Delineation of breeding zones – Picea abies in Norway as an example




Дата канвертавання25.04.2016
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Delineation of breeding zones – Picea abies in Norway as an example
Tore Skrøppa

Norwegian Forest and Landscape institute


Background information
Norway spruce (Picea abies) is a young species in Norway and started its introduction into the Norwegian landscape approximately 2500 years ago. Its present natural occurrence is in south-eastern Norway from sea level and up to 1000 m, and in Central and North Norway, north to lat. 67, at decreasing altitudes in the north. Outside this area the species has been planted both in western Norway and north of its natural boundary in northern Norway.

Genetic information characterizing adaptation to the climatic conditions is available from provenance, progeny and clonal trials. Measurements have in particular been made of annual growth rhythm traits: the timing and duration of the annual growth period, frost hardiness development in the autumn and dehardening in the spring, and the occurrence of climatic damage under field conditions. All studies demonstrate a clinal variation in growth rhythm traits in natural populations from the south to the north and from low to high altitudes. The southern and lowland populations have the longest duration of the growth season, and as a consequence, the highest growth potential. They also have the latest development of autumn frost hardiness. The only well-known characterisations of the adaptive process of spruce populations are the responses to temperature and photoperiod. Within natural populations, a large genetic variation is present, also for traits that show clinal variation at the provenance level and in populations at the geographic margin of the species. In addition, a number of studies have shown that Norway spruce can adjust the performance in adaptive traits by a rapid and likely epigenetic mechanism, through a kind of a long-term memory of temperature sum and photoperiod during seed production.

Seed orchards were in the 1960s and 1970s established from plus-tree selections in natural forests and are now being renewed with tested materials. Now selection and testing of a second generation of parents has begun. In the revised breeding strategy the proposed breeding objectives are to improve climatic adaptation, growth and quality, without decreasing the genetic variation in future forests. The bred material should give a higher survival and be possible to use over a larger area then material from natural stands. The bred material should also be robust to future climatic changes. The increased growth should contribute to mitigate the effect of CO2 from the atmosphere. Breeding should not decrease, preferably increase, wood density, improve form stability and reduce the frequencies of defects that cause reduced value production.

Earlier most reproductive material of Norway spruce was of the category source indentified, collected in natural stands and characterized by its region of provenance (Figure 1). Transfers should not be made more than 200 km north or south and less than 300 m in altitude.


Breeding and deployment zones
In a revised breeding strategy Norway is divided into eight breeding zones (Table 1) based on, latitude, altitude, and known climatic gradients, both for administrative reasons and optimal use of adapted reproductive materials from the seed orchards. Breeding efforts and objectives differ between zones depending on whether there are specific issues in the wood production that have to be focused and also on the importance of forestry in the region. In each zone the breeding population is divided into one or more sub-populations each containing 50 unrelated individuals. Breeding zone G0 will contain one sub-population with individuals selected from more southern provenances adapted to climatic conditions corresponding to a 2º C increase in mean annual temperature in deployment zone G2 and G4. The other zones will contain sub-populations with individuals from a limited geographic area within the zone. Hence, the populations should then be adapted to the present climate in the zone, but may also be ranked according to climatic gradients within the zone. They should provide the basic material for reproductive material from seed orchards that could be used in a wide area, but also be flexible for transfer if climate change. All individuals in the sub-populations should be tested in progeny tests planted at several sites. The importance of traits in selection will vary among zones, but will generally characterise annual growth rhythm, height growth and wood quality traits. The timing of flushing in spring is a key trait in regions where spring frosts frequently occur and early flushing will be avoided. The recommendations for the deployment of reproductive material should be revised as more fields test information become available.

It is important to note that breeding and deployment zones are different and that there can be several deployment zones within each breeding zone. The deployment zones are defined by the adaptive properties of the seedlings from each seed orchard which have to be tested. Their performance will to some extent be influenced by the seed orchard locality due to both pollen contamination from surrounding forests and by epigenetic effects caused by the climatic conditions at the seed orchard site.

Table 1. Breeding zones and regions of deployment for Norway spruce in Norway. In each breeding zone there is one or more sub-populations each containing 50 unrelated individuals from a limited geographic area within the zone.


Breeding zone

Region of deployment

Altitude

Number of sub-populations

G0

Same as G1 and G4 with a 2º C increase in mean annual temperature

0 – 250 m

1


G1

Interior south-eastern Norway

Lat. 58º - 62º N



0 – 350 m

5

G2

Interior south-eastern Norway

Lat. 58º - 62º N



350 – 650 m

4

G3

Interior south-eastern Norway

Lat. 58º - 62 ºN



650 – 950 m

4

G4


Western Norway

Lat. 58º - 62 ºN



0 – 350 m

2

G5

Central and northern Norway

Lat. 62º - 66º30‘N



0 – 250 m

3

G6

Central and northern Norway

Lat. 62º - 66º30‘ N



250 – 550 m

3

G7

Northern Norway

Lat. 66º30’ - 70ºN



0 – 250 m

1




Figure 1. Map of Norway with the seven breeding zones G1 – G7 based on materials from native Norway spruce populations. The breeding zone G0 is based on materials from more southern provenances outside Norway. Each breeding zone contains several regions of provenance or seed collection regions which are delineated by red border lines.



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