Jackson B. Jett

Genetics of wood production

1 The Role of Genetics in Wood Production-General Concepts.- 1.1 Background Information.- 1.2 Categorization of Wood and Trees.- 1.3 Wood Properties of Importance.- 1.3.1 Wood Density (Specific Gravity).- 1.3.1.1 The Genetics of Wood Density in Conifers - General Introduction.- 1.3.1.2 The Genetics of Wood Density in Hardwoods - General Introduction.- 1.3.2 Other Wood Properties.- 1.4 The Causes and Types of Wood Variation.- 1.4.1 Importance and Magnitude of Wood Variation.- 1.4.2 Assessing Genetic Improvements.- 1.4.2.1 Strength of Inheritance - General.- 1.5 Environmental vs. Genetic Influence on Wood.- 1.6 Literature on the Inheritance of Wood.- 1.7 Summary.- 2 Genetic Controls in Wood Formation.- 2.1 Controls Influencing Wood Development.- 2.1.1 The Kinds and Strength of Genetic Control in Wood.- 2.1.1.1 The Measurement of Genetic Control.- 2.1.1.2 The Change of Genetic Control with Tree Age - Juvenile and Mature Wood.- 2.1.1.3 The Environmental Control.- 2.1.1.4 Reaction with the Environment - Genotype x Environment Interaction.- 2.2 The Value of Genetic Differences in Wood.- 2.3 Summary.- 3 Sampling and Analysis in Genetic Studies on Wood.- 3.1 Making Wood Studies - Sampling Methods.- 3.2 Size of Sample.- 3.3 Location and Age of Sample.- 3.3.1 Estimating Whole Tree Specific Gravity Values from a Single Sampling Point.- 3.3.1.1 Age of Wood-Juvenile to Mature Wood Correlations.- 3.3.1.2 Removing Extractives.- 3.4 Obtaining Wood Samples.- 3.5 Methods of Determining Wood Density.- 3.6 Methods of Determining Other Wood Properties.- 3.6.1 Spiral Grain.- 3.6.2 Tracheids and Fibers.- 3.6.3 Moisture Content.- 3.6.4 Pulp Yield.- 3.7 Indirect Selection for Wood and Pulp Properties.- Appendix Table 3.1 Some methods used to determine wood density in trees.- Appendix Table 3.2 Some methods that have been used to determine spiral grain.- 4 The Importance of Wood Density (Specific Gravity) and Its Component Parts.- 4.1 General Concepts and the Importance of Wood Density.- 4.1.1 Earlywood and Latewood.- 4.1.1.1 The Ratio of Latewood to Earlywood and Its Value.- 4.1.1.2 Inheritance in Earlywood and Latewood.- 4.1.1.3 Wall Thickness.- 4.2 The Effect of Genetic Manipulation of Wood Density on the Final Product - General.- 4.2.1 The Effect of Wood Density on the Final Product for Conifers.- 4.2.2 The Effect of Wood Density on the Final Product for Hardwoods.- 4.2.2.1 Wood Density in the Diffuse-Porous Hardwoods.- 4.2.2.2 Wood Density in the Ring-Porous Hardwoods.- 4.2.2.3 The Effect of Rays and Vessels.- 4.3 Summary.- 5 The Genetics of Wood Density.- 5.1 General.- 5.2 The Genetic Control of Wood. Density in *the Conifers.- 5.2.1 Hard Pines.- 5.2.2 Soft Pines.- 5.2.3 Other Conifers of Major Importance.- 5.2.3.1 The Spruces and Firs.- 5.2.3.2 Douglas-Fir and Larch.- 5.2.4 Other Conifers of Minor Importance.- 5.3 The Genetic Control of Wood Density in Hardwoods.- 5.4 Genetic Gains in Wood Density Using Vegetative Propagation and Coppice.- 5.5 Inheritance of Within-Tree Variation in Wood Density.- 5.6 Summary.- 6 Inheritance of the Cellular Components of Wood, Cellulose Yield and Pulp and Paper Products.- 6.1 General Concepts.- 6.1.1 Variability and its Causes.- 6.2 Cells of the Hardwoods.- 6.2.1 Fiber Length.- 6.2.2 Fiber Diameter, Wall Thickness, and Percentage of Cell Types.- 6.2.3 Vessels and Rays.- 6.3 Cells of the Conifers.- 6.3.1 Tracheid Length.- 6.3.2 Other Tracheid Characteristics.- 6.4 Cellulose Yield and Pulp and Paper Products.- 6.5 Summary.- 7 Grain, Fibril Patterns, and Internal Defects.- 7.1 General.- 7.2 Spiral Grain.- 7.2.1 Interlocked Grain.- 7.3 Microfibrillar Angle.- 7.4 Miscellaneous Wood Grain Patterns, Figured Wood.- 7.5 Reaction Wood.- 7.6 Cracks, Shake, and Other Internal Defects.- 7.7 Summary.- 8 Tree Form and Internal Tree Characteristics.- 8.1 Introductory Comments.- 8.2 Stem. Form and Branching.- 8.2.1 Stem Straightness and Sinuosity.- 8.2.2 Stem Taper.- 8.2.3 Branching Characteristics.- 8.3 Juvenile Wood and Genetics.- 8.3.1 Juvenile to Mature Wood Transition.- 8.3.2 Changing the Properties of Juvenile Wood.- 8.4 Chemistry of Wood.- 8.4.1 Cellulose and Lignin.- 8.4.2 Extractives and Gum Yields.- 8.4.3 Heartwood.- 8.4.4 Other Chemicals.- 8.5 Miscellaneous Traits.- 8.5.1 Moisture Content.- 8.5.2 Bark Characteristics.- 8.5.3 Wood Color.- 8.6 Summary.- 9 Wood Genetics Related to Provenance and Seed Source.- 9.1 The Meaning of Provenance and Seed Source.- 9.1.1 Provenance, Geographic Source, or Geographic Race.- 9.1.2 Confusion and Complexity of Terms.- 9.1.3 Assessment of the Wood of Provenances.- 9.2 The Overall Effect of Provenance.- 9.2.1 Genetic Differences in Wood Properties Among Provenances of the Hard Pines.- 9.2.2 Genetic Differences in Wood Properties Among Provenances in Conifers Other Than the Hard Pines.- 9.2.3 The Importance of Provenance in Determining the Wood Properties of Hardwoods.- 9.3 S Summary.- 10 Correlations Among Wood Properties and with Growth Rate.- 10.1 General Concepts.- 10.2 Growth Rate and Wood Properties.- 10.2.1 Growth Rate and Wood Density.- 10.2.2 Growth Rate and Other Wood Properties.- 10.3 Wood Property Relationships in the Conifers.- 10.4 Relationships Among Wood Properties in Hardwoods.- 10.5 Relationship of the Wood Properties of Coppice, Rooted Cuttings, and Grafts to Donor Trees.- 10.6 Wood Property Relationships Between Chemical Composition and Pulp Properties.- 10.7 Summary.- 11 The Genetics of Miscellaneous Factors That Affect Wood.- 11.1 What Are Miscellaneous Factors?.- 11.2 Diseases and Insects.- 11.2.1 Diseases.- 11.2.1.1 Wood Decay and Discoloration.- 11.2.1.2 Other Effects of Disease.- 11.2.2 Insects.- 11.3. Wood Uniformity.- 11.4 Hybridization to Change Wood Properties.- 11.5 Effects of Polyploidy on Wood.- 11.6 The Effect of Tissue Culture and Biotechnology.- 11.7 Wood for Energy.- 11.8 Summary.- 12 Determination of Wood Properties to Be Used in a Tree Improvement Program.- 12.1 Using Genetic Information.- 12.2 Selection of Trees for a Genetics Program.- 12.2.1 Considerations for Selection.- 12.2.2 Opportunity for Early Selection.- 12.3 Choice of Wood Properties - What Should Be Included?.- 12.4 Summary.- 13 Improvement in Wood by Using Genetics.- 13.1 Current and Future Usage of Genetics to Change Wood.- 13.1.1 When to Employ Genetics.- 13.2 Examples of Changes in Wood by the Use of Genetics.- 13.2.1 The Hard Pines.- 13.2.2 Other Conifers.- 13.2.3 Temperate Hardwoods.- 13.2.4 Tropical Hardwoods.- 13.2.4.1 Eucalypts.- 13.3 Improving Wood When There Is a Negative Correlation with Growth Rate.- 13.4 Summary.- References.- Species Index.

Phenological variation in height and diameter growth in provenances and families of loblolly pine

The phenology of 5- and 6-year old loblolly pine (Pinus taeda L.) trees was studied over two different growing seasons (1993 and 94) in southwest Georgia. These trees were from 7–9 open-pollinated families from each of four different provenances planted at two locations. The provenances were: Atlantic Coastal Plain (eastern SC), Gulf Hammock (north FL), Lower Gulf (south AL, MS) and Upper Gulf (north AL, MS). Provenances did not vary as to when height growth started in spring, but showed very significant differences for the date of growth cessation in fall. The Gulf Hammock source grew the most and also had the longest height growth period, while the Upper Gulf source was first to stop height growth and had the least annual height increment. Provenances were also significantly different for the date of cessation of diameter growth (a difference of 22 days between Gulf Hammock and Upper Gulf), and the order of cessation was the same as for height. Families within provenances were significantly different for date of cessation of height growth and diameter growth. When family means were considered across provenances, there was a correlation of 0.69 (p-value = 0.0001) between annual height increment and date of height growth cessation. There was a weaker association between faster growth and a longer growing season within provenances.

Rootstock effects in grafted conifers: A review

The literature on rootstock effects (on scions) in conifers was reviewed, specifically: graft success, compatibility, size, reproduction, phenology, crown and needle characters, mineral contents, organic compounds, water relations, disease resistance and wood properties. Scions usually had higher graft success and less incompatibility on more closely related rootstocks although there were exceptions. Even intergeneric grafts have succeeded on occasion. Although there were marked rootstock effects on growth and reproduction, the effects did not follow a pattern with increasing relationship. It is also likely that some crown characters and the nutrient content of scions can be manipulated by the use of rootstocks. For many characters, a specific rootstock may give a desired result only for a limited number of scion types (species, cultivars or clones). With some exceptions, the review shows that the subject has not been comprehensively studied. Many of the studies were either short-term, inadequately replicated, or poorly designed to allow firm conclusions about rootstock effects. The physiological and biochemical mechanisms, which cause the changes seen in morphology, are not well understood. Further research and more comprehensive study of rootstock effects on scion biology are recommended.

Tree Form and Internal Tree Characteristics

Previous chapters have dealt with the most common wood characteristics and their inheritance patterns. This chapter, and Chapter 11, cover a miscellany of wood properties that did not fit into the previous chapters; but that does not imply that this chapter does not contain important information. It does! For example, improving tree form is the fastest and easiest way to improve wood properties and needs major consideration. Although a limited amount can be done with it genetically, an alteration of the pattern of juvenile wood production will have a major effect on wood utilization. Although wood chemistry often shows a strong inheritance, its effect on the final product is usually less than that of anatomical changes, and research on genetic aspects of wood chemistry has been limited. Moisture content, bark percentage, and wood color all have important inheritance patterns.

The Role of Genetics in Wood Production — General Concepts

For many years most tree improvement programs included growth, form, adaptability, and pest resistance in their assessments but did not include wood properties as such. It was recognized that tree form, growth rate, and pest tolerance could all affect wood in several ways, as was described by Zobel (1971) (Fig. 1.1). However, the potential for improving wood by direct application of genetics was not generally appreciated, although persons like Harris (1983) strongly emphasized the value of employing genetics to improve wood. Many people felt that if growth, form, and adaptability were central to a genetics program, there would be little opportunity left for altering wood, even if there were strong genetic control. However, as noted by Zobel (1972): “Addition of a wood property will enable moderate changes in wood while still being able to maintain the desired form, growth, and adaptability.” As early as 1935, Schreiner recognized the possibilities for genetic manipulation of wood and published an article on how pulping characteristics might be improved by breeding; these ideas were later expanded in his 1958 paper. The economic impact of changes in wood quality were recently outlined by Cubbage (1990). However, little proof was available regarding the inheritance of wood properties except for studies like those of Pawsey (1965) in Australia, who tested the wood of clones of radiata pine (Pinus radiata) and found large differences among clones but great similarity among ramets within a clone. The general possibility of improving wood quality through breeding was covered by Lahiri (1959) and an assessment of the wood qualities to use in tree breeding was made by Dadswell et al. (1963) in Pinus radiata and for Douglas-fir (Pseudotsuga menziesii) by Kellogg (1990).

Genetic Controls in Wood Formation

An explanation has already been given in Chapter 1 about how external factors (environmental), combined with internal factors, control the formation and qualities of wood. Both external and internal factors influence the physiology of the tree which, in turn, determines the kind of wood formed. Thus, without a good knowledge of physiology, one can only hypothesize what causes the production of differing types of wood. That is a major problem because, unfortunately, too little is known about the physiological processes and cell differentiation that control formation of wood with differing properties (Fig. 2.1).

The Importance of Wood Density (Specific Gravity) and Its Component Parts

A general definition of specific gravity and wood density was given in Chapter 1, but it will be of value to repeat a summary of it here. The two terms will be used interchangeably, since they measure the same thing although results are expressed using different units. Wood density and wood specific gravity both indicate the amount of actual wood substance present in a unit volume of wood (see Chap. 1.3.1). Although there are several different methods used to measure wood density, the standard way is to calculate the ratio between the dry weight of wood divided by the green volume of the same wood. This is often referred to as basic density (Tsoumis 1991). Thus, grams/cubic centimeter (specific gravity), pounds/cubic foot (wood density, English units) or kilograms/cubic meter (wood density, metric system) are all related. Because one ml of water equals 1 g, specific gravity is a unitless measurement and is expressed only, for example, as 0.45, not as 0.45 g/ml. The above classifications will be used throughout this book but the reader must observe carefully all data on wood density referred to in publications. Occasionally, one will find specific gravity or wood density expressed as the dry weight of wood divided by dry volume, or green weight or air-dry weight of wood over green volume or, very rarely, green weight of wood over dry volume. The values for wood density or for specific gravity will be quite different when such different methods of measurement are used.

Family stability of wood specific gravity in Pinus tecunumanii established on three sites in South America

Wood specific gravity was determined for 29 half-sib families of 4-year-old Pinus tecunumanii from the Mountain Pine Ridge, Belize, planted at three locations in Brazil and Colombia. Although there was a significant (p ≤ 0.05) family by sites interaction (F × S), it was found that only 5 of the 29 families were major contributors. The test planting at the highest elevation (1750 m, La Arcadia, Colombia) was the most interactive site.

The Genetics of Miscellaneous Factors That Affect Wood

This book has attempted to generally classify genetic factors that affect wood properties. However, several important items do not fit any general categorization and are reported in this chapter. Disease and insect attacks can have a major effect on wood and hybridization is rapidly becoming more important since the hybrids can be used with vegetative propagation techniques. Currently, biotechnology is being used in an attempt to improve wood quality.

Inheritance of the Cellular Components of Wood, Cellulose Yield and Pulp and Paper Products

There are many properties of wood that are under genetic control, most of which are essentially independent except for those that are actually dependent on each other, like cell wall thickness and specific gravity. Most show a relatively strong inheritance pattern. A few are of importance in determining product quality, but others play only a minor role. Frequently, it is not the cell component itself that is of importance, but ratios, such as cell length to wall thickness or to lumen size, that are important.