Tree breeding

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Tree breeding is the application of genetic, reproductive biology and economics principles to the genetic improvement and management of forest trees. In contrast to the selective breeding of livestock, arable crops, and horticultural flowers over the last few centuries, the breeding of trees, with the exception of fruit trees, is a relatively recent occurrence.

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Pinus radiata grafts in preparation for the establishment of a seed orchard in New Zealand Grafts.jpg
Pinus radiata grafts in preparation for the establishment of a seed orchard in New Zealand
Isolation bags for controlled pollination in a Pinus radiata seed orchard. Isolation bags.jpg
Isolation bags for controlled pollination in a Pinus radiata seed orchard.

A typical forest tree breeding program starts with selection of superior phenotypes (plus trees) in a natural or planted forest, often based on growth rate, tree form and site adaptation traits. This application of mass selection improves the mean performance of the forest. Offspring is obtained from selected trees and grown in test plantations that act as genetic trials. Based on such tests the best genotypes among the parents can be selected. Selected trees are typically multiplied by either seeds or grafting and seed orchards are established when the preferred output is improved seed. Alternatively, the best genotypes can be directly propagated by cuttings or in-vitro methods and used directly in clonal plantations. The first system is frequently used in pines and other conifers, while the second is typical in some broadleaves (poplars, eucalypts and others). The objectives of a tree breeding program range from yield improvement and adaptation to particular conditions, to pest- and disease-resistance, wood properties, etc. Currently, tree breeding is starting to take advantage of the fast development in plant genetics and genomics.

Optimisation

Tree breeders make efforts to get their operation efficient by optimising tree breeding. Scientists develop tools aimed at improvement of the efficiency of tree breeding programmes. Optimising can mean adapting strategies and methods to certain species, group of populations, structure of genetic variation and mode of inheritance of the important traits to obtain the highest benefit per unit of time. Optimising is usually carried out at the following levels: breeding strategy (appropriate intensity of breeding, breeding population structure and size, plan for maintenance of genetic diversity), breeding methods (mating type, testing and selection methods, testing population size and time) and deployment methods of the genetically improved material (seed orchards [1] and clonal forestry: genetic contribution, size). Computer simulators are frequently used: stochastic – based on defined and random algorithms; and deterministic – based on defined algorithms.

Selection strategies have been compared for annual progress in long-term breeding at a given annual cost considering genetic gain, gene diversity, cost components, and time components. For Norway spruce it seems favourable to clone full sib families and then select based on clonal performance [2] while for Scots pine a two-stage strategy seems best, first phenotypic pre-selection and then progeny-testing the selections. [3]

Tree improvement

A genetically variable population and a method of selecting genetically superior individuals provide the basis for tree improvement by breeding. In essence, a tree improvement program sets out to isolate and evaluate the genetic component of variation in one or more characters of interest. In the simplest procedure, cycles of selection reduce the available population in a particular direction to enhance desirable traits, then breeding from selections to expand the population with improved characteristics. Breeding strategies vary with species and objectives, but all use mating designs to generate information and new material. Choice of a suitable breeding strategy and mating design is a key decision in any breeding program. Kiss (1986) [4] used a 2-level design in British Columbia to study variation within and between separate populations of white spruce, both within British Columbia and from eastern North America.

The breeding program for white spruce initiated in 1986 by the Canadian Forestry Service in the Maritimes employed 2 kinds of mating: polycross, to test clones for general combining ability; and pair-mating, to generate material for second generation selections (Fowler et al. 1988). [5]

Newton's (2003) [6] systematic review of yield responses of white spruce and 3 other North American conifers to forest tree improvement practices indicated that correct provenance-progeny selection could yield juvenile height growth gains of about 12% at 20 years for white spruce, and a corresponding merchantable productivity (mean annual merchantable volume increment) gain of 26% at 50 years for plantations established at nominal initial densities on medium-to-good quality sites. Also, preliminary estimates derived from individual case studies indicated that first generational selection strategies for white spruce could increase merchantable productivity by approximately 20% at 45 years.

See also

Related Research Articles

<i>Ex situ</i> conservation Preservation of plants or animals outside their natural habitats

Ex situ conservation literally means, "off-site conservation". It is the process of protecting an endangered species, variety or breed, of plant or animal outside its natural habitat; for example, by removing part of the population from a threatened habitat and placing it in a new location, an artificial environment which is similar to the natural habitat of the respective animal and within the care of humans, example are zoological parks and wildlife sanctuaries. The degree to which humans control or modify the natural dynamics of the managed population varies widely, and this may include alteration of living environments, reproductive patterns, access to resources, and protection from predation and mortality. Ex situ management can occur within or outside a species' natural geographic range. Individuals maintained ex situ exist outside an ecological niche. This means that they are not under the same selection pressures as wild populations, and they may undergo artificial selection if maintained ex situ for multiple generations.

<span class="mw-page-title-main">Selective breeding</span> Breeding for desired characteristics

Selective breeding is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together. Domesticated animals are known as breeds, normally bred by a professional breeder, while domesticated plants are known as varieties, cultigens, cultivars, or breeds. Two purebred animals of different breeds produce a crossbreed, and crossbred plants are called hybrids. Flowers, vegetables and fruit-trees may be bred by amateurs and commercial or non-commercial professionals: major crops are usually the provenance of the professionals.

<span class="mw-page-title-main">Vegetative reproduction</span> Asexual method of reproduction in plants

Vegetative reproduction is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment or cutting of the parent plant or specialized reproductive structures, which are sometimes called vegetative propagules.

<i>Pinus echinata</i> Species of conifer

The shortleaf pine is a softwood conifer tree that has short needles and small cones. The species is mainly found in southeastern United States, and can inhabit various climates. The shortleaf pine is sometimes referred to as the “old field”, “spruce”, “rosemary”, “yellow”, “two-leaf” and “heart” pine; however, there is a true shortleaf pine that is different from these pine variations. The confusion stems from a custom in the Southeastern United States to only refer to pines as either “long-leaf” or “short-leaf”. Furthermore, the pine can be distinguished from other pines by examining their short leaves and small cones.

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<span class="mw-page-title-main">Seed orchard</span>

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<i>Ulmus wallichiana</i> Species of tree

Ulmus wallichianaPlanch., the Himalayan elm, also known as the Kashmir elm and Bhutan elm, is a mountain tree ranging from central Nuristan in Afghanistan, through northern Pakistan and northern India to western Nepal at elevations of 800–3000 m. Although dissimilar in appearance, its common name is occasionally used in error for the cherry bark elm Ulmus villosa, which is also endemic to the Kashmir, but inhabits the valleys, not the mountain slopes. The species is closely related to the wych elm U. glabra.

<span class="mw-page-title-main">Connecticut Agricultural Experiment Station</span> United States historic place

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<span class="mw-page-title-main">Grafting</span> Horticultural technique of joining plant tissues to grow together

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<i>Thinopyrum intermedium</i> Species of flowering plant

Thinopyrum intermedium, known commonly as intermediate wheatgrass, is a sod-forming perennial grass in the Triticeae tribe of Pooideae native to Europe and Western Asia. It is part of a group of plants commonly called wheatgrasses because of the similarity of their seed heads or ears to common wheat. However, wheatgrasses generally are perennial, while wheat is an annual. It has gained the Royal Horticultural Society's Award of Garden Merit as an ornamental.

<span class="mw-page-title-main">Plant genetics</span> Study of genes and heredity in plants

Plant genetics is the study of genes, genetic variation, and heredity specifically in plants. It is generally considered a field of biology and botany, but intersects frequently with many other life sciences and is strongly linked with the study of information systems. Plant genetics is similar in many ways to animal genetics but differs in a few key areas.

<span class="mw-page-title-main">Istituto di Genetica Vegetale</span>

Istituto di Genetica Vegetale (IGV) is a research network om Plant Genetics and Breeding within the Italian Consiglio Nazionale delle Ricerche. IGV is headquartered in Bari and has four different Divisions in Portici, Palermo, Florence and Perugia. IGV started its activities in November 2002.

<span class="mw-page-title-main">Plant breeding</span> Humans changing traits, ornamental/crops

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This glossary of genetics and evolutionary biology is a list of definitions of terms and concepts used in the study of genetics and evolutionary biology, as well as sub-disciplines and related fields, with an emphasis on classical genetics, quantitative genetics, population biology, phylogenetics, speciation, and systematics. Overlapping and related terms can be found in Glossary of cellular and molecular biology, Glossary of ecology, and Glossary of biology.

References

  1. Lindgren, D. and Prescher, F. 2005. Optimal clone number for seed orchards with tested clones. Silvae Genetica 54: 80-92.
  2. Danusevičius D & Lindgren D 2002. Efficiency of Selection Based on Phenotype, Clone and Progeny Testing in Long-term Breeding. Silvae Genetica 51:19-26.
  3. Danusevičius D & Lindgren D 2002. Two-stage selection strategies in tree breeding considering gain, diversity, time and cost. Forest Genetics. 9:145-157.
  4. Kiss, G.K. 1986. Genetic improvement of white and Engelmann spruce in British Columbia 1983–85. p. 191–193 in Yeatman, C.W.; Boyle, T.J.B. (Eds.), Proc. 20th Meet. Can. Tree Improv. Assoc. Part 1, Quebec QC.
  5. Fowler, D.P., Bonga, J.M., Park, Y.S., Simpson, J.D., and Smith, R.F. 1988. Tree breeding at the Canadian Forestry Service – Maritimes 1985 and 1986. p. 31–36 in Morgenstern, E.K.; Boyle, T.J.B. (Eds.). Tree Improvement – Progressing Together Sympos., Truro NS, Aug. 1987. Proc. Part 1, 21st Meet. Can. Tree Improv. Assoc.
  6. Newton, P.F. 2003. Systematic review of yield responses of four North American conifers to forest tree improvement practices. For. Ecol. Manage. 172:29–51.

Selected bibliography