Superficial Hyphae Research Articles

Fungal Hyphae on the Assimilation Branches Are Beneficial for Haloxylon ammodendron to Absorb Atmospheric Water Vapor: Adapting to an Extreme Drought Environment.

Research on endophytic fungi in desert plants, particularly the epiphytic or endophytic fungi of leaves, remains limited. In the extremely arid regions of northwest China, the ultra-xerophytic desert plant Haloxylon ammodendron harbors white fungi on its assimilating branches during autumn. The hyphae of these fungi intertwine, both internally and externally, comprising superficial, bridging, and endophytic types. The superficial hyphae attach to the surface of the assimilating branches and continuously grow and intersect, forming a thick layer of felt-like hyphae. This thick, felt-like layer of hyphae facilitates the adsorption of atmospheric water vapor on the surface of the hyphae or the assimilating branches, allowing H. ammodendron to capture atmospheric moisture, even under low humidity. Some superficial hyphae penetrate the cuticle into the epidermis, becoming bridging hyphae, which can rapidly transport water from the outside of the epidermis to the inside. The endophytic hyphae shuttle within the epidermis, achieving rapid water transfer within the epidermis of the assimilating branches. The presence of these three types of hyphae not only enables the assimilating branches of H. ammodendron to achieve rapid water absorption and transmission, but also facilitates the uptake of atmospheric water vapor under low humidity conditions. We discuss the mechanism by which the hyphae promote water absorption from the perspectives of hyphal composition, the formation of felt-like structures, and environmental conditions. We consider the presence of fungal hyphae on the surface of the H. ammodendron assimilating branches as an inevitable ecological process in arid environments. This study provides important theoretical insights into the mechanisms underlying the strong drought resistance of desert plants in extremely arid regions and offers strategies for desertification control.

First Report of Powdery Mildew Caused by Podosphaera xanthii on Benincasa hispida in Korea.

Benincasa hispida (Thunb.) Cogn. (syn. B. cerifera Savi, Cucurbita hispida Thunb.), called wax gourd or ash gourd, is a cucurbitaceous vine grown for medicinal purposes and commercial values of its large fruits in Southeast Asia (Al-Snafi 2013). During the summer and autumn of 2020, leaves of wax gourd were observed to be affected by powdery mildew with 100% disease incidence in an experimental plot of Jeonbuk National University (35°50'55″N, 127°07'48″E), Korea. Fungal colonies were initially circular to irregular, forming white patches on both sides of the leaves and young stems, finally covering entire leaves and causing premature senescence of the leaves and poor growth. A representative voucher specimen was deposited in the Korea University herbarium (KUS-F32171). At least 30 measurements were taken for each asexual diagnostic features. Conidiophores arising from superficial hyphae were straight, 100 to 210 μm long, and produced 3 to 7 immature conidia in chains with a crenate outline. Foot-cells were cylindrical, 46 to 74 ×10 to 12 μm, followed by 1 to 2 shorter cells. Conidia were ellipsoid-ovoid to barrel-shaped, 30 to 40 × 18 to 23 μm with a length/width ratio of 1.4 to 2.0 and contained conspicuous fibrosin bodies. Germ tubes were produced from a lateral position on conidia. Sexual stage was not observed during the growing season. The morphological characteristics of the fungus were compatible with those of Podosphaera xanthii (Castagne) U. Braun & Shishkoff (Braun and Cook 2012), a well-known cucurbitaceous powdery mildew. DNA was extracted from mycelium, and primer sets ITS1F/PM6 and PM3/TW14 were used for amplification of ITS1-5.8S-ITS2 regions and 5´-end of 28S rDNA gene, respectively (Takamatsu and Kano 2001). Sequences determined in this study were deposited to the GenBank under the accession numbers MW559231 and MW559420, respectively. The sequences for ITS regions and 28S rDNA gene showed 99.78% and 99.07% similarity respectively with those of P. xanthii (MH465242, MH465243, MT250855 for ITS, and MK357436, MT826247 for LSU). Pathogenicity was confirmed twice by pressing a diseased leaf onto young leaves of five wax gourd plants. Five non-inoculated plants were used as controls. Inoculated leaves developed symptoms after 5 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Sphaerotheca fuliginea (syn. P. xanthii) on B. hispida has been listed in Hungary, India, Japan, Singapore, and Taiwan so far (Farr and Rossman 2021). Recently, the identity of P. xanthii on B. hispida in Taiwan was confirmed with morphological examination and molecular analysis by Wu and Kirschner (2017). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on B. hispida in Korea. Since wax gourd production is only recently started on a commercial scale in the southern part of Korea, powdery mildew infections pose a serious threat to the safe production of the fruits, especially in organic farming where chemical control options are limited.

First Report of Podosphaera xanthii Causing Powdery Mildew on Mungbean (Vigna radiata) in Taiwan.

Mungbean (Vigna radiata L.) is routinely grown in the experimental fields at the headquarters of the World Vegetable Center (23°6'30.88"N, 120°17'51.31"E) for breeding, research and germplasm multiplication. In a spring 2016 mungbean trial, about 50% of the plants were affected with powdery mildew. The white, powdery-like patches first appeared on the upper leaf surfaces, and soon developed to grey patches on both sides of the leaves. Purple to brown discoloration appeared on the underside of the infected leaf. Microscopy examination revealed that the causal organism was not Erysiphe polygoni, which had previously been documented as the powdery mildew pathogen on mungbean in Taiwan (Hartman et al. 1993). The fungus produced typical structures of the powdery mildew Euoidium, anamorph of the genus Podosphaera. The mycelium consisted of septate, flexuous hyphae with indistinct appressoria. The erect conidiophores arising from superficial hyphae varied from straight or slightly curved to curled. Three to ten conidia were borne in long chains with crenate edges. Foot-cells were straight, cylindrical and measured 30 to 52 µm long. Conidia were hyaline, ellipsoid-ovoid to barrel-shaped, with fibrosin bodies, and measured 27 to 33 (mean = 30.4) × 15 to 20 (mean = 16.6) µm. Germ tubes were clavate and occasionally forked, and were produced from the lateral sites of the conidia. No chasmothecia were found in the samples. The morphological characteristics were consistent with P. xanthii (Castagne) U. Braun & Shishkoff (Braun & Cook 2012). To confirm the identity, the internal transcribed spacer (ITS) region of rDNA and partialβ-tubulin gene (TUB2) for the isolate MG3 were amplified with the primers ITS4/ITS5 (White et al. 1990) and BtuF5/BtuR7a (Ellingham et al. 2019), respectively. BLASTn analysis revealed the ITS sequence (MN833717) was 100% identical to many records of P. xanthii whereas the TUB2 sequence (MW363957) was 100% identical to a record of P. fusca (syn. P. xanthii; KC333362) in NCBI GenBank. A pathogenicity test was conducted by dusting conidia from an infected leaf onto six healthy four-week-old mungbean plants (cv 'Tainan No. 3'). Another three plants were not inoculated and were used as control. All the plants were maintained in a greenhouse at 25 to 28°C. All inoculated plants developed powdery mildew symptoms after 10 days, whereas the control plants remained symptomless. To our knowledge, this is the first report of P. xanthii causing disease on mungbean in Taiwan. P. xanthii also has been reported on mungbean in Thailand (Meeboon et al. 2016), while other records referring to E. polygoni infecting Vigna spp. are from Brazil and Fiji (Farr & Rossman 2020). Although both P. xanthii and E. polygoni have now been reported as causing powdery mildew on mungbean in Taiwan, which species predominates or is more important remains unclear. A comprehensive survey with accurate species identification is required to develop effective management of the disease, particularly for resistance breeding.

First Report of Lotus Powdery Mildew Caused by Erysiphe takamatsui in China

Lotus (Nelumbo nucifera Gaertn.) is an aquatic perennial plant of the family Nelumbonaceae, distributed in subtropical and temperate regions, also extensively planted as an ornamental flower. Furthermore, the rhizome is used as a vegetable and the roots and seeds in herbal medicine in China. In September 2018, some lotus leaves were found to be infected with a powdery mildew in a pond in Qingdao, Shandong Province, China. In the surveyed pond, from late September to mid-November, the disease incidence varied from 10 to 70%, and some leaves were almost completely covered with powdery mildew and turned brown and scorched. In several lotus ponds not far away from the surveyed one, a few powdery mildew–affected leaves were also found. Small colonies of powdery mildew were dispersed on the upper sides of the leaves, and the adjacent colonies coalesced over several days. Some chasmothecia were formed on the lesions in the middle of November. The voucher specimens are deposited in the Qingdao Agricultural University Herbarium (HMQAUPM18001). Superficial hyphae were hyaline, branched, and septate, 4.5 to 6.0 μm wide, with thin and smooth walls. Hyphal appressoria were 4.7 to 6.7 μm diameter, nipple shaped to lobed, mostly single, rarely in opposite pairs. Conidiophores were straight, 74.3 to 98.5 × 7.8 to 9.8 μm, and composed of three to four cells; foot cells were cylindrical, usually straight, occasionally somewhat curved to sinuous, 38.2 to 57.5 × 6.9 to 8.5 μm. Conidia were formed singly, ellipsoid-ovoid, subcylindrical to almost cylindrical, 35.2 to 41.2 × 17.2 to 19.2 μm, and showed a wrinkling pattern of the outer walls. Germ tubes were produced in perihilar position. Chasmothecia were scattered to gregarious, 102.2 to 129.8 μm in diameter; peridium cells were irregularly polygonal, 13.0 to 19.1 μm in diameter; appendages arising from the lower half were mycelioid, unbranched or occasionally with short lateral branchlets, 0.5 to 4 times as long as the chasmothecial diameter, brown at the base and becoming paler toward the apex. Asci were ellipsoid to obovoid, short-stalked, 62.0 to 70.9 × 39.8 to 46.4 μm, wall 1.9 to 2.9 μm thick, two- to eight-spored. Ascospores were ellipsoidal, 23.5 to 27.6 × 13.8 to 15.6 μm, colorless. The morphological characteristics were consistent with previous records of Erysiphe takamatsui (Braun and Cook 2012; Meeboon and Takamatsu 2015). To confirm the identification based on morphological traits, a molecular examination of the isolate HMQAUPM18001 was confirmed by sequence analyses of the rDNA spanning ITS1, 5.8S gene, ITS2 and the 28S rRNA gene using the primers ITS1/ITS4 (White et al. 1990) and NL1/NLP2 (Hirose et al. 2005; Mori et al. 2000), respectively. ITS and 28S sequences of HMQAUPM18001 have been deposited in GenBank under the accession numbers MK478870 and MK583929, respectively. BLAST analysis of the ITS (641 bp) and 28S (720 bp) segments both showed 100% homology with the ITS sequence of E. takamatsui strain TNS: F-52102 (GenBank accession no. AB916688) and 28S sequence of E. takamatsui strain MUMH 5399 (GenBank accession no. AB916690), respectively. Pathogenicity was confirmed through inoculation tests by pressing a diseased leaf onto young leaves of three healthy lotus plants. Three noninoculated plants were used as controls. Inoculated plants developed symptoms after 8 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants, fulfilling Koch’s postulates. Therefore, the pathogen on lotus was confirmed to be E. takamatsui. To our knowledge, this is the first discovery of E. takamatsui, hitherto only known from Japan, on lotus in the Chinese mainland (Farr and Rossman 2019). This is the second discovery of the sexual stage of E. takamatsui in the world, which is important to note because it has substantial implications on pathogen survival and diversity. Because this lotus powdery mildew may cause losses of ornamental value, as well as the quality as foodstuff and for medicine purposes, control measures such as improving air and light conditions, removing heavily infected leaves, and preinfection applying of sulfur agents should be considered.

Leveillula buddlejae sp. nov., a new species with an asexual morph resembling phylogenetically basal Phyllactinia species

An asexual morph of a powdery mildew was found on Buddleja asiatica (Scrophulariaceae) in Nepal. The morphological traits of this powdery mildew strongly resemble those of Phyllactinia species (including Ovulariopsis) belonging to a phylogenetically basal group closely related to Leveillula species, but phylogenetic examinations and analyses clearly showed that this fungus pertains to Leveillula. Within the latter genus, it seems to be allied to L. duriaei, but clearly differs from this species in having conidiophores arising from superficial hyphae and narrower conidia with different length/width ratios. Therefore, the powdery mildew on B. asiatica is described as Leveillula buddlejae sp. nov.

Histopathological assessment of the infection of maize leaves by Fusarium graminearum, F. proliferatum, and F. verticillioides

Young maize plants were inoculated on unfolded mature leaves and on folded immature leaves with Fusarium graminearum, Fusarium proliferatum, and Fusarium verticillioides suspensions. Infection and symptom development of disease on these asymptomatic mature leaves and immature leaves were then documented. Subcuticular infection was found by the three Fusarium species on both symptomatic and symptomless leaves. The three Fusarium species penetrated the stomata of immature leaves by the formation of appressoria-like structures, infection cushions or by direct penetration. Infection by the three species of Fusarium via stomata is reported here for the first time. The superficial hyphae and re-emerging hyphae of the three species produced conidia. The macroconidia of F. graminearum produced secondary macroconidia and F. proliferatum formed microconidia inside the leaf tissues that sporulated through stomata and trichomes. The infection of maize leaves by the three species of Fusarium and their sporulation may contribute inoculum to cob and kernel infection.

Five new species of Inocybe (Agaricales) from tropical India

Five new species of Inocybe, I. iringolkavensis, I. keralensis, I. kuruvensis, I. muthangensis and I. wayanadensis, are described from Kerala state, India, based on morphological and molecular data. All are associated with trees belonging to Dipterocarpaceae. Inocybe iringolkavensis is characterized by nodulose to somewhat stellate basidiospores, 1–4-spored basidia, and caulocystidia restricted to the stipe apex. Inocybe keralensis has a yellowish brown pileus, lamellae with whitish, serrate edges, smooth, ellipsoidal basidiospores and a duplex pileipellis with the superficial hyphae devoid of encrustations and encrusted hyphae beneath. The diagnostic features of I. kuruvensis include a dark brown pileus, stipe with a whitish base and grayish brown, floccose-fibrillose surface, nodulose basidiospores with saddle-shaped projections and faintly encrusted paracystidia with refractive contents. Violet basidiomata with a rimose, hygrophanous pileus, densely pruinose stipe with a marginate-bulbous base, and nodulose basidiospores are the major features of I. muthangensis. Inocybe wayanadensis is characterized by small, whitish basidiomata, a viscid pileus with a rimulose surface, a densely pruinose and fibrillose stipe with a marginate-bulbous base, nodulose basidiospores, thick-walled pleuro- cheilo- and caulocystidia and an ixotrichoderm-type pileipellis. The phylogenetic relationships of these new species are inferred from an analysis of nuc rDNA sequences of the internal transcribed spacers (ITS1-5.8S-ITS2) and the 28S gene. Except I. keralensis, which belongs to the Pseudosperma clade, all other species belong to the Inocybe clade. This study represents the second report of an Inocybe species (I. muthangensis) that combines violet basidiomata with nodulose basidiospores.

A reappraisal of Microthyriaceaea

Asterinella, Cirsosiopsis, Phragmaspidium, Platypeltella, Trichopeltella, Trichopeltum and Trichothyrinula are poorly known ascomycete genera, presently included in the family Microthyriaceae. In this paper the type species of each of these genera were examined and the taxa are redescribed and illustrated with photomicrographs. The taxonomic placement of each genus and their familial position is discussed. Asterinella and Platypeltella has superficial, flattened thyriothecia and superficial hyphae with hyphopodia; the thyriothecia opens by splitting to release the ascospores and these genera should be placed in Asterinaceae. Cirsosiopsis, has strongly flattened, discoid or pulvinate to elongate, carbonaceous ascomata and is transferred to Parmulariaceae. Phragmaspidium has an upper wall comprising neatly arranged radiating cells; the basal layer is poorly developed and thus the genus should be retained in Microthyriaceae. Trichopeltella, Trichopeltum and Trichothyrinula are foliar epiphytes forming extremely thin, relatively large, brown to black, circular to irregular, or root-like, spreading thalli, which cover the thyriothecia and should be placed in Trichopeltinaceae.

Two New Hepaticolous Species of the GenusOctosporella(Pezizales)

Abstract: Dobbeler, P. 2011. Two new hepaticolous species of the genus Octosporella (Pezizales). — Herzogia 24: 357–365. The pezizalean genus Octosporella (Pyronemataceae, Ascomycetes) is characterized by having orange-coloured perithecia-like ascomata, thick, colourless, superficial hyphae with elaborate infection structures consisting of appressoria and intracellular haustoria, and biotrophic obligate parasitism of hepatics. Two species are described as new. Both occur on hosts not recorded before for bryophilous fungi. Octosporella epiphylla, with spherical ascospores, infects epiphyllous Lejeuneaceae (Ceratolejeunea sp.) in Costa Rica and French Guiana. Octosporella fortunata grows on terricolous Saccogyna viticulosa on the Canary Islands and forms ascomata hidden within the host mats. Octosporella currently comprises ten species.

Two new species ofLichenostigma(Lichenotheliaceae, lichenicolous Fungi) from Iran

Abstract Valadbeigi T. & Brackel W. von: Two new species of Lichenostigma (Lichenotheliaceae, lichenicolous fungi) from Iran. — Willdenowia 41: 191–195. — Online ISSN 1868-6397; © 2011 BGBM Berlin-Dahlem., doi:10.3372/wi.41.41122 (available via http://dx.doi.org/) Two species of Lichenostigma, both from Iran, are described as new to science: L. iranicum, growing on Lobothallia praeradiosa, is characterised by rounded to elongate ascomata, sparse hyphal strands, 6(-8)-spored asci and the almost complete absence of pigmentation in the lower ascomatal wall; L. verrucosum, growing on Pleopsidium gobiense, is distinguished by rounded to irregular ascomata with radiating superficial hyphae, verrucose brown ascospores and by the complete absence of pigmentation in the lower ascomatal wall.

Studies onMicrothyriaceae: Placement ofActinomyxa,Asteritea,Cirsosina,PolystomellinaandStegothyrium

Abstract Actinomyxa, Asteritea, Cirsosina, Polystomellina and Stegothyrium are genera presently included in Microthyriaceae. We have examined the generic types and consider that their characters differ from those of Microthyriaceae. In Actinomyxa ascoma dissolve as a slimy mass in water and ostioles are star-like, thus the genus would be better placed in Stictidaceae. Asteritea has flattened ascomata with a star-like opening and superficial mycelium with hyphopodia and is better placed in Asterinaceae. Cirsosina has superficial hyphae without hyphopodia and elongate ascomata opening by a longitudinal split and is better placed in Aulographaceae. In Polystomellina ascomata also open by a longitudinal slit and have superficial hyphae and is better placed in Asterinaceae. Stegothyrium is a very unusual genus as it has thick-walled asci that appear to be bitunicate, but there is a J+ apical ring which is indicative of unitunicate asci. We suggest that Stegothyrium is excluded from Microthyriaceae and placed i...

A new species of Zygophiala associated with the flyspeck complex on apple from China

Zygophiala qianensis is described as a new fungal species associated with the cuticle of apple fruit sampled from an orchard in Shaanxi Province, China. Conidiophores were separate, arising from superficial hyphae, erect, scattered, subcylindrical, irregularly flexuous, consisting of four parts: a hyaline supporting cell that gives rise to a smooth, dark brown stipe, terminating in a finely verruculose, medium brown apical cell that gives rise to (1–)2(–3) medium brown, finely verruculose, doliiform to ellipsoidal, polyblastic conidiogenous cells, with 1–2 prominent scars, apical and lateral, darkened, thickened. Conidia were solitary, fusiform to obclavate, hyaline, smooth and thick-walled, transversely (0–)1(–7)-septate, mostly 1–2-septate, prominently constricted at the septum; apex obtuse, base subtruncate, with a darkened, thickened hilum. Zygophiala qianensis is compared morphologically to other species of Zygophiala, and a phylogenetic analysis of their DNA sequence data is presented.

Morphological patterns of Aspergillus niger biofilms and pellets related to lignocellulolytic enzyme productivities

To study the morphological patterns of Aspergillus niger during biofilm formation on polyester cloth by using cryo-scanning electron microscopy related to lignocellulolytic enzyme productivity. Biofilm and pellet samples obtained from flask cultures were examined at -80 degrees C in a LEO PV scanning electron microscope. Spore adhesion depends on both its rough surface and adhesive substances that form a pad between spore and support. An extracellular matrix surrounding germ tubes and hyphae was also seen. Biofilm mycelia showed an orderly distribution forming surface and inner channels, while pellets showed highly intertwined superficial hyphae and a densely packed deep mycelium. Morphological differences between both types of culture correlated with differences in enzyme volumetric and specific productivities. Biofilm cultures produced higher filter paper cellulase, endoglucanase, beta-glucosidase and xylanase volumetric and specific productivities than submerged cultures. Fungal biofilms are morphologically efficient systems for enzyme production. Favourable physiological aspects are shared with solid state fermentation, but fungal biofilms present better possibilities for process control and scale-up. The results of this study support the importance of morphology in the productivity of fungal submerged processes, placing biofilms in a preferential category.

First report of Neoerysiphe galeopsidis on Acanthus spinosus in the UK

In 2005, powdery mildew severely infected Acanthus spinosus , ‘spiny bear’sbreech’, in the Royal Horticultural Society’s Garden, Wisley. Initially discrete white patches appeared, mainly on the under surfaces of young leaves. By October a dense woolly lawn of conidiophores, bearing very long, entangled chains of conidia, almost covered these surfaces, the upper surfaces becoming discoloured. Having conidia maturing in chains on a herbaceous dicotyledon, the pathogen could be one of three genera. Lobed or kidney-shaped rather than nipple-shaped appressoria on superficial hyphae ruled out Golovinomyces (syn. Erysiphe ) orontii , previously recorded on this host in Britain (Braun, 1995). This, and lack of fibrosin bodies, excluded Podosphaera (syn. Sphaerotheca ) and thus suggested Neoerysiphe ; this was confirmed by SEM images of conidia with structural striations, leading to longitudinal wrinkling typical of the Oidium subgen. Striatoidium anamorph (Cook et al ., 1997). Elliptical conidia 24–43 × 13–21·5 μ m and foot cells 24– 50 × 7·5–12 μ m, straight, cylindrical or often narrowed at the base, fitted Neoerysiphe (syn. Erysiphe ) galeopsidis (Braun, 1995). In the absence of chasmothecia, the ITS region was amplified using primer sets ITS5/p3 and ITS1/p3, and sequenced as described by Cook et al . (2006). The ITS sequence (GenBank DQ350136) was identical to that of N. galeopsidis ex. Catalpa spp. (Cook et al ., 2006) and also to an N. galeopsidis sequence in GenBank (accession no. AF011300; ex Stachys sp., Lamiaceae). Braun (1995) confined N. galeopsidis to the Lamiaceae, despite a doubtful record on Geraniaceae, but its host range is clearly broader. Liu et al . (2005) found its chasmothecia on Althaea rosea (Malvaceae) and Cook et al . (1997) reported Oidium spp. with striated conidia on Acanthus mollis (Acanthaceae) and Jaborosa integrifolia (Solanaceae), but without confirming their identity. Recently, Cook et al . (2006) confirmed N. galeopsidis on Catalpa spp. (Bignoniaceae). This is its first confirmed record on Acanthus .

First report of powdery mildew on potted plants of Calluna vulgaris in Scotland

(cv. Bonfire Brilliance) were collected from a localgrower and brought into an unheated net-sided poly-ethylene tunnel at the Scottish Agricultural College, Auchin-cruive. By mid-November, patches of white myceliumwere visible on leaves. After approximately 10–12 weeks,it had colonised whole plants causing extensive foliarbrowning followed by defoliation. A preliminary micro-scopic examination revealed superficial hyphae bearingconidia typical of a powdery mildew. In Europe

Fungi from Mauritius: three Astrocystis species from Pandanus

Astrocystis fimbriata, A. rarissima and A. cepiformis spp. nov. are described and illustrated from dead leaves of Pandanus. Their affinities with related taxa are discussed, especially with Astrocystis species on Palmae and with Rosellinia as interpreted in recent studies. One species has stromata which develop from a mat of superficial hyphae, which has not previously been reported for Astrocystis.

Infection of beech leaves (Fagus sylvatica) by the endophyte Discula umbrinella (teleomorph: Apiognomonia errabunda): low-temperature scanning electron microscopy studies

The sequence of events leading to infection by Discula umbrinella of leaves taken from axenically grown beech seedlings was studied at the ultrastructural level. On the host surface, even under optimal conditions and when contact with the host is established, only approximately 70% germination can be observed. In hanging drops containing malt extract, germination is only approximately 10%, suggesting that abundant nutrient supply alone is not enough to promote germination. Incubation of conidia in leaf extracts, on the other hand, results in the induction of germination even if no contact with an appropriate support is established. Between 16 and 24 h after infection four stages of germination can be observed on beech leaves: (i) ungerminated conidia; (ii) germinating conidia producing long superficial hyphae; (iii) conidia with distinct, appressorium-like swelling at the end of the germ tube; and (iv) germinated conidia with a halo around the tip of the germ tube. Transmission electron microscopy shows that subcuticular penetration into the host occurs at places where halos are seen. Apparently only germination with formation of appressorium-like structures and halos leads to successful penetration. Application of conidia to the abaxial side of the host leaf results in the formation of structures similar to those observed on the adaxial surface. Conidial germ tubes penetrate the cuticular layers of the outer edges of the guard cells, but direct penetration through the stomata was rarely observed. Appressorium or halo formation, observed only on the host surface and never on other substrates, suggests host-specific induction of penetrating structures. The mode of penetration observed for D. umbrinella bears some similarities with that described for some biotrophs and pathogens, suggesting affinities between endophytes and pathogens. Key words: beech anthracnose, electron microscopy, endophytes, latent pathogens, ultrastructure.

The haustorial interface in a resistant interaction of Erysiphe pisi with Pisum sativum

The interface between Erysiphe pisi and pea cv. JI 1049 was studied at the ultrastructural and cytochemical levels and compared with those in two susceptible cultivars. Haustorial efficiencies, as indexed by the length of mycelium associated with each haustorium, and growth rates on the resistant and one susceptible cultivar were also compared. The interaction in the resistant cultivar differed from those in the susceptible cultivars in the following ways: (i) there was no contact between the host plasmalemma and the A neckband region; (ii) papillae were contiguous with the surface of the neck and thus were probably formed before haustoria and (iii) there appeared to be less polysaccharide in the extrahaustorial membrane. The extrahaustorial membrane in the resistant cultivar lacked ATPase activity, whereas the rest of the host plasmamembrane had normal activity. Each haustorium supported a significantly greater total hyphal length in the resistant than in the susceptible cultivars. Growth rates of superficial hyphae were very similar on the susceptible and resistant cultivars but there was a delay in the onset on hyphal growth on the resistant cultivar which correlated with the previously reported delay in formation of the first haustorium. In contrast to hyphal growth rates, the rate of haustorium production was significantly less in the resistant cultivar. It is proposed that resistance in cv. JI 1049 operates at the stages prior to haustorium formation, similarly to that in some non-host and partial resistance systems. Once formed, however, the function of the haustorium seems to be unimpaired, despite the observed interfacial differences.

Présence de Typhula mycophaga sp. nov. sur Lycoperdon en Colombie-Britannique

Typhula mycophaga sp. nov., occurring on senescent basidiocarps of Lycoperdon pyriforme Pers. in British Columbia, is placed in the subgenus Microtyphula Berthier because of the morphology and the structure of its basidiocarps and its nongelatinized sclerotia which have a normal epidermoid structure. This species is distinguished by its habit, nonamyloid spores, nonclamped hyphae, and papillate superficial hyphae on the stipe.

Role of conidial fusion in infection by Botrytis cinerea on cucumber leaves.

Glucose or sucrose enhanced germination of conidia, formation of primary appressoria and elongation of superficial hyphae, but did not induce infection by Botrytis cinerea on cucumber leaves. By enhancing conidial concentration in glucose or sucrose solution, however, B. cinerea produced significant lesions. When the conidial concentration exceeded 1×107 conidia/ml in 5% glucose or 5% sucrose solution, inoculated conidia fused with each other and formed netted structures on cucumber leaves. Similar fusions were also reported in the process of infection by Fusarium nivale. Hyphae growing out from the netted structures were more vigorous than hyphae or germ tube from single conidia. The hyphae from the structures formed appressoria, which belong to the second type of simple appressoria group. From the appressoria, infection pegs developed through epidermal cell walls. In 24hr after inoculation, infection hyphae were observed in the epidermal cells, and also in mesophyll cells 48hr after inoculation. It seems that glucose induces the conidial fusion and formation of the netted structures under the condition of more than a given concentration of conidia. The netted structures are thought to play a role of supplying nutrients for the infection by B. cinerea.