Antifungal effect of bark extracts from some European tree species     

Gry Alfredsen  Halvor Solheim  Rune Slimestad 《European Journal of Forest Research》2008,127(5):387-393

The inhibitory effect of methanol bark extracts from six deciduous and three coniferous European tree species were bioassayed against eight fungi from the different damage categories, brown rot, white rot, canker and blue-stain. This is the first report providing data on the antifungal activity of several Europaen tree species against fungi within these damage categories. Generally the decay fungi were more inhibited by the bark extracts than the blue-stain fungi, while the lowest inhibition was found among the cancer fungi. The main pattern found between the fungal groups in relation to the bark extracts in this study is believed to be caused by the route of ingress. Acer platanoides bark extract proved to be the most efficient bark extract tested, significantly reducing the growth rate of all tested fungi. Betula pubescens bark extract generally gave the weakest reduction in growth rate. In this study, the conifer bark extracts were in general more active against the canker and blue stain ascomycete fungi than the deciduous trees extracts.  相似文献   

Etiology and real-time polymerase chain reaction-based detection of gremmeniella- and phomopsis-associated disease in norway spruce seedlings     

Børja I  Solheim H  Hietala AM  Fossdal CG 《Phytopathology》2006,96(12):1305-1314

ABSTRACT In spring 2002, an unusual disease outburst was recorded on Norway spruce seedlings in southeast Norway. Extensive damage was recorded on 1- and 2-year-old Norway spruce seedlings that either had wintered in nursery cold storage or had been planted out in autumn 2001. The damage was characterized by leader shoot dieback and stem necroses on the upper or lower part of the shoot from 2001. Gremmeniella abietina and a Phomopsis sp. frequently were isolated from the diseased seedlings. Internal transcribed spacer (ITS) ribosomal (r)DNA sequence analysis and random amplified microsatellites profiling indicated that the G. abietina strains associated with diseased nursery seedlings belonged to the large-tree type (LTT) ecotype of the European race of G. abietina var. abietina, and inoculation tests confirmed their pathogenicity on Norway spruce. Based on ITS rDNA sequence analysis, the Phomopsis strains associated with diseased seedlings did not represent any characterized Phomopsis spp. associated with conifers. The Phomopsis sp. was not pathogenic in inoculation tests, indicating that it may be a secondary colonizer. ITS-based real-time polymerase chain reaction assays were developed in order to detect and quantify G. abietina and Phomopsis in the nursery stock. We describe here the G. abietina-associated shoot dieback symptoms on Norway spruce seedlings and conclude that the unusual disease outburst likely was related to the G. abietina var. abietina epidemic caused by the LTT on large Scots pines in 2001.  相似文献   

Induced resistance of Norway spruce,variation of phenolic compounds and their effects on fungal pathogens     

P. C. Evensen  H. Solheim  K. Hiland  J. Stenersen 《Forest Pathology》2000,30(2):97-108

Three clones of Norway spruce (Picea abies) were studied for their response to mass‐inoculation with the blue‐stain fungus Ceratocystis polonica. The effect of different pretreatments (fungal inoculation and wounding) before mass‐inoculation was investigated for their possible role in an acquired resistance reaction. Pretreated trees showed enhanced resistance to the subsequent mass‐inoculation relative to control trees that received no pretreatment. Furthermore, the fungal colonization of inoculated trees was less than that of wounded trees. The phenolic content of the bark, analysed by RP‐HPLC, was compared in trees receiving different treatments. Trees inoculated with C. polonica had higher average concentration of (+)‐catechin, taxifolin and trans‐resveratrol than wounded trees. Both inoculated and wounded trees had higher average concentrations of these compounds than control trees. The effect of the phenolic extract of Norway spruce bark on the growth of the root rot fungus Heterobasidion annosum and the blue‐stain fungi C. polonica and Ophiostoma penicillatum were investigated in vitro. Heterobasidion annosum was not negatively affected, and the extracts had fungistatic effects on the blue‐stain fungi. The growth of O. penicillatum was more inhibited than the growth of the more aggressive C. polonica.  相似文献   

Storm-induced tree resistance and chemical differences in Norway spruce (Picea abies)     

Tao Zhao  Halvor Solheim  Bo L?ngstr?m  Anna-Karin Borg-Karlson 《Annals of Forest Science》2011,68(3):657-665

Introduction   

Windstorm is one of the most destructive environmental disturbance factors on forests, but its influence on conifer defense chemistry and susceptibility to insects and diseases is not well understood.  相似文献   

Dutch elm disease has currently a low incidence on wych elm in Norway     

H. Solheim  R. Eriksen  A. M. Hietala 《Forest Pathology》2011,41(3):182-188

A rapid increase in the frequency of Dutch elm disease (DED), a wilting disease of elm trees caused by bark‐beetle vectored fungi, was observed in the early 1990s on several wych elm stands around Oslofjord, southern Norway. To examine the current status of the disease and its impacts on elm population, disease frequency and size distribution of elms were recorded at four locations. Northern parts of Lier, a municipality most affected by DED in Norway 15 years ago, showed in the survey season 4% disease frequency, whereas 13.8% of trees were dead, the dead trees having accumulated over several years in the unmanaged stands. In southern parts of the municipality the mean disease and death percentages were 1.9 and 2.4%. Compatible with their low disease incidence in early 1990s, the other two areas now examined, municipality of Larvik and district of Grenland, showed comparably low frequency of DED. Northern part of Lier showed significantly higher overall density of elm trees per hectare than the other examined areas, and also the small elms below 5 cm in d.b.h. were most frequent in this region. In contrast, the density of large trees was lower in northern Lier than in the other examined areas. These data suggest that regeneration of the tree is not prohibited owing to the disease but that the large trees have been locally reduced in frequency as a result of DED. The superior general density of elm trees in northern Lier, owing to the exceptionally rich soil in the warm southern slopes of the region,> may have contributed to the rapid increase of DED in the area 15 years ago and to the subsequent settlement of the disease outbreak as a chronic stage.  相似文献   

Hymenoscyphus species associated with European ash1     

A. M. Hietala  H. Solheim 《EPPO Bulletin》2011,41(1):3-6

The causative agent of dieback on European ash (Fraxinus excelsior) was first described as Chalara fraxinea based on cultural morphology because no sexual stage of the fungus was known. Later, based on culturing of ascospores of a candidate teleomorph, morphological comparison and nuclear ribosomal internal transcribed spacer sequencing, the sexual stage of C. fraxinea was assigned as Hymenoscyphus albidus, a native and widespread species in Europe. Recently, the morphological species concept of H. albidus was shown to cover two species that cannot be separated from each other based on teleomorph characters, but which can be distinguished by several DNA markers. As a result, the strains causing ash dieback were reassigned as H. pseudoalbidus. The closely related H. albidus is presumably a non‐pathogenic endophyte, but pathogenicity tests to confirm this hypothesis have not yet been performed. Genotyping of herbarium specimens has shown that H. pseudoalbidus was present in Switzerland for at least a decade prior to the epidemic outbreak in Europe. The origin of the ash dieback pathogen, and the general importance of correct pathogen identification to development of effective disease control, are discussed.  相似文献   

Phenolic contents and antioxidant activities in covered whole-grain flours of Norwegian barley varieties and in fractions obtained after pearling     

Ann Katrin Holtekjølen  Stefan Sahlstrøm  Svein Halvor Knutsen 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(1):67-74

Abstract

Phenolic contents and corresponding antioxidant activities were studied in covered whole-grain flours of Norwegian barley varieties and in two different pearling fractions. In covered whole-grain flours the summarized amount of phenolics (Σ-P) ranged from 481–676 mg gallic acid equivalent (GAE)/100 g dry matter (DM) and the corresponding total antioxidant activities (Σ-FRAP) between 6.1–8.7 mmol Fe^{3 +}/100 g DM. About 50% of the phenolics in these samples were easily extractable (free). Upon pearling a general decrease in both Σ-P and Σ-FRAP was seen in the pearled samples, while the ratio between free and bound phenolics was similar or increased to those in the covered whole-grain samples. The hulls had the highest Σ-P and Σ-FRAP and were dominated by bound phenolics. Despite accounting for only 10–20% of the total grain weight, the hulls typically contributed to 45% of the total antioxidant capacity measured in the covered whole-grain flours. Pearling makes it possible to obtain barley fractions with different amounts of phenolics, different ratios of free and bound phenolics, and thus different antioxidant activities.  相似文献   

Induction of disease resistance in Norway spruce (Picea abies) by necrotizing fungi     

P. Krokene†  H. Solheim  E. Christiansen 《Plant pathology》2001,50(2):230-233

Norway spruce trees ( Picea abies ) preinoculated with the root rot fungus Heterobasidion annosum , Nectria fuckeliana or a pathogenic strain of the blue-stain fungus Ceratocystis polonica were more efficiently protected against a subsequent massive inoculation with pathogenic C. polonica than trees pretreated with nonpathogenic C. polonica or sterile malt agar. Control trees that received no pretreatment were extensively colonized by the mass inoculation. There was a strong negative correlation between the length of the phloem necroses induced by the pretreatment inoculations and the extent of host symptoms caused by mass inoculation with pathogenic C. polonica . The degree of induced resistance in Norway spruce thus depended on the amount of host tissue destroyed by the pretreatment.  相似文献   

Genetic parameters for wood quality traits and resistance to the pathogens Heterobasidion parviporum and Endoconidiophora polonica in a Norway spruce breeding population     

Arne Steffenrem  Halvor Solheim  Tore Skrøppa 《European Journal of Forest Research》2016,135(5):815-825

  相似文献   

Real-time PCR-based monitoring of DNA pools in the tri-trophic interaction between Norway spruce, the rust Thekopsora areolata, and an opportunistic ascomycetous Phomopsis sp     

Hietala AM  Solheim H  Fossdal CG 《Phytopathology》2008,98(1):51-58

The difficulty in subculturing biotrophic fungi complicates etiological studies related to the associated plant diseases. By employing internal transcribed spacer rDNA-targeted quantitative real-time polymerase chain reaction, we now show that the heteroecious rust Thekopsora areolata, commonly associated in natural conditions to sapling shoots and cones of Norway spruce and leaves of wild bird cherry, frequently infects nursery-grown seedlings of the conifer. A spatial sampling scheme was used to investigate seedlings and saplings of Norway spruce showing phloem necrosis: the highest concentration of DNA of T. areolata was recorded in the area with necrotic phloem. The separate analysis of bark and wood tissues suggested that the initial spread of the rust to healthy tissues neighboring the infection site takes place in the bark. A Phomopsis species found to coexist with T. areolata in several seedlings showed very high DNA levels in the upper part of the lesion, and even in the visually healthy proximal tissues above the lesions, which indicates that the ascomycete, most probably a secondary invader following primary infection by T. areolata, has a latent stage during early host colonization. We hypothesize that this hemibiotrophic mode of infection contributes to the successful coexistence of Phomopsis with a biotrophic rust.  相似文献