Maria João Gaspar

Use of molecular markers for estimating breeding parameters: a case study in a Pinus pinaster Ait. progeny trial

The management of a genetic improvement program is based on the knowledge of the genetic parameters and their relationships to determine the genetic gains. Knowledge of the coefficient of coancestry (θ) is a requirement for efficient progeny testing scheme and for estimating additive variance components for any quantitative trait. When using open-pollinated families, most authors assume that the seedlings are related as half-sibs, but this is not always true. Our aim was to estimate a mean value of the coancestry coefficient of the families present in a maritime pine Pinus pinaster Ait. (maritime or cluster pine) progeny trial originating from seed collected in a clonal seed orchard and to study how deviations from the standard assumption of θ = 0.125 affect heritability estimations. Five highly polymorphic microsatellite markers were scored in 125 offspring from a subsample of five families from the progeny trial. The mean value of the coancestry coefficient of the families present in this progeny trial was 0.130. Differences between the unadjusted and adjusted heritability estimates were more pronounced in wood density (0.609 and 0.586, respectively) than in diameter (0.166 and 0.154, respectively). We conclude that in the trial, the associated error in heritability estimates due to the inclusion of full-sibs, when assuming a standard coefficient of relationship among open-pollinated sibs of 0.250, was low and that this result is robust with respect to the number of families sampled, given unbiased estimates of average relationship among offspring within sib families.

A comprehensive assessment of the transcriptome of cork oak (Quercus suber) through EST sequencing

BackgroundCork oak (Quercus suber) is one of the rare trees with the ability to produce cork, a material widely used to make wine bottle stoppers, flooring and insulation materials, among many other uses. The molecular mechanisms of cork formation are still poorly understood, in great part due to the difficulty in studying a species with a long life-cycle and for which there is scarce molecular/genomic information. Cork oak forests are of great ecological importance and represent a major economic and social resource in Southern Europe and Northern Africa. However, global warming is threatening the cork oak forests by imposing thermal, hydric and many types of novel biotic stresses. Despite the economic and social value of the Q. suber species, few genomic resources have been developed, useful for biotechnological applications and improved forest management.ResultsWe generated in excess of 7 million sequence reads, by pyrosequencing 21 normalized cDNA libraries derived from multiple Q. suber tissues and organs, developmental stages and physiological conditions. We deployed a stringent sequence processing and assembly pipeline that resulted in the identification of ~159,000 unigenes. These were annotated according to their similarity to known plant genes, to known Interpro domains, GO classes and E.C. numbers. The phylogenetic extent of this ESTs set was investigated, and we found that cork oak revealed a significant new gene space that is not covered by other model species or EST sequencing projects. The raw data, as well as the full annotated assembly, are now available to the community in a dedicated web portal at http://www.corkoakdb.org.ConclusionsThis genomic resource represents the first trancriptome study in a cork producing species. It can be explored to develop new tools and approaches to understand stress responses and developmental processes in forest trees, as well as the molecular cascades underlying cork differentiation and disease response.

Genetic correlations between wood quality traits of Pinus pinaster Ait

Abstract• It is essential to understand how characteristics are related to each other in breeding programmes to select wood properties, in order to avoid that, in selecting for one trait, we are negatively affecting another. Moreover, measuring wood properties is time consuming and expensive.• This study assesses genetic and phenotypic correlations between wood density components and spiral grain of 46 half-sib families of Pinus pinaster in seventeen-year-old trees.• Results showed that genetic correlations for all wood density components were higher than corresponding phenotypic correlations. Furthermore, all wood density components were highly genetically correlated with ring density, and also closely associated among themselves. Results showed a higher genetic correlation of ring density with earlywood density (rg = 0.96) than with latewood density rg = 0.79). A moderate to high positive genetic correlation was found between spiral grain and wood density characteristics (0.29–0.61).• We conclude that ring density (overall wood density) can be improved by increasing either earlywood density, latewood percent, or both of these traits, and spiral grain can be modify in future plantations.Résumé• En amélioration génétique, il est essentiel de connaître le degré de liaison entre caractères de manière à éviter lors de la sélection pour un caractère une contre-sélection pour un autre. De plus, la mesure des propriétés du bois est lourde et coûteuse.• Dans cette étude, nous étudions les corrélations génétiques et phénotypiques entre les composantes de la densité du bois et l’angle du fil chez 46 familles de demi-frères de Pinus pinaster âgées de 17 ans.• Les résultats montrent que les corrélations génétiques pour toutes les composantes de la densité du bois sont plus élevées que les corrélations phénotypiques. De plus, toutes les composantes de la densité sont fortement corrélées génétiquement avec la densité du cerne et étroitement liées entre elles. Les résultats indiquent une liaison génétique plus forte entre la densité du cerne et la densité du bois initial (rg = 0.96) qu’avec le bois final (rg = 0.79). Une corrélation génétique modérée à forte est mise en évidence entre l’angle du fil du bois et les caractéristiques de densité (0.29–0.61).• Nous concluons que la densité du cerne peut être améliorée soit en augmentant la densité du bois initial, soit la proportion de bois final, soit les deux et que l’angle du fil peut être modifié pour les plantations futures.

Evaluation of genetic diversity of Portuguese Pinus sylvestris L. populations based on molecular data and inferences about the future use of this germplasm.

1Institute for Biotechnology and Bioengineering, Centre of Genomics and Biotechnology (IBB/CGB), 3Department of Forestry Sciences and Landscape (CIFAP), and 4Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), University of Tras-os-Montes and Alto Douro (UTAD), P.O. Box 1013, 5001-801 Vila Real, Portugal 2Centre of Forestry Studies (CEF), ISA, UTL Tapada da Ajuda, 1349-017 Lisbon, Portugal

Physical location of SSR regions and cytogenetic instabilities in Pinus sylvestris chromosomes revealed by ND-FISH.

Portugal constitutes the southwestern end limit of the distribution area of Scots pine in the world. The population of ‘Ribeira das Negras’ (‘Serra do Geres’; NW Portugal) has been considered potentially native and peripheral. This species has 24 chromosomes, hardly distinguishable because of their similar size and shape. Cytogenetic studies are scarce and instabilities were previously reported in peripheral Scots pine populations. Here, we intended to cytogenetically characterize individuals from ‘Ribeira das Negras’ using 14 simple sequence repeats (SSRs) and 45S rDNA sequence (pTa71) as probes, by nondenaturing fluorescence in situ hybridization (ND-FISH) and FISH, respectively. Eight SSRs [(AC)10; (AG)10; (AG)12; (AAG)5; (AAC)5; (GATA)4; (GACA)5 and (GGAT)4] and pTa71 showed hybridization. The (AG)10 probe hybridized on all chromosomes and an ideogram was constructed. Each metaphase cell presented cytogenetic instabilities corroborating ‘Ribeira das Negras’ as a peripheral population. As far as we know, this is the first cytogenetic study in Scots pine using SSRs in FISH experiments. Scots pine (Pinus sylvestris L.) is one of the most widely distributed conifers across Eurasia and an economically important species as source of timber (Manson and Alia 2000). Peripheral populations of Scots pine are susceptible to marginal environments and could present high phenotypic variation as well as cytogenetic irregularities (Muratova 1994). Cytogenetic studies in gymnosperms constitute a hard task due to incomplete cell division synchronization

Genetic variation of chemical and mechanical traits of maritime pine (Pinus pinaster Aiton). Correlations with wood density components

Abstract• BackgroundGenetic selection for one trait can have an impact on other important traits for final use; thus, it is important to assess the correlation between traits.• MethodsGenetic control and relationships among lignin content predicted by near infrared spectroscopy, radial modulus of elasticity (MOERad) and the radial modulus of rupture (MORRad), as well as its correlations with wood density components and spiral grain were assessed by estimating heritability, phenotypic and genetic correlations using 552 Pinus pinaster trees from 46 half-sib families.• ResultsThe results of this study showed that lignin amount is under a moderate genetic control (h2 = 0.34) but due to the low coefficient of variation observed, selection for lignin content through breeding could yield modest gains. Selection based on density will result in a decrease of the lignin content, and that the lignin content was more dependent on the proportion of latewood.• ConclusionsThe results show that MOERad and MORRad are under moderate genetic control (h2 = 0.34 and h2 = 0.30 respectively), suggesting possible genetic gains by selection for higher resistance and elasticity. MOERad had higher correlations with latewood than earlywood components. Negative correlations were observed between mechanical traits and lignin content, while the correlations with spiral grain were positive.

Effects of Recent Minimum Temperature and Water Deficit Increases on Pinus pinaster Radial Growth and Wood Density in Southern Portugal

Western Iberia has recently shown increasing frequency of drought conditions coupled with heatwave events, leading to exacerbated limiting climatic conditions for plant growth. It is not clear to what extent wood growth and density of agroforestry species have suffered from such changes or recent extreme climate events. To address this question, tree-ring width and density chronologies were built for a Pinus pinaster stand in southern Portugal and correlated with climate variables, including the minimum, mean and maximum temperatures and the number of cold days. Monthly and maximum daily precipitations were also analyzed as well as dry spells. The drought effect was assessed using the standardized precipitation-evapotranspiration (SPEI) multi-scalar drought index, between 1 to 24-months. The climate-growth/density relationships were evaluated for the period 1958-2011. We show that both wood radial growth and density highly benefit from the strong decay of cold days and the increase of minimum temperature. Yet the benefits are hindered by long-term water deficit, which results in different levels of impact on wood radial growth and density. Despite of the intensification of long-term water deficit, tree-ring width appears to benefit from the minimum temperature increase, whereas the effects of long-term droughts significantly prevail on tree-ring density. Our results further highlight the dependency of the species on deep water sources after the juvenile stage. The impact of climate changes on long-term droughts and their repercussion on the shallow groundwater table and P. pinaster’s vulnerability are also discussed. This work provides relevant information for forest management in the semi-arid area of the Alentejo region of Portugal. It should ease the elaboration of mitigation strategies to assure P. pinaster’s production capacity and quality in response to more arid conditions in the near future in the region.

Within and between-tree variation of wood density components in Pinus sylvestris at five sites in Portugal

Pinus sylvestris is widely distributed in Europe and Asia, and Portugal constitutes its westernmost limit. The reduction of the Portuguese forest area of resinous species has provoked strong constraints on wood industries supply. Therefore, an increase in Scots pine area might be important, namely by reforestations of higher altitude areas, where Pinus pinaster has great difficulties to vegetate and where the risk of pinewood nematode attack is smaller. However, large gaps remain in the knowledge of Pinus sylvestris wood characteristics growing in Portugal. To address this question, the radial wood density and growth were evaluated by X-ray microdensitometric technique, sampling 100 adult trees from five representative sites of P. sylvestris distribution area in Portugal. The results revealed that Portuguese Pinus sylvestris shows good radial growth and denser wood than those found in northern European regions. Among the Portuguese stands, sites at a lower altitude (Gerês and Marão) exhibited denser wood. Regarding density components, it was verified that the differences among sites were more significant in latewood, while the differences between trees/sites were most expressive in earlywood. These facts induce a higher genetic control in earlywood characteristics and a greater dependence of latewood components on environmental and climatic effects. Regarding growth components, Trees and Rings effects were more noticeable than Site effect. Concerning radial patterns, Portuguese Pinus sylvestris shows a downward trend in the first years after the pith, followed by an increase in latter rings for the density traits, while the radial variation of ring width is expressed by a tendency of decrease from the pith to the cambium. Compared to other European regions, Portuguese Pinus sylvestris reveals good wood quality features, namely higher density and ring width values. However, compared to Portuguese Pinus pinaster it shows a relatively lower density and identical or relatively lower radial growth. Scots pine could be a good solution for future reforestations of Portuguese mountainous areas, less favorable to other species.