Rabbit pellets collected from the field were colonized by Podospora pleiospora at the exclusion of other coprophilous fungi, suggesting antibiosis. In liquid culture, P. pleiospora produced sordarin (1); sordarin B (2), a new compound in which sordarose is replaced by rhamnose; hydroxysordarin (3); and sordaricin (4). The major compounds 1 and 2 exhibited minimum inhibitory concentrations of 0.5–2.5 μg ml−1 against the yeasts Nematospora coryli and Sporobolomyces roseus, but showed little or no activity against bacteria or coprophilous filamentous fungi. In liquid culture, the production of 1 and 2 together amounted to 2.7 μg ml−1, whereas in rabbit dung only 1 was produced at a similar concentration (2.3 μg g−1 fresh weight). The biosynthesis of these substances was unaffected by the presence of inoculum of other fungi tested (Sporobolomyces roseus or Penicillium claviforme) in liquid culture or on dung. Sordarin-type natural products are therefore synthesized by P. pleiospora at sufficiently high concentrations to account for antibiosis against yeasts, but not against filamentous fungi.

Phoma medicaginis was isolated as the dominant endophyte from surface-sterilized shoots of Medicago sativa and M. lupulina growing outdoors. Plants were either symptomless or showed signs of infection in the shape of limited lesions which sometimes contained melanized pycnidial initials. Rapid colonization of host tissue and sporulation were observed within 9 d on dead plant material upon incubation in a moist chamber. Such colonized material, but not freshly harvested living tissue, contained brefeldin A (1.7 μg g−1D.W.). This toxin was also produced in pure culture (20 mg l−1) and in artificially inoculated autoclaved M. sativa stems (3 mg g−1D.W.=920 μg ml−1). The latter concentration of brefeldin A should be similar to that produced within a fruiting lesion of P. medicaginis and suppressed spore germination and growth of nine of 11 common phylloplane fungi tested. This metabolite may thus have a function in substrate defence after the switch from the endophytic to the saprotrophic period in the life-cycle of P. medicaginis following the death of infected host tissue.

The life-cycle of many plant-pathogenic fungi, especially those infecting aerial plant organs, contains several specific developmental stages. If these are sufficiently distinct in their physiology from vegetative hyphal growth, they present potential targets for non-fungitoxic plant protectants. The present review identifies such targets especially in the pre-penetration stages of the infection cycle of Magnaporthe grisea and other fungi infecting from air-borne spores. Examples of non-toxic natural products with activity against spore germination, attachment, appressorium formation, appressorium maturation and penetration of the host surface are given. In contrast, no substances selectively active against in planta growth or sporulation appear to be known. The selective activity of numerous secondary metabolites against specific infection stages without accompanying toxicity against vegetatively growing hyphae indicates a direction for the development of future natural product-derived fungicides which are more easily degraded in the environment and possess fewer non-target effects. Such substances are produced by many saprotrophic and endophytic fungi in pure culture. The paucity of data on the production of biologically active substances in natural situations limits the interpretation of their ecophysiological significance for the producer.

Sunflower oil poured onto compost in November induced massive growth of Mortierella species. Mortierella hyaline was isolated into culture at 4 or 18 °C on weak media but not at 23-25 °C or on 2% malt agar. It grew well on olive oil agar, with its hyphae aggregating inside oil drops. The nature of nutrients utilized in normal soils and composts by Mortierella is not known but lipid levels there would appear to be low. Many Mortierella species are able to convert diverse carbon sources into lipids and are thus known as oleaginous fungi. Their biotechnological applications are briefly discussed.

Names of fungi

1. Sclerotinia curreyana (Berkeley ex Currey) P. Karsten = Myriosclerotinia curreyana (Berkeley ex Currey) Buchwald; conidial state Myrioconium Sydow

2. Sclerotinia Fuckeliana (de Bary) Fuckel = Botryotinia fuckeliana (de Bary) Whetzel; conidial state Botrytis cinerea Persoon ex Fries

3. Sclerotinia fructigena (Persoon) Schröter = Monilia fructigena Honey ex Whetzel; conidial state Monilia fructigena (Persoon) Eaton

Introduction: Features of interest

Members of the Sclerotiniaceae are plant pathogens characterized by stalked apothecia with inoperculate asci. Apothecia arise from stromata, e.g. sclerotia which are formed on or in the tissue of the host plant. The apothecial state and the type of stroma are typical and taxonomically relevant features of the Sclerotiniaceae, and the family has been supported and delimited by DNA sequence data (Carbone & Kohn, 1993; Holst-Jensen et al., 1997a,b).

Name of fungus

Phaffia rhodozyma W. M. Miller et al.

Introduction: Features of interest

Carotenoids are a group of over 600 molecules which can be found in most life forms and fulfil diverse functions, ranging from their original evolutionary role as photosynthetic or light-quenching pigments to antioxidants, precursors of vitamin A, or pigments involved in the visual attraction of animals such as flower pollinators or mating partners (Johnson & Schroeder, 1995). They are also thought to reduce the incidence of cancer and degenerative diseases in man, probably due at least partly to their antioxidant role in protecting sensitive biological molecules from highly reactive oxygen species or free radicals (Bendich & Olson, 1989; Nishino et al., 1999). Carotenoids are synthesized de novo by many bacteria, all photosynthetic algae and higher plants, as well as some fungi, but not by animals which must therefore satisfy any carotenoid requirement they have from their diet. Thus, for instance in marine ecosystems, planktonic algae are thought to be the primary producers of carotenoids which then pass through the food chain, eventually accumulating in crustaceans and fish feeding on them (Johnson & Schroeder, 1995). This is true especially of astaxanthin, a natural derivative of the most abundant carotenoid, ß-carotene, which gives many marine crustaceans as well as salmonid fish their typical orange-red colouration (Johnson & An, 1991). Considerable quantities of astaxanthin must be added to the feed of farmed salmon in order to obtain a healthy crop of fish as well as satisfying the eye of the consumer (Meyers, 1994). Astaxanthin may even contribute to the taste of cooked salmon (Josephson et al., 1991).

Phylogenetic analyses of the ITS1-5.8S-ITS2 region of the ribosomal RNA gene cluster were carried out with two short-cycled (aecial/telial) European rusts on Asteraceae, Puccinia distincta causing the current pan-European epidemic on Bellis perennis, and P. lagenophorae causing a similar disease on Senecio spp., as well as the macrocyclic P. obscura which alternates between B. perennis (pycnial and aecial host) and Luzula spp. (main host). All three species formed a well-resolved cluster when compared with the ITS sequences of a range of other rust fungi, using both parsimony and distance methods. The sequences of P. distincta and P. lagenophorae differed from each other at three positions whereas P. obscura differed from P. distincta at 37 points. Together with consistent morphological and epidemiological differences across Europe, these data support the recognition of P. distincta as a separate species from P. lagenophorae. Both may be derived from P. obscura, although the precise evolutionary history remains obscure.

Seventy-one strains of fungi belonging to 53 species of Zygomycota and mitosporic fungi were isolated from soils containing different levels of 2,4,6-trinitrotoluene (TNT). Three moderately contaminated samples (500 ppm) and an uncontaminated control contained a rich diversity of species whereas few fungi were isolated from a heavily contaminated sample (1000 ppm). Most isolates were capable of biotransforming TNT into aminodinitrotoluenes and azoxy-dimers, although they differed widely in their tolerance of TNT. Spore germination was generally more strongly inhibited by TNT than hyphal growth. Among the Zygomycota, Absidia and Cunninghamella were highly TNT-tolerant and attacked the substrate even when this had precipitated at 1000 ppm, whereas 12 of the 14 Mortierella isolates were intolerant of TNT above 50 ppm. Among the mitosporic fungi, Acremonium, Cylindrocarpon, Gliocladium and Trichoderma but not Penicillium species were highly tolerant of TNT and had a high capacity to biotransform this compound. Large variations in these properties were determined between species and even strains belonging to the same species, and between different isolates from the same soil sample. Populations of soil microfungi therefore show a high natural variation of TNT tolerance and biotransformation ability, irrespective of any previous long-term exposure to this xenobiotic.

An in vitro screen of 83 isolates of coprophilous fungi revealed that many of them were capable of stimulating growth of Sphaeronaemella fimicola at a distance. When in direct contact with S. fimicola, many (excluding the Zygomycotina) also stimulated the production of perithecia. Species of Coniochaeta, Ryparobius, Thelebolus and Trichobolus were the strongest inducers. These and related genera were also associated with perithecia of S. fimicola on dung collected from the field. Hyphae of many of the strong perithecium inducers and a few non-inducing species were parasitized by necrotrophic intrahyphal growth of S. fimicola. Perithecium formation was stimulated even when parasitism was prevented by separation of growing mycelia of Ryparobius pachyascus and S. fimicola by Cellophane. In contrast, prior growth and removal of R. pachyascus followed by inoculation with S. fimicola caused enhanced growth and asexual reproduction without concomitant perithecium formation.

Three British rust fungi reported to form aecia on daisy (Bellis perennis) are compared. A recently discovered species, possibly introduced from Australia, is identified as Puccinia distincta. It is a short-cycled -opsis form lacking uredinia, with aecia and telia confined to Bellis and its aeciospores capable of reinfecting the same host. This rust is compared with a macrocyclic heteroecious eu-form, P. obscura, which produces pycnia and aecia on Bellis and uredinia and telia on Luzula. Puccinia distincta is probably derived from and correlated with P. obscura because both species have the same aecial host, and because their teliospores are closely similar in morphology and dimensions. Comparison is extended to P. lagenophorae, a common rust with aecia and telia on Senecio spp., which has been reported to form aecia on Bellis following inoculation with aeciospores from Senecio. The repeated failure of our own reciprocal inoculation experiments using aeciospores from the two different hosts and differences in teliospore morphology between P. distincta and P. lagenophorae lead us to conclude that the current rust epidemic on daisies is caused by P. distincta which is distinct from P. lagenophorae.

The two forms of acid phosphatase secreted by Botrytis cinerea were purified, characterized and found to possess fundamentally different properties. The phosphate-repressible acid phosphatase was a monomer of clearly defined molecular weight (55–56 kDa), with a polypeptide component of 43 kDa. The enzyme was secreted through the hyphal apex and accumulated in the culture fluid. Its high affinity for a wide range of substrates rendered it suitable for a putative role as an extracellular phosphate-scavenging enzyme. Secretion of a constitutive acid phosphatase occurred at low levels in phosphate-enriched culture; at phosphate starvation, the activity of this enzyme was enhanced ten-fold in the culture fluid and two-fold in the cell wall. The constitutive enzyme had strikingly different properties from those of the repressible form. It consisted of a 93 kDa polypeptide which was heavily glycosylated such that the secreted protein displayed size heterogeneity of 140–200 kDa by SDS–polyacrylamide gel electrophoresis and 320–450 kDa by native Sephacryl S-300 chromatography. Irrespective of the phosphate status, most of the secreted constitutive enzyme activity was retained by the cell wall. These results were consistent with ultrastructural histochemical observations which suggested that this enzyme form was secreted by a novel pathway via the fusion of vacuoles with the plasma membrane in mature hyphal segments.

Botrytis cinerea secreted low levels of a constitutive acid phosphatase into liquid culture when grown in the condition of phosphate starvation or in the presence of high concentrations (4 mM) of organic phosphate esters or inorganic phosphate. During phosphate starvation the overall acid phosphatase activity secreted into the culture fluid was increased up to 80-fold due to the appearance of a second (phosphate-repressible) enzyme form. On native polyacrylamide electrophoresis gels, the constitutive enzyme displayed size heterogeneity, whereas the repressible enzyme was resolved as a discrete band. Both forms of the enzyme reacted with p-nitrophenylphosphate under such conditions, but only the constitutive form was found to hydrolyse β-glycerophosphate. Histochemical staining with these two substrates with the Gomori lead-capture method revealed significant staining of secretory vesicles in the hyphal tip region only in phosphate-starved mycelium with p-nitrophenylphosphate as the substrate. By contrast, vacuolar structures were stained with both substrates under conditions of phosphate starvation as well as abundance of inorganic phosphate. The implications of these observations for the likely exit route of the two acid phosphatase forms are discussed.