Clonality Testing Research Articles

Clonality testing of cutaneous lymphoid infiltrates: practicalities, pitfalls and potential uses

PCR is the method of choice for assessing antigen receptor gene rearrangement in suspect cutaneous infiltrates. It is a powerful and robust technique, but not without certain limitations and pitfalls. Of particular importance in the analysis of lymphoproliferations in the skin are the quality of DNA obtainable, an understanding of how primer choice may influence sensitivity and issues surrounding pseudoclonality. When interpreting results, cognisance must also be taken of the well-documented fact that monoclonal T-cell receptor and immunoglobulin gene rearrangements are not infrequently encountered in benign reactive cutaneous disorders. We discuss these issues in detail herein, and outline the situations in which we believe clonality testing may add value to assessing the biological nature of a cutaneous lymphoid infiltrate. Lastly, we emphasize the importance of interpreting any results derived from PCR assays in the context of the clinical, histological and immunophenotypic findings.

Impacts of hypoxia on the features and chemoresistance of cancer stem cells in Hep-2 cells and underlying mechanism

To investigate the effects of hypoxia on the features and chemoresistance of cancer stem cells in Hep-2 cells and underlying mechanism. The shRNA interference recombinant plasmid targeting HIF-1α was synthesized and transfected into Hep-2 cells. The HIF-1α knockdown Hep-2 cells were established after clonal selection and the expression of HIF-1α was measured. The cellular features including proliferation, clonal formation, cell cycle, apoptosis and CD133 phenotype were measured in Hep-2 cells cultured under hypoxic condition in vitro. CD133+ cells were sorted from Hep-2 cells with flow cytometry. Clonal formation test and cisplatin treatment were carried out, and the expressions of related genes (Oct-4, suvivin and p53) in CD133+ cells were measured. HIF-1α knockdown Hep-2 cells was successfully established, as evidenced by the reduced mRNA and protein expressions of HIF-1α. The Hep-2 cells cultured under hypoxic microenvironment showed higher proliferation and clonal formation activity, cell cycle arrest in G0/G1, lower apoptosis, up-regulated CD133, however the effects of hypoxia reduced in HIF-1α knockdown Hep-2 cells. CD133+ cells were successfully sorted from Hep-2 cells, and the CD133+ cells showed increased clonal formation activity and cisplatin treatment resistance in hypoxia. Also the effects of hypoxia on CD133+ cells decreased with HIF-1α knockdown, showing down-regulated Oct-4 and survivin and up-regulated p53. Hypoixa can induce the features of cancer stem cells in Hep-2 cells and increase proliferation, differentiation and chemoresistant ability of CD133+ cells, which might be correlated with the changes in expressions of HIF-1α and related genes regulated by HIF-1α.

Clonality testing: teamwork by pathologist and molecular biologist

Clonality testing is a mature technique that is a reliable toolin the routine diagnostics of lymphoproliferations [1].Almost all lymphomas are clonal [2, 3], and the majority ofreactivelymphoproliferationsarepolyclonal[4].Althoughthestandard method, using the full program of antigen receptors,is now available for almost a decade [5], there is still greatneed for teaching and exchange of experience. This is due tothe fundamental different principles that form the basis ofclonality testing as a molecular test, compared to other mo-lecular tests in pathology. Most molecular tests deal with apathological change in the DNA of a tumor. Examples are ofcourse mutations and amplifications in oncogenes, transloca-tions resulting in abnormal gene activity or even novel pro-teins. In all these situations, there are important quality issuesand external quality assurance is mandatory [6–8]. In thesetests the interaction of pathologists and molecular biologistsshouldnotbeunderestimated,but it isnot incomparisonwithclonality testing. The main reason is that clonality testing isnotdealingwithpathologicalbutratherphysiologicalchangesin the DNA.It is well known that every mature B and T cell has aunique set of rearranged antigen receptor genes, unique inthe sense that after a B or Tcell is fully differentiated, it willstart to proliferate in case the proper antigen is presentresulting in small clones. The usefulness of clonality testinglies in the fact that reactive lesions have proliferations ofmany different B and/or Tcells, whereas a malignant lesionconsists of the proliferation of a single B or T cell. It istherefore clear that in principle, a sensitive clonality test, inwhich rearranged antigen receptors are amplified, will detectevery B and T cell, physiological or pathological. A sharpcontrast with a test which aims at the detection of a patho-logical change: in case a mutation is found, it implies thatthe test is positive. In case a clonal B or Tcell population isfound, it implies only that there is indeed a clonal popula-tion. This result really has to be interpreted in the fullpathological context of the lesion. And this can only bedone by bringing the pathology (morphology and immuno-phenotype) and molecular biology together.This special issue on clonality testing in Hematopathologyassemblesaseriesofarticlesthatdealwithproblematicissuesin applying this test and thus really is a teaching issue. In thiseditorialsomeoftheseissuesareoutlinedstressingtheimpor-tance of the interaction of the molecular biologists and thepathologists, each with her or his own expertise.In general, a pathologist orders clonality testing in case alesion is not clearly malignant or reactive. Some patholo-gists order clonality testing to confirm their diagnosis of alymphoma. In such cases one may expect a relativelystraightforward result of a clonality test: a dominant clonalresult with a small background polyclonal pattern. Althoughthis is helpful for building up experience, it is likely notcost-effective. In the more problematic cases, there can bemultiple clones and one of these may be malignant. Onetherefore needs to combine all data to come to a conclusion.Here we discuss some situations in which the interactionis critical.– The composition of the tissue tested is important forinterpretation of the clonality results. Normal germinalcenters consist of one or a few B cells that are in the

Production of cuttings in response to stock plant temperature in the subtropical eucalypts, Corymbia citriodora and Eucalyptus dunnii

Propagation of subtropical eucalypts is often limited by low production of rooted cuttings in winter. This study tested whether changing the temperature of Corymbia citriodora and Eucalyptus dunnii stock plants from 28/23°C (day/night) to 18/13°C, 23/18°C or 33/28°C affected the production of cuttings by stock plants, the concentrations of Ca and other nutrients in cuttings, and the subsequent percentages of cuttings that formed roots. Optimal temperatures for shoot production were 33/28°C and 28/23°C, with lower temperatures reducing the number of harvested cuttings. Stock plant temperature regulated production of rooted cuttings, firstly by controlling shoot production and, secondly, by affecting the ensuing rooting percentage. Shoot production was the primary factor regulating rooted cutting production by C. citriodora, but both shoot production and root production were key determinants of rooted cutting production in E. dunnii. Effects of lower stock plant temperatures on rooting were not the result of reduced Ca concentration, but consistent relationships were found between adventitious root formation and B concentration. Average rooting percentages were low (1–15% for C. citriodora and 2–22% for E. dunnii) but rooted cutting production per stock plant (e.g. 25 for C. citriodora and 52 for E. dunnii over 14 weeks at 33/28°C) was sufficient to establish clonal field tests for plantation forestry.

Genetic parameters and performance stability of white spruce somatic seedlings in clonal tests

The commercial use of white spruce varieties produced by somatic embryogenesis (SE) permits increased forest productivity compared to other reproductive technologies. However, the use of SE in clonal forestry requires an accurate assessment of genetic parameters and the performance stability of clones in plantations. For these reasons, two clonal tests were established of 52 white spruce somatic clones. In each clonal tests, we measured survival, bud dormancy, stem form, growth and branching characteristics of clones 4years after outplanting. There was a large variability among clones for characteristics related to growth and branching. At this juvenile stage, the clonal heritability estimates for all characteristics remained low. Of all the characteristics studied, height had the highest heritability. The selection of the top 20 clones (38% of the clones) provided a genotypic gain in height of about 4% for the two planting sites, which is reasonable for such a low selection intensity. High genotypic correlations were observed between growth and branching characteristics. Although a significant site effect was observed for most characteristics, the genotype×site (G×E) interaction was low and consequently the correlation between the two sites for the same characteristic was high. The performance stability of the somatic clones at both sites indicates that opportunities exist for selection of clones that adapt and perform well over different ecological regions, permitting a tangible increase in forest productivity.

Testing clonality of three and more tumors using their loss of heterozygosity profiles

Cancer patients often develop multiple malignancies that may be either metastatic spread of a previous cancer (clonal tumors) or new primary cancers (independent tumors). If diagnosis cannot be easily made on the basis of the pathology review, the patterns of somatic mutations in the tumors can be compared. Previously we have developed statistical methods for testing clonality of two tumors using their loss of heterozygosity (LOH) profiles at several candidate markers. These methods can be applied to all possible pairs of tumors when multiple tumors are analyzed, but this strategy can lead to inconsistent results and loss of statistical power. In this work we will extend clonality tests to three and more malignancies from the same patient. A non-parametric test can be performed using any possible subset of tumors, with the subsequent adjustment for multiple testing. A parametric likelihood model is developed for 3 or 4 tumors, and it can be used to estimate the phylogenetic tree of tumors. The proposed tests are more powerful than combination of all possible pairwise tests.

A practical approach to diagnostic Ig/TCR clonality evaluation in clinical pathology

The BIOMED-2 group developed and approved a set of multiplex Ig and T cell receptor PCR primers and successfully applied these to different well-defined WHO lymphoma entities with unprecedented high frequencies of malignant cases showing clonality. This approach has now become a worldwide standard of clonality testing in lymphoproliferations. While the clonality testing and assessment by GeneScan and/or heteroduplex analysis has become relatively easy to perform, the evaluation of the obtained gene rearrangement patterns can be difficult. In this review, we will address specific aspects of clonality testing, concerning both the practical phase as the evaluation of the obtained gene rearrangement patterns, which will help to overcome problems that can be encountered in the routine diagnostic setting.

Multiple clonal Ig/TCR products: implications for interpretation of clonality findings

Clonality assessment via analysis of immunoglobulin (Ig) and T cell receptor (TCR) gene rearrangements has become an important and valuable adjunct in the diagnostic process of suspect lymphoproliferations. One of the major issues in correct interpretation of clonality testing results appears to be the occurrence of multiple clonal PCR products. The presence of two different PCR products could reflect biclonality but can often more easily be attributed to the occurrence of biallelic rearrangements in a single clone. Furthermore, due to the specific configuration of the IGK and TCRB loci, multiple rearrangements can occur on one allele, resulting in the possibility that up to four PCR products could be compatible with a single clone. Finally, >2 clonal Ig/TCR products (>4 for IGK and TCRB) could reflect biclonality, oligoclonality, or even pseudoclonality. It is not always easy to distinguish between those options, but the use of duplicates will be helpful to determine reproducibility and relevance of the detected clonal PCR products. In conclusion, straightforward interpretation of clonality testing results can be hampered by the occurrence of multiple clonal products. Only careful consideration of immunobiological and technical explanations will prevent incorrect interpretation in such cases.

Threshold selection for rust resistance in hybrid poplar: Population response to mass selection

Abstract Eleven Populus × generosa populations were developed in the Pacific Northwest by annual controlled hybridization of P. deltoides and P. trichocarpa between 1991 and 2001. Mass selection for Melampsora leaf rust resistance was observed in the field as a threshold character in identifying seedling phenotypes for clonally replicated evaluation. The effectiveness of the approach was assessed for each annual population by comparing the distribution of phenotypes in unselected seedling populations with the distribution of selected genotypes in the clonal field tests established in successive years and evaluated at the approximate same level of disease severity using two selection thresholds corresponding to chlorotic and healthy tissue. Bi-directional selection was used as an initial check on the efficacy of the procedure and resulted in a wide separation in liability between the positive (0.06 threshold units (T.U.)) and negative (−2.45 T.U.) selection groups when tested as clones. The other 10 seedling populations that were subjected solely to directional selection exhibited a mean increase in incidence above the first selection threshold at the clonal stage (47 versus 81%) that was accompanied by an improvement in population liability (−0.06 versus 0.50 T.U.) and a reduction in population standard deviation (0.83 versus 0.54 T.U.). The change in liability was strongly related by polynomial regression to selection intensity and a grouping of populations based on infection-season precipitation (r2=0.98). The mean liability of four of the 10 seedling populations observed during years of high infection-season rainfall was six-fold lower than the mean liability of those populations observed during the other six years of lower infection-season rainfall (−0.12 T.U. versus −0.02 T.U., respectively), indicating that populations undergoing evaluation during years of heavy precipitation experienced more intense rust exposure. Moreover, quadratic functions showed that populations undergoing rust evaluation during years of high rainfall were more responsive to increases in selection intensity above the vertex of the function (i.e. 13.20 versus 3.43 T.U.). Realized heritability averaged 0.63 for all ten populations subjected solely to directional selection.

The EuroClonality website: information, education and support on clonality testing

Clonality assessment is an established tool in the diagnosis of malignant lymphoma; however, the evaluation of immunoglobulin/T-cell receptor (Ig/TCR) gene rearrangement profiles is not always straightforward. Therefore, the EuroClonality group supports and advises diagnostic laboratories in their clonality assessments on samples from patients suspicious for lymphoma, who are seen in the routine diagnostic setting. The support for clonality assessment is provided via the EuroClonality website: http://www.euroclonality.org. The features and procedures of the website are presented in this paper.

Validation of the REMA Score for Predicting Mast Cell Clonality and Systemic Mastocytosis in Patients with Systemic Mast Cell Activation Symptoms

Background: A variable percentage of patients with systemic mast cell (MC) activation symptoms meet criteria for systemic mastocytosis (SM). We prospectively evaluated the clinical utility of the REMA score versus serum baseline tryptase (sBt) levels for predicting MC clonality and SM in 158 patients with systemic MC activation symptoms in the absence of mastocytosis in the skin (MIS). Methods: World Health Organization criteria for SM were applied in all cases. MC clonality was defined as the presence of KIT-mutated MC or by a clonal HUMARA test. The REMA score consisted of the assignment of positive or negative points as follows: male (+1), female (–1), sBt <15 µg/l (–1) or >25 µg/l (+2), presence (–2) or absence (+1) of pruritus, hives or angioedema and presence (+3) of presyncope or syncope. Efficiency of the REMA score for predicting MC clonality and SM was assessed by receiver operating characteristic (ROC) curve analyses and compared to those obtained by means of sBt levels alone. Results: Molecular studies revealed the presence of clonal MC in 68/80 SM cases and in 11/78 patients who did not meet the criteria for SM. ROC curve analyses confirmed the greater sensitivity and a similar specificity of the REMA score versus sBt levels (84 vs. 59% and 74 vs. 70% for MC clonality and 87 vs. 62% and 73 vs. 71% for SM, respectively). Conclusions: Our results confirm the clinical utility of the REMA score to predict MC clonality and SM in patients suffering from systemic MC activation symptoms without MIS.

Somatic embryogenesis for mass propagation of elite Spruce families: effect of storage time on somatic embryogenesis initiation

Background Somatic embryogenesis (SE) is the only clonal propagation method that has potential for large scale production of elite conifer plants from the breeding programs. Methods that support bioreactor-based methods for SE propagation are developed [1,2]. Samples of somatic embryos can be stored indefinitely under liquid nitrogen for future plant production. Somatic embryo cultures are also studied as model systems for conifer embryo development to address fundamental research questions, or used as material for genetic transformation to study gene function in conifers. In addition to utilizing SE for masspropagation of known elite clones previously tested in field tests, the SE technology offers an opportunity to directly capture and increase the value of small samples of elite seeds from the breeding programs. Furthermore, by direct masspropagation of families through SE, the value of the elite seed is increased; however without the cost of clonal testing. This is arguably an alternative approach to the traditional approach of only utilizing clonal field-tested material for SE masspropagation [3].The aim of this project was to investigate the effect from seed storage time on the rate of somatic embryo initiation for the purpose of optimizing the use for SE over time of small valuable seed samples. This was done by isolating ZE from seeds of Norway spruce that had been stored for various times, and were collected from different parts of Sweden. Material and methods Plant material Nineteen batches of Norway spruce (Picea abies) seeds from commercial seed orchards in southern, middle and northern parts of Sweden were provided by the forest companies supporting the project.

Unequal clonal deployment improves genetic gains at constant diversity levels for clonal forestry

Maximizing genetic gain at an acceptable diversity level is an ideal outcome of selection and deployment. Based on this criterion, this study investigated the efficiency of unequal clonal deployment strategies for clonal forestry and compared them with truncation selection and equal deployment (truncation deployment). Two unequal deployment strategies were considered: (1) deploying the clones in linear relationship to their genetic values (linear deployment) and (2) optimizing genetic gain at a given diversity level using an algorithm (optimal deployment). All strategies were applied to candidate clone sets constructed from two clonal tests of spruces with one having a complex relationship of clone, half-sib, and full-sib and the other having a simpler relationship of clone and half-sib. At a constant diversity level, substantially more expected gains were obtained by the unequal deployment strategies than by truncation deployment. Optimal deployment was at least equal to linear deployment. Optimal deployment’s superiority was more evident when the candidate clones in the set were more closely related, having less available diversity for selection, and/or when higher diversity levels were demanded, but diminished when the candidate clones were unrelated or equally related. We recommend using optimal deployment for clonal forestry, although in some cases, linear deployment might be a near-optimal alternative. As current clonal tests are based on advanced breeding cycles, candidate clones for selection are inevitably related to some degree, so optimal deployment is likely to become preferred.

Effects of propagule type on genetic parameters of wood density and growth in a loblolly pine progeny test at ages 10 and 11 years

Nine full-sib families of loblolly pine (Pinus taeda L.) were produced by a 3 × 3 factorial mating design. Rooted cuttings and seedlings of full-sib families were tested together in two field locations. Twelve-millimeter wood increment cores were collected from 10- and 11-year-old test trees. On each of the two sites, there were six blocks and a split-plot design, with propagule type as the whole plot and family as the sub-plot. In addition to the collection of wood samples, height and diameter of 1,600 trees were measured. No significant differences were found between cuttings and seedlings for wood density and growth traits. Significant family variation was found for growth and wood density. Genetic parameters estimated for wood density and growth traits using seedlings and rooted cuttings showed that individual-tree and family heritability estimates from rooted cuttings were similar to or higher than those from seedlings for all traits. Half-sib breeding values for parents were highly correlated based on seedling and rooted cutting estimates for height (0.95) and wood density (0.99) but not for diameter (0.56), which suggests that wood density and height breeding value estimates from rooted cuttings in clonal progeny tests can be estimated by traditional seedling tests, but not for tree diameter.

Patterns of genetic parameters for height in field genetic tests of Picea abies and Pinus sylvestris in Sweden

We reviewed the genetic parameter estimates carried out from 1992 to 2006 for height increment in genetic tests of Norway spruce and Scots pine, to describe patterns of genetic variation, heritability, and genetic correlations. The material included seedling and clonal tests in Sweden, aged between 5 and 20 years. Multiple regression was used to explore relationships between parameter values and test environments. Results showed moderate narrow-sense heritabilities (\( {\hat{h}^2} \): mean =0.29 in Norway spruce; mean =0.23 in Scots pine) that decreased with test site latitude for both species. In Norway spruce, \( {\hat{h}^2} \) increased with better growth and decreased with tree age, while for Scots pine, \( {\hat{h}^2} \) increased with tree age and southward transfer. The additive genetic coefficient of variation (Open image in new window; mean 15%), in Norway spruce, decreased with growth as well as site latitude. Open image in new window in Scots pine (mean =8.5%) increased with southward transfer and more southerly test latitude. Additive and genotypic within-site genetic age-age correlations in Norway spruce were high, with mean rA and rG of 0.92 and 0.85, respectively. Corresponding across-sites estimates were on average lower. Genetic parameters were better expressed on favorable sites, at younger ages in Norway spruce and at older ages in Scots pine. The results imply that gain calculations should be based on different parameters in the two species. For maximizing genetic gain in the Swedish breeding program, testing times could be shorter for Norway spruce than for Scots pine. The investigation showed a large variation in parameter estimates from different field experiments, highlighting the importance of testing over multiple sites.

Negative images of crystalline immunoglobulin in crystal storing histiocytosis: A potential cytologic mimic of mycobacteria in smears

Two cases are described of crystal storing histiocytosis (CSH) associated with extranodal marginal zone lymphoma, presenting as lung and subcutaneous masses respectively. Fine-needle aspiration of subcutis and smears prepared from the resected lung masses showed negative images. Cytology slides of both cases were reviewed to identify cytomorphological features for the differential diagnosis between immunoglobulin crystals and mycobacteria. The crystals in CSH consist of straight and needle shaped rods with pointed or angular edges and are more variable in thickness than the uniformly thin mycobacteria. Mycobacteria show a haphazard distribution, whereas crystals are frequently present in parallel arrays. Small lymphoid or plasma cells are identified in the background of CSH, whereas a necrotic and inflammatory background is seen in mycobacteriosis. Additional samples for culture in the case of mycobacteriosis, or flow cytometry and molecular clonality testing in the case of CSH can provide critical data for a definitive diagnosis.

Long-term cryopreservation of Greek fir embryogenic cell lines: Recovery, maturation and genetic fidelity

In coniferous species, including Greek fir ( Abies cephalonica Loud), the involvement of somatic embryo plants in breeding and reforestation programs is dependent on the success of long-term cryostorage of embryogenic cultures during clonal field testing. In the present study on Greek fir, we assayed the recovery, morphological characteristics and genetic fidelity of embryogenic cell lines 6 and 8 during proliferation and maturation after long-term cryostorage. Our results indicate successful recovery of both cell lines after 6 years in cryostorage. In the maturation phase, both cell lines were capable of producing somatic embryos although some differences were detected among experiments. However, these changes were more dependent on the differences in the components of the maturation media or in the experimental set-up than on the long-term cryostorage. During both proliferation and maturation phases, the morphological fidelity of the embryogenic cultures as well as of the somatic embryos were alike before and after cryopreservation. The genetic fidelity of the cryopreserved cell line 6 that was assayed by random amplified polymorphic DNA (i.e. RAPD) markers demonstrated some changes in the RAPD profiles. The results indicate possible genetic aberrations caused by long-term cryopreservation or somaclonal variation during the proliferation stage. However, in spite of these changes the embryogenic cultures did not lose their proliferation or maturation abilities.

Histopathological and Immunohistochemical Evaluation of 53 Cases of Feline Lymphoplasmacytic Enteritis and Low-Grade Alimentary Lymphoma

Low-grade alimentary lymphoma (LGAL) is a recently described entity displaying many microscopical features similar to lymphoplasmacytic enteritis (LPE). The aim of this study was to review the histopathological and immunohistochemical features of LPE and LGAL to determine if specific features are useful in distinguishing between these disorders. Fifty-three cases of LPE (n=24) or LGAL (n=29) were recruited retrospectively and prospectively. Of the 24 cases of LPE, 12 were mild, seven were moderate and five were marked in severity. The ileum and jejunum were the most common sites affected for both LGAL and LPE (70-90% of cases). Involvement of the stomach was more common with LPE (29%) than LGAL (7%) (P<0.0001). Twelve cases of LGAL (41%) had evidence of concurrent LPE. Microscopical features significantly associated with LGAL were epitheliotropism, involvement of the muscularis propria and/or serosa, more severe infiltration and more severe changes to the villus and crypt architecture. Plasma cell infiltration within the mucosa, conversely, was a feature of LPE. Twenty-eight of the 29 cases of LGAL were of T-cell phenotype. While many LGAL and most LPE cases had a mixed infiltrate of T and B lymphocytes, LGAL cases had a clear predominance of the T-cell phenotype. Expression of class II molecules of the major histocompatibility complex by enterocytes did not differentiate between LGAL and LPE. In eight of 12 cases of moderate-marked LPE there was disparity in diagnosis by two pathologists regarding differentiation from LGAL, requiring assessment by a third pathologist to reach a consensus diagnosis. This demonstrates the inherent difficulty in differentiating LPE from LGAL on the basis of microscopical and immunohistochemical features alone. Other diagnostic tools such as clonality testing may assist in the definitive diagnosis of such cases.

Correspondence between performance of Eucalyptus spp trees selected from family and clonal tests

We examined the correspondence in performance between trees selected from a family test and their respective clones from a clonal test of Eucalyptus. Full-sib families were obtained from controlled pollination among individuals of Eucalyptus grandis and between E. grandis and E. urophylla. The hybridizations did not follow a factorial scheme. The family tests were carried out at three locations in Eunápolis and Itabela counties, in Bahia, Brazil, in 2003. Four hundred and ninety-seven high-performance trees were selected, by the individual BLUP procedure, in the family tests at two years of age, based on wood volume. The clones from these trees and 14 checks were evaluated in clonal tests carried out in the same region in 2006. The wood volume of the clones was evaluated at two years of age. Trait correlation between the trees selected from the family and clonal tests was low. The estimate of the coincidence between the best trees and the best clones using an average of the different intensities of selection was only 27%. These results demonstrate that the selection of trees in the family test should not be too drastic; otherwise the chance plus clones may be overlooked.

Viabilidade de aplicação da seleção precoce em testes clonais de &lt;i&gt;Eucalyptus&lt;/i&gt; spp

Com o objetivo de avaliar a eficiência da seleção precoce em Eucalyptus spp. foram usados dados de dois testes clonais avaliados quanto ao crescimento em altura (ALT), diâmetro à altura do peito (DAP) e volume individual de madeira (VOL) aos 25, 50 e 72 meses de idade. O delineamento experimental nos dois testes clonais foi o de blocos casualizados, com trinta tratamentos (clones), seis repetições, sendo um deles com seis e o outro com dez plantas em linha por parcela, no espaçamento de 3,0 m x 3,0 m. Foi feita a análise de variância para cada caracter e idade. Foram obtidas as estimativas de coeficiente de determinação genotípico e de correlações genotípicas entre os caracteres nas idades juvenis e na idade de rotação. Para verificar a viabilidade da aplicação da seleção precoce, foi simulada a seleção de 30% dos clones nas idades juvenis e na idade de rotação para cada um dos caracteres e idades avaliadas, obtendo-se as estimativas de ganhos genéticos com a seleção direta e indireta. Houve diferenças significativas entre os clones avaliados nos dois experimentos para todos os caracteres e idades. Com base nos resultados obtidos, é possível efetuar a seleção precoce aos 2 anos de idade sobre o caracter DAP em testes clonais de eucalipto.