Wood Density and Hydraulic Properties of Ponderosa Pine From the Willamette Valley VS. the Cascade Mountains

The Willamette Valley (WV) race of ponderosa pine (Pinus ponderosa) is being widely planted for timber in the Willamette Valley, western Oregon, because it grows in habitats that are either too wet or too dry for Douglas-fir (Pseudotsuga menziesii). Compared to the eastern Cascade Mountains (CM), the WV has 3 to 5 times the annual precipitation and warmer temperatures year around. This study characterized the wood quality of the WV race (4 sites) and the CM (4 sites), and also compared the behavior of their wood for water transport for the living trees (1 site in the WV and 1 site in the CM). The average tree ages at the sites ranged from 30 to 83 years at breast height. Between rings 27 and 31, compared to the CM, the WV had denser wood (0.48 vs. 0.40 g/cm3), denser earlywood (0.41 vs. 0.36 g/cm3), and denser latewood (0.62 vs. 0.50 g/cm3), with no significant differences in mean latewood proportion (about 0.35) or mean growth ring width (about 2.5 mm). The pith-to-bark trend in density differed between regions. In the WV, total wood density, earlywood density, and latewood density increased with growth ring from the pith. In the CM, total wood density and latewood density decreased slightly with growth ring width, and earlywood density remained unchanged. An additional sample of younger trees (23 years at breast height) from a genetic trial in the WV in which the seed source was the CM, had low density wood in the first few rings (like the CM trees) but had a steady increase in wood density with growth ring number (like the WV trees). Specific conductivity (ks) of trunk wood was lower in the WV, consistent with its higher wood density and suggestive that the WV race is more drought-adapted than the CM populations. There was no decline in ks from outer to inner sapwood in the WV trees, but a large decline in the CM trees. In water transport experiments, at an applied air pressure of 3.0 MPa, the WV and CM trees had lost 19% and 32% of their ks, respectively, again suggesting that the WV trees are slightly more drought-adapted than are the CM trees. At the other applied air pressures tested (0.5, 2.0. 4.0, and 5.0 MPa), there were no significant differences in loss of conductivity between the two sites. Trunk wood from breast height had a 50% loss of ks at 3.3-3.6 MPa. The loss of relative water content (100% - RWC) was about the same in both sites, except at 4.0 MPa, in which the CM trees had a larger loss of RWC than the WV trees. More work is needed on physiology to better understand the wood density/water transport relations. Ponderosa pine may be more interesting to study than other species because the earlywood, which transports most of the water, shows substantial density differences between geographic regions

Uniform Selection as a Primary Force Reducing Population Genetic Differentiation of Cavitation Resistance across a Species Range

Background: Cavitation resistance to water stress-induced embolism determines plant survival during drought. This adaptive trait has been described as highly variable in a wide range of tree species, but little is known about the extent of genetic and phenotypic variability within species. This information is essential to our understanding of the evolutionary forces that have shaped this trait, and for evaluation of its inclusion in breeding programs. Methodology: We assessed cavitation resistance (P 50), growth and carbon isotope composition in six Pinus pinaster populations in a provenance and progeny trial. We estimated the heritability of cavitation resistance and compared the distribution of neutral markers (FST) and quantitative genetic differentiation (QST), for retrospective identification of the evolutionary forces acting on these traits. Results/Discussion: In contrast to growth and carbon isotope composition, no population differentiation was found for cavitation resistance. Heritability was higher than for the other traits, with a low additive genetic variance (h 2 ns = 0.4360.18, CVA = 4.4%). QST was significantly lower than FST, indicating uniform selection for P50, rather than genetic drift. Putativ

Contacts et acculturations en Méditerranée occidentale

La question des contacts entre les différents peuples qui bordent les rives de la Méditerranée nord occidentale est l’un des sujets phares de la recherche archéologique de ces trente dernières années. Que l’on parle d’époque archaïque et classique ou de Protohistoire et d’âge du Fer, les échanges et les processus d’acculturation de ces peuples qui entrèrent alors en contact les uns avec les autres : Grecs, Celtes, Phéniciens, Ibères, Ligures, Étrusques, ont retenu l’attention des chercheurs travaillant sur l’expansion grecque dans ces régions, sur les trafics commerciaux, sur les échanges culturels. L’œuvre de Michel Bats (Directeur de recherche honoraire du CNRS) traverse toutes ces thématiques : la présence des Phocéens et des Étrusques dans le bassin occidental de la Méditerranée, l’acculturation et les identités ethno-culturelles, les recherches sur la céramique et ses usages dans une perspective anthropologique, l’appropriation de l’écriture par les sociétés protohistoriques. Ses collègues et amis, en organisant ce colloque et en participant à ces actes, entendent lui témoigner leur amitié et leur dette intellectuelle. Ce volume réunit des articles des meilleurs spécialistes, actuels de la question - des chercheurs de toute la Méditerranée - autour des quatre grands thèmes que nous venons d’évoquer afin tout à la fois de dresser un bilan et de définir de nouvelles perspectives. Cet ouvrage présente donc aussi bien des synthèses - sur la présence grecque en Espagne, sur l’origine de l’écriture, sur les pratiques funéraires, sur les identités culturelles et ethniques - que des découvertes récentes concernant la thématique des contacts et de l’acculturation en Méditerranée nord occidentale : l’agglomération du Premier âge du Fer de La Cougourlude (Lattes, Hérault) fouillée durant l’été 2010 ; le sanctuaire hellénistique de Cumes et les fouilles récentes de Fratte en Italie ; les ateliers de potiers de Rosas en Espagne ; les dernières découvertes d’Olbia de Provence

Genome-wide distribution of genetic diversity and linkage disequilibrium in a mass-selected population of maritime pine

Background: The accessibility of high-throughput genotyping technologies has contributed greatly to the development of genomic resources in non-model organisms. High-density genotyping arrays have only recently been developed for some economically important species such as conifers. The potential for using genomic technologies in association mapping and breeding depends largely on the genome wide patterns of diversity and linkage disequilibrium in current breeding populations. This study aims to deepen our knowledge regarding these issues in maritime pine, the first species used for reforestation in south western Europe. Results: Using a new map merging algorithm, we first established a 1,712 cM composite linkage map (comprising 1,838 SNP markers in 12 linkage groups) by bringing together three already available genetic maps. Using rigorous statistical testing based on kernel density estimation and resampling we identified cold and hot spots of recombination. In parallel, 186 unrelated trees of a mass-selected population were genotyped using a 12k-SNP array. A total of 2,600 informative SNPs allowed to describe historical recombination, genetic diversity and genetic structure of this recently domesticated breeding pool that forms the basis of much of the current and future breeding of this species. We observe very low levels of population genetic structure and find no evidence that artificial selection has caused a reduction in genetic diversity. By combining these two pieces of information, we provided the map position of 1,671 SNPs corresponding to 1,192 different loci. This made it possible to analyze the spatial pattern of genetic diversity (H-e) and long distance linkage disequilibrium (LD) along the chromosomes. We found no particular pattern in the empirical variogram of H-e across the 12 linkage groups and, as expected for an outcrossing species with large effective population size, we observed an almost complete lack of long distance LD. Conclusions: These results are a stepping stone for the development of strategies for studies in population genomics, association mapping and genomic prediction in this economical and ecologically important forest tree species

Understanding the genetic bases of adaptation to soil water deficit in trees through the examination of water use efficiency and cavitation resistance: maritime pine as a case study

This article provides a comprehensive view on the existing knowledge related to adaptation to soil water deficit in maritime pine, a conifer species widely planted in the southwestern Europe. It synthesizes discoveries made in ecophysiology, quantitative and population genetics as well as in genomics, combining several layers of information at the genotypic, phenotypic and environmental levels. Particular focus is given to two major traits: water-use efficiency (WUE) and cavitation resistance (CR). The former is related the maintenance of productivity during periods of lower soil water availability, whereas the latter is tightly linked to survival during severe drought. The development of high throughput phenotypic technologies have made it possible to estimate genetic and environmental variance components of these key traits, providing clues about their suitability for breeding and the evolutionary forces that have shaped their variability. Both CR and WUE were screened in different ecotypes as well as in the Aquitaine breeding population, the main genetic resource of the most advanced maritime pine breeding program in Europe. While the unexpectedly low level of variation of CR within and between natural populations will most likely hamper its use in breeding application, for WUE the medium heritability, absence of unfavorable phenotypic and genetic correlations with diameter growth, as well as the high inter-site correlation and weak genotype-by-environment interaction indicates that artificial selection could be applied for this trait without unfavorable consequences for radial growth, at least within the Aquitaine provenance. On the other hand, recent advances in sequencing and genotyping technologies have contributed to reveal the genetic architecture (i.e. number, location and effect of quantitative trait loci) of these two traits. In combination with ultra-dense genetic linkage map and functional genomics approaches, these findings will contribute to identify positional and expressional candidate genes that should be validated by association genetics and eventually introduced in genomic prediction models to make such knowledge useful to improve tree breeding

Imaging Redox Activity at Bipolar Electrodes by Indirect Fluorescence Modulation

Bipolar electrochemistry (BPE) is nowadays well-known but relatively underexploited and still considered as unconventional. It has been used, among others, in the frame of materials science and most importantly has also found very promising applications in analytical chemistry. Here, we extend this emerging field of analytical applications to the development of a new sensing concept based on indirect BPE. This approach is based on the generation of local pH gradients which will allow detecting indirectly redox-active molecules due to a modulation of the fluorescence intensity in the vicinity of a bipolar electrode.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Can wood density be efficiently selected at early stage in maritime pine (Pinus pinaster Ait.)?

La croissance et la rectitude du tronc sont les deux principaux critères de sélection dans le programme d'amélioration génétique du pin maritime en France. Cette étude a pour objectif d'évaluer la possibilité de sélectionner la densité du bois au stade juvénile. Plus de 1 900 arbres, provenant de trois tests, ont été analysés par microdensitométrie. Des gains génétiques relatifs élevés ont été mis en évidence pour la densité du bois au stade adulte (3 à 9 %). Les estimations de la densité réalisées aux stades adulte et juvénile étant bien corrélées, l'efficacité relative de la sélection atteint environ 80 % à l'âge de 12 ans. Les mesures de densité par rayons X ne sont pas envisageables à grande échelle dans le cadre d'un programme d'amélioration, ainsi nous avons évalué l'efficacité de l'utilisation du Résistographe, une méthode indirecte pour estimer la densité du bois sur arbres debout. Des corrélations élevées ont été mises en évidence entre les données obtenues avec le Résistographe et celles obtenues par microdensitométrie (R2 = 0.93 avec les données familiales). Il semble donc possible d'intégrer la densité du bois, estimée avec le Résistographe, comme nouveau critère de sélection dans notre programme d'amélioration.Growth and stem straightness are the two main selection criteria in the French maritime pine breeding programme. In this contribution, our objective was to study the possibility of selecting for wood density assessed at an early stage. We measured X-ray wood density, in three progeny tests, on more than 1 900 breast high increment cores. High relative expected genetic gain (from 3 to 9%) was found for wood density at mature stage. Juvenile and adult wood density estimations were well-correlated; the relative efficiency of early selection reached about 80% at 12 years old. As it would not be realistic to use the X-ray densitometer at an operational scale in a breeding programme, we tested the efficiency of using the Resistograph, an indirect method to assess wood density on live trees. High correlation between the Resistograph and density data (R2 = 0.93 on familial data) was found, suggesting that wood density through Resistograph assessment could be soon integrated as a new selection criterion in our breeding programme

Paternity recovery in two maritime pine polycross mating designs and consequences for breeding

Polycross mating systems are widely used in forest tree breeding for genetic testing. Backward selection based on polycross testing assumes equal male reproductive success and true half-sib progeny. The main objectives of this study were, firstly, to investigate the departure from these assumptions in a maritime pine polycross trial and, secondly, to evaluate the consequences for heritability and breeding values estimations. A total of 984 offspring from 98 half-sib families was genotyped with single nucleotide polymorphism markers to recover the full pedigree. Paternity was assigned successfully for 89 % of the offspring at a 99 % confidence level. We thus concluded there was an 11 % pollen contamination rate, assuming contamination when no genotype from the polymix composition could be identified as a father. The paternal contribution to the offspring varied among the males, but the departure from half-sib assumption was moderate since the average genetic correlation within the family was 0.26. Heritability and breeding values for girth at breast height and stem sweep were estimated using individual-tree mixed models with either partial or full pedigree information. The results highlighted a minor bias in heritability estimation due to unknown paternity, as well as a high correlation for estimated breeding values between the partial and full pedigree models, suggesting that the genetic merit of the parental generation for backward selection was adequately predicted using the partial pedigree model. Finally, pedigree recovery was also discussed in a perspective of forward selection