1. Forest Genetics And Tree Breeding Kenneth Williams Fisheries Extension Specialist Langston University Aquaculture Extension Program Elements of Forestry

2. Problems in Forest Genetics Large size Long life cycle – 15-20 yrs to sexual maturity Large land area needed – Over time may be destroyed by natural catastrophe

3. Natural Variation in Populations Allows trees to adapt to changing environment Increases likelihood of finding individual trees with economically superior traits.

4. Continuous vs. Discontinuous Variation Discontinuous ex. Seeds red or white Continuous ex. Seeds red through many shades of pink to white. Most colors clustered around the mean. Most tree traits of interest show continuous variation.

5. Genetic Variation Genotype – genetic makeup of an individual organism. Phenotype – external appearance of the individual. Phenotype can be seen and measured. Genotype usually cannot.

6. “Nature / Nurture” What traits are inherited and what traits are environmentally caused?

7. Provenance Studies Seeds from various geographic regions are grown together in 1 or more locations under similar conditions that allow a comparison of the seed sources in order to identify superior seed stocks.

8. Provenance Studies These studies demonstrate that many tree species are genetically quite variable. Certain variations related to climate. Characteristics changed systematically with increasing altitude and latitude of seed origin. Variation was shown to be in response to environmental factors. Ex. Growing season and minimum winter temperature.

9. Provenance Studies Adaptation to climate is and other survival and growth traits are controlled by patterns of continuous variation. Geographic patterns of variation are best explained by natural selection in response to environment.

10. Provenance Studies Complex adaptations due to competitive interactions for light, moisture etc. Sun leaves and shade leaves. Sun leaves - smaller, thicker outer edges of canopy. More chlorophyll. Shade leaves opposite.

11. Shade leave / Sun Leaves Shade leaves are: * thinner and weakly lobed * large surface area * less support tissue fewer stomata *Sun leaves are: * more xerophytic in nature, * possess thicker cuticles, * more and longer palisade cells * well developed vascular tissues.

12. Origin and Modification of Natural Variation Mutations – source of all genetic variation. Most are harmful. Trees not good organism for studying mutation. Life cycle too long. Genetic recombination more common source of variation. Because most trees reproduce sexually, recombination is an extremely important evolutionary mechanism.

13. Migration and Gene Flow As A Source Of Variation Migration by way of seed dispersal and pollination. Pollen from outside sources can contaminate and hinder production of improved seed.

14. Random Processes That Modify Variation Isolated populations. “founder effect” – population established by a very few individuals.

15. Directional Modification of Variation Principle of selection – there is variability of organisms. Selecting small transmittable differences over time accumulates until visible differences appear in the organism. Natural selection has no purpose. It is the consequence of the differences between individuals with respect to their ability to produce offspring.

16. Provenance Selection Select best stands before selecting individuals within a stand. Difference between stands ( groups of trees from a specific location) can be very great.

17. Exotic Introduction Exotic – a plant growing outside of its natural range. Conifers introduced into the southern hemisphere for timber and fiber production. Often introduced in the search for disease and pest resistance. Ex. Eurasian elms introduced in U.S. after problems with Dutch Elm disease. Environmental similarity important for the success of exotics.

18. Interspecific Hybrids Success in forestry is small. Greatest use in developing disease and pest resistant trees.

19. Plus- Tree Selection Trees selected from wild populations that exhibit one or more superior traits.

20. Comparison – Tree Selection Tree compared to neighboring trees and is selected if it exceeds neighbors in traits of interest. Used in Southern, even aged pine stands where most environmental, age and planting factors are the same for all trees. Does not work well in uneven – aged stands.

21. Baseline Selection Comparing a selected tree to the regional average. To be selected the tree must exceed regional average in traits of interest.

22. What Size Breeding Population? Large enough to maintain genetic variability for future. Small enough to be cost effective and fit space available. Small enough to make substantial genetic gains quickly. Need a balance of all factors.

23. Seeds or Scions? Seeds – original genotype no longer intact. Each seedling contains a different sample of the original trees genes plus genes from pollinating tree. Scions – exact genotype of selected tree. Generally provides greater opportunity for genetic improvement.

24. Evaluation Of Select Trees Wild tree selection serves as first approximation of individual tree’s genetic worth. Observations over time used to refine evaluation.

25. Progeny Testing Evaluates offspring of selected trees. Trees shown to have undesirable genotypes are eliminated from the seed orchard.

26. Genetic Gain Genetic gain = improvement Can be lost if breeding populations are severely limited. = inbreeding depression. Expanding number of stands from which trees are selected reduces the chance of inbreeding becoming a problem.

27. Heritability Estimate Proportion of variation in the population that is due to genetic differences among individuals. Can be increased by controlling as many environmental factors as possible. Then selection from orchard is more likely to be due to genetic differences. Genetic gain from wild-tree selection is about 10- 20% depending on species and trait selected.

28. Advanced Generation Breeding Just beginning to have significant numbers of 2 nd or 3 rd generation selected trees. Many promises of improvement. Many problems associated with F2 generations. Lonnnnng term research.

29. Domesticating The Forest Natural forests are being rapidly replaced with native or exotic trees. Monoculture on the rise.

30. Natural Population Pros Well adapted to site Replacement trees from distant source may be poorly adapted.

31. Plantation Forests May be ecologically unstable in monoculture. However, some species (ex. Douglas fir and Jack pine) naturally grow in monocultures. Most concern is not species monoculture but genetic diversity. Most examples of devastated monoculture systems involve clones.

32. Plantation Forests Most objectionable feature to many people is the visual uniformity of monocultures. – Even aged stands – Even spacing – Same species

33. Plantation Forests Solution – mixed species plantings that are compatible in the plantation system.

34. Preserving Natural Variation Need for genetic resource conservation is widely recognized. Original wild population called progenitor populations. Many have already been lost.

35. Preserving Natural Variation Logging and other human activities have depleted the genetic base of forest trees. High-grading – removing the best trees from a forest. And monoculture tends to reduce genetic variability. Inadvertent introduction of pests cause loss of genetic variation. (chestnut blight and Dutch elm disease.)

36. Preserving Natural Variation Parks and National forests may be used to preserve genetic material. Special storage facilities. (Colorado and in Arctic) Breeding orchards and other collections of trees.

37. Future Directions Forecasting human needs for timber 1-2 generations in the future is difficult. Large trees are a thing of the past. Trees will be harvested at increasingly smaller size and younger age. Forest products industries will have to adapt to changes in tree size.

38. Future Directions Gene banks needed in case tree selections prove to be disastrous in the future. Additional genetic gains appear to be possible for a number of generations in the future. Ability to stimulate flower production in juvenile trees will greatly accelerate breeding and testing programs.

39. Biotechnology Efforts have lagged behind because trees are slow and difficult organisms to work with. Their genetics are poorly understood. Economic payoff is slower. Will eventually play some part in traditional breeding programs.

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