bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐term survival of Bursaphelenchus xylophilus in living Pinus sylvestris in an established plantation
Authors: Halik S. , Bergdahl D. R.
Published: June 2007

Scots pines (Pinus sylvestris) in a 20‐year‐old plantation in northern Vermont, USA, were inoculated with the pinewood nematode (Bursaphelenchus xylophilus) in 1987. To determine how long B. xylophilus would survive after inoculation, the trees were periodically observed and sampled for the nematode up to the end of 1993. The nematode was still found to persist in living, healthy‐appearing pines 6 years after inoculation.
The use of needle‐trace method (NTM) in retrospectively detecting Lophodermella needle‐cast epidemic
Authors: Jalkanen R. , Aalto T. , Kurkela T.
Published: June 2007

The recently developed needle‐trace method (NTM) was successfully used to verify retrospectively the occurrence of a well‐documented needle‐cast epidemic caused by Lophodermella sulcigena in the 5‐year period of 1977–1981 in a stand of Pinus sylvestris.
Did climatic warming trigger the onset and development of yellow‐cedar decline in southeast Alaska*
Authors: Hennon P. E. , Shaw C. G.
Published: June 2007

Yellow cedar (Chamaecyparis nootkatensis) is a valuable tree species that is experiencing an extensive forest decline on over 200000 ha of unmanaged forest in southeast Alaska. Biotic factors appear secondary and some abiotic factor is probably the primary cause of this naturally occurring decline. A warming climate, which coincided with the onset of extensive tree mortality about 100 years ago, may have triggered one of the possible abiotic causes such as freezing damage and/or soil toxicity.
Glucanohydrolase enzyme activity in embryos of Scots, Corsican and lodgepole pines infected in vitro with Heterobasidion annosum
Authors: Nsolomo V. R. , Woodward S.
Published: June 2007

Embryos of Scots pine (Pinus sylvestris), Corsican pine (P. nigra var. maritima) and Lodgepole pine (P. contorta) were infected in vitro with Heterobasidion annosum and the activities of 1,3‐β‐glucanase, chitinase and β‐glucosidase were monitored. Both the infected and control embryos of the three pine species showed the presence of the enzymes. Statistical analysis showed no significant increase (P > 0.05) in the levels of 1,3‐β‐glucanase in infected embryos for all the three pine species. However, there was a significant increase in levels of chitinase in infected embryos of P. contorta and P. nigra var. maritima and also in levels of β‐glucosidase in infected embryos of all three of the pine species. The study has therefore revealed that constitutive levels of glucanohydrolase enzymes exist in the embryos of the three pine species and that the induction of chitinase and β‐glucosidase was a factor in the response of the embryos to stimulation by H. annosum infection.
The occurrence and pathogenicity of uni‐ and binucleate Rhizoctonia and Pythiaceae fungi among conifer seedlings in Finnish forest nurseries
Authors: Lilja A.
Published: June 2007

Uni‐ and binucleate Rhizoctonia and Pythiaceae fungi were isolated from roots of dieback seedlings. Only binucleate Rhizoctonia strains were present in the roots of healthy seedlings. In pathogenicity tests, uninucleate Rhizoctonia sp. were pathogenic and binucleate Rhizoctonia spp. non‐pathogenic. Pythium ultimum var. ultimum and Phytophthora undulata were the only Pythiaceae fungi that killed 12‐week‐old seedlings.
Histology of witches' brooms on Betula pubescens
Authors: Jump B. A. , Woodward S.
Published: June 2007

Witches' brooms caused by Taphrina betulina on Betula pubescens formed from the development of large numbers of axillary shoots on infected buds. Broom shoots showed vigorous growth during the first season, but died in the second or third year after initiation. Occasional adventitious root production was noted at the base of broom shoots. Cortex and secondary phloem tissues of the central gall‐like structure of the brooms expanded. The bark of infected material lacked brachysclereids, and tangential ray parenchyma of the secondary phloem were also absent. Numerous shoot bases and aborted axillary buds were present within the bark. Abundant starch granules were present, especially in the phellogen and phelloderm layers. Distortion of the internal lignified tissues was due to the presence of multiple vascular connections from the proliferation of shoots on the broom.
Breakdown of barrier zones and prediction of the spread of discolouration and decay resulting from stem wounds in Eucalyptus regnans and E. obliqua
Authors: White D. A. , Kile G. A.
Published: June 2007

In Eucalyptus regnans and E. obliqua a rapid increase in the spread of defects (discolouration and decay) was observed more than 14 years after wounding. This increase was due to a breakdown of the barrier zone and the subsequent spread of defects into wood formed after wounding. Satisfactory relationships predicting defect extent using time since wounding could not be derived.
Evaluation of Dutch elm disease susceptibility and pathogenicity of Ophiostoma ulmi using micropropagated elm shoots
Authors: Dorion N. , Bigot C. , Neumann P.
Published: June 2007

Elm (Ulmus sp.) shoots from in vitro micropropagated plants were tested with Ophiostoma ulmi culture filtrates, at different dilutions to determine the susceptibility of different host clones to Dutch elm disease (DED). ‘Commelin’, a susceptible Dutch hybrid, showed a high wilting index but that of American elm was higher. Although U. pumila × japonica (Sapporo gold 2) was the most tolerant to spore inoculation, its wilting index was as high as that of ‘Commelin’. The absorption capacity and wilting index of the elm shoots showed consistent correlation to isolate effectiveness (as determined by inoculation experiments), to production of toxin (cerato‐ulmin) and to filtrate dilution. This method could be used to assess the effectiveness of the different O. ulmi isolates and for the detection of elm genotypes that are highly susceptible to Dutch elm disease.
Stem damage in Swiss forests: incidence, causes and relations to crown transparency
Authors: Innes J. L. , Schwyzer A.
Published: June 2007

In the annual assessments of forest damage in Switzerland, the nature of any stem damage is recorded on the target trees. As the inventory is undertaken on a representative basis, the extent of stem damage should accurately reflect the extent of stem damage on trees in Switzerland. This paper examines the occurrence of stem damage by species, region and forest type and determines whether any relationship exists between stem damage and crown transparency.
The condition of the phloem in declining oaks
Authors: Schlag M. G.
Published: June 2007

Oaks (Quercus petraea, Q. robur) from several sites in eastern Austria affected by novel oak decline (NOD), as well as oaks (Q. robur) showing symptoms of oak yellows (OY), were tested for the presence of mycoplasma‐like organisms (MLOs). The samples, comprising roots, annual shoots, and branches, were examined using light‐, fluorescence‐, and electron‐nucroscopic techniques. Staining with the DNA‐fluorochrome DAPI provided no evidence for the presence of MLOs in any of the samples. Furthermore, no pathological sieve‐tube necrosis and no abnormal callose accumulation could be observed. An association of MLOs with‘novel oak decline’ or ‘oak yellows’ is, therefore, unlikely.
Histology of Pinus maximinoi cones infected by Cronartium conigenum1
Authors: Rayachhltry M. B. , Webb R. S. , Miller T. , Kimbrough J. W.
Published: June 2007

Apparently healthy and C. conigenum infected female strobili of Pinus maximinoi, collected in Guatemala, were histopathologically studied by light microscopy. Scales from infected cones were fused and fertile scales had aborted seeds. Infected cone scales lacked fibre cells in the cortex, which are abundant in healthy cone scales. Intercellular spaces of cortex contained abundant hyphae compared to phloem and xylem.

The cell walls of infected tissues in the ovules were darkly stained, while those of comparable healthy tissue were colourless under Pianeze's IIIB stain. Infected ovules of different developmental stages with nucellus, or nucellus plus spongy tissue, were observed. The cells of each tissue type contained many haustoria and did not develop into female gametophyte and embryo. Ovule colonization by hyphae appeared after pollination and subsequently caused their early abortion.
Uni‐ and binucleate Rhizoctonia spp. co‐existing on the roots of Norway‐spruce seedlings suffering from root dieback
Authors: Hietala A. M.
Published: June 2007

Rhizoctonia fungi were isolated from the roots of 2‐year‐old nursery‐grown Norway‐spruce seedlings displaying root‐dieback symptoms. The most frequently isolated species, a uninucleate Rhizoctonia sp., was found to co‐exist with binucleate Rhizoctonia in the same root system of several seedlings. All the uninucleate isolates anastomosed with each other forming a single anastomosis group with common cultural characteristics. Binucleate Rhizoctonia isolates were divided into several, morphologically dissimilar anastomosis groups (AG‐I, R. spp.). In a pathogenicity test under sterile conditions, isolates belonging to the uninucleate Rhizoctonia sp. infected all root regions, particularly the root tips, resulting in a stunted root‐system morphology, as was also observed in the isolation material.

Binucleate Rhizoctonia spp. colonized only basal root regions, occasionally infecting cortical cells with monilioid hyphae, and had no effect on root growth.
Immunocytochemical localization of pathogenesis‐related proteins in roots of Norway spruce infected with Heterobasidion annosum
Authors: Asiegbu F. O. , Denekamp M. , Daniel G. , Johansson M.
Published: June 2007

The occurrence and accumulation of β‐1, 3‐glucanase and chitinase in seedling roots of spruce (Picea abies) following challenge by the root‐rot pathogen Heterobasidion annosum were studied. Chitinase activity increased 2–3 fold following inoculation, whereas no significant increase in the activity levels of glucanase was recorded during infection. With TEM immunogold labelling, the enzymes were localized in protein aggregates in host tissues and in the cell walls of intercellular hyphae. Gold particles were sparse and irregularly distributed within host‐cell walls. Only minor labelling was observed on hyphal walls coated with electron‐dense materials. The labelling intensity increased with infection time and was always higher than in non‐infected seedling roots. When this experiment was repeated using root samples inoculated with the saprophyte Phlebiopsis gigantea, a similar labelling pattern was observed. The cross reactivity of antisera raised against sugar‐beet chitinase and glucanase with spruceroot enzyme extracts was demonstrated using dot‐blot assays and ELISA.
Transmission of hypovirulence agents among some Cryphonectria parasitica strains from Italy
Authors: Maresi G. , Giovannetti L. , Ventura S. , Turchetti T.
Published: June 2007

Six hypovirulent (H) strains of Cryphonectria parasitica collected in Italy were tested for dsRNA content, virulence, and conversion ability. Nine converts were also checked for dsRNA. In inoculation trials, H and converted (C) strains showed reduced pathogenicity. Most H and C strains were able to convert strains from various v‐c groups. DsRNA banding patterns were similar in five of the H strains and in their converts, while the last one and its converts showed no evidence of dsRNA. The broad conversion ability of H strains seems to be responsible for the natural recovery of Italian chestnut trees.
Differences in Agrobacterium infections in silver birch and Scots pine
Authors: Aronen T. , Häggman H.
Published: June 2007

The aim of this study was to investigate the differences in infections caused by Agrobacterium tumefaciens in a conifer, Scots pine (Pinus sylvestris), and in a non‐host deciduous species, silver birch (Betula pendula). All the Agrobacterium tumefaciens strains tested caused crown‐gall formation in both tree species, but the infection rates varied remarkably. In Scots pine, the development of galls was rare, and slower than in silver birch. Inoculation into the base of the stem were the most successful in gall induction. Silver‐birch galls were large, often surrounding the whole stem, in contrast to Scots pine galls, which were characterized by their small size and neck‐like connection with the host plant. In silver birch, no other morphological changes could be seen. In Scots pine, abnormal phenotypes with proliferating short shoots above the galls were observed during the second and third growing season. The results indicate that, of the two non‐host tree species, the deciduous one, silver birch, is more susceptible to an A. tumefaciens infection than the conifer, Scots pine. The matrix for A. tumefaciens infection in silver birch differs from that in Scots pine, since the terpene compounds of Scots pine seem either to kill the agrobacteria or to suppress their growth. The differences between the species could be partly caused by their difference in sensitivity to phytohormones. These features reflect evolutionary incompatibility between A. tumefaciens and a gymnosperm.
Occurrence of Persian (English) walnut blight and its control in the nursery
Authors: Belisario A. , Zoina A.
Published: June 2007

Observations carried out over several years in walnut nurseries in Italy revealed bacterial walnut blight, induced by Xanthomonas campestris pv. juglandis, to be the most harmful disease; 4 years of field trials were performed. Infection level was shown to be related to the inter‐row distances. The inter‐row distances 0.6, 0.8, 1.0, and 1.4 m were tested. The 1.4‐m distance resulted in the best control of bacterial spread, even under high inoculum pressure due to artificial inoculations. Foliage flush was the stage most vulnerable to bacterial infection. Chemical control with Bordeaux mixture and mancozeb was tested, but only Bordeaux mixture showed some effect. Two copper treatments, at the beginning and at the end of the vegetative period, can be recommended for those areas that are heavily infested with X. c. pv. juglandis.
Vegetative compatibility and conversion to hypovirulence among Italian isolates of Cryphonectria parasitica
Authors: Causin R. , Frigimelica G. , Montecchio L. , Mutto Accordi S.
Published: June 2007

A total of 850 virulent isolates of Cryphonectria parasitica were isolated from natural cankers on European chestnut trees growing in various Italian regions. Vegetative‐compatibility (v‐c) group membership was tested using the merge‐barrage method. In all, 19 vegetative‐compatibility groups were found, and, for each of these, a representative isolate (v‐c tester) was identified; 49% of the isolates were compatible with the tester of only one v‐c group, whereas 51% were compatible with the testers of more than one v‐c group; 3% of the isolates showed compatibility with seven v‐c groups. The coincidence between vegetative incompatibility and failure of conversion occurred in only a few cases; 42% of the converts were stable with respect to their morphological characteristics and presence of cytoplasmic ds‐RNA. The results obtained in Italy suggest that, for an efficient biocontrol programme, it is preferable to evaluate the tendency of a population to be converted rather than evaluating the v‐c group membership.
Effects of sulphuric acid and heavy‐metal deposition on frequency of asymptomatic infections of Gremmeniella abietina in Scots‐pine seedlings
Authors: Ranta H. , Neuvonen S. , Virtanen T.
Published: June 2007

The isolation frequency of Gremmeniella abietina was measured from asymptomatic 4‐year‐old Scots‐pine seedlings. The seedlings had been subjected to simulated sulphuric deposition (pH 3.1 or 4.1) or control treatments (irrigation with spring water (pH 6), or no irrigation) during the three previous growing seasons. The seedlings were planted in soil originating from two localities with different backround levels of copper (Cu) and nickel (Ni), and the soil was further amended with Cu (63.3 mg/1 of soil) and Ni (20.5 mg/1 of soil), or a combination of the two. The seedlings were inoculated with conidia of G. abietina during their third growing season in the field. Asymptomatic infections of G. abietina were recovered frequently from seedlings that had received water irrigation. The addition of sulphuric acid to the irrigation water, and/or the lowered pH (pH 3.1 and 4.1) resulting from this addition, mitigated the effect of water application. The effect of Ni‐treatment on the recovery of G. abietina depended on the irrigation treatment; with no irrigation, Ni‐treatment increased isolation frequency, but, in irrigated seedlings the response was the opposite. Only 10.6% of the seedlings had symptoms caused by G. abietina; most of the seedlings had become infected before the application of the various treatments.
Occurrence of Gremmeniella abietina damage on Scots pine along a pollution gradient from Monchegorsk nickel smelter to western Lapland
Authors: Kaitera J. , Fedorkov A. , Jalkanen R. , Krutov V. , Tsvetkov V.
Published: June 2007

Gremmeniella abietina damage was studied at stand and tree level on the Kola Peninsula and in northern Finland. At stand level, damage was recorded in four areas in Finland, while only individual damaged trees were found in Russia. According to the results of branch analysis, there was no sign of endemic epidemics in any of the areas. There was a significant negative correlation between the average G. abietina damage and modelled SO2 deposition and temperature sum along the gradient. The results suggest that G. abietina is distributed all over northern Finland and the Kola Peninsula in natural stands of Scots pine, and that the direct effect of SO2 deposition from the Monchegorsk nickel smelter on the damage may be minimal.
Inoculation of young pine seedlings with Peridermium pini from north‐east Scotland
Authors: Pei M. H. , Brodie J.
Published: June 2007

Seedlings of Pinus sylvestris, P. nigra ssp. laricio, and P. mugo vars mughus, rostrata and pumilio were inoculated at their cotyledon stage with aeciospores of Peridermium pini from north‐east Scotland. Infection was determined by the presence of both mycelia and haustoria in free‐hand or paraffin sections. In the second growing season, infected seedlings showed symptoms such as stem‐swelling, development of spermogonia and aecia, and death. In a second experiment, young P. sylvestris seedlings from seven seed sources collected in Great Britain were inoculated and the infection were examined after 6 weeks. In the samples of 50 seedlings from each source, 30–70% seedlings were infected.
Control of Dutch elm disease by induced host resistance
Authors: Sutherland M. L. , Mittempergher L. , Brasier C. M.
Published: June 2007

A range of fungi was screened for the ability to suppress symptoms of Dutch elm disease in European and hybrid elms under UK and Italian field conditions. The efficacy of the preventative inoculations varied Considerably between elm clones of differing resistance to the causal fungus Ophiostoma novoulmi. On susceptible English elm, Ulmus procera, preventative inoculations with conidia of Verticillium dahlias, Opbiostoma ulmi or Ophiostoma piceae (OPH form) caused no reduction in final disease levels. On U. x bollandica cv.‘Commelin’, pretreatment with V. dabliae or O. ulmi reduces final disease levels, but not significantly, On the elm clone Ca06 of U. carpinifolia, and on the hybrid clones FL025 and 196–6, significant (p0.05) symptom suppression occurred in trees pretreated with O. ulmi or V. dahliae. On the more resistant elm clones 3–14 and Lobel, only V. dahliae was an effective pretreatment (p0.05). Certain pretreatment fungi alone caused symptoms in some of the elm clones. Major difficulties in using this approach to control Dutch elm disease are discussed.The technical assistance by F. C. Baldwin, R. Brooker, S. A. Kirk and J. Rose at the Forest Research Station, Alice Holt, and by A. Fagnani and F. Ferrini at CNR, Florence, as well as statistical advice from A. J. Peace at Alice Holt, is gratefully acknowledged.The authors would like to thank the Pilkington Charitable Trust for funding the research in the UK and lsotron plc, Swindon, Berkshire, for gamma irradiating the conidial suspensions. The Italian contribution was supported by the National Research Council of Italy, special project RAISA, subproject no. 2, paper no. 2133. The authors also thank John GIBBS for helpful comments on the manuscript.
Befall der Fichte (Picea abies) durchHeterobasidion annosum in Abhängigkeit vom Baumalter
Authors: Rleger S.
Published: June 2007

Infection of Norway spruce (Picca abies) by Heterobasidion annosum in relation to tree age

The presence of H. annosum in stems and roots of young Picea abies of different age classes was determined in four heavily infected stands in Southern Germany. The frequency of infected trees increased with age (0% in age class I (I‐10 years), 7,5% in class 2 (11‐20 years), 33,3% in class 3 (21‐30 years)). Only the S‐type was found. An additional investigation of 1‐10‐year‐old trees growing on stumps with H. annosum decay or tightly surrounded by carpophores yielded an infection rate of 20% (mainly S‐type). H. annosum was confined to very small regions in the host tissue in these cases.
Capability of the European and North American race of Gremmeniella abietina to hydrolyse polygalacturonic acid in vitro
Authors: Petäistö R‐L. , Lappi J.
Published: June 2007

Polygalacturonase was found to be one of the first enzymes secreted by a pathogen during infection. The polygalacturonic‐acid hydrolysing activity was compared between the North American and the European race of Gremmeniella abietina in vitro. Isolates were grown in pure pectin media from which the enzyme activity was analysed. Altogether, 29 isolates were tested in five experiments (experimental runs in a growing chamber). The data were analysed using variance‐component models that included fixed‐race effects and random‐experiment, isolate, flask and measurement effects. The European race secreted more polygalacturonic‐acid hydrolysing enzyme than the North American race and the mycelial dry weight produced was smaller for the European race. The differences between races were of the same order of magnitude as the variation between isolates within races; variance components relating to experimental errors were quite large. No correlation was found between the activity and mycelial dry‐matter production within the races. Logarithmic transformation removed the apparent racial differences in the variability of the activity and mycelial dry weight. Results from the additionally tested A‐ and B‐type of Finnish isolates indicated differences in dry‐matter production.
Variation in Melampsoridium resistance among European white‐birch clones grown in different fertilization treatments
Authors: Poteri M. , Rousi M.
Published: June 2007

Resistance of 2‐year‐old plantlets of seven European white birch, Betula pendula, clones to birch rust, Melampsoridium betulinum, was studied in field experiments and in a leaf‐disc bioassay. In addition, rust resistance of plantlets growing in a nursery under three fertilization treatments was tested. The birch clones clearly varied in their levels of resistance. One of the clones was consistently the most resistant, and two were very susceptible. Plantlets growing in the lowest fertility treatment were the most resistant. Clone × fertilization interaction was small. The plantlets grown in the lowest fertilization treatment, in particular, deviated from the other treatments. Generally good rust‐resistance correlations were obtained between different experiments. The leaf‐disc bioassay was an effective way of determining the field rust resistance of birch clones. The possibility of trade‐offs between rust resistance and tree growth is discussed.
Seedling response of two trembling aspen (Populus tremuloides) families to infection by Hypoxylon mammatum
Authors: Enebak S. A. , Li B. , Ostry M. E.
Published: June 2007

Open‐pollinated progenies from two trembling aspen (Populus tremuloides) families with a 30‐year field history of 91% (putatively susceptible, PS) and 45% (putatively resistant, PR) mortality, respectively, caused by Hypoxylon mammatum, were grown in a greenhouse for 3 and 9 months. Seedlings were inoculated with two isolates of H. mammatum, representing high and low aggressiveness, through a stem wound. Beginning 4 days after inoculation, host responses were examined on 312 seedlings per family for a period of 5 weeks on 3‐ and 9‐month‐old seedlings. Significant differences in host responses were observed between the two isolates, with the more aggressive isolate allowing less callus formation, causing more tissue necrosis and producing longer cankers than the less aggressive isolate on both aspen families. Between‐family difference was much greater than within‐family difference for tissue necrosis, callus formation and canker length for both seedling ages. When the 3‐month‐old seedlings were challenged with H. mammatum, the PR family showed greater tissue necrosis, longer cankers, and less callus formation than the PS family. However, when the more lignifìed 9‐month‐old seedlings of the same families were inoculated, the PR seedlings had much less tissue necrosis, shorter cankers, more callus formation and less seedling mortality than the PS family. The results indicate that artificial inoculation of seedlings in a greenhouse can differentiate two aspen families at the seedling stage, but their correlation to field performance is highly dependent upon the seedling age. Host responses of older seedlings may be a better indicator of field performance.
Seedborne fungi in Norway spruce: testing methods and pathogen control by seed dressing
Authors: Motta E. , Annesi T. , Balmas V.
Published: June 2007

Italian seed lots of Norway spruce (Picea abies) were analysed by agar plate tests and seedling symptom test. Fusarium spp., Phoma spp. and Sirococcus conigenus were present on seeds, together with some saprophytes, but only S. conigenus and Fusarium spp. caused mortality in the seedling symptom test. Pathogenicity tests with 19 isolates belonging to nine Fusarium species showed that only some were pathogenic. Fusarium dlamini, reported for the first time in Italy, caused only some pre‐emergence mortality. Pathogenicity tests with S. conigenus indicated that the isolate was pathogenic and that temperature can greatly affect the results. Seed dressing with prochloraz was suitable for controlling the seedborne pathogens. Agar plate tests are effective and practicable methods for the detection of spruce seed mycoflora.
Quantitative assessment of fungal colonization in Norway spruce after green pruning
Authors: Metzler B.
Published: June 2007

In July and in October of 1978, 1979, 1980 five Picea abies stands in Baden‐Württemberg, Germany were green‐pruned up to a tree height level of c. 10 m. In 1993–94, 30 pruned trees and five control trees from each stand were harvested for investigation. The quality of pruning proved to be excellent because only few branch collar, bark injuries or too long branch stubs were detected. Based on isolations from more than 6000 wood specimens of c. 20 mm3 obtained from 175 trees, specific infection rates are given for different tree compartments. Wood decay fungi as well as important blue stain fungi were only rarely present. Tolerable discolourations were limited to the stub containing core of a few trees. Wood formed after pruning showed neither more fungal infections nor other related disadvantages compared with the respective increment from unpruned control trees. Nectria fuckeliana, proved to be the most abundant fungus in pruned trees especially in the branch stubs. Respective infection rates in and close to dry branches were compared. Bacteria could be found in the pruned branch stubs, however, they did not penetrate into the heartwood or sapwood of the stems. Both summer and autumn pruning involve only very low risk of wood deterioration. However, summer pruning shows some advantages with respect to lower infection rates by N. fuckeliana.
Responses of Cupressus and Chamaecyparis callus tissues to inoculations with Seiridium cardinale
Authors: Spanos K. A. , Woodward S.
Published: June 2007

Inoculations of callus generated from micropropagated shoots of Cupressus sempervirens, Cupressus macrocarpa, Cupressus torulosa and Chamaecyparis lawsoniana showed that callus of species resistant or relatively resistant to Seiridium cardinale supported significantly less surface growth of the pathogen than callus of susceptible species. In dual cultures of Cupressus sempervirens or Cupressus torulosa callus with S. cardinale, inhibition of fungal growth towards the callus was correlated with known field resistance of these host species. Lignification, accumulation of polyphenolics and possible suberization of cell walls were detected in inoculated callus. This response was also correlated with known field resistance of the tested host species.
Identification of European Armillaria species by analysis of isozyme profiles
Authors: Bragaloni M. , Anselmi N. , Cellerino G. P.
Published: June 2007

Studies were carried out to test the possibility of identifying European Armillaria species by using isozyme patterns. Twenty‐two different enzymes were used to analyse the haploid and diploid mycelium extract of Armillaria borealis, Armillaria cepistipes, Armillaria gallica, Armillaria mellea, Armillaria ostoyae and Armillaria tahescens. Tests for fumarase (E.C. 4.2.1.1.), aconitase (E.C. 4.2.1.3.), leucine‐amino peptidase (E.C. 3.4.11.1.), isocitrate dehydrogenase (E.C. 1.1.1.42.), shikimic dehydrogenase (E.C. 1.1.1.25), glucose‐6‐P‐dehydrogenase (E.C. 1.1.1.49.), malic enzyme (E.C. 1.1.1.40.), 6‐P‐gluconic dehydrogenase (E.C. 1.1.4.4.), pectin esterase (E.C. 3.1.1.11.), and pectic lyase (E.C. 4.2.99.3.) did not reveal enzyme activity. Isozyme profiles of acid phosphatase (E.C. 3.1.3.2.), phospho‐gluco‐isomerase (E.C. 5.3.1.9.), peroxidase (E.C. 1.11.1.7.), polyphenoloxidase (E.C. 1.14.18.), malic dehydrogenase (E.C. 1.1.1.37.), glutamic dehydrogenase (E.C. 1.4.1.3.) and superoxide dismutase (E.C. 1.15.1.1.) were ineffective for species identification. In contrast, esterase (E.C. 3.1.1.1.), glutamic‐oxalacetic transaminase (2.6.1.1.), phospho‐gluco‐mutase (E.C. 2.7.5.1.), alcohol dehydrogenase (E.C. 1.1.1.1.), and polygalacturonase (E.C. 3.2.1.15.) isoenzyme patterns showed enough polymorphism to allow the identification of the different Armillaria species. However, it is necessary to compare several enzyme profiles for a conclusive identification.

Intraspecific crosses of A tabescens were confirmed by the presence of a heteromeric isozyme pattern of alcohol dehydrogenase and phospho‐gluco‐mutase.
Somatic incompatibility among African Armillaria isolates
Authors: Abomo‐Ndongo S. , Guillaumin J.‐J.
Published: June 2007

Twenty‐five African Armillaria isolates paired on malt‐agar were divided into four groups on the basis of somatic incompatibility reactions. One of the groups is similar to the European species Armillaria mellea, while another group is provisionally designated as Armillaria heimii.
Identification of the genus Armillaria by specific amplification of an rDNA‐ITS fragment and evaluation of genetic variation within A. ostoyae by rDNA‐RFLP and RAPD analysis
Authors: Schulze S. , Bahnweg G. , Möller E. M. , Sandermann H.
Published: June 2007

Genetic variation among Armillaria ostoyae isolates was studied by rDNA‐restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis. A total of 20 A. ostoyae isolates, mainly obtained from Picea spp. of different geographical origins, were examined. Southern hybridization of whole‐cell DNAs digested with AvaII and probed with biotin‐labelled cloned rDNA from Saccharomyces carlsbergensis allowed the differentiation of five RFLP groups. UPGMA cluster analysis of RAPD profiles (138 scorable bands) generated by 10 decamer primers (OPA 01‐OPA 10) grouped the isolates in subclusters at similarity levels between 40% and 96%, indicating high intraspecific genetic variability. Some isolates of different geographical origins subgrouped together, suggesting that similar mutational events have occurred independently and that genetic exchange and recombination occurs among the DNAs in natural populations. The potential role of historical and current spread of spruce plants on the genetic variation of A. ostoyae isolates in Europe is discussed. Using the primer pair ARM‐1 and ARM‐2, an Armillaria‐specific ITS‐DNA fragment of about 660 bp was obtained. No intraspecific RFLP of this amplicon could be revealed, indicating low genetic variability of this region.

The established informative RFLP and RAPD markers and also the Armillaria‐specific ITS‐DNA fragment may be powerful tools for further epidemiological, phylogenetic and host‐pathogen interaction studies with A. ostoyae.
Abies sibirica in the Ural region is attacked by the S type of Heterobasidion annosum
Authors: Korhonen K. , Fedorov N. I. , Porta N. La , Kovbasa N. P.
Published: June 2007

Specimens of Heterobasidion annosum were collected in seven mixed stands of Abies sibirica and Picea abies in Yekaterinburg and Perm regions on the western side of the Ural Mountains, Russia. Pure cultures were isolated from 60 collections and identified in mating tests. Only the S intersterility group was found, attacking both fir and spruce. Based on the appearance of clamp connections in matings, the compatibility of 12 homokaryons from the Ural area with 14 S group homokaryons from western Europe was 100%, with 13 F group homokaryons from southern Europe 76% and 9 P group homokaryons from western Europe 3%. The results show that A. sibirica, in contrast to A. alba, is very susceptible to the S type H. annosum.
Histological analyses of the host response of two aspen genotypes to wounding and inoculation with Hypoxylon mammatum
Authors: Enebak S. A. , Bucciarelli B. , Ostry M. E. , Li B.
Published: June 2007

Ramets derived from root sprouts of two quaking aspen (Populus tremuloides) parents were either mechanically wounded or wounded and inoculated with mycelium of Hypoxylon mammatum. Female aspen parents were considered either resistant or susceptible based on a 30‐year field trial of their open‐pollinated progenies that had 21% and 93% mortality, respectively, caused by H. mammatum. Each stem was wounded twice at the base and in the nonlignified zone. Samples were taken 5 mm above the site of wounding at 7 and 14 days. Histochemicals used were phloroglucinol‐HCl and Sudan Black B to detect lignin and suberin, respectively. Thin sections of the resistant aspen ramets showed intensive staining phloroglucinol‐HCl, which was localized along both sides of the wound margin. Collenchyma callus was well developed by day 7 and was derived from the phloem tissue internal to the cell walls staining positive for phloroglucinol‐HCl, near the vascular cambium. In contrast, the tissues of susceptible aspen ramets were less stained, the stained cells were less scattered and less collenchyma callus had formed than on the resistant ramets. The presence of the fungus increased the amount of staining observed with phloroglucinol‐HCl and delayed wound closure in both aspen genotypes. No distinguishing pattern could be identified between the two aspen genotypes with respect to suberin formation. When comparing stem response to phloroglucinol‐HCl with respect to the tissue type on the same stem (succulent versus woody), the inoculation of older woody tissue resulted in a more defined host response and thus were better in separating the two aspen genotypes.
Colonization patterns and topochemical aspects of sap streak caused by Stereum sanguinolentum in Norway spruce
Authors: Kleist G. , Seehann G.
Published: June 2007

Fresh sapwood blocks of Norway spruce (Picea abies) were exposed to 12‐ and 60‐day attack by Stereum sanguinolentum in pure culture and were examined with respect to structural, topochemical and colour alterations. Final stages of degradation by 5. sanguinolentum were studied on naturally decayed spruce wood after 1 year of fungal growth. The development of discoloration in the main anatomical directions of wood was assessed. Furthermore, microspectrophotometrical studies on the decomposition of cell wall polyphenols were performed. Initial signs of sap streak appeared already 8 days after fungal infection. Within the three‐dimensional decay pattern, mycelial aggregations associ‐ated with the ray tissue proved to be the major cause of discoloration. UV extinction measurements taken at 280 nm of different parts of cell wall transverse sections revealed a specific pattern of lignin distribution and its derivatives during fungal degradation.
Similarity between fungi identified as Diplodia pinea f. sp. cupressi in Israel and Botryosphaeria stevensii or Diplodia mutila on Juniperus in the United States
Authors: Stanosz G. R. , Swart W. J. , Smith D. R.
Published: June 2007

A fungus identified as Botryosphaeria stevensii (anamorph Diplodia mutila) causes a canker disease that results in dieback of Juniperus species in the United States. A fungus identified as Diplodia pinea f. sp. cupressi causes a similar disease of Cupressus species in Israel and elsewhere. Cultural characteristics, pycnidia, and conidia of isolates of these two pathogens were compared. The ability of each fungus to produce cankers on Cupressus sempervirens was tested. Random amplified polymorphic DNA (RAPD) marker patterns also were analysed, using Sphaeropsis sapinea (syn. Diplodia pinea) isolates as an outgroup. Results indicate the fungus identified as D. pinea f. sp. cupressi from cypress in Israel is the same as, or at least highly similar to, the fungus identified as B. stevensii (or D. mutila) from juniper in the United States. Analysis of RAPD markers indicates relatively low similarity between these isolates and those of S. sapinea. Because these results are consistent with a previously published report describing substantial morphological and isozyme differences between isolates identified as D. pinea f. sp. cupressi and those of S. sapinea, use of the name D. pinea f. sp. cupressi should be abandoned. Inconsistencies between these isolates from juniper and cypress and published descriptions of B. stevensii and D. mutila, however, indicate the need for additional investigation into the relationship of these fungi.
Corresponding patterns of site quality, decline and tree growth in a sessile oak stand
Authors: Standová r T. , Somogyi Z.
Published: June 2007

This study focuses on two rarely studied aspects of oak decline: relations with site characteristics and effects on tree growth. The study was carried out in a 5.5 ha stand in Hungary which is strongly affected by oak decline. The nearly pure sessile oak (Quercus petraea) stand of mostly coppice origin was 90 years old at the beginning of the study. Within‐stand site heterogeneity was described by the herbaceous vegetation. Four ecological site types were distinguished by the species composition of herbs, and characterized by the ecological indicator values of the species. Tree growth between 1987 and 1993 was measured, and tree vigour was estimated from visual characteristics five times between 1987 and 1993. Potential volume increment of declining trees was estimated with the growth rates of healthy trees of the same size. Volume increment loss caused by oak decline was also assessed. Significant positive relationships were found between tree vigour and tree size and between tree vigour and tree growth. The growth of seriously declining trees dropped to almost one‐half of that of healthy ones. Growth reduction of living trees at the stand level amounted to 5.4%, whereas growth reduction of all trees, including those that died during the observation period, amounted to 19.9% of the potential growth. Tree size and growth were greater on better sites. A strong relationship was also found between tree vigour and site type, but sessile oak was more susceptible to decline at better sites.
A review of exapted resistance to diseases of Populus
Authors: Newcombe G.
Published: June 2007

The cultivation of hybrid poplar in the Pacific North‐west (PNW) has expanded in the last 15 years. Native Populus trichocarpa is susceptible to many pests and fungal pathogens but its interspecific hybrids were largely disease‐free until 1991 when Melampsora medusae f. sp. deltoidae first appeared in the region. Genetic analyses of resistance in the PNW, and elsewhere, reveal a pattern whereby genes for resistance are inherited in interspecific hybrids from the exotic, noncoevolved Populus parent. With some pathogen/poplar hybrid combinations, this resistance segregates in the F1 generation, but with others, only in the F2. Such exapted resistance is now known to occur in P. trichocarpa (versus the exotic, eastern North American rust species, M. medusae f. sp. deltoidae), in Populus deltoides (versus the Eurasian rust, Melampsora larici‐populina, the PNW population of Septoria populicola, and an undescribed PNW eriophyid mite), and in Populus maximowiczii (versus Melampsora occidentalis, and the PNW populations of Venturia populina, S. populicola, and Linospora tetraspora).
Resistance of new Belgian poplar clones to British isolates of the bacterial canker pathogen, Xanthomonas populi
Authors: Lonsdale D. , Rose J.
Published: June 2007

Forty‐nine new poplar clones, bred in Belgium and screened there for resistance to bacterial canker caused by Xanthomonas populi, were additionally screened in southern England, using British isolates of the bacterium. Thirty‐five of the test clones ranked better than the clone ‘Boelare’, which is already registered in the UK as an approved clone, and is regarded as having acceptable resistance. The registered clone ‘Ghoy’ was more susceptible, and outranked only four test clones. Preliminary measurements of canker length and stem girdling index showed differences between five bacterial isolates.
Melampsora and Marssonina pathogens of poplars and willows in New Zealand
Authors: Spiers A. G.
Published: June 2007

New Zealand has hosted three Melampsora species attacking poplars (Populus spp.), namely, Melampsora larici‐populina, Melampsora medusae and for a single season, Melampsora medusae‐populina, a unique interspecific hybrid. The predominant species, M. larici‐populina, over‐winters via larch and each year new races appear causing defoliation of previously rust‐resistant cultivars. Melampsora medusae also occurs in some seasons following over‐wintering on certain hosts or by aerial transport from Australia. Willows (Salix spp.) host four Melampsora species, Melampsora coleosporioides, Melampsora epitea var. epitea and two unidentified species attacking Salix viminalis and Salix daphnoides/Salix incana× open pollinated hybrids, respectively. The host range and pathogenicity of these species have remained static as no breakdown in host resistance has been observed. The anthracnose fungi, Marssonina brunnea and Marssonina castagnei on poplar, and Marssonina salicicola on tree willows occur throughout New Zealand. All three species can cause severe defoliation of susceptible cultivars in moist districts where annual rainfall exceeds 1000 mm. Although all form abundant microconidia during autumn, the Drepanopeziza states have never been observed in New Zealand. During an unusually wet summer (199–93), a new strain of Marssonina salicicoa appeared which defoliated the previously resistant cultivar, salix matsudana × salix alba cv. 1002 The importance of monitoring the morphological (conidial dimensions, DNA fingerprints) and physiological (host range and pathogenicity) attributes of local populations of Melampsora and Marssonina species is discussed.
Short rotation coppice willow in Northern Ireland since 1973: development of the use of mixtures in the control of foliar rust (Melampsora spp.)
Authors: McCracken A. R. , Dawson W. M.
Published: June 2007

A review is given of the use of clonal mixtures in the development of disease control strategies in short rotation coppice willow in Northern Ireland. Salix burjatica‘Korso’ had been grown successfully for over 10 years when, in 1985, Melampsora epitea var. epitea caused serious problems. Although fungicides were effective, their use was not practical for environmental and economic reasons. Therefore, in 1987 large scale field experiments were initiated to investigate the use of clonal mixtures as a disease control strategy. Increased yields were consistently recorded from mixed stands when compared to either the mean yield of component clones or the individual yields of any of the component clones grown in monoculture. Part of this increased yield was due to a reduction in the impact of rust disease. Investigations are currently being conducted on the effect of number of clones within a mixture, the best clones to use and the optimum planting density. It is essential that there is a range of susceptibilities to M. epitea var. epitea pathotypes within the components of the mixture.
Relative susceptibility of Salix clones to chrysomelid beetles: evidence from the Stott willow collection at Ness
Authors: Hodkinson I. D. , Flynn D. H. , Shackel S. C.
Published: June 2007

Willow species and hybrids growing in the Stott willow collection at Ness, UK, differed markedly in their susceptibility to leaf damage by insects, predominantly chrysomelid beetles, with the rank order of susceptibility remaining relatively constant over 2 years. Some species displayed a wide range of variation in susceptibility amongst clones; others very little. The range of susceptibilities of hybrids tended to mirror those of the parent species, with the hybrid usually sustaining leaf damage levels intermediate between those of the parents. Leaf damage in most species was higher on the lower leaf surface up to mid‐season, beyond which leaf perforation damage became prevalent. Damage levels did not appear related to leaf toughness. Apparent levels of leaf damage were lower in October versus July/August samples across nearly all species. Heavy leaf damage in one year did not appear to induce the production of leaves that were more resistant to insect attack in the following year.
Discoloration following bark stripping wounds on Fraxinus excelsior
Authors: Vasiliauskas R. , Stenlid J.
Published: June 2007

A total of 101 Fraxinus excelsior trees 8–32 cm in d.b.h. with bark stripping wounds caused by Alces alces and Cervus elaphus in Lithuania were cut, dissected and examined. The injuries ranged in age from 5 to 18 years, when the trees were 22–40 years old and were in the size range 6–24 cm d.b.h. For 5‐10 years old wounds, the mean length of associated wood discoloration was 804 × 201 cm, while in 16–18 years old wounds it was 912 × 144 cm. There was no correlation between wound age and extent of discoloration in the stems examined (r = 0.11). Tree d.b.h. and wound size (initial width × length) were correlated with the extent of discoloration (r = 0.43 and r = 0.20, respectively). The presence of complete wound occlusion had no significant effect on the length of columns of discoloration associated with wounds of 10 or more years old. The average occlusion rate during the first 10 years was 128 × 28 mm or 13 mm/year, correlating positively with the radial increment (r = 0.42). Amongst a total of 500 F. excelsior trees with wounds, 29 trees (5.8%) bore basidiomycete fruiting bodies. Most common was Phellinus punctatus, found on 12 (2.4%) stems, followed by Coniophora puteana (1.6%), Peniophora limitata (0.4%) and Datronia mollis (0.4%). Fungi most commonly isolated from discoloured wood were ascomycetes Phaeoacremonium rubrigenum, Phialophora malorum, Hypoxylon rubiginosum, Coniothyrium sporulosum, Libertella spp., Ophiostoma sp., and basidiomycetes Ischnoderma benzoinum, Ischnoderma resinosum, Tyromyces sp.