Will genomics guide a greener forest biotech

Forest biotechnology has been increasingly associatedwithwoodproductionusingplantationforestry,andhasstressed applications that use pedigreed material andtransgenic trees. Reasons for this emphasis includelimitations of available technologies to conform tounderlying genetic features of undomesticated foresttree populations. More recently, genomic technologieshave rapidly begun to expand the scope of forest bio-technology. Genomic technologies are well suited todescribeandmakeuseoftheabundantgeneticvariationpresent in undomesticated forest tree populations.Genomics thus enables new research and applicationsfor conservation and management of natural forests,and is a primary technological driver for new researchaddressing the use of forests trees for carbon sequestra-tion, biofuels feedstocks, and other ‘green’ applications.The roots of forest biotechnologyTwo major drivers have inﬂuenced the focus of forestbiotechnology. The ﬁrst driver was the inﬂuence of would-be end users of forest biotechnology. Requests for forestbiotechnology research and applications have come dispro-portionatelyfromindustryversusconservationgroups,andthe term forest biotechnology has been increasingly associ-ated with applications for industrial plantation forestrywith the aim of improved wood and ﬁber production. Thesecond driver has been the limited ability of availabletechnologies to address problems associated with naturalforests. Technologies and approaches have been adaptedfrom crop biotechnology and applied successfully to pedi-greed material for industrial plantation forestry. But ingeneral, the fundamental genetic attributes of undomesti-cated tree populations greatly limit the application of cropbiotech approaches to natural forests.In this Opinion article, I discuss the strengths andlimitations of past forest biotechnology efforts, and pointto two new drivers that are strengthening and broadeningforest biotechnology. (i) Investment in forest genomics isdeveloping more generalized technologies that areapplicable to industrial plantations and to natural forests.(ii) Forest biotechnology is being expanded to address newor previously intractable problems, including the geneticdissectionofadaptivetraitsvitaltoforestconservationandmanagement, the use of forest trees as carbon sinks, andthe use of forest trees as sources of biofuels.Inherent genetic architecture of forest treeschallenges limitations of available technologiesThe past focus of forest biotechnology in part reﬂects thechallenges posed by the genetic attributes of forest trees,and the limitations of extending available biotechnologiesdeveloped for agricultural crop species to forests. Thegenetic attributes of forest trees stand in stark contrastto those of domesticated annual crop plants. Forest treestypically have long generation times, are wind pollinatedwith outcrossing mating systems, and have not been sub-jected to signiﬁcant domestication. Individual trees arehighly heterozygous and carry a high genetic load (seeGlossary), such that mating between related individualsresultsininbreedingdepressionand,thus,precludesstrat-egies involving creation of inbred lines. In contrast to cropspecies that have lost genetic variation during domesti-cation, most natural tree populations contain largeamounts of genetic variation that can be exploited inbreeding programs. Furthermore, unlike crop species, for-est trees are expected to have minimal population sub-structure and low linkage disequilibrium [1,2]. A practicalconsequence of low linkage disequilibrium is that linkagerelationships between markers and alleles of genes con-trolling phenotypic traits are not consistent among indi-viduals, which limits the application of marker-assistedselection and breeding. Collectively, the characters ofinbreeding depression and low linkage disequilibrium com-bined with limitations of past technologies have skewedthe focus of forest biotechnology towards pedigreed mat-erial and applications for industrial plantation forestry.Opinion