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Genetically modified poplars in China Song, Xiao 2013

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GENETICALLY MODIFIED POPLARS IN CHINAA situation analysisXiao SongSpring 2013? 1Levitan, Isaak Iliich. 1888TABLE OF CONTENTSGenetica?y Modified Poplars in China? 4Abstract? 41. Introduction? 51.1 Background? 51.2 Taxonomy, Distribution, Basic Botany and Molecular physiology of poplars? 72. Experimental approach towards poplar breeding? 92.1 The genome sequencing project and genetic maps of Populus species? 92.2 Current commercial breeding objectives and pertinent breeding approaches? 103. Genetica?y Modified poplars? 123.1 Evolutionary background and phylogenetic relationship with its related wild / cultivated species? 123.2 Why do Chinese foresters create and release GM poplars?? 133.2.1 Modification of wood production? 143.2.2 Abiotic Stress Tolerant? 153.2.3 Biotic Disturbance resistance? 163.3 Impacts and concerns in both long- and short-terms? 173.3.1 Genetic contamination? 173.3.2 Ecological pressure? 193.3.3 Food and feed safety? 203.4 Status quo of GM poplars in China? 214. A proposal of ?What we can do before it?s too late?? 214.1 Transparency? 214.2 Develop we? established risk assessment and regulation system? 224.3 Do not become too relied on genetic engineering? 24? 24.4 Approaching the problems through ?Traditional breeding? of poplars? 244.5 A prospect? 25Conclusion? 26Appendix I? 27Appendix II? 30Appendix III? 34Appendix IV? 46Appendix V? 47Bibliography? 48? 3GENETICALLY MODIFIED POPLARS IN CHINAA situation analysisXiao SongSpring 2013Abstract    China has vast areas of poplar plantations serving as wind shelter, erosion control facility and industry resource. The intensive utilization of clonal forestry with its minimal genetic diversity has aroused serious pest infestation. To solve this problem and ultimately eliminate insect-caused losses, genetically engineered pest-resistant poplar has been introduced in a large scale planting. This made China the first and only country allowing genetically modified (GM) trees to be re-leased into open environment.        Images of Populs spp.    However, the long life span of trees is likely to increase the chance in detecting transgene in-stability  and increasing the danger to biodiversity, especially genetic diversity. It should be high-lighted that the open-pollinated mating system of poplar would speed the gene dispersal of these GMO genotypes and issues related to potential environmental consequences and biosafety issues caused by gene flow and transgene escape need to be addressed in a comprehensive manner. In this article, I will analyze the condition of GM  poplars released in China, review the major con-cerns and raise some proposals on how to eliminate the likelihood of transgene escape under the current situation. In my perspective, a prudent approach that considers the consequences of re-leasing GM  trees, large-scale commercialization with a monitoring and risk assessing system is preferred, and corrections should not be hesitated to be made.Key Words: Poplar; Genetic modification; Genetic diversity; Genetic Contamination? 41. Introduction1 . 1  B A C K G R O U N DForest harbours a great  amount of the planet?s biodiversity  while serving significant ecological, social and economical functions, without which neither the ecosystem nor the social construction could last. During the industrialisation and population booming, China has experienced serious deforestation in the recently  passed decades (Ewald et al. 2006). Poplar, with certain advanced characters against other tree species, majored the gigantic afforestation project in China, during which the massive plantation of artificial forests constructed with excessively used tree species cost severe pest infestation: 23.7% of the total forest plantation were under biotic disturbance resulting in an economic loss approaching 1 billion dollar (Ewald et  al., 2006).  In searching for the solution that would hopefully solve the problem efficaciously forever, Chinese forestal re-searchers employed the star of the biotech era ? Genetic Modification. Thus, in the early 1990s gene transformation targeting trees within the Populus genus prevailed in China as well as across the world, and the goals were not limited within biotic disturbance resistance, but extended into aspects like environmental stress tolerance, wood quality  modification and growth alternation (Tian & Tan, 2009).As widely spread genus, Populus has an impressive natural distribution that covers from tropical to sub-polar climate zones in the Northern hemisphere and provides habitats for local and migrat-ing wild lives as well as insects and micro-organisms, serves as air exchanging agents, water cy-cle tache and ecosystem holders. It  also embraces great heterogeneity and includes many long cultivated and intensively  used tree species across the world, which is both a virescence material, an industrial raw material and a conservation tool (Hu et al., 2010). Poplars were broadly planted world-wide for wind shelters, erosion control / water-soil conserva-tion, phytoremediation, landfill covers, biofuel production, pulp and logs (Acker et al. 2011; Marmiroli et  al., 2011; Zalesny & Bauer, 2007). Meanwhile, favoured by their simple clonal propagation, relatively rapid growth rate and considerably small genome size among woody spe-? 5cies, they are one of the major model plants used in both scientific and industrial forestal re-search (Bradshaw et al., 2000; Polle & Douglas, 2010).China, with a rich flora of the genus and the biggest crop of poplars through the globe, has been using poplar plantation as an efficient approach several environmental and social issues arose along the industrialisation of the country  (Weisgerber & Han, 2001). Historically, poplars have been closely associated with human civilisation and extensively  utilised in agroforestry/silvopastoral systems on the land for hundreds of years, resulting in the overall present distribu-tion of poplars, including native species, to be considerably transformed from its natural distribu-tion (Sigaud, FAO). Hybrid clones are widely planted in China for their various functions men-tioned above. One of the marked purposes lays in the protection against wind and desertification, poplar is one of the major material constructing the Three-North Shelter-belt, a massive shelter-belt grid horizontally across North China covering a 4480 km dimension east to west reserving planting area over 25 mil. ha., Figure 1-1.), while in the eastern provinces of the country  the planting aims at commercial wood and biomass production (Sigaud, FAO). In the major affores-tation programmes in China, poplar is estimated to occupy 60% of the total tree planting area (National Poplar Commission, 1996) and 80% of windbreak shelters of the Three North have been established with poplars (Sigaud, FAO). By 2006, artificial plantation area of poplars has exceed 7 million hectare in China, which is about 19% of its total artificial forest  area (Lu & Hu, 2006), 5% of the total forest cover (Ewald, et al., 2006) and is steadily  increasing. It is predicta-bly hard for such enormous scale of artificial plantation constituted with clones from limited cul-tivars to perform well under the stress of insects and diseases. After witnessing great  mortality under biotic disturbance, Chinese foresters took GM as a possible solution to eliminate the eco and commercial loss and overcome China?s lack of pest resistant  poplar germplasm resources (Hu et al., 2010), however, whether there is indeed a lack of pest resistant genetic resources re-mains to be discussed. The purpose of this paper is to interpret poplars breeding in China in an overall picture, given the situation of the rapid development in genetic modification and the al-ready  taken place commercialisation of GM  cultivars, and provide a preventive, as well as reme-dial insight through the issue. ? 61 . 2  T A X O N O M Y ,  D I S T R I B U T I O N ,  B A S I C  B O T A N Y  A N D M O L E C U L A R  P H Y S I O L O G Y  O F  P O P L A R S      The Taxonomy Lineage of poplars (Chao et al., 2009):          Kingdom: Plantae                Phylum: Angiosperms                      Class: Eudicots                            Order: Malpighiales                                   Family: Salicaceae                                         Subfamily: Populoideae                                                Genus: Populus    Populus is a genus of six sections (Leuce, Tacamahaca, Aigeiros, Turanga, Populus and Leucoi-des), a member of Salicaceae, which have been placed under the Malpighiales in the recent cla-distic analysis of the angiosperms, while various classifications still exist (FOC, 1999; Bradshaw et al. 2000; Sterck et al., 2005). It is naturally distributed through most terrestrial areas within the Northern Hemisphere and has a small representation in tropical Africa (FOC, 1999; Polle & Douglas, 2010). There are about 100 species worldwide, including species applied with various common names such as poplar, aspen, and cottonwood (FOC, 1999; URGI, 2010). China is among countries with a highly multifarious indigenous flora; based on its ample genetic variation of poplar species, there are germplasm resources with the conserved ability to survive, reproduce and settle in divergent habitats after long periods of adaptation processes (Weisgerber & Han, 2001). Out of over 100 Populus species found in nature, 71 species (47 endemic) are dis-tributed in China, including at least nine hybrids (FOC). Among them, 37 are distributed in North China (Sigaud, FAO, Table 1.), which have been intensively researched and utilised through the history of Chinese agroforestry. Meanwhile, comprehensive contemporary studies of the genus Populus looked into the mountain ranges of the Qinghai-Tibet Plateau , and uncovered  concen-trated genetic diversity of poplars in the subtropical mountainous regions of Southwest China: 3 sections, 17 species and 15 varieties have been recorded, described and taxonomically classified there. They grow within board altitudes between 1500 m and 4300 m above sea level. Many of these poplar sources are notable for their remarkable site adaptation potential in harsh habitats ? 7and vigorous growth under acceptable conditions (Weisgerber & Han, 2001). As summarised by Bradshaw et al. (2000), with the capability  of rapidly  invading disturbed sites, many poplar spe-cies occupy habitats in the dynamic environment of riverine floodplains, where they form a key component of riparian forests (Braatne et al., 1996). Others, such as the aspens, commonly colo-nise upland areas after intense, initialising fires (Burns & Honkala, 1990). Populus plants are deciduous broadleaf trees that can grow from 15 to 50 meters in height, with trunk diameters up to 2.5 meter (URGI, 2010). The majority species under the genus are dioe-cious with pendulous catkins formed by flowers of neither calyx nor corolla, which is adapted to wind pollination; the female plants produce tiny  capsules with filament around the bottom, a typical seed structure established for wind and water dispersal (FOC, 1999; Chao et al., 2009).  The heteromorphic plants? fertilisation method is typical chalazogamy, and they perform an obli-gate outcrossing mating system with self-incompatibility  mechanism and interspecific recogni-tion, thus inbred strains rarely occur and haplotypic polymorphisms were expected (Knox et al., 1972; Valda & Murray, 1981; Tuskan et al., 2006). Certain proteins in its pollen grain walls are essential for pollen germination and altering the interspecific incompatibility system, which de-termines whether pollen tubes develop sufficiently. This system lays barriers in the hybridisation between some poplar species, for instance, between the section Leuce and Aigeiros (Knox et al., 1972). Also, plants in Populus are all capable of reproducing asexually, often by sprouting from the root collar of killed trees or from detached branches that have been kept in moist condition and be-come embedded in the soil; some species propagate through sucker shoots that arise from hori-zontal roots, mostly after clear-cut and abiotic disturbance, especially fire (Bradshaw et  al., 2000; Ghazoul, 2004). This property of poplars would typically result in clonal stands up to a few hec-tares, and recurrent fires can maintain the generation of such clones for centuries (Bradshaw et al., 2000). Such eco-association with fire made it a good choice for regenerate and conserve fire damaged forest land. ? 8All species within this genus are diploids (2n=38) and can be breed for many fertile hybrids with highly  targeted characteristics that enrich the diversity of the natural germplasm and benefits the human society  (Marmiroli et  al., 2011). As suggested by  Marmiroli et al., the small size of the haploid Populus genome (ca. 480 to 550 Mbp, only four times that of Arabidopsis, and 400 times smaller than that of Pinus) has favoured the creation of 25 genetic maps and the development of various molecular resources in different species (Cervera et al., 2004; Tuskan et al., 2006; Mar-kussen et al., 2007; Gaudet et  al., 2008; Polle & Douglas, 2010), which forms an efficient com-plement to plant researches based on Arabidopsis, since many plant species found in nature are more similar to Populus than to Arabidopsis, life-historically and genetically (URGI, 2010).2. Experimental approach towards poplar breeding2 . 1  T H E  G E N O M E  S E Q U E N C I N G  P R O J E C T  A N D  G E-N E T I C  M A P S  O F  P O P U L U S  S P E C I E SThe genome sequencing of Populus trichocarpa conducted by Tuskan et al. (2006) is a milestone of forest sciences? successfully employing biotechnology, which opened doors and paved the way for molecular-scoped breeding and research on and around poplars. With the sophisticating biotechnical tools, the detailed interpretation of its genomic information and its favoured nature, Poplus has become a well accepted model system (Polle & Douglas, 2010). During the sequenc-ing, a wealth of biotechnics and several genomic databases are adhibited to draft the P. tricho-carpa genome, which enabled and facilitated the investigation of cellular and molecular mecha-nisms in long-lived forest trees by providing a thoroughly studied model system (Tuskan et al., 2006, Polle & Douglas, 2010).  The research group adopted whole-genome shot gun strategy for sequencing and assembling, and augmented it by constructing a physical map ?based on BAC restriction fragment fingerprints, BAC-end sequencing, and extensive genetic mapping based on simple sequence repeat (SSR) length polymorphisms? (Tuskan et al., 2006). In order to assemble as many of substantial frac-? 9tions derived from the shotgun reads as possible and assess the nature of the sequences in the fraction of the genome, the group proforem wu-BLAST searches against online databases (eg. NCBI, etc.). After that BAC clones were fingerprinted with an agarose gel based method and the BAC-end sequence were compared with the shotgun assembly through BLAST. With the linkage groups already discovered by previous researchers added in, the map was drafted (Tuskan et al. 2006). After getting the map, the research group constructed genome-wide pairwise DNA align-ments between Populus and assemblies of Oryza and Arabidopsis with VISTA pipeline infra-structure for detailed information. Thus, with following refinement, further prediction and anno-tation, whole-genome microarray  analyses, related RNA verification and statistic analysis, the millstone project that laid the foundation of transgenic tree breeding was carried out (some major results demonstrated in figures are attached in Appendix II). This initiative approach did not only answered the questions on how perennial plants are different from annual ones, what  makes a tree to have the unique biology and how should the future breeding of trees be conducted, but set a completely new agenda for forest research (Bhalerao et al., 2003).2 . 2  C U R R E N T  C O M M E R C I A L  B R E E D I N G  O B J E C T I V E S  A N D  P E R T I N E N T  B R E E D I N G  A P P R O A C H E SCurrently the breeding of poplars mainly aims at insect and disease resistance, environmental adaptation, biotic and abiotic stress tolerance, lignin and cellulose content modification, rapid growth with high biomass production, phytoremediation and aesthetic value for virescence (Hu et al., 2010; Marmiroli et al., 2011; Weisgerber & Han, 2001). The classical breeding pro-grammes are continued while molecular methods start to draw growing attention (Weisgerber & Han, 2001).For classical breedings, the major approaches are domestication of plants, deliberate crossing and targeting properties selecting, which relies on homologous recombination between chromosomes and mutants to generate genetic diversity that allows for desirable traits to occur (Kingsbury, 2009). Since we entered the biotech era, classical breedings are no longer limited in nurseries and fields; procedures could also take place partially for entirely  in the lab, benefiting from bio-? 10technics such as hormonal regulation, tissue culture, hydroponic culture, protoplast fusion and mutagenesis, etc. One of the major achievement in classical poplar breeding is the recognition pollen method developed for successful interspecific breeding. As mentioned previously, some species within the Populus genus are interspecific incompatible, thus one species? pollen might not sufficiently germinate on a stigma from another species even though they are within the same genus. To come across this barrier and breed hybrid poplar cultivars, conventional tree breeders used recognition pollen technique to overcome the barrier (Knox et al. 1972): by mixing viability reduced compatible pollens achieved by repeated freezing and thawing, gamma-radiation or chemical treatment into the viable incompatible pollens and bringing in the proteins that enables them to germinate, Knox et  al. obtained highly successful hybridisation from the cross P. alba x P. deltoides repeatedly.For modern breedings, molecular biotechnics are involved in enlarging the gene pool, desired trait selecting for desired traits and eventually  enhancing the efficiency of breeding (Kingsbury, 2009). The major approaches are marker assisted selection, reverse breeding, doubled haploidy and genetic engineering (Gepts, 2002, Kingsbury, 2009). With decades of endeavour of the sci-entists and breeders, molecular markers and genetic maps are available for most important crop plants and marker-trait association have been establish for a diverse array  of traits (Dwivedi et al., 2007), which provides information and visions for poplar breeding nowadays. Main attempts in genetic modification in poplars includes transfer of single genes into poplars and transforma-tion of combined multi-genes for targeted traits (Ewald et  al., 2006). The transferred sections came from a wealth of sources, from the bacteria to insect, and got engineered into certain poplar cultivars? gene pool with molecularized methods. The two most common transformation methods are Agrobacterium-mediated DNA transfer, and bombardment with DNA-coated micro-projectiles, so-called ?biolistic? transformation. By  the beginning of this century, transformation systems were further developed, but progress was mostly limited to a few poplar hybrids that were selected for ease of transformation. Nowadays, routine transformation procedures utilising A. tumefaciens or A. rhizogenes are conducted on most poplar species and hybrids even for re-calcitrant genotypes such as cottonwoods (Frankenhuyzen & Beardmore, 2004). ? 11Wu and Fan (1991) carried out the first gene transfer project in China inserting single Bt  genes into poplars and created anti-defoliator poplars, following which various of genetic engineering took place in China. Meanwhile, genetic modification of crop  plants, fruits and vegetables as well as trees are happening as a new way towards food security and biomass mass sufficiency to satisfy the world with booming population (Dwivedi et al., 2007). By now, genetically modified poplar cultivars have been processed to have many purposeful customised novel traits, which will be introduced in the following section. 3. Genetically Modified poplars3 . 1  E V O L U T I O N A R Y  B A C K G R O U N D  A N D  P H Y L O G E-N E T I C  R E L A T I O N S H I P  W I T H  I T S  R E L A T E D  W I L D  /  C U L T I V A T E D  S P E C I E SAlthough Populus has been cultivated and studied for a long time, the exact phylogenetic infor-mation about the genus is still under discussion; the classification sections was majorly relying on morphological, reproductive characters and interspecific crossability (Hamzeh & Dayanan-dan, 2004; Cervera et al., 2005): members of the same section can hybridise with each other naturally  or artificially (Zsuffa, 1975; Cervera et al., 2005). Classic taxonomic analysis, has been under great difficulties posed by high intraspecific diversity, wide natural crossability, and the convergent morphology shown by hybrids and their parental species (Cervera et al., 2005).To overcome the difficulties, molecular methods was brought in. Cervera et al. (2005) tried to determine the intergeneric, intersectional, interspecific, and intraspecific genetic and phyloge-netic relationships among species and hybrids of the Populus genus molecularly  by using AFLP markers, and concluded Populus species generally  group along their classical section lines, with markable exceptions observed, such as the placement of P. nigra in the Aigeiros section (Fig. 3-1-4). Meanwhile Hamzeh and Dayanandan (2004) approached the phylogeny by nucleotide se-quences of certain chloroplast  and nuclear genes (chloroplast trnT-trnF region and rDNA), and ? 12proposed a phylogeny trees of the genus which fits into the molecular interpretations towards the interspecific phylogenetic relationship  of the genus from three different angle (Fig. 3-1-3). Com-bining the molecular analysis with the traditional evolutionary analysis, the researches conducted by Cervera, as well as Hamzeh and Dayanandan proved the suggestion of Eckenwalder: since the progenitor species are generally of higher genetical diversity  than the derived species do, Popu-lus species under the Leuce and Aigeiros section are reckoned to be the oldest  and the most re-cent poplar species, respectively (Eckenwalder, 1996).With the refined information evolutionary  back ground and phylogenetic relationship provided, the breeding within the species and the genetic modification targeting species within the genus are under going a way with more directions. It would provide information for both traditional and modern poplar breeding. One example of phylogenetic background knowledge helps throw-ing light upon poplar breeding is the developing and utilisation of Poplar 741. For many  poplar transgenic experiments conducted in China, hybrid-clone 741, which is a complex cross of sev-eral poplars [Populus alba L. ? (P. davidiana Dode + P. simonii Carr.) ? P. tomentosa Carr.], is used to diminish gene flow of transgenes into the environment and natural population, since the formation of seeds in 741 Poplar is restricted and these seeds possess no capability  to germinate under natural condition (Ewald et al., 2006). Finding this base material, increased the efficiency and reduced the cost of the experiments on transgenic poplars. 3 . 2  W H Y  D O  C H I N E S E  F O R E S T E R S  C R E A T E  A N D  R E-L E A S E  G M  P O P L A R S ?With such improved technology  to facilitate breeding, and the public concerns on genetic engi-neering both scientifically and ethically, why are GM poplars still created and why is it even de-veloped with considerably or even concernably high pace? Improvement of trees through conventional breeding is constrained by the long reproductive cy-cles and complex reproductive characteristics of woody  plants, even with the help  with in vito technologies, it takes a relatively  long period to stable or maintainable cultivars with favoured ? 13characteristics (Fladung, 2006), especially with the interspecific incompatibility  system in some poplar species. Thus, when genetic engineering offers an attractive addition to conventional breeding by permitting the transfer of genes coding for preferred traits into selected cultivars without compromising their desirable genetic background, while taking the waiting through sev-eral life cycles out of the breeders way (Frankenhuyzen & Beardmore, 2004), the industry jumped for it.Genetic engineering is expected to bring great traits into poplar cultivars, which will majorly benefit the intensively managed short-rotation plantations with clonally propagated species, in contrast to conventional breeding, which is limited to sexually accessible variation with complex, sometimes combined traits that typically  depend on a large number of interacting genes, recombinant-DNA technology presented an almost infinite gene pool for breeders? to find and use genes coding for favourable traits. Concluded by Frankenhuyzen and Beardmore, endoge-nous genes already present in the tree genome can be modified to improve certain traits, such as fibre content and wood quantity, while exogenous genes can be transferred from unrelated organ-isms to provide entirely novel traits, such as resistance to herbicides, diseases or pests. The tar-geting traits are expected to positively affect the economics of plantation forests (improved growth, reduced rotation, promoted wood yield and quality, lowered cost of pest control), or con-fer various environmental benefits associated with forestry production (reduced pesticide and herbicide use) or processing (improved pulping, reduced inputs of hazardous chemicals and en-ergy). (Frankenhuyzen & Beardmore, 2004)By reducing the harvesting pressures on natural forest and meeting the industrial demands, GM tree breeding is now seen as an important future forest conservation strategies by its supporters (Adams et al. 2002). 3 . 2 . 1  M O D I F I C A T I O N  O F  W O O D  P R O D U C T I O NThe same as in most areas in the world, there is an urgent demand in wood and wood products to be met in China. The country  is now, the largest importer of industrial logs and the second largest ? 14importer of forest products globally, reported by FAO (Lu, 2004). At the same time, the protec-tion of natural forests, which had become necessary  because of the severe deforestation caused by industrialisation and environmental degradation, contributed to a shortage in wood production (Ewald et al., 2006).To achieve maximised economic benefits, there are two basic directions in modifying wood pro-duction: quantitively and qualitatively. The first one is usually achieved by altering the plant me-tabolism and increase the growth rate thus to obtain increased biomass production. The latter could be achieved by modifying the lignin / cellulose synthesis mechanism (Fladung, 2006). While modification of wood parameters and growth are traditionally  a major goal in forest breed-ing programs, the material is as complex as the formation process, thus targets are extremely hard to be accomplish through the time and resources consuming methods of conventional breed-ing; even when cultivars are established, their performance is largely dependent on ambient con-ditions (Fladung, 2006).Genetically modified trees with reduced lignin composition have been proposed as a strategy to potentially reduce environmental impacts from chemically harsh pulping practices, maximise operation efficiency and minimise the environmental footprint  in the paper industry  (Sponza, 2003).3 . 2 . 2  A B I O T I C  S T R E S S  T O L E R A N TAlong with the megatrend of global climate change, desertification, salinization and accumula-tion of toxic substances in soils (Frankenhuyzen & Beardmore, 2004), one of the serious prob-lems confronting Chinese forestry is soil salinity  (Ewald et al, 2006), as well as dry  out and pol-lution of the limited water supply, which makes the already limited land resources for forest habitat conservation and industrial plantation even more stretched. Poplars as tested phytoreme-diating and water-soil conserving species (Marmiroli, 2011), are propagated as a fixation of the situation, which will make the primary salinized land productive, put the secondary  salinized land on the way of recovering and becoming arable and detoxify  the polluted    soil to a certain ? 15degree. However, the mechanism is very complexed and only  by transcriptomes comparison and pathway analysis can scientists understand the establishment of such stress tolerance mecha-nisms through evolutionary  adaption (Janz et al., 2010). Thus, genetic engineering becomes the most efficient way to combine preferred traits and realise them in single cultivars, so as to keep the land productivity within salinised areas, or with the plantation still functioning in phytoreme-diation, which is considered an approach towards ease the dilemma of mitigating the shortage of land resource contradicting the unfulfilled huge forest biomass demands in China.Another main abiotic stress affecting poplar plantations in China is frost. To over come this is-sue, alternations in poplar phenology were often conducted. Usually, breeders try to put back the budding time to avoid cold damage to the newly germinated parts.  With conventional breeding, the goal of achieving cold hardness as well as high productivity is constrained by limited germ-plasm resources within the genus and interspecific incompatibility. To remove frost as a growth limiting factor for plantations and to adapt to the capricious weather under the influence of global climate change, as well as to meet the urgent need of forestry product by the booming population, gene transfer became the most economic solution.3 . 2 . 3  B I O T I C  D I S T U R B A N C E  R E S I S T A N C EInsect attacks and diseases are the main factors for economic losses in forestry. According to in-complete statistics dating back to the 1950s, the 1960s and the 1990s, an annual increase of losses of 25% was calculated in Chinese forestal economy (Su et al. 2003). Insect resistance is among the major goal, if not the most important one, of Chinese modern for-estry, since pest infection is one of the main causes of forest damage, especially in artificial plan-tations and the insects are often a limiting factor for tree growth and biomass production (Ewald et al., 2006). The control of forest pests with insecticides is only capable on smaller scales, such as in nurseries, but has detrimental ecological effects (Ewald et al., 2006). The Three North Shel-terbelts Project, which, as mentioned previously, is established with intensely  duplicated clones of very limited cultivars, has already been threatened by insect attacks. The reduction in timber ? 16production of Chinese forestry due to pests has been estimated to be around 17 million cubic me-tres per year that results in a huge economic loss. A spread of these insects from plantations into natural forests, causing a loss in both forest coverage and biodiversity in the surrounding ecosys-tem is of great possibility (Su et al. 2003).Meanwhile, the resistance and resilience against diseases caused by virus, fungus and bacteria are attracting increasing attention in China. The diseases do not only cause forest mortality, dam-aged wood quality  and reduced aesthetic value, but often spread around fleetly and tend to be associated with insects, which made it extremely hard to be taken under control once happened, usually  requiring intense chemical treatment that potentially do harm to micro-organisms, the rhizosphere, the local environment and affects broader area through the water-soil system.Therefore, efficient solutions for overcoming the problems in an economic way is under urgent call and biotechnology offers a real and fast solution (Ewald et  al., 2006), both the breeders and the stakeholders jump at having the insect resistant genes engineered into poplar and have the cultivars commercialised to take the severe loss under control, and maybe make some benefit within the shortest time. This would not only ease the economic issue, but will also approach to-wards solving the biomass resource security  issue of the nation, since it is not a secure way for long term operation to rely that much on imported wood. 3 . 3  I M P A C T S  A N D  C O N C E R N S  I N  B O T H  L O N G -  A N D  S H O R T - T E R M S3 . 3 . 1  G E N E T I C  C O N T A M I N A T I O NSince poplars have a relatively long life span, and the metabolism and reproduction process of GM  poplar will leave tissues and secretions containing novel genes in the local ecosystem to be accumulated through their life cycle. Suggested by Li (unpublished), the transferred genes left in the rhizospheric soil system is testable and stable for approximately three years, while the me-tabolism of the trees is always happening. Also, routes of novel gene transfer and exotic protein ? 17obtain could be established in the forest soil system, which links litter decomposition and nutri-ent cycling dynamically, and where novel proteins could be transmitted through the network con-structed by soil, soil microflora, mycorhizal and plant root (Frankenhuyzen & Beardmore, 2004). Thus, with the continually inflow of engineered DNAs and novel proteins into the soil, concerns on the direct and indirect  effects of novel gene leftovers are rising from the very  beginning of tree genetic engineering, which are mainly addressed on impacts of toxin-encoding transgenes on population levels of competitors, preys, hosts, sybionts, predators, parasites, pathogens and soil microbes, as well as the influence of novel genes and toxic proteins on non-target organisms (Lu, 2008). Apart from this, the invasive escape and vertical gene flow from GM clones towards their non-GM  counter-species, varieties, cultivars, landraces, as well as wild relatives has intimidated tre-mendous debate worldwide (Snow, 2002). Transgenic species and their offsprings are concerned to turn into weeds, since the super competitive characters brought in by the transgenes greatly increased the invasiveness of its carrier, for instance by  conferring early stage herbicides resis-tance into certain cultivar (Frankenhuyzen & Beardmore, 2004). Then, they might take over the habitat of the wild species or traditional varieties resulting in biodiversity losses and increased conservational cost. The concern is not a presumption but a lesson learn form the history of ex-otic tree species cultivation and plantation, for example, more than 19 species of pines have es-caped cultivation and become invasive weeds in the southern hemisphere during the last decades costing huge losses in economic and ecological values (Richardson, 1998; Frankenhuyzen & Beardmore, 2004). Moreover, the novel genes could flow to nontransgenic individuals within the same species through sexual reproduction, such as pollination, which is already observed by Stewart et al. (2003) and many other scientists in GM  annual crop plants, and as stated by Smouse et al. (2007), transgene flow by  propagules was seen in GM forest trees. In addition, transgenes could be passed on to the wild relatives without  interspicific incompatibility through out-breeding and gene introgression (Snow, 2002; Stewart et al., 2003).? 18Concerns have also been addressed on horizontal novel gene transferring from GM plants to un-related organisms, sometimes even a cross-kingdom gene transfer, through nonsexual means, like feed and digestion or biosynthesis. The most common example is from plants to parasite or micro-organisms (Lu, 2008; Frankenhuyzen & Beardmore, 2004). A recent research conducted by Zhang et al. (2012) found out that  exogenous plant miRNAs were present in the sera and tis-sues of various animals, which were primarily  acquired orally through food intake; they stated that their findings demonstrated that exogenous plant genetic material in food can regulate ex-pression of target genes in mammals. Suddenly, the discussion of biosafty risks brought by commercialising GM crops and trees reached a new peak in vehemence. 3 . 3 . 2  E C O L O G I C A L  P R E S S U R EEven if transgenes are well restricted within the carriers, they might still have it?s influence on the holding environment (Frankenhuyzen & Beardmore, 2004). The large existence of transgenic trees with engineered traits and a long life span draws significant ecological pressure on its living habitat, which includes the selection pressure on both targeting and non-targeting organisms in the local habitat and the ecosystem and the possible niche shift caused by  their over-competing surrounding plant  species and the influence on their associated species. All of these implicate a predictable loss in biodiversity, especially genetic diversity both within the species and among the ecosystem. Thus, they might as well affect critical ecosystem processes like decomposition and nutrient cycling (Frankenhuyzen & Beardmore, 2004). Insects and pathogens have extremely short life cycles comparing with trees, thus within a pest or disease resistant GM poplar site, the evolution of resistant pest or pathogen biotypes stand a great chance of exceeding both the sustainability of the habitat and the function of the engineered traits (Strauss et al., 1991; Brunner et  al., 2007). Selection pressures resulting from GM trees with superb characteristics could also affect non targeting insect species within the same habitat, which might be achieve by altering the food chain or breaking the equilibrium in competition (Frankenhuyzen & Beardmore, 2004). Thus, possible consequences on pest competitive  sup-pression and trophic interactions (Schuler et al. 2001) that might shift arboreal organism com-? 19munity dynamic and local biodiversity should be precautiously examined before the release of anti-insect transgenics.  There are still some unknown mechanism, involvements and routes in biogeochemical process. Significant interactions between engineered traits and the environment might  come within our sight anytime. Further studies and observations are necessary  before stepping forward (Lu, 2008).3 . 3 . 3  F O O D  A N D  F E E D  S A F E T YDirectly affecting ourselves are the food and feed safety issues caused by  GM plants. The main concerns are about toxicity, allergy  and long tern effect  on human and other living creatures? health caused by products from or under the impacts of GM plants. Plenty  of genes used in genetic modification are of the ability to cause toxicity, for example anti-biotic marker gene, anti-insect genes that encoding for insecticidal protein or neurotoxins and genes coding for antibacterial chemicals all have a potential toxicity  towards livestocks that de-pends on poplar leaves and young tissues, and then humans (Liu et al., 2001; Anon, 2008; S?-ralini et al., 2011). Allergy is usually  caused by pollens from GM plants. It may affect not  only humans and animals within the forest stand, but also have the influence delivered with the dis-tance travel pollens and seeds, and the anaphylaxis could be caused by direct contact with plant tissue or pollen, feeding on GM contaminated food and applying personal care products derived from GM  plants or plant materials contaminated by GMOs (Madsen & Sand?e, 2008; Antignac et al., 2010; Domingo & Bordonaba, 2011). Although, the concerns about subchronic and chronic health effects has been raised for GMOs, especially those containing pesticides, either produced from their engineered insect tolerance mechanism or gained from the external applica-tion of chemicals based on their pesticide tolerance, and some statistically  significant findings on the toxicity of GMOs on rodent have been revealed (S?ralini et  al., 2009; 2012), most relevant studies indicate no obvious deleterious effect. However, the no-obvious-effect  situation is be-lieved to be a consequence of insufficient studies limited by  time and methods (S?ralini et al., 2012). ? 203 . 4  S T A T U S  Q U O  O F  G M  P O P L A R S  I N  C H I N ALeple et al. reviewed all genetically engineered Populus species and hybrids by the year of 2000 worldwide (Table 3-3). Eight herbicides resistant lines, 5 insect resistant lines and 10 growth al-ternated lines, as well as 6 lines developed for wood quality modification. There are two cultivars of transgenic poplars commercialised in China by 2003: one is Poplar Hybrid 741 with Bt, Cry1 and API genes inserted, the other is Populus nigra with single Bt inserted, and they are both en-gineered to resistant leaf-eating insects (Sigaud, FAO). By 2010, nineteen insect-resistant GM poplar lines was created in China (Hu et al., 2010) possessing genes or combination of genes en-coding the production of proteinase inhibitors, insecticidal proteins, lectin or neurotoxin, all effi-cient in fighting against insects (Ewald et al., 2006).While the research and application of genetic modification are developing rapidly, the relative policies in China remained brief and deficient. Table 4 reviewed major policy measures related to biotechnology  carried out in China from early  1980s (Huang & Wang, 2002), from which we see the refining process of the national policies, however, it  is still way too loose comparing with that of the EU (Jaffe, 2004). Also, based on my observation, the public awareness and participation are relatively low. There is barely  no local NGO or community advocacy for ge-netic safety issues. This unbalanced situation might enlarge the nation?s chance in confronting with genetic contamination and related negative ecological changes. 4. A proposal of ?What we can do before it?s too late?4 . 1  T R A N S P A R E N C Y  First of all, I advocate for transparency in policy  making procedures, which should not only  be known within the high-level authority, as well as the data and information facilitating the deci-sion making, which should not be kept within the authority group. The consumers have the right to informations that may benefit  their choice and the farmers and foresters have the right to the ? 21genetic resources on their land. It is not fair for the policy makers to keep  them from knowing what they should know. Also, I advocate for marketing transparency. Labelling products containing GM  materials and products harvested or processed in and near GM poplar forests and nurseries, for example eco-nomic agriculture products harvested from undergrowth layer of forest stands constructed with GM  poplars. What?s more important, the labels should be obvious and easy  to find. Based on my observation, GMO products in the market in China are either labeled ambiguous or the label is extremely small and hard to find. People who is not conscious about  GMO related issues, or sen-iors and kids without sensitive observational ability  may never notice the information, which is supposed to be carried out to each consumer. Every purchase and consume on GMO related products should be conducted by people who is fully aware of it, or it is no difference than mar-ket fraud. The government should standardise the labelling in the market with uniform marks. Not only should GM poplar products be labelled, GM poplar surrounding products should also be labelled. If a carton of mushroom is non-GMO itself but is harvested from GM  poplar logs, the information should be clearly conducted to the customers. With such board scale of GM plants released and commercialised in China, no blind buying and trading of GM  related prod-ucts is still tolerable. If the people cannot choose whether they  want GMOs to be released and commercialised in their country, they  should at least be ensured their access to information about what  is going on ex-actly and their right of choosing whether to buy and used such product should be respected. 4 . 2  D E V E L O P  W E L L  E S T A B L I S H E D  R I S K  A S S E S S M E N T  A N D  R E G U L A T I O N  S Y S T E MWith all the concerns reviewed previously, insufficient risk assessing mechanism and the lack of efficient regulatory methods for the consequences of potential genetic contamination, the release and commercialisation of GM poplars were still carried out in China, which brought up the ur-? 22gent demand for a sensitive monitoring system as well as complementarity risk assessing and regulating mechanism.To assess the risk and find regulatory  methods, the foresters need to understand the condition first, and to really know what is going on with plantations containing GM  poplars and the nature forests near the plantations, GIS monitoring is a great tool for risk assessment, record keeping, forest management and geographical genetics conservation (Fan, 2001). However, it is very hard and costly to genotyping all the major poplar forest stand routinely and mark every genetic information on different layers in GIS to monitor the stability of target genes, the potential gene flow and both the long and short terms of ecological pressures. To lower the cost and increase the feasibility I suggest using asymmetry  data as an indicator. Asymmetry datas of plants is often fluctuating through its life history reflecting the living condition of the plant and could indicate their fitness, developmental stability  and the stress level (ecotoxicity, competi-tion, inbreeding, etc.) they are under (Clark et al., 1986; Jones, 1987; Graham et al., 1993; Ko-zlov et al., 1996; Rettig et al., 1997). Also, fluctuating asymmetry (FA) is more sensitive than life historical parameters, and is able to quantify  the impact of GM poplars, especially the ecological pressure (Zhai, 2001), which made it suitable for combination with GIS. As the mensuration and analysis of FA data are relatively easy to conduct and there is no need for high-priced instru-ments, the data collecting could be done with hearing co-op students, which on one hand, will lower the labour costs, on the other hand will provide students with a hand-on experience in for-est management and research, as well as better understanding in the forest ecosystem.Many other risk assessment mechanisms are proposed by  multiple authors. Most of them are laboratory operations, micro mimic nature system models (usually  for microbes) and mathemati-cal models that predict or determine the impacts and development trends of GM poplars (Do-mingo & Bordonaba, 2011). A combination of both field and laboratory  assessment gives forest-ers better information and chance to regulate potential consequences of GM popler releasing.? 234 . 3  D O  N O T  B E C O M E  T O O  R E L I E D  O N  G E N E T I C  E N-G I N E E R I N GEven though biotic disturbances resistant GM  poplars are currently  performing well in tolerating the attacks from insects and weedy, Chinese forestry should not rely entirely  on transgenes to solve the issues. In some small scaled plantation and plantation close to nature forests, bio-pesticide and bio-herbicide, which are not as toxic to the surrounding ecosystems as chemical compounds could be used in case of insect attack or weed overgrowth. Also, planting prescriptions could help with increasing the insect  resistance of traditional culti-vars and natural species of poplars. A common approach is mix planting. Pointed out by  Ewald et al. (2006) Asian longhorn beetle (Anoplophora glabripennis) is the major damage causing pest for poplars in China. However, mix-plant non-GM  poplars with Ailanthus altissima helps the stand resist against Anoplophora spp. (Jin, 2008), which tend to be a good solution for stands not planted for maximum biomass production. Meanwhile, both commercial and researching organic farming and foresting should be encour-aged, as a preservation of genetic resources, a life style choice for people and a research poten-tial.4 . 4  A P P R O A C H I N G  T H E  P R O B L E M S  T H R O U G H  ? T R A-D I T I O N A L  B R E E D I N G ?  O F  P O P L A R SSince Chinese forestry is confronted with several dilemmas mentioned in section 3.2, to become less relied on genetic engineering, Chinese foresters should try to breed certain non-transgenic poplar cultivars that is capable of solving part of the problems. The first step  of a breeding plan is to select for the suitable germplasm. In the breeding plan I am going to propose, the key species is Populus euphratica. It is a broadly distributed tree species in central Asia, of whom the natural habitats in China are located in the deserted area in Gansu, Qinghai, Xinjiang, Ningxia and Inner Mongolia (Peng et al., 2009; Zhang, 2009). P. euphratica ? 24evolved from the harsh deserted habitat process great quality of salinity tolerance, waterlog tol-erance, drought tolerance and sandstorm resistance. Also, it is no leaf feeding lepisoptera species hosting on Populus euphratica distributed in China (Table 5, Robinson et al., 2010).  Populus euphratica is the only species under the section Turanga, so the hybrid between it and any other Populus species will be characterised under distant hybridisation, which is highly  af-fected by its interspecific incompatibility. To overcome the barrier, breeders employed artificial pollination on stigmas previously treated with female parental pollen extracts, in vitro ovule cul-ture, and hybrid seedlings in vitro propagation technics to force hybridisation. Based on the re-sult achieved by  multiple combinations tries through different breeding methods, when using P. euphratica as the pollen source, the hybrid progenies tend to possess more desired traits in P. eu-phratica (Peng et al., 2009). Also, the survival rate of seed germinated seedlings are much higher than that  of the clones developed from sprout tillers, thus some asexual propagation might not be suitable for establishing hybrid P. euphratica stands (Shen et al., 2009). With the germplasm se-lected, the breeding methods developed and relative mechanism studied, the preferable cultivars will not remain hard to create for very long. 4 . 5  A  P R O S P E C TI my  perspective, a desirable future condition of GM poplar forestry in China is constructed with three elements: well established risk assessing and regulating mechanism, elaborative record keeping and monitoring system and carefully restricted plantation area gradually replaced by mix-planting or traditional hybrids with no less biomass production making the utmost of the na-ture biodiversity. From scopes other than forestry, I am looking forward to see the government could hold on to its own word of valuing the principle of freedom of science, but advances in science must serve, not harm humankind, and will actually ?mull over new rules and regulations to guide, promote, regulate, and guarantee a healthy development of science?, promoting the technology while showing appropriate precaution for biosafety, environmental health, food safety, and the commercialisation of biotechnology (Huang & Wang, 2002).? 25ConclusionGenetic modification is a double-edged sword, from which we knew exactly what we would be benefiting, but what damage would it do were never thoroughly understood. The extensive culti-vation of GM poplars in China has generated great benefits and helped solving a variety of issues both ecologically and economically. However, even while we are in the biotech era, the current information and data are not sufficient in showing the exact long-term influence of GM poplars on both bio-safety and human health. Great issues have been raised concerning GMO deploy-ment at large. The fact that GM trees are already widely planted in China and the present risk assessment system is not adequate in addressing these concerns, then the establishing of a so-phisticated risk assessment system is urgently needed. The plethora of available knowledge did not only provide us a way to deal with the present, but also should assist us to use biotechnology in a sustainable manner to save the future for all the living creatures.  While benefiting from ge-netic engineering, an integrated standing system of research, monitoring, evaluating and readjust-ing should be established.? 26 Construction Area of the Three North Shelterbelt Project Started from: 1978Planned time span: 73 years.Total area within the plan: 406.9 mil ha.Divisions: 4480 km east-west                 560-1460 km north-southAchievements in Stage One (1978 - 2000)Meadow pasture protection forest established: 0.5 mil ha.Meadow protected: 1.5 mil ha.Meadow recovered from desertification and salinization: 30.03 mil ha.Appendix IFigure 1-1. Construction area of the Three North Shelterbelt Project. (Edited from the original illustration by Ding, M. & Zhang, Y. Publish by Xinhua News Agency)? 27s: \ sigaud \ countries \ china \ Poplar Genetic Resources in North China02.doc 3     North East Central  North North West  SPECIES Heil Jil  Liao Mon Heb Shan Shaa Gan Nin Qing Xinj ALTITUDE (m) P. afghanica           ? 1400 - 2800 P. alba           ? 450 - 750 P. amuyensis ?   ?        600 - 800 P. canescens           ? 600 - 700 P. cathayana   ? ? ? ? ? ?  ? ? 800 - 3200 P. charbinensis ?           300 - 500 P. davidiana ? ? ? ? ? ? ? ? ? ? ? 200 - 3800 P. euphratica    ?    ? ? ? ? 2500 - 2900 P. gansuensis        ?    1800 - 2000 P. girinensis ? ?          300 - 400 P. hopeiensis     ? ? ? ? ? ?  700 - 1600 P. hsinganica ?   ? ?       300 - 700 P. iliensis           ? 600 - 750 P. jrtyschensis           ? 200 - 2000 P. koreana ? ? ?         400 - 1100 P. lasiocarpa       ?     1300 - 3500 P. laurifolia           ? 1200 -1700 P. maximowiczii ? ? ? ? ?  ? ?    400 - 2000 P. nakaii ? ? ? ? ?       600 - 900 P. nigra           ? 400 - 800 P. ningshanica      ? ?     600 - 1000 P. pamirica           ? 1800 - 2000 P. pilosa           ? 1600 - 2300 P. pruinosa           ? 300 - 1500 P. przewalskii    ?   ?  ?   500 - 1500 P.pseudomaximowiczii     ?  ?     1000 - 1600 P. pseudosimonii ? ? ? ? ? ? ? ?  ?  300 - 2300 P. pseudotomentosa      ?      300 - 1400 P. purdomii     ?  ? ?    700 - 3300 P. simonii ? ? ? ? ? ? ? ? ? ? ? 600 - 2300 P. suaveollens ?   ?        200 - 400 P. szechuanica       ? ?    1100 - 4000 P. talassica           ? 500 - 1800 P. tomentosa     ? ? ? ?    200 - 1800 P. tremula           ? 700 - 2300 P. ussuriensis ? ? ?         300 - 1400 P. wilsonii       ? ?    1300 - 3300  NUMBER BY PROVINCE 12 8 8 11 11 8 14 12 5 6 16 37 Legend: Heil: Heilongjiang; Jil: Jilin; Liao: Liaoning; Mon: Inner Mongolia; Heb: Hebei; Shan: Shanxi; Shaa: Shaanxi; Gan: Gansu; Nin: Ningxia; Q ing: Q inghai; Xin: Xinjiang  Table 1:  Distribution of poplar species in North China (Based on Xu, 1988)   Table 1. Distribution of poplar species in North China. (Derived by Sigaud, FAO., based on Xu, 1988) *Heil - Heilongjiang Province; Jil - Jilin Province; Liao - Liaoning;    Mon - Inner Mongolia Municipality; Heb - Hebei Province; Shan - Shanxi Province;    Shaa - Shaanxi Province; Gan - Gansu Provinc ; Nin - Ningxia Municipality;    Qing: Qinghai Province; Xin - Xinjiang Municipality? 28Figure 1-2. Classification and distribution of indigenous poplar species of China according the climatic zones (Weisgerber & Zhou, 1997.  Translated from German to English and edited by the author)? 29!"#$%&'et al(' )*Figure S3('+,-.,#,&/%/01&'12' /3,'))4'56'12'Populus'7,&1809'#,:",&9,'91&/%0&,;' 0&'*44'#9%221<;#'%<07&,;'%&;'1.0,&/,;'/1'%'7,&,/09'8%-'12'/3,'*='Populus'<0&$%7,'7.1"-#'>0&;09%/,;'6?' +18%&' &"8,.%<#' I@XIXA(' B%93' #9%221<;' >yellow' 6%.#A' C%#' 8%--,;' /1' %' 93.181#18,'>blue' 6%.#A' "#0&7' 809.1#%/,<<0/,' 8%.$,.#' C0/3' "&0:",' #,:",&9,' <19%/01&#' >red' <0&,#A('D"86,.#' 0&' -%.,&/3,#,#' %.,' ,#/08%/,#' 12' /3,' -,.9,&/' 12' /3,' <0&$%7,' 7.1"-' 91E,.,;' 6?'%##,86<,;' #,:",&9,' >%##"80&7' "&021.8' -3?#09%<F' 7,&,/09' ;0#/%&9,' %9.1##' /3,' 7,&18,A('G--.1H08%/,'#0I,' >0&'$6A' 0#' 0&;09%/,;' /1' /3,' .073/'12',%93'#9%221<;('J%-#'6,/C,,&'#9%221<;#'%.,' 12' "&$&1C&' #0I,(' !30#' %##,86<?' 0&9<";,#' 08-.1E,8,&/#' #0&9,' /3,' E,.#01&' /3%/' C%#'-"6<09<?'.,<,%#,;'%&;'"#,;'21.'81#/'7,&18,'%&%<?#,#('Appendix IIFigure 2-1.  Representation of the 335 Mb of Populus genomic sequence contained in 155 Scaf-folds aligned and oriented to a genetic map of the 19 Populus linkage groups (indicated by Ro-man numerals I - XIX) (Tuskan et al., 2006)* Each scaffold (yellow bars) was mapped to a chromosome (blue bars) using micro-satellite markers with unique sequence locations (red lines). Numbers in parentheses are estimates of the percentage of the linkage group covered by assembled sequence (assuming uniform physical: genetic distance across the genome). Approximate size (in kb) is indicated to the right of each Scaffold. Gaps between scaffolds are known size.? 30!"#$%&'et al(' )*2 Figure S4.'+,-.' #/%0&12'a)' 34536%#1'%&2'b)'71/%36%#1'Populus' #57%/08' 864575#571#'%&2'9.:;'"#0&<',4%=0253#0#>/?31'/1@57141'4131%/'#1A"1&81'B,>/?31'!C:DE'FG:>*G:'4+H,E'I:'4+H,E'%&2'@0&$%<1'<45"3'BJKD'#3180L08'Populus'M,N'8@5&1#'%#'345=1#(' '%&2'red'%445O#'a)'#65O'61/14586457%/08' B,>!' 4086E' =40<6/@?' #/%0&12D' %&2' 1"86457%/08' 41<05&#E' 41#318/0P1@?(' 954' 2%/%'85@@18/05&E'864575#571#'O141'&"7=1412'%4=0/4%40@?' L457'F' /5')G' 0&'1%86'81@@'%&2'864575#571'@1&</6'O%#'71%#"412'/6411'/071#'314'864575#571'B#65O&'=?'O60/1'/4%81'@0&1#D'"#0&<'Q3/07%#'PR('c)',>/?31'!C:'9.:;'#0<&%@#'%41'5=#14P12'%/' /61'1&2'%@@'864575#571'%47#E'd)'M,N#'L457'JKS.T'%41' L5"&2' /5'=1'85>@58%@0U12'O0/6'%&'FG:>*G:'4+H,'#0/1'%&2'e)'M,N#'L457'JKST..'%41'L5"&2'/5'=1'85>@58%@0U12'O0/6'/61'I:'4+H,'#0/1( M%4'0#'FV'W7(Figure 2-2. DAPI stained a) prophase and b0 metaphase Populus somatic chromosomes and FISH using Arabidopsis-tyoe telomere repeat sequence (A-type TRS), 18S-28S rDNA, 5S rDNA and linkage group (LG) specific Poplulus BAC clones as probes. (Tuskan et al., 2006)* White and red arrows  a) show heterochromatic (A-T rich, brightly stained) and euchromatic regions, respectively. For data collection, chromosomes were numbered arbitrarily from 1 to 38 in each cell and chromosome length was measured three times per chromosome (shown by white trace lines) using Op-timas v6. c) A-type TRS FISH signals are observed at the end all chromosome arms. d) BACs from ? 31!"#$%&'et al(' ))Figure S5.' *+%,-./' +0,+0#0&1%1.2&' 23' 1-0' de novo' 4-250670&280' #-217"&' #09"0&/0'%##08:5;' %&<' %&&21%1.2&' 32+' 1-0' Populus trichocarpa' /-52+2,5%#1(' =%/-' &"/5021.<0' .#'+0,+0#0&10<' :;' %&' %>0+%70' 23' ?@A' #09"0&/0' +0%<#' %1' %' 9"%5.1;' #/2+0' 23' ?A' 2+' -.7-0+('*0&0' 82<05#' 40+0' ,+0<./10<' :%#0<' 2&' 1-0' *5.880+' ,+27+%8' %1' B%$' C.<70' D1.%2&%5'E%:2+%12+;('LGXIV are found to be co-localized with an 18S-28S rDNA site and e) BACs from LGXVII are found to be co-localised with the 5S rDNA site. Bar is 10 ?m.Figure 2-3. Graphic representation of the de novo whole-genome shotgun sequence assembly and annotation for the Poplulus trichocar a chloroplast. (Tuskan et al., 2006)? 32!"#$%&'et al(' )*2 Figure S13.' +,-./.#./%0' 0.1%023%42.&' 56#27&%465' 89' 02&$%76' 7-.":#' ;<=>?' @.-'52#6%#6' -6#2#4%&16' 76&6#' ;4.:>?' 76&6#' 1.52&7' @.-' A)BC' 6&39/6#' ;/25506>' %&5'4-%&#1-2:42.&'@%14.-#';8.44./>('Yellow'56&.46#'%'#2&706'76&6'2&'%'*CC'$8'D2&5.D?'red'E'.-'/.-6'76&6#'2&'%'*CC'8:'D2&5.D(''* Each nucleotide is represented by an average of 410 sequence reads at a quality score of 40 or higher. Gene Models were predicted based on the Glimmer program at Oak Ridge National Laboratory. Figure 2-4. Chromosomal localization designated by linkage groups (LG), for disease resistance genes (top), genes coding for P450 enzymes (middle) and transcription factors (bottom). (Tuskan et al., 2006)* Yellow denotes a single gene in a 100 kb window, red 2 or more genes in a 100 bp window. ? 331998; Constabel and Ryan 1998) is an advantageover small plant models such as Arabidopsis in stud-ies involving systemic signal movement. Induced re-sistance to insect herbivory is acquired systemicallyand is phenocopied in part by mechanical injury(Havill and Raffa 1999). This positions poplar as anexcellent model for synthesizing ecologic and mo-lecular perspectives of induced resistance to insectherbivory.Dramatic Patterns of Nitrogen Allocation,Use, and StorageRiparian ecosystems receive nutrient inputs episodi-cally, which may help explain why poplar tissuesstore high levels of nitrogen in the form of vegeta-tive storage proteins for subsequent use (Colemanand others 1994; Lawrence and others 1997). Wehave observed healthy poplar leaves with nitrogenconcentrations exceeding 8% of dry weight (J.Cooke, K. Brown, J. Davis, unpublished), comparedwith the 1?1.5% maximum levels found even infertilized conifer needles. Nitrogen levels fluctuatedynamically among organs within the same tree(roots, stem, and leaves) in concordance with sea-sonal rhythms of active growth and dormancy. Thestem anatomy of poplar trees is particularly suited tostudying the role of phloem-transmissible sub-stances such as glutamine in regulating nitrogen al-location, because phloem can be specifically per-turbed by girdling, whereas xylem transport remainsintact (for example, Sauter and Neumann 1994).Physiological Process Models for PoplarGrowth and DevelopmentLarge databases of anatomical, physiological, and sil-vicultural traits are available for a modest number ofPopulus hybrids and clones. Several physiologicallybased growth and productivity models have beendeveloped from these data. The models include basicinformation on carbon uptake and allocation in pop-lar, as well as components and parameters of leafdisplay and crown structure. Most of the modelssimulate carbon uptake, carbon allocation, growth,and/or light interception in poplar and incorporatesome specific parameters of leaf display, position inthe tree, and branch structure (Chen and others1994; Host and others 1996; Isebrands and others1996). Data on the physiological and structuralgrowth determinants at the leaf, branch, and wholetree level indicate that differences in clonal produc-tivity can be incorporated into the ideotype conceptdeveloped for poplar tree breeding under short ro-tation intensive culture (Dickmann 1985; Dickmannand Keathley 1996).Cloning of Individual Tree GenotypesThe ease with which most materials can be vegeta-tively propagated is one of poplar?s premier assets.Cloning captures genetic variation and allows it tobe replicated in space and time in separate experi-ments. Cloning ?freezes? genetic variation in hybridsand permits the side-by-side growth of multiple gen-erations of a pedigree. Cloning permits the growth ofabnormal plants under field conditions that in thecompetitive environment of a seedling populationwould be impossible. Cloning also allows destructivesampling for physiological studies, the sharing ofmaterials among laboratories, and the buildup of cu-mulative knowledge on selected genotypes.Closely Related to Other AngiospermModel PlantsUnlike the pines and other gymnosperms, poplarsdiverged relatively recently from other angiosperms,such as Arabidopsis, which serve as models for inte-grating genetics into the study of plant biology (Fig-ure 1).Small Genome SizeThe haploid genome size of Populus is 550 millionbase pairs (bp) (Bradshaw and Stettler 1993), only 4times larger than the genome of the model plantArabidopsis, and 40 times smaller than the genomesof conifers such as loblolly pine. The small poplarFigure 1. Phylogeny of Populus.Poplar as a Model Forest Tree 309? New Phytologist (2005) www.newphytologist.org New Phytologist (2005) 167: 165?170Research 169these dates differ considerably and should be interpretedwith caution, it is clear that all the poplar species examinedshare the polyploidy event. This can be explained only ifthe genome duplication occurred in the ancestor of all thesespecies, somewhere between 8 and 13 myr ago. This also meansthat the divergence of the different poplar sections mustbe more recent than the polyploidy event. The earliest fossilsclaimed as being of poplar are 58-myr-old leaves ascribed tothe section Abaso, which is probably one of the earliest diverg-ing poplar species (Fig. 2; Eckenwalder, 1996), but for whichunfortunately no EST data exist. Therefore we cannot con-clude for sure whether the Abaso section shares the duplica-tion event. In this respect it would also be interesting toexamine the duplication past of other members of the familySalicaceae, such as the sister genus of Populus, Salix, whichis closely related (Leskinen & Alstr?m-Rapaport, 1999;Wikstr?m et al., 2001), to see whether they share the sameduplication event. Unfortunately too few EST data are avail-able for the other Salicaceae, so this question remains unan-swered. The earliest fossil evidence ascribed to the otherpoplar sections is claimed to be between 18 and 40 myr old(Eckenwalder, 1996 and references therein), which predatesthe polyploidy event, and is thus clearly in disagreement withour data. There are two possible explanations for this incon-gruence. The first is that the poplar fossils are not correctlyascribed to the different poplar sections. Alternatively, itis possible that the rate of synonymous substitutions (?) forpoplar is somewhat different than the value generally used fordicots (see above). This is not unlikely considering the factthat the generation time of a species is known to affect itsnucleotide-substitution rate (Gaut, 1998) and that poplar hasa much longer generation time than most other plant speciesused in molecular research. Careful calibration of some poplarmolecular markers in the future may shed further light onthis.AcknowledgementsWe would like to thank Stefanie De Bodt, Steven Maere andKlaas Vandepoele for their help in producing and interpretingFig. 2 Schematic representation of the phylogeny of the genus Populus and some relevant plant species, based on Blanc & Wolfe (2004); Eckenwalder (1996); Wikstr?m et al. (2001). Grey dots indicate large-scale duplication events proposed by Blanc & Wolfe (2004; see also Van de Peer, 2004); a black dot denotes the large-scale duplication event in poplar proposed in the current study.Appendix IIIFigure 3-1-1. Phylogeny of Populus, which indicates poplars diverged relatively recently from other angiosperms, such as Arabidopsis. (Bradshaw et al., 2000; Brunner et al., 2004)Figure 3-1-2. Intersectional phylogenetic relationship of the genus Populus. Schematic represen-tation of the phylogeny of the genus Populus and some relevant plant species (Sterck et al., 2005).* Grey dots indicate large-scal  duplication events; the black dot denotes the large-scale duplication event in poplar p oposed in th  current study.? 34September 2004] 1401HAMZEH AND DAYANANDAN?POPLAR PHYLOGENYFig. 2. The majority rule consensus tree of 30 939 equally parsimonious trees (tree length 118; consistency index ! 0.924) based on three noncoding regionsof trnT-trnF of cpDNA sequences from Populus species. Numbers above branches show the frequency of occurrence in 50% majority rule consensus tree, andnumbers below branches indicate bootstrap percentage values. Numbers in brackets show branch lengths (number of nucleotide substitution). A, Aigeiros; P,Populus; T, Tacamahaca.phyletic and sections Tacamahaca and Aigeiros were poly-phyletic groups (Fig. 2).Maximum likelihood analysis?The results of the Modeltestanalysis showed that TrN " I (Tamura and Nei, 1993: equalrate for all transversions and different transition rates with un-equal base frequencies) nucleotide substitution model was themost suitable model for the cpDNA. The parameters of themodel were: base frequencies: A ! 0.4175, C ! 0.1336, G! 0.1467, T ! 0.3023; rate matrix: (A?C) ! (A?T) ! (C?G) ! (G?T) ! 1.0; (A?G) ! 1.7645; (C?T) ! 2.5848;among-site rate variation: proportion of invariable sites, I, !0.6953; equal rates of substitution for all variable sites.The maximum likelihood analysis of cpDNA with the de-scribed model parameters retained a single tree (Fig. 3) witha topology identical to the 50% majority rule consensus treeobtained from parsimony analysis. Moreover, the bootstrapvalues for branch robustness under the maximum likelihoodcriterion were similar to the values obtained from the sametest under the parsimony criterion.As with the MP analysis, the ML analysis also showed themonophyletic origin of section Populus and the polyphyleticFigure 3-1-3-a. Interspecific phylogen tic relati nship of the genus Populus. (Hamzeh & Day-anandan, 2004)The majority rule consensus tree of 30,939 equally parsimonious trees (tree length 118; consis-tency index = 0.924) based on three noncoding regions of trnT-trnF of cpDNA sequences from Populus species.* Numbers above branches show the frequency of occurrence in 50% majority rule consensus tree, and numbers below branches indicate bootstrap percentage values. * Numbers in brackets show branch lengths (number of nucleotide substitution). * A, Aig iros; P, Populus; T, Tacamahaca.? 35September 2004] 1403HAMZEH AND DAYANANDAN?POPLAR PHYLOGENYFig. 4. The majority rule consensus tree of 497 equally parsimonious trees (tree length 94; consistency index ! 0.851) based on partial 5.8S RNA gene,ITS1 and ITS2 and part of 28S subunit sequences from Populus species. Numbers above branches show frequency of occurrence in 50% majority rule consensustree, and numbers below branches indicate bootstrap percentage values. Numbers in brackets show branch lengths (number of nucleotide substitution). A,Aigeiros; P, Populus; T, Tacamahaca.the 497 retained equally parsimonious trees (Fig. 4). Moreover,a sister relationship of P. maximowiczii and P. laurifolia tothe clade comprising two lineages of the Aigeiros and groupof Tacamahaca species (as mentioned earlier) was weaklysupported. The basal position of P. simonii was not supportedby the bootstrap analysis.In the MP analysis of rDNA with respect to the results ofthe bootstrap analysis, all Populus species studied formed astrongly supported monophyletic group comprising two majorclades. One clade comprised all species of the section Populuswith P. tremuloides and P. grandidentata occupying a positionsister to the clade comprising Eurasian species of section Po-pulus (P. tremula, P. alba, and P. davidiana), suggesting amonophyletic origin for this section. The other major cladeincluded all of the remaining species studied.The relationships among species within section Tacama-haca were unresolved, and they grouped as a polytomy. How-ever, this section could be divided into two distinct groups oftaxa: P. maximowiczii, P. simonii, and P. laurifolia in onegroup and the other members of the section in another group.The relationships among species within section Aigeiros wereresolved, and the MP analysis of rDNA suggested a mono-phyletic origin for this section. However, this was not sup-ported by bootstrap analysis ("50%). A close relationshipamong P. nigra, P. deltoides var. angulata, and P. roegnerianawas evident. In contrast to the cpDNA-based MP tree, therDNA-based tree did not have a close affinity between P. nigraand members of section Populus. Populus tristis and P. sze-chuanica clustered as an unresolved polytomy with the re-maining species of sections Tacamahaca and Aigeiros.Figure 3-1-3-b. Interspecific phylogenetic relationship of the genus Populus. (Hamzeh & Day-anandan, 2004)The majority rule consensus tree of 497 equally parsimonious trees (tree length 94; consistency i dex = 0.851) based on partial 5.8S RNA gene, ITS1 and ITS2 and part of 28S subunit se-quences from Populus species. * Numbers above branches sho  frequency of occurrence i  50% majority rule c nsensus tree, and num-bers below branches indicate bootstrap percentage values. * Numbers in brackets show branch lengths (number of nucleotide substitution). * A, Aigeiros; P, Populus; T, Tacamahaca.? 361402 [Vol. 91AMERICAN JOURNAL OF BOTANYFig. 3. Maximum likelihood tree based on three noncoding regions of trnT-trnF of cpDNA sequences from Populus species. Numbers below branches showbootstrap percentage values. A, Aigeiros; P, Populus; T, Tacamahaca.origin of sections Tacamahaca and Aigeiros. Populus nigraclustered with members of the section Populus. Populus tristisand P. szechuanica grouped with the lineage comprising theNorth American cottonwoods of section Aigeiros.rDNA trees?Maximum parsimony analysis?The maxi-mum parsimony analysis based on nuclear rDNA yielded 497equally parsimonious trees (tree length ! 94; CI ! 0.851; RI! 0.888; RC ! 0.756). In the 50% majority rule consensustree (Fig. 4), two North American aspens, P. tremuloides andP. grandidentata, grouped as sister taxa in the lineage con-sisting of other Populus species, but their placement in thestrict consensus tree remained unresolved. In the 50% majorityrule consensus tree, a group of balsam poplars of section Ta-camahaca, namely P. angustifolia, P. cathayana, P. tricho-carpa, P. balsamifera, P. tristis, and P. szechuanica clusteredas a sister group to the lineage comprising members of sectionAigeiros. Although the branch representing Tacamahaca oc-curred in 75% and Aigeiros 100% of 497 most parsimonioustrees, these branches were not supported by bootstrap analysis.Moreover, in the 50% majority rule consensus tree, within thebalsam poplar lineage, P. trichocarpa, P. balsamifera, P. tris-tis, and P. szechuanica clustered together as a sister group toP. angustifolia and P. cathayana. However, none of these in-ternal nodes and relationships was supported by the bootstrapanalysis, even though they occurred with a high percentage inFigure 3-1-3-c. Interspecific phylogenetic relationship of the genus Populus. (Hamzeh & Dayanandan, 2004)Maximum likelihood tree based on three noncoding regions of trnT-trnF of cpDNA sequences from Popu-lus species. * Numbers below branches show bootstrap percentage values. * A, Aigeiros; P, Populus; T, Tacamahaca.? 371.000.00 0.25 0.50 0.7556   P. euphratica171  P. wilsonii27   P. ciliata29   P. ciliata9    P. angustofolia8    P. angustifolia140  P. suaveolens142  P. suaveolens25   P. cathayana26   P. cathayana145  P. szechuanica146  P. szechuanica147  P. szechuanica10   *P. balsamifera63   P. koreana65   P. koreana64   P. koreana66   P. koreana67   P. koreana68   P. koreana88   P. maximowiczii89   P. maximowiczii94   P. maximowiczii95   P. maximowiczii86   P. maximowiczii87   P. maximowiczii96   P. maximowiczii82   P. maximowiczii84   P. maximowiczii85   P. maximowiczii90   P. maximowiczii91   P. maximowiczii92   P. maximowiczii93   P. maximowiczii167  P. trichocarpa161  P. trichocarpa168  P. trichocarpa162  P. trichocarpa163  P. trichocarpa158  P. trichocarpa157  P. trichocarpa165  P. trichocarpa159  P. trichocarpa160  P. trichocarpa70   *P. lasiocarpa76   *P. laurifolia141  *P. suaveolens143  *P. suaveolens31   *P. ciliata128  *P. sieboldii155  *P. tremuloides148  *P. szechuanica14   P. balsamifera11   P. balsamifera169  P. tristis12   P. balsamifera13   P. balsamifera15   P. balsamifera subcordata candicans18   P. candicans aurora175  *P. yunnanensis19   P. candicans77   *P. laurifolia28   *P. ciliata164  *P. trichocarpa166  *P. trichocarpa78   P. laurifolia79   P. laurifolia80   P. laurifolia129  P. simonii131  P. simonii137  P. simonii139  P. simonii138  P. simonii132  P. simonii133  P. simonii134  P. simonii135  P. simonii130  P. simonii136  P. simonii172  P. yunnanensis174  P. yunnanensis173  P. yunnanensis yunnanensis176  P. yunnanensis69 P. lasiocarpa72 P. lasiocarpa73 P. lasiocarpa74 P. lasiocarpa75 P. lasiocarpa170 P. violascens55   P. deltoides34   P. deltoides49   P. deltoides deltoides43   P. deltoides37   P. deltoides41   P. deltoides48   P. deltoides deltoides38   P. deltoides52   P. deltoides occidentalis54   P. deltoides deltoides45   P. deltoides51   P. deltoides deltoides35   P. deltoides42   P. deltoides44   P. deltoides53   P. deltoides deltoides46   P. deltoides50   P. deltoides deltoides47   P. deltoides deltoides36   P. deltoides40   P. deltoides39   P. deltoides58   P. fremontii59   P. fremontii wislizeni60   P. fremontii wislizeni sargent33   *P. deltoides30   *P. ciliata71   *P. lasiocarpa83   *P. maximowiczii57   P. euramericana62   P. fremontii61   P. fremontii117  P. nigra nigra120  P. nigra nigra125  P. nigra nigra119  P. nigra nigra121  P. nigra nigra118  P. nigra nigra122  *P. nigra italica123  P. nigra nigra124  P. nigra nigra177  Populus - blind test126  P. nigra nigra178  Populus - blind test98   P. nigra103  P. nigra101  P. nigra102  P. nigra104  P. nigra99   P. nigra100  P. nigra109  P. nigra italica105  P. nigra110  P. nigra italica111  P. nigra italica112  P. nigra italica114  P. nigra italica113  P. nigra italica108  P. nigra italica115  P. nigra italica107  P. nigra127  P. nigra116  P. nigra italica144  *P. suaveolens16   P. berolinensis17   P. berolinensis81   *P. laurifolia106  *P. nigra1    P. alba boleana6    P. alba7    P. alba tomentosa2    P. alba3    P. alba4    P. alba5    P. alba20   P. canescens23   P. canescens22   P. canescens156  *P. tremuloides21   P. canescens32   P. davidiana davidiana149  P. tremula151  P. tremula153  P. tremula152  P. tremula154  P. tremuloides150  P. tremula erecta24   *P. cathayana179  Salix180  Salix181  Salix97   P. mexicanaspecies sectionsP. wilsoniiP. ciliataP. angustofoliaP. euphraticaP. suaveolens/P. cathayanaP. szechuanicaP. koreanaP. maximowicziiP. trichocarpaP. balsamiferaP. candicansP. laurifoliaP. simoniiP. tristisP. deltoidesP. yunnanensisP. lasiocarpaP. violascensP. fremontii/P. euramericanaP. nigraP. berolinensisP. albaP. canescensP. tremula/P. tremuloidesP. davidianaP. mexicanaLeuceAigeirosSalix (outgroup)AbasoTacamahaca /LeucoidesTuranga123456Fig. 1 Dendrogram of Populus and Salix accessions, constructedfrom AFLP fragment similarities (Dice coefficient), with theUPGMA clustering method, and based on AFLP markers resolvedby five primer combinations (EcoRI+ATA/MseI+ACAA, EcoR-I+ATA/MseI+ACAC, EcoRI+ATA/MseI+ACAG and EcoR-I+ATA/MseI+ACAT, EcoRI+AAA/MseI+ACAT). Accessionsmarked with an asterisk are potentially mislabeled species orhybrids (see text and Table 2). Species are marked by brackets andarrows, whereas lines group sections1447Figur  3-1-4. Dendrogram of Populus accessions with Salix as an utgroup, constructed from AFLP fragment similarities (Dice coefficient) with the UPGMA clustering method, and based on AFLP arkers resolved by five primer combinations. (Cerv ra et al., 2005)* Accessions marked with an asterisk are potentially mislabeled species or hybrids. Species are marked by brackets and arrows, whereas lines group sections. ? 38separate from P. nigra that was originally classified as amember of the Aigeiros section. The P. deltoides clusterwas genetically closely related to the accessions classifiedas P. fremontii Wats. and P. candicans and, to a lesserextent, to P. yunnanensis (group 5) and species fromgroups 2, 3, and 6 of the Tacamahaca/Leucoides section.As mentioned previously, P. candicans represents inter-specific hybrids of P. deltoides ? P. balsamifera (Ta-ble 3). Remarkably, all P. fremontii accessions hadAFLP patterns typical for P. deltoides ? P. nigra hy-brids and grouped with Populus ? canadensis (synonymPopulus ? euramericana Moench), intermediate be-tween the P. deltoides and P. nigra groups (Fig. 1).Therefore, these accessions were genetically associatedwith the group consisting of P. nigra and with Populusberolinensis, another interspecific hybrid of P. nigra.The four species (P. alba, P. tremula, P. tremuloides,and P. davidiana) and interspecific hybrids (Popu-lus ? canescens) from the Leuce section, clustered in asingle distinct group, which, with the exception of P.mexicana and Salix accessions, was the most distinctfrom the groups of the other Populus species (Fig. 1).Populus ? canescens accessions clustered between P.alba and P. tremula, as was to be expected, since they areinterspecific hybrids between the two species (Rajoraand Dancik 1992).Interspecific relationships were also studied with PCO(Fig. S1). The first PCO explains 18% of the total var-iation of the Populus species. The relative position ofspecies and interspecific hybrids was consistent with thephenetic analysis. However, some of the species includedin the previously described large meta-group were notdistinguishable: P. trichocarpa and its associated hy-brids, P. balsamifera, P. tristis, P. laurifolia, as well as P.ciliata.Intraspecific relationshipsAs expected, the intraspecific GS values were higherthan the interspecific ones, and their estimation de-pended on the number of accessions analyzed for eachFig. 2 The single most parsimonious bifurcating unrooted tree, based on the Wagner method, representing the phylogeny of Populus.Plain and circled numbers correspond to accession codes (Table 2) and bootstrap values (only those above 50% are shown for mainbranches, grouping several species), respectively1451Figure 3-2. The single most parsimonious bifurcating unrooted tree, based on the Wagner method, represen ing the phylogeny of Populus. Plain and circled numbers correspond to acces-sion codes (Table 3-1) and bootstrap values (only those above 50% are shown for main branches, grouping several species), respectively. (Cervera et al. 2005)? 39Table 2 Information on individual poplar accessions analyzedAccessionnumberSpecies Variety orcultivarClonenameOrigin Provider New tentativeassignatione1 P. alba boleana CN2 P. alba 603.02 FR, INRA3 P. alba A.L05.010 IT IT, ISP4 P. alba BO-1 IT IT, ISP5 P. alba Villafranca IT IT, ISP6 P. alba B BE BE, VIB-UG7 P. alba tomentosa FR, INRA8 P. angustifolia 46/69 DE, HLFWW9 P. angustifolia ANG FR, INRA10 P. balsamiferac 1-5 US, MN BE, IBW P. szechuanica11 P. balsamifera 8-6 US, MN BE, IBW12 P. balsamifera 21-7 US, WI BE, IBW13 P. balsamifera 15-5 US, MI BE, IBW14 P. balsamifera 19-2 US, MI BE, IBW15 P. balsamifera subcordata candicans BE, IBW P. candicans16 Populus ? berolinensis BE, arboretumKalmthout17 Populus ? berolinensis 19870019 FR BE, arboretumMeise18 P. candicans aurora 19860364 BE, arboretumMeise19 P. candicans 19810762 BE, arboretumMeise20 Populus ? canescens 90000054 BE, arboretumMeise21 Populus ? canescens limbrichterbos BE, arboretumKalmthout22 Populus ? canescens Grauwe abeel 1 BE, IBW23 Populus ? canescens Grauwe abeel 2 BE, IBW24 P. cathayanac E6 IE, Teagasc unclassified25 P. cathayanab 306-52 DE, HLFWW26 P. cathayana US, WashingtonUniversity27 P. ciliata 72-085 IT, ISP28 P. ciliatac 65-017 IT, ISP P. trichocarpa ?P. maximowiczii29 P. ciliataa 72-085 FR, INRA30 P. ciliatac 102L7 IE, Teagasc Populus ? canadensis31 P. ciliatac D1D4E3 IE, Teagasc intrasectionalTacamahaca hybrid32 P. davidiana davidiana FR, INRA33 P. deltoidesc V12 US, IL BE, IBW Populus ? canadensis34 P. deltoides V1 CA, ONT BE, IBW35 P. deltoides V2 CA, ONT BE, IBW36 P. deltoides V3 US, MN BE, IBW37 P. deltoides V7B US, MO BE, IBW38 P. deltoides S174-1 US, ND BE, IBW39 P. deltoides S197-1 CA, ON BE, IBW40 P. deltoides S329-31 US, OH BE, IBW41 P. deltoidesb S333-53 US, MI BE, IBW42 P. deltoides S235-3 US, IL BE, IBW43 P. deltoides S193-1 US, ND BE, IBW44 P. deltoides DO-006 US, TX IT, ISP45 P. deltoides DI-180A US, OH IT, ISP46 P. deltoides S336-4 US, CT BE, IBW47 P. deltoides deltoides D37 CA, ONg CA, O.P. Rajora48 P. deltoides deltoides D43 CA, ONg CA, O.P. Rajora49 P. deltoides deltoides D68 US, INg CA, O.P. Rajora50 P. deltoides deltoides D70 US, ILg CA, O.P. Rajora51 P. deltoides deltoides D56 CA, ONg CA, O.P. Rajora52 P. deltoides occidentalis D87 US, KSg CA, O.P. Rajora53 P. deltoides deltoides D109 US, MSg CA, O.P. Rajora54 P. deltoides deltoides D121 US, ILg CA, O.P. Rajora55 P. deltoides S9-2 US BE, IBW56 P. euphratica CN VIB-UG1443Table 3-1. Information on individual poplar accessions of 32 typical Populus species and hybrids within 5 main sections analysed in Fig. 3-1-4 & Figure 3-2. (Cervera, 2005)? 40Table 2 (Contd.)AccessionnumberSpecies Variety orcultivarClonenameOrigin Provider New tentativeassignatione114 P. nigra ?Italica? PI88-058 TR IT, ISP115 P. nigra ?Italica? PI88-063 BG IT, ISP116 P. nigra ?Italica? Zaragoza ES ES, SIA117 P. nigra nigra N13 CZ h CA, O.P. Rajora118 P. nigra nigra N19 NLh CA, O.P. Rajora119 P. nigra nigra N20 FRh CA, O.P. Rajora120 P. nigra nigra N29 NLh CA, O.P. Rajora121 P. nigra nigra N40 NLh CA, O.P. Rajora122 P. nigrab nigra N84 DEh CA, O.P. Rajora123 P. nigrab nigra N85 DEh CA, O.P. Rajora124 P. nigra nigra N96 CZ h CA, O.P. Rajora125 P. nigra nigra N100 CZ h CA, O.P. Rajora126 P. nigra nigra N102 CZ h CA, O.P. Rajora127 P. nigra Ghoy BE BE, IBW128 P. sieboldiic Sie GB IE, Teagasc P. trichocarpa ?P. balsamifera129 P. simonii 1/9 BE, IBW130 P. simonii 81-001-003 CN IT, ISP131 P. simonii 81-002-003 CN IT, ISP132 P. simonii 108/49 DE, HLFWW133 P. simoniib 57/65 DE, HLFWW134 P. simonii 147/65 DE, HLFWW135 P. simoniib 141/66 DE, HLFWW136 P. simonii 58/90 DE, HLFWW137 P. simonii 59/90 DE, HLFWW138 P. simonii 60/90 DE, HLFWW139 P. simonii fastigiata BE, VIB-UG140 P. suaveolens 21/65 DE, HLFWW141 P. suaveolensc 15/74 DE, HLFWW P. trichocarpa ?P. balsamifera142 P. suaveolensa 21/65 DE, HLFWW143 P. suaveolensa,c 15/74 DE, HLFWW P. trichocarpa ?P. balsamifera144 P. suaveolensc 20/65 DE, HLFWW P. ? canadensis ?P. nigra145 P. szechuanica SZC FR, INRA146 P. szechuanica 275/49 DE, HLFWW147 P. szechuanicab 67/65 DE, HLFWW148 P. szechuanicac 144/65 DE, HLFWW P. balsamifera149 P. tremula 130-19 FR, INRA150 P. tremula erecta BE, arboretumBeveren151 P. tremula 1H BE, IBW152 P. tremula 2H BE, IBW153 P. tremula 3H BE, IBW154 P. tremuloides 210-22 FR, INRA155 P. tremuloidesc HI-10 IE, Teagasc intrasectionalTacamahaca hybrid156 P. tremuloidesc BE, arboretumKalmthoutPopulus ? canescens157 P. trichocarpa FPL FR, INRA158 P. trichocarpa 19-73 FR, INRA159 P. trichocarpa 36-77 FR, INRA160 P. trichocarpa 101-74 FR, INRA161 P. trichocarpa S3-31 BE, IBW162 P. trichocarpa V509 BE, IBW163 P. trichocarpa V510 BE, IBW164 P. trichocarpac ?Fritzi Pauley? V235 US, WA BE, IBW P. trichocarpa ?P. maximowiczii165 P. trichocarpab 212-161 FR, INRA166 P. trichocarpaa,c ?Fritzi Pauley? BE, arboretumKalmthoutP. trichocarpa ?P. maximowiczii167 P. trichocarpa ?Trichobel? BE, IBW168 P. trichocarpa ?Columbia river? V24 US, OR BE, IBW169 P. tristis 24/65 DE, HLFWW1445a le 3-1. (Continued).? 41sified accessions were assigned to a more likely speciesor hybrid, based on the AFLP patterns (Table 2). Fourmisclassified accessions could be assigned to certainspecies groups, two of which (148 and 175) shared aGS of > 0.98 with the other species (14 and 19,respectively). These accessions were included into thedataset to calculate interspecific as well as intraspecificGS values (Table 2; all, except those designated asunclassified or hybrid, were included). Interspecific GSranges between two species a and b were calculatedfrom all pair-wise GS values between all accessionsfrom species a and all accessions from species b.Intraspecific GS values give the range of all pair-wiseGS values among accessions of a single species. The GSmatrix, based on the individual accessions, is availableat http://www.psb.ugent.be/!vesto and the interspecificand intraspecific GS matrix is presented in Table 3. Toverify the consistency of cluster analysis, a seconddendrogram was constructed, using AFLP fragmentsimilarities (Dice coefficient) with the UPGMA clus-tering method, without including the misclassifiedaccessions and the accessions with GS ? 0.98 (Fig. S2,Electronic supplementary material).Phylogenetic analysis, performed on the latter repre-sentative and non-redundant set of accessions (GS< 0.98), was carried out with the MIX program of thePHYLIP software package version 3.57c (Felsenstein1993), in order to construct the single most parsimoni-ous tree based on Wagner?s method (Fig. 2). The datawere bootstrapped, to assess how strongly phylogeneticdata supported clades in this tree, with SEQBOOT (100bootstrapped data files) and followed by the MIX andCONSENSE software packages of PHYLIP Version3.57c. The single most parsimonious bifurcating un-rooted tree was constructed with the TREEVIEW soft-ware package (Page 1996).ResultsDendrograms obtained using Dice and Jaccard similar-ity coefficients were identical (data not shown). Thecorrelation between the Dice and Jaccard similaritymatrices and their co-phenetic matrices was very high(0.94 and 0.93, respectively), with an associated p-valueof 0.002 (one-tailed) that indicated a very good fit of theTable 2 (Contd.)AccessionnumberSpecies Variety orcultivarClonenameOrigin Provider New tentativeassignatione170 P. violascens 19860054 UK BE, arboretumMeise171 P. wilsonii 19820416 DE BE, arboretumMeise172 P. yunnanensis 82001 FR, INRA173 P. yunnanensis yunnanensis FR, INRA174 P. yunnanensisb V535 BE, IBW175 P. yunnanensisc BE, arboretumBeverenP. candicans176 P. yunnanensis BE, arboretumBeveren177 Populus-unknownd 22616 BE, arboretumKalmthoutP. nigra178 Populus-unknownd 22031 BE, arboretumKalmthoutP. nigra179 Salix BE, VIB-UG180 Salix BE, VIB-UG181 Salix 22010 BE, arboretumKalmthoutCountries are abbreviated according to ISO 3166-1-Alpha-2 code (BE Belgium, BG Bulgaria, CA Canada [ON Ontario], CN China, CZCzech Republic, DE Germany, DK Denmark, ES Spain, FR France, IE Ireland, IT Italy, JP Japan, MX Mexico, NL The Netherlands,TR Turkey, GB United Kingdom, US United States [IL Illinois, IN Indiana, KS Kansas, MN Minnesota, MO Missouri, MS Mississippi,ND North Dakota, OH Ohio, OR Oregon, TX Texas, WA Washington State, WI Wisconsin], YU Yugoslavia). HLFWW Hessian ForestCenter for Management, Planning, Research and Ecology (Mu?nden, Germany), IBW Instituut voor Bosbouw en Wildbeheer (Gera-ardsbergen, Belgium), INRA Institut National de la Recherche Agronomique (Orle?ans, France), ISP Istituto di Sperimentazione per laPioppicoltura (Casale Monferrato, Italy), SIA Servicio de Investigacio?n Agroalimentaria Diputacion General de Arago?n (Zaragoza,Spain), Teagasc Irish Agriculture and Food development Authority (Dublin, Ireland), VIB-UG Vlaams Interuniversitair Instituut voorBiotechnologie-Universiteit Gent (Gent, Belgium). Accessions in bold were used to perform the phylogenetic analysisa Samples known to be duplicates before the start of the analysis and confirmed by AFLPb Accessions showing GS of ? 0.98 based on AFLP fragment similaritiesc Possibly mislabeled and/or misclassified accessions based on AFLP analysisd Based on morphological descriptors (blind test). These clones showed AFLP patterns typical of P. nigrae Tentative assignation of misclassified accessions based on AFLP patterns, GS values and the dendrogram in Fig. 1f Information on the origin of P. maximowiczii accessions is provided in Rajora (1988)g Information on the origin of P. deltoides accessions is provided in Rajora (1989a)h Information on the origin of P. nigra accessions is provided in Rajora (1989b)1446ble 3-1. (Continued). * Countries are abbreviated according to ISO 3166-1-Alpha-2 code (BE Belgium, BG Bulgaria, CA Canada [ON Ontario], CN China, CZ Czech Republic, DE Germany, DK Den-mark, ES Sp in, FR Fr ce, IE Ireland, IT Italy, JP Japan, MX Mexico, NL The Netherlands, TR Turkey, GB United Kingdom, US United States [IL Illinois, IN Indiana, KS Kansas, MN Minnesota, MO Missouri, MS Mis-sissippi, ND North Dako a, OH Ohi , OR Oregon, TX Texas, WA Washi gton State, WI Wisconsi ], YU Yugosla-via). * HLFWW Hessian Forest Center for Management, Planning, Research and Ecology (Munden, Germany),    IBW Instituut voor Bosbouw en Wildbeheer (Geraardsbergen, Belgium),    INRA Institut National de la Recherche Agronomique (Orleans, France),    ISP Istituto di Sperimentazione per la Pioppicoltura (Casale Monferrato, Italy), SIA Servicio de Investigacion Agroalimentaria Diputacion General de Aragon (Zaragoza, Spain), Teagasc Irish Agriculture and Food development Authority (Dublin, Ireland), VIB-UG Vlaams Interuniversitair Instituut voor Biotechnologie-Universiteit Gent (Gent, Belgium). * Accessions in bold were used to perform the phylogenetic analysisa. Samples known to be duplicates before the start of the analysis and confirmed by AFLP b. Accessions sho ing GS of ? 0.98 based on AFLP fragment similarities c. Poss bly mislabeled and/or misclassified acc ssions bas d on AFLP an lysis . Based n morphological d scriptors (blind test). Th se lones showed AFLP patterns typical of P. nigra e. Tentative assignation of misclassified accessions based on AFLP patterns, GS values and the dendrogram in Fig. 3-1-3? 42Table3InterspecificandintraspecificGSamongpairsofPopulusandSalix,withaveragesimilaritiesbetweenparenthesesP.euphratica(1)P.ciliata(2)P.lasiocarpa(5)P.alba(7)P.davidiana(1)P.sieboldii(1)P.tremula(5)P.tremuloides(1)P.angustifolia(2)P.balsamifera(5)P.candicans(4)P.cathayana(2)P.laurifolia(3)P.maximowiczii(14)P.euphratica?P.ciliata0.50?0.51(0.51)0.99P.lasiocarpa0.46?0.47(0.47?0.01)0.56?0.59(0.58?0.01)0.90?0.99(0.95?0.03)P.alba0.29?0.45(0.36?0.05)0.29?0.4(0.32?0.04)0.34?0.44(0.40?0.03)0.70?0.95(0.81?0.06)P.davidiana0.400.350.36?0.38(0.38?0.01)0.57?0.65(0.60?0.03)?P.sieboldii0.480.620.60?0.62(0.61?0.01)0.39?0.47(0.44?0.03)0.43?P.tremula0.34?.047(0.40?0.04)0.36?0.43(0.39?0.02)0.35?0.49(0.41?0.04)0.53?0.70(0.59?0.04)0.71?0.78(0.74?0.03)0.38?0.51(0.46?0.05)0.67?0.86(0.75?0.07)P.tremuloides0.390.370.37?0.43(0.41?0.02)0.52?0.66(0.59?0.05)0.710.470.63?0.90(0.77?0.11)?P.angustifolia0.54?0.60(0.57)0.72?0.76(0.74?0.02)0.57?0.66(0.62?0.03)0.34?0.55(0.43?0.06)0.40?0.45(0.43)0.65?0.67(0.66)0.4?0.50(0.45?0.03)0.42?0.43(0.42)0.86P.balsamifera0.46?0.53(0.50?0.03)0.58?0.67(0.64?0.03)0.57?0.65(0.62?0.02)0.33?0.47(0.39?0.03)0.35?0.43(0.40?0.03)0.80?0.88(0.85?0.03)0.31?0.51(0.43?0.06)0.40?0.47(0.45?0.03)0.61?0.72(0.67?0.03)0.89?0.99(0.94?0.03)P.candicans0.51?.052(0.51?0.01)0.67?0.72(0.69?0.02)0.66?0.70(0.68?0.01)0.37?0.52(0.41?0.05)0.44?0.47(0.45?0.01)0.80?0.85(0.82?0.02)0.35?0.49(0.45?0.05)0.44?0.45(0.45?0.01)0.64?0.73(0.68?0.03)0.75?0.87(0.81?0.03)0.94?1.00(0.97?0.02)P.cathayana0.440.67?0.73(0.70?0.03)0.54?0.63(0.58?0.03)0.30?0.45(0.34?0.05)0.38?0.41(0.40)0.65?0.70(0.68)0.32?0.46(0.40?0.04)0.40?0.43(0.42)0.59?0.69(0.64?0.04)0.62?0.72(0.68?0.03)0.65?0.73(0.69?0.03)0.89P.laurifolia0.39?0.40(0.40?0.01)0.63?0.65(0.64?0.01)0.47?0.54(0.51?0.02)0.26?0.38(0.31?0.03)0.33?0.35(0.34?0.01)0.67?0.68(0.68?0.01)0.31?0.41(0.37?0.03)0.36?0.37(0.37?0.01)0.56?0.61(0.58?0.02)0.60?0.66(0.64?0.02)0.61?0.67(0.63?0.02)0.69?0.72(0.70?0.02)0.99?1.00(0.99?0.01)P.maximowiczii0.45?0.52(0.47?0.02)0.69?0.74(0.71?0.02)0.52?0.62(0.58?0.02)0.27?0.49(0.35?0.05)0.37?0.44(0.42?0.02)0.60?0.69(0.66?0.03)0.30?0.49(0.41?0.04)0.40?0.44(0.42?0.02)0.62?0.73(0.68?0.03)0.59?0.73(0.67?0.03)0.62?0.75(0.68?0.03)0.73?0.86(0.81?0.03)0.64?0.71(0.68?0.02)0.73?1.00(0.85?0.06)P.koreana0.44?0.45(0.45?0.01)0.67?0.69(0.68?0.01)0.55?0.61(0.58?0.02)0.31?0.47(0.35?0.05)0.41?0.43(0.42?0.01)0.63?0.67(0.65?0.01)0.36?0.45(0.41?0.02)0.41?0.45(0.42?0.02)0.63?0.72(0.68?0.03)0.60?0.71(0.67?0.03)0.65?0.70(0.67?0.02)0.78?0.84(0.82?0.02)0.65?0.71(0.68?0.02)0.79?0.91(0.86?0.03)P.simonii0.34?0.46(0.39?0.04)0.48?0.62(0.55?0.05)0.49?0.63(0.56?0.03)0.27?0.45(0.34?0.04)0.38?0.44(0.41?0.02)0.53?0.62(0.57?0.02)0.36?0.45(0.45?0.03)0.33?0.41(0.39?0.02)0.54?0.62(0.59?0.03)0.50?0.69(0.59?0.03)0.60?0.68(0.63?0.02)0.56?0.73(0.65?0.06)0.50?0.58(0.55?0.03)0.49?0.72(0.62?0.06)P.suaveolens0.440.70?0.73(0.72?0.01)0.57?0.63(0.60?0.01)0.30?0.46(0.35?0.05)0.410.700.37?0.47(0.41?0.03)0.430.60?0.67(0.64?0.04)0.63?0.72(0.69?0.04)0.69?0.73(0.70?0.01)0.91?0.98(0.94?0.04)0.67?0.70(0.69?0.01)0.75?0.84(0.81?0.03)P.szechuanica0.45?0.49(0.47?0.02)0.67?0.70(0.68?0.01)0.57?0.61(0.59?0.01)0.30?0.47(0.34?0.05)0.37?0.39(0.38?0.01)0.64?0.71(0.66?0.03)0.32?0.48(0.39?0.04)0.39?0.44(0.40?0.03)0.63?0.71(0.66?0.03)0.63?0.73(0.69?0.03)0.66?0.72(0.68?0.02)0.82?0.86(0.84?0.02)0.69?0.76(0.71?0.02)0.70?0.82(0.76?0.03)P.yunnanensis0.42?0.45(0.44?0.02)0.62?0.65(0.64?0.02)0.58?0.66(0.62?0.03)0.32?0.49(0.39?0.04)0.45?0.48(0.46?0.02)0.63?0.67(0.65?0.02)0.36?0.51(0.45?0.05)0.46?0.49(0.48?0.02)0.61?0.68(0.65?0.03)0.56?0.69(0.64?0.03)0.66?0.72(0.68?0.02)0.68?0.76(0.73?0.03)0.55?0.61(0.59?0.02)0.62?0.75(0.69?0.04)P.trichocarpa0.40?0.50(0.48?0.03)0.62?0.70(0.67?0.02)0.58?0.75(0.65?0.03)0.30?0.48(0.40?0.04)0.38?0.47(0.41?0.02)0.82?0.89(0.86?0.02)0.32?0.55(0.45?0.05)0.41?0.51(0.46?0.04)0.62?0.76(0.70?0.04)0.71?0.87(0.81?0.04)0.74?0.87(0.80?0.03)0.63?0.78(0.69?0.03)0.63?0.68(0.66?0.01)0.58?0.76(0.67?0.04)P.deltoides0.41?0.49(0.44?0.02)0.52?0.61(0.56?0.02)0.61?0.72(0.66?0.02)0.30?0.44(0.37?0.03)0.37?0.45(0.40?0.02)0.57?0.64(0.59?0.02)0.28?0.43(0.37?0.04)0.39?0.42(0.41?0.01)0.54?0.69(0.61?0.04)0.53?0.66(0.60?0.03)0.68?0.81(0.75?0.03)0.54?0.71(0.59?0.03)0.49?0.60(0.53?0.02)0.53?0.66(0.60?0.03)P.?euramericana0.37?0.45(0.43?0.03)0.53?0.64(0.59?0.03)0.53?0.64(0.59?0.02)0.26?0.42(0.35?0.04)0.35?0.42(0.39?0.02)0.58?0.65(0.63?0.02)0.27?0.46(0.38?0.04)0.36?0.40(0.39?0.02)0.58?0.71(0.65?0.04)0.51?0.67(0.61?0.04)0.64?0.79(0.74?0.03)0.50?0.66(0.60?0.04)0.50?0.56(0.53?0.01)0.52?0.68(0.61?0.03)P.nigra0.41?0.48(0.45?0.02)0.53?0.61(0.57?0.02)0.45?0.53(0.49?0.01)0.22?0.38(0.29?0.03)0.30?0.40(0.34?0.02)0.59?0.65(0.62?0.02)0.31?0.42(0.35?0.03)0.29?0.39(0.32?0.02)0.58?0.67(0.61?0.02)0.51?0.66(0.59?0.03)0.57?0.67(0.62?0.02)0.49?0.61(0.55?0.03)0.50?0.55(0.52?0.02)0.50?0.64(0.57?0.03)P.violascens0.490.690.79?0.83(0.82?0.02)0.36?.46(0.39?0.04)0.410.690.40?0.46(0.42?0.02)0.430.67?0.70(0.68)0.61?0.69(0.67?0.03)0.77 (?0.01)0.70 (0.70)0.58?0.59(0.58?0.01)0.65?0.75(0.71?0.04)P.wilsonii0.580.61?0.62(0.61)0.58?0.61(0.59?0.01)0.38?0.47(0.42?0.03)0.410.660.39?0.48(0.44?0.03)0.410.650.59?0.68(0.65?0.04)0.59?0.63(0.61?0.02)0.56?0.59(0.57)0.460.55?0.65(0.58?0.03)P.tristis0.510.66?0.67(0.66)0.61?0.65(0.63?0.01)0.37?0.45(0.41?0.03)0.400.890.36?0.51(0.45?0.06)0.500.71?0.72(0.71)0.88?0.96(0.93?0.03)0.80?0.87(0.83?0.03)0.67?0.72(0.70)0.63?0.64(0.63?0.01)0.65?0.73(0.69?0.03)P.berolinensis0.41?0.43(0.42?0.01)0.60?0.66(0.63?0.03)0.49?0.54(0.51?0.02)0.26?0.37(0.33?0.03)0.31?0.37(0.33?0.03)0.60?0.64(0.62?0.02)0.33?0.40(0.37?0.02)0.34?0.35(0.35?0.01)0.60?0.64(0.61?0.02)0.51?0.63(0.59?0.04)0.62?0.67(0.63?0.02)0.59?0.69(0.65?0.04)0.64?0.68(0.66?0.01)0.52?0.69(0.63?0.04)P.?canescens0.35?0.39(0.37?0.2)0.31?0.41(0.38?0.04)0.37?0.43(0.40?0.02)0.63?0.79(0.72?0.04)0.61?0.66(0.64?0.02)0.44?0.46(0.45?0.01)0.57?0.72(0.65?0.05)0.58?0.64(0.61?0.03)0.42?0.5(0.47?0.03)0.34?0.46(0.41?0.03)0.36?0.46(0.42?0.04)0.33?0.42(0.38?0.03)0.31?0.36(0.34?0.02)0.29?0.41(0.35?0.03)P.mexicana0.140.13 (0.13)0.13?0.17(0.14?0.02)0.05?0.14(0.10?0.04) 3-2. Interspecific and intraspecific GS among pairs of Populus and Salix, with average similarities between parentheses. (Cervera, 2005)? 43Table3(Contd.)P.koreana(6)P.simonii(11)P.suaveolens(2)P.szechuanica(4)P.yunnanensis(4)P.trichocarpa(10)P.deltoides(22)Populus?canadensis(10)P.nigra(31)P.violascens(1)P.wilsonii(1)P.tristis(1)P.?berolinensis(3)P.?canescens(5)P.mexicana(1)P.euphraticaP.ciliataP.lasiocarpaP.albaP.davidianaP.sieboldiiP.tremulaP.tremuloidesP.angustifoliaP.balsamiferaP.candicansP.cathayanaP.laurifoliaP.maximowicziiP.koreana0.85?1.00(0.92?0.07)P.simonii0.51?0.74(0.63?0.06)0.75?1.00(0.83?0.07)P.suaveolens0.80?0.84(0.83?0.01)0.57?0.73(0.64?0.06)0.98P.szechuanica0.74?0.79(0.76?0.01)0.52?0.71(0.61?0.07)0.80?0.83(0.81?0.01)0.87?1.00(0.93?0.05)P.yunnanensis0.67?0.71(0.69?0.01)0.67?0.79(0.74?0.04)0.71?0.76(0.74?0.02)0.63?0.67(0.66?0.02)0.91?1.00(0.95?0.03)P.trichocarpa0.61?0.74(0.68?0.03)0.54?0.72(0.63?0.04)0.65?0.78(0.70?0.03)0.60?0.74(0.66?0.03)0.58?0.75(0.69?0.04)0.91?1.00(0.95?0.03)P.deltoides0.57?0.65(0.60?0.02)0.51?0.66(0.56?0.02)0.56?0.72(0.61?0.03)0.57?0.72(0.61?0.02)0.57?0.71(0.62?0.02)0.54?0.68(0.60?0.03)0.89?0.99(0.94?0.02)P.?canadensis0.53?0.66(0.61?0.03)0.54?0.73(0.61?0.04)0.54?0.66(0.62?0.03)0.50?0.64(0.58?0.03)0.57?0.71(0.65?0.02)0.54?0.71(0.63?0.03)0.67?0.83(0.75?0.03)0.78?1.00(0.87?0.02)P.nigra0.53?0.64(0.59?0.02)0.48?0.78(0.59?0.06)0.52?0.61(0.57?0.02)0.53?0.62(0.57?0.02)0.53?0.63(0.56?0.02)0.54?0.68(0.61?0.03)0.45?0.60(0.53?0.02)0.68?0.87(0.76?0.03)0.84?1.00(0.93?0.03)P.violascens0.71?0.72(0.72?0.01)0.56?0.65(0.61?0.03)0.70?0.72(0.71)0.65?0.69(0.68?0.02)0.69?0.73(0.72?0.02)0.66?0.76(0.71?0.03)0.64?0.71(0.67?0.03)0.59?0.68(0.65?0.03)0.52?0.58(0.55?0.02)?P.wilsonii0.54?0.59(0.56?0.02)0.43?0.55(0.49?0.05)0.56?0.59(0.58)0.59?0.62(0.61?0.01)0.50?0.54(0.52?0.02)0.59?0.68(0.64?0.03)0.46?0.55(0.50?0.02)0.43?0.52(0.49?0.03)0.45?0.54(0.49?0.02)0.58?P.tristis0.67?0.71(0.69?0.01)0.52?0.64(0.58?0.04)0.70?0.72(0.71)0.69?0.71(0.70?0.01)0.65?0.69(0.67?0.02)0.80?0.87(0.84?0.03)0.62?0.68(0.64?0.02)0.58?0.68(0.65?0.03)0.60?0.67(0.63?0.02)0.690.66?P.berolinensis0.57?0.73(0.67?0.05)0.55?0.74(0.62?0.05)0.63?0.68(0.66?0.02)0.55?0.63(0.59?0.03)0.60?0.68(0.63?0.02)0.57?0.69(0.64?0.03)0.48?0.55(0.52?0.02)0.67?0.78(0.72?0.03)0.73?0.85(0.79?0.02)0.61?0.65(0.63?0.02)0.45?0.51(0.48?0.03)0.59?0.64(0.61?0.03)0.84?0.94(0.88?0.05)P.canescens0.34?0.40(0.37?0.02)0.27?0.46(0.38?0.04)0.33?0.44(0.40?0.04)0.31?0.41(0.36?0.03)0.34?0.49(0.42?0.04)0.37?0.53(0.44?0.04)0.28?0.41(0.34?0.03)0.27?0.41(0.35?0.03)0.24?0.47(0.34?0.04)0.38?0.44(0.42?0.02)0.40?0.51(0.46?0.04)0.39?0.46(043?0.03)0.34?0.41(0.37?0.02)0.73?0.94(0.85?0.07)P.mexicana0.13?0.15(0.14?0.01)0.14?0.23(0.18?0.03)0.090.11?0.14(0.11?0.02)0.16?0.18(0.16?0.01)0.12?0.19(0.17?0.02)0.13?0.18(0.15?0.01)0.15?0.20(0.17?0.02)0.15?0.22(0.18?0.02) 3-2. (Continued).? 44Table 2. Overview of traits introduced into poplar via genetic engineering Species/hybrid Methods Transgenes" Resistance to herbicides P. alha x P grandidenlata Fillatti et al. (1987) amA P. tremula x P. alba De Block (1990) bar P. trichocarpa x P deltoides De Block (1990) har P. tremula x P. alba Devillard (1992) bar P. tremula x P. alba Brasileiro et al. (1991) cr.l'l-1 LeplC et al. (1992) P. tremula x P. alba Chupeau et al. (1994) crsl-J P. tremula x P. alba Chupeau et al. (1994) bar P. alba x P grandidentata Fillatti et al. (1987) aroA Resistance to insects P. alba X P grandidentata McCown ct al. (1991) c:rylA(a) P. nigra Tian et a!. (1993) crylA(c) P. tremula X P. tremuluides Lcplc ct al. (1992) c:ryllIA P. trem.ula x P. tremuloilies Brasileiro et al. (1991) ael Leple et al. (1992) P. alba x P. gralldidentata Klopfenstein et al. (1991) pinll Flower ueve\opmcnt P. tremuloides Nilsson et al. (1992) leafy Alteration of metabolism P. tremula x P. alba Lepl6 et al. (1992) ipt P. tremula x P. ailla Nilsson et al. (1992) iaaM, iaaH Characteristics Glyphosate resistance Basta resistancc Basta resistance Basta resistancc Chlorsulfuron resistance Chlorsulfuron rcsistance Basta resistance Glyphosate resistance MalacoSOI1111 disstria (LY' Lymantria dispar (L) LY/nantria di.l'par (L) Apuchemia cinerarius (L) Chrysomela tremulae (C) Chry.l'ome/a trenu.t/ae (C) Lymantria dis,Jar (L) I Precocious flowering Cytokinin content Hormone metabolism Referen"e FiHatti et al. (1987) De Block (1990) De Block (1990) Devillard (1992) Brasileiro eta!' (1992) Chupeau ct al. (1994) Chupeau ct al. (1994) Donahue et al. (1994) McCown et al. (1991) Wang et al. (1996) Cornu et al. (1996) Leplc et al. (1995) Heuchelin et al. (1997) Weigel and Nilsson (19lJ5) VOIl Schwartzenhcrg ct al. (1994) Thominen ct al. (1l)l)5) N W o c-< h t"" (1) -0 "" :=:. P. tremu/a x P. tremu/oides Nilsson et a!. (1992) role Hormone metabolism Nilsson et al. (1996) P. tremula x P. tremuloides Fladung et al. (1996) rolC Hormone metabolism Ahuja and Fladung (1996) P. tremula x P. alba Leple et a!. (1992) gar Glutathione metabolism Foyer et a!. (1995) P. tremula x P. alba Leple et a!. (1992) gshfl Glutathione metabolism Foyer et al. (1995); Strohm et a!. (1995); Arisi et al. (1997) P. tremula x P. alba Leple et a!. (1992) gshl Glutathione metabolism Noctor et a!. (1996) Arisi et al. (1997) P. rremula x P. alba Leple et a!. (1992) AS comt Lignin composition Van Doorsselaere et al. (1995) P. tremula x P. alba Leple et al. (1992) AS cad Lignin extractability Baucher et al. (1996a) Promoter studies P. tremula x P. grandidentutu Klopfenstein et al. (1991) ppin2/cat Wound-induced expression Klopfcnstein et al. (1991) P. tremula x P. alba Leple et al. (1992) pead/gus Xylem-specific expression Feuillet et al. (1995) P. tremula x P. tremuloides Nilsson et al. (1992) prolC/gus Seasonal-specific expression Nilsson et al. (1996) P. tremula x P. alba LepJe et a!. (1992) p-SAM/gus TIssue-specific expression Mijnsbrugge ct al. (1996) P. tremllia x P. tremu/oides Nilsson et a!. (1992) p35SIgus Constitutive expression Nilsson et al. (1996) Transposable clements P. tremu/a x P. tremu/aides Fladung et a!. (1996) p35S/Aclro/C Phenotype modification Ahuja and Fladung (1996) prbcsl Acl rolC " aroA: mutant EPSP synthase (glyphosate resistance); bar: phosphinotricin acetyl transferase (phosphinotricin resistance); cad: cinn3myllilcohol dchy-drogenllse; cat: ehloramphenieal acetyl transferase; comt: caffeic acid O-methyl transferase; crs1-1: mutant actetolactate synthase (chlorsulfuron resistance); cry/Arc), c:ryIA(a), cry/lIA: BacilluJ thuringiensis Il-endotoxins genes; gshl: y-glutamylcysteine synthetase; gshIl: glutathione synthetase; gor: glutathione reductasc; f3-glueuronidase; ipt: isopenteny transferase; iaaR: indole-3-aectamide hydrolase; illaM: tryptophan-2-mono-oxygenase; luxF2: lucifcrase; ael: cysteine proteinase inhibit()r from rice (oryzacystatin);p: promoter;pinl/: potato protease inhibitor II. b L: Lepidoptera; C: Coleoptera. ::;l I>l ::l <II 00  ::l dl 'U ::;l " ,-... '1:3 CIl 'U " n I;! .... Table 3-3. Overview of traits introduced into poplar via genetic engineering (Leple et al., 2000)? 45* aroA: mutant EPSP synthase (glyphosate resis-tance); bar: phosphinotricin acetyl transferase (phosphi-notricin resistance); cad: cinn3myllilcohol dchydrogenllse;cat: ehloramphenieal acetyl transferase; comt: caffeic acid O-methyl transferase; crs1-1: mutant actetolactate synthase (chlorsulfuron resistance); cryIA(c), cryIA(a), cryIlIA: BacilluJ thuringi-ensis ?-endotoxins genes; gshl: ?-glutamylcysteine synthetase; gshIl: glutathione synt etase; gor: glutathione reductasc; gus: ?-glueuronidase; ipt: isopenteny transferase; iaaH: indole-3-aectamide hydrolase; iaaM: tryptophan-2-mono-oxygenase; luxF2: lucifcrase; ocl: cysteine proteinase inhibi-tor from rice (oryzacystatin); p: promoter; pinll: potato protease inhibitor II. * L: Lepidoptera; C: Coleoptera.!"#$%&%'()*+,-./*+0110+2+!"#3(45"+6+745"+8+!"'$9(:;('4:+#$%;<9=5%:%">+?<@<:%A)<5;+45B+C%:$9>+$5+D=$54!"#$%&' !(' &)$' &$*)%!+!,-' &).&' 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ppendix IVTable 4. 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