IUFRO Breeding theory and progeny testing

Main native species: Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.)

Most important hardwood: Birch (Betula pendula Roth, Betula pubescens Ehrh.)

Introduced in the 1970s: Lodgepole pine (Pinus contorta Douglas ex Loudon)

The first societies for forest tree breeding in Sweden were founded in 1936 (for South Sweden) and 1941 (for North Sweden), merging in 1959 and later evolving in to the present tree breeding branch of Skogforsk. Much of the initial efforts were spent on hardwood and ideas picked up from agricultural experiences. The reorganization in 1967 into a national forest tree breeding institute was more directed towards conifer breeding. The first basic plus-tree selections were carried out in the period 1940-1960 in mature wild forests.

Around 1970, most of the partial diallel crossing-plans designed for the initial set of native conifer seed orchards (at age around 10-15) were fulfilled. Now there was a need for more efficient progeny testing, and new, improved establishment techniques were employed. The first series of genetic tests with full-scale, thoroughly mapped single-tree plots were planted in 1971. In about 1975 it became a fact that the first-generation grafted seed orchards did work in practice for sustainable seed production. The earlier efforts were not in vain!

In the 1980s, results started to become available from numerous progeny tests of plus trees selected during the 1950s and 1960s. It wass verified that breeding works! These plus trees in the seed orchards still produced most of the bred seed used in Sweden at the turn of the 20^th century. Encouraged by the results, the breeding base is now expanded by a new extended plus-tree selection in using improved criteria in even-aged young stands, with the basic aim to ensure long-term breeding being profitable. A second round of seed orchard establishment is initiated in order to secure future seed supplies.

After 1985 a process of assimilation of applicable genetic evaluation techniques from animal breeders is started. The development and adaptation for tree breeding is facilitated by the since then notably accelerated development of computing technology for everyday use.

In about 1990, the principles for sustainable long-term breeding and formulation of breeding programmes for the Swedish tree species are worked out. The main documents are presented at a meeting with the Nordic group for tree breeding in Edinburgh 1993. Around 1995 there is a verification of the breeding progress so far through mass-comparisons of currently available grown-up forests with standard vs. bred Scots pine. Considerable further progress is verified where the parent trees are selected by way of progeny testing.

At the birth of the 21^st century it was time to compile predictions of genetic gain in future improved seed orchards of Scots pine, lodgepole pine, Norway spruce and silver birch, and to forecast the performance of clone mixes of bred Norway spruce. In 2000 proper comparisons of standard vs. bred Scots pine in north Sweden were carried out and further verified by re-measurements in old progeny trials from the 1970s. The planning of a third round of seed orchard establishment in order to secure future seed supplies of superior seed, fully supported by Swedish forestry was done.

In 2005, better estimates of the breeding gain in production per unit area are made available and may be used in forestry planning on a national level. The establishment of a third round of seed orchard is realized as a Skogforsk commission by order of Swedish forest industry and landowners. International co-operation is started in order to develop improved genetic evaluation and breeding value calculation with Skogforsk in Sweden and the Australian Southern Tree Breeding Association as main parties.

Author: Tore Ericsson, Skogforsk, Box 3, SE-918 21 Sävar, Sweden.