Single Phialides Research Articles

A new species of Dictyochaeta (Sordariomycetes, Chaetosphaeriales, Chaetosphaeriaceae) from freshwater habitats in China.

Freshwater fungi refer to the fungi that depend on the freshwater habitats for the whole life cycle or part of their life cycle. In this context, a new aquatic hyphomycete was isolated from decaying wood in a freshwater habitat in Jiangxi Province, China. Dictyochaetajiangxiensis sp. nov., a new aquatic hyphomycete, is characterised by its unbranched, septate, base-fertile conidiophores with multisepta and single phialide at the apex, brown, sterile seta, monophialidic, subcylindrical conidiogenous cells narrowing below the funnel-shaped collarette, hyaline, unicellular, thin-walled, smooth, guttulate, falcate to subclavate conidia narrowly rounded at both ends with hair-like appendages. Phylogenetically, the new species Dictyochaetajiangxiensis clustered together with Dictyochaetabrevis MFLU 19-0216 in a well-supported clade, but formed a separate branch. In order to better define the taxonomic status of the new species, a phylogenetic tree of most closely-related taxa in Chaetosphaeriaceae was established, based on multi-locus sequences (ITS and LSU). The novel species is described and illustrated. Newly-generated molecular data of Dictyochaetajiangxiensis is also provided.

Trichocladium solani sp. nov.-A New Pathogen on Potato Tubers Causing Yellow Rot.

A new species, Trichocladium solani, was isolated from potato (Solanum tuberosum L.) tubers from Russia. The species has no observed teleomorph and is characterized morphologically by non-specific Acremonium-like conidia on single phialides and chains of swollen chlamydospores. Phylogenetic analysis placed the new species in a monophyletic clade inside the Trichocladium lineage with a high level of support from a multi-locus analysis of three gene regions: ITS, tub2, and rpb2. ITS is found to be insufficient for species delimitation and is not recommended for identification purposes in screening studies. T. solani is pathogenic to potato tubers and causes lesions that look similar to symptoms of Fusarium dry rot infection but with yellowish or greenish tint in the necrotized area. The disease has been named "yellow rot of potato tubers".

First report of Fusarium oxysporum Causing Fusarium Dieback on Archidendron clypearia in China.

Archidendron clypearia (Jack) Benth. (common name: Monkey-pod) is a perennial arbor tree belonging to the family Fabaceae. It is used to produce a traditional medicine to treat a variety of heat toxicity symptoms in China. The distribution of A. clypearia mainly include Guangdong, Fujian, and Zhejiang provinces in China as well as other countries in Southeast Asia. In 2018, about 30 Monkey-pod trees were observed showing typical dieback symptoms in a commercial plantation (114°36'09.401″E, 22°58'38.553″N) of Huizhou, Guangdong Province, China. In addition, white cylindrical sawdust exudates from exit holes of ambrosia beetles were observed on the trunks and main branches of the diseased trees. Discoloration was seen around the exit holes of the beetles by splitting the wood. Samples of symptomatic and asymptomatic wood tissues of branches, trunks, and roots were collected from 11 trees. To identify the pathogen, the samples were disinfected with a sodium hypochlorite solution containing 50 g/l chlorine for 60 s, rinsed three times with sterile distilled water, and placed on potato dextrose agar (PDA) for culture at 25℃ for 14 days. Beetles from exit holes of the pathogen-infected wood tissues were also collected and identified as Xyleborus affinis by their cytochrome c oxidase I (COI) sequences (GenBank accession numbers: MT921005 and MT921006) as well as morphological features. After two weeks incubation, 37 single-spore isolates were obtained (31 from galleries of branches and trunks, and 6 from mycangia and the body surface of beetles). Colonies on PDA were fusarium-like, pale orange, floccose with abundant aerial mycelia, and growing at the rate of 3.0 to 4.5 mm/d at 25℃. Conidiophores from the aerial mycelia often had single phialides. Microconidia were hyaline, 0-1 septate, (4-)6-12(-16) × 2-4 μm (n=100), Macroconidia were hyaline, ellipsoidal to falcate, 2-4 septate, (10-)25-45(-50) × 3-6 μm (n=100), with basal foot cells shaped to pointed and apical cells tapered and curved. Two representative isolates (CYML 367, 368) were used for molecular identification and pathogenicity tests. The internal transcriptional spacer region (ITS), β-tubulin (TUB), and translation elongation factor-1α (TEF 1-α) regions were amplified with primers ITS1F/ITS4 (White et al. 1990), Bt2a/Bt2b (Glass and Donaldson 1995), and EF1-728F (Carbone and Kohn 1999) /EF-2 (O'Donnell et al.1998), respectively. DNA extraction and PCR conditions were followed the methods described by Yin et al. (2019). The amplified fragments were sequenced. The results of BLAST demonstrated that the fragment sequences of ITS (468 bp), TEF 1-α (616 bp), and TUB (295 bp) of isolates CYML367 and CYML368 had 100% similarity to correspondence sequences from the Fusarium oxysporum Schlecht. emend. Snyder & Hansen species complex (GenBank accession numbers MT032694, JF740777, and MN451171, respectively). Sequences generated from this study were deposited into GenBank under accession numbers MN826824 and MN826825 (ITS), MN839680 and MN839681 (TUB), and MN839682 and MN839683 (TEF 1-α). Pathogenicity tests were conducted on 2-year-old seedlings (60-70 cm height, 1.0-1.2 cm in diameter) of A. clypearia with the representative isolates. Ten seedlings were inoculated with each isolate. The stem surface was disinfected with 75% ethanol for 30 s, and rinsed with sterilized water, wounded by removing part of the phloem and xylem, and placed with a mycelial plug (5 mm diameter) from the margin of a 7-day-old PDA plate with mycelia facing the cambium. The inoculated wounds were wrapped with a medical sterile gauze to prevent desiccation and contamination. Control plants were inoculated with non-colonized PDA plugs. These inoculated and control plants were incubated in a chamber at 25℃, 50% humidity, 12 h light/12 h dark cycle. After 3 weeks, all inoculated plants displayed Fusarium dieback symptoms similar to those observed on the original diseased trees in the plantation. The average lesion lengths (1.2/1.7 cm) caused by two isolates were all significantly longer than the wounds in the negative controls (P<0.05). The same fungus was re-isolated from the symptomatic plants, thus fulfilling the Koch's postulates. Further studies should be conducted on the potential vector association, transmission route, and management strategies of this pathogen on A. clypearia in growing regions of China. To our best knowledge, this is the first report of F. oxysporum causing dieback on A. clypearia in China.

Aspergillus loretoensis, a single isolate from marine sediment of Loreto Bay, Baja California Sur, México resulting as a new obligate halophile species

An obligate halophile fungal was isolated from 275m deep marine sediments and is characterized here for the first time. Its optimal growth was at 15% NaCl even though it was able to grow at 25% and is incapable of growth with no NaCl. Based on its morphological characteristics as conidia chain production in a single phialide, the fungal is related to the genus Aspergillus, subgenus Polypaecilum. Phylogenetic molecular analysis using several markers (ITS1-2; RPB1; RPB2; Cct8; TSR1; CaM; BenA) places the fungal isolate closer to Aspergillus salinarus and A. baarnensis. However, its morphological and molecular differences establish it as a new species, Aspergillus loretoensis sp. nov.

Taxonomy of the Sphaerostilbella broomeana-group (Hypocreales, Ascomycota).

Three new species, closely related to Sphaerostilbella broomeana, are described from the USA and India. These species form septate conidia from simple conidiophores with individual branches terminating in a single phialide and chlamydospores. Teleomorphs, known for S. broomeana and S. appalachiensis, are characterised by hairy perithecia and fusiform, apiculate, and conspicuously warted ascospores. This combination of characters distinguishes the S. broomeana-group from other members of Sphaerostilbella that all form gliocladium-type anamorphs and mostly grow on basidiomata of Stereum spp. Like in other species of the genus, the majority of hosts of the species described in this paper belong to wood-inhabiting taxa of Russulales. Sphaerostilbella broomeana had been recorded from a few regions in Europe and exclusively on Heterobasidion annosum. Herein, it is reported also from H. parviporum in many other localities and on H. insulare s.l. at the foothills of the Himalayas. Its sister species, found in the same region in northern India on another member of Russulales (Dichostereum effuscatum), is described as S. himalayensis. The two species described from North America colonize polypores from various taxa. Whereas S. appalachiensis occurs in eastern USA, with H. irregulare among its hosts, S. toxica is so far known only from two locations in eastern Texas, growing on Gloeophyllum striatum (Polyporales). Despite their great similarity in morphology and ITS rDNA, TEF1 sequences clearly distinguish these two North-American species. Moreover, the two strains of S. toxica appeared metabolically distinct as their organic extracts strongly inhibited the growth of human pathogenic microbes grown in vitro. Phylogenetic analysis of rDNA sequences supports monophyly of the genus Sphaerostilbella and the included S. broomeana-group, established here.

First Report of Paecilomyces variotii Isolated From Citrus Psyllid (Diaphorina citri), the Vector of Huanglongbing of Citrus, in China

HomePlant DiseaseVol. 100, No. 12First Report of Paecilomyces variotii Isolated From Citrus Psyllid (Diaphorina citri), the Vector of Huanglongbing of Citrus, in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Paecilomyces variotii Isolated From Citrus Psyllid (Diaphorina citri), the Vector of Huanglongbing of Citrus, in ChinaX. B. Song, L. H. Zhang, A. T. Peng, B. P. Cheng, and J. F. LingX. B. SongSearch for more papers by this author, L. H. ZhangSearch for more papers by this author, A. T. PengSearch for more papers by this author, B. P. ChengSearch for more papers by this author, and J. F. LingSearch for more papers by this authorAffiliationsAuthors and Affiliations X. B. Song , Agricultural College of South China Agricultural University, Guangdong Province, Key Laboratory of Microbial Signals and Disease Control, Guangzhou 510640, China, and Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Guangzhou 510640, China L. H. Zhang , Agricultural College of South China Agricultural University, Guangdong Province, Key Laboratory of Microbial Signals and Disease Control, Guangzhou 510640, China A. T. Peng B. P. Cheng J. F. Ling , Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Guangzhou 510640, China. Published Online:15 Sep 2016https://doi.org/10.1094/PDIS-04-16-0510-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat The citrus psyllid (Diaphorina citri) is a small insect that feeds on the leaves and stems of citrus trees. It is also the only insect vector of Huanglongbing (HLB), the most devastating disease of the citrus industry in China. Controlling the citrus psyllid population density is an important safeguard measure against HLB, and biocontrol is the most effective method to control citrus psyllid in the future (Meyer et al. 2008). Citrus psyllid adults were collected into sterile centrifuge tubes from a citrus field, which had many diseased citrus trees infected HLB in Guangzhou, China, in 2015. The psyllids were placed directly on a potato dextrose agar (PDA) plate and incubated at 27°C with alternating light and dark for 2 to 3 days. Mycelium was picked into a new PDA culture plate, and the purification was repeated three times. Conidia were then suspended in sterile water for single-spore isolation. An isolate of an entomophagous fungus, GZMS-11, was isolated from citrus psyllid by the above method. GZMS-11 grew well on PDA, showed a round and fluffy colony, turning from white to brown with age. The colony diameter was 5.86 cm after 10 days at 27°C, with alternating light and dark. Brown pigment was produced and diffused into the medium after the colonies were cultured for 3 to 4 days. Conidiophores were erect and most of them were generated on the mycelium individually. Single phialide or multiple phialides were generated from the metulae, and they formed broom-like branches. The phialide size was 2.5 to 3.5 × 15 to 20 μm (avg. 3.0 ± 0.5 × 17.1 ± 1.5, n = 100), slender and acuminate, slightly curved, and the conidia attached with the phialide; the oval conidia size was 5.5 to 7.5 × 2.5 to 3.5 μm (avg. 6.2 ± 0.5 × 3.1 ± 0.5, n = 100). The cultural characteristics of the GZMS-11 was consistent with Paecilomyces variotii. Total DNA of GZMS-11 was extracted and the rDNA ITS region was sequenced by PCR using the universal primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′, forward) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′, reverse). The PCR product showed a sequence identity of 97.0 to 99.0% with sequences of P. variotii strains (AY904061, FJ895878, JN798498, AY753335) reported in GenBank. Based on the biological characteristics and ITS sequence, isolate GZMS-11 was identified as a novel strain of P. variotii. The pathogenicity against citrus psyllid of GZMS-11 was tested by treating citrus psyllid adults with a conidial suspension at the concentration of 1.0 × 108 spores/ml (Gandarilla-Pacheco et al. 2013). The corrected mortality rates were 35.83, 66.71, and 97.16% after 3, 7, and 10 days, respectively. Two days after treatment, mycelium could be observed on the surface of some citrus psyllid through a stereoscopic microscope. After 7 days, spore production structure could be observed visually on the citrus psyllid. These results have indicated that GZMS-11 has strong pathogenicity against citrus psyllid adults, and has the potential for being used for biological control of citrus psyllid in the future.

A phylogenetic assessment and taxonomic revision of the thermotolerant hyphomycete genera Acrophialophora and Taifanglania

We assessed the phylogenetic relationships of 19 isolates belonging to Acrophialophora and Taifanglania based on internal transcribed spacer (ITS), nuclear 18S subunit (nuc 18S) rDNA and β-tubulin sequences. Phylogenetic data showed that Acrophialophora and Taifanglania comprise a monophyletic clade, but did not support the distinction of two genera. Being the older and more frequently used name, Acrophialophora is adopted as the generic name and Taifanglania is treated as a synonym. The generic concept of Acrophialophora is emended to include the morphological characters formerly used to distinguish Taifanglania. Three new thermotolerant species isolated from soil samples in China are described and illustrated, (i) A. ellipsoidea, with solitary phialides tapering into thin necks and long chains of ellipsoidal to fusiform conidia, (ii) A. angustiphialis with single phialides terminal or lateral on hyphae, and long chains of ellipsoidal or fusiform conidia and, (iii) A. acuticonidiata with single phialides and fusiform conidia with acute ends. Phylogenetic analyses show that A. acuticonidiata, A. angustiphialis and A. ellipsoidea are most closely related to A. curticatenata, A. hechuanensis and A. major, respectively. Growth tests showed that the three new species are thermotolerant, with optimal growth temperatures of 37–40 C, and maximum growth temperatures near 50 C. A key to the accepted species of Acrophialophora is provided.

FIRST REPORT OF PANAMA WILT DISEASE OF BANANA CAUSED BY FUSARIUM OXYSPORUM f. sp. CUBENSE IN PAKISTAN

In Pakistan, Dwarf Cavendish bananas are grown on 30.000 ha with an annual production of 141.200 tons. In 2012-13, bananas grown in the district of Thatta (Sindh province) came down with an unknown disease, which was also observed in the Hyderabad region. Severely affected plants showed a conspicuous yellowing, followed by their death. Cross-sectioned pseudostems disclosed the presence of reddish-brown to dark-brown discolouration of vascular tissues and rhizome. Fruits had a reduced size. Isolations carried out on PDA from pseudostem, rhizome and roots yielded the consistent recovery of Fusarium oxysporum f. sp. cubense, the agent of Panama disease, which was identified based on morphology of: (i) macroconidia, sickle-shaped mostly 3 septate (occasionally 5 septate), pointed at both ends, 30-60x3-5 μm in size, borne on single phialides; (ii) microconidia, kidney shaped, without septation, produced on false heads, 5-12x3-5 μm in size. The optimum temperature for colony growth and sporulation was 25°C and 30°C, respectively. For pathogenicity tests, 12-week-old banana plantlets of cv. Basri were inoculated with 30 ml of a conidial suspension (106 conida/ml). Wilt symptoms developed after 45 days on the inoculated plants from which the same fungus used for inoculation was recovered. Thus, Pakistani banana plantations are affected by Panama wilt, a devastating disease that has damaged thousands of hectares of banana plantations in different parts of the world (Ploetz, 2000). The cultivation of banana in Pakistan is at high risk, as Panama wilt has the potential to cause losses similar to those induced by the epidemic of banana bunchy top disease, which virtually eradicated banana cultivation from the Sindh in 1980s (Khalid et al., 1993).

Phialosimplex salinarum, a new species of Eurotiomycetes from a hypersaline habitat.

Salt mines represent an extreme environment with hypersaline conditions, complete darkness, and low nutrient availability. The diversity of filamentous fungi in such habitats is largely unknown. Eight strains of an unknown fungus were isolated from water samples of the salt mine in Berchtesgaden (Bavaria, Germany). They could be assigned to the ascomycete genus Phialosimplex, based on their common characteristics of producing conidia in chains or in heads on single phialides. Species of this genus are hitherto known to cause mycoses in dogs and have been found in mummies. Using molecular and morphological methods, the isolates are established as a new species, Phialosimplex salinarum sp. nov. Basipetospora halophila is also transferred to Phialosimplex as P. halophila comb. nov.

Morphology and molecular taxonomy of Evlachovaea-like fungi, and the status of this unusual conidial genus

The entomopathogenic anamorphic genus Evlachovaea was described to differ from other fungi in forming its conidia obliquely to the axis of the conidiogenous cell and with successive conidia having alternate orientations with a zipper- or chevron-like arrangement resulting in flat, ribbon-like chains. Morphological and molecular studies of six Evlachovaea-like isolates baited from Central Brazilian soils using Triatoma infestans (a vector of Chagas disease) and of other entomopathogens with Evlachovaea-like conidiogenesis led to a re-evaluation of the status of this little known fungal genus. The Brazilian isolates formed two distinct groups based on gene sequences for both the internal transcribed spacer (ITS) and translation elongation factor (EF-1α) genes, morphology, and growth patterns; both groups also differed from the type species, Evlachovaea kintrischica. More detailed studies of these fungi indicated that the alternatingly oblique orientations of forming conidia are neither a stable nor invariant character (even on single phialides). Furthermore, the molecular cladistic analysis unambiguously placed the Evlachovaea isolates firmly within the genus Isaria (Hypocreales: Cordycipitaceae). The ITS sequences of E. kintrischica were very similar or even identical to those of Isaria amoenerosea and Isaria cateniobliqua, thereby suggesting that E. kintrischica is a synonym of one of these species, and that the genus Evlachovaea must be treated as a later synonym of Isaria, which must now be recognized to include several highly divergent modes of conidiogenesis. These taxonomic findings are discussed in the context of dramatic changes recently imposed on the nomenclatural standards used to determine the correct names of all pleomorphic fungi.

First Report of Phaeoacremonium parasiticum Causing Petri Disease of Grapevine in Peru.

Since 2005, symptoms of grapevine decline have been observed on 4- to 8-month-old grapevines (cvs. Red globe and Crimson) grafted onto 1103 P rootstock in Ica and Pisco valleys in southern Peru. Affected plants exhibited weak growth, interveinal chlorosis, necrosis and wilting of leaves, and death. Dark brown-to-black streaking of the xylem was seen when transverse or longitudinal cuts were made in the trunk and shoots. Symptomatic plants were collected and sections (5 cm long) were cut from the zone between the rootstock and the scion, surface sterilized for 1 min in a 1.5% sodium hypochlorite solution, and washed twice with sterile distilled water. The sections were split longitudinally, and small pieces of discolored tissues were placed onto potato dextrose agar (PDA) supplemented with oxytetracycline (500 mg liter-1). Plates were incubated at 25°C in the dark for 15 days. A Phaeoacremonium sp. was consistently isolated from necrotic tissues. Single conidial isolates were obtained and grown on PDA and malt extract agar (MEA) in the dark at 25°C for 3 weeks until colonies produced spores (3). Colonies were brown on PDA and olive brown on MEA. Conidiophores were branched, 27.5 to 67.5 (42.5) μm long, and often consisting of a single phialide. Conidia were hyaline, oblong ellipsoidal, 2.5 to 4.5 (3.6) μm long, and 1.2 to 1.9 (1.6) μm wide. On the basis of these characteristics, the isolates were identified as Phaeoacremonium parasiticum (Ajello, Georg & C.J.K Wang) W. Gams, Crous & M.J. Wingf. (teleomorph Togninia parasitica L. Mostert, W. Gams & Crous) (2,3). Identity of isolate Ppa-1 was confirmed by PCR-restriction fragment length polymorphism of the internal transcribed spacer region (Phaeoacremonium-specific primers Pm1-Pm2) with the restriction enzymes BssKI, EcoO109I, and HhaI (1). Additionally, the beta-tubulin gene fragment (primers T1 and Bt2b) of this isolate was sequenced (GenBank Accession No. FJ151015). The sequence was identical to the sequence of P. parasiticum (GenBank Accession No. AY328379). Pathogenicity tests were conducted using the isolate Ppa-1. Approximately 20 μl of a suspension containing 103 conidia ml-1 was injected into the pith of four nodes on each of 10 dormant, unrooted, 15 cm long cuttings of cv. Red Globe. Four nodes on each of 10 cuttings were used as controls and injected with an equal volume of sterile distilled water. Inoculation points were covered with Parafilm. The cuttings were planted in plastic pots and maintained at 24 ± 3°C in diffuse light, watering as needed. Within 2 months of inoculation, all P. parasicitum-inoculated cuttings exhibited shoots with very poor growth with small leaves and short internodes. In the xylem vessels, black streaks identical to symptoms observed in declining vines in the vineyard were observed. Control plants did not show any of these symptoms. The fungus was reisolated from internal tissues of symptomatic shoots of all inoculated cuttings but not from the control shoots. To our knowledge, this is the first report of P. parasiticum causing young grapevine decline in Peru.

Taxonomy of the Acarine Parasite Hirsutella thompsonii

SUMMARY Cultural features and morphology of 11 isolates of the hyphomycete Hirsutella thompsonii, an important pathogen of various eriophyoid mites, are described and illustrated. Three morphologically distinct groups of H. thompsonii were distinguished and accordingly three varieties are proposed: H. thompsonii var. thompsonii, var. vinacea and var. synnematosa. The variety vinacea is characterized by vinaceous colonies and a different host, Acalitus vaccinii. The strains accommodated in the var. synnematosa were isolated from Eriophyes spp. and related genera. In fresh culture they produce cream-colored cylindrical synnemata, bearing two kinds of phialides: (1) single phialides with solitary conidia and (2) densely crowded phialides with catenulate conidia. In all three varieties two different conidiogenous structures are formed: (1) solitary often proliferating phialides producing one or more globose, verrucose conidia and (2) polyblastic conidiogenous cells with smooth-walled, subglobose to ellipsoidal conidia. Although H. thompsonii differs in some morphological characters from other species in the genus, its maintenance in Hirsutella is proposed.

Contribution to the morphology of the productive strains of Penicillium chrysogenum Thom from the Wisonsin family.

The morphology of four productive strains ofPenicillium chrysogenum Thom from the Wisconsin family was studied. The strains Q-176, 47–1564, 49–133, 51–20Z, which were naturally or artificially obtained mutants of thePenicillium chrysogenum NRRL 1951 strain were very variable as to the colony structure and the character of conidiophores. The present study is concerned with the evaluation of their taxonomic position. The macrohabitus of the colonies was not remarkably changed. All different types of colonies (U, D, C, B, rarely A) described by Backus and Stauffer, were found on Czapek agar; they were not recognized on malt agar. Deviations from the normal asymmetric conidiophore were found with every type of colonies, most often with the more floccose or lanose ones showing a higher and a sparser overgrowth. These deviations or changes in the microstructure were divided into three degrees according to their quality and occurrence: (1) A strongly divaricate conidiophore where only metulae and phialides were developed; (2) monoverticilate conidiophore or single phialides on the conidiophore filament; (3) degeneration of phialides or metulae to sterile globose cells or an ultimate reduction of conidiophore to dichotomically branched stump-like hypha. The investigated strains can be involved in the taxonPenicillium chrysogenum Thom; it is necessary, however, to include some additional traits into the characteristics of the taxon: Colonies of the naturally or artificially obtained mutants often have lanose overgrowths sporulating sparsely. Formation of the yellow pigment and the exudate was not obligatory. conidiophores of these strains had a tendency to be more simple. They were scarcer, divaricately open, characterized sometimes by the formation of monoverticilate penicilli. A degeneration was frequently found of the ends of conidiophores (phialides and metulae) to globose enlarged sterile cells as well as the formation of giant cells in the mycelium or reduction of conidiophore to dichotomically branched hypha with stump-like ends.