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Land race• Introduced trees that are adapted to an environment after several generations • Advantage Natural selection helps land races adapt to a new environment • Disadvantage May not

Terms Commonly Used in Tree Improvement

Khongsak Pinyopusarerk

CSIRO/Ensis-Genetics Canberra, Australia

• A community of interbreeding individuals

No degree of relationship is assumed.

• The term “Stand” is often used

synonymously.

• Geographic location where seed was collected.

• Refers to natural forests, not

plantations.

• Provenance boundaries not always clear-cut, often one of judgment and opinion.

• Provenance may have different genetic adaptation.

10°

20°

Kilometres

32

31

30 29

28 27

25 26

1 6 1 9 22

15

24 23

21

17 18 14

13 1-12 20

Land race

• Introduced trees that are adapted to an

environment after several generations

• Advantage

Natural selection helps land races adapt to a new

environment

• Disadvantage

May not be from the best natural provenances or come from very small genetic base

• Individuals with parents in common

• Half-sib family

One common mother, father unknown

• Full-sib family

Both parents in common

Generated by artificial (controlled) pollination

• Trees produced from the seed of a known

parent

• Progeny tests are established to determine the genetic worth of the parent trees

• Testing of vegetative propagules (e.g grafted or cutting materials) is also a progeny test, but

often called “clonal test”

• The genetic potential of the tree when

environmental factors are excluded, i.e only determined by the genes of the tree.

• Genotype is determined chiefly from

performance of progeny and other

relatives.

• The tree as we see it

• Phenotype is determined by the genotype (G) plus the environment (E)

P = G x E

• Similar phenotypes do not necessary breed alike

In natural stand phenotype is influenced by the environment in which the trees are growing

When growing in plantations and under similar

environmental conditions, superior phenotypes tend to have good genetic potential.

Genetically identical individual trees (ramets) produced by vegetative propagation from founder tree (ortet).

Ortet

(superior tree

in field trial)

Ramets

Vegetative propagation

(Cuttings, grafts, or micropropagation)

One clone

Clone

These trees were propagated by cuttings.

The original plant from

which a clone has been

derived

An individual member of a clone

In breeding

• Production of offspring by mating between closely related trees, usually by

Selfing.

• This procedure if carried out for a number of

generations will expose undesirable, recessive characters.

• Production of offspring by mating between unrelated trees or distantly related trees.

• Systematic removal of undesirable individuals from a population

• Synonym with “ culling ”

Heritability (h2)

• Measure of proportion of variation due to genetics (ranges from 0 to 1)

• Apply only to a particular population

growing in a particular environment

• Usually within an expected range

Growth: h2 = 0.15 – 0.25 (moderate)

Wood density: h2 = 0.40 – 0.60 (high) Branching : h2 = 0.05 – 0.10 (low)