Rhynchosporium secalis isolates E97-2 and H97-2, represented the major pathotypes in populations on barley in Alberta, Canada, but differed widely in their virulence. Following greenhouse co-inoculation with the two pathotypes, E97-2, originally isolated from resistant cv. ‘CDC Earl’, predominated over H97-2, isolated from the susceptible cv. ‘Harrington’, from the first to the last of four infection cycles on both ‘CDC Earl’ and ‘Harrington’. These results indicated that the host can rapidly influence pathotype composition and that pathotype E97-2 may have a competitive advantage over H97-2 on these cultivars. DNA polymorphisms were found between isolates from single or mixed inoculations on cvs ‘CDC Earl’ and ‘Harrington’ for four successive cycles. Co-inoculation with the two isolates resulted in a shift to a molecular phenotype more similar to E97-2 than H97-2. The competitive advantage of E97-2 over H97-2, combined with the selective pressure exerted by the host, would explain the increased susceptibility of cv. ‘CDC Earl’ and other cultivars with similar sources of scald resistance, in fields across Alberta. However, H97-2 will likely remain one of the major pathotypes in Alberta due to the relatively large acreage of cv. ‘Harrington’ in this province.

Perenniporiella gen. nov. is segregated from Perenniporia. The new combinations Perenniporiella neofulva and Perenniporiella micropora, and the new species Perenniporiella pendula are proposed. Perenniporia piperis and Perenniporia albida are considered as taxonomic synonyms of P. neofulva. The three species are described and their taxonomic position is discussed. A key to the neotropical Perenniporiella and Perenniporia species with pileate basidiomes is presented.

The first action spectrum for a photo-induced response of an arbuscular mycorrhizal fungus is reported. At low light intensity, the responsive wavelengths for light-induced hyphal branching of the primary germ tube of Gigaspora gigantea were determined to be in the blue to UV-A range. The action spectrum showed the greatest stimulation of branching occurred around 390 nm although a shoulder was observed between 360–370 nm. A second major peak of light-induced branching occurred at 430 nm. The exposure of specific areas of the germ tube to high intensity blue light for a short period led to several interesting observations. By exposing 2 mm segments (0–2, 2–4, 4–6, etc.) or 3 mm segments away from the tip, it was determined that photoinduction of hyphal branches could occur anywhere along the axis of a growing germ tube except in the apical 2 mm. When 3 mm segments were exposed at greater distances from the tip (6–9, 9–12, and up to 33–36 mm), branches frequently formed in areas not directly exposed to light. The branches were usually in clusters which were spaced approximately 3 or 6 mm apart. Since light scattering could be ruled out, these results indicated that the exposure sites and sites of hyphal branching did not necessarily coincide and suggested the probable involvement of a second messenger during this blue light-induced event.

Several species of Mortierella (Mortierellales, Zygomycota) were examined for substances regulating their sexual reactions. Compounds isolated from both mated and single growing Mortierella strains were purified by thin layer chromatography. Some of these compounds showed UV absorbance-characteristics similar to those of trisporoids, a group of compounds involved in sexual regulation in Mucorales. A compound with a 4-dihydromethyltrisporate-like absorbance spectrum was detected. To test for the interspecific sexual responses typically induced by trisporoids, the compounds extracted from Mortierella spp. were tested against the Mucorales Mucor mucedo and Phycomyces blakesleeanus and were found to induce sexual reactions in both tester strains. A gene encoding 4-dihydromethyltrisporate dehydrogenase was identified in several Mortierella species and the activity of the gene product was shown using a histochemical assay. We suggest that the regulation of sexual processes by trisporoids is common to both Mucorales and Mortierellales and may be more widespread within the Zygomycota.

Mycoparasites collected from aerial parts of the cocoa plant (Theobroma cacao) have shown great promise in the control of black pod, caused by Phytophthora palmivora, and moniliasis, caused by Moniliophthora roreri. However, the ecology of epiphytic mycoparasites is still poorly understood although it has a direct bearing on applied biocontrol practices, ranging from the identification and isolation of promising biocontrol candidates to formulation needs and required application frequency. One objective of this study was to determine the natural abundance of mycoparasites on cocoa flowers and pods in relation to crop development stage and cultivar. For this purpose, native mycoparasites were detected on cocoa flowers and pods using the precolonised plate baiting technique. Furthermore, the survival of an applied Clonostachys rosea isolate on cocoa pods on shaded and non-shaded trees was compared as well as the recolonisation patterns of surface-sterilised pods by native mycoparasites under these conditions. Clonostachys spp. were the most commonly isolated native mycoparasites, followed by Fusarium spp. No differences in the occurrence of native, epiphytic mycoparasites were observed between the three main cocoa cultivars, ‘Criollo’, ‘Forastero’ and ‘Trinitario’, nor between clones within these groups. Thus, a single biocontrol inoculum can be suitable for application to cultivar mixtures of cocoa commonly grown together in a field. Different susceptibility classes of segregating F1 populations of hybrids with resistance against M. roreri and P. palmivora supported similar population levels and taxonomic assemblages of mycoparasites. Therefore, we reject the hypothesis that these antagonists mediate resistance. Mycoparasite abundance and genetic disease resistance to black pod and moniliasis are independent phenomena and should lead to additive effects if employed simultaneously in an integrated disease management programme. The survival of applied C. rosea was not affected by the shading regime or any other meteorological parameter measured. On the other hand, recolonisation of surface-sterilised cocoa pods by most native mycoparasites was faster in the shade. Only Trichoderma spp. colonised pods exposed to direct sunlight faster than shaded ones. The implications for the design of biocontrol inocula and formulation technology are discussed.

Host specificity of the mycoparasite Hypomyces microspermus to the Xerocomus chrysenteron group has been observed, but primarily from European collections. Our objectives were to test host specificity among Hypomyces spp. associated with boletes in California oak-woodlands, investigate population biology of these parasites, and to initiate studies on host-parasite coevolution. Bolete samples were collected from four locations separated by up to 600 km. Hypomyces isolates were cultured and host tissue samples taken for molecular identification. Based on AFLP analysis, four distinct Hypomyces clades were found with little genotypic diversity within each group. ITS-rDNA regions of selected isolates from each group were sequenced and analyzed along with sequences from a previously published phylogeny. Isolates from two AFLP groups clustered with H. microspermus whereas isolates from the other two AFLP groups clustered with H. chrysospermus. ITS-RFLP followed by sequence analysis identified three bolete hosts: (1) X. dryophilus; (2) a Xerocomus species closely related to X. dryophilus with affinities to X. chrysenteron; and (3) a Xerocomus species related to the X. subtomentosus group, which is not closely related to X. dryophilus and X. chrysenteron. H. microspermus infected X. dryophilus and the species with affinities to X. chrysenteron, whereas H. chrysospermus infected the species with affinities to X. chrysenteron and the species related to the X. subtomentosus group. These results support previous observations that H. microspermus is host-specific to the X. chrysenteron group, and that H. chrysospermus is more of a generalist pathogen. We also conclude that host-parasite coevolution studies within this system will not be possible until a phylogeny of North American boletes is in place.

Helicobasidium mompa is a clampless basidiomycete and binucleate both in secondary and primary hyphae. Single basidiospore isolates were paired in sibling and non-sibling combinations. We did not observe any alterations in colony morphology, such as tuft formation, but mycelial incompatibility, as indicated by the presence of a dark demarcation line between colonies, occurred in a unifactorial manner. Techniques using DNA molecular markers, such as internal transcribed spacer-restriction fragment-length polymorphism (ITS-RFLP), inter–simple-sequence-repeat polymerase chain reaction (PCR), and universally primed PCR, failed to identify nuclear migration to opposite single basidiospore isolates in all but one of the 92 pairings. These results imply that single basidiospore isolates of H. mompa may be incompetent to mate under laboratory conditions and that a single mycelial incompatibility factor operates in single basidiospore isolates.

A Phytophthora pathogen of trees and shrubs previously designated Phytophthora sp. O-group is formally named as P. inundata sp. nov. P. inundata falls within the P. gonapodyides-P. megasperma major ITS Clade 6, its present nearest known relative being P. humicola. It has non-papillate sporangia, fairly large oogonia (average ca 40 μm) with thick walled oospores, amphigynous antheridia, a distinctive colony type, a high optimum temperature for growth of 28–30°C, fast growth at the optimum, and a high upper temperature limit for growth of ca 35–37°. A study of the breeding system of eight P. inundata isolates showed them to be classically heterothallic with A1 and A2 compatibility types. However some P. inundata A1×A2 combinations failed to mate even though the same isolates mated successfully with P. drechsleri testers. Others were ‘silent’ A1s or A2s, unable to produce their own gametangia but able to induce gametangial formation in the opposite sexual compatibility type of another species. This indicates a partial breakdown of the sexual mechanism in the species. Two isolates (one A1 and one A2) were unpredictably and chimaerically self-fertile, suggesting A1+A2 chromosomal heteroploidy. The association of P. inundata with ponds and rivers and with root and collar rots of trees and shrubs after flooding is discussed.

In the paper by M. Morretti, A. Arnoldi, A. D'Agostina, G. Farina & F. Gozzo on the ‘Characterization of field isolates and derived DMI-resistant strains of Cercospora beticola’, in Fig. 2 there is an error in the formula of 14α-methyl-3,6-diol: an -OH group was omitted in the C6 position.

Forty-two dikaryotic and 42 monokaryotic isolates, and 34 pairings were examined by horizontal polyacrylamide gel electrophoresis (PAGE) for six enzymatic activities, viz. EST, 6PGD, IDH, MDH, SHDH and SOD. 44 bands were analysed. Numerical analysis of the isoenzymatic patterns was undertaken and compared with those from morphological characters. The analysis of six enzymatic systems showed the existence of four monomorphic systems (IDH, MDH, SHDH and SOD). The sterease system (EST) appears to be polymorphic in Polyporus ciliatus and in populations of P. tenuiculus from Argentina, being monomorphic in the remaining species studied. The 6PGD system is polymorphic in P. tucumanensis and monomorphic in the other species. Predominance of monomorphic enzymes and a clear distribution of the electromorphs among the species, indicates that isoenzymatic analysis is a good taxonomic tool within Polyporus. The low intraspecific variability allowed the use of interspecific differences to separate species. Numerical analysis showed a good correlation between morphological and molecular characters. In the isoenzymatic phenogram the similarity index is high only among very close species, showing a stressed separation of species.

Spontaneously-occurring hypovirulence in the tan sclerotial isolate S10 of Sclerotinia sclerotiorum from sunflower in Canada was characterized and compared to another hypovirulent isolate Ep-1PN of S. sclerotiorum from eggplant in China. Hypovirulent isolates derived from S10 were purified by single hyphal tip isolations from colonies of S10 showing abnormal growth on potato dextrose agar (PDA) and tested for pathogenicity on leaves of canola (Brassica napus cv. ‘Westar’). These abnormal isolates differed from the virulent isolate wtS10 derived from a normal colony of S10 by the reduced hyphal growth, induced production of abnormal hyphal branches, enhanced production of brown pigments, reduced sclerotial formation on PDA, reduced oxalic acid accumulation in potato dextrose broth, and reduced pathogenicity on canola. Vegetative transfers revealed that the hypovirulence phenotype of the hypovirulent isolate S10-2A-11 was stable. This preliminary in vitro transmission test indicated that the hypovirulence in the isolate S10-2A-11 was transmissible but at a lower rate than that of the hypovirulent isolate Ep-1PN. Double-stranded ribonucleic acids (dsRNAs) were detected in isolate Ep-1PN, but not in hypovirulent and virulent isolates derived from S10. The existence of dsRNA-free hypovirulence in S10 progenies suggests that another hypovirulence mechanism may exist in S. sclerotiorum.

A study of saprobic fungi occurring on the fynbos of the Western Cape Province of South Africa yielded four unknown Anthostomella species. A. proteae from Protea nitida, A. cynaroides from P. cynaroides, A. leucospermi from Leucospermum oleifolium, and A. brabeji from Brabejum stellatifolium are described as new. New records for South Africa include A. conorum from Leucadendron sp., Protea magnifica and P. neriifolia, and A. clypeata from Ischyrolepis subverticellata, Cannomois Virgata, Restio egregius, and R. cfr confusus. A dichotomous key to the Anthostomella species in South Africa is also provided.

Tropical xylariaceous taxa in the genera Biscognauxia, Hypoxylon and Xylaria were evaluated for their ability to produce wood-decay enzymes and effect mass loss and lignin solubilization in angiosperm and gymnosperm wood. All xylariaceous taxa were capable of cellulose and xylan hydrolysis, but few produced enzymes involved in lignin breakdown. Xylariaceous fungi were incapable of causing mass loss in gymnosperm wood, but several caused significant mass loss in angiosperm wood during a six month in vitro exposure. Mass loss values obtained were low at approx. 20% of those obtained for basidiomycetes. Lignin was solubilized at similar rates to mass loss by Hypoxylon and Xylaria species, resulting in indices of lignin solubilization between 0.88 and 1.11, which were similar to those obtained for white-rot basidiomycetes and higher than those previously reported for any other xylariaceous fungi.

Cheiromycina globosa and C. ananas spp. nov. are described in the lichenized hyphomycete genus Cheiromycina, one from Germany and one from the USA. A key is provided to all four species now known in genus, and all other lichenized hyphomycetes are briefly mentioned. All are corticolous and rarely recorded, so far only from temperate regions in Europe and North America.

Colletotrichum lagenarium is a plant pathogenic fungus, and produces melanin that is an essential factor for appressorial penetration into host tissues. The melanin biosynthesis pathway of C. lagenarium starts with pentaketide synthesis catalyzed by polyketide synthase Pks1p. We previously confirmed that the direct product of Pks1p is 1,3,6,8-tetrahydroxynaphthalene. Thus, melanin biosynthesis in this fungus requires the reduction of 1,3,6,8-tetrahydroxynaphthalene to scytalone. We made a double mutant 9141-144 from the thr1 mutant 9141 that lacks the ability to metabolize 1,3,8-trihydroxynaphthalene. The double mutant 9141-144 could metabolize neither 1,3,6,8-tetrahydroxynaphthalene nor 1,3,8-trihydroxynaphthalene. However melanin production by the double mutant was restored by THR1, indicating that Thr1p can metabolize both compounds in vivo. These results demonstrate that two enzymes, Thr1p and a deduced 1,3,6,8-tetrahydroxynaphthalene-specific reductase, are involved in the first reduction step of the melanin biosynthesis pathway of C. lagenarium.

Relative quantitative RT-PCR and western blotting were used to investigate the expression of three genes with potentially regulatory functions from the arbuscular mycorrhizal fungus Glomus intraradices in symbiosis with tomato and barley. Standardisation of total RNA per sample and determination of different ratios of plant and fungal RNA in roots as colonisation proceeded were achieved by relative quantitative RT-PCR using universal (NS1/NS21) and organism-specific rRNA primers. In addition, generic primers were designed for amplification of plant or fungal β-tubulin genes and for plant glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes as these have been suggested as useful controls in symbiotic systems. The fungal genes Ginmyc1 and Ginhb1 were expressed only in the external mycelium and not in colonised roots at both mRNA and protein levels, with the proteins detected almost exclusively in the insoluble fractions. In contrast, mRNA of Ginmyc2 was identified in both external and intraradical mycelium. In mycorrhizal roots, Ginmyc2 and fungal β-tubulin mRNAs increased in proportion to fungal rRNA as colonisation proceeded, suggesting that accumulation reflected intraradical fungal growth. Fungal α-tubulin protein and β-tubulin mRNA both appeared to be more abundantly accumulated in AM hyphae within heavily colonised roots than in external hyphae, relative to fungal rRNA. Tomato GAPDH mRNA accumulation was proportional to tomato rRNA, but accumulation of tomato β-tubulin mRNA was reduced in colonised roots compared to non-mycorrhizal roots. These results provide novel evidence of differential spatial and temporal regulation of AM fungal genes, indicate that the expression of tubulin genes of both plant and fungus may be regulated during colonisation and validate the use of multiple ‘control’ genes in analysis of mycorrhizal gene expression.

Fungal species richness and abundance were assessed in leaf litter of the Australian rainforest tree Neolitsea dealbata (Lauraceae) using particle filtration. Results were comparable to the species richness and abundance reported in previous studies of tropical leaf litter microfungi. Eight leaf samples yielded 1365 strains. In an assessment of the effect of surface treatments, 736 strains in 112 morphotaxa were isolated, while 639 strains in 141 morphotaxa were recovered to assess the effect of surface treatment. Isolation rates in airdried leaves stored at room temperature for four weeks declined linearly, while the number of morphotaxa remained essentially constant for the first three weeks. Isolates of common morphotaxa were lost preferentially over those of rarer taxa. Such losses of isolates may be acceptable if only presence/absence data are collected. If frequency data are vital for community analysis, only fresh material should be utilised. Two surface sterilisation treatments were applied to N. dealbata leaves. An ethanol/sodium hypochlorite treatment was considered unsuitable because it significantly reduced the number of morphotaxa derived from the leaf lamina. A sodium hypochlorite treatment reduced the number of detectable propagules in the wash water without changing the number of morphotaxa derived from leaf particles in comparison with those of the control group.

Three new Cortinarius species, Cortinarius conopileus, C. keralensis, and C. phlegmophorus spp. nov., are described from Kerala State in southern India. This is the first record of ectomycorrhizal Cortinarius spp. in the tropical part of India. In addition to distinct morphological characters, the comparative analysis of rDNA ITS sequences of the collections from India and morphologically similar species support the recognition of these taxa as new species. Phylogenetic analyses demonstrate that the three Indian Cortinarius spp. belong to both larger subclades of the genus Cortinarius, clade/cortinarius and clade/telamonia. As supported by morphological and molecular data, C. phlegmophorus belongs to Cortinarius subgen. Myxacium sect. Defibulati. Based on classical morphological characters, both C. keralensis and C. conopileus are representatives of subgen. Telamonia. However, C. conopileus belongs to clade/obtusi, which is a well-supported subclade of clade/cortinarius. Thus, in contrast to classical taxonomy, the clade/obtusi represents an independent evolutionary origin of telamonioid taxa. This result is also reflected by the distinct morphological characters of taxa of clade/obtusi, namely the lamellar trama with ellipsoid inflated hyphae and the presence of cystidia. In contrast, C. keralensis is a typical member of clade/telamonia. Within/telamonia, only relationships of closely related taxa are resolved due to the low genetic divergence found in ITS sequences. Based on morphological and molecular criteria, C. keralensis is a distinct taxon of sect. Saturnini.

Lewia avenicola sp. nov. (anamorph Alternaria sp.) is described. The fungus was isolated from oat grain in Norway. The fungus produced conidia within a month, and ascomata with fully mature ascospores within 8 months following inoculation, when stored on slants of synthetic nutrient agar (SNA) at 4 °C in darkness. A comparison with other known Lewia species is made, and a key to the five known Lewia species is included.