Screening for host responses in Acacia to a canker and wilt pathogen,Ceratocystis manginecans

In Vietnam, the productivity of Acacia hybrid (Acacia mangium x A. auriculiformis) plantations is being threatened by an aggressive canker pathogen, Ceratocystis manginecans, and selection for tolerance is the main control strategy. A pot trial was established in Binh Duong province to screen for the host response of nine Acacia genotypes (six Acacia hybrid clones, two A. auriculiformis clones and mixed provenance seedlings of A. mangium) to artificial inoculation with three isolates of C. manginecans. Lesion lengths as measured on the inner bark suggested that the two A. auriculiformis clones were relatively more tolerant to C. manginecans than the A. mangium genotype. In contrast, the lesion lengths of all six Acacia hybrid clones fell between the A. auriculiformis and A. mangium genotypes. The results of this study indicate that among the Acacia hybrid clones, BV10 showed the most tolerance to C. manginecans. Chemical analysis of crude sapwood extracts sampled from the lesion provided some evidence that induced phenolic compounds, particularly tetrahydroxyflavanone and condensed tannins may have a defensive role in the Acacia—C. manginecans pathosystem. However, results were not consistent across individual Acacia hybrid clones and A. mangium genotypes.     

Variation of heartrot,sapwood infection and polyphenol extractives with provenance of Acacia mangium

Infection of heartwood by decay fungi (heartrot) is a concern for growers of Acacia mangium for solid‐wood products as the incidence can be high in some regions of Indonesia. Variation of heartrot incidence for different provenances of A. mangium was determined using two field trials in Sumatra, Indonesia. In a Riau Province trial of 21 provenances, the effect of provenance was statistically significant for natural heartrot incidence, which ranged from 1.6% to 27.2%. In a smaller trial using artificial inoculation in South Sumatra, heartwood infection incidence ranged from 39.4% to 70.8% across six provenances and both wound type and provenance were statistically significant factors. There was also significant variation in sapwood infection length related to provenance. Wood extractives (yield, total phenols, protein‐precipitable tannin and 2,3‐trans‐3,4′,7,8‐tetrahydroxyflavanone) were quantified from a subsample of trees for each trial. However, no significant differences in extractive concentration were detectable according to provenance and evidence for a relationship between heartwood extractives and heartrot incidence was generally poor. While further studies need to be completed to establish the basis for heartrot incidence, results from these trials allow for recommendations on provenance selection to reduce heartrot incidence and provide information for further genetic selection programmes.     

The influence of heartwood on the pulping properties of Acacia melanoxylon wood

The pulping wood quality of Acacia melanoxylon was evaluated in relation to the presence of heartwood. The sapwood and heartwood from 20 trees from four sites in Portugal were evaluated separately at 5% stem height level in terms of chemical composition and kraft pulping aptitude. Heartwood had more extractives than sapwood ranging from 7.4% to 9.5% and from 4.0% to 4.2%, respectively, and with a heartwood-to-sapwood ratio for extractives ranging from 1.9 to 2.3. The major component of heartwood extractives was made up of ethanol-soluble compounds (70% of total extractives). Lignin content was similar in sapwood and heartwood (21.5% and 20.7%, respectively) as well as the sugar composition. Site did not influence the chemical composition. Pulping heartwood differed from sapwood in chemical and optical terms: lower values of pulp yield (53% vs 56% respectively), higher kappa number (11 vs. 7), and lower brightness (28% vs 49%). Acacia melanoxylon wood showed an overall good pulping aptitude, but the presence of heartwood should be taken into account because it decreases the raw-material quality for pulping. Heartwood content should therefore be considered as a quality variable when using A. melanoxylon wood in pulp industries     

Wood‐rotting basidiomycetes are a minor component of fungal communities associated with Acacia hybrid trees grown for sawlogs in South Vietnam

Acacia hybrid (Acacia mangium × Acacia auriculiformis) clones are widely planted in Vietnam with a total of approximately 400,000 ha to meet the demand for pulpwood, sawn timber and wood chip exports. Silvicultural techniques such as pruning and thinning have been applied to improve productivity and sawlog quality of Acacia hybrid plantations. However, those techniques may also create opportunities for wood decay fungi to enter the Acacia hybrid stems through wounds and cause stem defects that reduce sawlog quality and the value of the plantation. The presence of fungal decay agents in Acacia hybrid trees was examined in two Vietnamese plantations. In July 2011, just prior to a second thinning, discoloured wood samples were taken from a three‐year‐old Acacia hybrid plantation at Phan Truong Hai for the isolation of fungi. In July 2012, approximately 18 months after pruning and thinning treatments, discoloured wood samples were taken from a three‐year‐old Acacia hybrid plantation at Nghia Trung for the isolation of fungi. DNA sequencing of the rDNA ITS identified the isolates. In May 2015, approximately 4 years after thinning and fertilizer treatments, discoloured and decayed wood samples were taken from the above (7‐year‐old) Acacia hybrid plantation at Phan Truong Hai for fungal identification. DNA was extracted directly from discoloured and decayed wood samples and fungal rDNA ITS amplicons sequenced on a Roche 454 sequencer. The results showed that silvicultural treatments did not affect the fungal communities associated with discoloured and decayed wood of Acacia hybrid plantation at Phan Truong Hai. A total of 135 fungal species or OTUs (operational taxonomic units) were identified, including 82 members of Ascomycota and 52 Basidiomycota.     

Photosynthesis in co-occurring invasive Acacia spp. and native Bornean heath forest trees at the post-establishment invasion stage

Seedlings of invasive species often exhibit superior physiological traits that facilitate their spread at early stages of invasion, although it is unclear whether these traits persist at the post-establishment stage. To determine whether mature exotic Acacia spp. possess superior traits over mature native plants, we compared foliar gas exchange and chlorophyll a fluorescence of Acacia auriculiformis and Acacia mangium coexisting with tropical heath forest tree species Buchanania arborescens and Dillenia suffruticosa in Brunei Darussalam. The CO₂ assimilation rates of Acacia spp. were significantly higher than those of heath species at current prevailing conditions of ~400 ppm ambient CO₂, 1,500 µmol m^?2 s^?1 photosynthetically active radiation and 30°C leaf temperature. The photosystem II of Acacia spp. exhibited significantly higher maximum quantum yield of primary photochemistry at comparable temperatures, and was more sensitive to an elevated temperature (42°C for 1 h). Better photosynthetic performance of Acacia spp., due to larger stomatal openings, better light harvesting efficiency, and greater plasticity in photosystem II, may enable adult Acacia trees to sustain a competitive growth advantage and suppress native tropical heath forest species. The competitive advantage maintained by Acacia spp. in post-establishment stage likely facilitates the establishment of monospecific Acacia stands in invaded heath forests.     

Quantifying stem discoloration and decay following pruning and thinning an Acacia hybrid plantation

Acacia hybrid (Acacia mangium × A. auriculiformis) is widely planted in Vietnam, and part of the estate is managed for solid timber products. This requires pruning and thinning – practices that through mechanical wounding can facilitate the entry of fungal organisms, leading to stem defects. The extent to which this happens in Acacia hybrid has not been previously studied in Vietnam. A destructive survey was conducted in a 3‐year‐old Acacia hybrid plantation at Nghia Trung in Binh Phuoc province, 18 months after the imposition of pruning and thinning treatments. Pruned trees had a higher incidence and severity of discoloration and decay in the stem than unpruned trees; thinning increased the incidence of stem decay and the severity of discoloration but not the severity of decay. An interaction between pruning and thinning did not influence the incidence of stem decay but did increase the severity of discoloration in thinning treatments. Across treatments, levels of discoloration and decay were <30% and <5%, respectively. Modification of current pruning practices may be necessary to ensure that decay levels are kept within acceptable limits at an anticipated harvest age of 7–8 years.     

Growth and Development Responses of Three Acacia Species to Long-Term Light Regimes

Abstract

Three species of Acacia which are used in various forestry systems in Micronesia are the Acacia confusa Merr., A. mangium Willd., and A. auriculiformis Cunn. ex Benth. The responses of these species to limited light have not been established. The objective of this study was to determine the growth responses of these three species to light ranging from 19% to 100% sunlight transmission in order to determine the relative tolerance of these species to shade. Several common adaptations to low light occurred with all three species, such as increased leaf surface area in relation to mass of supportive tissue and reduced leaf mass per unit leaf area. However, other adaptations to low light were not evident. Numerous indicators of growth were decreased at low levels of sunlight transmission. The relative reduction in growth at 19% transmission compared with 100% transmission was similar for each species. The results indicate that these Acacia species exhibit some adaptations to development in limited light, but they are not tolerant of shade. All three species are thus classified as shade avoiders, and have limited application under shaded conditions in any Pacific island forestry system.     

Facilitation by two exotic Acacia: Acacia auriculiformis and Acacia mangium as nurse plants in South China

Because of their high growth rate and tolerance to bare soil, two exotic Acacia species, Acacia auriculiformis and Acacia mangium, have been commonly planted in degraded areas of South China. With their large canopies and ability to fix nitrogen, the two Acacia species have also been considered to act as nurse plants for understory plants. The current study clarified the nursing effects of the Acacia species by comparing microclimate characteristics and physiological traits of native plant seedlings at three sites: under the canopies of the each Acacia species and on bare land (open site). Although the sites were not replicated, the results indicated that adult trees of both Acacia species can facilitate native species, but that A. mangium has greater facilitating effects due to greater temperature buffering, radiation reduction, and nutrient amelioration. In response to facilitation, three species (Castanopsis hystrix, Michelia macclurei, and Manglietia glauca) with different shade-tolerant traits growing under Acacia canopies expressed distinct adaptations. For the three species, the chlorophyll fluorescence curves of rETR and ΔF/Fm′ were higher under A. auriculiformis and on the open site than under A. mangium. The maximum quantum yield in PSII(Fv/Fm) in diurnal changes of the three species showed that all the Fv/Fm values were between 0.70 and 0.84 and that the Fv/Fm values were mostly higher under A. mangium than on the open site or under A. auriculiformis. Total chlorophyll content and both chlorophyll a and b contents in the three species were higher under the Acacia species than on the open site, while chlorophyll a/b ratio was higher on the open site. In contrast, the carotenoid content in C. hystrix and M. macclurei was lower under the two Acacia species than on the open site, while the opposite was true for M. glauca. The results demonstrate that the adaptation of the understory species to abiotic environmental factors is not restricted to a single mechanism but apparently involves a group of interrelated, adaptive suites. And also these adaptations were species-specific and especially related to their shade tolerance.     

Management of fungal root‐rot pathogens in tropical Acacia mangium plantations

Acacia mangium is a fast‐growing tree species. It is mainly planted in large monocultures for pulpwood in South‐East Asia. Root rot has become the most economically damaging disease of this species with high tree mortality rates observed during second and third rotations. Two main types of root rots have been found in A. mangium, viz. brown root‐rot and red‐root disease caused by Phellinus spp. and Ganoderma spp., respectively. To assess the future management options for root rot of A. mangium, we review past and current disease‐management strategies for root rot in different temperate and tropical industrial tree crops. The efficacies of a wide range of silvicultural, chemical and biological options are detailed, and their potential utilization in managing root rot of A. mangium is discussed. We conclude that the current gaps in knowledge regarding identification, biology and disease epidemiology of the root‐rot pathogens will need to be addressed so that effective management options can be developed.     

Possibility of improvement in fundamental properties of wood of acacia hybrids by artificial hybridization

Growth, specific gravity, and wood fiber length of Acacia mangium, Acacia auriculiformis, artificial acacia hybrid clones, and combinations, which were planted in a trial forest in Bavi, Vietnam, in July 2001, were examined. The radial variations from pith to bark were investigated to clarify the effect of genetic factors on these traits. Superiority of hybrids over their parents ranged from 36.3% to 41.6% for diameter, from 20.0% to 25.3% for height, from 6.9% to 20.7% for specific gravity, and from 6.1% to 12.8% for wood fiber length. The hybrid possessed heterosis in diameter, height, specific gravity, and wood fiber length regardless of whether the female parent was A. mangium or A. auriculiformis. The profiles of wood fiber length and specific gravity in the radial direction were similar for all the trees investigated. Wood fiber length was initially 0.5–0.6 mm near the pith and then increased slowly, finally reaching 1.0–1.2 mm near the bark. The specific gravity of acacia increased from 0.49–0.58 near the pith to 0.63–0.74 near the bark. From a relative distance of 30% from the pith, the specific gravity increased slightly and seemed to be stable. The relations among tree diameter, specific gravity, and wood fiber length were fair and could be represented by positive linear regression formulas. Hybrids for which A. auriculiformis was the female parent and A. mangium was the male parent had a faster growth rate and longer wood fibers than the inverse hybrids. Part of this report was presented at the 6th Pacific Regional Wood Anatomy Conference, Kyoto, Japan, December 2005     

Ganoderma root-rot in an Acacia arboretum

Ganoderma lucidum caused root rot in an Acacia arboretum. Stumps colonized by the fungus were the source of infection. Among 18 species. Acacia albida, A. aneura, A. decurrens, A. murrayana and A. victoriae were the most susceptible to the disease whereas A. greggii and A. verek showed resistance.     

Bondability of tropical fast-growing tree species III: curing behavior of resorcinol formaldehyde resin adhesive at room temperature and effects of extractives of <Emphasis Type="Italic">Acacia mangium</Emphasis> wood on bonding

The effects of curing time at room temperature and methanol extracts from Acacia mangium on the curing behavior of resorcinol formaldehyde (RF) adhesive were examined by using the thermomechanical analysis spring method. For a specimen that was cured for 3 months at room temperature, the relative elasticity (E _r) curve did not change to a hard glass state from room temperature to 200°C and the adhesive had cured completely. The initial temperature of the reactive zone for chemical and mechanical changes was 15° and 25°C higher than that for the control when 10 and 15 parts by weight methanol extract was added to the liquid adhesive, respectively. It appears that the extractives of A. mangium in RF adhesive interferes with the chemical cure of the adhesive. It is suggested that a combination of curing time and sweeping by methanol on the laminae surface can improve the bonding performance of A. mangium laminates bonded with RF at room temperature.     

Growth and Mycorrhizal Dependency of Acacia mangium Willd. Inoculated with Three Vesicular Arbuscular Mycorrhizal Fungi in Lateritic Soil

Three VA-mycorrhizal fungi; Glomus occultum, Glomus aggregatum (local isolates) and G. mosseae (strain from Bangalore, India) were inoculated to assess their effect on growth of Acacia mangium in lateritic soil. All inoculations enhanced growth with respect to shoot height, root diameter, leaf area, chlorophyll content and biomass of A. mangium significantly compared to uninoculated control seedlings. G. occultum proved most efficient among the three. The mycorrhizal dependency factor indicated that the growth of A. mangium was 57% dependent on G. occultum, 47% on G. mosseae and 46% on Glomus aggregatum.     

Effect of pruning Acacia mangium on growth,form and heart rot

Small volumes of timber are now being produced from Acacia mangium plantations in Indonesia. These trees require pruning and thinning to increase the strength and appearance of the wood. However, cut surfaces from pruning are potential infection courts for the entry of decay-causing fungi like heart rot. This study investigated the effects of pruning on stem form and the incidence of heart rot in an 18-month-old plantation of Acacia mangium in South Sumatra. The objectives were to assess whether pruning is associated with an increase in the incidence of heart rot and whether form pruning compared to lift pruning reduced the incidence of heart rot and improved stem form. Form pruning removed 25% of leaf area by removing large branches and those subtending a narrow angle with the stem up to 3 m height, and lift pruning removed 25% of crown length from below. Trees in these treatments were singled before pruning. The third treatment, a control, was not singled and was used to assess base levels of heart rot.No significant difference in diameter increment between the two pruning treatments was found. There was strong evidence that form pruning was associated with better form 18 months after treatment. Trees in this treatment had a reduced number of branches >30 mm diameter and improved stem straightness (reduced kink). Lift pruning reduced average branch size but did not improve stem straightness. No heart rot was detected in any treatment.The results showed that form pruning is likely to have positive benefits on stem straightness and is likely to be effective to any selected pruning height. However a subsequent lift pruning is still considered a requirement. While wounds created from pruning and singling are assumed to have a large impact on the incidence of heart rot, this may not be an issue unless there is a sufficient source of fungi present in the environment to invade the wounds.     

Effect of four multipurpose tree species on soil amelioration during tree fallow in Central Togo

The effects of Cassia siamea, Albizia lebbek, Acacia auriculiformis, and Azadirachta indica on soil fertility have been studied on five-year-old fallows on Ferric Acrisols in Central Togo. Litter quality and soil fertility under the four species were significantly different. Topsoil pH increases significantly with increasing litter Ca levels. Cassia siamea and Azadirachta indica were superior in enriching the sandy-loamy topsoils with Calcium and in increasing soil pH. Under Acacia, which had the highest biomass production, litter accumulation appeared to be responsible for the low mineral soil Ca and P values. In addition, topsoil pH under Acacia was lower than under grass or bush fallow or the other species. Slow litter mineralization of Acacia auriculiformis was probably caused by the thick, leathery consistence and high tannin content of its litter. Due to its high biomass production supporting soil acidification pure Acacia auriculiformis stands seemed to be less favourable for improving soil fertility on planted fallows but more suited for firewood plantations and topsoil protection. The foliage as well as the litter and topsoil under Albizia showed narrow C/N- and C/P-ratios resulting in easily mineralizable organic matter. All tree species tested were superior to natural grass/herb fallow in building up surface soil fertility. However, differences with natural bush fallow were not significant.

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Résumé Au bout de cinq ans des differences fortement significative ont été trouvées quant aux caractères de la litière et de la fertilité des jachères arborées avec Cassia siamea, Albizia lebbek, Acacia auriculiformis et Azadirachta indica, respectivement. ll y a une corrélation positive entre le pH de l'horizon superficiel et la teneur en Ca dans la litière: l'enrichissement du sol sable-limoneux en Ca et le pH sont plus élevés sous Cassia siamea et Azadirachta indica que sous les autres espèces. Acacia se caractérise par la plus grande production en biomasse, donc une accumulation importante de litière sur le sol, ce qui entraîne les plus faibles teneurs en P et Ca dans l'horizon de surface. En plus, il semble qu'elle fait diminuer le pH parce que les valeurs trouvées sont inférieures à celles des parcelles témoin ou des autres espèces. La mineralisation retardée de la litière de Acacia auriculiformis depend probablement de la consistence des feuilles et du content élevé de tannine. Acacia est par consequent moins favorable à des jachères plantées mais plutôt efficace quant à la production du bois de feu et la protection du sol contre l'érosion. Vu les petits rapport C/N et C/P dans les feuilles, la litière et dans l'horizon superficiel d'Albizia, on peut supposer que sa matière organique soit plus facilement décomposable. Toutes les espèces d'arbre étudiées sont plus capables de lever la fertilité des sols que les herbes des parcelles témoin. La comparaison avec une jachère spontanée d'arbustes ne fait pas apparâitre d'effets significatifs.

     

Ecophysiology of Acacia species in wet–dry tropical plantations

Selected tropical Acacia species are used extensively for short-rotation plantation forestry in many parts of Asia and, to a limited degree, in Australia. We explored leaf-level photosynthetic activity and leaf water potential (Ψleaf) of three field-grown Acacia tree species (aged between 7 and 18 months) in contrasting wet–dry tropical plantations in southern Vietnam and northern Australia. Light-saturated photosynthetic rate (A1500) declined throughout the morning and early afternoon in the dry season; in the wet season, levels remained high and relatively constant throughout most of the day. Maximum daily A1500 at 09:00 ranged from 22.2 μmol?m?2?s?1 in the wet to 10.4 μmol?m?2?s?1 in the dry season. At both locations, trees were able to extract soil water such that pre-dawn leaf water potential (Ψpd) remained>?1.5?MPa even at the end of the dry season. Stomatal conductance to water vapour (gs) did not respond to decreasing Ψleaf during the wet season but was sensitive to changes in Ψleaf in the dry season. Species comparisons of the relationships between A1500 and Ψleaf revealed different strategies to balance carbon uptake and water loss in a wet–dry environment. Acacia crassicarpa and A. mangium regulated Ψleaf to a greater extent than the A. mangium×A. auriculiformis hybrid such that ?Ψleaf (determined as Ψpd?midday Ψleaf) was unaffected by season. This result suggests that the hydraulic regulation of tree water status varies amongst young tropical Acacia species. From a management perspective, for Acacia species that tend to strongly regulate water loss in environments with an extended dry season, overall productivity at the end of a rotation may be less than for species that prioritise carbon gain.     

Structural host responses of Acacia mangium and Eucalyptus pellita to artificial infection with the root rot pathogen,Ganoderma philippii

Structural host responses of young Acacia mangium and Eucalyptus pellita to infection with the root rot pathogen Ganoderma philippii were described. To our knowledge, this is the first report investigating the histology of root responses infected with G. philippii. The infected roots of A. mangium were characterized by the presence of a continuous multilayered mycelial sheath (~100–200 μm thick), fungal outgrowths and the production of a wound periderm. In contrast, roots of E. pellita were characterized by a mycelial sheath and fungal outgrowths and a wound periderm comprising of only one to four rows of cells.     

Wood properties of juvenile and mature heartwood in Robinia pseudoacacia L.

The aim of this study is to characterise the properties of juvenile and mature heartwood of black locust (Robinia pseudoacacia L.). Content, composition and the subcellular distribution of heartwood extractives were studied in 14 old-growth trees from forest sites in Germany and Hungary as well as in 16 younger trees of four clone types. Heartwood extractives (methanol and acetone extraction) were analysed by HPLC-chromatography. UV microspectrophotometry was used to topochemically localise the extractives in the cell walls. The natural durability of the juvenile and mature heartwood was analysed according to the European standard EN 350-1. Growth as well as chemical analyses showed that, based on extractives content, the formation of juvenile wood in black locust is restricted to the first 10–20 years of cambial growth. In mature heartwood, high contents of phenolic compounds and flavonoids were present, localised in high concentrations in the cell walls and cell lumen of axial parenchyma and vessels. In juvenile wood, the content of these extractives is significantly lower. Juvenile wood had a correspondingly lower resistance to decay by Coniophora puteana (brown rot fungus) and Coriolus versicolor (white rot fungus) than mature heartwood.     

A single dominant Ganoderma species is responsible for root rot of Acacia mangium and Eucalyptus in Sumatra

Ganoderma root rot is the most serious disease affecting commercially planted Acacia mangium in plantations in Indonesia. Numerous Ganoderma spp. have been recorded from diseased trees of this species and to a lesser extent Eucalyptus, causing confusion regarding the primary cause of the disease. In this study, a large collection of Ganoderma isolates were obtained from the roots of A. mangium showing early signs of root rot in disease centres in South Sumatra plantations. Isolates were also collected from Eucalyptus roots at Lake Toba in North Sumatra showing similar symptoms as well as from sporocarps connected to these samples. Phylogenetic analyses showed that a single Ganoderma sp., identified as G. philippii, is the major causal agent of Ganoderma root rot on A. mangium. Results from this study also showed that the isolates obtained for Eucalyptus trees in North Sumatra belong to G. philippii. Isolates from roots and connected fruiting bodies together with the morphology of the fruiting structures confirmed this identification. Symptoms associated with this pathogen are obvious and it should not be confused with other diseases. Other Ganoderma spp. found in disease centres are considered to be of minor importance and management strategies for root rot should be focused on G. philippii.     

Growth and yield prediction models for Acacia mangium grown in the plantations of the central region of Bangladesh

Acacia mangium is a very fast growing species belonging to the family Leguminosae that has been introduced in the plantations in Bangladesh for its faster growth and wide range of adaptability. The present study aimed at development of growth and yield prediction models for the species using simultaneous equation method. Models were selected for the species to estimate stand dominant height, stand diameter, stand basal area per hectare and total volume yield per hectare. Paired t-test, 45-degree line test, percent absolute deviation and biological principle of stand development were used for the validation of chosen models. The results suggest that the models derived were statistically and biologically acceptable and could be satisfactorily used for stands of Acacia mangium of ages 4–7 yrs based on a base age of 6 yr.