Genomic selection based on the single-step genomic best linear unbiased prediction (ssGBLUP) approach is becoming an important tool in forest tree breeding. The quality of the variance components and the predictive ability of the estimated breeding values (GEBV) depends on how well marker-based genomic relationships describe the actual genetic relationships at unobserved causal loci. We investigated the performance of GEBV obtained when fitting models with genomic covariance matrices based on two identity-by-descent (IBD) and two identity-by-state (IBS) relationship measures. Multiple-trait multiple-site ssGBLUP models were fitted to diameter and stem straightness in five open-pollinated progeny trials of Eucalyptus dunnii, genotyped using the EUChip60K. We also fitted the conventional ABLUP model with a pedigree-based covariance matrix. Estimated relationships from the IBD estimators displayed consistently lower standard deviations than those from the IBS approaches. Although ssGBLUP based in IBS estimators resulted in higher trait-site heritabilities, the gain in accuracy of the relationships using IBD estimators has resulted in higher predictive ability and lower bias of GEBV, especially for low-heritability trait-site. ssGBLUP based on IBS and IBD approaches performed considerably better than the traditional ABLUP. In summary, our results advocate the use of the ssGBLUP approach jointly with the IBD relationship matrix in open-pollinated forest tree evaluation.

Genetic parameters for growth, stem straightness, pilodyn penetration, relative bark thickness and survival were estimated in a base-population of five open-pollinated provenance/progeny trials of Eucalyptus viminalis. The trials, located in northern, central and southern Buenos Aires Province, Argentina, comprised 148 open-pollinated families from 13 Australian native provenances and eight local Argentinean seedlots. The Australian native provenances come from a limited range of the natural distribution. Overall survival, based on the latest assessment of each trial, was 62.4%. Single-site analyses showed that statistically significant provenances differences (p<0.05) for at least one of the studied traits in three out of the five trials analyzed. The local land race performed inconsistently in this study. The average narrow-sense individual-tree heritability estimate b h 2 was 0.27 for diameter and 0.17 for total height. Values of b h 2 also increased with age. Pilodyn penetration, assessed at only one site, was more heritable b h 2 ¼ 0:32 than the average of growth traits. Estimated individual-tree heritabilities were moderate to low for stem straightness (average of 0.20) and relative bark thickness (0.16). The estimated additive genetic correlations r A ð Þ between diameter and height were consistently high and positive (rAaverage of 0.90). High additive genetic correlations were observed between growth variables and pilodyn penetration (rA average of 0.58). Relative bark thickness showed a negative correlation with diameter rA ¼ À0:39 ð Þ and height rA ¼ À0:51 ð Þ . The average estimated additive genetic correlation between sites was high for diameter (0.67). The implications of all these parameter estimates for genetic improvement of E. viminalis in Argentina are discussed.

Background: Functional genetic markers have important implications for genetic analysis by providing direct estimation of functional diversity. Although high throughput sequencing techniques for functional diversity analysis are being developed nowadays, the use of already well established variable markers present in candidate genes is still an interesting alternative for mapping purposes and functional diversity studies. SSR markers are routinely used in most plant and animal breeding programs for many species including Eucalyptus. SSR markers derived from candidate genes (SSR-CG) can be used effectively in co-segregation studies and marker-assisted diversity management. Results: In the present study, eight new non reported SSRs were identified in seven candidate genes for wood properties in Eucalyptus globulus: cinnamoyl CoA reductase (CCR), homocysteine Smethyltransferase (HMT), shikimate kinase (SK), xyloglucan endotransglycosylase 2 (XTH2), cellulose synthase 3 (CesA3), glutathione S-transferase (GST) and the transcription factor LIM1. Microsatellites were located in promoters, introns and exons, being most of them CT dinucleotide repeats. Genetic diversity of these eight CG-derived SSR-markers was explored in 54 unrelated genotypes. Except for XTH2, high levels of polymorphism were detected: 93 alleles (mean of 13.1 sd 1.6 alleles per locus), a mean effective number of alleles (Ne) of 5.4 (sd 1.6), polymorphic information content values (PIC) from 0.617 to 0.855 and probability of Identity (PI) ranging from 0.030 to 0.151. Conclusions: This is the first report on the identification, characterization and diversity analysis of microsatellite markers located inside wood quality candidate genes (CG) from Eucalyptus globulus. This set of markers is then appropriate for characterizing genetic variation, with potential usefulness for quantitative trait loci (QTL) mapping in different eucalypts genetic pedigrees and other applications such as fingerprinting and marker assisted diversity management.

The effect of initial planting density on the growth and wood density of Eucalyptus globulus was examined in a trial established in the southeast of Buenos Aires Province, Argentina. A modified Nelder design was used to generate 9 planting densities ranging from 582 to 2.083 trees/ha. The effect of planting density on diameter at breast height, total tree height, basal area, relative bark thickness and wood density was studied over a 10-year period. By reducing the initial density of planting to 761 trees/ha, an increase on individual tree growth was observed, principally on diameter and to a lesser extent on tree height. However, basal area (m2/ha) was greatest at intermediate densities. Initial planting density affected wood basic density at 6 years of age but not relative bark thickness. In conclusion, 1,095 trees/ha was found to be the best initial density to optimize individual and stand growth.