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Chapter 10.

The Role of Genetics and Improvement in Southern Productivity

R.C. Schmidtling, T.L. Robison, INTRODUCTION S.E. McKeand, R.J. Rousseau, onsumption of forest products is expected 1 H.L. Allen, and B. Goldfarb to continue its rapid increase during the C21st century. In contrast, the land base used for production is expected to decline because of population pressures, environmental concerns, lack of adequate management by many 97 Abstract—Because of space limitations, a landowners, and the divesture of lands deemed thorough discussion of the rich history of tree nonstrategic. Even today, removals equal or improvement in the Southeastern United States exceed growth rates in some areas (Wear and cannot be totally accomplished in this forum. Greis 2002). However, models indicate that the However, a synopsis of key program highlights potential productivity of in many regions and the people who forged and directed these can be much higher than is currently realized programs is presented, together with a discussion (Allen 2000, Bergh and others 1998, Sampson of current and future work. This discussion covers and Allen 1999). With investments in appropriate improvement programs for both southern pines management systems, growth rates > 25 m3/ha/ and hardwoods. Comparisons of and contrasts year for pines are biologically possible and between these two types of programs are can be financially attractive for a broad range discussed and punctuated by the reasons for of site types in temperate, subtropical, and tropical regions. successes and failures. Today, southern pine tree improvement programs are on the cutting edge In the early days of southern , of genetic technology, moving from open- vast areas were clearcut with little or no regard pollinated seed to clonal programs encompassing for regeneration. Natural regeneration was molecular genetic features. Programs for southern satisfactory in some areas but totally lacking in hardwoods generally are much less advanced, others. Very little planting occurred before the Civilian Conservation Corps began wide-scale because there are several limiting factors unique planting during the Great Depression. Wakeley to hardwoods and because hardwood fiber is (1944) estimated that < 500 acres of southern available at low cost. pines had been artificially regenerated successfully before 1920. Historically, the practice of focused on controlling the composition, quantity, and structure of forest vegetation and the maintenance of site quality. As forest have become important sources of fiber, , and structural material, this custodial role has given way to active intervention to improve both and soil resources. Forest managers are recognizing that intensive silviculture requires active management of both biotic and abiotic resources to optimize production. 1 Chief Geneticist (now Emeritus), U.S. Department of Silvicultural treatments including soil tillage, Forest Service, Southern Research Station, vegetation control, fertilization, fire, and Saucier, MS 39574; Research Scientist, MeadWestvaco, Wickliffe, KY 42087; Professor of Forestry, North Carolina can dramatically affect soil resources. The key State University, Raleigh, NC 27695; Central Forest Research Leader, MeadWestvaco, Wickliffe, KY 42087; and Geneticists, North Carolina State University Forest Tree Improvement Cooperative, Raleigh, NC 27695, respectively. Southern Forest Science: 98 Past, Present, and Future Productivity well before the turn ofthe20 well beforetheturn B Early Work SOUTHERN PINETREEIMPROVEMENT potential toberealized. sufficient resourcestoallowthefullgenetic best geneticmaterialavailableandtoprovide to optimizingfiberproductionisdeploythe U.S. DepartmentofAgriculture Forest Service AppalachianStation[now partofthe Service, of theU.S.DepartmentAgriculture Forest in 1934byA.L.McKinneyand L.E.Chaiken pollinated progenytestofloblolly pineinstalled 1951). pines (Dorman between longleafandslash( pinehybridin1929,across first artificialsouthern 1944). Wakeley isalsocredited withcreatingthe among geographicracesofloblollypine(Wakeley growth anddiseaseresistancevariedwidely Wakeley publishedage-15 dataindicatingthat pineswasunknownbefore effect insouthern pine.Themagnitudeoftheseed-source southern clearly demonstrategeneticdifferencesina Bogalusa, LA.Thistestwasoneofthefirstto an importantloblollypineprovenancetestnear aware ofseedsourceeffectsandin1926installed Although hehadlittletrainingingenetics,was Pines”(WakeleySouthern 1954)isstillinuse. silviculture, andhismanual“Plantingthe a monumentalamountofresearchinbasic in 1924.Hisundaunteddriveledhimtocomplete with PhilWakeley, whocameintotheregion treeimprovementbegan ofsouthern the history ( pinehybrid[longleaf first naturalsouthern CA, in1925. Genetics) atPlacerville, (which laterbecametheInstituteofForest G. EddystartedtheTree BreedingStation work withwalnut( in 1916.InspiredbysomeofLuther Burbank’s IdahoandColoradobegan sources innorthern ponderosa pine( initiated in1912(Kaufman1961),andtestingof [ collections foranextensivestudyofDouglas-fir for Europeanspecies.Inthiscountry, nativeseed importance ofgeographicseedsourcewasknown P. palustris Pseudotsuga menziesii Other earlyworkincludedalargeopen- Although Chapman(1922)identifiedthe efore 1920,littlewasknownabouthow productivity intheUnitedStates.Since seed sourcemightaffectforestplantation Mill.)xloblollypine( Pinus ponderosa Juglans (Mirb.)Franco] were spp.)hybrids,James P. elliottii th century, the P. taeda Laws.)seed Engelm.) L.)], attended. Sincethen,theconferences havebeen organizers weresurprisedwhen >80people held inAtlanta, of1951.The GA,inJanuary ForestSouthern Tree Improvement Conference research program.Theresultwasthefirst possibility ofestablishingaregionalseed-source ForestSouthern ExperimentStationonthe Authority (TVA) andthe Forest Service’s Relations DivisionoftheTennessee Valley beginning inthefallof1949betweenForestry second eventwasanexchangeofcorrespondence wasdevotedtotreeimprovement.The Appalachian SectionoftheSocietyAmerican tree breedersinEurope.The1950meetingofthe aware ofthetremendousprogressbeingmadeby Congress inHelsinki1949,wheretheybecame foresters whoattendedtheWorld Forestry first wastheinfluenceofseveralprominent genetics andtreeimprovementinthe1950s.The provided theimpetusforrapidexpansionof day. According toKaufman (1961),twoevents research andtechnologytransfertothepresent force inforestgeneticsandtreeimprovement tree improvement.Ithascontinuedtobeaguiding research anddevelopmentinforestgenetics tofoster Improvement Committeewasformed toasorchards. referred seed productionareasinloblollypine,whichhe methods. Thispromptedhimtoestablishthefirst collecting becauseofthestudent’spreferred dysgenic selectionwouldresultinpoor-quality work,Easlyconcludedthat the of Dorman‘s rather thanthesawtimberhewascutting.Aware treeswithlotsofconesonthem, short, scrubby The studentslatertoldhimthattheypreferred log operationsandsellthemtotheStatenursery. tocollectconesfromoneofhissaw- permission with Westvaco, gavesomehighschoolstudents genetic variation. demonstrating theexistenceofindividualtree pines establish thefirstprogenytestsinsouthern seedlings fromtheseselectionswereusedto high gumyield.Open-andcontrolled-pollinated FL, startedselectingslashandlongleafpinefor working attheresearchstationinLakeCity, Power Project(Kaufman1961). the plantingwasfloodedbySantee-Cooper Substantial inherentdifferenceswerenotedbefore (Forest ResearchStation]. Southern Service), In 1951, the Southern ForestIn 1951,theSouthern Tree Around 1949,L.T. Easly(1953), aforester andSchopmeyer,In 1941,Mitchell,Dorman, held every other year. The proceedings of the Carolina seed sources have been planted conferences are major sources of information extensively in Arkansas, where they outgrow in genetics and tree improvement, as is evident the local sources. in the literature cited for the present chapter.2 It was assumed, based on the loblolly results, One product of the first conference was the that east-west differences would be important establishment of a subcommittee, headed by Phil in longleaf and shortleaf pines, because they Wakeley, to install the Southwide Southern Pine also occur on both sides of the Mississippi River. Seed Source Study (SSPSSS), one of the most Recent analysis has shown that this is not so, and comprehensive provenance tests ever established. the latest seed-movement guidelines (Schmidtling The results from Wakeley’s (1944) first test 2001) stress the importance of minimum were dramatic, but the study was planted only temperatures in seed transfer considerations at Bogalusa, LA. The local seed source from for these two species. Livingston Parish, LA, was clearly the best not Wise use of information about geographic only for growth but also for disease resistance. 99 variation has resulted in large increases in The SSPSSS, on the other hand, was much southern pine productivity. Further increases more comprehensive. It was a very large have been realized through breeding. Forest tree undertaking, involving many cooperators across breeding in the South started in earnest with the the Southeastern United States who collected formation of the tree improvement cooperatives seed and provided planting sites. All four major in the 1950s, with the main emphasis on pines. southern pine species were included—loblolly, The first cooperatives evolved in the early 1950s 10. Chapter slash, longleaf, and shortleaf (P. echinata Mill.) out of research programs at the University of pines. A total of 128 plantations were established, Florida (headed by T.O. Perry) and at the Texas including seed from and plantations in 16 States, Forest Service (headed by Bruce Zobel). Zobel ranging from New Jersey and Pennsylvania south moved to North Carolina State University in to Florida and west to Texas, Oklahoma, and 1956 to form the third and the largest of the tree Missouri (Wakeley 1961). improvement cooperatives that exist today. The results of the SSPSSS and some other

Current Status Improvement and Tree Genetics more limited provenance tests showed that the Productivity improvements from genetics have local seed source was not always the best source. helped to make investments in intensive forestry Seed sources from warmer climates tended to very profitable throughout the world. In regions grow faster than local sources, if the warmer such as the Southeastern United States, managers climate sources were not moved to areas with of facilities for wood-based facilities climates greatly unlike those where they have realized that their future depends upon a originated. Unlike the other southern pines, reliable, ecologically sustainable, and economically loblolly has important east-west differences. affordable supply of wood. Plantations of Seed sources from west of the Mississippi River genetically improved forest trees are critical to are slower growing but more resistant to disease maintaining this supply. In the South, > 1 billion and tolerant of than sources from east of loblolly pine seedlings are planted each year, the Mississippi. Sources from just east of the river, and nearly every seedling is a product of a tree centered at Livingston Parish, LA, combine the improvement program. Because of the economies rust resistance of the western sources with the of scale, even modest genetic gains are worth faster growth of the eastern sources. Results of millions of dollars to industrial landowners, and this study led to large-scale transfers of seed to the small landowner benefits as well. Even increase productivity. Disease-resistant Livingston through only one generation of improvement, Parish, LA, seed was widely planted in locations gains have been substantial. For first-generation to the east. For example, much of this seed was loblolly pine and slash pine, volume, stem quality, planted in Georgia, where disease had caused and disease resistance have been improved, and losses in productivity. Fast-growing coastal the gain in harvest value is estimated to be 15 to 20 percent over unimproved trees (Hodge and others 2 Copies of proceedings of the Southern Forest Tree 1989, Talbert and others 1985). Estimates from Improvement Conferences are available from the National the second generation of improvement in loblolly Technical Information Service, 5285 Port Royal Rd., pine are even more encouraging. Additional Springfield, VA 22161, 800-553-6847 or 703-605-6000, fax 703-605-6900, [email protected]. Southern Forest Science: 100 Past, Present, and Future Productivity in the short term by breeding only the very best bybreedingonly the very in theshortterm populations, financial benefitscanberealized 1993, Whiteandothers1993). Intheelite 1989, McKeand andBridgwater 1998,White selected elitebreedingpopulations (Cotterill populations withintensively managedand to supplementtraditionalmainline breeding improved genotypes.Ageneraltrendhasbeen sufficient sizeanddiversitytoprovidenew through time,thebreedingprogrammustbeof deployment program,andtosustaingeneticgains others 1996). world (Balocchi1997,Carson1996,Walker and in otherpineregenerationprogramsaroundthe and others1997)havebeenusedsuccessfully developed intheSouth(Bramlett1997,Goldfarb for mass-producingfull-sibseedlingsarebeing vegetative propagation.Pollination methods seed andthebulkingofthesefamilieswith sib familiesarethecost-efficientproductionof profitability. Limitationstoutilizingthebestfull- have moreoptionsforincreasingproductivityand regeneration (Liandothers1999),foresterswill realized ifthebestfull-sibfamiliesareusedfor is necessary. Becausemoregeneticgaincanbe suchascoldtolerance environmental concerns areas whereadditionalselectionintensityfor impact onforestproductivity, especiallyin sib families(Bramlett1997)willhavesignificant being pursued.Massproductionofselectedfull- the geneticqualityofplantingstockarealso sites (Liandothers1999). generation familiesaredeployedtothebest greater gainsareexpectedwhenthebestsecond- practices (McKeand andothers1997).Even best sitepreparationandnutritionmanagement first-generation programsinconjunctionwiththe by utilizingthemostresponsivefamiliesfrom 30 percentmorewoodcanbeproducedperhectare increase productivity. Itisestimatedthat20to advanced geneticmaterialwilldramatically silvicultural techniqueswithuseofthemost knowledge ofsoilproductivityandoptimal have increasedgreatly. Combiningathorough and others1997),theoptionsavailabletoforesters silvicultural manipulation(Allen2000,McKeand in forestproductivityfrombothgeneticsand in thefirstgeneration(Liandothers1999). quality shoulddramaticallyexceedwhatwasseen percent forroguedorchards,andimprovementin average 7percentforunroguedorchardsto18 productivity gainsoverthefirstgeneration A breedingprogramisthebackboneofany Deployment optionsforfurtherincreasing Because ofthesubstantialimprovements Early Work TREE IMPROVEMENT SOUTHERN HARDWOOD productivity throughgenetics. foundation ofthesuccessfuleffortstoimprove and others1992),thisvariationisthe compared tootherplantsandanimals(Hamrick highlevelsofgeneticvariation generally havevery domesticated inthepastfewyears.Forest trees species thatarebeingbredhaveonlybeen undomesticated populations,andthosefew Most foresttreespeciesremainaswild compared tootherplantandanimalbreeders. have auniqueresponsibilityandopportunity objective.Treeresources isaprimary managementofgenetic where thelong-term replacements for, largerbreedingpopulations populations arecomplementsto,andnot is dramaticallyincreased. generations cyclefaster, andthegainperyear genotypes. Fewer treesarebred,sobreeding ( the breedingofwalnuts( involved inthiswork.Thisprogramincluded divisionoftheTVAwhen theforestry became studies intheSouthdatefromspringof1936, widely distributednaturalstands.Theearliest provenance trialsandsamplecollectionsfrom E 1973), andsycamore ( oak ( oak ( red other hardwoodspecies,including northern and Windham 1999). Studiessoonfollowedfor United Statesexpectedinthe mid-1980s(Tibbs mitigate ashortageintimber resourcesinthe initiated atreeimprovementprogramtohelp were established.At thistime,theForest Service (Farmer andWilcox 1966,Maisenhelder 1961) ( cottonwood ( styraciflua 1961),sweetgum( Thorbjornsen (Farmer andothers1967,Kellison 1965,Lotti1955, trials ofyellow-poplar( 1938, Wakeley 1975).Inthe 1950s andearly1960s, withdesirabletimber quality(Schreiner orother productivity andqualityofnuts,acorns, virginiana pseudoacacia triacanthos Carya Quercus These elite,intensivelymanagedbreeding arly studiesintheSouthconcentratedon in growthandwoodpropertiesbymeansof establishing geographicvariationpatterns Q. falcata Q. rubra spp.),chestnuts( spp.),honeylocust( L.)asameansofcombininghigh L.)(Webb 1964),andeastern L.),blacklocust( Populus deltoides L.)(GallandTaft 1973),cherrybark L.),andpersimmon( var. pagodifolia Platanus occidentalis Liriodendron tulipifera Castanea Juglans Robinia Gleditsia Bartr. exMarsh.) Ell.)(Randall Liquidambar spp.),hickories spp.),oaks Diospyros L.) L.) (Land 1981, Webb and others 1973). By 1983 at leaf rust resistance than local clones. Many least 27 hardwood species had been considered for of the cottonwood clones developed at Stoneville tree improvement, and collections had been made remain the backbone of plantation and breeding for most of these (Purnell and Kellison 1983). programs today. Unlike southern pines, no one species or small Hardwood cooperatives were organized group of species is suited to the various site types somewhat later than the pine cooperatives. The throughout the South, because hardwoods are very HRC began in 1963 with a combined program site specific. Understanding site specificity is of intensive tree improvement and less intensive essential to understanding and realizing genetic management of natural stands (Young 1996). gain in hardwoods. However, the absence of Sweetgum, sycamore, yellow-poplar, green ash economy of scale greatly limits the ability to (Fraxinus pennsylvanica Marsh.), and water oak/ develop a viable genetic program for most willow oak (Q. nigra L./Q. phellos L.) received hardwood species. most of the attention during the early years Three early programs stood out for their because of their commercial importance across a 101 longevity and contributions to hardwood genetics. majority of the Southern United States. Initially, a These programs were established by the Forest selection index was used to identify phenotypically Service, Southern Forest Experiment Station; superior trees, which were then grafted into clone the North Carolina State University Hardwood banks and seed orchards with the oaks established Research Cooperative (HRC); and the Texas in seedling seed orchards. In 1972, region-wide

Forest Service. The Southern Forest Experiment progeny testing was initiated by the HRC (Anon. 10. Chapter Station’s program of hardwood tree improvement 1999). Open-pollinated seed from phenotypically began in the early 1960s at the Southern average or better than average sweetgum, Hardwoods Laboratory located in Stoneville, sycamore, water oak, willow oak, and black walnut MS. Sweetgum, cherrybark oak, sycamore, and (J. nigra L.) were collected from natural stands eastern cottonwood were studied initially, and throughout the South. The modified selection other species added in the late 1970s and early scheme was used because the index system proved 1980s just prior to the closing of the hardwood inadequate for identifying genotypically superior project in 1982 (Ferguson and others 1977, Mohn southern hardwoods in natural stands (Purnell Genetics and Tree Improvement and Tree Genetics and others 1970). Eastern cottonwood, probably and Kellison 1983). the most intensively studied hardwood species in In 1971, the Texas Forest Service’s the South, was the subject of testing from 1965 Western Gulf Forest Tree Improvement through 1980. Early tests indicated that local Program formally added the Hardwood sources were superior to earlier introductions of Cooperative Tree Improvement Program to European hybrids (Maisenhelder 1970). Testing their existing pine program (Byram and Lowe eventually resulted in the release of the first and 1995). To date, 17 species-site trials and 188 open- only certified genetically superior cottonwood pollinated progeny tests have been established clones in the country (Land 1974). Subsequently, with nearly 1,500 families (Byram and others collections were made from natural stands 2000). After 20 years, sycamore, sweetgum, and throughout the lower Mississippi River Valley, green ash tests indicated that family differences from coastal areas from North Carolina to were significant, but there were neither consistent Texas, and from other programs as far north as provenance effects nor any meaningful genotype x Minnesota. Large clonal tests were established environment interactions for hardwood species in with industry and university cooperators in the southern Coastal Plain (Byram and others Arkansas, Illinois, Kentucky, Louisiana, and 1998). A slight indication was found that sources Mississippi. Clones suitable for use in various from the western edge of the species range are portions of the Mississippi River Valley were slower growing. Families that performed well identified, and data collected on vegetative across the region could be identified as early propagation, controlled pollination, disease as age 5 or 10. resistance, architecture, and selection strategies provided excellent information Current Status for industry and university programs to build A survey of State tree improvement personnel upon (Cooper and Ferguson 1979; Cooper and indicated that most Southern States currently Filer 1976, 1977; McKnight 1970). In general, have hardwood tree improvement programs, and clones originating up to 200 miles south of the almost half are active members of one of the two plantation sites grew faster and had greater hardwood cooperatives. Arkansas, Louisiana, Southern Forest Science: 102 Past, Present, and Future Productivity butternut ( butternut chestnut [ threatened byintroducedpestssuchasAmerican species thataredifficulttomaintainor will relyonseedlingseedorchards.Hardwood have artificialregenerationprograms,andthese redoakandwhite( northern policy,Windham 1999).Undercurrent only longer justifiedforFederal lands(Tibbsand intensive, pineimprovementprogramsareno and managementprogramshavebecomeless planted annually. Asrotationshavelengthened have subsequentlyreducedthenumberofacres and have reducedthenumberofacresharvested the last15years.Thisismainlybecausenewlaws dramaticallyover in theSouthhaveshifted increase. correspondingly and demandforimprovedseedlingswould hardwood plantingcouldincreasesubstantially, the extensionofeligibilitytoadditionallands, and iftheseprogramsareexpandedthrough cost-share programs(Byramandothers2000), is highnowforhardwoodseedtosupportFederal nonindustrial privatelandalmostentirely. Demand bottomlandhardwoodson planting ofsouthern Program,drive Reserve e.g., theConservation production. Federal cost-sharingprograms, to wildlifethanfromitsimportancefiber sometimes resultsmorefromitsimportance Justification forresearchonaparticularspecies programs, butotherspecieshavebeenadded. importanceinboth sweetgum areofprimary membersoftheHRC.Sycamoreand currently Program. NorthCarolinaandSouthare with theWestern GulfForest Tree Improvement Mississippi, andTexas benefitfromtheiraffiliation Westvaco (nowMeadWestvaco) probably hashad in thePacific Northwestand aroundtheworld. including theinterspecifichybridization programs programs, thebasisforseveralcurrent form Experiment Stationandthe Texas Forest Service ForestClones developedbytheSouthern programs tomakesignificant advancements. techniques forcontrolledpollinationhaveenabled abundant seedproduction,andestablished in theSouth.Easeofvegetativepropagation, probably moreadvancedthanthatofanyspecies intheseprojects. Service Forestry CommissionarepartnerswiththeForest The UniversityofTennessee and theGeorgia major focusofmoreprograms(McCutchan1999). becomesa Windham 1999)asgeneconservation florida Tree improvementeffortsonFederal land Genetic improvement of eastern cottonwoodis Genetic improvementofeastern L.)receivespecialattention(Tibbsand Castanea dentata J. cinerea L.), anddogwood( (Marsh.)Borkh.], Q. alba L.)will Cornus populations, something thathasbeenavoided in necessitated therebuilding oftestingandbreeding wavering haslimitedgains, mainlybecauseithas replaced byproblemsofgreater importance.This or whentheperceptionofa hardwoodshortageis dollars tighten,whenrawmaterial costsdecrease, be closedwhendemandlessens,research programs havebeenintensiveattimesonlyto but throughouttheUnitedStates.Numerous improvement effortsinnotonlytheSoutheast still accuratewhensummarizinghardwoodtree for meaninganddirection.”Thesewordsare improvement asa“haphazardthing,searching in 1975whenhecharacterizedhardwoodtree single-species focus.McKnightrecognizedthis a unifiedapproachorthebenefitsofhaving hardwood treeimprovementhasgenerallylacked hemicellulose andauxin. projects aimedatincreasingproductionof (Anon. 2002).Thiseffortisalreadydeveloping Populus genomic sequencingworkthatisbeingdonewith Populus University ofWashington, especiallyinthegenus Poplar MolecularGeneticsCooperative atthe Cooperative atOregonStateUniversityandthe at theTree GeneticEngineeringResearch will alsobenefitfromworkbeingaccomplished products inanumberofspecies.TheSoutheast possibilities forcommercializingtransformation Paper).Carolina (International of Florida),Alabama(BoiseCascade),andNorth Missouri (MeadWestvaco), Florida(University States andclonetestshavebeenestablishedin United made fromthroughoutSoutheastern State University. Newseedcollectionshavebeen and testingprogramsareactiveatMississippi Program(Landandothers2000).Breeding clones fortheSoutheastaspartoftheirBiomass sponsoringresearchtodevelop currently are targetingthesesitesfortheirspecificneeds. mills.Improvementprograms various southern investigated asasourceofhardwoodfiberfor and fertilizedplantationsystems)arebeing breeding population.Today, (irrigated fiberfarms aviable deployment population,andconstructing realized gains,establishingageneticallydiverse the 1980s.Thesewereaimedatincreasing progeny testswereestablishedthroughout closure oftheStonevilleproject.Bothcloneand the mostconsistentcottonwoodprogramsince Unlike southern pinetreeimprovement, Unlike southern Venture companiesareexploringthe The U.S.DepartmentofEnergy(DOE)is , whichisbeingfundedthroughtheDOE . Themostexcitingefforttodateisthe Populus the continuous pine tree improvement programs obstacle to success is maturation. As seedlings of of the South. Several major factors contribute to these species that are difficult to mature, they the unique aspects of hardwood tree improvement; undergo many morphological and physiological these include the number of species, their site changes. One important trait that changes is the sensitivity, and their infrequent occurrence in ability of severed stems to form adventitious . even-aged monospecific stands (Land 1975). For these species, rooting of cuttings collected from very juvenile seedlings will often be high As with past programs, current hardwood (> 80 percent), but rooting success of cuttings programs face a lack of long-term funding because from open-grown trees typically drops to almost hardwood furnish is perceived to be low in cost and zero over a period of 2 to 10 years. accessible even though numerous southern mills are reaching further for their hardwood fiber In many species, juvenility (the ability to form supply. Even though large amounts of hardwood adventitious roots and rapid growth of rooted fiber are needed to sustain these mills, little has cuttings) can be maintained for several years been invested in research to develop low-cost through severe (hedging) of stock 103 hardwood fiber sources that would provide to produce cuttings for rooting (Goldfarb and substantially higher yields than natural stands others 1997, Rowe and others 2002). Cuttings can do, and in less time. Industry funding has become be rooted at high frequencies even when taken even more restricted with the recent downturn from hedged loblolly pine that is several years in the paper industry. The funding crunch is also old (Cooney and Goldfarb 1999). Rooted cuttings affecting long-term cooperatives through mergers of this type grow as rapidly as seedlings from the 10. Chapter and the capitalization of the supporting land base same families (Frampton and others 2000, Stelzer that is thought to be nonstrategic to a specific and others 1998). mill. Today’s industrial programs are faced with Other strategies exist for maintaining juvenility a need to develop plantation schemes that will until clones can be selected and multiplied. One meet return-on-investment demands and build strategy employs establishing clone trials from programs focused on one or two species that stock plants while maintaining juvenility of the are adapted over a range of sites throughout stock plants through selection age. A possible the South. Genetics and Tree Improvement and Tree Genetics

modification could include establishment of clones as axillary cultures and maintaining the THE FUTURE OF TREE IMPROVEMENT cultures at temperatures that are low but above IN THE SOUTH freezing to delay maturation. any new tools are available to aid in efficiently manipulating the genes of A second strategy being pursued consists of M forest trees. While traditional methods initiating somatic embryogenic cultures from of quantitative genetics have been very candidate seeds. The cultures would be divided effective, they can be enhanced with emerging to generate somatic seedlings for clonal field tests technologies. There are exciting new possibilities while the remaining portions of the culture would for improvement through advances in be placed in liquid nitrogen for cryopreservation. biotechnology that allow incorporation of genes When superior clones have been selected, for traits such as herbicide resistance, insect preserved cultures could be recovered, multiplied, resistance, increased cold tolerance, modified and used to generate somatic seedlings for lignin, and growth. A requisite first step to . For the southern pines, all of these applying biotechnology to plantations is the ability steps have been achieved, but there are limitations to vegetatively propagate selected clones. Rooted in the efficiencies of each step in the process. cuttings of many hardwood species and fewer Also at this time, only a relatively low percentage have been used in intensive forestry of genotypes (families and clones) can be practices for decades and in a few situations successfully propagated through all the steps. for centuries. Classic examples include willows Ultimately, the strategy most likely to be (Salix spp.), poplars, and sugi (Cryptomeria employed widely will be the one with the lowest japonica D. Don), which has been clonally cost per genetic gain delivered. Both technologies, propagated for > 1,000 years and used in though possible on a research scale, still require plantation forestry in Japan since around A.D. further development on an operational scale, so it 1400 (Toda 1974). Unfortunately, most conifers is difficult to precisely predict gains and costs. and certain recalcitrant hardwoods have not been Perhaps the ideal system would comprise elements clonally propagated successfully. The primary of both technologies. That is, clones would be Southern Forest Science: 104 Past, Present, and Future Productivity (Hill exMaiden) inBrazilproduce70m beendramatic. Thebestclonesof often recalcitrant hardwoodswill likelybecomeareality. pinesand forsouthern clonalforestry arrested, lost. Ifmaturationcanbereversed oratleast opportunity forspecificgenecombinationstobe occurs whenclonesarepropagated,thereisno be utilized.Becausenosexualrecombination the fullgeneticpotentialofpopulationcan specific clonesofanyagetreecanbepropagated, not possiblethroughconventionalbreeding.When Stettler andothers1988),providesadditionalgains in temperateregions(e.g.,LiandWyckoff 1993, (Zobel andothers1987),with Eucalyptus Eucalyptus more easilypropagated sitesthan widely adaptableforuseonsouthern Gocke andothers2001).Sweetgumwouldbemore poor shootgrowthfollowingrooting(Anon.2001, of sweetgum,however, hasbeentemperedby Recent successinbothrootingandsurvival 1995;Robisonandothers1999). Rieckermann times(Anon.1998,1999,2000; storage methods,basalauxintreatments,and focused onoptimizingthecollectionofcuttings, University sincethemid-1990s.Effortshave has beenongoingatNorthCarolinaState of asexualpropagationtechniquesforsweetgum the mid-1970s.Thedevelopmentandrefinement ongoing projectattheUniversityofGeorgiasince others 1997).Sweetgumpropagationhasbeenan via staminateinflorescencetissues(Merkleand 1985) hasledtothepropagationofmaturetrees (Sommer andBrown1980,Sommerothers Pioneering workattheUniversityofGeorgia sources frommaturetreestoinitiatecultures. explant to certainspecies,utilizesalternative in thenearfuture. pines of someclonalsystemforthesouthern landowners, willresultinthedevelopment the widespreadinterestofmanyindustrial with thepotentialgeneticgainsavailableand that researchadvancesinrecentyears,together and strategicuncertainties,itappearslikely for reforestationstock.Despitetechnological large-scale, low-costproductionofrootedcuttings intostockplantsfor seedlings couldbeturned Once selected,amoderatenumberofsomatic and clonallytestedwithsomaticseedlings. cultures,cryopreserved, started asembryogenic Productivity increases from clonal forestry have Productivity increasesfrom clonalforestry True asispracticedwith clonalforestry A thirdstrategy, whichmayonlybeapplicable speciesinmanytropicalcountries species. Populus , Salix, Populus 3 or E. grandis /ha/year, species common (Strauss andothers1992).Inthe future, 1994), anditisunlikelythat thissituationis member ofthepopulation(O’Malley andMcKeand marker-trait associationbe thesameineach disequilibrium iscommonin apopulationwill associations inotherparents. Onlyiflinkage desirable traitsinoneparentwillhavedifferent likelythatmarkersassociatedwith It isvery association withfieldtrialsisevenmoreexpensive. themarker-trait are expensive,anddetermining breeding programs.However, molecularmarkers traditional selectionmethodsinsomeelite Marker-assisted selectionwilllikelysupplement Williams andByram2001,Wu andothers2000). and others2000,O’MalleyMcKeand 1994, (Bradshaw1996,Johnson is notstraightforward economic trait. associated withthelocusorlocicontrolling been identifiedusingDNAmarkersthatare volume production(Kayaandothers1996)have gravity ofwood(Grooverandothers1994), resistance (Wilcox andothers1996),specific loblolly pine,forexample,majorgenesdisease in controllingeconomicallyimportanttraits.In collaborated toidentifygenesthatareimportant Already moleculargeneticistsandbreedershave to increasewiththehelpofmoleculargenetics. will bedeployedhasincreasedandcontinue of methodstoaffectthetypepropagulethat directly impactforestproductivity. Thenumber stock istheonlyopportunitybreedershaveto pines. pursuing asimilarstrategyforthesouthern UnitedStatesareactively the Southeastern and Chile(Balocchi1997).Severalcompaniesin plantation programsinNewZealand,Australia, Don andhashadmajoreconomicimpacton has becomeoperationalwith that havedemonstratedprovenperformance (Tuskan 1997). byproducingindividualelitegenotypes improvement approachtoonethatwillcapture species, breedingwilladaptfromapopulation becomespracticalinmore As clonalforestry by averageseedlings(Stettlerandothers1988). are >100percentbetterthanthoseproduced P. trichocarpa realized. Thebestclonesfromhybridcrossesof Northwest oftheUnitedStateshavealsobeen Similar benefitsforhybridpoplarsinthePacific half thismuchvolume(Zobelandothers1987). whereas unimprovedseedlingsproduceonly Using marker-traitassociationseffectively Deployment ofgeneticallyimprovedplanting Multiplication ofspecificfull-sibfamilies x P. deltoides produceyieldsthat Pinus radiata D. if the investment is made to map genotypes “Nature Biotechnology” (volume 20, number 6) of all parents in an elite , the was devoted to various aspects of the use of incremental cost of using the markers for selection GM crops. in both breeding and deployment populations could be reduced. Again this promising technology CONCLUSIONS awaits improvement in cost efficiency (Johnson enetic tree improvement and plantation and others 2000). management has had and will continue to Molecular geneticists’ greatest contribution to G have a positive impact on forestry and forest tree improvement may be a better understanding management worldwide. The demand for forest of the processes of wood formation and growth. products will continue to increase, and intensive With knowledge about processes such as lignin management will be needed to meet this demand. biosynthesis (e.g., MacKay and others 1997), Plantation management of fiber farms can also molecular geneticists hope to manipulate the alleviate pressure on ecologically sensitive forests process to make pulping more efficient (e.g., and provide year-round accessibility to wood. Tree 105 Dimmel and others 2001). Genetic engineering, or improvement can best promote the conservation the insertion of foreign genes into the genome of a of forest ecosystems by providing high-yielding, desirable clone, has been realized in forestry. In adaptable planting stock for these fiber farms. species in which tissue culture via organogenesis Tree breeders must be cautious in the use of or embryogenesis is feasible, insertion of genes the genetic resources in breeding populations. The has great potential. One of the major factors that rich genetic variation in most tree improvement 10. Chapter will hamper hardwood molecular biology programs programs is an endowment that must be skillfully is the lack of highly sophisticated conventional managed. Fortunately, breeders have learned to breeding programs for most species. manage populations both for short-term financial Advances in mapping and transformation benefit and long-term conservation of genetic have been more rapid in hardwoods than in the variation. The future of tree improvement for pines because of their relative ease of culture both pines and hardwoods is bright, with more and manipulation. Indeed, various Populus species challenges, more available tools, and more

opportunities for gain than ever before. Improvement and Tree Genetics and sweetgum have become model species for industrial and cooperative biotechnology programs. This is even more evident with the LITERATURE CITED recent announcement of a project to sequence a Anon. 1998. Thirty-fifth annual report of the hardwood Populus clone (Anon. 2002). Development of research cooperative. Raleigh, NC: North Carolina State University, College of Forest Resources. 38 p. molecular resistance to more environmentally friendly herbicides would reduce establishment Anon. 1999. Thirty-sixth annual report of the hardwood research cooperative. Raleigh, NC: North Carolina and early rotation maintenance costs that have State University, College of Forest Resources. 41 p. plagued hardwood plantations. This possibility Anon. 2000. Thirty-seventh annual report of the hardwood has tremendous potential, and transgenic tests research cooperative. Raleigh, NC: North Carolina State throughout the United States are providing University, College of Forest Resources. 15 p. insights into it. While this trait alone would allow Anon. 2001. Thirty-eighth annual report of the hardwood for a tremendous increase in hardwood plantation research cooperative. Raleigh, NC: North Carolina State acreage in the South, the addition of other University, College of Forest Resources. 62 p. characteristics, such as reduced lignin content, Anon. 2002. Researchers develop poplar “parts list”: would provide even more impetus. Department of Energy effort will help scientists use trees more efficiently. The Forestry Source. 7(4): 13. It is unlikely that transformed [genetically modified (GM)] trees will be widely deployed Allen, H.L. 2000. Silvicultural treatments to enhance productivity. In: Evans, J., ed. The forests handbook. Oxford, until the negative public perception of their use UK: Blackwell Science Ltd. [Not paged]. Chapter 6. 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