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1.
We investigated the cellular responses of stem tissues of mature Scots pine (Pinus sylvestris L.) trees to inoculations with two fungal pathogens. The bark beetle vectored fungus, Leptographium wingfieldii Morelet, induced longer lesions in the bark, stronger swelling of polyphenolic parenchyma cells, more polyphenol accumulation and increased ray parenchyma activity compared with the root rot fungus, Heterobasidion annosum (Fr.) Bref., or mechanical wounding. Axial resin ducts in the xylem are a general feature of the preformed defenses of Scots pine, but there was no clear induction of additional traumatic axial resin ducts in response to wounding or fungal infection. The anatomical responses of Scots pine to pathogen infection were localized to the infection site and were attenuated away from bark lesions. The responses observed in Scots pine were compared with published studies on Norway spruce (Picea abies (L.) Karst.) for which anatomically based defense responses have been well characterized. 相似文献
2.
Tree defense against bark beetles (Curculionidae: Scolytinae) and their associated fungi generally comprises some combination of constitutive (primary) and induced (secondary) defenses. In pines, the primary constitutive defense against bark beetles consists of preformed resin stored in resin ducts. Induced defenses at the wound site (point of beetle entry) in pines may consist of an increase in resin flow and necrotic lesion formation. The quantity and quality of both induced and constitutive defenses can vary by species and season. The inducible defense response in ponderosa pine is not well understood. Our study examined the inducible defense response in ponderosa pine using traumatic mechanical wounding, and wounding with and without fungal inoculations with two different bark beetle-associated fungi (Ophiostoma minus and Grosmannia clavigera). Resin flow did not significantly increase in response to any treatment. In addition, necrotic lesion formation on the bole after fungal inoculation was minimal. Stand thinning, which has been shown to increase water availability, had no, or inconsistent, effects on inducible tree defense. Our results suggest that ponderosa pine bole defense against bark beetles and their associated fungi is primarily constitutive and not induced. 相似文献
3.
- Fungal species stimulating tree defenses are generally not those that grow the best in the sapwood.
- We argue that beetle development in the phloem, fungal invasion of the sapwood and phloem, and tree death, occur after tree defenses are exhausted, and that any fungus present in the beetle gallery could thus potentially invade the sapwood after defense exhaustion.
- any beetle species would be helped in its establishment in a given tree species by developing an association, even loosely, with a fungus species belonging to the Ophiostomatoid flora of that tree species;
- the necessity of a considerably low level of tree resistance for fungus extension into the tree is the selection pressure that has led fungi to develop their intrinsic ability to stimulate tree defenses, through their ability to grow into the phloem. This association can be completed by antagonistic fungal species controlling extension of the previous fungal species in the tree tissues;
- Beetle species using the strategy of overcoming tree resistance are associated with a fungal complex, of which species could assume three roles regarding relationships between beetles and trees: 1- to stimulate tree defenses in the phloem and superficial sapwood, 2- to grow into the sapwood after tree resistance is overcome, and 3- to control phloem extension of the first other two categories. Bringing nutrients to the beetle progeny can be a fourth role.
4.
Importance of current photosynthate in the regulation of tree defense against the southern pine beetle (SPB),Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae) was investigated in loblolly pine,Pinus taeda L. Downward translocation of carbohydrate was blocked by removing a ring of bark (girdle) at 3.5 m above ground. Beetle colonization success and tree defensive responses measured as resin flow and induced lesion formation to inoculations with the beetle-associated fungus,Ophiostoma minus (Hedge.) H. and P. Sydow., were assessed above and below girdles. We hypothesized that a decrease in a available carbohydrate would lead to a decrease in tree defense and an increase in SPB colonization success below girdles. At 2 weeks, post-girdling carbohydrates were already reduced by 50% below girdles, but no significant differences in beetle colonization success or defensive responses were measured. At 8 weeks, post-girdling starch was reduced by 93%, sucrose by 44% and resin flow by 44% below girdles. Southern pine beetle adults were more successful in colonizing areas below than above girdles. However, no significant differences were detected in the size of the lesions that formed in response to inoculated fungi. This suggests that the size of the induced lesion may not be a reliable indicator of tree resistance to bark beetle attack as previously believed, and that lesion development is not entirely dependent on available carbohydrate or related to tree defense against beetles. Cambial growth was reduced below girdles with no latewood formed below and 25 rows of latewood formed above girdles. Latewood contains much higher densities of resin ducts than earlywood. This may explain why resin flow was lower and beetles were more successful in colonizing areas of the tree below girdles. Therefore, tree defense against bark beetles may be more complex than a simple supply-and-demand relationship for carbohydrate, and changes in source-sink relationships, as influenced by the environment, may be more important than supply. 相似文献
5.
A number of various species of blue-stain fungi were isolated fromTomicus piniperda adults at various stages of development, as well as from the galleries, pupal chambers and sapwood underneath galleries on
Japanese red pine. This study was an attempt to identify the species, composition of blue-stain fungi associated withT. piniperda, the frequency of occurrence of the fungi, and their role in the sapwood-staining of Japanese red pine in Tsukuba City, central
Japan. Among the seven species of blue-stain fungi isolated, an undescribed species ofOphiostoma together withO. minus were the dominant species and closely associated withT. piniperda. These two species occurred on newly emerging adults more frequently than the overwintered adults.Hormonema dematioides was also associated with the beetle, however, its frequency of occurrence from the emerged new adults was very low. Although
the two other species,O. ips andGraphium sp. were also isolated from emerged beetles, the frequency of these fungi from gallery systems suggested that they were accidentally
carried byT. piniperda. Leptographium wingfieldii, known to be associated with the beetle in Europe, was also isolated at a very low frequency and the fungus seemed not to
be closely associated with the beetle.Ophiostoma sp. andO. minus appear to be the most important causes of blue-stain of Japanese red pine sapwood after infestation byT. piniperda. 相似文献
6.
Oleoresin flow is an important factor in the resistance of pines to attack by southern pine beetle, Dendroctonus frontalis Zimm., and its associated fungi. Abiotic factors, such as nutrient supply and water relations, have the potential to modify this plant-insect-fungus interaction; however, little is known of the effects of inoculation with beetle-associated fungi on oleoresin flow. We observed that constitutive and induced resin yield in loblolly pine, Pinus taeda L., were affected by either fungal inoculation (with the southern pine beetle-associated fungus Ophiostoma minus (Hedgcock) H. & P. Sydow) or silvicultural treatment. The effects of mass wounding (400 wounds m(-2)) and mass wounding and inoculation with O. minus were assessed by comparison with untreated (control) trees. The treatments were applied to trees in a 2 x 2 factorial combination of fertilizer and irrigation treatments. Fertilization did not significantly affect constitutive resin yield. Even as long as 105 days post-treatment, however, mass-inoculated trees produced higher induced resin yields than control or wounded-only trees, indicating a localized induced response to fungal inoculation. We noted no systemic induction of host defenses against fungal colonization. Although beetles attacking previously attacked trees face a greater resinous response from their host than beetles attacking trees that had not been previously attacked, the effect of an earlier attack may not last more than one flight season. Despite mass inoculations, O. minus did not kill the host trees, suggesting that this fungus is not a virulent plant pathogen. 相似文献
7.
Metka Novak Andreja Urbanek Krajnc Ljerka Lah Neja Zupanec Nada Kraševec Mitja Križman Joerg Bohlmann Radovan Komel 《European Journal of Forest Research》2014,133(4):573-583
Among the most devastating pests of Norway spruce (Picea abies) are the European spruce bark beetle (Ips typographus) and the associated pathogenic blue-stain fungus Ceratocystis polonica. Following attack and colonization, the beetle and the fungus must cope with induced host chemical defenses, such as monoterpenes that are generally thought to be toxic to both symbionts. The goal of this study was to better understand the response of Norway spruce following C. polonica inoculation at low density that does not overwhelm the tree and to identify monoterpenes mobilized toward the fungus. We inoculated healthy mature trees and monitored monoterpene profiles 2, 3, and 5 months post-inoculation. We also exposed three different C. polonica strains to the most abundant or significantly up-regulated monoterpenes to determine differences in monoterpene toxicity and resistance among strains. Total monoterpene levels, including limonene, were increased at 2 and 3 months after inoculation and had dropped after 5 months. In in vitro assays, all monoterpenes were inhibitory to C. polonica. Limonene and β-pinene were the most potent inhibitors of fungal growth. The extent of inhibition varied between the three strains tested. These results showed a defense response of Norway spruce to C. polonica, in which limonene may play a critical role in inhibiting the spread of the fungus. We also showed that differences between strains of C. polonica must be taken into account when assessing the role of the fungus in this bark beetle–symbiont system. 相似文献
8.
Production of free and conjugated polyamines by two ectomycorrhizal fungi, Pisolithus tinctorius (Pers.) Coker and Couch and Paxillus involutus (Batsch) Fr., was studied in vitro. Spermidine was the main polyamine in the mycelium of both fungi. Paxillus involutus also produced large amounts of the diamine putrescine, whereas Pisolithus tinctorius contained traces of the diamine cadaverine and released into the culture medium an unknown compound probably related to cadaverine or N-methylputrescine. Both fungi accelerated adventitious root formation and increased subsequent root growth of Scots pine (Pinus sylvestris L.) hypocotyl cuttings in vitro. Exogenous cadaverine enhanced rooting caused by Pisolithus tinctorius and also promoted mycorrhiza formation by the fungus. Putrescine and Paxillus involutus had a synergistic effect on root initiation, but not on subsequent root growth. We conclude that specific diamines may be involved in the interaction between ectomycorrhizal fungi and adventitious root formation in Scots pine, and that the effects of specific exogenous polyamines are dependent on the fungal strain and its ability to produce these compounds. The finding that Paxillus involutus enhanced rooting and root growth without mycorrhiza formation indicates that fungal-induced rooting is not necessarily related to visible mycorrhiza formation. 相似文献
9.
When conifers such as Picea abies Karst. (Norway spruce) are attacked by insects or pathogens, they often respond by producing increased quantities of terpenoid oleoresin. This response can be mimicked in young P. abies seedlings by treatment with methyl jasmonate (MJ). In this study, we determined the effects of MJ on terpenoids and other chemical defenses of mature P. abies, and investigated whether this treatment protected trees against attack by the blue-stain fungus Ceratocystis polonica (Siem.) C. Moreau, the most important fungal associate of the spruce bark beetle Ips typographus L. Methyl jasmonate treatment induced the formation of traumatic resin ducts in the developing xylem, enhanced resin flow and stimulated increased accumulation of monoterpenes, sesquiterpenes and diterpene resin acids. However, only minor changes were detected in terpene composition in response to MJ treatment and no changes in soluble phenolic concentration were measured. There was much variability in the timing and degree of response to MJ among clones. The observed chemical and anatomical changes in response to MJ treatment were correlated with increased resistance to C. polonica, suggesting that terpenoid oleoresin may function in defense against this pathogen. 相似文献
10.
A quantitative multiplex real-time polymerase chain reaction (PCR) procedure was developed to assess the extent of Heterobasidion annosum (Fr.) Bref. growth in Sitka spruce (Picea sitchensis (Bong.) Carr.) bark and wood and to determine correlations between lesion length and fungal colonization. Based on lesion length and real-time PCR, the responses of four 3-year-old Sitka spruce clones to inoculation with H. annosum were characterized as showing either resistance or susceptibility to the pathogen. In susceptible clones, the extent of bark colonization did not differ from the visible length of the bark lesion, whereas lesions were longer than the extent of fungal colonization in resistant clones. The resistant clones contained considerably less fungal DNA than the susceptible clones, relative to the amount of host DNA in both the bark and the wood, indicating less resistance and more host cell death in the susceptible clones following inoculation. In both resistant and susceptible clones, fungal colonization in the wood extended beyond the visible necrotic lesion in the bark, indicating that host defense responses are weaker in wood than in bark. The spread of the pathogen in both bark and wood was less in the resistant clones than in the susceptible clones, indicating that defenses in both bark and wood of the resistant clones were superior to those in the susceptible clones. 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(6):497-506
The pine shoot beetle, Tomicus piniperda, is a secondary colonizer of pines and other conifers. Although it is necessary to understand interactions of this insect with other organisms, few studies have focused on its fungal associates. This study focused on the effect of geographical distance on the occurrence of fungi carried by the beetle. Adult beetles were collected from Scots pine (Pinus sylvestris) in North (Rovaniemi) and South (Hyytiälä) Finland. The mycota was isolated and identified using a combination of morphological and molecular data. The results revealed a great diversity of fungal taxa isolated from T. piniperda, with a total of 3073 isolates representing 20 taxonomic units. The most frequently isolated fungi in the bark beetles from North Finland were Beauveria bassiana, Kuraishia sp., whereas Penicillium velutinum was mostly observed in the insects from South Finland. Ophiostoma canum and Ophiostoma minus were also isolated from the beetles from both North and South Finland. The number of fungi isolates per insect was 2.58 in the North and 3.74 in the South, respectively. Significant differences were found between South and North Finland in fungal taxa isolated from the beetles. The highest richness and diversity of the fungal taxa was observed in the South. However, the overall fungal diversity index analysis revealed that the mycobiota was under-sampled which suggests that a proportion of the fungal species may have remained undetected. 相似文献
12.
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. 相似文献
13.
We examined drought-induced changes in susceptibility of potted Scots pine (Pinus sylvestris L.) trees to a bark-beetle associated fungus (Leptographium wingfieldii Morelet, from the bark beetle Tomicus piniperda L.). Five-year-old field-grown trees were transplanted to 50-l pots and grown for 1 year before the treatments were applied. Trees in the drought treatment were subjected to several successive, 3-week-long drought cycles, with predawn water potential dropping below -2 MPa at peak drought intensity. The experimental drought cycles were more severe than the natural drought episodes usually recorded in Scots pine stands. Trees were then mass-inoculated with L. wingfieldii at a density close to the critical threshold density of inoculations (400 m(-2)) above which tree resistance is overcome. Inoculation of well-watered trees resulted in induced reaction zones around the inoculation points and very limited damage (resinosis) in the sapwood. Drought alone had no long-lasting consequences on tree water relations, except for a decrease in hydraulic conductance in the youngest segments of the main stem. However, the combination of mass-inoculation and drought stress after inoculation resulted in a dramatic loss of stem hydraulic conductivity that was paralleled by conspicuous damage to the sapwood (resinosis, drying and blue staining). There was a close correlation between amount of visible sapwood damage and loss of hydraulic conductivity. The intensity of induced reactions in the phloem was unaffected by drought stress. We conclude that tree defence against L. wingfieldii is decreased during severe drought stress, resulting in changes in the spread and action of the fungus in the sapwood but not in the phloem. 相似文献
14.
Extensive ponderosa pine (Pinus ponderosa Dougl. ex Laws.) mortality associated with a widespread severe drought and increased bark beetle (Coleoptera: Curculionidae, Scolytinae) populations occurred in Arizona from 2001 to 2004. A complex of Ips beetles including: the Arizona fivespined ips, Ips lecontei Swaine, the pine engraver beetle, Ips pini (Say), Ips calligraphus (Germar), Ips latidens (LeConte), Ips knausi Swaine and Ips integer (Eichhoff) were the primary bark beetle species associated with ponderosa pine mortality. In this study we examine stand conditions and physiographic factors associated with bark beetle-caused tree mortality in ponderosa pine forests across five National Forests in Arizona. A total of 633 fixed-radius plots were established across five National Forests in Arizona: Apache-Sitgreaves, Coconino, Kaibab, Prescott, and Tonto. Prior to the bark beetle outbreak, plots with mortality had higher tree and stocking compared with plots without pine mortality. Logistic regression modeling found that probability of ponderosa pine mortality caused by bark beetles was positively correlated with tree density and inversely related with elevation and tree diameter. Given the large geographical extent of this study resulting logistic models to estimate the likelihood of bark beetle attack should have wide applicability across similar ponderosa pine forests across the Southwest. This is particularly true of a model driven by tree density and elevation constructed by combining all forests. Tree mortality resulted in significant reductions in basal area, tree density, stand density index, and mean tree diameter for ponderosa pine and for all species combined in these forests. Most of the observed pine mortality was in the 10–35 cm diameter class, which comprise much of the increase in tree density over the past century as a result of fire suppression and grazing practices. Ecological implications of tree mortality are discussed. 相似文献
15.
16.
To study the effect of chemical pretreatment on conifer resistance, 13-year-old Norway spruce (Picea abies (L.) Karst.) trees were treated with methyl jasmonate (MJ) or oxalic acid (OxA) on the outer bark and inoculated with the pathogenic blue-stain fungus Ceratocystis polonica (Siem.) C. Moreau 4 weeks later. Both chemicals significantly reduced symptoms of fungal infection, but MJ was more effective than OxA (51 versus 18% reduction in length of necrotic lesions in the phloem relative to untreated control trees). Anatomical examination of treated stem tissues showed that MJ induced extensive formation of traumatic resin ducts in the xylem and extra polyphenolic parenchyma (PP) cells in the secondary phloem between the cambium and the regular annual PP cell layer. No traumatic resin ducts were formed after treatment with OxA, and the coverage of extra PP cells in OxA-treated tissues was not significantly higher than in the controls. The anatomically based defense reactions induced by MJ were similar to the reactions observed after pathogen infection, mechanical wounding and bark beetle attack. Neither MJ nor OxA had apparent phytotoxic effects on Norway spruce at the concentrations used, with needle and stem tissues of all trees appearing normal without visible symptoms of toxicity. However, trees treated with MJ had 30% less radial sapwood growth than control trees. In conclusion, MJ treatment of Norway spruce appears to have practical potential as a tool for increasing plant resistance to fungal infection, but with a modest reduction in sapwood growth. 相似文献
17.
We made inoculations to determine the comparative virulence of blue-stain fungi isolated from Japanese red pine (Pinus densiflora Sieb. & Zucc.). Based on the symptoms caused by each fungus, the most virulent fungus was Leptographium wingfieldii. Also, Ophiostoma minus was relatively virulent while lesions induced by some species did not differ from those in the control treatment. Based on
the results, we concluded that the pathogenicity of the blue-stain fungi varied widely, and thus their impact on the host
most likely varies too.
Received: June 7, 2002 / Accepted: October 4, 2002
Present address: JST Domestic Research Fellow, Forest Pathology Laboratory, Tohoku Research Center, Forestry and Forest Products
Research Institute, 92-25 Nabeyashiki, Shimo-Kuriyagawa, Morioka 020-0123, Japan Tel +81-19-648-3961; Fax +81-19-641-6747
e-mail: H_masu@hotmail.com
Acknowledgments We thank Drs. Ohtaka and Usuki, Plant Pathology and Mycology Laboratory, Institute of Agriculture and Forestry, University
of Tsukuba, for technical assistance. Contribution No. 174, Plant Pathology and Mycology Laboratory, Institute of Agriculture
and Forestry, University of Tsukuba.
Correspondence to:H. Masuya 相似文献
18.
Roger F. Walker Shannon L. Swim Dale W. Johnson Watkins W. Miller Robert M. Fecko 《Journal of Sustainable Forestry》2013,32(7):627-676
Forest thinnings implemented with cut-to-length and whole-tree harvesting systems followed by underburning were evaluated for their effects on bark beetle prevalence in pure, uneven-aged Jeffrey pine (Pinus jeffreyi Grev. & Balf.) interspersed with isolated California white fir (Abies concolor var. lowiana [Gord.] Lemm.). Based on pitch tube counts in a stand with a moderate bark beetle population in its pine component, the Jeffrey pine beetle (Dendroctonus jeffreyi Hopkins) generally preferred larger trees before treatment implementation, but after exhibiting mixed pretreatment tendencies concerning stand density demonstrated a posttreatment proclivity toward higher density. Cut-to-length thinning followed by underburning increased the pine beetle population while whole-tree thinning unaccompanied by burning reduced it. Tree mortality was induced by the bark beetle infestation but was not its sole cause. Pitch tube abundance on white fir far exceeded that on Jeffrey pine, and the greatest influence on the fir engraver (Scolytus ventralis LeConte) population was the prevalence of its host tree. The responses presented herein to these thinning and burning practices, which are being increasingly utilized in forest restoration efforts in the western USA, provide natural resource managers insight into potential forest health outcomes when implemented in Jeffrey pine and similar dry site forest types. 相似文献
19.
小长喙霉 ( Ophiostoma minus Hedgc.)于 190 6年作为新种定名为 Ceratostomella minorHedgc,1981年更名为 Ophiostoma minus Hedgc.,此后一直沿用至今 [1]。小长喙霉以小蠹虫( Tomicus spp.)为媒介 ,通过小蠹虫对树木的蛀害 ,被携带进入到寄主植物组织内 ,进行自身生命过程并危害寄主植物[2 ] ,故也被称为小蠹虫伴生真菌 [3,4] 。该菌的寄主植物主要是松树( Pinus spp.) [4] ,它在协助小蠹虫蛀害松树树木中扮演着重要的角色 [3,4]。80年代以来 ,纵坑切梢小蠹 ( Tomicus piniperda Linnaeus)在云南 8个地州大面积暴发成灾 ,10余万 hm2 … 相似文献
20.
Prescribed fire is an important tool in the management of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests, yet effects on bark beetle (Coleoptera: Curculionidae, Scolytinae) activity and tree mortality are poorly understood in the southwestern U.S. We compared bark beetle attacks and tree mortality between paired prescribed-burned and unburned stands at each of four sites in Arizona and New Mexico for three growing seasons after burning (2004–2006). Prescribed burns increased bark beetle attacks on ponderosa pine over the first three post-fire years from 1.5 to 13% of all trees, increased successful, lethal attacks on ponderosa pine from 0.4 to 7.6%, increased mortality of ponderosa pine from all causes from 0.6 to 8.4%, and increased mortality of all tree species with diameter at breast height >13 cm from 0.6 to 9.6%. On a per year basis, prescribed burns increased ponderosa pine mortality from 0.2% per year in unburned stands to 2.8% per year in burned stands. Mortality of ponderosa pine 3 years after burning was best described by a logistic regression model with total crown damage (crown scorch + crown consumption) and bark beetle attack rating (no, partial, or mass attack by bark beetles) as independent variables. Attacks by Dendroctonus spp. did not differ significantly over bole heights, whereas attacks by Ips spp. were greater on the upper bole compared with the lower bole. Three previously published logistic regression models of tree mortality, developed from fires in 1995–1996 in northern Arizona, were moderately successful in predicting broad patterns of tree mortality in our data. The influence of bark beetle attack rating on tree mortality was stronger for our data than for data from the 1995–1996 fires. Our results highlight canopy damage from fire as a strong and consistent predictor of post-fire mortality of ponderosa pine, and bark beetle attacks and bole char rating as less consistent predictors because of temporal variability in their relationship to mortality. The small increase in tree mortality and bark beetle attacks caused by prescribed burning should be acceptable to many forest managers and the public given the resulting reduction in surface fuel and risk of severe wildfire. 相似文献