Showing papers in "Transactions of The British Mycological Society in 1980"

Comparison of histological and physiological responses to Phakopsora pachyrhizi in resistant and susceptible soybean

Abstract: Although cuticular and epidermal penetration by the rust and death of the penetrated cell were similar in two cultivars, subsequent hyphal branching and growth was decreased and retention of trypan blue stain was increased in the resistant cultivar. No uredinia formed in the resistant cultivar. Phytoalexin formation began earlier in the resistant cultivar and at a time when many cells had changed in their physiology as revealed by stain retention. A product of germinating urediniospores caused more rapid browning and phytoalexin formation in pods of the resistant cultivar.

Isolation of entomogenous fungi from elm bark and soil with reference to ecology of Beauveria bassiana and Metarhizium anisopliae

Abstract: Using a selective medium, the entomogenous fungus Beauveria bassiana was isolated in quantity from bark of elm trees and from soil at the base of trees at Culford, Suffolk and near Cambridge during 1976 and 1977. Most of the trees had died of Dutch elm disease but some were healthy. It was concluded that B. bassiana was present as conidia which originated from infected insects on or under the bark. By contrast Metarhizium anisopliae was isolated only once from a soil sample. Differences in the distribution of these two unspecialized entomogenous hyphomycetes are discussed.

Metals in sporophores of basidiomycetes

Abstract: The contents of Na, K, Rb, Mg, Ca, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb in sporophores of 130 basidiomycete species from woodland and pasture areas in south Sweden are reported. The frequencies of most metal concentrations approximated to a log normal distribution, but positively one-tailed aberrations occurred for Cd, V, Ca and Mn. The ratio formed between highest and lowest concentration ranged from 3000 in Cd to 9.5 in Mg. The frequencies of high or low concentrations differed between major genera, but exceedingly high concentrations were found in scattered species of a variety of genera.

Pleomorphism in Crinipellis perniciosa, causal agent of witches' broom disease of cocoa

Abstract: Basidiospores of Crinipellis perniciosa (Stahel) Singer germinated rapidly in water and on standard agar media to produce a fine, hyaline, binucleate mycelium 1.5-3 μm diam, with clamp-connexions; the secondary or dikaryotic mycelium. White to cream, fast-growing, regular, cotton-like colonies were formed on agar. The primary mycelium was short-lived and dikaryotization occurred within 24–48 h. Basidiospores on vigorous cocoa callus tissues germinated slowly with short, abnormally swollen germ-tubes giving rise either to thickwalled chlamydospores or to a grossly swollen flexuous, hyaline to brown, uninucleate mycelium 5–20 μm diam with dense granular cytoplasm. Characteristic slow-growing, cerebriform colonies were irregularly formed on agar surrounding the callus. A similar, although less swollen, mycelium was observed intercellularly in infected green cocoa stems (brooms) and pods. Dikaryotization occurred when active callus or plant growth declined, and in old callus cultures and dead brooms the tissues were colonized, both inter- and intracellularly, by secondary mycelium. The primary mycelium became thick-walled and devoid of contents. The life cycle of C. perniciosa is divided into two phases which are separated morphologically, genetically and physiologically: the biotrophic or parasitic, monokaryotic phase and the necrotrophic or saprophytic, dikaryotic phase. The fungus is now classified as a hemibiotroph.

Notes on some fungi occurring on Peltigera, with a key to accepted species

Abstract: A key to 40 obligately lichenicolous fungi reported on species of Peltigera , and notes on 16 of these, are provided. That so many species are exclusive to this host genus, and that six constitute monotypic genera, suggests that Peltigera represents a particularly ancient group within the Lecanorales. The following new taxa are introduced: Dacampiosphaeria gen.nov. (Pleosporales), D. rivana (de Not.) comb.nov. ( Leptosphaeria rivana (de Not.) Sacc.), Herpotrichiella peltigerae (Fuckel) comb.nov. ( Trichosphaeria peltigerae Fuckel), Karsteniomyces gen.nov. (Sphaeropsidales), K. peltigerae (P. Karst.) comb.nov. ( Stagonopsis peltigerae P. Karst.), Lasiosphaeriopsis gen.nov. (Coronophorales s. lat.), L. salisburyi sp.nov., Leptosphaeria clarkii sp.nov., Phaeospora peltigericola nom.nov. ( Leptosphaeria arnoldii Rehm), Phoma peltigerae (P. Karst.) comb.nov. ( Phyllosticta peltigerae P. Karst.), Trichoconis lichenicola sp.nov., Wentiomyces peltigericola sp.nov., and W. lichenicola (Hansf.) comb.nov. ( Dimeriella lichenicola Hansf.). The nomenclatural problems surrounding the generic name Scutula Tul. are reviewed, Phragmonaevia fuckelii Rehm and P. peltigerae Rehm are recorded for the British Isles for the first time, and recent collections of Pezizella epithallina (Phill. & Plowr.) Sacc. are reported from the British Isles and Denmark.

Mononematous species of Hirsutella

Abstract: The entomogehous hyphomycete genus Hirsutella Pat. is divided into two sections based on the presence or absence of synnemata. A key, descriptions, and illustrations are provided for ten mononematous species, including four new species, H. brownorum, H. guyana, H. illustris and H. rhossiliensis. Lectotypes are designated for two species, H. versicolor Petch and H. strigosa Petch, and H. thompsonii Fisher is neotypified. A lectotype is designated for Calonectria pruinosa Petch, the perfect stage of H. versicolor, which is redescribed and illustrated as Torrubiella pruinosa (Petch) comb. nov. Three species excluded from the mononematous section are discussed and a lectotype is designated for one, H. besseyi Fisher.

Effect of copper on morphology of Aureobasidium pullulans.

Abstract: The presence of copper during growth of Aureobasidium pullulans in both liquid and solid media had a profound effect on morphology of the organism. In addition to stimulating melanin synthesis copper also promoted formation of filaments or hyphae during later stages of growth. The taxonomic implications of these findings are discussed.

Control of hyphal orientation in colonies of Mucor hiemalis

Abstract: This is a study of factors controlling the development of hyphae of Mucor hiemalis on a plane uniform agar surface, whereby a single germ tube elongating linearly gives rise to a colony enlarging symmetrically on an approximately uniform front through 360° from its centre. Most branches arise closely behind an existing elongating hyphal tip, and only a small number are formed on older parts of hyphae. The observed distances between successive points of of origin of hyphae fit a γ distribution with estimated shape parameter 1.5 and an estimated scale parameter of 0.011μm. The observed angles at which branches diverged from their parents' axes ranged within a normal distribution (mean 56° σ 17°). The first formed hyphae extend at about 20 μm per h for about 1 h after germination. Subsequently some stop growing permanently or temporarily; variation in the rates of elongation at the remaining tips, and at those branches formed after this first hour fits a half normal curve (mean 85 μm h−1). Growing hyphal tips repel each other, the maximum distances between tips at which this interaction has been seen range from about 10 μm to about 20 μm. No appreciable reorientation has been seen when living tips come close to dead ones, or if they approach agar sites from which another growing tip has been removed. The effects of moving growing tips close to older parts of the mycelium are less regular. Half of 68 observed cases stopped elongating, approximately one quarter (16) grew away from the older hyphae before making contact, approximately one quarter (18) crossed the older hyphae with no visible change in direction. Analysis of patterns produced by computer simulation indicates that the circular shape is the expected result of any system having the observed variation in branching and rates of elongation. No other controlling factor is needed to explain the patterns seen. In particular there is no evidence that orientating interactions between hyphal tips have any biologically important effect on colony shape. The amount to which the observed variation could be increased or reduced without affecting the growth patterns in any biologically important way is being studied.

Effects of fungicides on development of Entomophthora aphidis

Abstract: Three systemic fungicides (benomyl, ethirimol and tridemorph) and seven non-systemic ones (captafol, captan, fentin acetate with maneb, mancozeb, maneb, thiram and zineb) at concentrations recommended for field use inhibited germination of conidia of Entomophthora aphidis. All inhibited mycelial growth of the fungus in vitro, and benomyl, fentin acetate with maneb, maneb and thiram killed the fungus. Benomyl, tridemorph and thiram were aphicidal : each of the others, except captafol and zineb, decreased the infectivity of E. aphidis for living pea aphids, 6 h after they were treated topically with the fungicides. Each except captafol, zineb and maneb, was still active when the aphids were inoculated 48 h after treatment. When aphids were inoculated 4 h before treatment with fungicides, each of these except zineb, still decreased the infectivity of the fungus, although fungicide treatment 22 or 70 h after inoculation had little effect. The number of conidia discharged from infected aphid cadavers treated with the fungicides was diminished by benomyl and tridemorph and increased by captafol and captan.

Influence of pH on toxicity and uptake of copper in Aureobasidium pullulans

Abstract: A lowering from pH 45 of the initial pH of a medium containing 4 mM copper, reduced its toxicity to a copper-sensitive, and to a copper-tolerant strain of Aureobasidium pullulons At pH 45 the copper-tolerant strain takes up less copper than does the sensitive strain The lowering of pH from this level decreases copper uptake in both strains Variations of uptake with pH and between strains are suggested as the basis of differing sensitivities of strains to copper

Spatial patterns of sporophore distribution around a young birch tree in three successive years.

Abstract: Sporophores of three mycorrhizal fungi were found distributed around a young birch tree in the fifth, sixth and seventh years after planting in agricultural soil. The spatial patterns of distribution varied both between species and years. Sporophores of Lactarius pubescens increased in number, spread rapidly from close to the tree and were aggregated in increasingly tighter clumps. The number of sporophores and rate of spread from the tree of Hebeloma spp. declined and their aggregation into clumps became lax. The distribution of Laccaria laccata sporophores was comparatively static, moving outwards a small amount with numbers and clumping structure showing little net change. There were distinct arcs around the tree which were not occupied by sporophores of any species. Analysis of the association between species was complicated by the clumping. They tended to be negatively associated in the fifth season but subsequently overlapped and there was no consistent evidence of spatial inhibition between species. A distinction is drawn between the fairy ring frequently reported for saprophytic fungi of grassland and that for tree mycorrhizal fungi. Some evidence is considered that sporophore distributions reflect the closely adjacent occurrence of mycorrhizas and the processes which affect the colonization of tree root systems by mycorrhizal fungi.

Heterothallism in Bremia lactucae.

Abstract: It is shown that Bremia lactucae is capable of regular and predictable production of large numbers of oospores in lettuce tissues. Many isolates, while incapable of sexual reproduction when cultured alone, produced oospores in large numbers when cultured in combination with certain other isolates. This demonstrates the existence of heterothallism. In a survey of 39 isolates only two compatibility types were identified. These findings are discussed in relation to previous reports that sexual reproduction in B. lactucae is sporadic or does not occur at all. There was an inverse relationship between the intensities of sexual and asexual sporulation.

Pathogenicity of Alternaria and Cladosporium isolates on Phaseolus

Abstract: Phaseolus leaves were inoculated with conidia of Alternaria alternata, Cladosporium cladosporioides and C. herbarum. Plants were incubated in growth rooms at high humidity. Using light microscopy and cultural techniques it was shown that several of the isolates of all three species were able to penetrate into leaves via stomata. With many isolates most infections remained localized in the substomatal cavity. In other isolates, especially of Alternaria, a more extensive, intercellular mycelium developed. A few isolates also caused host mesophyll cells to become necrotic. These parasitic activities were correlated with an accelerated loss of chlorophyll from infected leaves and an increase in their levels of ribonuclease. These data suggest that some strains of these common filamentous phylloplane fungi are able to behave as weak parasites on herbaceous tissues. The use of fungicides which restrict their activity may result in yield increases over and above those attributed to the control of other, established pathogens.

Parasexuality in the deuteromycete Metarhizium anisopliae

Abstract: Auxotrophic and conidial colour mutants of Metarhizium anisopliae var. minor were obtained after ultraviolet treatment and used to demonstrate parasexual recombination. Heterokaryons between different mutants revealed that spore colour is non-autonomous. From heterokaryons, putative diploids were isolated. They differed from the parental strains by being prototrophic, by their spore-colour, DNA content and number and size of nuclei. In addition, they produced haploid sectors having parental markers when haploidization was induced by chloroneb. The discovery of parasexuality in M. anisopliae is important for basic genetic and applied studies in this species.

Two fungi parasitic on females of cystnematodes (Heterodera spp.)

Abstract: A nematode parasitic fungus, Nematophthora gynophila gen. et sp.nov. which attacks females of cyst-nematodes (Heterodera spp.) is described and placed in the Leptolegniellaceae Dick. Parasitized female nematodes fail to form cysts as the fungus destroys the body wall and cuticle and eventually replaces the body contents with a mass of resting spores. A Lagenidiaceous fungus is reported which also kills female cyst-nematodes. The release of zoospores by both fungi is described, and their significance in biological control is discussed.

Production of toxins and wall degrading enzymes by Gliocladium roseum

Abstract: Preparations of glucanases from Gliocladium roseum Bainier degraded glucans in Botrytis allii Munn hyphae. Increased β1–3 glucanase activity and the formation of chitinase occurred in cultures of B. allii parasitized by G. roseum. These results indicated that the disintegration of hyphal walls during parasitic attack was probably due to heterolytic enzyme action. Substances toxic to the host were detected in parasitized cultures; these were stable, partly, at least, of low molecular weight and effective over short distances only. Coagulation of cytoplasm and disintegration of hyphal walls occurred without physical contact between the hyphae of the two species; coiling of G. roseum hyphae around those of the host was infrequent and penetration rare, indicating that intimate contact between hyphae is not an essential part of the necrotrophic attack.

Growth of Serpula lacrimans in relation to water potential of substrate.

Abstract: Serpula lacrimans grows over lime-sand plaster containing more than 1% (w/w) water at a rate comparable to that on nutrient agar. When the water content of the plaster is lower, growth is reduced and occurs non-uniformly in a series of flushes. Growth under these conditions is stimulated by the addition of water or inhibited by the addition of 0.5 molal sucrose to the inoculum and the water content of the plaster is raised as the mycelium grows over it. Studies using agar and liquid culture show that the fungus cannot withstand water potentials of less than about −60 bars. Growth takes place on plaster at a much lower (−600 bars) water potential.

Origin of a new race of Puccinia striiformis

Abstract: Tests were carried out on the progeny of a mixture of two races of Puccinia striiformis Westd., following the inoculation of susceptible and differentially resistant cultivars. A new race designated 105E137 was identified from the mixed inoculation of races 104E137 and 33E32. The most likely mechanism responsible for production of the recombinant was reassortment of whole dikaryotic nuclei.

Germination and growth of Alternaria and Cladosporium in relation to their activity in the phylloplane.

Abstract: The effect of humidity, temperature and nutrient-poor conditions on conidial germination and hyphal growth of Alternaria alternata, Cladosporium cladosporioides and C. herbarum were studied in vitro. Alternaria conidia germinated quickly at high humidity, and in nutrient-free water its germ-tubes grew to form extensive hyphal networks. This development was accompanied by translocation of materials towards the hyphal apices, which resulted in a progressive increase in necrotic, ghost-like, hyphal compartments. Cladosporium conidia germinated irregularly and those of C. cladosporioides tended to form microcyclic conidia. Germ-tubes grew more slowly than those of Alternaria and ghost-like compartments were seen only after longer periods of incubation. Several physiological characteristics of the Cladosporium isolates, and their conidial dimensions, supported the morphological evidence which suggested that they represent two distinct species.

The fungal succession on decomposing sugar cane bagasse

Abstract: Nine species of fungi were isolated from the fungal succession on bagasse; Rhizopus microsporus, Mucor pusilius, Aspergillus fumigatus, A. niger, A. terreus, A. flavus, Penicillium sp., Trichoderma longibrachiatum and an agaric. The commonest species were A. fumigatus and A. terreus which were present throughout the 20 weeks of study. Maximum colony counts were recorded during the sixth to the thirteenth weeks of the succession. During the succession pH of the bagasse changed from acidic to neutral and finally became slightly alkaline, the moisture content gradually dropped and maximum temperature reached 50°C. Pectin was utilized by all nine bagasse fungi while cellulose was utilized by all except R. microsporus and M. pusilius . Xylan was utilized by all excepting R. microsporus , while αconidendrin was utilized only by A. niger .

Reciprocal translocation heterozygosity in heterothallic species of Phytophthora and its significance

Abstract: A multiple association of chromosomes, indicating heterozygosity for a reciprocal translocation, has been observed at meiosis in nine heterothallic Phytophthora species. In P. cryptogea Pethybr. & Laff., P. botryosa Chee and P. capsici Leonian, an association of four was observed in A1 × A2 crosses but it is not known if it is present in both mating types. In P. drechsleri Tucker,P. cinnamomi Rands, P. palmivora (Butl.) Butl. and P. megakarya Brasier & Griffin, the association of four has been found in both mating types. In P. megakarya, it has been observed in 4 A1 isolates and 1 A2 isolate and in P. palmivora in 12 A2 and 3 A1 isolates. The effect of heterozygosity for a reciprocal translocation on gene segregation of mitotic recombinants is discussed. It is suggested that the development of a stable heterothallic system in the 2 n mycelia Phytophthora depends on the suppression of mitotic segregation in the heterozygous mating type.

Conditions essential for controlled fruiting of macromycetes — A review

Abstract: Among the edible commercialized macromycetes in occidental countries, only two species ( Agaricus bisporus, Pleurotus ostreatus ) produce carpophores in controlled culture conditions. Most other species of interest to the consumer have not been domesticated for fruiting (e.g. Cantharellus cibarius, Lactarius deliciosous, Boletus edulis , various Morchella spp.). Nevertheless, during the last few years, encouraging results have been obtained for certain species ( Tuber, Macrolepiota procera , various Pleurotus spp.). In the Far East, numerous other macromycetes have been cultivated and commercialized ( Tremella spp., Auricularia spp., Flammulina velutipes, Volvariella volvacea, Lentinus edodes alias Shii-take). The control of fruiting necessitates a better understanding of the ecophysiology of these mushrooms. On-site observations, indispensable but not sufficient, must be complemented by laboratory experiments to define the influence of climatic factors on the initiation and development of carpophores, nutritional requirements of mushrooms and their physiological interactions with other micro-organisms.

Host infection by Claviceps purpurea

Abstract: Infection of wheat and rye by Claviceps purpurea and its subsequent sphacelial development was investigated by light and electron microscopy. Penetration occurred via the stigma and ovary wall and colonization was intercellular. Pectolytic enzymes were detected both in submerged cultures of the fungus and in infected ovaries and may play a part in parasitism. Initially, fungal growth was directed towards the ovule and vascular traces and, within about a week, the ovary was destroyed and replaced by fungal tissue (the sphacelium). Honeydew began to exude from infected florets at about this stage. Fungal penetration did not extend into the rachilla but remained distal to a core of thick-walled cells in the rachilla throughout parasitic development.

Observations on marine algicolous fungi, including the hyphomycete Sigmoidea marina sp.nov.

Abstract: Sigmoidea marina sp.nov., a marine hyphomycete growing on drift Fucus serratus and Laminaria saccharina , is described and compared with the freshwater hyphomycetes Anguillospora and Condylospora . Ascomycetes, Fungi Imperfecti and thraustochytrids isolated from seaweeds are listed, and Corollospora intermedia is recorded for the first time from British coastal waters.