Tree breeding is a key element of the plantation forestry and the national forest seed procurement aimed at guaranteeing a supply of seeds with inherited high-quality and diverse characteristics for forest regeneration. The tree species cultivated in Finland include Scots pine, Norway spruce, silver birch, hybrid aspen, black alder and Siberian larch.
Tree breeding creates new growth
Bioeconomy demands increasing but sustainable utilisation of forest resources. One efficient way to respond to this challenge takes place in the course of forest regeneration as the main part of the regeneration area of Finnish forests, some hundred thousand hectares, is cultivated either by planting or direct seeding. The use of genetically improved reforestation material in is an easy and effective way to enhance the timber production capability of a new forest. The improved hardiness, quality and yield of this material provides added value to both the forest owner and the forestry sector.
Tree breeding was started with the selection of thousands of tree specimens with particularly good growth and high quality characteristics growing in natural stands. These so called plus trees were multiplied by means of grafting and planted in hundreds of hectares of seed orchards. In seed orchards, the grafts of plus trees hybridise freely with each other through wind pollination producing genetically improved seed for use in artificial reforestation. The orchard seeds contain coincidental combinations of tens of excellent parent trees. Exactly the same combinations could emerge in nature as well, but the likelihood of that happening is nearly non-existent. The introduction of plus trees from large areas to the same orchard greatly increases the probability of the enrichment of the most beneficial genes in the reforestation stock.
For the time being, sexual propagation by means of seed orchards has been the only method to transfer the genetic gains from tree breeding into large-scale practice. Currently three quarters of the conifer seedlings produced for forestry purposes in Finland are grown from orchard seeds. Alongside this method, a quicker and more efficient method is under development for spruce. It would enable to produce seedlings from seed embryos by means of the cultivation of vegetative plant cells.
The long-term breeding programme steers the implementation
Tree breeding is a long, continuous process. Genes that have a beneficial impact on desirable traits are enriched in every tree generation by means of alternating practices, selection, recombination, and testing. Compared to other cultivated plants, the pace at which tree breeding progresses is much slower due to the long duration between generations. In addition, verification of the inherited differences manifesting themselves in the yield, quality and hardiness traits through field testing takes significantly more time (10–20 years) than with other plants.
The implementation of this long-term process is steered by the breeding programme. The programme determines the means used to ensure the steady accumulation of genetic gains while maintaining genetic diversity at a sufficient level over many generations of breeding.
Role of the Natural Resources Institute of Finland
The Natural Resources Institute of Finland is responsible for the provision of tree breeding as a public service, to serve the needs of forest owners, producers of genetically improved seeds, and the forestry sector in general.
Picture on top of the page: Erkki Oksanen, Luke