MORPHOLOGY OF CHAETOMIUM ERRATICUM

Development of perithecia from single, uninucleate ascospores disclosed a homothallic condition for Chaetomium erraticum. This species was found to produce sessile ascogonial coil initials from uninucleate vegetative cells that become enveloped by hyphae formed at the base of the ascogonium. The ascogonium consists of several cells that are uninucleate or binucleate. A perithecium forms from numerous divisions and enlargement of the surrounding uninucleate cells. Differentiation of the perithecial cells results in the formation of a carbonaceous wall, perithecial hairs, and an ostiole lined with periphyses. A convex hymenial cluster of ascogenous cells forms in the lower half of the centrum from which typical croziers develop. Asci push up into the pseudoparenchyma cells of the centrum. The growth of the ascogenous system is in part responsible for increase in perithecial size. The breakdown of the pseudoparenchyma cells around the developing asci results in the formation of a central cavity in which ascospores are released when the asci deliquesce. No paraphyses are present. The type of development and features of the centrum of C. erraticum and other species of Chaetomium indicate a distinct Xylaria-type centrum.     

Perithecium development in Sordaria brevicollis

Microconidia and ascogonial coils were produced by the two strains of Sordaria brevicollis , WTA and WTa. Over 90% of the microconidia, which functioned chiefly for sexual reproduction, germinated producing short–lived germ tubes. Ascogonial coils with conspicuous trichogynes were observed. A hypha was initiated from the base of the ascogonial coil and soon completely surrounded it, giving rise to the protoperithecium. The ascogonial coil became the ascogonium within the proto–perithecium, and it was surrounded by a pseudoparenchymatous centrum. Many paraphyses arose from pseudoparenchymatous cells. The ascogonium followed the Sordariaceous type of development and gave rise to ascogenous hyphae, croziers, unitunicate asci and ascospores. Anomalous perithecia were observed and perithecia reached maturity 9–1 1 days after inoculation.     

Morphology,development and cytology of Taphrina maculans Butler

Morphology, development and nuclear behavior of the ascogenous stroma and asci in the infection spots have been described inTaphrina maculans Butler. The fungus forms subcuticular and intercellular mycelium in the leaf tissues and the ascogenous layers originate through division of the subcuticular hyphal cells in the infection sites. Germination of ascogenous cells starts with their elongation in the uppermost layer forming asci and ascospores without formation of stalk cells. Meiosis of the fusion (diploid) nucleus occurs in the young ascus as in otherTaphrina species devoid of stalk cells. The haploid chromosome complement in this species consists of 3 chromosomes (n=3). All the cells in the stromatic layer are potential ascogenous cells and ascus formation continues, until all of them are exhausted in the infection spot. Eight ascospores are normally formed in each ascus, but multi-plication of ascospores may occurin situ later. Three morphologically distinct types of ascus opening are encountered, which are apparently not correlated with prevalent environment. Multiplication of ascospores after their discharge from mature asci occurs by budding proceded by a mitotic division of the spore nucleus. Blastospores (budded cells) germinate into short hyphae and binucleate condition of cells originates by mitotic division of the nucleus. Occurrence of giant cells containing 2 nuclei is often observed. Possible origin of Uredinales fromTaphrina-like ancestors has been indicated due to their close resemblance.     

Programmed ascospore death in the homothallic ascomycete Coniochaeta tetraspora

Immature asci of Coniochaeta tetraspora originally contain eight uninucleate ascospores. Two ascospore pairs in each ascus survive and mature, and two die and degenerate. Arrangement of the two ascospore types in individual linear asci is what would be expected if death is controlled by a chromosomal gene segregating at the second meiotic division in about 50% of asci. Cultures originating from single homokaryotic ascospores or from single uninucleate conidia are self-fertile, again producing eight-spored asci in which four spores disintegrate, generation after generation. These observations indicate that differentiation of two nuclear types occurs de novo in each sexual generation, that it involves alteration of a specific chromosome locus, and that the change occurs early in the sexual phase. One, and only one, of the two haploid nuclei entering each functional zygote must carry the altered element, which is segregated into two of the four meiotic products and is eliminated when ascospores that contain it disintegrate. Fusion of nuclei cannot be random-a recognition mechanism must exist. More study will be needed to determine whether the change that is responsible for ascospore death is genetic or epigenetic, whether it occurs just before the formation of each ascus or originates only once in the ascogonium prior to proliferation of ascogenous hyphae, and whether it reflects developmentally triggered alteration at a locus other than mating type or the activation of a silent mating-type gene that has pleiotropic effects. Similar considerations apply to species such as Sclerotinia trifoliorum and Chromocrea spinulosa, in which all ascospores survive but half the spores in each ascus are small and self-sterile. Unlike C. tetraspora, another four-spored species, Coniochaetidium savoryi, is pseudohomothallic, with ascus development resembling that of Podospora anserina.     

Scanning electron microscopy of surface and internal features of developing perithecia of Neurospora crassa.

Stages in the development of perithecia of Neurospora crassa, designated by the time elapsed after crossing, were investigated with the scanning electron microscope, from protoperithecia through perithecia. The usual examination of external features of whole specimens with this instrument was augmented by a freeze-fracture technique which allowed the viewing of development internally as well. Rapid increases in perithecial size soon after crossing were followed by the appearance, in section, of a centrum, at first undifferentiated but subsequently developing ascogenous hyphae. The perithecial beak appeared as a compact mass easily distinguishable in whole specimens from the surrounding hyphae by means of texture as well as shape. Two ascospores were photographed during emergence from an ostiole, but ostioles were found more frequently closed than open.     

印度块菌子囊果内部解剖结构的扫描电镜观察

利用扫描电镜对成熟印度块菌子囊果的内部结构进行了观察,以系统揭示其子囊果内部组织特征,为块菌属的分类以及块菌属真菌子囊果的生理研究奠定基础。观察结果进一步证明,成熟印度块菌子囊果横切面上的白色迷宫状脉络是由不育的侧丝构成,而暗脉则是被侧丝缠绕并包裹着的可育的菌丝组织,即产孢组织,这些白色脉络和暗脉就构成了印度块菌子囊果横切面上迷宫状的纹脉;产孢组织中,可观察到正在发育的大大小小的子囊被缠绕在一起的大量产囊丝与侧丝包裹着,形成密密麻麻微小的类似蜂巢状结构;子囊孢子游离于子囊中,成熟子囊孢子表面有刺状纹饰,刺的顶端有小弯钩。单个子囊内含的子囊孢子大小与其内含的子囊孢子数目有关,子囊内所含的子囊孢子越多,子囊孢子就越小。     

Perithecial ascomycetes from the 400 million year old Rhynie chert: an example of ancestral polymorphism

We describe a perithecial, pleomorphic ascomycetous fungus from the Early Devonian (400 mya) Rhynie chert; the fungus occurs in the cortex just beneath the epidermis of aerial stems and rhizomes of the vascular plant Asteroxylon. Perithecia are nearly spherical with a short, ostiolate neck that extends into a substomatal chamber of the host plant; periphyses line the inner surface of the ostiole. The ascocarp wall is multilayered and formed of septate hyphae; extending from the inner surface are elongate asci interspersed with delicate paraphyses. Asci appear to be unitunicate and contain up to 16 smooth, uniseriate-biseriate ascospores. The method of ascospore liberation is unknown; however, the tip of the ascus is characterized by a narrow, slightly elevated circular collar. Ascospores appear 1-5 celled, and germination is from one end of the spore. Also present along the stems and interspersed among the perithecia are acervuli of conidiophores that are interpreted as the anamorph of the fungus. Conidiogenesis is thallic, basipetal and probably of the holoarthric-type; arthrospores are cube-shaped. Some perithecia contain mycoparasites in the form of hyphae and thick-walled spores of various sizes. The structure and morphology of the fossil fungus is compared with modern ascomycetes that produce perithecial ascocarps, and characters that define the fungus are considered in the context of ascomycete phylogeny.     

MORPHOLOGICAL STUDIES IN PODOSPORA ANSERINA

Perithecium development in Podospora anserina begins with the formation of a coiled ascogonial initial that arises as a lateral branch from a vegetative hypha. Hyphae grow up around the initial, forming an envelope that will become the ascocarp wall. As the ascocarp increases in size, several layers of thin-walled pseudoparenchyma cells form inside the wall, especially at the apex of the ascocarp. Paraphyses arise both from the base of the ascocarp and from the innermost layer of pseudoparenchyma cells and grow inward and upward, completely filling the centrum with tightly packed filaments. During development of the ascocarp the ascogonium proliferates to form ascogenous hyphae along the base of the centrum. Asci arise from the ascogenous hyphae and grow up among the paraphyses. Meristematic growth at the ascocarp apex results in the formation of an ostiole lined with periphyses. Centrum structure in P. anserina could be interpreted as intermediate between the Xylaria and Diaporthe types.     

桫椤自然保护区的虫草及其相关真菌*

从贵州省赤水市桫椤自然保护区采集到虫草5种,其中新种3个:赤水虫草Cordyceps chishuiensis Liang & Liu, 桫椤虫草Cordyceps suoluoensis Liang & Liu和柄壳虫草Cordyceps stipillata Liang & Liu。赤水虫草和其近缘种的主要区别是子座直接从寄主的头部或腹部长出,单生,分枝,子囊壳广拟卵形,无喙。桫椤虫草的主要特征为子囊孢子具细丝状、柱状和囊状等多种形状,子囊孢子在子囊中呈绳状排列。柄壳虫草以子座柄分枝,子囊壳有柄和子囊孢子较粗(2祄)与其近缘种相区别。模式标本保存于贵州大学真菌资源研究室(LFRGU)     

DEVELOPMENT OF THE PERITHECIUM IN GNOMONIA COMARI (DIAPORTHACEAE)

Perithecia of Gnomonia comari (Ascomycetes) mature within 14 days on cornmeal agar under continuous fluorescent light at 25 C. The perithecium is initiated by a coiled, multicellular ascogonium. Branches from somatic hyphae surround the ascogonium. This hyphal envelope early differentiates into two regions: a centrum of pseudoparenchymatous cells and a peripheral wall of more elongated, flattened cells. The wall produces a long, ostiolate beak by eruption of a column of hyphae from the inner layers at the apex; the cells gradually become thick-walled and brown from the peripheral layers inward. Proliferations from the ascogonial cells near the center of the perithecium form a bowl-shaped mass of ascogenous hyphae which expands centrifugally until it appears in section as a crescentic layer across the middle of the centrum. The centrum pseudoparenchyma above this incipient hymenium disintegrates, and short abortive paraphyses extend upward from the subhymenial pseudoparenchyma into the resulting cavity. The paraphyses disintegrate as the asci develop among them. The hymenium gradually pushes downward into the disintegrating subhymenial pseudoparenchyma until it rests on the perithecial wall. Maturing asci become detached from the hymenium, fill the perithecial cavity, and pass through the ostiole. At the tip of the beak they discharge their ascospores forcibly. Diaporthaceae with abortive paraphyses may occupy an intermediate position in a series leading from forms (Gaeumannomyces graminis) with long delicate paraphyses resembling those in the Sordariaceae to forms (Stegophora ulmea) in which the centrum is entirely pseudoparenchymatous.     

The Ascogenous Hyphae of Pyronema confluens

The ascogenous hyphae arise from the oogonium, opposite groupsof nuclei, as minute, enucleate papillae. Nuclei pass into themsingly, rarely two at a time, and a knob-like swelling is formed,containing several nuclei and later growing out into one ormore branches. The nuclei are in single file in the branchesand irregularly arranged in the bulbous base. There are frequentlytwo nuclei in a leading position at the tip of the young branch,but the nuclei may become more evenly spaced as the hypha elongates.The nuclei undergo a simultaneous mitosis. The spindles of thedividing nuclei in the branches are not parallel and this is,therefore, not a conjugate division. Walls are formed as ingrowingrings across the spindles so that the ascogenous hypha, whenseptate, has a uninucleate end cell followed by one, or usuallymore, binucleate cells and a basal bulb containing a variablenumber of nuclei. Croziers are formed as lateral, hooked outgrowths from the binucleatecells. After a simultaneous mitosis of the two nuclei a uninucleateend cell, a binucleate penultimate cell, and a uninucleate stalkcell are formed. Thus, the division in the crozier and thatin the ascogenous hypha are alike. The binucleate cell of the crozier may proliferate to form anothercrozier, or it may form an ascus after the fusion of its twonuclei. The stalk and terminal cell of the crozier may anastomoseand grow out to form a lateral crozier. The chromosome number in the mitosis in the ascogenous hyphais twelve and there are twelve bivalents at the first divisionof meiosis in the ascus. The effect of increasing the illumination of the cultures withan electric lamp in addition to diffuse daylight is to ensurethe further development of all early formed sexual organs, tomake the ascogenous hyphae develop rapidly, to make the lattershort and curved in form with few binucleate cells, and to increasethe tendency towards a period of erect proliferation beforethe formation of the asci and lateral proliferation begin. The bearing of the results on current theories of sexualityin the Ascomycetes is discussed.     

板栗褐缘叶枯病协同致病菌Ophiognomonia castaneae的生活史

采用室外定点观察,子实体诱导及rDNA ITS、MS204、tef1-α 3种分子标记进行系统发育分析等方法,对板栗褐缘叶枯病Phomopsis castaneae-mollissimae的协同致病菌板栗蛇孢日规壳Ophiognomonia castaneae的生活史进行了研究。结果表明,每年7月下旬至8月初叶片发病初期很少分离到O. castaneae,随着病斑扩大该菌的分离频率逐渐增大,至发病后期其分离频率可高达78.5%,甚至可超过致病菌P. castaneae-mollissimae,10月下旬板栗落叶背面的病斑上开始形成O. castaneae的分生孢子盘,11月下旬开始形成O. castaneae的子囊壳原基,次年5、6月越冬落叶背面的病斑上长出子囊壳;带病斑的叶片经室内外诱导,0-25℃范围均可产生成熟子囊壳;湿度是决定子囊壳能否形成的关键因素,强光照不利于子囊壳的产生;分离物的菌丝体在PDA培养基上培养,易产生分生孢子;将分离物分为两种交配型,相互交配后6个月所有处理均未长出该菌的有性型子实体。室外定点观察及rDNA ITS、MS204、tef1-α 3种分子标记表明分离物和病斑上的子囊孢子及其萌发菌丝为O. castaneae的不同生长发育阶段。     

PERITHECIAL FORMATION IN GELASINOSPORA RETICULISPORA. I. EFFECTS OF LIGHT AT TWO DIFFERENT GROWTH STATES

Hyphae of Gelasinospora reticulispora were cultured on corn meal agar in a growth tube at 25 ± 0.4°C under different light conditions. While the hyphal tip was growing, perithecia were not formed under continuous white light (ca. 2000 ergs cm^?2 sec^?1), but some perithecia were initiated in total darkness. However, when white light was given after a dark period, perithecial formation was greatly promoted. In these cases, perithecial formation occurred in older portion of the culture (the portion nearest the point of inoculation) at first, and then gradually spread to the younger portion. Immediately after the tip of hyphae reached the other end of the growth tube, perithecia were induced in the youngest portion of the hyphae irrespective of the photoconditions; then formation proceeded toward the older portion. This induction was not age-dependent, because in growth tubes with different lengths, perithecia always became visible ca. 24 hr after the tip of hyphae reached the other end of growth tube. The photoinhibitory effect was no longer observed thereafter, but photopromotive effect was still evident.     

Ascoma development and phylogeny of an apothecioid dothideomycete, Catinella olivacea

Catinella olivacea is a discomycetous fungus often found fruiting within cavities in rotting logs. Because this habitat would lack the air currents upon which discomycete species normally rely for the dispersal of their forcibly ejected ascospores, we suspected an alternative disseminative strategy might be employed by this species. An examination of the development of the discomycetous ascomata in pure culture, on wood blocks, and on agar showed that the epithecium was gelatinous at maturity and entrapped released ascospores in a slimy mass. We interpreted this as an adaptation for ascospore disperal by arthropods. Developmental data also showed that C. olivacea was unusual among other discomycetes in the Helotiales (Leotiomycetes). For example, the ascoma developed from a stromatic mass of meristematically dividing cells and involved the formation of a uniloculate cavity within a structure better considered an ascostroma than an incipient apothecium. Furthermore, the ascus had a prominent ocular chamber and released its ascospores through a broad, bivalvate slit. These features, along with phylogenetic analyses of large subunit and small subunit rDNA, indicated that this unusual apothecial fungus is, surprisingly, more closely affiliated with the Dothideomycetes than the Leotiomycetes.     

A study of the fine structure of ascosporogenesis in Saccobolus kerverni

Summary Observations of ascospore fromation in KMnO₄-fixed Saccobolus kerverni apothecia with the electron microscope reveal the following sequence. Ascus formation is preceded by the development of croziers whose fine structure differs little from that of vegetative hyphae. Following fusion of the two nuclei in the ascus mother cell, the resultant ascus elongates, and two large vacuoles appear, first below and later above the fusion nucleus. These vacuoles soon occupy dominant positions at the tip and bottom of the ascus and assume a flocculent appearance. Nuclear blebbing occurs during meiosis, mitosis, and the subsequent spore delimitation process in the central cytoplasmic portion of the ascus. Each spore initial is surrounded by two membranes, the plasma and investing membranes, between which the spore wall is deposited in two layers, an inner primary wall and an outer secondary wall. Following primary wall deposition the spores clump; secondary wall deposition begins outside the primary wall at the places where the spores are contiguous. Interdigitation of these walls and disappearance of the investing membranes in the sutures lead to the envelopment of all eight ascospores in a common secondary wall. A flocculent material in the epiplasmic vacuoles aggregates around the mature spore balls.Based on a portion of a dissertation presented to the Faculty of the Graduate School of the University of Texas in partial fulfillment of the requirements for the degree of Doctor of Philosophy.     

CYTOLOGY OF HELMINTHOSPORIUM TURCICUM AND ITS ASCIGEROUS STAGE,TRICHOMETASPHAERIA TURCICA

Knox- Davies , P. S., and J. G. Dickson . (U. Wisconsin, Madison.) Cytology of Helmintho sporium turcicum and its ascigerous stage, Trichometasphaeria turcica . Amer. Jour. Bot. 47(5) : 328—339. Illus. 1960.–The cells of the vegetative hyphae were generally multinucleate. Interphase nuclei resembled those of higher organisms, with a matrix of thread-like chromatin material surrounding a spherical nucleolus. “Beaked” nuclei frequently associated with anastomosing hyphae were interpreted as migrating nuclei. Nuclear division in the vegetative hyphae was rapid. Various division stages were distinguished but it was difficult to make accurate chromosome counts. The nucleoli were discarded at prophase or prometaphase and were reorganized in daughter nuclei at telophase. An outstanding feature of nuclear division was that all the nuclei in a cell divided simultaneously. Conidiophores and conidia were occasionally joined by wide cytoplasmic connections. They were multinucleate throughout their development. Mechanisms therefore exist for the perpetuation of heterokaryons through the conidium. Ascus development was studied in a hybrid between a dark and an albino isolate. Crozier formation was typical and nuclear fusion occurred in the young ascus. Four nuclear divisions were completed in the ascus before there was evidence of ascospore delimitation. Further nuclear division took place in the ascospores whose cells were multinucleate. The occurrence of less than 8 ascospores in an ascus appeared to follow degeneration of nuclei rather than the incorporation of a number of division-Ill nuclei in a single ascopore. Chromosome counts and irregularities in the appearance and behavior of nuclei and chromosomes in the asci indicate that aneuploidy occurs in Trichometasphaeria turcica. It is suggested that aneuploidy is a common phenomenon in the conidial stage of the fungus H. turcicum, and possibly also in other imperfect fungi.     

STUDIES IN THE GENUS NECTRIA. II. MORPHOLOGY OF N. GLIOCLADIOIDES

Hanlin , Richard T. (Georgia Experiment Station, Experiment.) Studies in the genus Nectria. II. Morphology of N. gliocladioides. Amer. Jour. Bot. 48(10): 900–908. Illus. 1961.—Swollen tips of vegetative hyphae develop into multicellular archicarps from which multinucleate ascogonia form. From basal cells of each archicarp arise hyphae which grow up into a prosenchymatous, true perithecial wall; around this wall is formed a thin pseudoparenchymatous stroma of compacted hyphae. The ascogonia give rise to ascogenous cells from which croziers and asci form directly. At the same time, an apical meristem forms cells that grow downward into the centrum. These are pseudoparaphyses. Asci grow up among the pseudoparaphyses, which deliquesce as the ascocarp matures. The ascus tip contains a thick ring with a pore and lateral thickening of the ascus wall. Ascospores are forcibly ejected. The chromosome number is 4. This species conforms to the Nectria Developmental Type of Luttrell.     

Scanning Electron Microscopy on the Perithecial Development of Phyllactinia corylea on Mulberry-II. Sexual Stage

Development of perithecia of Phyllactinia corylea (Pers.) Karst. on mulberry (Morus spp.) leaves was examined by scanning electron microscopy. Two short specialized structures, antheridium and ascogonium, emerged from two separate hyphae, were fused with each other and developed into an egg‐shaped perithecial primordia. These primordia later developed into globose immature perithecia, which covered with protruded wall cells with clear margins. A large number of hyphae emerged from near the base of globose perithecia, which radiated on the leaf surface and thus helped the perithecia to fix to the surface. Specific characteristic penicillate cells and acicular appendages originated from the immature perithecia. The penicillate cells developed with apical sterigma‐like projections from the wall cells of the upper part of immature perithecia, whereas the acicular appendages originated from the shrunken wall cells at the perithecial equatorial planes. On maturation of perithecia, the acicular appendages bent down and pushed the perithecia above the substrate and thus helped them to liberate out. The sterigma‐like projections were covered with paste‐like granular substance, which help the dispersed perithecia to attach to mulberry leaves and branches.