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1.
Biscogniauxia nummularia is known for its association with beech (Fagus sylvatica), on which it occurs as a saprotroph and a pathogen causing strip cankers following water stress. This fungus has also been reported as a dominant endophytic species in plants of the sedge Carex brevicollis growing in the understory of beech forests and adjacent grasslands in Sierra de Urbasa (Navarre, Spain). In this area, stromata of B. nummularia were observed in dead and living wood of beech trees at several locations where plants of C. brevicollis also contained the fungus as an endophyte. Pure cultures obtained from stromata of B. nummularia on F. sylvatica trees were compared to endophytic isolates from symptomless C. brevicollis. Culture morphology and micromorphology as well as rDNA sequences of the internal transcribed spacer (ITS) regions were identical, suggesting that B. nummularia from beech can also live endophytically in C. brevicollis. It is unknown whether the endophytic strains of Carex might have a role as an inoculum source for the infection of beech trees, or whether they represent a dead end in the life cycle of the fungus.  相似文献   

2.
Twenty‐nine fungi that were isolated from seeds and female cones of Podocarpus falcatus from natural forests in Ethiopia, were assessed for their impact on seeds and seedlings of the same host. Based on the results from in vitro seed inoculation tests, we could group the fungi into five categories as: (i) isolates that were pathogenic only to seeds and had no obvious impacts on the germlings; (ii) isolates that were pathogenic only to the germlings; (iii) isolates that were pathogenic both to seeds and the emerging germlings; (iv) isolates that were more or less harmless; and (v) isolates that were germination promoters. Inoculation tests were also performed on 4–7‐day‐old aseptically grown seedlings. Fusarium oxysporum and Polyporus sp., were strongly pathogenic to both seeds and seedlings, while Nectria gliocladioides, Peniophora cinerea and Pestalotiopsis neglecta also demonstrated pathogenicity but to a lesser extent. Other isolates, e.g. Diaporthe spp. resulted in increased germination of P. falcatus seeds and no pathogenicity to seedlings. However, further investigations are required in order to find out how these fungi behave under nursery or field conditions.  相似文献   

3.
The pathogenicity of Colletotrichum dematium was evaluated as the agent causing post-emergence damping-off of current-year beech (Fagus crenata) seedlings. Current-year beech seedlings inoculated with C. dematium died within 20 days after both wound and non-wound inoculation, indicating that this fungus is pathogenic to current-year seedlings. C. dematium was frequently isolated from hypocotyls exhibiting damping-off at five different sites. The incidence of isolation was high and little variation occurred between sites and years. C. dematium was also detected in all litter samples examined although the incidence of detection differed depending on sites and/or detection methods. These results strongly indicate that C. dematium plays an important role in rapid seedling death during the early stages of beech regeneration.  相似文献   

4.
Investigations on root and crown status of spruce and beech were carried out on selected trees in the ‘Werdenfelser Land’ area (Bavarian Alps, Southern Germany). In addition, the association of fine root pathogens of the genera Phytophthora and Pythium with the trees’ rhizosphere was studied. In a variety of stands representing various site conditions, soil and root samples were taken from 12 spruce (Picea abies) pairs and eight beech (Fagus sylvatica) pairs. Each pair consisted of a healthy and a declining tree as indicated by crown transparency. The root status was characterized using a set of parameters, and correlations between crown and fine root status were observed. In spruce, most parameters decreased significantly with increasing crown transparency, whereas in beech, correlations were less pronounced. The total number of lateral roots per cm small root (diameter 2–5 mm) was significantly lower in both species for declining trees compared to healthy trees. Pythium spp. were isolated from 15 of 24 soil samples taken from under spruce, and from eight of 16 samples from under beech. Phytophthora citricola was found in two beech stands only. Among the isolated species, Pythium anandrum, Pythium inflatum and Pythium acrogynum were identified according to morphological features. After polymerase chain reaction‐restriction fragment length polymorphism analysis, residual Pythium isolates were assigned to four different groups. No crown transparency‐dependent differences in isolation frequency were found. In soil infestation tests, all species tested caused root damage on both young spruce and beech plants, with P. citricola being the most aggressive pathogen. Additionally, Pythium‐infected beeches showed severe leaf chloroses and necroses. Due to their low isolation frequency, Phytophthora spp. are not considered to play a major role in the decline of spruce and beech in the investigated area. Pythium spp., however, were isolated frequently, showed pathogenicity towards the fine roots of spruce and beech, and are therefore considered to be at least contributing factors in the decline of Bavarian mountain forests.  相似文献   

5.
Phytophthora cactorum was consistently isolated from basal stem tissues of walnut seedlings affected by collar and root rot. The isolates were identified on the basis of morphological and cultural characteristics and of electrophoretic patterns in polyacrylamide slab gels of total native mycelial proteins and isozymes (arylesterase, malate dehydrogenase, acid and alkaline phosphatase). The electrophoretic phenotypes of walnut isolates were identical or very similar to those of P. cactorum isolates from different hosts (apple, loquat, pineapple-guava and strawberry). In pathogenicity tests, P. cactorum isolates from walnut proved to be highly pathogenic for seedlings of English walnut (Juglans regia) and moderately pathogenic for seedlings of eastern black walnut (Juglans nigra); moreover, they did not rot apple seedlings, suggesting host-specificity. Poor soil drainage and excessive irrigation can be considered as predisposing factors to collar and root rot incited by P. cactorum.  相似文献   

6.
Laboratory studies of Marssonina brunnea (Ell. + Ev.) Magn. established the wide host range and strong pathogenicity of this pathogen to poplars. New Zealand isolates were uniformly pathogenic whereas gross differences in pathogenicity were observed between international isolates. The adoption of a standard inoculation technique for screening poplars for Marssonina resistance is urged.  相似文献   

7.
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8.
《Southern Forests》2013,75(2):57-62
Ceratocystis fimbriata sensu lato (s.l.) is an important pathogen of Eucalyptus. Pathogenicity of isolates has typically been evaluated by inoculating seedlings under greenhouse conditions. It is, however, not clear how accurately this reflects pathogenicity under field conditions. In this study, five techniques to potentially screen C. fimbriata isolates for their relative pathogenicity to Eucalyptus were compared. These included: in vitro growth comparisons on artificial media; inoculations on apples; inoculation on Eucalyptus seedlings in a greenhouse; inoculations on Eucalyptus bolts freshly cut from stems of young trees; and field inoculations on young trees. Eight isolates of C. fimbriata s.l. collected from various areas in South Africa were used. There was considerable variation in growth in culture and aggressiveness of the eight isolates. Field inoculations on young trees were best correlated with inoculations of bolts (r = 0.76). Lower correlation coefficients were obtained with seedlings (r = 0.59), apple inoculations (r = 0.56), and in vitro colony growth (r = 0.42). Inoculation of bolts provides a rapid and reliable method to screen isolates of C. fimbriata s.l. for pathogenicity to Eucalyptus.  相似文献   

9.
Cylindrocarpon‐like fungi are globally distributed plant pathogens and have a wide range of host species. However, very little is known about the species that live in the topsoil of forests and their potential role in reducing the natural regeneration of tree species, particularly of forest trees that produce abundant fruit only once every few years. To enhance our understanding of the species that inhabit the topsoil, we studied the diversity and pathogenicity of Cylindrocarpon‐like fungi inhabiting the litter in old‐growth mixed‐beech forests in the Carpathians (Poland) and in the Alps (Austria), and in a managed beech stand in the Krakowsko‐Cz?stochowska Highland (Poland). The fungi inhabiting the beech litter were investigated using beechnuts and pine seedlings as bait. Isolates were identified based on morphology and DNA sequencing. The pathogenicity of the most common species was investigated by inoculating beech germinants. A wide range of Cylindrocarpon‐like fungi were associated with the beech litter: 718 cultures representing 12 species were isolated. Five taxa were identified down to species level: namely Ilyonectria crassa, I. pseudodestructans, I. rufa, Neonectria candida and N. obtusispora, and seven species were identified to genus level (Neonectria or Ilyonectria species). Ilyonectria destructans, which is considered to be the sexual morph of ‘Cylindrocarpon destructans’, was not found. There were qualitative and quantitative differences between the different forest sites in terms of Neonectria and Ilyonectria species composition in beech litter. The isolation frequency and species richness of Cylindrocarpon‐like fungi were greatest in beech litter taken from old‐growth mixed‐beech forests. Neonectria and Ilyonectria species were capable of killing beech germinants, suggesting that they may play a negative role in natural beech regeneration.  相似文献   

10.
The effect of pH, temperature and light on pathogenicity of two isolates of Cylindrocarpon destructans was studied. Both isolates were pathogenic to fir and pine seedlings. The degree of aggressiveness was affected by pH, temperature, light intensity and also by accompanying bacteria and actinomycetes.  相似文献   

11.
The pinewood nematode (PWN) Bursaphelenchus xylophilus is an invasive pathogen that was introduced from North America to Asian countries and Portugal and is devastating native pine forests. Some native European and Asian Bursaphelenchus nematodes also have weak to moderate pathogenicity to native pine species. To evaluate the potential risk of native Bursaphelenchus species, we inoculated ten Japanese Bursaphelenchus species into native pine species (the dominant forest species) in Japan, and evaluated their pathogenicity using mortality and tracheal tissue damage as indices. Inoculation was conducted on August 3, 2007, and the symptoms were observed every 2 weeks until February 1, 2008. None of the inoculated trees, excluding the pathogenic PWN inoculated control, showed external disease symptoms; however, four species [a less pathogenic PWN isolate, B. luxuriosae, Bursaphelenchus sp. NK215 (undescribed), and NK224 (undescribed)] caused tracheal tissue damage in inoculated seedlings and showed weak pathogenicity. Therefore, we conclude that there are some potentially pathogenic native species of nematodes distributed in Japan. Interestingly, two of these weakly pathogenic species, B. luxuriosae and NK215, are not associated with Pinaceae trees, suggesting that nematode pathogenicity may be a pre-adaptive character. More experimental studies under different conditions are necessary to accurately evaluate the potential risk of these pathogens.  相似文献   

12.
During and after prolonged periods of rainfall in late spring, blighted young twigs of European beech (Fagus sylvatica) were frequently observed in several beech stands in south‐western and southern Germany. Long and short shoots of young understorey trees or lower branches up to 1.5 m above the soil level were affected. Symptoms also occurred regularly on twigs in heights up to 2 m and more above the ground. Necroses usually expanded within the current year’s tissue and often also reached into the previous year’s wood. Ponding rain water in the stands or along forest roads or open soil seemed to promote the disease. Of a total of 54 symptomatic twigs collected in four stands, 37 revealed Phytophthora isolates, of which 33 were P. plurivora and four were P. cambivora. Both species caused extensive lesions on beech twigs in laboratory pathogenicity tests. Patterns of the disease indicated that these pathogens, generally considered soilborne species, in most cases are transmitted from the soil to above‐ground parts of the trees via rain splash. In larger heights, however, other vectors such as snails might be responsible for transmission. Although Phytophthora spp. are well known as causal agents of seedling blight as well as root and cambium rot and aerial bleeding cankers of mature beech, to our knowledge this is the first report of a twig blight in beech associated with soilborne Phytophthora spp. In particular in periods of high precipitation, this disease might pose an additional threat to Central European beech forests, especially endangering the success of artificial and natural regeneration of beech in affected stands.  相似文献   

13.
Summary Thirty‐four fungal species isolated from cork oak (Quercus suber) in Catalonia (NE Spain) during 1992–95 were tested for pathogenicity either in stem, leaf or root inoculations. Eleven species were found to be pathogenic on stem: Biscogniauxia mediterranea, Botryosphaeria stevensii, Diatrype cf. stigma, Endothia gyrosa, Fusarium solani, Graphium sp., Ophiostoma quercus, Phomopsis sp., Phytophthora cinnamomi, Sporendocladia bactrospora and an unidentified Coelomycete. Three fungi showed pathogenic effects on leaves: Dendrophoma myriadea, Lembosia quercina and Phomopsis quercella. No clear pathogenic effects were detected in the root inoculation experiment. Trunk pathogens were differentiated into two groups according to the effects induced in the inoculated plants; B. stevensii, Phomopsis sp. and P. cinnamomi caused the death of the inoculated plants and induced the formation of large cankers and vascular necroses. The other pathogenic species also produced severe cankers and vascular lesions, but no significant mortality was detected. Water stress increased the lesions caused by B. mediterranea and Phomopsis sp., but limited those of P. cinnamomi and the rest of the inoculated fungi. However, water stress did not significantly affect the damage caused by B. stevensii, which was the most virulent of the species tested. Leaf pathogens only showed their effects if the leaf cuticle was previously damaged. Lembosia quercina caused small dark lesions whereas D. myriadea and P. quercella produced large necrotic areas in well‐watered plants. The lesions caused by the last two fungi were reduced by water stress.  相似文献   

14.
The effect of nitrogen fertilization on fungistatic phenolic compounds in fine roots of beech and Norway spruce growing in afforestation plots was analysed. The plots were situated at two sites in Switzerland on acidic soil with low base saturation. For 9 years, the trees have been treated with dry ammonium nitrate to give 0, 10, 20, 40, 80, 160 kg N ha?1 year?1, respectively. The phenolic compounds responded differently to fertilization. Fine roots of beech showed a significant decrease of (?)‐epicatechin and piceatannol with increasing nitrogen fertilization. The concentration of protocatechuic acid was increased with fertilization. Roots of fertilized Norway spruce showed significantly decreased concentrations of 4‐hydroxyacetophenone and piceatannol. The mycelial growth of three isolates each of Heterobasidion annosum s.l. and Cylindrocarpon destructans was tested on agar media containing various phenolic compounds in concentrations found in fine roots of Norway spruce (Picea abies) and beech (Fagus sylvatica). All three H. annosum isolates were inhibited by p‐coumaric acid and (?)‐epicatechin. Two isolates were inhibited by another four phenolic compounds (p‐hydroxybenzoic acid, 4‐hydroxyacetophenone, piceatannol and protocatechuic acid), one by (+)‐catechin. Two of three C. destructans isolates were inhibited by all phenolic compounds except for (+)‐catechin which affected only one isolate, one isolate did not respond at all.  相似文献   

15.
The effects of water stress and defoliation by Lymantria dispar on the successful infection of the fungal pathogen Biscogniauxia mediterranea in seedlings of the Turkey oak (Quercus cerris) were studied under controlled conditions. Seedlings were inoculated by spraying with a spore suspension of Biscogniauxia mediterranea and were subjected to different levels of water stress, insect defoliation, and combinations of the two factors. The leaf water potential was periodically assessed throughout the experiment. The fungus was isolated exclusively from seedlings deprived of water, and insect defoliation increased significantly the proportion of fungus isolation when the water stress was moderate. Thus insect defoliation seems to promote fungal colonization in case of moderate water stress.  相似文献   

16.
The pine nematode Bursaphelenchus mucronatus has been associated with pine wilt in China. This work was intended to investigate the role of the pathogenicity‐related β‐1,4‐endoglucanase gene of B. mucronatus in the infection of pines. In this study, the full‐length cDNA of the Bm‐eng‐1 gene was cloned and characterized from a B. mucronatus isolate. Phylogenetic analysis suggested that the Bm‐eng‐1 gene of B. mucronatus may be acquired from fungi through horizontal gene transfer. The function of the gene was demonstrated using RNA interference. RNA interference indicated that Bm‐eng‐1 was involved in the dispersal, reproductive ability and pathogenicity of B. mucronatus. In situ hybridization showed that Bm‐eng‐1 was specifically expressed in the oesophageal gland of B. mucronatus. Furthermore, to investigate the relation between β‐1,4‐endoglucanase activities and virulence of different isolates, the β‐1,4‐endoglucanase activities and the expression levels of Bm‐eng‐1 were detected in six B. mucronatus isolates with different virulence. β‐1,4‐Endoglucanase activity was generally higher in pathogenic isolates than in non‐pathogenic isolates, and the Bm‐eng‐1 expression levels in different isolates were positively correlated with the β‐1,4‐endoglucanase activity. These findings suggested that β‐1,4‐endoglucanase plays important roles in the pathogenic process of B. mucronatus, and the differential expression of the gene may underlie the different activity levels of β‐1,4‐endoglucanase, subsequently influencing variations in virulence of B. mucronatus isolates.  相似文献   

17.
P. Frey  J. PlNON 《Forest Pathology》1997,27(6):397-407
A collection of 42 isolates of Melampsora allii-populina was established. Fourteen isolates were collected from various poplar cultivars over several French localities and 28 isolates from the alternate hosts (Allium spp., Arum spp. and Muscari comosum) obtained from nature or after inoculation. These isolates were inoculated in the laboratory on a large range of poplar cultivars belonging to several species. No isolate proved pathogenic on all cultivars and many qualitative interactions were observed between isolates and cultivars. This is the first evidence for the existence of physiological races within this fungus. No link was found between pathogenicity on poplar and on the alternate hosts. Among the inoculated cultivars, at least three were susceptible to all isolates (Beaupre, Candicans and Robusta), whereas the following showed qualitative reactions to the inoculated isolates: Altichiero, Carpaccio, Cima, Fritzi Pauley, I 154, Isieres, Luisa Avanzo, NL 2842, Rap and Spijk. Race-specific resistance to M. allii-populina (i.e. resistance to some races of the pathogen, but not to the others) has been found in two North American species (Populus deltoides and Populus trichocarpa) which have never coevolved with this fungus. The results are discussed in comparison with Melampsora larici-populina.  相似文献   

18.
The beech bark disease (BBD) complex affecting American beech consists of the scale insect, Cryptococcus fagisuga, and one or more pathogenic fungi of the genus Neonectria. Following extensive above‐ground mortality of mature beech, stands can be defined by a characteristic set of conditions that are termed the aftermath zone. A long‐standing hypothesis states that C. fagisuga is a necessary predisposing factor for Neonectria infection. Although some evidence supports this in the killing front, the relationship has not been examined in the aftermath zone and other predisposing factors have been proposed. Using quantitative, tree‐level data, we found no significant relationships between C. fagisuga and Neonectria spp. in aftermath stands of central New York State. We propose that the pathosystem operating in the aftermath zone differs from that in the killing front in that C. fagisuga may not be the sole predisposing factor.  相似文献   

19.
We compared the structure of the arboreal layer and the diversity and species composition of the understory vegetation of three types of mature forest communities: oak (Quercus pyrenaica) and beech (Fagus sylvatica) forests and Scots pine (Pinus sylvestris) plantations. Our main aim was to determine whether differences in these variables existed and were due to the identity of the dominant tree species. We selected four stands or replicates per forest type located geographically close and with relatively similar conditions. We found no differences in the arboreal structure of oak and beech forests, which were characterised by great variability in tree size, while in case of plantations, this variability was lower at both the intra-stand (estimated by the coefficient of variation) and inter-stand (i.e. the four replicates harboured trees of similar sizes) scales. However, the highest variability in the canopy layer of natural forests was not consistently linked to greater understory species richness. Indeed, the lowest plant species richness was found in beech forests, while oak forests harboured the highest value at either the sampling unit (per m2) or stand scales. The greatest negative correlation between plant diversity and the environmental variables measured was found for litter depth, which was the highest in beech forests. The results obtained by the CCA indicated that the four replicates of each forest type clustered together, due to the presence of characteristic species. We concluded that pine plantations did not approach the environmental conditions of native forests, as plantations were characterised by singular understory species composition and low arboreal layer variability, compared to natural woodlands.  相似文献   

20.
The blue‐stain fungus Ceratocystis resinifera colonizes wounds on living Picea spp. and other conifers in Europe and North America. Little is known regarding the pathogenicity of this fungus and consequently, four Norwegian C. resinifera isolates were inoculated on to Norway spruce (Picea abies) using two different techniques. These included single‐point inoculations on young trees (two inoculations per tree on 14‐year‐old trees) and mass‐inoculations on older trees (～200 inoculations per tree on 34‐year‐old trees). In both experiments, C. resinifera induced minor symptoms that in most cases did not differ significantly from inoculation with sterile agar. The virulent blue‐stain fungus C. polonica, which was inoculated for comparative purposes, induced extensive symptoms, causing 83% dead cambium circumference and 82% blue‐stained sapwood, and long necrotic lesions in the phloem. The results suggest that C. resinifera is non‐pathogenic or only mildly pathogenic to Norway spruce and does not present a threat to these trees.  相似文献   

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