Showing papers in "Transactions of The British Mycological Society in 1971"

Antagonistic properties of species-groups of Trichoderma: II. Production of volatile antibiotics

Abstract: Isolates from different species-groups of Trichoderma were tested for production of non-volatile antibiotics, by an agar layer technique. Preliminary studies on the chemical nature of these antibiotics were made. Many isolates produced non-volatile antibiotics active against a range of fungi. The ability to produce such antibiotics varied between isolates of the same species-group as well as between isolates of different species groups. The susceptibility of fungi to these antibiotics varied widely; Fomes annosus (Fr.) Cooke was the most susceptible and Fusarium oxysporum Schlecht, ex Fr. the most resistant of the test fungi used. Gliotoxin and viridin were not produced, but other chloroform-soluble antibiotics, including trichodermin and peptide antibiotics were detected.

Antagonistic properties of species-groups of Trichoderma: III. Hyphal interaction

Abstract: When grown in dual culture, hyphae of the majority of Trichoderma isolates coiled around hyphae of different test fungi. Penetration of hyphae by Trichoderma hyphae seldom occurred. The importance of antibiotics and extracellular enzymes during hyphal interaction is discussed.

Thermophilous fungi of coal spoil tips: II. Occurrence, distribution and temperature relationships

Abstract: Thirty–two thermophilous fungal species were isolated from twelve coal spoil tips in Staffordshire. The distribution of fungi in five spoil tips with high surface-soil temperatures (warm areas), in comparison with non-warm areas, is presented together with the frequency of isolation of each species. Populations of thermophilous fungi in well-colonized warm areas were found to be higher than those of the corresponding non-warm areas, but were lower in the warm areas where colonization by higher plants was poor. There may be a balance between temperature and nutrient levels. The cardinal temperatures for growth of thirty–five thermophilous fungal species were determined and the species divided into four groups on the basis of their temperature-growth relationships. The difficulties involved in defining thermophily are discussed in conjunction with the possible mechanisms operating.

Mycoflora associated with Typha latifolia

Abstract: The fungal succession on Typha latifolia L. has been followed from the time the leaves first appeared through the stages of senescence to their ultimate decay. The main colonizers of this substrate were shown to be Alternaria tenuis, Aureobasidium pullulans, Cladosporium herbarum, Epicoccum nigrum and Phoma typharum. The numbers of species increased as the plant senesces. Sporobolomyces spp. were isolated only during the summer months. Seasonal fluctuations of the common species are illustrated. Certain groups of species tended to be specific to a particular site on the plant or to a particular condition of the substrate. Moribund leaves were mainly dominated by Leptosphaeria spp., whilst litter regions supported nematophagous fungi. The rhizome and roots yielded relatively fewer fungi than other sites on the plant.

Biochemical and structural changes in non-growing maintained and autolysing cultures of Aspergillus nidulans

Abstract: Studies were made of the dry weight, and content of DNA, RNA, protein, carbohydrate, lipid and melanin, of Aspergillus nidulans cultures with and without a maintenance ration of glucose. Both types of culture were cytologic-ally heterogeneous at all stages of development but the proportion of autolysing hyphae was always less in maintained than in starved cultures. Ninety-six h after glucose deprivation, 60 % of hyphal fragments were viable. Intrahyphal hyphae were common in all cultures. Fully autolysed hyphae consisted of empty hyphal walls. In steady-state cultures grown at a specific growth rate of 0·043 h −1 (doubling time, 16·2 h) about 80% of the glucose respired was catabolized via the Embden-Meyerhof-Parnas (EMP) pathway and about 20% by the hexosemonophosphate (HMP) pathway. When the feed was reduced to 1·5 times the maintenance ration, or terminated completely, there was a rapid decrease in the respiratory activity of the culture and virtually all the glucose was catabolized via the EMP pathway.

Mycoflora of living and dead leaves of Nothofagus truncata

Abstract: The fungal colonists of the phylloplane and internal tissues of leaves of Nothofagus truncata (New Zealand hard beech) were studied using a combination of direct observational and cultural methods. Young leaves acquired a mycoflora of internal parasites and discrete surface colonies soon after unfolding. The ensuing succession, which involved fungi imperfecti and asco-mycetes, was followed until just after leaf-fall. Although certain of the primary saprophytes are common components of successions on leaves of other trees, they apparently colonized the leaves of hard beech at an earlier stage than in the other successions. Some colonists of the phylloplane showed tendencies towards either epiphyllous or hypophyllous development. Seasonal sampling showed a peak of fungal activity in summer.

A synopsis of the carbomycetaceae and terfeziaceae (tuberales)

Abstract: The Carbomycetaceae Trappe fam.nov. is established for the genus Carbomyces , formerly included in the Terfeziaceae. The Terfeziaceae now includes Amylascus Trappe gen.nov., Delastria Tul. & Tul., Hydnobolites Tul. & Tul., Mukagomyces Imai, Picoa Vitt., Terfezia (Tul. & Tul.) Tul. & Tul., and Tirmania Chatin. A parallel polyphyletic origin is postulated for these genera, but the family Terfeziaceae is retained until more data permit re-evaluation of the entire Tuberales. Two former genera are reduced to subgeneric rank: Picoa subgen. Leucangium (Quel.) Trappe and Terfezia subgen. Mattirolomyces (Fisch.) Trappe. These new combinations are proposed: Tirmania nivea (Desf. ex Fr.) Trappe, Amylascus herbertianus (Cribb) Trappe, Terfezia arenaria (Moris) Trappe, and T. terfezioides (Matt.) Trappe.

Thermophilous fungi of coal spoil tips

Abstract: Calcarisporium thermophile and Sphaerospora saccata sp.nov. are described from coal spoil tips, together with several other strains and species of taxonomie or ecological interest.

Ultrastructure of septa in Melampsora lini

Abstract: Three types of septa occur in the uredial thalii of Melampsora lini (Ehrenb.) Lev. The typical perforate septa of filamentous hyphae consist of a cross-wall containing two electron-dense layers separated by an electron-transparent central lamella. The central pore in the cross-wall is partially to completely blocked by an electron-dense plug that has the configuration of a pulley wheel. The plug is often surrounded by a distinct region of cytoplasm devoid of organelles. Partial septa occur in filamentous hyphae and pseudoparenchyma of uredial primordia. They consist of thick invaginations of the entire longitudinal wall profile. These septa have large pores which lack plugs and do not impede movement of organelles. Complete septa consisting of cross-walls without pores are typical of the pseudoparenchymatous uredial primordia.

Behaviour of Ophiobolus graminis on slides buried in soil in the presence or absence of wheat seedlings

Abstract: On slides buried in field soils, mycelial inoculum of Ophiobolus graminis produced hyphae, which grew towards wheat seedling roots, forming clumps of cells in the root hair region and infecting hairs before penetrating seminal root axes. Without roots few new hyphae grew, but phialospores (microconidia) were produced abundantly. Growth was similar using infected wheat roots as inoculum, except fewer and smaller clumps developed. Using infested debris from a wheat-field as inoculum, the amount of clump formation and root hair infection was negatively correlated with the size of the colonized host fragments and no phialospores developed. All clumps were ephemeral and lysed quickly after seminal axes were infected. Phialospores remained intact during 21 days' observation, but did not germinate. Mycelium labelled with fluorescent brightener confirmed that the observed growths were O. graminis . It is suggested that O. graminis has an ephemeral feeding stage before initial infection of an axis. The extent of this depends on the nutritional status of the original inoculum : inoculum with large food reserves can infect roots without extensive clump development and root hair infection. When there is no host stimulus, active mycelium with small food reserves produces phialospores, but slowly metabolizing mycelium in debris does not.

Aureobasidium pullulans: An endophyte in sycamore and other trees

Abstract: Aureobasidium pullulans was frequently isolated from surface-sterilized living twigs, buds, leaves and seeds of sycamore, and from twigs of horse-chestnut and lime. The distribution of the fungus in the sycamore is described. It was isolated from roots and shoots of seedlings, but diminished in the roots during the first year of growth.

Synchronous initiation and maturation of Aspergillus niger conidiophores in culture

Abstract: Synchronous development of Aspergillus niger conidiophores was obtained by using a system in which complete development was divided into four distinct morphogenetic stages, (i) Conidiophore initiation occurred in a low nitrogen (LN) medium, but not in a medium in which both glucose and nitrogen were exhausted simultaneously and not in LN medium under oxygen-limited conditions, (ii) Conidiophore growth occurred without exogenous nitrogen although exogenous glucose was essential. In addition, development was enhanced by a colonial growth form indicating that translocation from mycelium to the conidiophore was an important feature of this stage. During stages (i) and (ii) there was the abundant production of a carotenoid pigment, (iii) Vesicle and phialide formation did not occur on conidiophores formed in LN medium. Transfer of aborted conidiophores to a medium containing a nitrogen source and a tricarboxylic acid cycle intermediate as a carbon source stimulated vesicle and phialide formation. There was a concurrent stimulation of respiration and an increase in RQ, value. Conidiospore formation was inhibited and this resulted in vesicle and phialide proliferations, (iv) Heavy conidiospore production occurred on a further transfer of conidiophores with vesicles and phialides to a glucose nitrate medium. Conidiophore initiation, vesicle and phialide formation and carotene production were inhibited by reduction of the oxygen supply rate although vegetative growth could continue.

New aquatic hyphomycetes

Abstract: Three aquatic hyphomycetes, Anguillospora curvula sp.nov., Dendrospora juncicola sp.nov. and Lemonniera cornuta Ranzoni, a new British record, are illustrated and described.

Conidial evidence for host restriction in Claviceps purpurea

Abstract: Graminicolous Claviceps spp. other than C. purpurea are tribe-specific in their host ranges, whereas C. purpurea (including C. microcephala) is recorded from grasses belonging to at least seventeen tribes. On the assumption that significant differences in conidial size and shape are indicative of speciation taking place within C. purpurea, a comparative study has been made of i o i honeydew samples from thirty-one species of British grasses belonging to twenty-eight genera and thirteen tribes. Samples showed considerable variation in size and shape of conidia but, after applying Bartlett's test for homogeneity of variance, it is claimed that independent samples collected from different specimens of the same host could reasonably have come from the same population. By contrast, spore populations from different hosts are shown by the analysis of variance and covariance to differ significantly in both sizeand shape. The results of atransplant experiment, in which conidia were grown in culture from slices of sclerotia with a known size of honeydew conidia, indicate these differences to be primarily under genetic control. Conidial populations from different hosts may therefore be divided into groups by applying Duncan's multiple-range test. The groups are considered sufficiently distinct to provide morphological evidence for host restriction in C. purpurea. It is noteworthy that a close similarity exists between the species-composition of these groups and the ‘biologic forms’ proposed by Stager from cross-inoculation experiments.

Studies on leaf blotch of barley (Rhynchosporium secalis)

Abstract: In seedling tests, some isolates of Rhynchosporium secalis attacked all cultivars of barley tested, but others, though able to attack most cultivars were unable to attack Dea and Pioneer. This suggests that there were two physiologic races of the fungus among the fifteen isolates tested. In addition to their specific resistance to the second race, Dea and Pioneer were partially resistant to all isolates, as were (to varying degrees) some of the other cultivars not specifically resistant to either race. Though there were some discrepancies, cultivars generally behaved in the same way in seedling tests as in the field. Though isolates of the fungus differed in the rate at which their spores germinated, any one isolate germinated similarly on all cultivars of the host. Resistance in the host was expressed at the stage of penetration. Leaves of Dea and Pioneer were penetrated only to a very slight extent by isolates to which they were specifically resistant, and were penetrated less than leaves of Cambrinus and Proctor by isolates to which they had non-specific resistance. Although in general the extent to which mycelium proliferated below the cuticle was correlated with the severity of symptoms, Dea and Pioneer have non-specific resistance partly because in them more mycelium is associated with any particular level of severity of external symptoms than in Cambrinus and Proctor. Some cultivars have non-specific resistance because on them spores are less readily formed.

Ontogenetic diversity of sclerotia of Sclerotinia sclerotiorum and related species

Abstract: The ontogeny of sclerotia of Sclerotinia sclerotiorum (Lib.) de Bary and S. trifoliorum Erikss., both of which produce large sclerotia, was compared with that of S. libertiana Fuckel and S. minor Jagger, which produce smaller sclerotia. Initials of the large-type sclerotium develop terminally by the repeated branching of long aerial, primary hyphae and fusion of the branches. Initials are formed in close proximity and several initials coalesce to form one sclerotium. Initials of the smaller-type sclerotium develop in positions lateral to the main hyphae by the repeated branching, interweaving and frequent anastomoses of short aerial hyphae. This is a simple type of development from strands. Initials are not normally formed in close proximity and coalescence of hyphal aggregates is less frequent. Small hyphal aggregates which developed into rounded spore-like cells were produced by all isolates. The differences between the two sclerotium types are due to the growth patterns of the mycelia of the two groups. The ontogenetic diversity suggests taxonomie differences between them. Study of sclerotium ontogeny in association with biochemical and serological studies, should be useful as an aid to taxonomy.

Effect of temperature, oxygen and carbon dioxide on cellulolytic activity of some fungi

Abstract: Eleven fungi isolated from conveyor belting were tested for their cellulolytic activity under a range of temperatures (15–35°C), oxygen concentrations (20–1%, v/v) and carbon dioxide concentrations (0–15%, v/v). Three fungi, Chaetomium globosum Kunze ex Fr., Memnoniella echinata (Riv.) Galloway and Stachybotrys atra Corda were distinguished by high activity throughout this range of temperature. The other organisms showed relatively greater losses of activity at the extremes of the range. Three fungi Trichoderma koningii Oud., Fusarium solani (Mart.) Sacc. and S. atra were most tolerant of low oxygen levels. Carbon dioxide had little effect on most organisms, but high concentration caused marked inhibition of Fusarium culmorum (W. G. Sm.) Sacc. and stimulation of C. globosum, F. solani and Fusarium moniliforme Sheld.

Conidium liberation in Erysiphe graminis

Abstract: The effects of various factors upon the liberation of conidia of Erysiphe graminis DC. f.sp. tritici Marschal (powdery mildew of wheat) were investigated, using a Hirst automatic volumetric spore trap and a range of meteorological instruments. The data obtained were analysed by standard visual methods and also by means of the correlation coefficient phi ( φ ), ( ad-bc )[( a + b )( c + d ) ( a + c )( b + d )]- ½ , where a, b, c and d refer to the cells of a 2 × 2 table used for the computation of coefficients of association. A digital computer was employed in this analysis. The difficulties and potentialities of such a means of analysis are discussed. Seasonal and diurnal periodicities recorded by other workers were confirmed. Days in which rainfall occurred were profoundly different from dry days, the diurnal periodicity of spore release being obscured. Wind, rainfall, surface dryness of the host leaves, high temperatures and low relative humidities were positively associated with spore liberation. Rainfall was independent of the other phenomena, which occurred as a complex. Onset of rain and wind were shown to be more important than continuation of either.

Turgor pressure of fungal mycelia

Abstract: The osmotic water potential and turgor pressure of fungal mycelia were determined by thermocouple psychrometry. The water potential ( ψ ) of intact aerial mycelia was assumed to be the same as that of the growth substrate: the osmotic water potential ( ψ s ) of the mycelia was determined by psychrometric measurement of the water potential of disrupted samples of the mycelia. Turgor pressure ( ψ p ) of the mycelia was calculated by difference ( ψ p =ψ-ψ s ). The effect of decreasing substrate water potential on the turgor pressure, osmotic water potential and colony growth rate of Mucor hiemalis and Aspergillus wentii was evaluated, using sucrose and KCl to control substrate water potential. Mycelial turgor pressure ranged from 4 to 11 bar for M. hiemalis and 12 to 18 bar for A. wentii but showed no consistent relationship to growth rate or to substrate and osmotic water potential. The results indicate that solute-induced growth retardation of M. hiemalis probably involves an inhibitory influence of low internal osmotic water potential.

Seasonal periodicity of saprolegniaceae at Ibadan, Nigeria

Abstract: Seasonal periodicity was observed in some aquatic phycomycetes found in Ibadan, Nigeria. The Saprolegniaceae found in this study could be classified as dry, rainy and all-season species. The dry-season species did not occur during the rainy season, while the rainy season species were found only during the rainy months. Species with eccentric oospores were found mainly during the dry season but those with centric and subcentric oospores occurred only during the rainy season.

Physiological requirements of two marine phycomycetes, Althornia crouchii and Ostracoblabe implexa

Abstract: Growth of two marine phycomycetes isolated from diseased oyster shells was investigated. Both fungi were obligately marine and stenohaline, with optimum growth in 2·3–2·5% sodium chloride. Of the minor salts in an artificial sea-water medium, sodium bicarbonate produced the most significant stimulation of growth of Althornia crouchii. Both fungi grew best at 30 °C; there was no growth at 35°. Light inhibited the growth of the fungi. They grew well in natural or artificial sea water supplemented with yeast extract (1 g/l) and peptone (1 g/l). They did not grow if the concentrations of yeast extract and peptone were reduced to 0·02 g/l. A. crouchii produced normal sporangia and zoospores on glycogen, D(+)trehalose or cellobiose. The addition of sodium malate also permitted good growth, but without zoospore production. Ostracoblabe implexa was stimulated by the simultaneous addition of sodium malate, aspartic acid and sodium glutamate. Most other carbohydrates and fatty acids tested either did not support growth or were inhibitory. Inorganic nitrogen sources tested did not support growth of A. crouchii.

Dispersal and viability of sporangia of Pseudoperonospora cubensis.

Abstract: Intensive dispersal of sporangia of Pseudoperonospora cubensis (Berk & Curt.) Rostow from infected fields of cucumber in a hot, dry climate started between 06.00 and 07.00 h, reached a peak around 08.00 h, and subsided by noon. Infectivity of airborne sporangia to cucumber test plants diminished with high temperatures and high relative humidities during the interval between the time of dispersal and commencement of conditions favourable for infection. At the humidity levels tested during such an interval of 5 and 22 h, sporangial infectivity was reduced to nil only at 35 and 40°C, the highest temperatures tested. Infectivity of dispersed sporangia was greatly reduced when sporangia were wetted for a period too short to ensure infection and were then allowed to dry out. Most of the sporangia thus treated failed to release zoospores and this explained the decrease in their infectivity. Whether sporangia were dispersed by wind or by immediate contact with water did not alter the sensitivity of wetted sporangia to drying.

Fine structure and physiology of conidial germination in Aspergillus fumigatus

Abstract: The fine structure of Aspergillus fumigatus conidia at successive stages of germination is described. Spore swelling is accompanied by a stretching and disintegration of the outer wall layer of the spore, nuclear division, increase in the number of mitochondria and the formation of a vacuole from endoplasmic reticulum. The inner spore wall gives rise to the germ-tube wall by growing out through the remains of the outer wall. Spore swelling is dependent upon an external supply of assimilable carbon compounds. Percentage germination at a fixed incubation time is much reduced by total lack of nutrients and is more influenced by the level of external carbon than by that of external nitrogen compounds.

Ustilago violacea on Silene dioica

Abstract: A small, undetermined proportion of plants of S. dioica spontaneously undergo total or partial change from female to hermaphrodite or to male and vice versa, in the absence of U. violacea , confirming that the fungus is not the only cause of sex change in S. dioica . Infection of S. dioica by U. violacea was produced by treating with chlamydo-spores seeds, seedlings, open male and female flowers, terminal and axillary buds and, to a very limited extent, by stem injection and by the use of spore-contaminated soil. The distribution of the mycelium in naturally infected plants was examined. Chlamydospores may germinate even in unopened infected anthers. Un-germinated chlamydospores placed in distilled water germinate from 4 h 15 min onwards at about 18°C. After 16 h there is 100 % germination at temperatures from 14 to 23°. The percentage germination obtained was not affected when 1%. 2% and 5% solutions of glucose or of malt extract were used. The optimum pH for germination was about 6–6. Exposure to daylight did not affect the percentage of germination as compared with that in darkness. Percentage germination fell with length of time the spores had been held in storage. After 24 months it still reached 25–32% following storage at 0°, 46–54% after storage at 20°. Young chlamydospores are binucleate, mature spores uninucleate. The occurrence of the reduction division when the spore germinates is confirmed. The diploid nucleus has four, the single haploid nucleus of each promycelial cell two chromosomes.

Studies on soft rot of yams in storage

Abstract: Anatomical studies on inoculated yam disks revealed that the pathogens of yam causing storage rots penetrated the parenchyma cells of the tubers and established themselves within the cells. Infected cells were cleared of most of their starch grains and their walls disintegrated. The pathogens produced extracellular cellulolytic and pectic enzymes in culture. Studies on the effect of the pathogens on yams showed that the carbohydrate contents of the rotten tubers dropped.

Occurrence of Endogone spores in West Pakistan soils

Abstract: The incidence of Endogone spores in 200 soil samples from West Pakistan was investigated. Most samples were found to contain one or more types of spore. Two new types are described, in addition to the six types already found by Mosse & Bowen (1968 a ) in Australian and New Zealand soils. All spore types formed vesicular-arbuscular mycorrhizas with red clover seedlings. The relationship of spore types and their number with soil category is discussed.

Location and extent of fungal mycelium in grains of barley

Abstract: Cryostat sectioning and phenol-acetic-aniline blue staining was used in a detailed study of the location of the internal fungal mycelium in apparently healthy grains of barley plants. Hyphae were observed in the parenchyma layer of the lemma and palea which enclose the mature caryopsis, and within the pericarp layer of the caryopsis itself. No mycelium was observed in other parts of the grain. As assessment technique is described for the estimation of fungal mycelium present within individual grains.

Reaction of potato leaves to infection by Phytophthora infestans in relation to position on the plant

Abstract: When potato plants cv. King Edward are inoculated with Phytophthora infestans by a standard method, which is described, four types of leaf reaction can be distinguished: (1) successful infection with fungal spread giving normal lesions, (2) relative hypersensitivity (as defined), (3) hypersensitivity (as defined) and (4) no visible symptoms. Leaves showing these reactions form zones on growing plants and up to three such zones can be present. In very young plants all leaves are very susceptible and show normal lesions. In older plants up to flowering time reaction types 2, 3 and 4 appear in a zone intermediate between susceptible zones with reaction type 1 at the top and base of the plant. In plants immediately after flowering there may be a less well-defined susceptible zone at the top of the plant so that temporarily only two clear zones are present. With further increase in leaf number the susceptible zone at the base increases in size, the intermediate more resistant zone remains constant in extent and a susceptible zone is again present at the top. The overall resistance of plants therefore varies with age and may be related to the occurrence of different reaction types. These reactions have been shown by plants grown in the open and in the glasshouse but are more apparent on leaves attached to the plant and, with the exception of normal lesions, are much less frequently seen on detached leaves. Reactions of leaves on various kinds of branches were similar to those on main stems except that leaves on flower shoots showed more frequent occurrence of reaction types 3 and 4. When the concentration of sporangia in the inoculum applied to leaves on main stems was 5000/ml reaction types 3 and 4 were most frequent but were somewhat fewer at a concentration of 10000 sporangia/ml and least at concentrations between 25000 and 100000 sporangia/ml.

Resistance of barley varieties to establishment of subcuticular mycelia by Rhynchosporium secalis

Abstract: Spores of Rhynchosporium secalis (Oudem.) J. J. Davis established subcuticular hyphae in leaves of both susceptible and resistant barley varieties. The frequency, and rate of extension, of hyphae was greater in susceptible than in resistant varieties. The resistance of barley varieties to the establishment and growth of hyphae was associated with the presence of previously identified major genes. Cuticle thickness did not contribute to this resistance which was, at least in part, an active response to invasion. Isolates of Race U.K. 2 were more effective than isolates of U.K. 1 in overcoming the resistance to hyphal establishment of any variety.