Mycelial Strands Research Articles

The penetration of soil by mycelial strands of ectomycorrhizal fungi

Soil factors affecting growth of mycelial strands from ectomycorrhizas into surrounding soil were studied experimentally. Treated soil cores were inserted into root boxes for 4–6 weeks, then infiltrated with gelatin, sectioned, and mycelial strands harvested. Very large differences in mycelial strand growth (measured by weight) occurred between different soils, some soils completely inhibiting growth of strands of the mycorrhizal fungus Rhizopogon luteolus. Compaction of soil reduced mycelial strand penetration greatly e.g. by 80 per cent in one experiment. Soil sterilization ameliorated compaction effects. High soil phosphorus tended to increase strand growth but nitrogen level and Pseudomonas fluorescens. a common soil bacterium, had small or inconsistent effects.

The uptake and translocation of phosphate by mycelial strands of pine mycorrhizas

Uptake and rapid translocation of 32P-orthophosphate to Pinus radiata mycorrhizas from soil by mycelial strands of Rhizopogon luteolus was demonstrated. In greenhouse material, translocation occurred from soil for at least 12 mm and some 30–80 per cent of phosphate absorbed from 5 × 10 −6 M as KH 2PO 4 was translocated. In the field, translocation occurred for 12 cm. Uptake by excised mycelial strands was metabolically mediated. Translocation occurred more rapidly when the untreated ends of strands were placed in an osmoticum: polarity in translocation was also observed. It was concluded that uptake and translocation by mycelial strands (as distinct from individual hyphae) provide an effective method for mycorrhizal exploitation of large inter-root soil volumes and assist the plants in competition for nutrients. Large differences occurred between strains of the same species in mycelial strand growth in soil. Mycelial strands of R. luteolus grew through the test soil at 1.3-2.9 mm/day and along P. radiata roots at 1.7 mm/day at 25°C day and 16°C night temperatures.

Rhizina undulata . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Rhizina undulata . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Larix decidua, L. leptolepis, Picea abies, P. sitchensis, Pinus contorta, P. nigra, P. maritima, P. sylvestris, P . elliottii var. elliottii, P. patula, P. pinaster, P. strobus, Pseudotsuga menziesii, Tsuga mertensiana, T. heterophylla , Abies alba among softwoods, and Castanea sativa , a hardwood. DISEASE: Group dying of conifers. The disease is characterized by the death of seedlings or plantation trees in groups, which are always found around old fire sites. The roots of infected trees are covered with white or yellowish mycelial strands and fruit bodies of the fungus are formed on the litter at the base of diseased trees during wet weather. GEOGRAPHICAL DISTRIBUTION: Europe (Belgium, Britain, Bulgaria, Finland, France, Germany, Netherlands, Poland, Republic of Ireland, Sweden, USSR (Lithuania & Latvia SSR)); Africa (Rhodesia, Ngwane (formerly Swaziland), South Africa); USA (Oregon, Washington State, Minnisota, California, Md, New York); Canada (British Columbia). TRANSMISSION: By ascospores through the soil, after they have been activated by exposure to temperatures of 35-45°C in the neighbourhood of pine roots.

Kinetics of apical and lateral branching in Aspergillus nidulans and Geotrichum lactis

Apical branching was a normal feature of hyphal morphogenesis at the margins of colonies of Aspergillus nidulans and Geotrichum lactis . In G. lactis apical branching occurred in a dichotomous manner. After a hypha had divided apically there was no further wall extension below the point of origin of the branches. Apical branching was preceded in A. nidulans but not G. lactis , by a slight deceleration (18%) in growth rate. Branching was followed in both species by an acceleration in the rate of total hypha formation (i.e. sum of the growth rates of both branches) which persisted until each branch had attained a growth rate identical to that of the original parent hypha; thus there was a doubling in the rate of hypha formation. The growth of lateral branches produced by leading hyphae could be divided into a short exponential phase (doubling times as short as 6–7 min), a phase of increasing growth rate and a phase of constant linear growth rate. The mean linear growth rates of lateral branches of A. nidulans and G. lactis were respectively about 21 and 31% less than the mean growth rates of their leading hyphae. The rate of growth of parent hyphae was not significantly affected by lateral branch formation. Some lateral branches of A. nidulans grew parallel and close to the hyphae from which they arose; thin mycelial strands of three to four hyphae often resulted from this type of growth. The apical region (37 μm from the tip) of a germ-tube of A. nidulans was apparently involved in a negative autotropic response. It is suggested that this region may represent the extension zone of the hypha.

Growth of Odontia bicolor in vitro

The growth of Odontia bicolor in soil and in balsam fir wood was studied. In steam-sterilized organic soil, the fungus grows rapidly, producing a scanty and uniform growth, whereas in propylene oxide gas-treated or natural organic soil, it forms mycelial strands. In mineral soil, the fungus reacts as in organic soil except that growth is more sparse. The fungus grows through natural soil and colonizes new substrate more rapidly when mycelial strands are linked to an appropriate food base.The optimum temperature for growth on a 2.5% malt extract medium occurs between 22 and 27 °C. The fungus grows well in balsam fir wood at any moisture content above 42% of the oven-dry weight, and twice as fast in sapwood as in heartwood. Its growth is not influenced by previous storage of the wood, either frozen (−20 °C) or at a temperature of 2 °C for up to 16 weeks.

Translocation of C^(14)‐Labeled Compounds in Mycorrhizae and It Implications in Interplant Nutrient Cycling

Loblolly pine (Pinus taeda L.) seedlings were grown axenically in mycorrhizae synthesis cultures with either the symbiont Pisolithus tinctorius (Pers.) Coker and Couch or Thelephora terrestris (Ehrh.) Fr. Glassware was designed to allow synthesis of mycorrhizae on two seedlings physically separated except for a bridge formed between the two root systems by mycorrhizal fungus mycelium. Glucose—C14 and sucrose—C14 were used as tracers to investigate movement of labeled compounds from mycorrhizal roots to external mycelium, from external mycelium to roots and from one root system to the other via shared mycelium. Whether applied to foliage as glucose—C14 or sucrose—C14, C14 was readily translocated to pine roots. Transport of C14 from mycorrhizal roots to external hyphae of T. terrestris up to a distance of 12 cm was shown, but only slight movement of C14 occurred into external hyphae of P. tinctorius. The introduction of glucose—C14 and sucrose—C14 to isolated strands of T. terrestris resulted in the movement of C14 from strands to roots. Movement of isotope from one seedling to the other via mutually—shared mycelium did not occur in the synthesis cultures; however, C14 movement between root systems artifically linked by mycelial strands indicated that interplant exchange can take place. Evidence suggests that mycorrhizal fungi such as T. terrestris could be effective in the exchange of organic and possibly other materials between root systems in an ecosystem.

Detection and Vertical Distribution of White Root Rot Fungus in Forest Soils

Detection and vertical distribution survey of the white root-rot fungus, Rosellinia necatrix (Hart.) Berl. were conducted in four forest soils in Hyogo and Kyoto Prefectures. These forests are located adjacent to mulberry fields which had been established on newly opened forests and the mulberry trees are sufferring from the white root rot disease. Whether the fungus was present or not in the forest soils was tested by examining the typical mycelium strands adhering to plant remnants and also by baiting method. In the latter method, bundles of mulberry and copse twigs, 30cm long, were buried to the depth of 20cm, and after a month or two the bundles were removed and examined for the colonization of the fungus. Under forest conditions, the fungus grows and survives saprophytically on partially decomposed plant debris in the F-, H-, and A1-layeres. The fungus inhabits to depths of one to five cm from the top of A-layer. In cases where the A-layer developed well into a thick layer, the fungus grew densely throughout the A1-layer; on the contrary, in cases where the A-layer developed only faintly, the fungus appeared in F- and H- layers and the amount of mycelial strands remained small.

Formation of sclerotia and mycelial strands in Rhizoctonia solani Kühn

The dish technique of Schutte (1956) was modified to study the formation of sclerotia of Rhizoctonia solani. First, a small dish containing 7.5ml of agar medium is placed at the center of a Petri dish, after which 15ml of agar medium is poured into the remaining space. The contents of agar media in both dishes are different, i.e. Czapek's agar lacking sugar but containing all other nutrients, and distilled water agar containing only carbohydrate. The fungus, inoculated at the center of the small dish, develops a colony, and then sclerotia are formed on the agar medium deficient in carbohydrate, irrespective of the site in dish, while few sclerotia are formed on the medium containing carbon sources. In other words, sclerotia of the fungus are formed by utilizing carbohydrate, which is supplied by translocation through the mycelium from separate sites and the utilization efficiency is higher when carbohydrate is added to the outer medium. Autoradiography with 14C-glucose, applied at the inner or outer medium, showed the movement of isotope through the mycelium bidirectionarily. Some of the isolates tested formed mycelial strands on the outer surface of inner dish, which morphogenesis was similar to those of Helicobasidium purpureum.

The surface mycoflora of ash roots

Cylindrocarpon radicicola Wr. forms a predominant component of the surface mycoflora of Fraxinus excelsior roots. Its predominance is especially evident on actively growing root tips, which enlarge the area of root system. The fungus occurs in an active mycelial state throughout the year. The usefulness of the Harley-Waid method for isolating such mycelia was once more confirmed. The hyphae form mycelial strands, thus ensuring the greater vitality of the fungus in soil space. In comparative experiments with other forest woody and herbaceous plants the predominant presence of C. radicicola was again established. Therefore, this fungus is assumed to be a common inhabitant of root surfaces of higher plants.

Purification of the spherule-endospore phase of Coccidioides immitis.

Upon shaking an aqueous suspension of spherules, endospores and mycelium of Coccidioides immitis with chloroform, selective agglomeration of the mycelium around the emulsified chloroform droplets occurred. The mycelial strands became aligned on the surface of the droplets in parallel configurations, as an apparent consequence of surface forces, and the droplets accumulated at the chloroform-water interface. Spherules and endospores were not so-affected and could be resuspended readily in the aqueous phase of the system. This observation formed the basis of a procedure that was employed to obtain the spherule-endospore phase from cultures of C. immitis in highly purified form.

Morphogenesis of mycelial strands in the cultivated mushroom, Agaricus bisporus

When growing from an inoculum providing a suitable food base over an inhospitable surface, such as that of glass, or through a non-nutrient medium, such as unsterilized soil, the mycelium of Agaricus bisporus becomes organized into mycelial strands. The morphogenesis of the strands appears very similar to that previously observed in strand development by Merulius lacrymans, Phymatotrichum omnivorum and Agaricus campestris. A number of adjacent and parallel-running leading hyphae growing out from a food base into the surrounding soil become bound together and ensheathed by a profuse development of their finer branches (tendril hyphae), which are thin-walled and aseptate. Strand development is acropetal. By the use of sterilized, acid-washed quartz sand as a non-nutrient medium surrounding the food base, it could be demonstrated that strand development amongst the outgrowing mycelium was inversely correlated with the concentration of free nutrients in the medium. At very low nutrient concentrations, mycelial growth was sparse but strand development was conspicuous; at higher nutrient concentrations, the reverse occurred.

Poria carbonacea (Berk. & Curt.) Cooke as a cause of timber rot in Jamaica

Poria carbonacea (Berk. & Curt.) Cooke, a tropical brown-rot fungus, is recorded as causing decay of structural timber ( Brosimum alicastrum Sw.) in recently built houses in Jamaica. The outbreaks snowed several features in common with dry rot caused by Merulius lacrymans , but the mycelial sheets on the surface of infected timber were not seen to form mycelial strands. The sporophore and cultural characters of P. carbonacea are described. The optimum temperature for growth is about 31·5° C. and the minimum relative humidity for development of mycelium on agar is about 90% at 30° C. The fungus is comparable with other well known wood-destroyers in its ability to decay wood of B. alicastrum .

Stages of Development in Rhizomorphic Thalli of Armillaria mellea

Rhizomorphs and mycelial strands occur widely in the Ascomycetes, Basidiomycetes, and Fungi Imperfecti, but yet the structure, development, and functions of these common vegetative organs have not been studied intensively. At the present time there appears to be no obvious morphological distinction between a mycelial strand and a rhizomorph, for these structures exist in a continuum from simple to complex, some being little more than individual hyphae or aggregations of hyphae, as in Ophiobolus graminis, and others ranging upward to highly elaborate rhizomorphs containing well organized apices and differentiated celltypes, as in Sphaerostilbe repens, Merulius lacrimans, and Armillaria

The biology of Helicobasidium purpureum Pat.

Three isolates of Helicobasidium purpurem were shown, as originally isolated, to use both ammonium and nitrate N, as well as a mixture of amino acids. Two required thiamin and were partially deficient for some other growth factor or factors. The third behaved anomalouslyand its growth factor requirements were not determined. A cytological examination showed the vegetative mycelium of the isolates studied to be binucleate. H. purpureum was shown to depend on a food base for growth through soil, which was little affected by a wide range of soil conditions. The fungus showed an affinity for continuous surfaces in soil. Pieces of carrot root stimulated growth once the fungus had made contact with them, but not otherwise. Formation of mycelial strands from a food base appeared to constitute the normal growth habit of the mycelium in soil. A morphological study of strand development in natural (i.e. unsterilized) soil suggested that, under these conditions, there is some mutual attraction between the outgrowing hyphae of H. purpureum , so that hyphae coming together by chance tend to continue parallel growth in association. The coherence of strands formed in this way was increased by an interweaving growth of the main hyphae, by a binding action of short side branches and by anastomoses. The postulated attraction between hyphae presumed responsible for stranding did not, however, prevent branching of strands or their occasional disintegration into the constituent individual hyphae. Attempts to induce the formation of mycelial strands in pure culture were unsuccessful, so that it has not been possible to determine the nature of the stimulus responsible for stranding that operates upon hyphae growing through soil from a food base. Survival of sclerotia of H. purpureum was poor in an acid soil, but was unaffected by a wide range of conditions in a slightly alkaline soil. Survival in the first mixed with sand was improved when this soil was rendered alkaline. Decreased longevity of sclerotia in the acid soil was associated with a high incidence of spontaneous germination.

The Development and Behaviour of Mycelial Strands in Merulius lacrymans (Wulf.) Fr.

The Development and Behaviour of Mycelial Strands in Merulius lacrymans (Wulf.) Fr.

The Development and Behaviour of Mycelial Strands in Merulius lacrymans (Wulf.) Fr.

The Development and Behaviour of Mycelial Strands in Merulius lacrymans (Wulf.) Fr.

A new hyaline species of Verticillium: V. intertextum sp.nov.

An isolate of Verticillium, obtained from a wilted Japanese maple tree in Massachusetts, U.S.A., formed septate, branching mycelium which, when growing subaerially or aerially, became aggregated into mycelial strands or ‘ropes’ from which the verticillately branched conidiophores developed. When grown on Dox's agar in darkness the prostrate mycelium was hyaline, but in daylight it was distinctly orange-pink. Maximum growth in culture was at 25°C. and at pH 7·2. Good growth occurred on media containing sucrose, dextrose, maltose or glycerine with a maximum on maltose. Variation of the nitrogen source indicated that growth was best on media containing sodium nitrate. The fungus, although re-isolated from inoculated specimens of Acer palmatum, did not induce wilt in this plant nor in a wide range of other plants usually susceptible to infection by Verticillium. The organism is accorded specific rank and is named Verticillium intertextum sp.nov.

The development of sclerotia of certain fungi

The development of sclerotia of six species of fungi was studied and three different methods of formation were distinguished. Sclerotial initials of Rhizoctonia solani develop by the increased branching and septation of the ordinary hyphae. The mature sclerotia are rather loosely constructed of brown barrel-shaped cells with dense contents. Sclerotia of Botrytis allii, B. cinerea and Sclerotium cepivorum develop terminally by the repeated dichotomous branching of a hyphal tip followed by increased septation and fusion of the branches. Mycelial strands of S. rolfsii and Sclerotinia gladioli put out branches which coalesce to form the sclerotia.

Function of the mycelial strands in substrate colonization by the cultivated mushroom, Psalliota hortensis

Experiments are described showing that for successful colonization of a suitable prepared compost by mycelial strands of the cultivated mushroom fungus, a certain inoculum potential is necessary; if inoculum potential is only just adequate, colonization is greatly delayed. Inoculum potential at the growing tips of the mycelial strands appears to vary directly with size and vigour of the inoculum food-base, and inversely with distance from this food-base. New mycelial strands soon grow out from freshly colonized compost into new soil, but not into soil already occupied by older strands.

A study of violet root rot factors affecting production and growth of mycelial strands in Helicobasidium purpureum pat

Summary For this investigation, potato tubers were inoculated with 8·5 mm. disks cut from a growing colony of Helicobasidium purpureum on meat-malt extract agar, and buried in glass jars filled with soil; maximum growth of mycelial strands from the inoculum disk was measured after some seven weeks by a paper scale fitted to the curved surface of the tuber. The distance covered by mycelial strands and the frequency of infection cushions decreased with increase in storage age of the tuber. Inoculum disks cut from the growing margin of the fungus colony (marginal disks) were less effective for production and growth of strands than disks cut within a circle drawn 8·5 mm. from the margin (submarginal disks). The greater effectiveness of submarginal disks was related to their greater mycelial density; progressive development of mycelium within the marginal zone of the fungus colony was due to infiltration of new hyphae from the submarginal zone, as well as to branching of the original hyphae within the marginal zone. Production and growth of strands also increased with concentration of nutrients in the agar, and especially with that of the malt constituent. With increase in age of the colony to five or six weeks at 25°C., the potency of inoculum disks for strand production declined, but this apparent staling effect did not occur with disks cut from colonies on double depth agar (6 mm.). Transfer of colonies after three or four weeks' growth at 25°C. to laboratory temperature (15–20°C.) for a further 1–2 weeks reduced strand growth from disks more severely than did continued incubation of the colonies at 25°C. for the same period. Growth of strands was greater in a 1 soil : 3 sand mixture than in soil. Soil acidity depressed strand growth at medium and low but not at high soil moisture content, and not in the soil/sand mixture. This adverse effect of soil acidity was also shown in growth of mycelium over Rossi-Cholodny slides.