Mycoparsitic behaviour ofFusarium oxysporum Schlechtendahl towardsAspergillus luchuensis Inui

Summary Mycoparasitic behaviour ofFusarium oxysporum Schlechtendahl towardsAspergillus luchuensis Inui was studiedin vitro. Growth of the hyphae ofF. oxysporum inside the hyphae and conidiophores ofA. luchuensis and formation of resting bodies ofF. oxysporum in conidiophores and hyphae ofA. luchuensis were observed. Bursting of the host hypha attacked by the parasitic hyphae was also noticed.     

Antagonistic interactions between fungal pathogens and phylloplane fungi of guava

Dominant phylloplane fungi of guava (Psidium guajava L.) were screened for their antagonistic activities against the two pathogens,Colletotrichum gloeosporioides andPestalotia psidii, bothin vitro andin vivo. Culture filtrates ofAspergillus niger, Fusarium oxysporum andPenicillium citrinum caused more than 50% growth inhibition ofC. gloeosporioides. Filtrates ofCephalosporium roseo-griseum andF. oxysporum were most effective in reducing the growth ofP. psidii. Volatiles produced from the cultures ofA. niger, F. oxysporum, P. citrinum andP. oxalicum inhibited the growth ofC. gloeosporioides, whereas volatiles fromC. roseo-griseum, F. oxysporum andTrichoderma harzianum inhibited the growth ofP. psidii. The inhibitory effect of volatiles decreased with increase in incubation time. In general, the maximum effect of volatiles was noticed after 48 h incubation. Different grades of colony interactions in dual cultures were recognised between the two pathogens and the phylloplane fungi examined. Maximum inhibition ofC. gloeosporioides was caused byAureobasidium pullulans, Cladosporium cladosporioides, epicoccum purpurascens, F. oxysporum andMyrothecium roridum, whereasAspergillus terreus, C. roseo-griseum andP. oxalicum significantly reduced the growth ofP. psidii. Application of a spore suspension of each test fungus inhibited lesion development of guava leaves caused by the test pathogensin vitro. Inhibition was more pronounced when the spore concentration was increased.A. pullulans, C. cladosporioides, E. purpurascens, F. oxysporum, andT. harzianum were found to be strongly antagonistic toC. gloeosporioides. A. niger, A. terreus, C. roseo-grisem andT. harzianum were strongly antagonistic toP. psidii.     

Three newAspergillus species isolated from clinical sources as a causal agent of human aspergillosis

Three new species ofAspergillus isolated from clinical sources in China are described and illustrated:A. beijingensis, A. qizutongii andA. wangduanlii. The first species is characterized by spreading colonies, yellow to grayish green conidial heads, smooth-walled conidiophores with a clavate vesicle, uniseriate aspergilla and nearly globose, micro-verrucose conidia. The second is characterized by spreading colonies, olive-yellow conidial heads, conspicuously roughened conidiophores with a flask-shaped vesicle, uniseriate but often secondarily proliferating aspergilla and globose, smooth conidia. The third is characterized by rapidly growing colonies, dull green conidial heads, smooth to irregularly roughened conidiophores which are often surrounded by coiled hyphae in the basal part and are terminally swollen into a globose or irregular shaped vesicle, uniseriate aspergilla and globose, micro-verrucose conidia.     

Colony interactions and mycoparasitism betweenAcremonium furcatum andAspergillus spp.

Summary Colony interactions and mycoparasitism betweenAcremonium furcatum and ten species of Aspergillus were studied in dual cultures. It was observed thatA. furcatum overgrew the colonies of all the ten species of Aspergillus studied. During the mycoparasitic interactions frequent coiling, penetration and growth of hyphae ofA. furcatum inside the conidiophores of six species of Aspergillus were observed.     

A rapid identification method for aflatoxin-producing strains ofAspergillus flavus andA. parasiticus by ammonia vapor

The colony reverse of aflatoxin (AF)-producing strains ofAspergillus flavus andA. parasiticus turned pink when their cultures were exposed to ammonia vapor. The color change was visible for colonies grown on media suitable for AF production such as potato dextrose, coconut, and yeast extract sucrose agars after 2 d incubation at 25°C. Of the 120 strains ofA. flavus, A. parasiticus, and two related species inA. flavus group:A. oryzae andA. sojae tested in this study, only the AF-producing strains ofA. flavus andA. parasiticus showed the pink pigmentation. The color change occurred immediately after the colony was contacted with ammonia vapor. This method was useful for rapid screening the AF-producing strains ofA. flavus andA. parasiticus.     

A newLeptographium species associated withTomicus piniperda in south-western China

Tomicus species (Coleoptera: Scolytidae) are serious pests of pines with a wide distribution in Europe, Asia and America. In Yunnan, south-western China,T. piniperda has destroyed more than 0.5 million ha ofPinus yunnanensis in the past 15 years. A blue stain fungus belonging to the genusLeptographium is associated with both the shoot-feeding and trunk-attacking stages of the beetle's life cycle. The fungus is morphologically similar to the anamorph ofOphiostoma crassivaginatum and toL. pyrinum, which are both characterised by short robust conidiophores and hyphae covered by a granular layer. Both these species have been isolated from conifers and are associated with insects. After comparing the fungus fromT. piniperda with similarLeptographium species, using light and scanning electron microscopy, we concluded that it represents a new taxon, which is described here asL. yunnanense sp. nov.     

Erythrogymnotheca,a new genus of Eurotiales

Erythrogymnotheca, a new genus of the Eurotiales, is proposed. The genus, based on the single speciesE. paucispora, is characterized by non-ostiolate ascomata with a telaperidium composed of an envelope of yellowish or reddish, branched, thin-walled hyphae, 1–2(-4)-spored asci, one-celled, subglobose to broadly ellipsoidal, thick-walled ascospores with spines, and the absence of an anamorph. The ascomatal initials ofE. paucispora are long clavate to vermiform, and reminiscent of those ofTalaromyces flavus.     

Morphological and physiological comparisons ofHelicobasidium mompa andH. purpureum

Morphological and physiological comparisons were made of sevenHelicobasidium mompa isolates and fourH. purpureum isolates. Colonies of theH. mompa isolates were thin, dense, or hard and dense, and most were pale brown to brown or dark brown, while that of isolate 344c was pinkish. Colonies ofH. purpureum isolates were hard and dense, and their colonies were dark brown. Diameters of hyphae were similar forH. mompa andH. purpureum. Dimensions of conidia and morphology of conidiophores ofH. mompa isolate 344c were close to those ofH. purpureum reported previously.H. mompa isolates grew well at 23°C, 25°C or 27°C, while all isolates ofH. purpureum grew well at 23°C. Growth rates ofH. purpureum isolates was almost the same as those ofH. mompa isolates with slow growth. Polygaracturonase activity at pH 3 was variable among the isolates for bothH. mompa andH. purpureum. Itaconic acid was produced abundantly by three isolates ofH. mompa but not produced by isolate AH130, whereas all isoaltes ofH. purpureum produced a small amount of itaconic acid.     

Comparison of four media for the isolation ofAspergillus flavus group fungi

Four agar media used to isolate aflatoxin producing fungi were compared for utility in isolating fungi in theAspergillus flavus group from agricultural soils collected in 15 fields and four states in the southern United States. The four media wereAspergillus flavus andparasiticus Agar (AFPA, 14), the rose bengal agar described by Bell and Crawford (BCRB; 3), a modified rose bengal agar (M-RB), and Czapek's-Dox Agar supplemented with the antibiotics in BC-RB (CZ-RB). M-RB was the most useful for studying the population biology of this group because it permitted both identification of the greatest number ofA. flavus group strains and growth of the fewest competing fungi. M-RB supported an average of 12% moreA. flavus group colonies than the original rose bengal medium while reducing the number of mucorales colonies and the number of total fungi by 99% and 70%, respectively. M-RB was successfully employed to isolate all three aflatoxin producing species,A. flavus, A. parasiticus andA. nomius, and both the S and L strains ofA. flavus. M-RB is a defined medium without complex nitrogen and carbon sources (e.g. peptone and yeast extract) present in BC-RB. M-RB should be useful for studies on the population biology of theA. flavus group.Abbreviations M-RB Modified Rose Bengal Agar - CZ-RB Czapeks Rose Bengal Agar - BC-RB Bell and Crawford's Rose Bengal Agar - AFPA Aspergillus flavus andparasiticus agar     

Cytochemical localization and ultrastructure of Aspergillus flavus in cottonseed

Cottonseeds having fluorescent fibers were harvested from fields in Arizona and examined utilizing light microscopy and transmission electron microscopy. The occurrence of fluorescent fibers indicated that seeds had been infected by Aspergillus flavus during development. Presence of A. flavus was verified by plating portions of seeds with fluorescent fibers. Hyphae, conidial heads, and conidia were identified readily in differentially-stained cotyledon tissue processed for light microscopy. Utilization of transmission electron microscopy permitted observations on lignified seed coats and cotyledons of mature cottonseeds. Hyphae were located throughout the cotyledon and in the nonlignified layers of the seed coat. The identification of hyphae in cross sections of vessel elements within the seed coat provided ultrastructural evidence supporting the hypothesis that A. flavus may enter seeds via the vascular tissue. Controls for the microscopy studies included observations on cottonseeds with no visual signs of infection and on laboratory-grown cultures of A. flavus. These observations demonstrated that the hyphae localized within fluorescent seeds had features characteristic of A. flavus and that fungal-like structures do not occur within uninfected seeds.     

Comparative efficacy of amphotericin B,clotrimazole and itraconazole againstAspergillus spp.

The susceptibilities of two isolates ofAspergillus flavus, one from a human case of recalcitrant mycotic keratitis, and an environmental isolate ofA. fumigatus, to itraconazole, clotrimazole and amphotericin B were measured. Observations of macroscopic growth and microscopic evaluations of conidia germination both indicated that the two isolates ofA. flavus were markedly more resistant to amphotericin B than to itraconazole and clotrimazole. Itraconazole was more effective than clotrimazole for all isolates. Ourin vitro susceptibility results suggest the use of itraconazole should be a primary consideration in the treatment ofAspergillus keratitis.     

Fusarium udum parasitic onAspergillus luchuensis andSyncephalastrum racemosum

Summary Mycoparasitic behaviour ofF. udum on two soil-inhabiting microfungi,Aspergillus luchuensis andSyncephalastrum racemosum, was studied in dual cultures.Fusarium udum coiled and penetrated the host fungi and formed chlamydospores inside their hyphae and reproductive structures. The vegetative hyphae ofA. luchuensis showed swellings due to diffusible toxic substances ofF. udum in the medium and formed vesicle-like structures. This is the first record of these fungi being hosts of the mycoparasiteF. udum.     

Influence of iturin A on mycelial weight and aflatoxin production byAspergillus flavus andAspergillus parasiticus in shake culture

Iturin A, a peptidolipid produced byBacillus subtilis, inhibits growth of a large number of fungi. In this study, the effects of iturin A were evaluated on nine isolates ofA. flavus and seven isolates ofA. parasiticus in liquid shake culture. The mycelial dry weight of theA. flavus isolates was not significantly influenced by iturin A, however, there was a significant reduction in mycelial dry weight for two of theA. parasiticus isolates. Aflatoxin production was significantly reduced in five of theA. flavus isolates and three of the six aflatoxigenicA. parasiticus isolates. For the other seven isolates, aflatoxin levels were either unchanged or significantly increased in the presence of iturin A. These results indicate that iturin A does not consistently reduce growth or aflatoxin production of these fungi in pure culture.     

Phylogenetic relationships ofCryptococcus neoformans and some related basidiomycetous yeasts determined from partial large subunit rRNA sequences

The genusCryptococcus was found to be heterogeneous on the basis of partial rRNA sequences. The human-pathogenic speciesC. neoformans, comprising 4 serotypes and havingFilobasidiella neoformans andF. bacillispora as teleomorphs, was found at a relatively large distance fromFilobasidium. Serotypes B and C had identical sequences, while in A and D they were different, with D closer to B and C than to A.Filobasidiella depauperata, which lacks a yeast-like anamorph, clustered withF. neoformans.The genusFilobasidium was clearly separated fromFilobasidiella and clustered withC. albidus, C. kuetzingii, C. gastricus, C. lupi, C. vishniaciae, C. bhutanensis, C. aerius, C. terreus andC. ater. The latter may represent the anamorph ofFilobasidium elegans. The organe to red species ofCryptococcus, as well asC. aquaticus andC. yarrowii, were found completely unrelated with these taxa,C. macerans being affiliated toCystofilobasidium capitatum.The genusTrichosporon was found relatively homogeneous; it includesC. humicola, C. curvatus and the filamentous speciesHyalodendron lignicola. Cryptococcus flavus andC. dimennae probably belong to the Tremellales, though distances between these species are large. The positions ofC. laurentii andC. luteolus remains to be determined.     

Influence of formic acid on fungal flora of barley and on aflatoxin production inAspergillus flavus link

In recent yearsAspergillus flavus and aflatoxin production have been noted on several occasions in grain preserved with formic acid. Samples of mouldy barley treated with formic acid and stored in an open bin were investigated for the presence of fungi. In the lower part of the bin there was a clear dominance ofFusarium sporotrichioides, and deoxynivalenol and neosolaniol were detected.A. flavus andA. fumigatus were also present.Paecilomyces variotii occurred, almost as a pure culture, in the upper part of the bin, but no patulin was found. Cultivation of four fungal isolates from these genera on laboratory substrates containing formic acid showedP. variotii to be the most tolerant to formic acid, withstanding 150 mM, but still without patulin production.F. sporotrichioides andA. fumigatus tolerated only 6 mM formic acid. The growth ofA. flavus was reduced and atypical at 60 mM formic acid. Pretreatment ofA. flavus spores with formic acid increased aflatoxin production about 800 times.     

Preharvest seed infection byAspergillus flavus group fungi and subsequent aflatoxin contamination in groundnuts in relation to soil types

Preharvest seed infection byAspergillus flavus and aflatoxin contamination in selected groundnut genotypes (fourA. flavus-resistant and fourA. flavus-susceptible) were examined in different soil types at several locations in India in 1985–1990. Undamaged mature pods were sampled at harvest and seed examined forA. flavus infection and aflatoxin content in two or more trials at ICRISAT Center on light sandy soils and red sandy loam soils (Alfisols), and on Vertisols, at Anantapur on light sandy soils, and at Dharwad and Parbhani on Vertisols. Rainy season trials (1985–1989) were all rainfed. Post-rainy season trials were irrigated; late-season drought stress (90 days after sowing (DAS) until harvest at 125 DAS) was imposed in the 1987/88 and 1989/90 seasons.A. flavus infection and aflatoxin contamination levels were much lower in seed of all genotypes from Vertisols than in seed from Alfisols across locations and seasons. Vertisols also had significantly lower populations ofA. flavus than Alfisols. There were no marked differences between light sandy soils and red sandy loam soils (Alfisols) in respect of seed infection byA. flavus and aflatoxin contamination. Significant interactions between genotypes and soil types were evident, especially in theA. flavus-susceptible genotypes. Irrespective of soil types,A. flavus-resistant genotypes showed lower levels of seed infection byA. flavus and other fungi than didA. flavus-susceptible genotypes. The significance of the low preharvest aflatoxin risk in groundnuts grown on Vertisols is highlighted.ICRISAT Journal Article No. JA 1122     

Development of a serial bioreactor system for direct ethanol production from starch using<Emphasis Type="Italic">Aspergillus niger</Emphasis> and<Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Aspergillus niger hyphae were found to grow with unliquefied potato starch under aerobic conditions, but did not grow under anaerobic conditions. The raw culture ofA. niger catalyzed saccharification of potato starch to glucose, producing approximately 12 g glucose/L/day/ The extracellular enzyme activity was decreased in proportion to incubation time, and approximately 64% of initial activity was maintained after 3 days. At 50°C,A. niger hyphae growth stopped, while the extracellular enzyme activity peaked. On the basis of theA. niger growth property and enzyme activity, we designed a serial bioreactor system composed of four different reactors. Fungal hyphae were cultivated in reactor I at 30°C, uniquefied starch was saccharified to glycose by a fungal hyphae culture in reactors II and III at 50°C, and glucose was fermented to ethanol bySaccharomyces cerevisiae in reactor IV. The total glucose produced by fungal hyphae in reactor I and saccharification in reactor II was about 42 g/L/day. Ethanol production in reactor IV was approximately 22 g/L/day, which corresponds to about 79% of the theoretical maximum produced from 55 g starch/L/day.     

Behaviour of the hyphae of<Emphasis Type="Italic"> Laccaria laccata</Emphasis> in the presence of<Emphasis Type="Italic"> Trichoderma harzianum</Emphasis> in vitro

The growth rate and the behaviour of Laccaria laccata and Trichoderma harzianum hyphae in co-culture and in the rhizosphere of 3-month-old Pinus sylvestris seedlings grown in vitro were investigated. In the interaction zone, hyphae of L. laccata became more pigmented and formed short branches growing towards the hyphae of the saprobic fungus, coiled around them and penetrated sporadically. Vacuolated hyphae of T. harzianum showed protoplasm granulation and breaks in walls followed by release of protoplasts. In the rhizosphere, the mantle hyphae of L. laccata showed a tendency to surround conidia of T. harzianum. No obvious penetration of the conidial walls by the hyphae of the mycorrhizal fungus was observed by scanning electron microscopy. Instead, in rare cases, the hyphae of L. laccata showed marked wrinkles, and a partial degradation of a mucilaginous material covering the mantle appeared to occur.     

Aseptic ectomycorrhizal synthesis betweenAbies firma andCenococcum geophilum in artificial culture

A simple in vitro system is described for the synthesis ofAbies firma-Cenococcum geophilum ectomycorrhizas. SterilizedA. firma seedlings on both MMN and FH media were inoculated with hyphal discs from actively growing margins ofC. geophilum colonies. Typical ectomycorrhizas formed on seedlings on FH medium after 3 mo of incubation. By light microscopy, the synthesized mycorrhizas were seen to possess a thin mantle from which emanated extraradicle hyphae and highly branched, rarely septate intracortical Hartig net mycelium, characteristic ectomycorrhizal features. This is the first report of aseptic ectomycorrhization ofA. firma seedlings byC. geophilum. This model system will facilitate detailed studies on ectomycorrhizal development ofAbies species.     

Aspergillus salviicola,a new species from imported spice

A new species ofAspergillus, A. salviicola, has been isolated from Turkish sage, an imported spice in Japan. The species, characterized by white to rosy buff conidial heads, pinkish smooth-walled conidiophores, large biseriate aspergilla, globose smooth-walled conidia, absence of sclerotia and thermotolerant growth, is considered to represent an interface species in the subgenusCircumdati.