Mendel's followers

The genetic improvement of trees involves the application of genetic principles associated with silvicultural practices likely to improve trees’ quality and growth characteristics. Although the goal of forest genetics research has traditionally been to increase stem volume, research is increasingly centering on the identification of genes associated with traits such as disease and insect resistance, wood quality and embryogenic capacity. Researchers at the Laurentian Forestry Centre (LFC) of the Canadian Forest Service (CFS) have been studying the genetics of tree species and populations for nearly half a century. The main participants in this area of research are scientists Jean Beaulieu, Francine Bigras, Nathalie Isabel and Gaëtan Daoust. This text will outline their recent work.

50 YEARS OF RESEARCH AND STILL MUCH TO ACHIEVE

Forest genetics is a descriptive science. Its objective is to acquire a basic understanding of genetic variations in tree species and the causes and consequences of such variations. It focuses as much on the distribution of genetic diversity in natural forests as on understanding the organization of genes and their impact on observable traits such as tree volume or shape.

White spruce progeny test.

CFS - LFC’s interest and participation in research on the genetics and breeding of forest trees dates back to the early 1950s, when forest geneticists were conducting the first studies to measure the extent of genetic variation in the main forest tree species and determine potential gains in growth and quality. Then came a number of tree improvement programs, including one still being carried out today, on white spruce, the most advanced. White spruce is one of the main native species used in reforestation efforts in Quebec. The white spruce breeding program, supervised by Dr. Jean Beaulieu between 1990 and 1996, has been transferred to the ministère des Ressources naturelles du Québec, as has the entire field of tree improvement, which was previously carried out by both departments. In the future, the CFS - LFC will concentrate exclusively on basic research in forest genetics.

White spruce DNA markers.

Today, a number of original studies are being carried out at the Laurentian Forestry Centre in collaboration with researchers from the ministère des Ressources naturelles du Québec and l'Université Laval. In particular, they include studies to discover genetic markers associated with economically important traits in commercially valuable softwood species and studies on the distribution of genetic diversity in natural forests and the capacity of superior stock to adapt to anticipated climate change.

GENETIC DIVERSITY

To be able to protect and make better use of forest resources, an understanding of the genetic diversity of species is required. Genetic diversity is the direct result of differences in genes among individuals of the same species. It is the source of all diversity, as well as of the capacity of species to adapt to changing environmental conditions. CFS - LFC is currently carrying out several projects on genetic diversity to gain insight into the distribution of diversity and how it is transmitted from generation to generation. Forest geneticists are working to discover the links between genetic fingerprints (obtained using techniques from molecular biology) and economically important traits that can be observed with the naked eye.

Various markers can be used to reveal the presence of genetic diversity. They include markers based on enzymes (molecules manufactured from the information contained in genes). Similarly, differences between two individuals can be obtained by comparing their genetic fingerprints as obtained from DNA markers (DNA is the major component in genes and the basis of heredity).

The history of settlement in Quebec suggests that man has also had an influence on levels of genetic diversity found in white pine populations. To test this hypothesis, Dr. Beaulieu used enzyme markers and found that white pine populations in the St. Lawrence Valley have lower levels of genetic diversity than populations in the Outaouais region. This information will be used to formulate reforestation and conservation strategies for this species. In another study using enzyme and DNA markers, researchers Nathalie Isabel and Jean Beaulieu found that this phenomenon did not occur in black spruce populations, which had similar levels of diversity throughout the species’ range in Quebec.

THE NEXT GENERATION OF RESEARCHERS

Laurentian Forestry Centre researchers are supervising a master’s student who is studying levels of genetic diversity in northern populations of butternut. Such research is urgent, before butternut canker, which is causing serious damage in the United States, attacks our populations.

In addition, another master’s student is working with researchers Jean Beaulieu and Gaëtan Daoust on the genetics of new populations in Canada. Harvesting pressures have radically increased on this species, previously overlooked but now known to contain substances in its needles called taxanes which can be used to fight some cancers. These studies have provided useful information on genetic diversity in the species and have allowed conservation measures to be proposed to ensure that large-scale harvesting does not harm natural populations.

INVESTING IN GENETIC IMPROVEMENT IS COST EFFECTIVE

The Norway spruce, introduced in Quebec in the early 20th century, is very popular as a plantation species, since it provides better yields than native spruce species. Norway spruce is very susceptible, however, to white pine weevil. Although the weevil does not significantly affect productivity, it is disliked by forest managers and woodlot owners, due to the damage it causes in young plantations. Reforestation efforts have suffered as a result, with a significant decrease in the use of the species in plantations.

In the mid-1980s, researcher Gaëtan Daoust, in collaboration with scientists from the ministère des Ressources naturelles du Québec and other scientists at the CFS - LFC, began a genetic improvement program on Norway spruce. The program allowed several provenances with superior phenotypic qualities (visible traits) to be identified. Clones with a high degree of resistance to white pine weevil were selected from the breeding program stock. Recent studies have shown that, despite the damage to Norway spruce caused by white pine weevil, the impact of the pest is acceptable over the medium term and the species’ growth potential is very high. These results provide a strong argument in favour of increasing reforestation efforts with improved seed from the species.

White pine pollen harvesting.

Governments have been very supportive of tree improvement programs for species like the Norway spruce, since the long-term economic benefits of such programs justify the investments made. A very recent study on the economic impact of the genetic improvement of Norway spruce has shown that the research costs associated with identifying recommended provenances can be recovered in less than a year. According to the authors, Jean-François Côté of DGR Forestry Consultants, Gaëtan Daoust and Sylvain Masse of the CFS - LFC and Guy Prégent of the ministère des Ressources naturelles du Québec , the use of genetically improved trees in plantations will probably result in additional annual profits of $777,000 in Quebec, as opposed to costs of $400,000 for the research required to identify the recommended provenances. Estimated benefits from the use of improved seedlings range from $400/ha to $2500/ha depending on site quality. This represents additional revenues to the Quebec government of up to 27%, assuming reforestation is done at the most fertile sites. Equally encouraging results can be expected with other species that perform well such as white spruce.

GENETIC MARKERS FOR THE EARLY EVALUATION OF WOOD QUALITY

An evaluation of the physical characteristics of wood is an important competent of tree improvement programs. Even today, the best way to assess the quality of wood is to measure its density.

In the early 1990s, a study by a team of geneticists at the CFS - LFC, based on a progeny test of 39 families of white spruce, demonstrated that the density of mature wood is under strong genetic control. The heritability of this trait, or the measurement of the degree to which a trait is influenced by genetic factors, had one of the highest values obtained for an economically important trait.

DNA sampling to reveal the presence of genetic markers.

In forest species, reliable evaluations of economically important traits such as wood density or fibre length cannot be done immediately after planting. In the case of species like white spruce, they take a good twenty years, which is a significant limitation.

To deal with this problem, Dr. Nathalie Isabel and Dr. Jean Beaulieu, researchers at the CFS - LFC, are trying to find DNA markers closely associated with the genes for the sought-after traits. These markers provide an indication of the presence of one or more genes determining wood quality. Up to now, three markers potentially indicative of high wood density in white spruce have been found. Tests to verify the value of the markers have shown that the best marker represents a genetic gain of 4%, which corresponds to an increase in density of 13 kg/m³.

At the same time, the phylogeny (or genealogy) of trees selected for the quality of their wood was determined in order to be able to locate the genes responsible for wood characteristics through genetic mapping.

Dr. Isabel and her colleagues are also interested in identifying other markers associated with various economically important or adaptive traits in spruces. These markers could then be used to help breeders select the best trees at an early age, without having to wait years before directly evaluating the traits in question. Instead, researchers will just have to collect a few needles from a tree, extract the DNA and determine if the sought-after marker is present.

DNA sampling to reveal the presence of genetic markers..

INTEGRATING RESEARCH AREAS

Changes that occurred at the CFS in 1995 resulted in the creation of national science and technology networks (including the tree biotechnology and advanced genetics network). They have encouraged the greater integration of work by researchers in the different disciplines. In 1996, research efforts linking forest genetics and tree physiology intensified.

Needle sampling for the freezing tolerance test .

Researchers have been trying for years to understand the physiological mechanisms behind cold hardiness, not only to reduce frost damage but also to extend the distribution of some species northward. In plants, frost hardiness is genetically determined. Dr. Francine Bigras, who has been studying the physiology of stress in nursery-grown forest seedlings for a number of years, has begun work on frost hardiness in white spruce families resulting from controlled crosses and in greenhouse-produced Norway spruce families. The goal of this research, done in collaboration with Dr. Jean Beaulieu for white spruce and Gaëtan Daoust for Norway spruce, is to determine the degree of resistance to freezing in genetically improved seedlings and determine if production methods for improved seedlings cause variations in freezing tolerance.