Arbuscular mycorrhizal fungal-induced alteration to root architecture in strawberry and induced resistance to the root pathogenPhytophthora fragariae

Three strawberry cultivars Elsanta, Cambridge Favourite and Rhapsody were inoculated with eitherGlomus fasciculatum orGlomus etunicatum and their growth compared with non-inoculated plants. The roots of all inoculated plants were 55 to 70% colonised after 98 days. Increases in both root and shoot dry weights were measured. Root architecture was also determined and increases in branching were evident in AMF colonised root systems. The remaining plants were then inoculated with the root pathogenPhytophthora fragariae and allowed to grow for a further 58 days before harvest. In two of the cultivars, Cambridge Favourite and Elsanta, AMF reduced root necrosis by approximately 60 and 30% respectively. Only in the least susceptible cultivar, Rhapsody, was no reduction measured in AMF colonised plants. There were differences in the control conferred by the two arbuscular mycorrhizal fungi and this suggests there may be practical benefits of inoculation. Relationships between the presence of roots of different orders, on inoculation with the pathogen, and subsequent necrosis provided a mechanism for identifying root-architecture driven alteration to susceptibility. Root system necrosis was positively correlated with the proportion of the root system made up of higher order roots (3° to 4°) in non-colonised plants and negatively correlated in AMF colonised plants. These data suggest that root-architecture changes are not important per se but factors expressed concurrently may be.     

Fungal ectomycorrhizal community and drought affect root hydraulic properties and soil adherence to roots ofPinus pinaster seedlings

Pinus pinaster seedlings were grown in a sandy dune soil either inoculated withHebeloma cylindrosporum or let to natural colonisation. Six months later, half of the seedlings of both treatments were subjected to a 3-week moderate drought. Root colonisation analysis showed that root tips were colonised to almost 100% independent of the inoculation. DNA determination of the ectomycorrhizal morphotypes showed that inoculated seedlings were extensively mycorrhized byH. cylindrosporum (more than 75%) whereas non-inoculated seedlings were mycorrhized by the exotic speciesThelephora terrestris (50%) andLaccaria bicolor (30%) and to a lesser extent byH. cylindrosporum (20%). Drought did not affect these frequencies. Total plant biomass was not affected by the mycorrhizal status or by drought but the root/shoot biomass ratio as well as the root/leaf surface area ratio were much lower in seedlings extensively colonised byH. cylindrosporum. Root hydraulic conductivity was higher in plants mainly mycorrhized byH. cylindrosporum, showing that this fungus improved the water uptake capacity of the root system as compared toT. terrestris and/orL. bicolor. This positive effect was also found under drought but to a lesser extent.H. cylindrosporum also increased the amount of root-adhering soil as compared to the other fungal symbionts, illustrating the performance of this association in aggregating sandy soil particles and developing the rhizosheath. The origin of the reduced root hydraulic resistance byH. cylindrosporum mycorrhization is discussed for the whole path including soil, soil-root interface and root cortex.     

Effect of vesicular-arbuscular mycorrhiza on survival,penetration and development of root-knot nematode in tomato

Summary Effect of mycorrhizal colonisation byGlomus fasciculatum on survival, penetration and development of the root knot nematodeMeloidogyne incognita in tomato was studied. The number of giant cells formed in mycorrhizal plants was significantly low. Mycorrhizal roots did not prevent the penetration by nematode larvae. Root extract from the mycorrhizal plants brought about 50% mortality of the nematode larvae in four days time.     

Detection of arbuscular mycorrhizal fungi within colonised roots of the Gramineae family members by nested-polymerase chain reaction (PCR)

In this study, it is aimed to asses the association of arbuscular mycorrhizal (AM) fungi within colonised rhizosphere of Gramineae family members through a survey by using nested- polymerase chain reaction method in Van province (Turkey). From 24 agro-ecological fields, a total of 82 samples belonging to Gramineae family were tested by molecular methods. The presence of Glomus intraradices and Glomus mosseae was ascertained in 10 plants belonging to eight different species by using fungus specific primers. Root colonisation ranged from 6 to 37% within rhizosphere of Gramineae family members and the average root colonisation by AM fungi was 22%.     

UV-B radiation affects flavonoids and fungal colonisation in <Emphasis Type="Italic">Fagopyrum esculentum</Emphasis> and <Emphasis Type="Italic">F. tataricum</Emphasis>

In the present study, we have evaluated the effects of increased UV-B radiation that simulates 17% ozone depletion, on fungal colonisation and concentrations of rutin, catechin and quercetin in common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tataricum). Induced root growth and reduced shoot:root ratios were seen in both of these buckwheat species after enhanced UV-B radiation. There was specific induction of shoot quercetin concentrations in UV-B-treated common buckwheat, whereas there were no specific responses for flavonoid metabolism in tartary buckwheat. Root colonisation with arbuscular mycorrhizal fungi significantly reduced catechin concentrations in common buckwheat roots, and induced rutin concentrations in tartary buckwheat, but did not affect shoot concentrations of the measured phenolics. Specific UV-B-related reductions in the density of microsclerotia were observed in tartary buckwheat, indicating a mechanism that potentially affects fungus-plant interactions. The data support the hypothesis that responses to enhanced UV-B radiation can be influenced by the plant pre-adaptation properties and related changes in flavonoid metabolism.     

Comparative root colonisation of strawberry cultivars Camarosa and Festival by Fusarium oxysporum f. sp. fragariae

Background and aims

Strawberry (Fragaria x ananassa) is a high-value crop worldwide. Fusarium oxysporum f. sp. fragariae causes rapid wilting and death of strawberry plants and severe economic losses worldwide. To date, no studies have been conducted to determine colonisation of either susceptible or resistant strawberry plants by F. oxysporum f. sp. fragariae, or whether plant colonisation by F. oxysporum f. sp. fragariae differs between susceptible and resistant cultivars.

Methods

Colonisation of strawberry plants by a pathogenic isolate of F. oxysporum f. sp. fragariae was examined both on the root surface and within root tissue of one resistant cv. Festival and one susceptible cv. Camarosa using light and scanning electron microscopy from 4?h to 7?d post inoculation (pi).

Results

Resistant cv. Festival significantly impeded the spore germination and penetration from 4 to 12 hpi and subsequent growth and colonisation by this pathogen until 7 dpi compared with susceptible cv. Camarosa. At 7 dpi, fungal colonisation in resistant cv. Festival remained mainly confined to the epidermal layer of the root, while in susceptible cv. Camarosa, hyphae not only had heavily colonised the cortical tissue throughout but had also colonised vascular tissues.

Conclusions

This study demonstrates for the first time that resistance of a strawberry cultivar to F. oxysporum f. sp. fragariae is a result of impedance of pathogen growth and colonisation both on the plant surface and within host tissues. Resistance mechanisms identified in this study will be of high value for breeding programmes in developing new disease-resistant cultivars to manage this serious strawberry disorder.     

Lack of arbuscular mycorrhizal colonisation in tea (<Emphasis Type="Italic">Camellia sinensis</Emphasis> L.) plants cultivated in Northern Iran

Soil and roots associated with different tea clones and nearby weeds (Veronica sp., Setaria sp., Salvia sp., Senecio sp. and Tripogon sp.) were sampled for arbuscular mycorrhizal fungi (AMF) in the tea gardens of Northern Iran. Spores were searched for in the soil and AMF colonisation determined microscopically and fatty acid signatures in roots was determined. Root samples from mycorrhizal and non-mycorrhizal clover were used as positive and negative controls. AMF spores were abundant in the tea garden soils; the genera Glomus and Acaulospora dominated. Microscopic observations of stained tea roots showed no sign of AMF. To confirm this, the roots were analysed for fatty acid signature compounds. The average level of PLFA 16:1ω5 as signature molecule for AMF in tea roots was 2 nmol g⁻¹ dry root, while the NLFA 16:1ω5 was not detectable. In mycorrhizal and non-mycorrhizal clover roots, the PLFA 16:1ω5 was 141and 5.74 nmol g⁻¹ dry root, respectively. In roots of weeds in tea plantations, the amount of PLFA 16:1ω5 was in the range 4.9 to 31.1 nmol g⁻¹ dry root. Thus, there was no evidence for AMF association in tea roots and weeds are thought to be the source of the spores in the soils. Finally, no mycorrhizal colonisation was found when tea plant seedlings were inoculated with AMF in pot cultures.     

Contribution of an arbuscular mycorrhizal fungus to the uptake of cadmium and nickel in bean and maize plants

Two experiments were carried out in pots with three compartments, a central one for root and hyphal growth and two outer ones which were accessible only for hyphae of the arbuscular mycorrhizal fungus, Glomus mosseae ([Nicol. and Gerd.] Gerdemann and Trappe). In the first experiment, mycorrhizal and nonmycorrhizal bean (Phaseolus vulgaris L.) plants were grown in two soils with high geogenic cadmium (Cd) or nickel (Ni) contents. In the second experiment, mycorrhizal and nonmycorrhizal maize (Zea mays L.) or bean plants were grown in a non-contaminated soil in the central compartment, and either the Cd- or Ni-rich soil in the outer compartments. In additional pots, mycorrhizal plants were grown without hyphal access to the outer compartments. Root and shoot dry weight was not influenced by mycorrhizal inoculation, but plant uptake of metals was significantly different between mycorrhizal and nonmycorrhizal plants. In the first experiment, the contribution of mycorrhizal fungi to plant uptake accounted for up to 37% of the total Cd uptake by bean plants, for up to 33% of the total copper (Cu) uptake and up to 44% of the total zinc (Zn) uptake. In contrast, Ni uptake in shoots and roots was not increased by mycorrhizal inoculation. In the second experiment, up to 24% of the total Cd uptake and also up to 24% of the total Cu uptake by bean could be attributed to mycorrhizal colonisation and delivery by hyphae from the outer compartments. In maize, the mycorrhizal colonisation and delivery by hyphae accounted for up to 41% of the total Cd uptake and 19% of the total Cu uptake. Again, mycorrhizal colonisation did not contribute to Ni uptake by bean or maize. The results demonstrate that the arbuscular mycorrhizal fungus contributed substantially not only to Cu and Zn uptake, but also to uptake of Cd (but not Ni) by plants from soils rich in these metal cations. Deceased 21 September 1996 Deceased 21 September 1996     

Fungal communities in mycorrhizal roots of conifer seedlings in forest nurseries under different cultivation systems, assessed by morphotyping, direct sequencing and mycelial isolation

Fungi colonising root tips of Pinus sylvestris and Picea abies grown under four different seedling cultivation systems were assessed by morphotyping, direct sequencing and isolation methods. Roots were morphotyped using two approaches: (1) 10% of the whole root system from 30 seedlings of each species and (2) 20 randomly selected tips per plant from 300 seedlings of each species. The first approach yielded 15 morphotypes, the second yielded 27, including 18 new morphotypes. The overall community consisted of 33 morphotypes. The level of mycorrhizal colonisation of roots determined by each approach was about 50%. The cultivation system had a marked effect on the level of mycorrhizal colonisation. In pine, the highest level of colonisation (48%) was observed in bare-root systems, while in spruce, colonisation was highest in polyethylene rolls (71%). Direct internal transcribed spacer ribosomal DNA sequencing and isolation detected a total of 93 fungal taxa, including 27 mycorrhizal. A total of 71 (76.3%) fungi were identified at least to a genus level. The overlap between the two methods was low. Only 13 (13.9%) of taxa were both sequenced and isolated, 47 (50.5%) were detected exclusively by sequencing and 33 (35.5%) exclusively by isolation. All isolated mycorrhizal fungi were also detected by direct sequencing. Characteristic mycorrhizas were Phialophora finlandia, Amphinema byssoides, Rhizopogon rubescens, Suillus luteus and Thelephora terrestris. There was a moderate similarity in mycorrhizal communities between pine and spruce and among different cultivation systems.Electronic supplementary material Supplementary material is available for this article at and accessible for authorised users     

Fungal root endophytes of the carnivorous plant Drosera rotundifolia

As carnivorous plants acquire substantial amounts of nutrients from the digestion of their prey, mycorrhizal associations are considered to be redundant; however, fungal root endophytes have rarely been examined. As endophytic fungi can have profound impacts on plant communities, we aim to determine the extent of fungal root colonisation of the carnivorous plant Drosera rotundifolia at two points in the growing season (spring and summer). We have used a culture-dependent method to isolate fungal endophytes and diagnostic polymerase chain reaction methods to determine arbuscular mycorrhizal fungi colonisation. All of the roots sampled contained culturable fungal root endophytes; additionally, we have provided molecular evidence that they also host arbuscular mycorrhizal fungi. Colonisation showed seasonal differences: Roots in the spring were colonised by Articulospora tetracladia, two isolates of uncultured ectomycorrhizal fungi, an unidentified species of fungal endophyte and Trichoderma viride, which was present in every plant sampled. In contrast, roots in the summer were colonised by Alatospora acuminata, an uncultured ectomycorrhizal fungus, Penicillium pinophilum and an uncultured fungal clone. Although the functional roles of fungal endophytes of D. rotundifolia are unknown, colonisation may (a) confer abiotic stress tolerance, (b) facilitate the acquisition of scarce nutrients particularly at the beginning of the growing season or (c) play a role in nutrient signalling between root and shoot.     

Factors affecting the colonisation of a root system by fluorescent Pseudomonads: The effects of water,temperature and soil microflora

The colonisation of a radish root system by strains ofPseudomonas fluorescens, selected for their ability to promote potato and radish growth under different environmental conditions is reported. In pot experiments colonisation of different parts of the root system was measured at different temperatures, in different watering regimes and in sterile and recropped soil. Root colonisation was extensive but populations were highest on the upper root system and their distribution throughout the root system was greatly affected by environmental factors. percolation of water through the soil and partial soil sterilisation enhanced colonisation but the effects of temperature and recropping were complex. Growth promotion was unpredictable and there was no simple relationship between PGPR colonisation and stimulation of plant growth.     

Root cortical anatomy is associated with differential pathogenic and symbiotic fungal colonization in maize

Root anatomical phenotypes vary among maize (Zea mays) cultivars and may have adaptive value by modifying the metabolic cost of soil exploration. However, the microbial trade‐offs of these phenotypes are unknown. We hypothesized that nodal roots of maize with contrasting cortical anatomy have different patterns of mutualistic and pathogenic fungal colonization. Arbuscular mycorrhizal colonization in the field and mesocosms, root rots in the field, and Fusarium verticillioides colonization in mesocosms were evaluated in maize genotypes with contrasting root cortical anatomy. Increased aerenchyma and decreased living cortical area were associated with decreased mycorrhizal colonization in mesocosm and field experiments with inbred genotypes. In contrast, mycorrhizal colonization of hybrids increased with larger aerenchyma lacunae; this increase coincided with larger root diameters of hybrid roots. F. verticillioides colonization was inversely correlated with living cortical area in mesocosm‐grown inbreds, and no relation was found between root rots and living cortical area or aerenchyma in field‐grown hybrids. Root rots were positively correlated with cortical cell file number and inversely correlated with cortical cell size. Mycorrhizae and root rots were inversely correlated in field‐grown hybrids. We conclude that root anatomy is associated with differential effects on pathogens and mycorrhizal colonization of nodal roots in maize.     

The mycorrhizal status of Phragmites australis in several polluted soils and sediments of an industrialised region of Northern Portugal

Roots of Phragmites australis from three polluted soils and sediments (a periodically flooded stream bank containing organic pollutants, a high-pH drying sedimentation pond and an acidic, periodically flooded sand polluted by industrial effluents) were sampled over a 1-year cycle of plant growth to assess the degree of colonisation by arbuscular mycorrhizal fungi (AMF). At the dry sedimentation pond, root samples of Juncus effusus and Salix atrocinerea were also taken to assess the presence of AMF throughout the year. Root colonisation was low (<5% root length colonised) but arbuscule presence peaked in P. australis during the spring and autumn prior to flowering. These changes in arbuscule abundance were also seen in a parallel greenhouse trial using seed taken from one of the sites. Roots of J. effusus contained mainly vesicular colonisation but arbuscule activity peaked during the winter months (December–March). S. atrocinerea roots were found to be ectomycorrhizal throughout the year but the fine feeder roots were colonised by AMF. The results confirm that semi-aquatics, like P. australis, can become arbuscular mycorrhizal but that this status changes during the year depending on soil moisture content and plant phenology. The influence of AMF in these polluted soils is uncertain but the potential exists to establish a more diverse plant ecosystem during the landscaping of these areas (phytostabilisation) by management of adapted plant and AMF ecotypes. Accepted: 6 November 2000     

Effect of root exudate fractions from P-deficient and P-sufficient onion plants on root colonisation by the arbuscular mycorrhizal fungus Gigaspora margarita

 The effect of root exudates from P-deficient onion on root colonisation by an arbuscular mycorrhizal fungus was examined. Onions (Allium cepa L.) were grown in solution culture at phosphorus concentrations of 0 (P0) and 2 (P2) mg P l^–1. Root exudates were collected and fractionated with Amberlite XAD-4 resin to give EtOH and water soluble fractions. Onions inoculated with the arbuscular mycorrhizal fungus Gigaspora margarita Becker & Hall were grown with or without (control) root exudates and exudate fractions in a growth chamber. After 24 days, arbuscular mycorrhiza levels and appressoria formation had increased in plants treated with P0-root exudate or the P0-EtOH fraction when compared to corresponding P2 treatments or control plants. P0 and P2 water-soluble fractions did not significantly affect either aspect of fungal development. These results suggest that hydrophobic compounds found in root exudates from P-deficient onion increase appressorium formation and, therefore, enhance mycorrhiza development. Accepted: 2 June 1998     

Pectic enzymes as a selective pressure tool forin vitro recovery of strawberry plants with fungal disease resistance

Summary A novel strategy in selecting strawberry (Fragaria xananassa L.) plants with resistance toRhizoctonia fragariae andBotrytis cinerea was developed. Purified pectic enzymes produced byR. fragariae were usedin vitro to select morphogenetic calluses. Both regenerated shoots and plants were testedin vitro andin vivo withR. fragariae andB. cinerea. Thein vitro resistance of shoots regenerated under selection pressure was confirmed byin vivo tests with runner plants either by root immersion in a suspension ofR. fragariae mycelium before potting the plants in sterile soil, or by spraying the leaves with several strains ofB. cinerea spores. The increase of resistance against pathogens was correlated to the increase of phenolic compounds, particularly orthodibydroxyphenolsAbbreviations MS (Murashige & Skoog 1962) - BAP (6-benzylaminopurine) - IBA (Indole-3-butyric acid) - PE (Pectic enzymes) - PDA (Potato dexstrose agar) - PG (Polygacturonase) - RU (Reducing Units) - SE (Standard Error) Communicated by N. Amrhein     

Growth,morphology and gas exchange of mycorrhizal and nonmycorrhizal Panicum coloratum L., a C4 grass species,under different clipping and fertilization regimes

Summary Root samples collected in grasslands of the Serengeti ecosystem, Tanzania, were found to be mycorrhizal and infection frequency was positively correlated with grazing intensity across sites. To examine the role of mycorrhizae in a grazing ecosystem, I analyzed the growth, morphology and gas exchange of mycorrhizal and nomycorrhizal plants of Panicum coloratum L. under different fertilization and clipping regimes. Both severe clipping and high nitrogen promoted more prostrate shoot growth but inhibited root growth. However, mycorrhizal infection promoted a prostrate shoot morphology and enhanced root growth. Photosynthesis was inhibited by clipping, however; at the most severe clipping and nitrogen regime, photosynthesis of the mycorrhizal plants was not affected whereas the largest inhibition of photosynthesis occurred in similarly treated nonmycorrhizal plants. Discussion of the putative roles of mycorrhizae in intensely grazed ecosystems is presented.     

Community analysis of arbuscular mycorrhizal fungi in a warm-temperate deciduous broad-leaved forest and introduction of the fungal community into the seedlings of indigenous woody plants

A community of arbuscular mycorrhizal (AM) fungi was investigated in a warm-temperate deciduous broad-leaved forest using a molecular analysis method. Root samples were obtained from the forest, and DNA was extracted from the samples. Partial 18S rDNA of AM fungi were amplified from the extracted DNA by polymerase chain reaction using a universal eukaryotic primer NS31 and an AM fungal-specific primer AM1. After cloning the PCR products, 394 clones were obtained in total, which were divided into five types by restriction fragment length polymorphism (RFLP) with HinfI, RsaI, and Hsp92II. More than 20% of the clones were randomly selected from each RFLP type and sequenced. Phylogenetic analysis showed that all the obtained clones belonged to Glomus but could not be identified at species level. Topsoil of the forest containing plant roots was inoculated to nonmycorrhizal seedlings of indigenous woody plants, Rhus javanica var. roxburghii and Clethra barvinervis, to introduce the community of AM fungi into the seedlings. Among these five RFLP types, four types were detected from both seedlings, which indicates that the AM fungal community in the forest root samples was introduced at least partly into the seedlings. Meanwhile, an additional four types that were not found in the forest root samples were newly detected in the seedlings, these types were closely related to one another and close to G. fasciculatum or G. intraradices. It is expected that a community of indigenous diverse AM fungi could be introduced into target fields by planting these mycorrhizal seedlings.     

A global assessment using PCR techniques of mycorrhizal fungal populations colonising<Emphasis Type="Italic"> Tithonia diversifolia</Emphasis>

Tithonia diversifolia (Mexican sunflower) is a shrub commonly used as a green manure crop in Central and South America, Asia and Africa as it accumulates high levels of phosphorus and other nutrients, even in depleted soils. In root samples collected from the global distribution of Tithonia, we examined the degree of mycorrhizal colonisation and estimated the families of associated arbuscular mycorrhizal (AM) fungi. No colonisation by ectomycorrhizas was found. The degree of colonisation by AM fungi was on average 40%, but ranged between 0 and 80%. No mycorrhizal colonisation was found in the samples collected from the Philippines or in one each of the Rwandan and Venezuelan samples. Throughout its global distribution (Costa Rica, Nicaragua, Indonesia, Honduras, Mexico, Kenya and Rwanda), Tithonia forms mainly associations with Glomaceae. Only in one location in Nicaragua were associations with another family (Acaulosporaceae) found.     

Reduced growth of autumn-sown wheat in a low-P soil is associated with high colonisation by arbuscular mycorrhizal fungi

Autumn-sown wheat (Triticum aestivum) was studied over two seasons in south-eastern Australia, on a low-P soil where indigenous arbuscular mycorrhizal fungi (AMF) were known to provide little nutritional benefit to crops. It was hypothesised that AMF would be parasitic under these circumstances. Shoot dry mass and water soluble carbohydrate (WSC) reserves in roots and shoots were measured for wheat grown with or without P-fertiliser, in plots where crop sequences had produced either high or low colonisation by AMF. Application of P-fertiliser greatly increased crop growth and decreased colonisation by AMF. At tillering, colonisation by AMF ranged from 24 to 66% of root length when no P was applied and from 11 to 32% when P was applied. At each P-level, high colonisation correlated with reductions of around 20% in stem and root WSC concentrations (first season) or shoot WSC content and shoot dry mass (much drier second season). Impacts on yield were not significant (first season) or largely masked by water-stress and frost (second season). While the major fungal root diseases of the region were absent, interactions between crop sequence and other unknown biotic constraints could not be discounted. The results are consistent with the parasitic impacts of colonisation by AMF being induced primarily through the winter conditions experienced by the crops until anthesis. It is concluded that wheat in south-eastern Australia may benefit from reduced colonisation by AMF, which could achieved through selected crop sequences or, perhaps, targeted wheat breeding programs.     

Impact of <Emphasis Type="Italic">Heterobasidion</Emphasis> root-rot on fine root morphology and associated fungi in <Emphasis Type="Italic">Picea abies</Emphasis> stands on peat soils

We examined differences in fine root morphology, mycorrhizal colonisation and root-inhabiting fungal communities between Picea abies individuals infected by Heterobasidion root-rot compared with healthy individuals in four stands on peat soils in Latvia. We hypothesised that decreased tree vitality and alteration in supply of photosynthates belowground due to root-rot infection might lead to changes in fungal communities of tree roots. Plots were established in places where trees were infected and in places where they were healthy. Within each stand, five replicate soil cores with roots were taken to 20 cm depth in each root-rot infected and uninfected plot. Root morphological parameters, mycorrhizal colonisation and associated fungal communities, and soil chemical properties were analysed. In three stands root morphological parameters and in all stands root mycorrhizal colonisation were similar between root-rot infected and uninfected plots. In one stand, there were significant differences in root morphological parameters between root-rot infected versus uninfected plots, but these were likely due to significant differences in soil chemical properties between the plots. Sequencing of the internal transcribed spacer of fungal nuclear rDNA from ectomycorrhizal (ECM) root morphotypes of P. abies revealed the presence of 42 fungal species, among which ECM basidiomycetes Tylospora asterophora (24.6 % of fine roots examined), Amphinema byssoides (14.5 %) and Russula sapinea (9.7 %) were most common. Within each stand, the richness of fungal species and the composition of fungal communities in root-rot infected versus uninfected plots were similar. In conclusion, Heterobasidion root-rot had little or no effect on fine root morphology, mycorrhizal colonisation and composition of fungal communities in fine roots of P. abies growing on peat soils.