Ascogenous Hyphae Research Articles

Cytological studies of Chaetomium cochliodes

A culture of Chaetomium cochliodes, HLX 440-1, is homothallic. The vegetative hyphal cells are multinucleate and the cells of the ascogenous hyphae are predominantly uninucleate. There is no true crozier stage in the development of the asci from the ascogenous hyphae, though a structure reminiscent of a crozier is formed. The ascogenous cell from which the ascus develops is initially uninucleate.

Ascocarp Development in Two Homothallic Neurosporas

Perithecia of Neurospora terricola and N. dodgei are initiated by the formation of a coiled archicarp, the terminal portion of which is soon differentiated as an ascogonium consisting of several cells. Sterile hyphae which early envelop the female organ give rise to the ascocarp wall. No trichogynes were identified. When the protoperithecium of N. terricola has reached a diameter of approximately 100 /u and that of N. dodgei about 160 u, primary ascogenous hyphae start to develop from the ascogonium. Immediately above these a centrum cavity appears into which paraphyses quickly grow. Asci do not appear until the centrum has attained nearly its maximum size and an ostiolar canal has been formed. As the asci develop, the paraphyses disintegrate. It is concluded that the perithecial centrum is of the "Xylariatype," as defined by Luttrell, and that Neurospora should therefore be placed in the Xylariales in the Luttrell scheme of classification. In many morphological and cytological features, N. terricola and N. dodgei resemble closely not only other species of Neurospora previously studied but also other members of the Sordariaceae (sensu Moreau), particularly members of the genera Gelasinospora, Sordaria, and Pleurage. Noteworthy cytological features encountered were: multinucleate ascogonial cells; ascospores initially uninucleate but becoming binucleate prior to maturation; in N. terricola beaked nuclei bearing prominent appendages at the 4-nucleate stage of ascus development; and a haploid chromosome number of 7 in N. terricola.

DEVELOPMENT AND TAXONOMY OF APIOSPORINA COLLINSII

The ascocarp of Apiosporina collinsii is a pseudothecium which develops from a subiculum. It has pseudoparaphyses, bitunicate asci and an irregular pore in the apical region. The centrum development is of the Pleospora-type and the production of ascogenous hyphae is similar to that described for Spororomia leporina. Apiosporina collinsii is classified in the Venturiaceae, Pleosporales and Loculoascomycetes.The restriction of the parasite to one or a few branches of the host Amelanchier alnifolia is due to the production of cork cells which isolate infected areas in the stem. The retention of infected leaves is associated with cork which surrounds the leaf traces in the petioles.

THE DEVELOPMENTAL MORPHOLOGY OF CLATHROSPORA HETEROSPORA VAR. SIMMONSII

Clathrospora heterospora var. simmonsii has the Pleospora type of development but with two unusual features. Ascogenous hyphae arise from pseudoparaphyses, and an operculate ostiole is formed by the dehiscence of a circular apical cap.

PERITHECIUM DEVELOPMENT IN CHAETOMIUM TRIGONOSPORUM

Chaetomium trigonosporum produces mature perithecia and a Scopulariopsis-like conidial state in cultures derived from single ascospores. The perithecial primordium consists of a central ascogonium surrounded by a vegetative sheath. Division and tangential growth of the peridial cells results in enlargement of the perithecium and the development of a central cavity. The ascogonium initial which typically arises from a single uninucleate cell of the vegetative mycelium soon develops into an ascogonium consisting of several uninucleate cells. Several cells of the ascogonium become multinucleate. From these cells the ascogenous hyphae branch more or less dichotomously toward the apex of the perithecium. The cells of the ascogenous hyphae are uninucleate and apical cells develop into asci directly, without the crozier stage.C. trigonosporum has a "Xylaria type" centrum characteristic of Chaetomium and distinct from the "Ophiostoma type" centrum found in Microascus.

Development and Cytology of Preussia typharum

Ascocarp development in Preussia typharum is similar to that found in the Pleosporales. A stroma originates in an intercalary position on a hypha. It increases in size, and the outer cell layer differentiates to form the wall. The ascogenous system arises from ascogonia scattered throughout the centrum. These give rise to the ascogenous hyphae, which form asci at their tips by means of croziers. The centrum contains paraphysoids, and a distinct hymenium is present. The haploid chromosome number is 11.

The Development and Cytology of Pycnidiophora Dispersa

Ascocarp development in Pycnidiophora dispersa is similar to that in Phaeotrichum. A stroma originates in an intercalary position on a hypha. It increases in size, and the outer cell layer differentiates to form the wall. The ascogenous system forms from a mass of fertile cells in the center of the centrum. These become enlarged and multinucleate and give rise to ascogenous hyphae which form asci at their tips by means of croziers. In time, most of the cells of the centrum become fertile and give rise to ascogenous hyphae. There are no sterile threads in the centrum and no hymenium is present, the asci being scattered throughout the locule. The haploid chromosome number is n = 6.

THE DEVELOPMENT AND CYTOLOGY OF PYCNIDIOPHORA DISPERSA

Ascocarp development in Pycnidiophora dispersa is similar to that in Phaeotrichum. A stroma originates in an intercalary position on a hypha. It increases in size, and the outer cell layer differentiates to form the wall. The ascogenous system forms from a mass of fertile cells in the center of the centrum. These become enlarged and multinucleate and give rise to ascogenous hyphae which form asci at their tips by means of croziers. In time, most of the cells of the centrum become fertile and give rise to ascogenous hyphae. There are no sterile threads in the centrum and no hymenium is present, the asci being scattered throughout the locule. The haploid chromosome number is n = 6.

STUDIES IN THE GENUS CALICIOPSIS

Three species of the genus Caliciopsis, all of which produce cankers on conifers, were investigated with respect to development, morphology, general biology, and pathogenicity. Caliciopsis orientalis is described as a new species. Developmental studies have shown that the ascocarps originate from the surface of an erumpent stroma. The female sexual structures are formed from dark-staining hyphae which arise in the core of the young ascocarp. Certain of these hyphae send out trichogynes which penetrate to the outside of the ascocarp. The hyphae enlarge greatly and produce clusters of ascogonia by a budding process or through meristogenous division of the hyphal cells. The ascogonia may further divide by septum formation and thus become multicellular. Septate, branching ascogenous hyphae grow out from the ascogonia and give rise to tufts of asci from the terminal cells. The stalks of the asci elongate enormously as they are carried up into the hymenium. Homologous development and structure were shown in several members of the Caliceaceae. Differences in the final appearance of the hymenium were attributed to the absence of extensive ascogenous hyphae in the Caliceaceae, but the fundamental similarities were interpreted as evidence of a phylogenetic relationship with Caliciopsis. Comparison of the asci, hymenium, and general habit of two genera of the Coryneliaceae with Caliciopsis confirmed the opinion of previous workers that the two groups are related. Observations on fruiting cycles revealed developmental correlations which indicated the possibility of functional spermatia, but experimental spermatization failed to prove this. Data on spore dissemination, germination, and penetration were also gathered. Canker anatomy and host–parasite relationships were elucidated. Pure cultures were obtained from both spermatia and ascospores. The latter were used to determine nutritional requirements of the fungus by measuring growth response to 14 carbon compounds, 5 nitrogen sources, and 7 vitamins. The effects of pH, temperature, and aeration on vegetative growth in pure culture were also studied. Extensive field observations revealed that one species (C. pseudotsugae) is widespread in British Columbia on three native conifers, and that in addition to primary pathogenicity it offers opportunities for associative effects to other forest pathogens which may result in serious damage. Behavior in pure culture confirmed the evidence of association between the pathogens involved. Pathogenicity was proved by extensive field inoculations.

CONTRIBUTIONS TO OUR KNOWLEDGE OF AMBROSIA FUNGI. I. ASCOIDEA HYLECOETI SP. NOV. (ASCOMYCETES)

BATRA, LEKH R. (U. Kansas, Lawrence), and HELENE FRANCKE-GROSMANN. Contributions to our knowledge of ambrosia fungi. I. Ascoidea hylecoeti sp. nov. (Ascomycetes). Amer. Jour. Bot. 48(6): 453-456. Illus. 1961.-The genus Ascoidea Bref. & Lindau in Brefeld (1891) belongs to the family Ascoideaceae (Endomycetales, Hemiascomycetidae). Ascoidea differs from all other ascomycetes by its possession of characteristic multispored asci which proliferate, the newer asci being formed through the collar-like wall remnants of older asci. Ascogenous hyphae are absent. The present fungus differs in many ways from the type and the only species of the genus, A. rubescens Bref. & Lindau. Ascoidea hylecoeti reproduces asexually by chlamydospores. The asci are conical and many spored. They are aggregated in thick clusters of 50-200 individual asci. The number of ascospores per ascus is much larger than that of A. rubescens and their size is much smaller. Ascoidea hylecoeti is known to occur only in association with the genus Hylecoetus, one of the ambrosia beetles. AMBROSIA fungi are a group of fungi which live symbiotically with some genera of insects. Most of these fungi live saprophytically on plant and in. sect material. although some may have a rather complex and parasitic role together with the insect partner in the formation of so-called ambrosia galls on some plants. Generally, these fungi serve as a major source of food for the developing larvae. Ambrosia fungi are predominantly ectosymbiotes. They are characterized by having mucilaginous spores and fragrant colonies when grown on common laboratory media or when observed in the field. Some of these fungi cause blue staining of logged timber. resulting in heavy economic losses in some parts of the world. These fungi usually overwinter in the form of oidia, thick-walled chlamydospores, or dried, shiny. and mucilaginous crusts of ascospores. The female ambrosia beetles carry the fungi in special structures and the inocula are deposited during oviposition along with the eggs (FranckeGrosmann 1952, 1956, 1957). Taxonomically, most of the ambrosia fungi belong to the Endomycetales, Ophiostomatales and other ascomycetous orders and Fungi Imperfecti (Batra, 1959). Some unidentified Basidiomycetes have also been isolated by the present authors, although no Phycomycetes have so far been observed. Ascolidea hylecoeti was isolated during our studies of symbiotic relationships between ambrosia fungi and ambrosia beetles. Like many other such fungi, this fungus lives as an ectosymbiote and is

DEVELOPMENT OF THE ASCOCARP OF CERATOCYSTIS ULMI

Rosinski, Martin A. (U. Maine, Orono.) Development of the ascocarp of Ceratocystis ulmi. Amer. Jour. Bot. 48(4): 285–293. Illus. 1961.—A study of the development of the perithecium of Ceratocystis ulmi was conducted using classic histological techniques. This study revealed the presence of a singular combination of primitive and advanced characteristics. The perithecium possesses a simple centrum made up only of ascogenous hyphae and small, spherical asci, but croziers are formed prior to ascus formation, and the ascogenous hyphae are arranged in a hymenium. Since development of C. ulmi compares closely with most other accounts of development in other members of the genus Ceratocystis, it appears that Ceratocystis is a good taxon. In addition, because of its intermediate nature and because Ceratocystis is the type genus of the family Ophiostomataceae, this family should be placed in a separate order, the Ophiostomatales.

The cytology of Gloeotinia temulenta (blind seed disease of Rye-Grass)

A study has been made of nuclear organization and reproduction during the life-cycle of Gloeotinia temulenta. All cells of the vegetative hyphae are uninucleate and heterokaryons cannot, therefore, occur; the only sources of genetic variation are thus mutation and sexual recombination. The chromosome number, n = 15, has been determined at both mitosis and meiosis. The mitotic chromosomes range in size from 0·25 μ to just under 1 μ. Most, if not all, of the chromosomes are highly heterochromatic. Prominent ‘prochromosomes’ are found in resting nuclei which approximate in size and number to the mitotic chromosomes. At both mitosis and meiosis ‘heterochromatic association’ is a prominent feature. Nucleolar activity (as indicated by variation in size) has been examined in relation to both cytoplasmic protein synthesis and nuclear reproduction. Nucleolar activity is positively correlated with cytoplasmic basophilia and is greatest in cells which must be presumed to be actively engaged in protein synthesis, viz. young vegetative hyphae and young asci. The apparent absence of the nucleolus from microconidiophores where the nucleus undergoes repeated division indicates that it is not essential for nuclear reproduction. Microconidia in G. temulenta (as in other members of the Sclerotiniaceae) do not germinate and produce a vegetative mycelium; their function is purely sexual. Their inability to germinate is attributed to the very low concentration of ribose nucleic acid (RNA) in the cytoplasm which results from an elaborate pattern of cytological and cytochemical differentiation in the microconidiophores and associated cells. The ascogonium in G. temulenta consists apparently of a coiled hypha embedded in a small stroma. In stromata fertilized by compatible microconidia, hyphae with binucleate cells are produced and these are interpreted as young ascogenous hyphae which subsequently grow up the centre of the apothecium and proliferate in the subhymenium to yield the asci. Nuclear behaviour in the ascus shows no peculiarities. Meiosis is followed by a mitotic division to yield eight nuclei ; a single ascospore is organized around each nucleus.

A Comparative Morphological and Physiological Study of the Species of Dipodascus

SummaryDipodascus belongs to the family Dipodascaceae (Endomycetales, Hemiascomycetidae). The genus is characterized by lacking ascogenous hyphae and ascocarps, and possessing typically ∞-spored and bifurcate asci. There are three species: D. albidus Lagerheim, the type species, D. uninucleatus Biggs, and D. aggregatus Francke-Grosmann. The distinguishing characters of these species are outlined in a key to the species.The life history of D. aggregatus is described for the first time and is compared with that of the other two species.

A Comparative Morphological and Physiological Study of the Species of Dipodascus

SummaryDipodascus belongs to the family Dipodascaceae (Endomycetales, Hemiascomycetidae). The genus is characterized by lacking ascogenous hyphae and ascocarps, and possessing typically ∞-spored an...

Observations on Gymnoascaceae. V. Developmental Morphology of Two Species Representing a New Genus of the Gymnoascaceae

SUMMARYTwo species, Pseudoarachniotus roseus and P. citrinus, are described as representatives of a new genus of Gymnoascaceae. One of these species, P. roseus, is described as new. The morphological development and other diagnostic characteristics are presented for P. roseus and P. citrinus. In both species the gametangia consist of coiling initials which may be designated as antheridia and ascogonia. From the ascogonium there arise ascogenous hyphae which form asci following production of croziers. The groups of asci which arise are entirely devoid of peridial hyphae. This characteristic lack of a peridium, plus the presence of discrete antheridia and ascogonia, the formation of croziers, and the lack of conidia on phialides, distinguish the new genus, Pseudoarachniotus. The interrelationships of Byssochlamys, Talaromyces, Pseudoarachniotus and Arachniotus are discussed.

Observations on Gymnoascaceae. IV. A New Species of Arachniotus and a Reconsideration of Arachniotus trisporus

SUMMARY1. Diagnostic characteristics are provided for a new species, Arachniotus reticulatus, and also for Byssochlamys nivea.2. The morphological development of these two species is discussed and illustrated. The formation of ascogenous hyphae and croziers precedes the production of asci in both species. This agrees with the findings of Rosenbaum for Arachniotus trisporus Hotson and of Benjamin for Byssochlamys nivea Westling.3. Arachniotus trisporus Hotson was found to lack a true peridium. Therefore, this species falls within the generic limits of Byssochlamys as was previously recognized by Benjamin and by Cain. However, the results obtained here verify the position taken by Benjamin in placing A. trisporus Hotson in synonomy with B. nivea Westling.4. The position of the genus Byssochlamys within the family Gymnoascaceae is discussed.

Observations on Gymnoascaceae. IV. A New Species of Arachniotus and a Reconsideration of Arachniotus Trisporus

SUMMARY1. Diagnostic characteristics are provided for a new species, Arachniotus reticulatus, and also for Byssochlamys nivea.2. The morphological development of these two species is discussed and illustrated. The formation of ascogenous hyphae and croziers precedes the production of asci in both species. This agrees with the findings of Rosenbaum for Arachniotus trisporus Hotson and of Benjamin for Byssochlamys nivea Westling.3. Arachniotus trisporus Hotson was found to lack a true peridium. Therefore, this species falls within the generic limits of Byssochlamys as was previously recognized by Benjamin and by Cain. However, the results obtained here verify the position taken by Benjamin in placing A. trisporus Hotson in synonomy with B. nivea Westling.4. The position of the genus Byssochlamys within the family Gymnoascaceae is discussed.

Development of the Ascocarp of Anthracobia melaloma

SUMMARYAnthracobia melaloma is a small operculate discomycete which is found most frequently on burnt wood. It grows and fruits readily in pure culture. The species is heterothallic.Arichicarps are produced by both mating types when these are grown separately. Antheridia cannot be distinguished except when they are in contact with a trichogyne.Plasmogamy is effected by the coiling of the tip of the trichogyne around an antheridial hypha. One cell of the antheridial hypha, the one in contact with the very tip of the trichogyne, swells until it is almost spherical. The walls between this swollen cell (the antheridium) and the trichogyne break down permitting the interchange of nuclei and cytoplasm.The archicarp can be separated into 3 distinct regions just prior to the formation of ascogenous hyphae. The ascogonial cells have very large pores in the cross walls. The cells of the trichogyne can be distinguished by the amorphous structure of the protoplasm and the swellings in the cross walls of the 6 to 8 cells nearest to the ascogonium. The stalk cells are distinguished best by the broad hyphae branching from them.Ascogenous hyphae develop from 2, 3, or 4 ascogonial cells. These rapidly spread throughout the young apothecium and become septate. Branches arise from the cells of these primary ascogenous hyphae and 2 nuclei migrate into each of these branches. The lateral branches immediately bend over forming characteristic croziers, and conjugate division of the 2 nuclei in these laterals presumably occurs. Asci do not form immediately after the first croziers are developed. Instead, the nuclei in the penultimate cell usually divide conjugately again. This process of conjugate division in the penultimate cell may occur many times before an ascus is finally formed.The hyphae giving rise to the sterile portion of the apothecium develop from the stalk cells of the archicarp. These are broad hyphae which contain a darkly stained protoplasm and nuclei of the same size as the nuclei in the ascogonial and stalk cells.The formation of the cortex and paraphyses is the result of sympodial growth of the sheath hyphae as described by Corner (1929). The hairs are merely terminal cortical cells which differentiate further by elongation and by darkening and further thickening of the walls.

Observations on Gymnoascaceae. II. Two New Species of Myxotrichum

SUMMARY1. Diagnostic characteristics are provided for two new species, Myxotrichum thaxteri and M. conjugatum.2. The morphological development of these two species is discussed and illustrated. The formation of ascogenous hyphae and croziers precedes the production of asci.3. A comparison is made of the gametangial types represented in Myxotrichum uncinatum, M. thaxteri, M. emmonsii, and M. conjugatum. The value of gametangial morphology in taxonomy is discussed.

BIOLOGY, CYTOLOGY, AND TAXONOMY OF COCHLIOBOLUS SATIVUS

Cochliobolus sativus (Ito & Kurib. ex Kurib.) Drechs. ex Dast. produced mature ascocarps on seeds of Zea mays L., previously disinfested with mercuric chloride, boiled one minute to kill the embryo and partly immersed in Sach's agar. Isolates of the conidial state, Helminthosporium sorokinianum Sacc. ex Sorokin (= H. sativum Pamm., King & Bakke), and monoascosporic isolates were hermaphroditic and heterothallic. Uninucleate, spherical spermatia 1.7 μ wide, the sole male agents in plasmogamy, were produced in phialids in slimefilled spermogonia measuring 2.5 × 2.5 mm. Hyphal fusions and conidiation did not initiate the heterokaryon in the ascogonium. Homokaryotic isolates and incompatible crosses produced partially mature ascocarps by differentiation of maternal stroma. Pseudoparaphyses extended downwards from subapical stromatic cells and produced locules. Subsequently in compatible crosses the heterokaryotic ascogenous hyphae grew from the sub-basal pseudoparenchyma and produced a fascicle of asci in the locule. Eight scolecospores, uninucleate at inception, formed after meiosis. The asci had two walls (bitunicate) but the inner wall was not evident in asci filled with spores nor functional in spore discharge. Whole asci extruded from the ascocarp in slime and dehisced in water by a terminal circumscissile rupture. Cochliobolus Drechs. was placed in the Pseudosphaeriaceae Höhn. sensu Luttrell in the Pseudosphaeriales Thiessen & Sydow.