Grandis Clones Research Articles

Durability of thermally modified Eucalyptus wood against marine borer attack

Wood is a prevalent material in marine construction, both for fixed and mobile structures. However, the impact of xylophagous organisms diminishes its longevity by compromising its physical and mechanical properties. This study aimed to assess the influence of genetic variation and thermal treatment on the durability of Eucalyptus spp. wood against marine borers. Thermal modification was conducted in a kiln at 200 ºC for 14 hours, encompassing heating, exposure to peak temperature, and cooling stages. Two hybrids of E. grandis x E. urophylla, an E. grandis clone and an E. urophylla clone were tested. The experiment took place in the municipality of Pontal do Paraná (Paraná State, Brazil), using EN 275 (1992) guidelines with appropriate adaptations, during six months (summer and autumn). The extent of wood damage was visually evaluated, and damage intensity was categorized. All wood samples, irrespective of genetic material or thermal treatment, experienced attacks ranging from severe to complete infestation. Hence, the utilization of these species and hybrids in marine environments, whether in their natural state or after thermal modification, is not advisable given their insufficient resistance against marine borers.

Relações entre o espaçamento arbóreo e características do campo nativo em sistemas silvipastoris no bioma Pampa

ABSTRACT: The current study assessed the association of eucalyptus-tree spacing with forest growth and yield, as well as with the floristic composition, diversity and yield of natural grassland grown in silvopastoral systems in Pampa biome. Data were collected in six family cattle-ranching area in Bagé County (RS). The effect of two different genetic materials (seminal-origin Eucalyptus dunnii plant and one Eucalyptus grandis clone) on shading features of plants grown in 3 planting-spacing dimensions(625, 312 and 208 trees ha-1) was assessed, as well as their association with herbaceous extract (bare soil; green cover; forage dry matter; floristic composition; species richness; and grass, legumes and winter - and summer-growth species rates) and forestry (litter accumulation, diameter at breast height, total height and volume per hectare) variables. Planting carried out at the highest tree density (625 trees ha-1) has increased forest yield. However, it reduced green cover, herbaceous extract dry-matter yield and species richness, mainly in grasses and legumeswith greater forage potential. Conversely, it is possible combining forestry and animal yield to the preservation of native forage species at low tree densities (204 to 312 trees ha-1).

Wood ash content variation in Eucalyptus grandis clones in Mozambique

The sustainability of native forests in Sub-Saharan Africa depends on the diversification of sources to generate bioenergy, and Eucalyptus spp. wood has been highlighted. However, the determination of energy quality parameters has been a challenge to enable plantation wood to generate energy. The research assessed the ash content of radial and longitudinal samples of Eucalyptus grandis (Hill) clone with different ages and growth sites. Samples were collected in three pre-established plots in the center of Mozambique. Five trees were cut down in each plot and six discs were removed from each tree. Grinded samples with <0.5 mm particle size were generated from the heartwood and sapwood of each disk to determine the ash content. Wood from 7-year-olds had a higher ash content compared to 9-year-olds. The two sample plots differed from each other in terms of wood ash content. Heartwood samples had smaller ash content than sapwood samples. In general, the ash content of the intermediate positions was lower than those from the base and top of the stem, for both radial sections. No conclusive differences were found between samples from the base and the top of the trees, indicating that the material from the top of the trees can also be used as wood fuel. Ash content can be a considerable parameter to assess the quality of the wood of Eucalyptus spp. as a fuel.

Influence of Two Cutting Propagation Systems on Early Field Growth of Four Eucalyptus urophylla × Eucalyptus grandis Clones in the Republic of Congo

Influence of Two Cutting Propagation Systems on Early Field Growth of Four Eucalyptus urophylla × Eucalyptus grandis Clones in the Republic of Congo

Use of Eucalyptus grandis clones treated with a water repellent to improve the dimensional stability of utility poles

Wood is a common construction material used in most environments. However, its sensibility to abiotic agents, in particular those that affect the dimensional stability, limits the materials durability and decreases its properties. In this work, the efficiency of a paraffin-emulsion-based product as a water repellent, combined with the selection of Eucalyptus grandis clones with a low cracking index, was tested for its use in utility poles in order to improve the woods dimensional stability. Four selected Eucalyptus grandis clones were treated with the product mixed with Chromated Copper Arsenate - the most commonly used wood protector - in a single stage by the Bethell method at two retention levels. The dimensional stability of the treated samples was studied through the determination of anti-shrink efficiency. Test samples were also exposed to accelerated weathering processes for 200 h, and later analyzed by SEM microscopy. Results showed a significant improvement in the dimensional stability of treated wood when compared to samples without the water repellent, with variable efficacy depending on the clone used. Despite the weathering process slightly affected the appearance of the wood surface, the product is suitable for exterior use

Variation in Botryosphaeriaceae from Eucalyptus plantations in YunNan Province in southwestern China across a climatic gradient

ABSTRACTThe Botryosphaeriaceae accommodates many important pathogens of woody plants, including Eucalyptus. Recently, Botryosphaeriaceae were isolated from diseased plant parts from surveys of Eucalyptus plantations in the YunNan Province, China. The aims of this study were to identify these Botryosphaeriaceae isolates and to evaluate their pathogenicity to Eucalyptus. A total of 166 isolates of Botryosphaeriaceae were obtained from six regions in the YunNan Province, of which 76 were from Eucalyptus urophylla × E. grandis hybrids, 49 from E. globulus trees, and 41 isolates were from other unknown Eucalyptus species or hybrids. Isolates were identified by comparing DNA sequences of the internal transcribed spacer ribosomal RNA locus (ITS), partial translation elongation factor 1-alpha (tef1), β-tubulin 2 (tub2) and DNA-directed RNA polymerase II subunit (rpb2) genes, and combined with their morphological characteristics. Eleven species were identified, including Botryosphaeria fusispora, B. wangensis, Lasiodiplodia pseudotheobromae, Neofusicoccum kwambonambiense, N. parvum, and six novel species described as B. puerensis, N. dianense, N. magniconidium, N. ningerense, N. parviconidium and N. yunnanense. The dominant species across the regions were N. yunnanense, N. parvum and B. wangensis, representing 31.3, 25.3 and 19.9% of the total isolates, respectively. Species diversity and composition changed across the different climatic zones, despite their relatively close geographic proximity and the fact that some of the species have a global distribution. All the Botryosphaeriaceae species were pathogenic to one-year-old plants of an E. urophylla × E. grandis clone and E. globulus seed-derived plants, but showed significant inter- and intra-species variation in aggressiveness amongst isolates. The study provides a foundation for monitoring and management of Botryosphaeriaceae through selection and breeding of Eucalyptus in the YunNan Province of southwestern China.

Morphological and kinetic parameters of the absorption of nitrogen forms for selection of Eucalyptus clones

Eucalyptus clones are selected according to productivity, wood quality, rooting capacity, and resistance to drought, frost and diseases. However, kinetic and morphological parameters that determine the absorption efficiency of nutrients such as nitrate (NO3−) and ammonium (NH4+) are often not considered in breeding programs. The objective of this study was to evaluate the morphological, physiological and kinetic parameters of nitrogen uptake by clones of Eucalyptus saligna (32,864) and Eucalyptus grandis (GPC 23). Morphological parameters in shoot and root systems, biomass and N concentrations in different organs, photosynthetic pigment concentrations, parameters of chlorophyll a fluorescence and photosynthetic rates were evaluated. Kinetic parameters, maximum absorption velocity (Vmax), Michaelis–Menten constant (Km), minimum concentration (Cmin) and influx (I) were calculated for NO3− and NH4+ in the two clones. E. grandis clone was more efficient in the uptake of NO3− and NH4+, and showed lower Km and Cmin values, allowing for the absorption of nitrogen at low concentrations due to the high affinity of the absorption sites of clone roots to NO3− and NH4+. Higher root lengths, area and volume helped the E. grandis clone in absorption efficiency and consequently, resulted in higher root and shoot biomass. The E. saligna clone had higher Km and Cmin for NO3− and NH4+, indicating adaptation to environments with higher N availability. The results of NO3− and NH4+ kinetic parameters indicate that they can be used in Eucalyptus clone selection and breeding programs as they can predict the ability of clones to absorb NO3− and NH4+ at different concentrations.

Nitrogen supply methods affect the root growth dynamics in Eucalyptus grandis

Sandy soils presenting low organic matter levels do not provide enough N to meet Eucalyptus sp. demands. Nitrogen fertilizers can be applied to soil surface, although N losses tend to happen and to decrease the amounts of this component used by plants. Alternatively, N can be applied to planting pits at seedling transplantation time or to small holes dug close to the plants. However, aspects such as the impact of different N supply modes applied to the soil on the growth parameters of root systems and the way these supply modes can affect morphological and physiological parameters of the shoot remain poorly known. The aim of the current study is to assess shoot and root growth in Eucalyptus grandis trees grown in soil subjected to different N supply modes. Eucalyptus grandis clones (GPC 23) were subjected to three N supply modes, namely: control (without N application) (C), N application to soil surface (SN) and N application to the pit (PN). Plant height, stem diameter, N concentration and chlorophyll a fluorescence in leaves, morphological parameters of the root system (total root surface area and mean root diameter), total length of active roots and total number of living and dead roots were analyzed. The PN supply mode has led to the highest mineral N levels (NH4+ and NO3−) in the soil, as well as increased the total length of active roots, the number of living roots and the root surface area in soil layers 20–40 cm and 40–60 cm. This process has enabled greater N uptake by plants, which, in its turn, has increased N concentrations in leaves, favored photosynthetic processes and resulted in taller plants presenting greater stem diameter. The SN supply method did not increase the mineral N in the soil, and it restricted the total length of active roots in soil layer (0–20 cm) and resulted in higher mean root diameter.

INFLUENCE OF THE REPLANTING AGE ON YIELD AND GROWTH OF EUCALYPT CLONAL STANDS

ABSTRACT The growth of an eucalypt plantation should be monitored to identify factors that influence its development, helping in the decision-making process, aiming to reduce productivity losses. Thus, the objective of the present study was to evaluate the influence of the age of replanting on the yield and growth of eucalypt stands. The experiment was conducted in an area of CENIBRA S.A. Company, and established in a commercial plantation in August 2011. The application of herbicide and the ant control were performed in total area before planting. Seedlings of Eucalyptus urophylla × Eucalyptus grandis clones in 3.0 × 2.5 m spacing were used. Limestone (1,500 kg ha-1) was applied in total area before planting and 100 g plant-1 of NPK fertilizer (06-30-06) was applied immediately after planting. Four months after the installation of the experiment, 300 kg ha-1 of NPK (06-10-29) was applied. Treatments consisted of four dates of seedling replanting (0, 20, 40 and 80 days after planting) without complementary fertilization, and two treatments (replanting 40 and 80 days after planting) with supplementary fertilization (100g plant-1 NPK 06-30-06). The individual volume of replanting trees was 46.6% lower than of non-replanted ones. Treatments with complementary planting fertilization did not differ (p > 0.05) by the T-test. It is concluded that the longer the time between planting and replanting, the smaller the individual volume of the replanting trees and that the complementary fertilization in seedlings replanted does not favor their growth.

Active Fungal Communities in Asymptomatic Eucalyptus grandis Stems Differ between a Susceptible and Resistant Clone.

Fungi represent a common and diverse part of the microbial communities that associate with plants. They also commonly colonise various plant parts asymptomatically. The molecular mechanisms of these interactions are, however, poorly understood. In this study we use transcriptomic data from Eucalyptus grandis, to demonstrate that RNA-seq data are a neglected source of information to study fungal–host interactions, by exploring the fungal transcripts they inevitably contain. We identified fungal transcripts from E. grandis data based on their sequence dissimilarity to the E. grandis genome and predicted biological functions. Taxonomic classifications identified, amongst other fungi, many well-known pathogenic fungal taxa in the asymptomatic tissue of E. grandis. The comparison of a clone of E. grandis resistant to Chrysoporthe austroafricana with a susceptible clone revealed a significant difference in the number of fungal transcripts, while the number of fungal taxa was not substantially affected. Classifications of transcripts based on their respective biological functions showed that the fungal communities of the two E. grandis clones associate with fundamental biological processes, with some notable differences. To shield the greater host defence machinery in the resistant E. grandis clone, fungi produce more secondary metabolites, whereas the environment for fungi associated with the susceptible E. grandis clone is more conducive for building fungal cellular structures and biomass growth. Secreted proteins included carbohydrate active enzymes that potentially are involved in fungal–plant and fungal–microbe interactions. While plant transcriptome datasets cannot replace the need for designed experiments to probe plant–microbe interactions at a molecular level, they clearly hold potential to add to the understanding of the diversity of plant–microbe interactions.

QUALITY OF Eucalyptus urograndis CHARCOAL PRODUCED IN THE SOUTHERN REGION OF TOCANTINS

The objective of this work was to determine the quality of the Eucalyptus urophilla x Eucalyptus grandis clone charcoal, defining the basic density and wood retractability, apparent density, breaking index, charcoal yield, condensable and non-condensable gas yield, AQI and calorific values, comparing the results of different trunk positions and in two different heating ramps, ramp 1 (R1) with a heating rate of 1.25 ºC/min, final temperature of 450ºC and total of 6 hours, and ramp 2 (R2) with a heating rate of 1.19 ºC/min, final temperature of 500ºC and total time of 7 hours. The six evaluated trees were from a six-year-old cloned tree plantation located in the municipality of Gurupi, in the south of Tocantins state. The specimens for the characterizations were made from wooden discs removed from three trunk positions (base, DBH, top). The Eucalyptus urograndis wood presented basic density considered average (0.47 g/cm³) and good dimensional stability. The charcoal presented an expected yield and high calorific value influenced by the final temperature of the heating ramps, high fixed carbon content, acceptable ash content, as well as a low breaking rate. The results were satisfactory and identified the species as a good energy source.

Distance from the trunk and depth of uptake of labelled nitrate for dominant and suppressed trees in Brazilian Eucalyptus plantations: Consequences for fertilization practices

Climate changes will increase the probability of drought, which is likely to dramatically increase tree mortality. The capacity of trees to withdraw water in deep soil layers is an important trait likely to account for tree survival over prolonged droughts. Our study aimed to gain insight into the maximum distance from the trunk where Eucalyptus fine roots take up water and mobile nutrients in deep sandy soils during dry periods. NO3−-15N was injected in the soil at the end of the rainy season in commercial Eucalyptus stands planted with the same E. urophylla × E. grandis clone. The 15N tracer was applied in the middle of the inter-row (replicated in 3 plots): at 5 depths (from 0.1 to 6 m) at age 0.6 year, at 4 depths (from 0.1 to 9 m) at age 1.2 years, at 5 depths (from 0.1 to 12 m) at age 2.2 years, and at 6 depths (from 0.1 to 15 m) at age 6.4 years. δ15N was determined in leaves sampled in dominant and suppressed trees at different distances from each injection area, 4–5 months after NO3−-15N injection (after the dry season). While dominant trees took up NO3−-15N down to a depth of 6 m between 7 and 12 months after planting, the maximum depth of NO3−-15N uptake for suppressed trees was between 3 and 4.5 m. From 1.5 to 6 years after planting, a foliar enrichment in 15N was mainly detected when the NO3−-15N tracer was injected in the upper soil layers and only for a few trees at a depth of 6 m. Most of the uptake of 15N occurred within 2 m of horizontal distance from the injection site, whatever tree age and tree social status. Low amounts of NO3−-15N were taken up for injection sites located between 2 m and 5 m from the trunk, and 15N uptake was never detected at horizontal distances greater than 6 m from the trunk. Eucalyptus fine roots can take up nitrates at depths between 6 and 8 m the first year after planting. However, the NO3−-15N tracer injected at a depth of 6 m was only taken up by dominant trees and a 15N foliar enrichment of suppressed trees was only detected when the tracer was injected in the upper 3 m. Fertilizers must be applied within 2 m of the trunks in Eucalyptus plantations to be taken up by all trees, regardless of their social status. When fertilizations are concentrated the first months after planting in sandy soils, nutrient leaching in deep layers might increase the heterogeneity of the stands since mobile nutrients could only be taken up by dominant trees.

Influence of moisture content on the axial resistance and modulus of elasticity of clonal eucalyptus wood

Abstract The mechanical and physical properties of wood are important factors used to determining the suitability and application of wood material. Modulus of elasticity and resistance values of wood which is changed according to the factors such as, temperature, moisture content, and density. Obtained results in this study show that the modulus of elasticity and the axial resistance for studied clones woods increase when the wood moisture decreases. According to the stress of rupture, both woods are classified within the range of weak stress. In addition, these results show that Eucalyptus grandis clone 3758 has a high modulus of elasticity in compression and low axial resistance compared to E. camaldulensis clone 579.

Carfentrazone‐ethyl and glyphosate drift inhibits uredinial formation of Austropuccinia psidii on Eucalyptus grandis leaves

The response to infection of Austropuccinia psidii in resistant (CLR-383) and susceptible (CLR-384) Eucalyptus grandis clones, exposed to herbicide drift of carfentrazone-ethyl, glyphosate and a mixture of these two herbicides, was evaluated at microscopic and physiological levels. Plants of the two clones showed symptoms of phytotoxicity caused by herbicide drift. However, net CO2 assimilation rate, height and shoot dry matter were lower in CLR-384 than in CLR-383. At the ultrastructure level, the leaves of both clones exposed to the herbicides showed thylakoid disorganization and accumulation of starch grains in the chloroplasts. Only plants of CLR-384 were infected by A. psidii, but when exposed to herbicide drift, rust severity was lower than in control plants. Six days after inoculation (dai), plants of this clone exposed to the herbicides had smaller uredinia than control plants. At 12 dai, non-herbicide treated plants showed normal uredinia, containing abundant urediniospores. By contrast, plants exposed to the herbicides were less colonized by the fungus, and the uredinia were smaller with reduced production of urediniospores, which were sometimes not even detected. Glyphosate and carfentrazone-ethyl herbicide drift reduce infection and uredinial formation of A. psidii and to some extent induce basal resistance in a susceptible clone of E. grandis. © 2018 Society of Chemical Industry.

Genetic variability of growth and wood chemical properties in a clonal population of Eucalyptus urophylla × Eucalyptus grandis in the Congo

Thirty-four Eucalyptus urophylla × Eucalyptus grandis hybrids were evaluated with a view to selecting for improved growth and wood-quality traits for plantations in the Congo. Height, circumference at breast height and volume were measured at 12, 27, 37, 49 and 60 months. Lignin content, the syringyl/guaiacyl ratio and total extractives content were predicted by near-infrared spectroscopy using wood powder samples collected from trees at breast height. While wood chemical properties were stable and under strong genetic control, growth traits were not. The genetic correlation between lignin content and growth was weak and negative, whereas the environmental correlation was also weak but positive. The genetic improvement of E. urophylla × E. grandis clones, based on growth features, leads to a limited decrease in lignin content and syringyl content and to a limited increase in extractives content.

Botrytis eucalypti, a novel species isolated from diseased Eucalyptus seedlings in South China

Eucalyptus has become a preferred species for the production of industrial products and also for the protection of natural forests in South China. Many diseases affect these trees, both on plantations and in nurseries. One such disease in Eucalyptus nurseries is grey mould caused by a species of Botrytis. Symptoms of grey mould were recently observed on stems and leaves of Eucalyptus urophylla × Eucalyptus grandis seedlings in nurseries in ZhanJiang, GuangDong Province, South China. Diseased stems and leaves were covered with mycelium, conidiophores, and conidia of the causal pathogen. The fungus was identified on the basis of DNA sequence comparisons and morphological features, and its pathogenicity was tested on three Eucalyptus clones. Based on sequence comparisons of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA and partial DNA sequences of five nuclear gene regions, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60), DNA-dependent RNA polymerase subunit II (RPB2), necrosis and ethylene-inducing proteins (NEP1 and NEP2), combined with morphological characteristics and culture growth rate, the fungus represents a previously undescribed species of Botrytis. This undescribed species is phylogenetically and morphologically closely to Botrytis cinerea and B. pelargonii, but can be distinguished from them by DNA sequences of HSP60, RPB2, NEP1, and NEP2 gene regions, conidial characteristics, and culture growth rate. Here, a description of the fungus, designated as Botrytis eucalypti sp. nov., is provided. The results of in vitro leaf inoculation tests demonstrate that B. eucalypti is virulent on all three tested E. urophylla × E. grandis clones.

RELATIONSHIP BETWEEN THE ANATOMY AND DRYING IN Eucalyptus grandis X Eucalyptus urophylla WOOD

ABSTRACT Drying is an important step to using wood and anatomical characteristics influence this process. Thus, the objective of this work was to evaluate the relationship between anatomy and wood drying. Samples with 2 x 2 x 4 cm were obtained from eight Eucalyptus urophylla x Eucalyptus grandis clones at 1.3 m height to evaluate the anatomy and drying in climate chamber during 15 days. Cell wall fraction was established as the parameter that best correlated with drying, the Pearson correlation coefficient between this parameter and moisture was -0.8986, -0.6580, 0.9216, 0.8743, 0.7131 and 0.8727 for saturated wood, and after 1, 2.5, 5, 10 and 15 days of drying, respectively. The frequency and vessel size, as well as the height and width of the rays showed low relation with wood drying. Wood anatomy, mainly the cell wall fraction, influences moisture losses and should be considered in wood drying programs.

IBA EFFICIENCY ON MINI-CUTTING ROOTING FROM TEAK (Tectona grandis Linn F.) CLONES

ABSTRACT This study aimed to evaluate IBA efficiency in mini-cuttings rooting based on four Tectona grandis clones. Vegetative samples were collected in a hydroponic mini-clonal hedge in Verde Novo reforestation company at Colider, Mato Grosso. A factorial arrangement (4 x 6) was utilized, based on Carapá, Ipê, GU5 and TB7 clones vs six IBA dosages (0, 1000, 2000, 4000, 8000 and 16000 mg L-1), in a randomized block design based on three repetitions and 16 mini-cuttings per experimental unit. Cutting evaluations were based on survival and rooting rates after greenhouse conditions, after shadow-house, and at sun exposure, besides, total height, collar diameter, aerial and root biomass were also analyzed. Results registered a 95,4% average survivance rate as well as a 91,8% rooting rate, considered as very high for this tree species. IBA dosages utilization did not produce a significative effect on rooting mini-cuttings from these investigated clones. However, there were different responses among clones, which suggests a genotypic effect.

CRESCIMENTO INICIAL E CONCENTRAÇÃO DE NUTRIENTES EM CLONES DE<i> Eucalyptus urophylla</i> x <i>Eucalyptus grandis</i> SOB INTERFERÊNCIA DE PLANTAS DANINHAS

http://dx.doi.org/10.5902/1980509821099A presença de plantas daninhas em plantios de eucalipto, especialmente nos dois primeiros anos, pode acarretar grandes prejuízos à produtividade, pois reduz a eficiência de aproveitamento dos recursos de crescimento pela cultura. Assim, objetivou-se com este trabalho avaliar os efeitos da interferência de plantas daninhas sobre o crescimento inicial de dois clones de Eucalyptus urophylla x Eucalyptus grandis e sobre a concentração foliar de nutrientes na cultura e nas plantas daninhas. O experimento foi instalado em esquema fatorial 2 x 5 + 7, sendo dois clones de híbridos de Eucalyptus urophylla x Eucalyptus grandis, identificados como CNB001 e CNB016, em competição com cinco espécies de plantas daninhas Urochloa decumbens (capim-braquiária), Ipomoea nil (corda-de-viola), Commelina diffusa (trapoeraba), Spermacoce latifolia (erva-quente) e Panicum maximum (capim-colonião). Adicionalmente foram cultivados os dois clones de eucalipto e as cinco plantas daninhas em monocultivo como padrão de comparação, no delineamento inteiramente casualizado, com quatro repetições. Foram avaliados o crescimento inicial de mudas de eucalipto através da altura de plantas, o diâmetro do coleto, o número de ramos, a área foliar e matéria seca, o teor foliar de nutrientes do eucalipto, bem como o teor de nutrientes nas folhas das plantas daninhas. O clone CNB001 apresentou crescimento inicial superior ao clone CNB016, no entanto, livre da interferência de plantas daninhas, verificaram-se teores foliares semelhantes para a maioria dos nutrientes em ambos os genótipos. O clone CNB016 mostrou maior sensibilidade à interferência negativa das plantas daninhas que o clone CNB001, sendo seu crescimento inicial mais afetado por Ipomoea nil e a concentração de nutrientes reduzida pelas espécies Panicum maximum, Urochloa decumbens e Commelina diffusa. Panicum maximum apresentou maior interferência com o clone CNB001, enquanto Ipomoea nil pouco influenciou o crescimento e o teor de nutrientes deste híbrido. As plantas daninhas apresentaram elevada capacidade de extrair nutrientes do solo, mesmo em convivência com os clones de Eucalyptus urophylla x Eucalyptus grandis. A interferência imposta à cultura é dependente da espécie infestante e do genótipo de eucalipto.

The Eucalyptus grandis NBS-LRR Gene Family: Physical Clustering and Expression Hotspots.

Eucalyptus grandis is a commercially important hardwood species and is known to be susceptible to a number of pests and pathogens. Determining mechanisms of defense is therefore a research priority. The published genome for E. grandis has aided the identification of one important class of resistance (R) genes that incorporate nucleotide binding sites and leucine-rich repeat domains (NBS-LRR). Using an iterative search process we identified NBS-LRR gene models within the E. grandis genome. We characterized the gene models and identified their genomic arrangement. The gene expression patterns were examined in E. grandis clones, challenged with a fungal pathogen (Chrysoporthe austroafricana) and insect pest (Leptocybe invasa). One thousand two hundred and fifteen putative NBS-LRR coding sequences were located which aligned into two large classes, Toll or interleukin-1 receptor (TIR) and coiled-coil (CC) based on NB-ARC domains. NBS-LRR gene-rich regions were identified with 76% organized in clusters of three or more genes. A further 272 putative incomplete resistance genes were also identified. We determined that E. grandis has a higher ratio of TIR to CC classed genes compared to other woody plant species as well as a smaller percentage of single NBS-LRR genes. Transcriptome profiles indicated expression hotspots, within physical clusters, including expression of many incomplete genes. The clustering of putative NBS-LRR genes correlates with differential expression responses in resistant and susceptible plants indicating functional relevance for the physical arrangement of this gene family. This analysis of the repertoire and expression of E. grandis putative NBS-LRR genes provides an important resource for the identification of novel and functional R-genes; a key objective for strategies to enhance resilience.