.

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Progeny testing

Progeny testing in Scots pine started a little earlier than in Sitka spruce, and by the end of the 1960s nearly 50 progeny tests comprising 16 series were established in the forest. These contained open-pollinated families collected either from the standing tree in the forest or from grafted parents in a clone bank, or from families derived from artificial pollination using pollen mixtures of known composition. A further 64 Scots pine half-sib progeny tests (19 series) were planted in the 1970s and 21 in the first four years of the 1980s (7 series). By spring 1984, the last progeny test to estimate the breeding values of parent plus-trees was planted. One or two full-sib progeny tests had been established during the half-sib testing phase and in 1987, 3 half-diallels were planted with the objective of investigating the relative importance of additive and non-additive genetic variance; data from these are not yet available.

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Breeding population

As progeny-test data were collected, a rudimentary breeding population was constructed based on height and stem straightness. The best of the breeding population at any given time was used as a production population upon which grafting of clones for new tested clonal seed orchards was based.

In 1997, a complete analysis of all Scots pine progeny tests designed to estimate breeding values was carried out and 226 plus trees were re-selected for any new breeding population envisaged in the future (Lee, 1997b). It is not expected that Scots pine breeding will continue past this first generation. It is uncertain where the relative emphasis in gain should be placed between height and stem straightness in the breeding of Scots pine. There is a slight negative correlation between the two traits (r = -0.3). In order to give flexibility for the future, three alternative breeding objectives were developed, each involving a population of 200 re-selections. Since there was found to be great overlap between the constituents of these populations it was decided to retain a single breeding population of 226 parents with which any of the 3 objectives could be pursued.

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What’s of interest

These pages review the work performed by the Forestry Commission and Forest Research on tree improvement following the 50th aniversary of its establishment which passed in 1998.The genetic background describes the scientific procedures of tree breeding and the technical terms used in the remaining pages.All species are referred to by their common name in English.

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