-This article describes changes in the genetic variation of wood density components with cambial age and their relationship with the within-ring area components. Wood samples from 31 half-sib families of radiata pine were submitted to X-ray densitometry procedures. Traits studied were earlywood (ED) and latewood (LD) density, earlywood (EA) and latewood (LA) area, and latewood proportion (LP). Between rings 2 to 5 (juvenile wood) and 11 to 14 (mature wood), heritability estimates suggest that breeding for increased ED is feasible. Upward selection for ED would also be associated with a phenotypic reduction in EA in juvenile and mature wood. Between rings 6 to 10, the heritability estimates for ED indicate low genetic variation in the transition region. Attempts to increase ED by breeding might not have a significant impact on LD, though this trait showed a moderate genetic control in this region. Any change in ED and LD would have unclear effects on EA and LA, respectively, because of the changing pattern of genetic covariances.wood density / heritability / radiata pine / earlywood / latewood Résumé -Variabilité génétique de composantes de la densité du bois dans un test de descendances de pin radiata dans le sud du Chili. Cet article décrit l'évolution en fonction de l'age cambial de la variabilité génétique de composantes de la densité intra-cerne et des relations entre ces caractères et des composantes de la surface des cernes. Des échantillons de bois appartenant à 31 familles de demi-frères de pin radiata ont été soumis à une procédure d'analyse microdensitométrique. Les caractères étudiés sont la densité du bois initial (ED) et du bois final (LD), la surface du bois initial (EA) et du bois final (LA) et la proportion de bois final dans le cerne. Entre les cernes 2 à 5 (bois juvénile) et les cernes 11 à 14 (bois adulte), les valeurs estimées d'héritabilité suggèrent qu'il est possible d'augmenter ED génétiquement. Une sélection pour une augmentation de ED entraînerait une diminution phénotypique de EA dans le bois juvénile et le bois adulte. Dans la région de transition représentée par les cernes 6 à 10, les estimations de l'héritabilité montrent peu de variabilité génétique. Des tentatives d'augmenter génétiquement la densité de ED pourraient ne pas avoir d'effet significatif sur LD, même si ce caractère est lui-même moyennement génétiquement contrôlé dans cette zone. Toute modification de ED et LD aurait des effets changeants sur EA et LA en raison des variations de la valeur des covariances génétiques.densité du bois / héritabilité / pin radiata / bois initial / bois final

Eucalyptus cladocalyx F. Muell is a tree species suitable for low-rainfall sites, even with annual average precipitation as low as 150 mm per year. Its wood is classified as highly durable and its permanence in soil is longer than 25 years, so it can be used for multiple applications. Given that about 41% of the world’s land area is classified as drylands, added to the impact of climate change on the availability of water resources, it becomes necessary to use plant species that can tolerate environments with low water availability. In this study, a Bayesian analysis of genetic parameters showed that wood density (WD) was moderately heritable, with a posterior mean of h2 = 0.29 and a Bayesian credibility region (90%) of 0.06–0.74, while the slenderness coefficient (SC) was highly heritable, with a posterior mean of h2 = 0.48 and a Bayesian credibility region (90%) of 0.11–0.87. Through Bayesian regression analysis, we identified four and three significant associations for WD and SC, respectively. Another important finding of the bi-trait Bayesian analysis was the detection of three large-effect pleiotropic QTLs located on LG4 at 52 cM, on LG2 at 125 cM, and on LG6 at 81 cM. Bayesian bi-trait regression and the posterior probability of association indicated that three QTLs presented strong evidence of association with WD and SC. This provides convincing evidence that the loci qtlWD130/qtlSC130, qtlWD195/qtlSC195, and qtlWD196/qtlSC196 have a significant pleiotropic effect. The association mapping based on multivariate Bayesian regression was useful for the identification of genomic regions with pleiotropic effects. These loci can be used in molecular marker-assisted breeding to select trees with better wood density.

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Studying population structure has made an essential contribution to understanding evolutionary processes and demographic history in forest ecology research. This inference process basically involves the identification of common genetic variants among individuals, then grouping the similar individuals into subpopulations. In this study, a spectral-based classification of genetically differentiated groups was carried out using a provenance–progeny trial of Eucalyptus cladocalyx. First, the genetic structure was inferred through a Bayesian analysis using single-nucleotide polymorphisms (SNPs). Then, different machine learning models were trained with foliar spectral information to assign individual trees to subpopulations. The results revealed that spectral-based classification using the multilayer perceptron method was very successful at classifying individuals into their respective subpopulations (with an average of 87% of correct individual assignments), whereas 85% and 81% of individuals were assigned to their respective classes correctly by convolutional neural network and partial least squares discriminant analysis, respectively. Notably, 93% of individual trees were assigned correctly to the class with the smallest size using the spectral data-based multi-layer perceptron classification method. In conclusion, spectral data, along with neural network models, are able to discriminate and assign individuals to a given subpopulation, which could facilitate the implementation and application of population structure studies on a large scale.

& Key message Pith-to-bark wood density profiling is interesting in forestry science. By comparing it with the X-ray method, this study proved that a fiber optic NIR spectrometer with a high-precision displacement system could accurately measure intra-ring wood density with a spatial resolution of 0.5 mm. & Context Most near-infrared spectroscopy (NIRS) studies for wood density determination use samples that have been pulverized beforehand. Attenuation of ionizing radiation is still the standard method to determine wood density with high spatial resolution. However, there is evidence that NIRS could be an accurate and affordable method for determining intraring density in solid wood strips. & Aims In this study, we research whether the results published for intra-ring density predictions in wood can be improved when calibrated with X-ray microdensitometry. & Methods The measurements were made using a fiber optic probe with a separation between measurement points of 0.508 mm in a range between 1200 and 2200 nm. A total of 4520 density points were used to create partial least squares regression (PLSR). X-ray densitometry data were used as reference values. Twenty PLSR calibrations were randomly executed on 31 samples collected from 28 Pinus radiata D. Don trees. & Results Upon selecting 20 latent variables, the R 2 value was 0.873 for the training group and 0.895 for the validation group, while RMSEP values are 43.1 × 10 −3 and 47.1 × 10 −3 g cm −3 for the training and validation groups, respectively. The range error ratio (RER) was 13.7. & Conclusion The RER was high and almost in the range suggested for quantification purposes. Results are superior to wood density studies in the literature which do not employ spatial resolution and to those found in studies using hyperspectral imaging.

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The increase in prevalence of environmental pollution, especially soil contamination with toxic metals has led to their uptake in the human food chains through plant parts. Accumulation and magnification of heavy metals in human tissues through comsuption of herbal medicine can cause hazardous impacts on health. Therefore, chemical profiling of four heavy metals (Cu, Cr, Mn and Zn) was undertaken in samples of Azorella spinosa from coast and mountain of Maule Region in Chile. The Cu, Cr, Mn and Zn concentrations were determined in plants of the species Azorella spinosa and their soils of origin. For each plant, the metal contents in the stalk, leaves and soil were determined by flame atomic absorption spectroscopy. The methodology was validated using certified reference material: BIMEP-432 for the plant samples and MESS-1 for the soil samples. The concentration ranges found in the plant tissue were: Cu: