A. M. Aguiar

Comparison Between Open Pollinated Progenies and Hybrids Performance in Eucalyptus grandis and Eucalyptus urophylla

Summary The cellulose industry in Brazil uses, mainly, hybrids between Eucalyptus grandis × E. urophylla. Not only the volume but also the wood density has great influence in the cellulose productivity, therefore a selection for both characteristics should be done as an alternative to increase the improvement program efficiency. The present work has been carried out with the objective of comparison between Open Pollinated progenies (OP) and hybrids performance in E. grandis and E. urophylla. To do so, 15 OP progenies of E. grandis, 15 OP progenies of E. urophylla, and 15 hybrids between E. grandis × E. urophylla, plus four controls were evaluated. The experiment was carried out from October to November 2001, in three sites, Aracruz and São Mateus, in the Espírito Santo State, and Caravelas, Bahia State, Brazil, in a 14 × 14 lattice design, involving the 49 treatments mentioned plus other progenies not considered in this article, with single tree plots and 40 replicates. Two years later the circumference at breast height (CBH) and the basic wood density (BWD) were evaluated. The hybrids performance for CBH was higher, an average, 38,7% than the OP progenies for both species. Part of the heterosis in relation to parental means could be attributed to the inbreeding depression due to selfing that occurred in the OP progenies and the dominance controlling this character. For the BWD the hybrids performance was the same of the OP progenies. Since there was divergence between the parents, it can be inferred that dominance has no importance for this trait. The negative correlation between the CBH and the BWD could impair the simultaneous selection for both traits, depending on the wood basic density range used by the industry.

Determinação das deformações residuais longitudinais decorrentes das tensões de crescimento em Eucalyptus spp.

This study was carried out to determine the longitudinal residual strain (DRL) resulting from growth stress in standing trees, in different clones of Eucalyptus spp. Twelve clones of 9-year-Eucalyptus spp. were selected by basal area (G). From each clone, 12 trees of each clone were selected, and the following variables were measured: basic density (DB), bark thickness (EC), diameter at breast height (DBH) and total height (H). The measurements of DRL were performed in living trees, using an extensometer(Growth Strain Gauge), according to the CIRAD-Foret method. Readings were taken at four locations around the tree trunk. In relation to the levels of DRL, the results obtained in the study indicated that the clones showed large variations among themselves, presenting values considered high ones when compared with the results found in literature. The clone 8 was distinguished by having the lowest levels of strain and was considered as a suitable and recommended material for the production of solid wood and for breeding programs. On

Development of near infrared calibrations for physical and mechanical properties of eucalypt pulps of mill-line origin

Near infrared (NIR) spectroscopy has been used in several studies to predict the physical and mechanical properties of pulp hand-sheets. In most of these studies, wood samples were pulped in a laboratory under different regimes and/or refined to introduce variability into the data set. This study investigates the potential of NIR spectroscopy to create calibrations for eucalyptus pulp properties of mill-line origin. Seven mechanical properties (air resistance, compressibility, drainability, hygro-expansivity, stretch, tensile index and tensile stiffness) and three physical properties (bulk density, specific volume, and surface area) were investigated. Coefficients of deter mination (R2) for all 10 properties were poor. The R2C value exceeded 0.70 for only one property (tensile index), while the R2CV values exceeded 0.40 for only two properties (drainability and surface area). Ratios of performance to deviation were equally poor, ranging from 0.87 for bulk density to 1.28 for drainability. These statistics indicate that none of the calibrations could be used to accurately predict the properties of unknown samples. The poor performance of the calibrations is likely due to the low variability of our dataset, which is generally inherent in samples of mill-line origin.

Effect of Different Progeny Test Strategies in the Performance of Eucalypt Clones

Abstract The objective of the present study was to investigate whether the performance of an individual in clonal testing was affected by the location of the initial selection. The study also evaluated the effect of mass selection and BLUP (Best Linear Unbiased Prediction) on the performance of individuals in the progeny test and the clonal test. In the progeny test, 62 half-sib E. grandis families, 68 half-sib E. urophylla families and 62 full-sib families between E. grandis and E. urophylla, plus four checks were evaluated totaling 196 treatments. The experiments were carried out at three sites: Aracruz and São Mateus, in Espírito Santo State and Caravelas, Bahia State, Brazil. The 1000 best individuals were classified by mass selection and BLUP. In the clonal tests 257 clones were evaluated in two locations: Aracruz and Caravelas. In both the progeny test and the clonal test, two years after planting, the circumference at breast height and basic wood density were measured and the sum of standardized variables (Z) was estimated for simultaneous selection of both characteristics. The results indicated that the origin of the individual in a progeny test had a small effect on the performance of the clone when evaluated in other environments; the estimates of realized heritability and the linear regression coefficient were small in all the selection strategies. Thus, the correlation between the performance of trees selected in progeny tests and their respective clones in the clonal test was small.

Independent and Joint-GWAS for growth traits in Eucalyptus by assembling genome-wide data for 3373 individuals across four breeding populations

Genome-wide association studies (GWAS) in plants typically suffer from limited statistical power. An alternative to the logistical and cost challenge of increasing sample sizes is to gain power by meta-analysis using information from independent studies. We carried out GWAS for growth traits with six single-marker models and regional heritability mapping (RHM) in four Eucalyptus breeding populations independently and by Joint-GWAS, using gene and segment-based models, with data for 3373 individuals genotyped with a communal EUChip60KSNP platform. While single-single nucleotide polymorphism (SNP) GWAS hardly detected significant associations at high-stringency in each population, gene-based Joint-GWAS revealed nine genes significantly associated with tree height. Associations detected using single-SNP GWAS, RHM and Joint-GWAS set-based models explained on average 3-20% of the phenotypic variance. Whole-genome regression, conversely, captured 64-89% of the pedigree-based heritability in all populations. Several associations independently detected for the same SNPs in different populations provided unprecedented GWAS validation results in forest trees. Rare and common associations were discovered in eight genes involved in cell wall biosynthesis and lignification. With the increasing adoption of genomic prediction of complex phenotypes using shared SNPs and much larger tree breeding populations, Joint-GWAS approaches should provide increasing power to pinpoint discrete associations potentially useful toward tree breeding and molecular applications.

Genomic selection prediction models comparing sequence capture and SNP array genotyping methods

The successful application of genomic selection (GS) approaches is dependent on genetic makers derived from high-throughput and low-cost genotyping methods. Recent GS studies in trees have predominantly relied on SNP arrays as the source of genotyping, though this technology has a high entry cost. The recent development of alternative genotyping platforms, tailored to specific species and with low entry cost, has become possible due to advances in next-generation sequencing and genome complexity reduction methods such as sequence capture. However, the performance of these new platforms in GS models has not yet been evaluated, or compared to models developed from SNP arrays. Here, we evaluate the impact of these genotyping technologies on the development of GS prediction models for a Eucalyptus breeding population composed of 739 trees phenotyped for 13 wood quality and growth traits. Genotyping data obtained with both methods were compared for linkage disequilibrium, minor allele frequency, and missing data. Phenotypic prediction methods RR-BLUP and BayesB were employed, while predictive ability using cross validation was used to evaluate the performance of GS models derived from the different genotyping platforms. Differences in linkage disequilibrium patterns, minor allele frequency, missing data, and marker distribution were detected between sequence capture and SNP arrays. However, RR-BLUP and BayesB GS models resulted in similar predictive abilities. These results demonstrate that both genotyping methods are equivalent for genomic prediction of the traits evaluated. Sequence capture offers an alternative for species where SNP arrays are not available, or for when the initial development cost is too high.