Microdochium Bolleyi Research Articles

Identification of Microdochium bolleyi Associated with Basal Rot of Creeping Bent Grass in Korea

Symptoms of basal rot occurred sporadically on creeping bent grasses growing at a golf course in Hampyeong, Korea in April 2007. Ten isolates of Microdochium sp. were obtained from leaves and crowns of the diseased bent grasses. All isolates were identified as Microdochium bolleyi based on morphological, cultural, and molecular characteristics. This is the first report on M. bolleyi associated with basal rot on creeping bent grass in Korea.

Bioactive Isocoumarins Isolated from the Endophytic Fungus Microdochium bolleyi

Three new isocoumarin derivatives ( 2- 4) were isolated together with monocerin ( 1) from Microdochium bolleyi, an endophytic fungus from Fagonia cretica, a herbaceous plant of the semiarid coastal regions of Gomera. Compounds 2 and 3 are both 12-oxo epimers of 1, and 4 is a ring-opened derivative of 1. The structures were elucidated by detailed spectroscopic analysis and comparison with reported data. The absolute configurations were determined by a modified Mosher's method. Compounds 1, 3, and 4 showed good antifungal, antibacterial, and antialgal activities against Microbotryum violaceum, Escherichia coli, Bacillus megaterium, and Chlorella fusca. Compound 2 was moderately antifungal and antialgal.

EFFECT OF FILM PACKAGING ON PHYTOPATHOLOGICAL AND PHYSIOLOGICAL PROCESSES OF FRESH-CUT WHITE ASPARAGUS (ASPARAGUS OFFICINALIS L.) DURING STORAGE

The effect of polypropylene-film (PP-film) and P-Plus-film on changes in fungal growth, related changes in the carbohydrate pattern (fructose, glucose and sucrose) of film wrapped peeled asparagus and changes in the oxygen and carbon dioxide concentrations within the film packaging was measured at harvest and after 3 days of shelf life (20°C). At harvest, endophytic contamination with Idriella bolleyi (30%), Cladosporium macrocarpum (3.3%), Verticillium spp. (1.7%), Penicillium spp. (1.7%) and Fusarium oxysporum (1.7%) was found. After three days of storage, the development of fungi was inhibited, possibly as a result of the decline in the oxygen concentration in the P-Plus-film (8.2%) and in PP-film (0.18%). Idriella bolleyi decreased by 8.3% in PP-film packaging and by 16.7% in the P-Plus-film indicating a better adaptation to varying physiological conditions in postharvest. The different film packaging material accounted for the variability in oxygen concentration (98%), fungal growth (93%), glucose (93%) and fructose (81%). Correlations were found between fungal growth and sucrose concentration (r=0.65, P<0.05), oxygen concentration (r=0.62, P<0.05), carbon dioxide concentration (r=-0.62, P<0.05). The development of fungi was inhibited by the gaseous composition within the film-packaging unit and/or by the limited source of carbohydrates available. Furthermore, the non-pathogenic fungus Idriella bolleyi, a known antagonist, might have been inhibited by the growth of Cladosporium spp., Fusarium spp., Penicillium spp. and Verticillium spp.

Fungal populations in roots and crowns of common and durum wheat in Saskatchewan

A survey of fungal populations in discolored subcrown internodes and crown or lower-culm tissue of common and durum wheat was conducted throughout Saskatchewan in 1998 and 1999. The fungus with the highest percentage of isolation, and found in the greatest number of fields, was Bipolaris sorokiniana, followed by Microdochium bolleyi and the Fusarium spp. associated with fusarium head blight. Fusarium graminearum was isolated at low frequencies, and only in eastern areas of the province affected by fusarium head blight. Bipolaris sorokiniana appeared to be favoured in the drier Brown soil zone, whereas Fusarium spp. were in general found at higher levels in the Dark-Brown and Black or Dark-Gray soil zones. Despite marked environmental differences between the 2 years of this study, there were no consistent differences between years in the presence of the most commonly isolated fungi, and the ranking of fungi based on their isolation frequency. There was a negative correlation between isolations of B. sorokiniana and each of the Fusarium spp., whereas the severity of discoloration in crowns or lower culms was positively correlated with the presence of Fusarium spp. in 1999. In some cases, Fusarium spp. were more commonly isolated from durum than common wheat. This is the first time that Fusarium spp. in underground and crown cereal tissue is identified to the species level across Saskatchewan. Based on the levels of Fusarium spp. found in subcrown internodes and crowns or lower culms, it is suggested that the role played by these infected plant parts in the epidemiology of fusarium head blight in Saskatchewan be examined

In vivo observation of conidial germination at the oxic–anoxic interface and infection of submerged reed roots by Microdochium bolleyi

The underground plant parts of reed ( Phragmites australis) growing in anoxic soil of the littoral zone of lakes are provided with oxygen via an aerenchyma. Some of this oxygen is released into the rhizosphere, which creates a potential microhabitat for aerobic fungi. Although fungal endophytes of reed have been shown to occur also in roots of flooded habitats, it is not known whether or how fungi can infect roots growing in anoxic or hypoxic soil. To study fungal infection of reed roots in the laboratory, we developed an incubation chamber to expose reed roots to conidia of Microdochium bolleyi in an anoxic agar medium and to observe fungal infection in vivo. Germination rates of conidia were high close to living roots, but decreased to zero in anoxic areas of the chamber. Conidial germ tubes located up to 200 μm from the roots grew preferentially towards the living roots. Conidia also germinated close to air-filled Teflon tubes and exhibited germ-tube tropism, but not as distinctly as on living reed roots. Conidia did not germinate in the neighbourhood of dead roots in anoxic agar. However, in the aerated margin of the incubation chamber most conidia germinated and exhibited tropic growth towards dead roots. Penetration of M. bolleyi through several cell layers of living roots was observed in cryo-microtome sections. Penetration was significantly deeper with illuminated plants than with plants kept in the dark; in some cases even the stele was reached. This is the first observation of oxygen released from roots to support growth of an aerobic fungus and of fungal penetration into root tissue in an anoxic environment.

Seed Treatment of Barley with Idriella bolleyi causes Systemically Enhanced Defence against Root and Leaf Infection by Bipolaris sorokiniana

Inoculation of barley seed with the saprophytic fungus Idriella bolleyi caused systemically improved resistance on both leaves and roots of young plants to subsequent infection with the necrotrophic fungus Bipolaris sorokiniana . Lesion sizes were reduced by up to 50% as a result of the seed treatment. Seed and root inoculation with I. bolleyi induced biochemical defence responses in the plants as shown by slight accumulation of pathogenesis-related (PR) proteins, but the accumulation was not as great as when the roots were inoculated with B. sorokinina . Conidia of I. bolleyi applied to seed survived well during storage, with no significant reduction in colony forming units (CFUs) occurring at 15°C after 2 months. However, storage at 28°C decreased the viability of the applied conidia. The fungus colonized the seed and roots during field conditions as indicated by high numbers of CFUs. Two months after sowing, frequencies of I. bolleyi were higher on plants treated with the fungus than on control plants where colonization occurred naturally from field soil. The implications of the results are discussed in relation to earlier reports of biological control of cereal root diseases by I. bolleyi and induced resistance.

The occurrence of barley root diseases in different agri-ecological zones of Syria

A survey was conducted to determine the occurrence of root diseases and the identity of causal agents on barley grown in northern agricultural areas of Syria in 1992 and 1993. In 1992, 20 plants with at least 1 cm long subcrown internodes were randomly selected from each of 53 fields when plants were between flowering and maturity. In 1993, 50 plants were selected from each of 72 fields. In addtion, four wheat fields were sampled in 1993. Plants were visually rated for disease severity on the subcrown internode. Fungal cultures were isolated from root tissues by plating on selective and general media. Isolates were tested for pathogenicity using a seedling bioassay, and representative pathogens were identified to the species level. Root rot was more severe in the drier agricultural zones and disease severity increased with crop maturity. There was a weak negative association between disease severity and the number of tillers per plant. The most prevalent pathogens in both years were Microdochium nivale (average of 43%), Cochliobolus sativus (35%), red-pigmented Fusaria (13%), and Microdochium bolleyi (8%). More than 80% of the C. sativus and M. nivale isolates, and less than 20% of the Fusarium spp. and M. bolleyi isolates, were pathogenic. Cochliobolus sativus was most common in the drier areas, whereas M. nivale was most common in the wetter areas, particularly from the northwest region. This paper is the first report of M. nivale and M. bolleyi on barley and Gaeumannomyces graminis var. tritici on wheat in Syria. Other root disorders (pests) found included cyst-forming nematodes and Porphyrophora tritici.

Identity and Pathogenicity of Fungi Associated with Root and Crown Rot of Soft Red Winter Wheat Grown on the Upper Coastal Plain Land Resource Area of Mississippi

Seedling stand, disease severity and fungal incidence were determined from untreated ‘Wakefield’ soft red winter wheat planted on a Leeper silty clay loam in field tests conducted at the Mississippi Agricultural and Forestry Experiment Station, Plant Science Research Center, Mississippi State University, Starkville, Mississippi during the 1996–97 and 1997–98 growing seasons. Seedling stand was reduced by 40% each year in plots established with untreated seed. Cochliobolus sativus was the most frequently isolated fungus. Fusarium acuminatum, Fusarium equiseti and Fusarium solani were the most prevalent Fusarium spp. Seven other Fusarium spp. and 23 species of other fungal genera were isolated. Pathogenicity tests with three isolates each of C. sativus, Cochliobolus spicifer, F. acuminatum, F. solani, F. equiseti, Fusarium compactum, Embellisia chlamydospora and Microdochium bolleyi were performed in test tube culture and two isolates each of C. sativus, C. spicifer, F. acuminatum, E. chlamydospora and M. bolleyi under greenhouse conditions. In test tubes and in the greenhouse, seedlings infected with isolates of C. sativus developed seedling blight, discoloration and necrosis, primarily in seminal roots and crowns. In the greenhouse, C. sativus induced lesions on the lower leaf sheath and reduced seedling height, seedling emergence, dry and fresh weight of roots and shoots. Isolates of F. acuminatum, F. solani, F. equiseti, F. compactum, E. chlamydospora and M. bolleyi induced slight to moderate orange to light‐brown discoloration of crown and seminal roots in test tubes. Cochliobolus spicifer isolates had the most pre‐emergence activity, inducing black root discoloration and root pruning of wheat seedlings and reducing seedling emergence, root fresh weight and shoot dry weight. In the greenhouse, F. acuminatum reduced seedling height, seedling emergence and root and shoot dry weights. Microdochium bolleyi and E. chlamydospora reduced fresh and dry weight of roots, plant emergence and shoot dry weight. Fusarium acuminatum and C. spicifer reduced the growth rate of wheat seedlings. All fungi evaluated showed increased disease severity compared to the untreated control. The high frequency of isolation of C. sativus from crown and root tissues can be partially explained by the dry, warm conditions during the early stages of wheat seedling development in the Upper Coastal Plain Land Resource Area of Mississippi.

Anti-fungal properties of chitinolytic dune soil bacteria

Anti-fungal properties of chitinolytic soil bacteria may enable them to compete successfully for chitin with fungi. Additionally, the production of chitinase may be part of a lytic system that enables the bacteria to use living hyphae rather than chitin as the actual growth substrate, since chitin is an important constituent of most fungal cell walls. Lysis of living fungal hyphae by chitinolytic bacteria has been reported frequently; however, these reports nearly always deal with bacteria that had been selected because of their mycolytic properties. Our main objective was to get a better understanding of the relationship between chitinolytic and anti-fungal properties of bacteria that occur naturally in soils, i.e. without artificial selection. Three inner dune sites, two of which were lime-poor and one lime-rich, along the Dutch coast were selected for this study. Bacteria that were able to degrade colloidal chitin in water–agar comprised 0.2–5.7% of the total amount of culturable bacteria of these dune sites. Pseudomonas spp. were the most abundant culturable, chitin-degrading bacteria at the lime-poor sites, whereas Xanthomonas spp. and Cytophaga spp. were important at the lime-rich site. Chitinolytic actinomycetes were relatively abundant at all three sites. Chitinolytic and non-chitinolytic bacteria were randomly selected and tested for the possession of antagonistic activities against fungal dune strains [ Chaetomium globosum, Fusarium culmorum, F. oxysporum, Idriella (Microdochium) bolleyi, Mucor hiemalis, Phoma exigua, Ulocladium sp.]. The tests were done using water–agar to simulate the energy-limiting conditions that bacteria will encounter in dune soils. The percentage of bacterial isolates that were antagonistic against these fungi was considerably higher for chitinolytic strains than for non-chitinolytic ones. Therefore, the possible involvement of chitinase with respect to the inhibition of fungal growth was studied in more detail. It appeared that in many cases the inhibition of fungal growth was not accompanied by bacterial chitinase production. There was also no clear relationship between the activity of other cell wall degrading enzymes ( β-1,3-glucanase and protease) and antagonism. Chitinolytic bacteria had selective rather than general anti-fungal properties, which were not necessarily related to differences in general susceptibility of the fungi towards antagonism. These results may indicate that antibiotics were involved in the antagonistic activities of chitinolytic bacteria against fungi. Only growing fungi were antagonized by the chitinolytic bacteria; none of the chitinolytic bacteria were able to lyse existing mycelium of any of the fungi. The relevance of the results for the ecology of chitinolytic soil bacteria is discussed.

Infection of Adventitious Roots of Agrostis palustris by Idriella bolleyi1

AbstractSeven isolates of Idriella bolleyi obtained from adventitious roots of Agrostis palustris displaying symptoms of thinning, low vigor, and death of turf in a random, nondescript pattern were evaluated for their ability to infect adventitious roots of A. palustris under high and low temperature regimes and to affect plant growth and symptom expression. All isolates of I. bolleyi infected roots under high and low temperature regimes and all but one isolate decreased shoot and root dry weight. Isolate IB‐2 decreased dry weight under low temperatures, but not under high temperatures. Stolon growth of root‐inoculated plants increased or remained unchanged among plants subjected to high temperature; stolon growth decreased on plants subjected to low temperature. Most isolates of I. bolleyi decreased the chlorophyll content of leaves of plants subjected to high temperature; chlorophyll content of leaves of inoculated plants subjected to low temperature remained unchanged. Hyphal growth was observed on inoculated adventitious roots and was accompanied by dark clusters of fungal cells and chlamydospores on the epidermis and cessation structures within the cortex. Vascular tissues were not penetrated by I. bolleyi. It was concluded that I. bolleyi can infect adventitious roots of A. palustris as a minor root pathogen and alter root and shoot growth.

Interaction Specificity of the Biocontrol AgentSporothrix flocculosa: A Video Microscopy Study

Sporothrix flocculosa, a biocontrol agent reported to act by antibiosis, had a differential effect against four target fungi, based on video microscopy records of the interactions. Two of the fungi, Botrytis cinerea and Cladosporium cucumerinum, were very susceptible and reacted ahead of the advancing colony of S. flocculosa. Typical reactions included retraction of the plasmalemma, aggregation of the cytoplasm, and cell death. When S. flocculosa was inoculated directly onto a colony of B. cinerea, conidia of the biocontrol agent developed toward the pathogen, and the hyphae of B. cinerea ceased cytoplasmic activity and became highly vacuolated within 8 h. Individual conidia of S. flocculosa produced several germ tubes, but did not attack live, necrotic, or dead hyphae of the pathogen. The other two tested fungi, Fusarium oxysporum f. sp. radicis-lycopersici and Idriella bolleyi, were unaffected by the presence of S. flocculosa. These results correlated with previous observations that C. cucumerinum and F. oxysporum f. sp. radicis-lycopersici were, respectively, sensitive and tolerant against purified toxins of S. flocculosa. This indicates that the host range of S. flocculosa is dictated by host sensitivity to its toxins.

Biocontrol of seedling diseases of barley and wheat caused by Fusarium culmorum and Bipolaris sorokiniana: effects of selected fungal antagonists on growth and yield components

The purpose of this study was to verify, under natural conditions, biological control effects obtained in a former screening programme against Fusarium culmorum. The most successful antagonists against seedborne Fusarium culmorum and Bipolaris sorokiniana were isolates of Chaetomium sp., Idriella bolleyi and Gliocladium roseum. These results were also obtained when the antagonists were applied to B. sorokiniana‐infected barley sown in field soil in pots. In field experiments, G. roseum gave the best control of F. culmorum in winter wheat. One month after sowing, germination increased by 170%, the disease index decreased by 73% and plant dry weight increased by 25%, compared to untreated plots. At harvest, the number of tillers per row was found to have increased by 53%, yield had increased by 160% and the 1000‐grain weight had increased by 4%. For all evaluated parameters the effect was significantly different from the untreated plots and not significantly different from the plots treated with the fungicide, Sibutol LS 280. I. bolleyi gave a lower but still significantly effective control, when evaluated for disease index and numbers of tillers per row, while Chaetomium sp. did not show any reduction in the disease. Furthermore, in field experiments using barley infected with B. sorokiniana, a significant effect of G. roseum was demonstrated as increased plant dry weight after 1 month and increased 1000‐grain weight at harvest. The disease‐controlling effect of G. roseum on F. culmorum was shown in a field experiment with spring barley.

Vital fluorochromes as tracers for fungal growth studies.

Eight fluorescent dyes were tested for staining the spores or mycelia of six fungi and for their translocation into new growth when the preloaded spores or mycelia were incubated on agar coated coverslips. The dyes studied were Cellufluor, Nile red, fluorescein diacetate (FDA), carboxyfluorescein diacetate (CFDA), chloromethylfluorescein diacetate (CMFDA), aminochloromethyl coumarin (CMAC), and the carbocyamines DiIC18(3) and DiOC18(3). The fungi on which the dyes were tested included Botrytis cinerea, Fusarium oxysporum f.sp. lycopersici, Idriella bolleyi, Pythium oligandrum, Sclerotium cepivorum and Trichoderma harzianum. Most of the fluorochromes gave good initial staining of mycelia or spores; however, FDA fluorescence faded rapidly during excitation, making it impractical for use. Also, the spores and mycelia of B. cinerea and T. harzianum sometimes gave weak fluorescence with Nile red, and the spores and mycelia of I. bolleyi gave unusually weak fluorescence with Cellufluor. There were other variations of staining among the different dye/fungus combinations, but each fungus showed strong fluorescence at least one dye. Cellufluor, CMFDA, CMAC and, to a lesser extent, CFDA and Nile red, were efficiently translocated into new growth from preloaded spores or mycelia, whereas FDA, DiIC18(3) and DiOC18(3) were not. The extent of translocation ranged from 0.1 to 1.2 mm in germ tubes arising from spores, and from 0.9 to 9.2 mm in mycelia extending from dye-loaded agar blocks. The findings suggest that fluorescent dyes could be used as markers or tracers in studies of fungal growth and differentiation.

Interaction between root lesion nematode,Pratylenchus neglectus(Rensch 1924) Chitwood and Oteifa 1952, and root rotting fungi of wheat

Abstract The most frequently isolated fungi from lesioned and non‐lesioned segments of wheat roots collected from fields infested with Pratylenchus neglectus were Fusarium oxysporum (Fo), F. acuminatum (Fa), F. equiseti (Fe), Microdochium bolleyi (Mb), Gaeumannomyces graminis (Gg), Bipolaris sorokiniana (Bs), Pythium irregulare (Pi), Pyrenochaeta terrestris (Pt), Phoma sp., and Ulocladium atrum. In a glasshouse experiment, some of the above fungi plus Rhizoctonia solani (Rs) were tested singly and in selected combinations with and without P. neglectus. Number of nematodes per plant and per gram dry root and severity of root lesioning showed a positive interaction between some of these fungi and the nematode. Inoculation with Rs, Mb, Bs, Gg + Fe, or Pi resulted in significantly higher nematode populations per plant or per gram dry root. However, with Gg + Rs, nematode numbers were reduced. Pt, Pi, Fo, or Gg + Fe in combination with the nematode significantly increased severity of root lesioning.

Physiology of production of viable biomass and spore inoculum for the biocontrol agent Idriella (Microdochium) bolleyi

Biomass of the biocontrol agent Idriella bolleyi can be produced in submerged liquid culture as mycelium, conidia, and chlamydospores. Each fraction was separated and quantified. The conidial fraction appeared to be the most thermotolerant, suggesting that this form had the best potential shelf life of the three. Conidia were produced during the early phase of growth and their production did not appear to require any form of nutrient exhaustion or growth rate decay. The highest viability per unit biomass was obtained in carbon-limited medium, with sodium nitrate as the nitrogen source, after 6 h. Maximum biomass was not obtained in this medium until 167 h and, as the biocontrol product is likely to be sold by weight, an acceptable compromise between the two parameters must be found. Excess ammonium chloride in the medium appeared to inhibit growth. A procedure, involving culture homogenization, was adopted in order to estimate potential viability in shake-flask liquid culture.

Effect of substrate and plant maturity on the incidence of infection of potato roots by pathogenic and non-pathogenic fungi

Colonization of roots of field-grown potato plants by pathogenic and non-pathogenic fungi was examined by plating surface-sterilized roots onto low nutrient medium. Plants which originated from micropropagated nodal cuttings (MP plants) or from seed-grade potato tubers (ST plants) were subjected to nine pre-plant treatments designed to test the effect of different potting substrates and different levels of natural tuber inoculum on the root mycoflora. The experiment was repeated in a second year but at a different site; in each year roots were collected once in July, August and September. Cylindrocarpon destructans, Colletotrichum coccodes, Trichoderma viride, Microdochium bolleyi and Fusarium tabacinum showed the highest mean frequencies of colonization; Verticillium tricorpus, Rhizoctonia solani, Polyscytalum pustulans and Gliocladium roseum were mainly confined to roots of ST plants or MP plants with added tuber inoculum, and Trichoderma viride, Chrysosporium pannorum, Penicillium spp., Aureobasidium pullulans and Phoma leveillei were dominant in roots of MP plants raised in peat-based potting substrates. There was evidence of suppression of the potato pathogens R. solani, P. pustulans and C. coccodes, and of several non-pathogens in roots of the same plants. Most of the fungi recovered from potato roots were also typical components of the soil microflora and occurred in both field sites. Exceptions were Fusarium oxysporum and V. dahliae, which were found in one year only. Possible associations and dissociations between different combinations of fungi occurring together on the same root system were evaluated using a correlation matrix, and spatial relationships of different groups demonstrated by principal coordinate analysis. The influence of the indigenous mycoflora on root colonization by particular potato tuber pathogens is discussed.

Screening Selected Fungi for Antagonism towardsPseudocercosporella herpotrichoides(Fron) Deighton, the Cause of Eyespot Disease of Cereals

In the laboratory, a dual culture primary screen using wheat straw agar (WSA) showed that 64 out of 152 selected fungi inhibited the in vitro growth of Pseudocercosporella herpotrichoides by 50% or more. An ‘asymmetric’ species of Penicillium isolated from wheat stubble was the most effective, inhibiting growth of the pathogen by 70%. The results were similar using both W‐type and R‐type isolates of P. herpotrichoides. Other fungi showing in vitro antagonism included: Trichoderma viride, T. koningii, T. harzianum, Chaetomium globosum, Acremonium persicum, Botryotrichum piluliferum, Sordaria alcina, Microdochium bolleyi, Rhizoctonia cerealis and Laetisaria arvalis. In a glasshouse secondary screen, the 64 fungi showing antagonism in vitro were assessed further for their ability to reduce eyespot disease symptoms of wheat seedlings using a straw collar co‐inoculation technique. Of them, 13 fungi reduced disease symptoms significantly: a Chaetomium sp. from stubble, two Fusarium spp., a F. culmorum isolate T. viride, T. koningii, T. harzianum, B. piluliferum, M. bolleyi, L. arvalis, the ‘asymmetric’ Penicillium sp. and two unidentified fungi from stubble. A F. culmorum isolate was the most effective antagonist on average, giving disease reductions of 54 and 58% for the W‐type and R‐type of P. herpotrichoides respectively. M. bolleyi, T. harzianum and the F. culmorum isolate were the most effective antagonists of the W‐type, all three reducing disease by 54%. T. viride was most effective against the R‐type, reducing disease by 64%.

Differential tropism to living and dead cereal root hairs by the biocontrol fungus Idriella bolleyi

Video microscopy was used to study the orientation of spore germination and germ-tube growth on root hairs of aseptic cereal seedlings. Germ-tubes of Idriella (Microdochium) bolleyi emerged away and grew away from living wheat and oat root hairs, but towards dead root hairs which were rapidly overgrown and penetrated. I. bolleyi also germinated away from adjacent glass fibres, cotton fibres and touching spores of itself, Gliocladium roseum or Clyindrocarpon sp. On wheat, Fusarium oxysporum f. sp. lycopersici, Gliocladium roseum and Geotrichum candidum showed lesser and contrasting responses compared with I. bolleyi: F. oxysporum orientated slightly towards living and away from dead root hairs, G. candidum orientated slightly towards both living and dead hairs, and G. roseum showed no significant orientation. Also, these fungi did not proliferate on dead root hairs. The tropic responses of I. bolleyi are consistent with its role as a weak parasite of cereals and its ability to control cereal root pathogens by competitive exclusion from naturally senescing host tissues.

Infektionsstrukturen von Microdochium bolleyi an Wurzeln und Koleoptilen von Gerste

AbstractInfection structures of Microdochium bolleyi on barley roots and coleoptiles Microdochium bolleyi grows within roots and coleoptiles of barley either leading to a damage of the tissue or to a symptomless infection. The present work investigated whether these different types of infection are correlated with different infection structures of the fungus. Two types of hyphae were formed infectmg either the rhizodermis or the epidermis. The fungus spread within the cortex only, not affecting the endodermal cells or the vascular tissue. The extend to which the roots were damaged depended on the infection density. Differences in the structure of hyphae formed in symptomless or necrotic parts of the roots were not observed. In both, roots and coleoptiles, hyphae were detected in dead cells only.

Mycorrhiza and root-associated fungi in Spitsbergen

Roots of 76 plant species collected in West Spitsbergen (Svalbard), in the middle-northern Arctic zone, were examined for mycorrhiza and root-associated fungi. Dryas octopetala, Pedicularis dasyantha and Salix polaris were ectomycorrhizal and Cassiope tetragona and Empetrum hermaphroditum ericoid mycorrhizal. Pedicularis dasyantha was only slightly infected. Structures resembling vesicular-arbuscular mycorrhizal (VAM) fungi were not found in the roots, and soil samples screened for VAM fungi contained only one spore. Root endophytic fungi commonly occurred in Spits-bergen, but only Olpidium brassicae, Pleospora herbarum, Papulaspora, Microdochium bolleyi and Rhizoctonia solani were identified with reasonable certainty. A sterile endophytic dark-septate fungus (DSF) was in 39.5% of the flowering-plant species examined, especially in the Brassicaceae, Caryophyllaceae, Saxifragaceae and Poaceae. DSF were categorized into four slightly overlapping groups. Sterile endophytic hyaline septate fungi were rare. In the literature it is suggested that at least some of the DSF species or the hyaline septate fungi are functionally mutualistic rather than saprophytic or pathogenic. The literature on ectomycorrhizal fungi and plants in Spitsbergen is reviewed, including about 50 species, mainly of the genera Cortinarius, Hebeloma, Inocybe, Laccaria, Lactarius and Russula. These are symbiotic with the above-mentioned ectomycorrhizal plants. Four further ectomycorrhizal plants (Betula nana, Salix spp.) are very rare in the area.