Symptoms and fungi associated with elm trees decline in Iran

Elm (Ulmus, Ulmaceae) is one of the most popular and important trees in urban and landscape areas in Iran. A severe decline of elm trees has recently been observed in some areas of Kerman and Shiraz cities. However, the identity of the causal agents has not yet been investigated. The purpose of this study, carried out in the years 2012–2014, was to isolate and identify fungal trunk pathogens associated with decline symptoms observed in elm trees. Samples were collected from trunks and branches of trees showing various disease symptoms and internal wood lesions. Fungal isolations were made from discolored or decayed wood tissue. In Kerman some elm trees were attacked by the beetle Aeolesthes sarta; therefore, samples were also collected from larvae and adults of beetles associated with trees showing wood damage. Fungal isolates were identified by morphological, cultural and molecular characteristics. Thirteen fungal species, Phaeoacremonium (P.) minimum, P. parasiticum, P. sicilianum, P. alvesii, P. fraxinopennsylvanicum, Spencermartinsia viticola, Dothiorella (Do.) sarmentorum, Neoscytalidium hyalinum, Diatrype (Di.) whitmanensis, Cosmospora viridescens, Phoma (Pho.) herbarum, Phellinus (Phe.) tuberculosus and Inonotus levis were identified. Phaeoacremonium parasiticum was the only species isolated from both larvae and adult beetles. Pathogenicity trials were performed on detached shoots of elm under greenhouse conditions. Dothiorella sarmentorum was the most virulent species based on the length of wood necrosis. This study is the first report of P. sicilianum, C. viridescens and Phe. tuberculosus in Iran. In addition, most of the isolated species are reported for the first time on elm trees in the world.     

Identification and characterization of bacterial strains associated with diseased oak trees in Northern Iran

Oak decline syndrome is characterized by periodic occurrences of decline and death of oaks over widespread areas. An outbreak of a new emerging disease on oak trees was reported in the Hyrcanian forest of Iran (Mazandaran and Golestan provinces) that showed stem bleeding and canker symptoms. Bacterial isolates were characterized through biochemical and physiological tests, protein electrophoresis, DNA fingerprinting (rep‐PCR, ERIC and BOX primers) and sequencing of 16S rRNA and MLSA (multilocus sequencing analysis) for housekeeping genes (gyrB, infB and atpD). A complex community of the genus Brenneria spp. (Brenneria goodwinii, Brenneria roseae subsp. roseae, Brenneria sp. and Brenneria nigrifluens) and a few isolates in the genus Gibbsiella were identified as major groups involved. Isolate differentiation was more accurate using concatenated partial gene sequences within the main groups. All bacterial isolates showed hypersensitivity reactions (HR) on Pelargonium leaves (Pelargonium × hortorum). Pathogenicity studies of different Brenneria and Gibbsiella strains revealed that they have potential to cause the disease in oak seedlings and devastating oak canker and stem bleeding symptoms in northern Iran. Due to the presence of several potentially pathogenic agent(s) associated with the oak decline, identification of the principal agent(s) is of major interest. To our knowledge, this is the first report of potentially pathogenic bacteria associated with oak bleeding and canker in Iran.     

Identification of transgenes from wood of genetically transformed poplar trees

We have extracted total DNA from different fractions of fresh wood as well as from cold-stored and air-dried wood harvested from transgenic aspen grown in the field. The highest amounts of DNA were obtained from bark/cambium tissue; the DNA quality, however, was poor. Best results in PCR and Southern blot analyses were obtained from DNA extracted from early wood. Using appropriate primer pairs, amplification products were obtained from both the foreign gene (transgene) and aspen genomic sequences. In Southern blot analyses transgene-specific hybridisation signals were obtained. This is the first report on the detection of foreign genes in wood sampled from genetically modified trees.     

Molecular identification of decay fungi in the wood of urban trees

Trees are valuable for urban areas, however, are also susceptible to wood rot fungi. For accurate and fast assessment of the severity and evolution of decay in standing trees, a molecular technique was used to identify the causal agents of wood rot. Fruit bodies of wood decay fungi were collected from infected trees in various stands in Germany. Thirty-six species were identified by traditional methods. The DNA of fruit bodies was extracted, ITS-rDNA amplified by PCR, and ITS regions sequenced. Wood samples from infected urban trees were collected, the entire DNA extracted from affected wood parts, and fungal ITS amplified and sequenced. Fungal species were identified by comparing sequence data with the fruit body data. The technique enables an accurate and rapid identification of causal rot fungi in urban trees.     

Canker disease of willow and poplar caused by Cryptosphaeria pullmanensis recorded in China

A new canker disease of Salix alba and Populus alba has been observed in Xinjiang, China. Black circular spots on dead branches and stems are the symptoms of the disease. Sixty‐seven isolates recovered from Salix matsudana, S. alba and Populus alba were identified as Cryptosphaeria pullmanensis based on morphological features and multigene phylogeny. Pathogenicity tests were performed on S. alba and P. alba stems using the C. pullmanensis isolates. Cankers on and Cryptosphaeria pullmanensis of C. pullmanensis from the stems fulfilled Koch's postulates and confirmed C. pullmanensis as the causal agent of the canker disease. C. pullmanensis is characterized by its yellow stromatic tissue surrounded by a black conceptacle with regularly arranged multiple locules sharing common walls and hyaline, allantoid, aseptate conidia (mean size 7.42 × 1.72 μm). This is the first report of C. pullmanensis causing Cryptosphaeria canker in China, and S. alba and P. alba are new host records for C. pullmanensis.     

Decay development in living sapwood of coniferous and deciduous trees inoculated with six wood decay fungi

Development of decay and/or discoloration was assessed in the functional sapwood of one coniferous and three deciduous trees after wounding and artificial inoculation with six wood decay fungi. Living stems of mature Douglas fir, beech, oak, and sycamore trees were wounded in spring 2002 and immediately inoculated with brown, white, and soft rot fungi. Extent of discoloration and decay, wood weight loss, and total phenols in the reaction zone (zone of active response at a dynamic interface between living sapwood and wood colonized by decay fungi) were assessed 16 and 28 months after inoculation.     

Identification and species-typing of wood rotting fungi using melting curve analysis

A method for identification and typing of wood rotting fungi using the melting temperature [T(m)] of DNA fragments coding rRNA (rDNA) was examined. The T(m)s of four DNA fragments, inter transcribed spacer (ITS) I, ITS II, and two partial fragments of 28S rDNA from each of 20 species of wood rotting fungi, were measured by melting curve analysis. The T(m) variation was large enough between species to enable identification based on the T(m) values. A pair of T(m)s of the ITS I region (between the primers ITS1 and ITS2) and the ITS II region (between the primers ITS3 and ITS4) had the highest resolution for identifying wood rotting fungi. To assess about the diversity of the T(m), intraspecific diversity of these DNA fragment sequences was evaluated using test strain sequences and data from the GenBank/EMBL/DDBJ biological database. The intraspecific diversity of T(m) was considered to be small because the nucleotide diversity of each fragment was small within the species.     

Phytophthora alticola and P. boodjera associated with decline of young Eucalyptus smithii trees in Uruguay

Eucalyptus production mainly destined to cellulose pulp production has expanded strongly in the last 30 years in Uruguay. Eucalyptus smithii has recently emerged as a promising species for cellulose pulp production. However, an average of 40% of young trees die during the first and second summer of post-planting. In this study, 32 Phytophthora isolates were obtained from 132 E. smithii young trees with root and collar rot symptoms, confirming the association of Phytophthora to E. smithii decline. Based on phylogenetic analysis of ITS, TUB2, cox1 and HSP90 gene regions and phenotypical characteristics, two species belonging to the genera Phytophthora clade 4 were identified, P. alticola (96%) and P. boodjera (4%). Tested isolates of both species significantly reduced both shoot and root dry weights of inoculated E. smithii seedlings compared to control plants. To our best knowledge, this is the first time that P. alticola and P. boodjera are recovered from young symptomatic E. smithii trees in commercial plantations as well as the first time these species are found in the Americas.     

Constraints on physiological function associated with branch architecture and wood density in tropical forest trees

This study examined how leaf and stem functional traits related to gas exchange and water balance scale with two potential proxies for tree hydraulic architecture: the leaf area:sapwood area ratio (A(L):A(S)) and wood density (rho(w)). We studied the upper crowns of individuals of 15 tropical forest tree species at two sites in Panama with contrasting moisture regimes and forest types. Transpiration and maximum photosynthetic electron transport rate (ETR(max)) per unit leaf area declined sharply with increasing A(L):A(S), as did the ratio of ETR(max) to leaf N content, an index of photosynthetic nitrogen-use efficiency. Midday leaf water potential, bulk leaf osmotic potential at zero turgor, branch xylem specific conductivity, leaf-specific conductivity and stem and leaf capacitance all declined with increasing rho(w). At the branch scale, A(L):A(S) and total leaf N content per unit sapwood area increased with rho(w), resulting in a 30% increase in ETR(max) per unit sapwood area with a doubling of rho(w). These compensatory adjustments in A(L):A(S), N allocation and potential photosynthetic capacity at the branch level were insufficient to completely offset the increased carbon costs of producing denser wood, and exacerbated the negative impact of increasing rho(w) on branch hydraulics and leaf water status. The suite of tree functional and architectural traits studied appeared to be constrained by the hydraulic and mechanical consequences of variation in rho(w).     

Determination of fiber length and juvenile and mature wood zones in Acer velutinum Boiss. trees grown in Iran

In our investigation we studied fiber lengths and the transition age from juvenile to mature wood in Acer velutinum Boiss. For this purpose, samples from three normal maple trees at a Noshahr site in northern Iran were selected. Disks were cut at breast height. Test samples were taken along a radial direction from the pith to the bark, accounting for every ring during a 48-year period. We used the Franklin method to distinguish between fibers of juvenile and mature wood. The results show that the fiber length increased along the radial direction from the pith to the bark. The transition age between juvenile and mature wood was determined at the 14th annual ring from the pith.     

Brenneria spp. and Rahnella victoriana associated with acute oak decline symptoms on oak and hornbeam in Iran

Decline diseases of forest trees are complex syndromes not attributable to single causal factors. In Iran, symptoms of decline disease have been observed in a number of native forest species including Quercus castaneifolia (chestnut‐leaved oak), Q. brantii (Persian oak) and Carpinus betulus (hornbeam). The symptoms are prevalent in the northern forests and the Zagros mountain forests. There are parallels between the disease in Iran and acute oak decline (AOD) reported in the UK, specifically the presence of weeping cankers, which have been attributed to a polybacterial complex wherein Brenneria goodwinii is considered a key necrogen. Based on the AOD symptomatology, and as a first step towards discovering potential causal agents of the stem weeping symptoms of affected trees in Iran, necrotic tissues were tested primarily for the presence of B. goodwinii. Symptomatic Q. castaneifolia and C. betulus from the Mazandaran Province and symptomatic Q. brantii from Kohgiluyeh and Boyerahmad Province were sampled. Isolation and culture on a selective medium yielded uniform bacterial colonies. Isolates were characterized using phenotypic and genotypic (DNA sequencing) tests. The isolates were phenotypically identical to members of Pectobacteriaceae and Yersiniaceae, specifically Brenneria and Rahnella spp. The nucleotide sequences of the 16S rRNA and housekeeping genes gyrB, infB and atpD (MLSA) amplified via PCR demonstrated that the isolates from the trees in Iran were indeed B. goodwinii, B. roseae subsp. roseae, Rahnella victoriana and an unknown species of Brenneria. Most bacteria isolated from non‐symptomatic trees were Gram‐positive, and Pseudomonas spp. were dominant, but bacterial species isolated from the diseased trees were not detected in healthy trees. Hypersensitivity response tests were positive, but inoculation on saplings was more variable with internal necrosis developing only once in the test period. Therefore, further testing is required. This is the first report of the incidence of B. goodwinii, B. roseae subsp. roseae, R. victoriana and Brenneria sp. associated with acute oak decline‐like symptoms on Q. castaneifolia, Q. brantii and C. betulus across the western forests of Iran and in the world.     

Cement-bonded particleboard with a mixture of wheat straw and poplar wood

We investigated the hydration behavior and some physical/mechanical properties of cement-bonded particleboard (CBPB) containing particles of wheat straw and poplar wood at various usage ratios and bonded with Portland cement mixed with different levels of inorganic additives. We determined the setting time and compression strength of cement pastes containing different additives and particles, and studied the effects of these additives and particles on thickness swelling, internal bond strength and modulus of rupture of CBPB by using RSM (Response Surface Methodology). The mathematical model equations (second-order response functions) were derived to optimize properties of CBPB by computer simulation programming. Predicted values were in agreement with experimental values (R2 values of 0.93, 0.96 and 0.96 for TS, IB and MOR, respectively). RSM can be efficiently applied to model panel properties. The variables can affect the properties of panels. The cement composites with bending strength > 12.5 MPa and internal bond strength > 0.28 MPa can be made by using wheat straw as a reinforcing material. Straw particle usage up to 11.5% in the mixture satisfies the minimum requirements of International Standard, EN 312 (2003) for IB and MOR. The dose of 4.95% calcium chloride, by weight of cement, can improve mechanical properties of the panels at the minimum requirement of EN 312. By increasing straw content from 0 to 30%, TS was reduced by increasing straw particle usage up to 1.5% and with 5.54% calcium chloride in the mixture, TS satisfied the EN 312 standard.     

Identification of endophytic fungi of grapevine with emphasis on the causal agents of grapevine trunk disease in the vineyards of Zanjan Province in Iran

Trunk disease is a major problem on grapevine in Zanjan province, causing serious decline, despite which its aetiology remains unknown. The purpose of this study was to investigate factors involved in grapevine decline in vineyards of Zanjan province. Samples were collected from twigs and branches of grapevines in the region between October and November 2018. Fungal isolates were identified based on morphological characteristics and ITS-rDNA sequence data for selected isolates. The frequency and diversity of the fungal community recovered from grapevines in Darreh Sejin in Zanjan province were higher than in other regions. A total of 112 fungal isolates comprising 22 species were recovered. Phaeoacremonium minimum, Microsphaeropsis olivacea and Kalmusia variispora were identified as the dominant species in the region examined and could be considered the main trunk pathogens of grapevines in Zanjan region. In inoculation tests, M. olivacea was proved to be pathogenic on grapevine for the first time in this study.     

Estimating the costs of one hectare of poplar planting and supplying wood required for producing various types of paper in Iran

In Iran, due to abundant restrictions on harvesting wood from northern forests by implementing the preservation project and also lack of possibility for sufficient wood production, development of the area of planting poplar is quite inevitable. Poplar wood properties have special importance to produce many wood production, particularly pulp and paper. Paper factories are the major consumers of poplar wood at the global level and this is because of unique morphological, physical, mechanical and technological properties of poplar wood. Therefore, regarding the importance of using this species in making various printing and writing paper, packaging or carton, cardboard and newsprint, in this study, costs of poplar production in one hectare including planting and harvesting were examined and determined. Then, based on conversion coefficients of FAO, required round wood, productivity and the cost of poplar wood were calculated for the producing various kinds of paper. The results indicate that carton and cardboard paper or packaging allocate the lowest cost and highest return, while printing and writing paper had highest cost and lowest return in terms of poplar wood supply needed for paper production.     

杨树新无性系木材性质的变异研究

The wood basic density, cellulose content and fiber form were investigated for all sample trees at breast height (1.3m) in seven poplar clones, and at 0 (butt), 5.6, 9.6, 13.6, 17.6, 19.6 and 21.6 m for clone Nanlin-95 and Nanlin-895, respectively,for providing information on variation patterns of wood density, fiber characteristics and holocellulose content within trees and among clones. The results showed that significant variations about wood density, cellulose content, fiber diameter and the ratio of fiber length to diameter existed among poplar clones examined. Variance analysis indicated that there were significant differences in wood basic density, fiber length, fiber diameter and cellulose content among the growth rings, which had an increasing tendency along the direction from pith to bark. The significant differences also existed in wood basic density, fiber length and fiber diameter at different tree height. The mean wood basic density had a general increase trend with increasing height of trees and the lowest was found at the base, while fiber length and fiber diameter had a general decline pattern with increasing height of trees and the biggest value was observed at the height of 5.6 m. Regression analysis indicated that the relationship between examined wood properties and growth ring number (cambial age), and the relationship between examined wood properties and tree height can be described by polynomial functions.     

杨柳树在长春市街路广场园林生态系统中的地位研究

利用样地调查方法,对长春市街路与广场的树木结构进行分析,结果表明：街路与广场共有杨柳树172617株,杨树的平均胸径为19．8cm,平均树高8．5m;柳树的平均胸径为20．0cm,平均树高7．5m。杨柳树的总生物量为83805．5t,总叶面积为14851196．9m^2。杨柳树每年可以制造干物质4629．2t,吸收二氧化碳6786．6t,放出氧气4939．4t,吸滞灰尘5755．4t,吸收二氧化硫44．1t。     

Effects of oleoresins and monoterpenes on in vitro growth of fungi associated with pine decline in the Southern United States

As a means of exploring pine resistance to root disease and declines, the effects of host plant secondary metabolites on the growth of root colonizing fungi associated with three diseases/declines of southern pines – loblolly pine decline, littleleaf disease and annosum root rot were tested. The associated fungi –Leptographium huntii, L. serpens, L. terebrantis, L. procerum, Heterobasidion annosum and Phytophthora cinnamomi– were grown in saturated atmospheres or in direct contact with, pure monoterpenes and crude oleoresin collected from the four southern pines (Pinus taeda, P. eschinata, P. palustris and P. elliotti) for 7 day. Fungal growth was measured at 3, 5 and 7 day. Root‐infecting fungi differed significantly in sensitivity to crude oleoresin and pure monoterpenes. All fungi tested were inhibited, to some extent, by the resins tested. H. annosum and P. cinnamomi were strongly inhibited by all the monoterpenes tested. The ophiostomatoid fungi were significantly less affected by the compounds tested. L. huntii and L. serpens were less inhibited by monoterpenes than either L. terebrantis or L. procerum. These fungal growth studies show that the kind and amount of secondary metabolite produced by the host plant have a profound effect on tree pathogens. Alterations of tree physiology may have implications for defenses against tree pathogens as well as to the ecology and management of forest ecosystems. Difference in incidence of root disease observed in the field may be explained by the ability of the fungus to tolerate these host defense mechanisms.     

Identification and distribution of Armillaria species associated with an oak decline event in the Arkansas Ozarks

Forests in the Ozark Mountains of northern Arkansas recently experienced a widespread oak decline event. Armillaria, a root rot fungus, has been associated with other oak decline events and may have been an important contributing factor to tree mortality in this event. Although Armillaria has been identified from the Ozark Mountains in Missouri, it has never been investigated in the Arkansas Ozarks. Molecular diagnostic techniques were used in this study to identify species of Armillaria present on roots removed from dead trees of two common oak species, northern red oak, Quercus rubra L., and white oak, Q. alba L., from three geographic areas and on three topographic positions – ridges, south‐ and west‐facing benches. Armillaria(A. mellea, A. gallica or A. tabescens) was identified from 31% of root samples taken from 102 trees in seven of nine sample plots. Armillaria mellea, occurred most often (20 samples, both oak species on seven plots) followed by A. gallica (10 samples, northern red oak only on four plots), and A. tabescens occurred twice (on northern red oak in a single plot). Thus, all three Armillaria species occurred on northern red oaks while A. mellea was the only species recovered from white oaks. Results varied by topographic position with samples from tree roots on ridges having the fewest positive identifications, one of 29. West‐facing benches had the highest positive samples with 20 of 41 testing positive and trees on south‐facing benches were intermediate with 11 of 32 samples from infected trees. This study documents the occurrence of three species of Armillaria in the Arkansas Ozarks and their association with oak mortality resulting from an oak decline event coupled with a red oak borer, Enaphalodes rufulus, outbreak. Further, it documents some potential variation in host/pathogen combinations and forest site conditions.     

Efficacy of radio frequency treatment and its potential for control of sapstain and wood decay fungi on red oak,poplar, and southern yellow pine wood species

The effectiveness of radio frequency (RF) treatment in the control of wood decay fungi (Gloeophyllum trabeum, Ganoderma lucidum, and Irpex lacteus) and sapstain fungus (Ceratocystis fimbriata) in red oak (Quercus spp.), poplar (Populus alba), and southern yellow pine (Pinus spp.) was evaluated in the laboratory as an alternative to methyl bromide (MB) treatment. Wood samples (15.5 x 10 x 10 cm) were inoculated with fungi from a 7-day culture by dipping them to a depth of one face deep (2 cm) into inoculum and incubating them at 25°C for 14 days. Identical wood samples were left uninoculated as controls. Subsequent to incubation, the wood blocks were exposed to RF radiation in an industrial 40-kW dielectric oven at temperatures between 60° and 70°C for 2 min. The test fungi were recovered and reisolated from all of the control wood blocks but not from RF-treated wood blocks. RF treatment resulted in complete inhibition of the fungus in 98%-100% of the wood samples. Moisture content loss (≥1%) was noted after wood had been exposed to RF treatment. Moisture content may be an important factor to consider with RF treatments. RF treatment can, therefore, potentially provide an effective and rapid quarantine treatment as an alternative to MB fumigation for certain pathogen-wood combinations. This article reports the results of research only. Mention of a product does not constitute an endorsement or recommendation by USDA for its use.     

First detection of Neoscytalidium dimidiatum associated with canker disease in Egyptian Ficus trees

In September 2013, a canker disease of Ficus nitida and F. benjamina was reported for the first time in Assiut governorate, Egypt. Infected samples were collected from various locations. Pure cultures of a fungus were isolated on potato dextrose agar at 25°C from diseased plants. Morphological investigation and DNA sequencing showed that the causal agent was Neoscytalidium dimidiatum. A pathogenicity test conducted using 2‐year‐old plants of each host gave 70%–80% infection, and the pathogen was reisolated from the inoculated plants. A pure culture of N. dimidiatum was deposited in the culture collection of the Assiut University Mycological Centre (AUMC) under the code AUMC 9293 and the ITS sequence was placed in NCBI under accession number KX985929 .