Showing papers in "Transactions of The British Mycological Society in 1983"

Spore dormancy in vesicular-arbuscular mycorrhizal fungi

Abstract: Spores of four species of VA mycorrhizal fungi were unable to germinate when first formed. The change in their capacity to germinate was examined by using populations of newly-formed spores with a narrow age range. Percentage germination and length of hyphae produced by the spores when incubated in soil or on nutrient agar media was measured during storage at constant temperatures between 5 and 37 °C in both wet (−0.15 MPa) and dry (−300 MPa) soil. The results supported the hypothesis that spores of these species were innately dormant when first formed and suggest that changes occurred with close synchrony. The dormancy period in wet soil was approximately 6 weeks for Glomus caledonium and G. monosporum , and 12 weeks for Gigaspora calospora . This period was significantly reduced to 1 week for the Glomus spp. and 6 weeks for Gigaspora calospora in dry soil. For Acaulospora laevis the dormancy period was 6 months under all conditions. Plant roots had no effect on the change to quiescence of spores of any species, however newly-quiescent spores were effective propagules.

Effect of temperature and water potential on growth rate of wood-rotting basidiomycetes

Abstract: Radial growth of twelve species of wood-rotting basidiomycetes was examined over a range of temperatures on malt agar: optimum growth rate occurred at between 20 and 30 °C. Variability in growth rate of several different isolates of five of the species was assessed at 10° and 20°. A significant difference in growth rates of different isolates was found in four species at 20° but only in one species at 10°. No significant difference was detected between the Q10 coefficients of different isolates of a species. The effect of water potential on growth rate was investigated for one isolate of each of the twelve species using four different solute systems and two types of agar media. Differences were detected between the solute systems and media although a general trend of decrease in growth rate with decrease in water potential was observed. The limit for growth was about −4.4 MPa (− 45 bars).

Comparisons of fungal melanin biosynthesis in ascomycetous, imperfect and basidiomycetous fungi

Abstract: Melanin biosynthesis was studied in 26 species of fungi belonging to 16 genera using the melanin inhibitor tricyclazole (5-methyl-1,2,4-triazolo(3,4 b )-benzothiazole) and enzyme reactions in cell-free homogenates. All but one of the 20 dark brown and black ascomycetous and imperfect fungi apparently made melanin from 1,8-dihydroxynaphthalene. Cell-free homogenates of these fungi metabolized two or more melanin substrates (1,3,6,8-tetrahydroxynaphthalene, (+)-scytalone, 1,3,8-trihydroxynaphthalene or vermelone) to intermediates in the melanin pathway, including 1,8-dihydroxynaphthalene, and/or the melanin biosynthetic pathway in these fungi was blocked in vivo by tricyclazole, causing a change in fungal colour and an accumulation of 2-hydroxyjuglone, flaviolin, and other melanin shunt products. Aspergillus niger and six basidiomycetes did not metabolize these melanin substrates, and melanin biosynthesis in these fungi was not affected by tricyclazole. Thus, many ascomycetous and related imperfect fungi appear to make melanin from 1,8-dihydroxynaphthalene, whereas basidiomycetes and at least some imperfect fungi probably use alternative pathways.

Production of copper oxalate by some copper tolerant fungi

Abstract: Aspergillus niger, Penicillium spinulosum, Verticillium psalliotae and Porta placenta cause the formation of copper oxalate crystals when grown in a copper containing medium. Results are discussed in relation to the copper tolerance mechanisms of those fungi.

Temperature relations of spore germination and hyphal growth of vesicular-arbuscular mycorrhizal fungi in soil

Abstract: Spores of Glomus caledonium, Gigaspora calospora and Acaulospora laevis from the same source and grown under the same conditions had different temperature limits for germination. Within these limits, temperature affected the duration of the period between imbibition and the onset of germination. Over most of the range, for each fungus, temperature caused no change in either the proportion of the spores which germinated, the time (after onset of germination) taken for the maximum proportion to germinate or the rate and extent of hyphal growth. At temperatures close to the limits, the rate of both spore germination and hyphal extension were decreased. The upper temperature limits for germination were less than those in moist soils in the natural habitat of the fungi, a feature which may have an ecological role.

Role of organic matter in growth of a vesicular-arbuscular mycorrhizal fungus in soil

Abstract: Vesicular arbuscular mycorrhizal fungi can grow saprophytically in soil. Results show that organic matter is an important factor in this process.

Distinction between Sclerotinia species by their pectic zymograms

Abstract: Zymograms of the extracellular pectic enzymes of Sclerotina sclerotiorum, S. minor and S. trifoliorum were prepared by electrophoresis of untreated fluid from liquid cultures. Each species gave a distinctive zymogram which allowed a rapid and non-subjective identification.

Extent, development and function of mycelial cord systems in soil

Abstract: Mycelial cord systems of Phallus impudicus, Phanerochaete velutina, Steccherinum fimbriatum, Stropharia aeruginosa and Tricholomopsis platyphylla, when excavated in the field, were found to be between 318 m (5. aeruginosa) and 317 m (P. velutina) in overall length. Cord systems of P. impudicus, P. velutina and T. platyphylla increased in length by 0.8, 0.95 and l.0 m respectively over 12–14 months. In all cases extension occurred via the peripheries of the systems, whilst certain more central parts disappeared. Mycelial development from colonized wood-blocks in tubes of non-sterile soil showed similar patterns to that observed in the field. However, in tubes of γ-irradiated soil mycelia were not aggregated into cords to such an extent as in non-sterile soil, and, except for T. platyphylla, had slower extension rates, although sometimes being more luxuriant. Wood-blocks colonized by Hypholoma fasciculate, S. fimbriatum, P. impudicus and P. velutina underwent significantly greater losses in dry weight in sterile soil than did blocks in non-sterile soil, except for those colonized by T. platyphylla. Cord systems of like and unlike mycelial types of P. velutina from wood blocks fused in soil, but whilst fusion of those of like mycelial type gave rise to cords of substantial diameter, fusions between different mycelial types were followed by death of the fine cords in the fused regions and avoidance of such regions thereafter. Cord formation by a coprophilous species occurred in non-sterile but not sterile conditions, and was associated with strong substratum directed growth responses.

What are phialides anyway

Abstract: The history of the term phialide is outlined. The way the term has been used is analysed and found to be confused. Four problems are identified: nobody in recent years has used the term in its original sense ; nobody is agreed on what a typical phialide is; nobody can be certain what anyone else means by the term; the term is promoting the very artificial classification it was introduced to avoid. The reasons for these problems are discussed, and four other terms (aleuriospore, annellide, blastic and thallic) subject to the same difficulties are identified. It is concluded that none of these words can be used as unambiguous, precise scientific terms, but that they can still have a function as vague words describing general symptoms.

Armillaria species from south-eastern Australia

Abstract: Armillaria hinnulea spnov and A fumosa spnov are described Armillaria novae-zelandiae is fully described and its occurrence in Australia documented Armillaria novae-zelandiae and A hinnulea occur widely in wet forests in south-eastern Australia, the former in cool temperature rainforest and mixed forest, the latter in mixed forest and wet sclerophyll eucalypt forest Armillaria fumosa is so far only known from poorly drained or seasonally wet locations within dry sclerophyll eucalypt forest Morphological characteristics of vegetative isolates can be used to differentiate between A hinnulea, A novae-zelandiae and A fumosa although isolates of the latter species cannot be differentiated from those of another Australian species, A luteobubalina The new combinations Armillaria bulbosa, A fellea, A griseomellea, A montagnei and A sparrei are proposed

Aquatic hyphomycetes in sixteen streams in France, Germany and Switzerland

Abstract: Sixteen streams in the Black Forest, Vosges, Swiss Jura and Napf regions with different geology and climate, reflected by variations in water chemistry and riparian vegetation, were investigated for aquatic fungal communities. Linear correlation and regression analysis as well as χ2-tests indicate that fungal species richness is negatively correlated with pH and associated factors (conductivity, alkalinity, calcium and magnesium content) whereas the riparian vegetation shows no influence. In contrast, average annual spore concentration in the streams is little influenced by the water chemistry, but is significantly connected with the riparian vegetation. A similarity index (Sorensen index) indicates that similarity between the different fungal communities is highest within the same regions and is dissimilar when communities of different regions are compared.

Aphid honeydew, a potential stimulant of Cochliobolus sativus and Septoria nodorum and the competitive role of saprophytic mycoflora

Abstract: The effect of aphid honeydew on fungal leaf saprophytes and pathogens was studied on wheat under controlled environmental conditions. When honeydew was added to the inoculum, the colonization of flag leaves by a mixed population of Sporobolomyces roseus, Cryptococcus laurentii var. flavescens, Aureobasidium pullulons and Cladosporium cladosporioides was highly stimulated. After an exponential growth period of about 6 days, the population densities of all showed a tenfold increase in the presence of honeydew. Honeydew added to the inoculum of Septoria nodorum or Cochliobolus sativus enhanced the degree of infection of wheat leaves by these pathogens 2.5–4 times. During the prepenetration development of C. sativus, honeydew stimulated spore germination, the formation of two germ-tubes per conidium and germ-tube growth. Addition of saprophytes to the inoculum, enriched with honeydew, reduced the stimulation of infection in one experiment only where high population densities were reached within one day, but application of honeydew 4–5 days before inoculation, always resulted in an abundant population of naturally occurring saprophytes which completely neutralized the honeydew effect. Carbohydrate determinations of washings from leaves treated with artificial honeydew, revealed a decrease in washable carbohydrates from 450 to 40 μg ‘glucose’ cm−2 leaf within 7 days, with a simultaneous increase in the number of saprophytes from less than 104 to 4.106 C.F.U. cm−2. The implications of these results for the interpretation of secondary effects of aphids on the yield of wheat are discussed.

A comparison of some preservation techniques for fungi

Abstract: Of 58 fungi covered in mineral oil in 1950, 47 were viable after 32 years storage and 7 of those not surviving the full period remained viable for 20 years or more Oil storage remains a useful alternative to liquid-nitrogen storage for isolates of Phytophthora, Pythium , basidiomycetes and mycelial forms which do not readily survive freeze-drying Storage in anhydrous silica gel was compared with oil, freeze-drying and liquid-nitrogen storage techniques as a cheap alternative More stable and consistent growth was achieved after storage in silica gel than under oil though the range of fungi surviving was much narrower Although some of the plectomycetes, hyphomycetes and zygomycetes tested survived 11 years in silica gel in good condition, the technique was not as successful as freeze-drying or liquid-nitrogen storage but was considered to be a useful alternative for laboratories with limited resources or those requiring a simple technique

Microdochium stoveri and Monographella stoveri, new combinations for Fusarium stoveri and Micronectriella stoveri

Abstract: Colonies derived from single ascospores of Micronectriella stoveri produced Fusarium stoveri in agar culture. The teleomorph had a paraphysate locule and an amyloid ascal apex, which places it in Monographella as M. stoveri (Booth) comb.nov. In the anamorph conidiogenesis was holoblastic, with conidiogenous cells either determinate or proliferating sympodially. Annellations were not seen either in optical or in scanning electron microscopy. The formation of annellations per se was rejected in defining genera. The anamorph of M. stoveri was found to be congeneric with anamorphs of other species of Monographella in which conidiogenesis is holoblastic-annellidic and which have been placed in Gerlachia. G. nivalis and the anamorph of M. stoveri were compared with Microdochium phragmitis , type species of Microdochium , and found to be congeneric. Gerlachia is considered to be a taxonomic synonym of Microdochium and the following new combinations were proposed: M. nivalis (Fries) comb.nov., M. nivalis var. majus (Wollenweber) comb.nov., M. oryzae (Hashioka & Yokogi) comb.nov. and M. stoveri (Booth) comb.nov.

Competitive interactions amongst four species of Glomus on maize and onion

Abstract: Maize and onion plants were infected with four species of Glomus in all fifteen possible combinations. Growth of maize was enhanced similarly in all treatments whereas onion plants showed differential growth effects. Inocula containing more than one endophyte gave more consistent results, although spore yields were lower, in mixed inocula compared with inocula of single species. G. clarum spored prolifically throughout the treatments. Maize plants produced three times the number of spores compared with onions. G. clarum was a good competitor and G. caledonium much less efficient. Mixed inocula are suggested for field inoculations.

Desert truffles: The genus Tirmania

Abstract: The genus Tirmania and its two species, T. nivea and T. pinoyi, are redescribed. They are distinct from other desert truffles in having asci that become blue to green in Melzer's reagent and hyaline, double-walled spores with a smooth outer wall and minutely reticulate-roughened inner wall. Both species form mycorrhizae with annual Helianthemum spp. and are known only from gypsiferous, saline, or gypsiferous-saline, gravelly deserts in North Africa and West Asia. They have been prized from ancient times as a nutritious, seasonal food. If cultivation methods can be developed for ensuring dependable annual yields of desert truffles, many deserts used now only for spring grazing could produce significant amounts of additional food.

Cultural and pathogenic variation in potato isolates of Rhizoctonia solani in Northern Ireland

Abstract: One hundred and eighty two isolates of R. solani from sclerotia on tubers of various potato cultivars grown in 24 different locations in N. Ireland showed wide variation in cultural characteristics. The pattern of sclerotial formation, being the most stable and well-defined character of each isolate, was used to divide them into six groups. Attempts to anastomose these with test strains of anastomosis groups (AG-1, AG-2 type 1, AG-2 type 2, AG-3, AG-4 and AG-5) showed that all isolates in N. Ireland groups 1–5 anastomosed with AG-3 and those in group 6 only with AG-2 type 1. Mycelial growth of group 6 was slower and hyphal diameter smaller compared with that of other groups. Pathogenicity tests on 5 potato cultivars (Arran Banner, Arran Consul, Bintje, Dunbar Standard and Pentland Dell) showed that the isolates in groups 1–5 (AG-3) caused significantly more stem canker and black scurf than those of group 6 (AG-2 type 1).

Osmotic sensitivity of fungal variants resistant to dicarboximide fungicides

Abstract: Fungicide-resistant variants of Botrytis cinerea, Penicillium expansum and Aspergillus nidulans were selected on media amended with the dicarboximide fungicide iprodione. A total of 58 were scored for osmotic sensitivity by comparing the extent to which their radial growth was inhibited by adding 0.68 m sodium chloride to the basal medium with that of their parents. The majority (49) were abnormally osmotically sensitive, but within this group there was no consistent relationship between degree of osmotic sensitivity and degree of fungicide resistance. The remaining nine osmotically insensitive variants were, however, all of only low fungicide resistance. The radial growth rates and conidiation of the resistant variants were very diverse, and bore no obvious relationship either to their degree of osmotic sensitivity or to their degree of fungicide resistance. Two of the A. nidulans variants were almost aconidial on basal medium, but conidiated abundantly on medium amended with iprodione. The correlation between osmotic sensitivity and dicarboximide resistance is discussed in relation to the infrequent occurrence, to date, of practical problems associated with dicarboximide resistance.

Chemical composition of the resting spore wall of Plasmodiophora brassicae

Abstract: Walls of the resting spores of Plasmodiophora brassicae were isolated mechanically and analysed quantitatively for their major components. At least 88 % of the spore wall dry weight was accounted for and shown to comprise 25.1% chitin, ≥ 2.5% other carbohydrates, 33.6% protein and ≥ 17.5% lipid while residual ash was equivalent to 10.5% of the total weight; chitosan and cellulose were absent from the walls. The significance of the abnormally high levels of protein and lipid is discussed.

Mycelial interactions, morphogenesis and ecology of Phlebia radiata and P. rufa from oak

Abstract: Attached or fallen branches of oak ( Quercus robur ) colonized by Phlebia radiata and P. rufa were collected from locations in South-West Britain, and the patterns of decay within the branches analysed. Isolates were cultured from decayed wood, fruit-body tissue and from single basidiospores. Isolates were paired on malt agar in various combinations and also against other species of decay fungi. Bipolar incompatibility was found in both species, although P. rufa behaved inconsistently, and intraspecific pairings between genetically different dikaryons were mutually antagonistic. Pairings between the two species always resulted in strong mutual antagonism, immediately after hyphal fusion, and no dikaryons with clamp connexions were formed between homokaryons. Both species tended to replace other decay fungi in culture, but P. radiata was generally the more successful. All of the above interactions appeared to depend on contact with septate mycelia. Colonies of both species on agar extended relatively rapidly from a wide peripheral zone of appresed, mostly coenocytic mycelium which generally lacked hyphal fusions. Behind this zone, which was wider in P. radiata than in P. rufa , hyphae with clamp connexions developed and aerial mycelium was formed. The aerial mycelium of P. rufa was generally rather localized and rapidly aggregated into small hymenial surfaces on homokaryotic and dikaryotic mycelia. P. radiata formed a much more diffuse, floccose aerial mycelium which formed hymenia only occasionally on old cultures. Homokaryotic and dikaryotic cultures of both species produced oidia, although P. rufa did so more abundantly and more consistently than P. radiata . The cultural differences between the two species were correlated with differences in their ecology: P. radiata is regarded as a secondary colonizer, but P. rufa is probably a pioneer colonizing weakened, but still-living wood.

Protease, phenoloxidase and pectinase activities in mycorrhizal fungi

Abstract: Protease and phenolidase activities in mycelial extracts of Suillus variegatus, S. bovinus, Pisolithus tinctorius, Piloderma croceum, Paxillus involutus, Amanita muscaria and Fomes annosus was demonstrated. Pectinase activity was not detected in culture filtrates and was very low or absent in all mycorrhizal fungi tested.

Effect of Junlon on morphology of Aspergillus niger and its use in making turbidity measurements of fungal growth

Abstract: Aspergillus niger formed pellets when grown in submerged, shake flask culture. However, when the acrylic resin, Junlon (2 g l −1 ) was added to the medium, the mould grew as disperse, filamentous mycelia, and under these conditions culture turbidity was a reliable parameter of culture biomass.

Anaerobic survival of aquatic fungi

Abstract: Aero-aquatic Hyphomycetes were tested for their ability to survive on beech leaf disks under anaerobic conditions for periods of up to 12 months. Helicodendron triglitziense, H. conglomeration and H. giganteum showed 100% survival, while H. luteo-album and H. hyalinum showed reduced survival. Survival of aero-aquatic Hyphomycetes, Ingoldian aquatic Hyphomycetes and members of the Saprolegniales was also compared on hemp seeds under anaerobic conditions. Aero-aquatic Hyphomycetes showed the greatest percentage survival. Articulospora tetracladia, Achlya colorata (isolate lacking oospores) and Dictyuchus sterilis failed to survive even 3 months. No significant difference was found in the survival of Tricladium splendens from a stagnant drainage ditch and from a fast-flowing river. Only species of Saprolegniales with oospores survived anaerobic conditions.

Invasive and developmental processes of Entomophthora muscae infecting houseflies (Musca domestica)

Abstract: Germ-tubes of Entomophthora muscae penetrate any part of the cuticle of Musca domestica, but most frequently that of the abdomen, at or very near the point where the conidium adheres. A triradiate fissure is produced in the surface of the cuticle where the germ-tube enters, and penetration proceeds by enzymic and mechanical means, causing local melanization. Inside the host the germ-tube expands to a bladder-like hypha from which develop hyphal bodies. These are disseminated and multiply throughout the host in the haemocoel but are most numerous in the abdomen, where they invade first the fat and then other tissues, causing death of the host. Conidiophores then develop and emerge from the adjacent intersegmental membranes whilst tissues in the head, thorax and appendages remain almost unattacked. By 12 h after death all parts become invaded and conidiophores emerge from intersegmental membranes all over the fly. Dead flies are frequently attached to the substrate by their proboscis. This phenomenon has not been explained, but the fungus does not form specialized attachment structures.

Variation in symbiotic activity of Rhizoctonia isolates from Goodyera repens mycorrhizas

Abstract: Numerous isolates of mycorrhizal fungi from roots of the orchid Goodyera repens were identified as Rhizoctonia goodyerae-repentis and had similar characteristics in culture. All formed compatible intracellular infections in germinating seeds of G. repens but there was considerable variation in their ability to stimulate growth of seedlings. Symbiotic activity and some mycelial characteristics of isolates stored on agar and those maintained on plants changed after one year in culture. The activity of most isolates declined, but to varying extents, and the cause of this variability is not known. Two (unidentified) isolates did not establish a symbiosis with G. repens in culture.

Some Verticicladiella species, including V. truncata sp. nov., associated with root diseases of pine in New Zealand and South Africa.

Abstract: Verticicladiella procera and two undescribed Verticicladiella species were identified from a collection of Verticicladiella isolates associated with a Pinus strobus L. root disease in New Zealand. One of the undescribed Verticicladiella species was also isolated from diseased roots of Pinus taeda L. in South Africa and is described as V. truncata sp.nov. V. truncata was found to be pathogenic and is carried by a scolytid bark beetle.