Molecular genetics of growth and development in Populus. I. Triploidy in hybrid poplars

Summary While constructing a genetic linkage map of a hybrid poplar genome (Populus trichocarpa x P. deltoides), we identified several restriction fragment length polymorphismus (RFLPs) for which the parental trees are heterozygous. Although 8 of the 11 F₁ hybrid offspring inherited, as expected, single RFLP alleles from each parent, 3 F₁ trees in the mapping pedigree inherited both maternal alleles along with a single paternal allele at some loci. Aneuploidy or polyploidy in these 3 F₁ trees due to partial or complete nondisj unction during female gametogenesis is the simplest explanation for this finding. Of the 3 f₁ offspring with supernumerary RFLP alleles 2 have triploid nuclear DNA contents as measured by fluorescence flow cytometry; the 3rd F₁ with supernumerary alleles has a sub-triploid nuclear DNA content and is probably aneuploid. Among the tri/aneuploid hybrids, leaf quantitative traits either are skewed toward those values characteristic of the P. trichocarpa female parent (adaxial stomate density, petiole length: blade length ratio; abaxial color) or show transgressive variation (epidermal cell size). Abaxial leaf color was used to screen a large population of P. trichocarpa x P. deltoides hybrids for further evidence of tri/aneuploidy. In each case where a white abaxial leaf surface was observed and the nuclear DNA content measured, the hybrid proved to be tri/aneuploid. All sexually mature female triploids examined were sterile, although the inflorescences completed their development in the absence of embryo formation. The (probably) aneuploid F₁ hybrid is a fertile female. Of 15 female P. trichocarpa parents used in crosses to P. deltoides, 10 produced one or more tri/aneuploid hybrid offspring. In an intraspecific cross using a P. trichocarpa female that had produced triploid hybrids with five different P. deltoides males, no tri/aneuploid offpsring were found.     

QTLs for Woolly Poplar Aphid (Phloeomyzus passerinii L.) Resistance Detected in an Inter-Specific Populus deltoides x P. nigra Mapping Population

The genus Populus represents one of the most economically important groups of forest trees. It is composed by approximately 30 species used for wood and non-wood products, phytoremediation and biomass. Poplar is subjected to several biological and environmental threats although, compared to annual crops, we know far less about the genetic bases of biotic stress resistance. Woolly poplar aphid (Phloeomyzus passerinii) is considered a main pest of cultivated poplars in European and American countries. In this work we present two high density linkage maps in poplar obtained by a genotyping by sequencing (GBS) approach and the identification of QTLs involved in Ph. passerinii resistance. A total of 5,667 polymorphic markers (5,606 SNPs and 61 SSRs) identified on expressed sequences have been used to genotype 131 plants of an F1 population P ×canadensis obtained by an interspecific mate between Populus deltoides (resistant to woolly poplar aphid) and Populus nigra (susceptible to woolly poplar aphid). The two linkage maps, obtained following the two-way pseudo-testcross mapping strategy, have been used to investigate the genetic bases of woolly poplar aphid resistance. One major QTL and two QTLs with minor effects (mapped on LGV, LGXVI and LG XIX) explaining the 65.8% of the genetic variance observed in the progeny in response to Ph. passerinii attack were found. The high density coverage of functional markers allowed the identification of three genes belonging to disease resistance pathway as putative candidates for P. deltoides resistance to woolly poplar aphid. This work is the first report on genetic of woolly poplar aphid genetic resistance and the resistant loci associated markers identified represent a valuable tool in resistance poplar breeding programs.     

Rapid Activation of Phenylpropanoid Metabolism in Elicitor-Treated Hybrid Poplar (Populus trichocarpa Torr. & Gray x Populus deltoides Marsh) Suspension-Cultured Cells

Elicitor induction of phenylpropanoid metabolism was investigated in suspension-cultured cells of the fast-growing poplar hybrid (Populus trichocarpa Torr. & Gray × Populus deltoides Marsh) H11-11. Treatment of cells with polygalacturonic acid lyase or two fungal elicitors resulted in rapid and transient increases in extractable l-phenylalanine ammonia lyase and 4-coumarate:coenzyme A ligase enzyme activities. The substrate specificity of the inducible 4-coumarate:coenzyme A ligase enzyme activity appeared to differ from substrate specificity of 4-coumarate:coenzyme A ligase enzyme activity in untreated control cells. Large and transient increases in the accumulation of l-phenylalanine ammonia-lyase and 4-coumarate:coenzyme A ligase mRNAs preceded the increases in enzyme activities and were detectable by 30 minutes after the start of elicitor treatment. Chalcone synthase, cinnamyl alcohol dehydrogenase, and coniferin β-glucosidase enzyme activities were unaffected by the elicitors, but a large and transient increase in β-glucosidase activity capable of hydrolyzing 4-nitrophenyl-β-glucoside was observed. Subsequent to increases in l-phenylalanine ammonialyase and 4-coumarate:coenzyme A ligase enzyme activities, cell wall-bound thioglycolic acid-extractable compounds accumulated in elicitor-treated cultures, and these cells exhibited strong staining with phloroglucinol, suggesting the accumulation of wall-bound phenolic compounds.     

PdEPF1 regulates water‐use efficiency and drought tolerance by modulating stomatal density in poplar

Water deficiency is a critical environmental condition that is seriously reducing global plant production. Improved water‐use efficiency (WUE) and drought tolerance are effective strategies to address this problem. In this study, PdEPF1, a member of the EPIDERMAL PATTERNING FACTOR (EPF) family, was isolated from the fast‐growing poplar clone NE‐19 [Populus nigra × (Populus deltoides × Populus nigra)]. Significantly, higher PdEPF1 levels were detected after induction by dehydration and abscisic acid. To explore the biological functions of PdEPF1, transgenic triploid white poplars (Populus tomentosa ‘YiXianCiZhu B385’) overexpressing PdEPF1 were constructed. PdEPF1 overexpression resulted in increased water deficit tolerance and greater WUE. We confirmed that the transgenic lines with greater instantaneous WUE had approximately 30% lower transpiration but equivalent CO₂ assimilation. Lower transpiration was associated with a 28% reduction in abaxial stomatal density. PdEPF1 overexpression not only strongly enhanced WUE, but also greatly improved drought tolerance, as measured by the leaf relative water content and water potential, under limited water conditions. In addition, the growth of these oxPdEPF1 plants was less adversely affected by reduced water availability than plants with a higher stomatal density, indicating that plants with a low stomatal density may be well suited to grow in water‐scarce environments. Taken together, our data suggest that PdEPF1 improves WUE and confers drought tolerance in poplar; thus, it could be used to breed drought‐tolerant plants with increased production under conditions of water deficiency.     

Impact of drought on productivity and water use efficiency in 29 genotypes of Populus deltoides x Populus nigra

We examined the relationships among productivity, water use efficiency (WUE) and drought tolerance in 29 genotypes of Populus x euramericana (Populus deltoides x Populus nigra), and investigated whether some leaf traits could be used as predictors for productivity, WUE and drought tolerance. At Orléans, France, drought was induced on one field plot by withholding water, while a second plot remained irrigated and was used as a control. Recorded variables included stem traits (e.g. biomass) and leaf structural (e.g. leaf area) and functional traits [e.g. intrinsic water use efficiency (Wi) and carbon isotope discrimination (Delta)]. Productivity and Delta displayed large genotypic variability and were not correlated. Delta scaled negatively with Wi and positively with stomatal conductance under moderate drought, suggesting that the diversity for Delta was mainly driven by stomatal conductance. Most of the productive genotypes displayed a low level of drought tolerance (i.e. a large reduction of biomass), while the less productive genotypes presented a large range of drought tolerance. The ability to increase WUE in response to water deficit was necessary but not sufficient to explain the genotypic diversity of drought tolerance.     

Stem growth habit affects leaf morphology and gas exchange traits in soybean

Backgrounds and Aims

The stem growth habit, determinate or indeterminate, of soybean, Glycine max, varieties affects various plant morphological and developmental traits. The objective of this study is to identify the effect of stem growth habit in soybean on the stomatal conductance of single leaves in relation to their leaf morphology in order to better understand the ecological and agronomic significance of this plant trait.

Methods

The stomatal conductance of leaves on the main stem was measured periodically under favourable field conditions to evaluate g_max, defined as the maximum stomatal conductance at full leaf expansion, for four varieties of soybean and their respective determinate or indeterminate near isogenic lines (NILs). Leaf morphological traits including stomatal density, guard cell length and vein density were also measured.

Key Results

The value of g_max ranged from 0·383 to 0·754 mol H₂O m⁻² s⁻¹ across all the genotypes for both years. For the four pairs of varieties, the indeterminate lines exhibited significantly greater g_max, stomatal density, numbers of epidermal cells per unit area and total vein length per unit area than their respective determinate NILs in both years. The guard cell length, leaf mass per area and single leaf size all tended to be greater in the determinate types. The variation of g_max across genotypes and years was well explained by the product of stomatal density and guard cell length (r = 0·86, P < 0·01).

Conclusions

The indeterminate stem growth habit resulted in a greater maximum stomatal conductance for soybean than the determinate habit, and this was attributed to the differences in leaf structure. This raises the further hypothesis that the difference in stem growth habit results in different water use characteristics of soybean plants in the field. Stomatal conductance under favourable conditions can be modified by leaf morphological traits.Key words: Soybean, Glycine max, stem growth habit, stomatal conductance, stomatal density, guard cell length, near isogenic lines     

Impact of iron supply on the kinetics of recovery of photosynthesis in Cd-stressed poplar (Populus glauca)

Background and Aims

Cadmium (Cd) causes Fe-deficiency-like symptoms in plants, and strongly inhibits photosynthesis. To clarify the importance of Cd-induced Fe deficiency in Cd effects on photosynthesis, the recovery processes were studied by supplying excess Fe after the Cd symptoms had developed.

Methods

Fe-citrate at 10 µm or 50 µm was given with or without 10 µm Cd(NO₃)₂ to hydroponically cultured poplars (Populus glauca ‘Kopeczkii’) with characteristic Cd symptoms. Ion, chlorophyll and pigment contents, amount of photosynthetic pigment–protein complexes, chlorophyll fluorescence and carbon assimilation were measured together with the mapping of healing processes by fluorescence imaging.

Key Results

In regenerated leaves, the iron content increased significantly, while the Cd content did not decrease. As a result, the structural (increase in the amount of photosynthetic pigments and pigment–protein complexes, decrease in the F₆₉₀/F₇₄₀ ratio) and functional (elevation of CO₂ fixation activity and ΔF/F_m′) recovery of the photosynthetic machinery was detected. Cd-induced, light-stress-related changes in non-photochemical quenching, activity of the xanthophyll cycle, and the F₄₄₀?/F₅₂₀ ratio were also normalized. Imaging the changes in chlorophyll fluorescence, the recovery started from the parts adjacent to the veins and gradually extended to the interveinal parts. Kinetically, the rate of recovery depended greatly on the extent of the Fe supply, and chlorophyll a/b ratio and ΔF/F_m′ proved to be the most-rapidly reacting parameters.

Conclusions

Iron deficiency is a key factor in Cd-induced inhibition of photosynthesis.Key words: Cadmium, chlorophyll–protein, iron deficiency, poplar, Populus glauca Haines 1906 var. Kopeczkii, fluorescence imaging, chlorophyll fluorescence induction     

Species‐specific microsatellite markers to monitor gene flow between exotic poplars and their natural relatives in eastern North America

Species‐specific microsatellite markers were obtained for the unambiguous recognition of five poplar species of ecological and commercial importance to eastern North America: the native species Populus balsamifera and Populus deltoides, the exotic species Populus maximowiczii, Populus nigra, Populus trichocarpa and their interspecific hybrids. Forty‐four of 71 tested primer pairs amplified simple sequence repeat (SSR) loci for all five taxa. Six of these loci showed non‐overlapping allelic diversity between species, including fixed differences. Together, they were useful to identify unambiguously the five taxa and to validate parental contributions in a group of hybrid progeny. These markers will be invaluable to detect gene flow from plantations of exotic poplar into adjacent stands of native species and between the two potentially hybridizing native species P. balsamifera and P. deltoides.     

Habituation to thaxtomin A in hybrid poplar cell suspensions provides enhanced and durable resistance to inhibitors of cellulose synthesis

Background  

Thaxtomin A (TA), a phytotoxin produced by the phytopathogen Streptomyces scabies, is essential for the development of potato common scab disease. TA inhibits cellulose synthesis but its actual mode of action is unknown. Addition of TA to hybrid poplar (Populus trichocarpa x Populus deltoides) cell suspensions can activate a cellular program leading to cell death. In contrast, it is possible to habituate hybrid poplar cell cultures to grow in the presence of TA levels that would normally induce cell death. The purpose of this study is to characterize TA-habituated cells and the mechanisms that may be involved in enhancing resistance to TA.     

Testing the ‘Hybrid Susceptibility’ and ‘Phenological Sink’ Hypotheses Using the P. balsamifera – P. deltoides Hybrid Zone and Septoria Leaf Spot [Septoria musiva]

Hybrid genotypes that arise between plant species frequently have increased susceptibility to arthropod pests and fungal pathogens. This pattern has been attributed to the breakdown of plant defenses (‘Hybrid susceptibility’ hypothesis) and (or) to extended periods of susceptibility attributed to plant phenologies in zones of species overlap and (or) hybridization (‘phenological sink’ hypothesis). We examined these hypotheses by assessing the susceptibility of parental and hybrid Populus host genotypes to a leaf spot disease caused by the fungal pathogen Septoria musiva. For this purpose, 214 genotypes were obtained from morphologically pure zones of P. balsamifera and P. deltoides, and from an intervening zone of overlap and hybridization on the drainage of the Red Deer River, Alberta, Canada. Genotypes were identified as P. balsamifera, P. deltoides, or hybrid using a suite of 27 species-specific SNP markers. Initially the genetic structure of the hybrid zone was characterized with 27.7% of trees classified as admixed individuals. To test the hybrid susceptibility hypothesis, a subset of 52 genotypes was inoculated with four isolates of S. musiva. Levels of susceptibility were P. balsamifera > F₁ hybrid > P. deltoides. A further 53 genotypes were grown in a common garden to assess the effect of genotype on variation in leaf phenology. Leaf phenology was more variable within the category of hybrid genotypes than within categories of either parental species. Leaf phenology was also more variable for the category of trees originating in the hybrid (P. balsamifera – P. deltoides [hybrid and parental genotypes combined]) zone than in adjacent pure zones of the parental species. The results from the inoculation experiment support the hybrid intermediacy hypothesis. The results from the common garden experiment support the ‘phenological sink’ hypothesis. These findings have greatly increased our understanding of the epidemiology and ecology of fungal pathogens in plant hybrid zones.     

Physiological mechanism for the reduction in soil water in poplar (Populus deltoides) plantations in Dongting Lake wetlands

The use of large-scale tree plantations has provoked increasing concern regarding the negative effects on local environments in different ecosystems. However, the physiological mechanism underlying the reduction in soil water by tree plantations in wetlands is not clear. The aims of this study were to investigate the effects of poplar (Populus deltoides) plantations on soil water content and to elucidate the underlying physiological mechanisms. To this end, we conducted a 1-year fixed-plot investigation of soil water content (SWC), plant photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and water-use efficiency (WUE) of individual leaves of 11- and 5-year-old poplars and of reed (Triarrherca sacchariflora, a native herbaceous plant) in the Dongting Lake wetlands, China. SWC was highest in reed, intermediate in 11-year-old poplar, and lowest in 5-year-old poplar, suggesting that poplar plantations produce a lower soil water content in wetlands. From May to July, Pn was significantly higher in reed than in the two poplar stands, but did not differ between the different-aged poplars. As a whole, Gs and Tr were higher, but WUE was lower, in the poplar stands than in reed during the growing season, indicating that Gs and Tr are the key physiological mechanisms associated with the lower soil water in poplar stands. Relationships among Pn, Gs, and Tr showed positive correlations (P < 0.01) for each type of vegetation. These data suggest that poplar plantations may cause the transformation of wetlands into dry land due to a lower WUE leading to a massive water loss from soil. This, in turn, would have an influence on community composition and ecosystem function after establishment of the plantations.     

Factors Influencing the Tissue Culture and the Agrobacterium tumefaciens-Mediated Transformation of Hybrid Aspen and Poplar Clones

Tissue culture conditions and transformation have been established for both aspen and poplar. The use of previously described culture conditions resulted in shoot tip necrosis in the shoot cultures and necrosis of stem and leaf explants. Shoot tip necrosis could be overcome by buffering the medium with 2-(N-morpholino)ethanesulfonic acid and Ca-gluconate and by growing the shoots below 25°C. Necrosis of the explants was probably due to an accumulation of ammonium in the explants and could be overcome by adapting the NO₃⁻/NH₄⁺ ratio of the media. Stem explants of established shoot cultures of the aspen hybrid Populus alba × P. tremula and of the poplar hybrid Populus trichocarpa × P. deltoides were cocultivated with Agrobacterium strains having chimeric bar and neo genes on their disarmed tDNAs. Transformed aspen shoots were obtained from 30 to 40% of the explants, while transformed poplar shoots were obtained from 10% of the explants. Extracts from the transformed trees contained high phosphinotricin acetyltransferase and neomycin phosphotransferase activities, and the trees contained one to three copies of the chimeric genes. The transformed trees were completely resistant to the commercial preparations of the herbicide phosphinotricin (glufosinate), while control trees were not.     

Genotypic variation in aluminum resistance, cellular aluminum fractions, callose and pectin formation and organic acid accumulation in roots of Populus hybrids

Soil acidity and aluminum (Al) toxicity are major factors limiting crop yield and forest productivity worldwide. Hybrid poplar (Populus spp.) was used as a model to assess genotypic variation in Al resistance and physiological stress responses to Al in a woody tree species. Eight hybrid crosses of P. trichocarpa, P. deltoides and P. nigra were exposed to Al in solution culture. Resistance to Al varied by genotype and hybrid cross, with P. trichocarpa × P. deltoides crosses being most resistant, P. trichocarpa × P. nigra being intermediate and P. deltoides × P. nigra being most sensitive to Al. Total root Al accumulation was not a good indicator of Al resistance/sensitivity. However, the partitioning of Al into apoplastic and symplastic fractions indicated that differences in sensitivity among genotypes were associated with Al uptake into the symplasm. Aluminum treatment increased callose and pectin concentrations of root tips in all genotypes, but more prominently in Al sensitive genotypes/hybrids. In Al sensitive genotypes, higher levels of symplastic Al accumulation correlated with elevated concentrations of citrate, malate, succinate or formate in root tips, whereas organic acid accumulation was not as pronounced in Al resistant genotypes. These findings suggest that exclusion of Al from the symplast is associated with Al resistance. Further screening of Al tolerant poplar genotypes could yield successful candidates to be utilized for sustainable reforestation/reclamation and carbon sequestration projects where soil acidity may limit tree growth.     

Genetic mapping of QTLs affecting tree growth and architecture in Populus: implication for ideotype breeding

 A segregated F₂ progeny derived from two highly divergent poplar species, Populus trichocarpa and P. deltoides, was used to evaluate the genetic basis of canopy structure and function in a clonally replicated plantation. The QTLs of large effect on growth, branch, and leaf traits were identified using the Populus linkage map constructed by 343 molecular markers. Stem height and harvest index appeared to be under the control of few QTLs with major effects, whereas variation in stem basal area, volume, and dry weight might be due to many more QTLs. Branch and leaf traits on sylleptics tended to include more QTLs with major effects than those on proleptics. In the environment where the pedigree was tested, sylleptics were very frequent in the P. trichocarpa parent but rare in the P. deltoides parent. For sylleptic traits for which two or more QTLs were identified, however, increases in the trait values were conditioned not only by the P. trichocarpa alleles, but also by the P. deltoides alleles. Similar findings were found for traits on proleptics that were differently expressed between the two parents. For both sylleptic and proleptic branch types, dominance (ranging from partial to over) was observed. The QTLs on specific linkage groups were found to be responsible for relationships between stem growth and its developmental components. Similar QTL clustering was also observed for morphological or developmental integration in poplar, i.e., traits with similar developmental origins are more strongly correlated with one another than traits with different developmental origins. The implications of these molecular genetic results for ideotype breeding of poplars are discussed. Received: 15 July 1997/Accepted: 19 August 1997     

Genomic regions involved in productivity of two interspecific poplar families in Europe. 1. Stem height, circumference and volume

Interspecific hybrids of Populus species are known for their superior growth. In this study, we examined the effect of the genetic background and contrasting environmental conditions on growth and searched for quantitative trait loci (QTL) affecting growth traits. To this end, two hybrid poplar families resulting from controlled crosses, Populus deltoides ‘S9-2’ × P. nigra ‘Ghoy’ (D × N, 180 F₁) and P. deltoides ‘S9-2’ × P. trichocarpa ‘V24’ (D × T, 182 F₁), were grown at two contrasting sites, Northern Italy and Central France. At the end of the second growing season, tree dimensions (stem height, circumference, and volume) were assessed. The performances of both families significantly differed within and between sites. Tree volume was significantly larger at the Italian site as compared to the French site. Genotype by environment interactions were significant but low for both families and for all growth traits. Tight correlations among the individual growth traits indicated that there may be a common genetic mechanism with pleiotropic effects on these growth traits. In line with previous studies, linkage groups I, VII, IX, X, XVI, XVII, and XIX appeared to have genomic regions with the largest effects on growth traits. This study revealed that (1) both families have high potential for selection of superior poplar hybrids due to the pronounced heterosis (hybrid vigor) and the large genetic variability in terms of growth and (2) the choice of site is crucial for poplar cultivation. Dillen and Storme contributed equally to the work. An erratum to this article can be found at     

Ribosomal RNA genes structure in somePopulus spp. (Salicaceae) and their hybrids

The tandemly repeated multigene families encoding 18S and 25S rRNAs were studied at the restriction enzyme level inPopulus alba L.,Populus deltoides Bartr. exMarsh.,Populus trichocarpa Torr. & Gray and in the hybrids between the last two mentioned species. The analysis of single and double digestion with EcoRI, BamHI, XbaI, and SstI endonucleases showed the presence of single repetitive unit types of 12.25 and 11.75kb inP. alba andP. trichocarpa, respectively.P. deltoides showed two rDNA gene types having the same length (12.25Kb) but different nucleotide sequence in the IGS. The rDNAs genes ofP. deltoides andP. triochocarpa are inherited codominantly in their hybrids.     

Relationship between genotype and soil environment during colonization of poplar roots by mycorrhizal and endophytic fungi

Poplars are among the few tree genera that can develop both ectomycorrhizal (ECM) and arbuscular (AM) associations; however, variable ratios of ECM/AM in dual mycorrhizal colonizations were observed in the roots of a variety of poplar species and hybrids. The objective of our study was to analyze the effect of internal and external factors on growth and dual AM and ECM colonization of poplar roots in three 12–15-year-old common gardens in Poland. We also analyzed the abundance of nonmycorrhizal fungal endophytes in the poplar roots. The Populus clones comprised black poplars (Populus deltoides and P. deltoides × Populus nigra), balsam poplars (Populus maximowiczii × Populus trichocarpa), and a hybrid of black and balsam poplars (P. deltoides × P. trichocarpa). Of the three sites that we studied, one was located in the vicinity of a copper smelter, where soil was contaminated with copper and lead. Poplar root tip abundance, mycorrhizal colonization, and soil fungi biomass were lower at this heavily polluted site. The total mycorrhizal colonization and the ratio of ECM and AM colonization differed among the study sites and according to soil depth. The influence of Populus genotype was significantly pronounced only within the individual study sites. The contribution of nonmycorrhizal fungal endophytes differed among the poplar clones and was higher at the polluted site than at the sites free of pollution. Our results indicate that poplar fine root abundance and AM and ECM symbiosis are influenced by environmental conditions. Further studies of different site conditions are required to characterize the utility of poplars for purposes such as the phytoremediation of polluted sites.     

Potentials and limitations of the cross-species transfer of nuclear microsatellite marker in six species belonging to three sections of the genus Populus L.

The genus Populus is classified into six different sections, and depending on the declaration of hybrids, the number of species varies between 22 and 85. Species within one section, and sometimes between sections, are crossable to each other, resulting in many naturally but also artificially produced hybrids. Morphological attributes for a clone characterisation are often difficult to evaluate when different poplar species or even hybrids are crossed; thus, molecular markers are needed to characterise the different species. Taking advantage of the large microsatellite resource developed for Populus trichocarpa, however, amplification of these microsatellite markers in other Populus species either often fails, or in the case of amplification, unrelated genomic regions are amplified. To meet this obvious problem of the species transferability of microsatellite markers, in total, 305 microsatellite loci, mainly from P. trichocarpa but also few from Populus tremuloides and Populus nigra, were tested for their transferability to diverse genotypes of six species belonging to three sections of the genus Populus. Ultimately, 209 microsatellite loci could be amplified with varying sizes in the different species. The PCR products of selected loci were separated in a polyacrylamide gel and sequenced to assure that the expected loci were derived from the database genome of P. trichocarpa. The present results constitute a large study for microsatellite transferability for Populus species. The documented microsatellite loci can be applied to species-, hybrid- and clone-specific diagnostic approaches or as universal markers for comprehensive ecological studies.