Over the past years, a great deal has been learned about variation in wood prop­ erties. Genetic control is a major source of variation in most wood properties. Wood is controlled genetically both directly in the developmental or internal pro­ cesses of wood formation and indirectly by the control of tree form and growth patterns. Emphasis in this book will be on the internal control of wood production by genetics although there will be two chapters dealing with the indirect genetic control of wood, which was covered in detail in the previous book by Zobel and van Buijtenen (1989). The literature on the genetics of wood is very variable, SO'lle quite superficial, on which little reliance can be placed, and some from well-designed and correctly executed research. When suitable, near the end of each chapter, there will be a summary with the authors' interpretation of the most important information in the chapter. The literature on the genetics of wood can be quite controversial. This is to be expected, since both the environment and its interaction with the genotype of the tree can have a major effect on wood properties, especially when trees of similar genotypes are grown under widely divergent conditions. Adding to the confusion, studies frequently have been designed and analyzed quite differently, resulting in conflicting assessments of results.

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.- 1.4 The Causes and Types of Wood Variation.- 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.- 2.2 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.- 3.4 Obtaining Wood Samples.- 3.5 Methods of Determining Wood Density.- 3.6 Methods of Determining Other Wood Properties.- 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.- 4.2 The Effect of Genetic Manipulation of Wood Density on the Final Product - General.- 4.3 Summary.- 5 The Genetics of Wood Density.- 5.1 General.- 5.2 The Genetic Control of Wood. Density in ·the Conifers.- 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.- 6.2 Cells of the Hardwoods.- 6.3 Cells of the Conifers.- 6.4 Cellulose Yield and Pulp and Paper Products.- 6.5 Summary.- 7 Grain, Fibril Patterns, and Internal Defects.- 7.1General.- 7.2 Spiral 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.- 8.3 Juvenile Wood and Genetics.- 8.4 Chemistry of Wood.- 8.5 Miscellaneous Traits.- 8.6 Summary.- 9 Wood Genetics Related to Provenance and Seed Source.- 9.1 The Meaning of Provenance and Seed Source.- 9.2 The Overall Effect of Provenance.- 9.3 S Summary.- 10 Correlations Among Wood Properties and with Growth Rate.- 10.1 General Concepts.- 10.2 Growth Rate and Wood Properties.- 10.3 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.- 11.3. 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.- 13 Improvement in Wood by Using Genetics.- 13.1 Current and Future Usage of Genetics to Change Wood.- 13.2 Examples of Changes in Wood by the Use of Genetics.- 13.3 Improving Wood When There Is a Negative Correlation with Growth Rate.- 13.4 Summary.- References.- Species Index.