Showing papers on "Mycelium published in 1982"

The role of vesicular arbuscular mycorrhizal fungi in agriculture and the selection of fungi for inoculation

Abstract: Vesicular arbuscular (VA) mycorrhizas are roots infected with particular soil fungi which form symbiotic associations. It is often assumed that VA mycorrhizal fungi could be used to increase the efficiency of phosphate fertilizers in agriculture. Our principal concern is the question: 'Can the symbiosis be exploited on a large scale?'. VA mycorrhizas increase nutrient uptake, and hence plant growth, by shortening the distance that nutrients must diffuse through soil to the root. Mycorrhizal roots do not appear to have a lower threshold concentration of nutrients for absorption from solution than do non-mycorrhizal roots. Most soils contain VA mycorrhizas. Hence, for plant growth to respond to inoculation with VA mycorrhizal fungi, agricultural soils must have either a low incidence of indigenous VA mycorrhizal fungi or alternatively, species which are less effective than the inoculant fungi in their ability to stimulate nutrient uptake by plants. The distribution of species of VA mycorrhizal fungi varies with climatic and edaphic environment, as well as with land use. However, the factors which control their distribution are poorly understood. Differences among VA mycorrhizal fungi in their ability to increase nutrient uptake appear to be due to differences in their ability to form mycorrhizas rapidly and extensively. The importance of other differences among the fungi, such as in the absorption of nutrients from solution or in the distribution and amount of external mycelium, has yet to be clearly demonstrated. Inoculant VA mycorrhizal fungi must be capable of persisting in soils at a high inoculum potential, as well as being able to increase nutrient uptake. Until now, little attention has been paid to characteristics which enable the fungi to persist after inoculation. We are critical of many of the methods employed in experiments aimed at selecting 'efficient' VA mycorrhizal fungi. For practical purposes, selection can only be achieved by means of comparisons performed in untreated field soils, with phosphorus supply limiting plant growth. Because the form of inoculum can affect the relative abilities of VA mycorrhizal fungi to infect and improve plant growth, appropriate inocula are needed for each agricultural situation. The survival of many species of fungi in various types of inocula requires further study so that procedures can be developed for introducing particular fungi into agricultural soils. This review emphasizes many gaps in our knowledge. For example, we need more information on how and to what extent species or strains of VA mycorrhizal fungi differ in their ability to increase plant growth. We know even less about their beneficial effects in years following that of field inoculation. The ecology of indigenous VA mycorrhizal fungi in field soils has also been largely neglected. These and other deficiencies preclude any immediate recommendations for large-scale inoculation with selected VA mycorrhizal fungi.

Development of external hyphae by different isolates of mycorrhizal glomus spp. in relation to root colonization and growth of troyer citrange

Abstract: SUMMARY The hypothesis was tested that the amount of external hyphae of a vesicular-arbuscular mycorrhizal (VAM) fungus extending from roots out into soil is not always proportional to the extent of colonization of the root cortex. Growth enhancement and amount of external hyphae were compared for eight isolates of five Glomus spp. that differed in their geographic origin and capacity to enhance growth of Troyer citrange, but were similar in their capacity to extensively colonize Troyer citrange roots. In general, isolates from California increased growth in a P-deficient (9.8 mg kg−1) California soil more than did non-native isolates from Florida soils. The difference between the capacity of California and Florida isolates to enhance growth was not a function of the degree to which they colonized the roots since all had colonized over 95% of the root length by the time of harvest. Differences in growth enhancement did appear, however, to be a function of the amount of external hyphae that had developed as estimated by the weight of soil they had bound into aggregates. This study suggests that isolates of VA mycorrhizal fungi may differ in their capacity to develop an external hyphal system independent of their capacity to colonize the root cortex, and that we cannot assume that high levels of colonization will necessarily mean the fungus has also developed the mycelium in the soil necessary to transport nutrients responsible for plant growth enhancement.

Factors Affecting the Elicitation of Sesquiterpenoid Phytoalexin Accumulation by Eicosapentaenoic and Arachidonic Acids in Potato

Abstract: Eicosapentaenoic and arachidonic acids in extracts of Phytophthora infestans mycelium were identified as the most active elicitors of sesquiterpenoid phytoalexin accumulation in potato tuber slices. These fatty acids were found free or esterified in all fractions with elicitor activity including cell wall preparations. Yeast lipase released a major portion of eicosapentaenoic and arachidonic acids from lyophilized mycelium. Concentration response curves comparing the elicitor activity of the polyunsaturated fatty acids to a cell-free sonicate of P. infestans mycelium indicated that the elicitor activity of the sonicated mycelium exceeded that which would be obtained by the amount of eicosapentaenoic and arachidonic acids (free and esterified) present in the mycelium. Upon acid hydrolysis of lyophilized mycelium, elicitor activity was obtained only from the fatty acid fraction. However, the fatty acids accounted for only 21% of the activity of the unhydrolyzed mycelium and the residue did not enhance their activity. Centrifugation of the hydrolysate, obtained from lyophilized mycelium treated with 2n NaOH, 1 molarity NaBH(4) at 100 degrees C, yielded a supernatant fraction with little or no elicitor activity. Addition of this material to the fatty acids restored the activity to that which was present in the unhydrolyzed mycelium. The results indicate that the elicitor activity of the unsaturated fatty acids is enhanced by heat and base-stable factors in the mycelium.

Growth kinetics and morphology of colonies of the filamentous form of Candida albicans.

Abstract: Summary: The growth and development of mycelia of the dimorphic fungus Candida albicans in serumcontaining medium is described. Initially, colonies are undifferentiated (all hyphae in the mycelium having approximately the same diameter, extension rate, apical and intercalary compartment lengths) whereas older mycelia differentiate at the colony margin to produce leading hyphae that are wider, faster growing and have longer apical and intercalary compartment lengths than the branches they subtend. Early colony development exhibits unusual features: germ tube extension is linear (not exponential as in other fungi) and there is a prolonged delay between septation and the onset of branch formation. The subsequent patterns of growth and branching are similar in all other respects to those of other mycelial moulds. Mycelia have septa that delimit single nuclei within compartments. The septa do not prevent cytoplasmic flow and consequently allow the peripheral growth zone to span several compartments. From these results we conclude that filamentous growth of C. albicans in this medium is best described as truly mycelial.

Relationships between host and endophyte development in mycorrhizal soybeans

Abstract: SUMMARY Symbiotic associations of soybeans and the vesicular-arbuscular mycorrhizal fungus Glomus fasciculatus were grown to maturity in a sand-perlite rooting medium watered with a nutrient solution containing growth-limiting amounts of soluble phosphorus. Development of fungal mycelia external and internal to the host plant's root system was measured by determining chitin in isolated fungal mycelium, in the rooting medium, and in the mycorrhizae. The biomasses of the extra- and intraradical mycelia were calculated from the values of chitin obtained splectrophotometrically. The amount of total fungal biomass relative to that of the host plant varied throughout the lifespan of the association and reached a maximum of 2-3 % 10 weeks after planting. The amount of intraradical mycelium increased throughout the host plant's life span. Extraradical fungal structures attained a maximum weight at the onset of logarithmic growth of the soybean pods and decreased thereafter. Cessation of the rapid growth phase of G. fasciculatus lagged behind that of the host plant's vegetative structures, but appeared to be related to pod development. The fungus to root dry wt ratio was 12-3 % at senescence. The ratio of extra- to intraradical mycelium decreased throughout the association's lifespan. Since the extraradical hyphae are the organs responsible for enhanced nutrient uptake this ratio is proposed as an index of the endophyte's usefulness to the host. High values for this usefulness index coincided with significant growth enhancement of the host plant. Source-sink relationships in the host appear to be a determining factor in the growth of the fungal endophyte.

Taxonomic affinities and criteria for identification of the common ectendomycorrhizal symbiont of pines

Abstract: Evidence from cultured and soil-borne mycelium clearly indicates that the widespread mycorrhizal symbiont (or symbionts) known as the E-strain is an ascomycete anamorph. The evidence includes regul...

Ovicidal fungi in soils of Cuba.

Abstract: Thirty-six strains of ovicidal fungi were isolated from 122 investigated soil samples collected in Cuba. The isolated strains belong to 8 genera, 2 strains consist of sterile mycelium only. Most of the strains belong to the genus Fusarium (4 species, 1 undetermined strain), the remaining ones to Mortierella (3 species and 6 undetermined strains), Humicola (2 species), Paecilomyces (2 species) and Penicillium (2 species). The genera Verticillium, Gliocladium and Cunninghamella were represented by one species each. A majority of isolated strains exhibited a high to very high ovicidal activity immediately after isolation; strains with a lower initial activity occurred only exceptionally. The high ovicidal activity has been preserved till now in the following five strains: Paecilomyces marquandii (2 strains), Fusarium solani f. spec. radicicola (1 strain), Mortierella sp. (1 strain) and the sterile mycelium (1 strain).

Tremorgenic indole metabolites and aflatoxins in sclerotia of Aspergillus flavus: an evolutionary perspective

Abstract: Isolates of Aspergillus flavus Link from both cool and warm latitudes were cultured on potato dextrose agar containing yeast extract to identify sclerotia-producing strains. Chloroform–MeOH extracts of sclerotia were analyzed for the presence of aflatoxins and major indole metabolites (e.g., cyclopiazonic acid, aflatrem, and dihydroxyaflavinine). Aflatoxin is reported from sclerotia of A. flavus for the first time. Cyclopiazonic acid was detected primarily in sclerotia of isolates from warmer latitudes. Aflatrem and dihydroxyaflavinine were detected in sclerotia from 85% of the strains examined. These metabolites are associated with the sclerotial stage of the life cycle, because neither were detected in extracts of the culture medium and mycelium of Petri dish cultures from which all the sclerotia were removed. Geographic variation and intrafungal allocation of these toxic compounds in A. flavus are examined from the evolutionary ecologist's perspective of selective forces shaping the chemical defense sy...

Factors for Conversion of Fungal Biovolume Values to Biomass, Carbon and Nitrogen: Variation with Mycelial Ages, Growth Conditions, and Strains of Fungi from a Salt Marsh

Abstract: Direct-count analysis of fungal biomass cannot be accurate or precise without firm knowledge of values for quantity of mass per unit volume of mycelium. We have determined a range in weight of dry matter, carbon and nitrogen per cm3 of fresh mycelium for salt-marsh fungi, using microecosystems which were rough simulations of a range of natural environments of fungi in salt marshes dominated by Spartina alterniflora Loisel. We found a wide range in dry matter per cm3 of mycelium, averaging 0.2 g cm3 for a group of less dense samples, and 0.9 g cm3 for more dense samples. The high densities were associated with young mycelium of two species known to be well adapted to the salt-marsh environment. The low densities were found for old mycelium, and for young and old mycelium of a species whose degree of adaptation to the salt-marsh environment is uncertain. Nitrogen and carbon percentages of dry fungal biomass were similar to those reported by other investigators (nitrogen, -4%; carbon, -35%).

Vanillic acid metabolism by selected soft-rot, brown-rot, and white-rot fungi

Abstract: Metabolism of vanillic acid, a product of lignin degradation, has been studied in selected representatives of soft-rot, brown-rot and white-rot fungi. All of the brown-and white-rot species examined decarboxylated vanillate to methoxyhydroquinone oxidatively. Mycelium extracts of all these fungi, except Pleurotus ostreatus contained high levels of an NAD(P)H-dependent vanillate hydroxylase. P. ostreatus also released 14CO2 from 14COOH-vanillate but by a different mechanism possibly involving phenoloxidases. Most of these fungi also contained a dioxygenase which catalysed the intra-diol cleavage of hydroxyquinol (1,2,4-trihydroxybenzene) to form maleylacetate. No 3-O-demethylase activity was detected, and data indicate that in some of the fungi examined cleavage of the aromatic ring occurs without prior removal of the methoxyl group. None of the soft-rot fungi tested contained vanillate hydroxylase or hydroxyquinol 1,2-dioxygenase, but very low levels of protocatechuate 3,4-dioxygenase were detected in mycelium extracts. Vanillate catabolism among members of this group occurs via a different route which may involve ring demethylation although no 3-O-demethylase activity was detected in this study. The enzyme NAD(P)H-quinone oxidoreductase was demonstrated to exist in all the studied groups of fungi.

Measurement of the extraradical mycelium of a vesicular-arbuscular mycorrhizal fungus in soil by chitin determination

Abstract: Development of a vesicular-arbuscular mycorrhizal (VAM) fungus in association with soybean was determined in a greenhouse soil mix by chitin assay. Samples were sieved to eliminate hexosamine-containing contaminants. This preparation reduced the interference caused by extraneous soil substances and permitted quantitative measurement of extraradical VAM fungal mycelium in the soil mix by colorimetric assay. Recovery of added chitin, used as an internal standard, was greater in the soil mix than in an inert medium indicating that some hexosamine was stabalized from chemical degradation by other soil components.

Development of mycorrhizae, extramatrical mycelium and sclerotia on pinus strobus seedlings

Abstract: SUMMARY On Pinus strobus seedlings cultured in growth pouches successful ectomycorrhiza formation took place upon inoculation with Pisolithus tinctorius, Cenococcum geophilum, Suillus granulatus, Suillus tomentosus, Paxillus involutus, Hebeloma cylindrosporum and Thelephora terrestris. Under the conditions used ectomycorrhizae formed within 2 weeks and some of them, P. tinctorius, P. involutus and T. terrestris, developed mantles and Hartig nets in less than 5 days. Mycelial strand formation took place around the root system of P. strobus 2 weeks after inoculation with P. tinctorius. Sampling on the 93rd day revealed no difference in ectomycorrhizal formation or the development of mycelial strands and sclerotia between root systems that were or were not illuminated. However, low light intensities on the aerial parts of the seedlings reduced the mycelial strands and sclerotia formation. Variation of nitrogen and phosphorus concentration added to the pouches were also studied. Increased concentrations of nitrogen, keeping phosphorus constant, led to greener seedlings and increased amount of ectomycorrhizal, mycelial strands and sclerotia. No sclerotia were formed in the complete absence of added nitrogen. Both the percentage of ectomycorrhizal short roots and the phosphorus contents of the seedlings increased in proportion to the amounts of nitrogen added. Increased concentrations of phosphorus, keeping nitrogen constant, led to a reduction in the percentage of ectomycorrhizal short roots without affecting the nitrogen content of the seedlings, the hyphal strands and sclerotia formation. The observations on the ontogeny of the sclerotia of P. tinctorius reported here for the first time fully support their identity as sclerotia.

Population structure, inter-mycelial interactions and infection biology of Stereum gausapatum

Abstract: Isolates from wood, fruit body tissue and single basidiospores of Stereum gausapatum from several locations in South-West England showed several types of reaction when paired on 2% malt agar. ‘Compatible’ reactions resulted in the formation of a distinct secondary mycelium between monospore isolates. ‘Lytic’ reactions resulted in the development, between monospore isolates, of a crescent-shaped zone of appressed mycelium bounded by regions of liquid droplet exudation. In pairings between sibs, the distribution of these two reaction types showed a reciprocal relationship depending on which fruit body had been used for isolation. In non-sib pairings the compatible reaction predominated although, as in a few sib pairings, in many instances it appeared to follow an initial lytic reaction. A narrow pigmented zone of ‘mutual antagonism’ was usually formed between different wood or fruit body tissue isolates, or laboratory-produced secondary mycelia, and also between certain non-compatible/non-lytic combinations of monospore sibs. Some interactions between monospore sibs were ‘weak’, with little or no pigment production or other obvious effect. These observations suggest that S. gausapatum is heterothallic and that there is a link between the mechanisms underlying the lytic and compatible reactions. The implications in the infection biology of S. gausapatum and in relation to findings for other Stereum spp. are discussed.

The Role of Laccase in Carpophore Initiation in Coprinus congregatus

Abstract: SUMMARY: The mycelium of the basidiomycete Coprinus congregatus is not uniformly competent to differentiate. Differentiation occurs only in localized areas of young mycelia. Studies on laccase activities from whole mycelium extracts suggest a correlation between overall laccase levels and the development of mushroom primordia. However, studies of higher resolution on the localized areas of developmental competence, under a variety of light, nutrient and temperature regimes, indicate that laccase is probably not involved in the actual development of the primordia. If laccase is involved in C. congregatus differentiation, it is only at the initial, light-requiring, step.

Effect of aeration and light on fruit body induction in Schizophyllum commune

Abstract: When dikaryotic mycelium of Schizophyllum commune was cultivated on complete medium for 3 days at 25 °C in the dark and then transferred to continuous light at the same temperature, fruit body differentiation took place in 24 h. The first clear sign of differentiation, seen between 8–12 h in the light, was a uniform front of synchronously growing hyphae, which later became the inner border of the fruit body. The outer border was formed between 12 and 20 h. A significant shortening in the length of the cells was observed in the mycelium producing fruit bodies. The comparison of cell length in cultures growing in light and dark, with and without aeration, indicated that the primary factor controlling cell length was aeration and then light. A pattern of intensified hyphal branching, including growth of clamp connexions into branches, that was observed only in the cultures grown in light was also interpreted as a light-induced response.

Regulation of formation of aerial mycelia and spores of Streptomyces viridochromogenes.

Abstract: Growth of Streptomyces viridochromogenes on a solid glycerol-NH4NO3 salts medium was accompanied by the formation of aerial mycelia and spores. Adding 0.5% or more casein hydrolysate to the medium stimulated growth while completely repressing the formation of aerial mycelia and spores. This repression was temporary, as evidenced by the fact that transfer of the organisms to media not containing casein hydrolysate resulted in the appearance of aerial mycelia and spores. The effects of individual amino acids were tested. Glycine retarded growth and repressed formation of both aerial mycelia and spores. L-Aspartic acid, L-glutamic acid, and L-histidine stimulated or had little effect on growth and repressed formation of spores but not aerial mycelia. Repression by casein hydrolysate could not be attributed to the carbon/nitrogen ratio or the pH of the medium. Adding 1.25 to 2.5 mM adenine to the medium caused a reversal of the casein hydrolysate repression of aerial mycelium formation but did not reverse repression of sporulation. Dimethyladenine and 8-azaguanine had an effect similar to that of adenine, but a variety of other purine or pyrimidine derivatives had no effect on casein hydrolysate repression. The repression of aerial mycelium and spore formation by casein hydrolysate occurred only in media containing 15 mM or more phosphate. Aerial mycelia and spores were formed in media containing casein hydrolysate and 3 mM or less phosphate.

Inorganic nitrogen nutrition and yeast-mycelial dimorphism in Aureobasidium pullulans

Abstract: Y-M dimorphism in A. pullulons has been examined in yeast cells spread on agar so that the response of individual cells could be determined. The Y → M transition can occur directly without an intermediate swollen cell stage. Inorganic nitrogen source did not quantitatively influence the transition, but affected the maintenance of mycelial growth in colonies developing from the spread cells, NH 4 + favouring more mycelium than NO 3 − . The M → Y transition is interpreted as being determined autogenically during colony growth, but under some conditions M forms can develop within a Y colony.

Development of t'he conidial state of myriogenospora atramentosa

Abstract: A liquid medium and a corn meal-malt agar medium were developed for culturing Myriogenospora atramentosa, a systemic parasite of pasture grasses. On living leaves the conidiomata that are produced in stromata precede the perithecia and are irregularly hysteriform and ephemeral. Conidia are acicular, I-celled, and hyaline. In culture, polar or lateral germ tubes from ascospore part-spores or conidia give rise to secondary conidia or develop into a mycelium. Aggregations of hyphae resembling sporodochia form in the mycelium. Simple conidiophores develop on both the sporodochia and the mycelium. The presence of an ephelidial conidial state like that in species of Balansia supports the classification of M. atramentosa in the tribe Balansiae, subfamily Clavicipitoideae, Clavicipitaceae. Light and scanning electron microscopy showed that the conidia are holoblastic on sympodial conidiophores. The occurrence of holoblastic as well as phialidic conidia indicates that conidiogenesis must be considered in the classification of the Clavicipitaceae.

Production of tannase (tannin acyl hydrolase e.c.3.1.1.20) by a strain of aspergillus niger

Abstract: Culture of a strain of Aspergillus niger on medium containing 3 % tannic acid yielded tannase (tanin acylhydrolase), evidenced both in the culture medium and the mycelium. Fermentation in submerged culture at constant air flow gave mycelium with high tannase activity.

Mushroom supplement containing protein and a time delay coating

Abstract: An improved nutrient supplement is disclosed for enhancing the growth of mushroom mycelium in a compost bed comprising a particulate nutrient supplement having at least a partial coating of a hydrophobic material that is not readily assimilable by competing microorganisms in the compost.

Distribution of cellular amino acids, protein, and total organic nitrogen during fruit body development in Flammulina velutipes. II. Growth on potato–glucose solution

Abstract: In Flammulina velutipes grown on potato–glucose solution the dry weight of mycelium decreased when fruitbodies elongated rapidly. Loss of dry weight by aborted primordia and stunted fruitbodies par...

Steroid modification with immobilized mycelium of Aspergillus phoenicis

Abstract: The bioconversion of progesterone by Aspergillus phoenicis has been studied. The metabolism in our conditions of experiment gave five important products. About 10 hours were necessary to obtain the highest concentration of 11-α-hydroxyprogesterone. During this time, 90% of progesterone were transformed at the optimal pH value 2.5. The transformations were tested using different immobilization methods which merits and limitations will be discussed.