Perithecial formation in Gelasinospora reticulispora III. Inhibitory effects of near-UV and blue light during the inductive dark period

Growing hyphae of Gelasinospora reticulispora required a continuousdark period prior to photoinduction of perithecia. The inductivedark period was interrupted by brief exposure of the hyphaeto white light so that the formation of perithecia no longertook place. Photosensitivity of the hyphae in terms of the light-breakeffect gradually changed during the inductive dark period. Sensitivityreached its maximum at the 18th hr of the dark period when anirradiation of 1?10⁵ ergs cm^–2 of near-UV light or 4?10⁴ergs cm^–2 of blue-light was sufficient for the light-break.Red and far-red light had no effect at all. The light-breakeffect was limited to the irradiated portion of the hyphae anddid not affect any unirradiated portions. Inhibitory effecton perithecial formation of continuous white light could betotally replaced for several days with intermittent irradiationof near-UV or blue light if given for 5 min every 4 hr. (Received December 18, 1973; )     

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.     

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.     

Studies on the development of perithecium of Ceratocystis stenoceras

The development of the perithecium of Ceratocystis stenoceras was observed by a light microscope and by a scanning electron microscope.The fungus has developed dark brown perithecia on wheat agar medium in three days of incubation. Perithecial primordia appeared as tightly knotted coils. At the center of it an oval ascogonium was observed. The ascogonium was developed from a lateral wall of a hypha, and the hyphae covering the ascogonium branched at the basal part where the ascogonium was attached. These hyphae branched repeatedly in the developmental growth to cover the ascogonium, and it was finally covered tightly. The plasmogamy of this fungus is much probably performed by the gametangial contact. As the stage proceeded, the ascogonium elongated, the terminal and the basal portions of it swelled and cleavage of the ascogonium resulted. Each of the cleaved ascogonia germinated continuously and stretched out the ascogenous hyphae. About that time the cells consisting of perithecia were vacuolated from the center and successively dissolved, so that a space was formed in the center of the body. Ascogenous hyphae continued to develop downwards, and their end were fixed to the inner wall of the body.The upper portion of the hyphae converged to the center of the body and the ascogenous hyphae became the supporting tissue for ascus formation.Hook formation was observed prior to the ascus formation. After completion of karyogamy by hook formation, the fissure appeared on the ascus and the end portion was released. The released portion included eight ascospores. The ascus had a smooth surface and no special structure was seen on the top. As the asci were matured, they evanesced by themselves and concurrently ascospores came out. Finally the body was massively filled with ascospores.     

Perithecial formation in Gelasinospora reticulispora

When hyphae in the basal region of 72-hold, dark-grown mycelium of G. reticulispora (Greis et Greis-Dengler) C. et M. Moreau (Sordariaceae) were exposed to a microbeam of monochromatic blue light, perithecial initials were induced only in hyphae located within or in the vicinity of the light spot. The average distance from the periphery of the microbeam spot to perithecial initials produced outside the spots was 100–200 m, regardless of the beam diameter or the incident light energy. The maximum distance of a perithecium formed outside a microbeam spot was ca. 700 m. The inductive effect of blue light became detectable at 100 J m^-2 and reached a maximum at 1000 J m^-2, regardless of beam diameter. A microphotographic examination showed that the microbeam irradiation was effective only in hyphae rich in protoplasm.V=Inoue and Furuya, 1975 b     

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.     

Methods of investigating populations of the take-all fungus (Ophiobolus graminis) in soil

Attempts to isolate Ophiobolus graminis directly from infested soils failed, so host-infection techniques were used to study soil-borne populations of the fungus. Extracting organic debris from soils and grading it by wet sieving through standard meshes concentrated the fungus. Fractions were tested for infectivity either as layers in pots of sand or by packing into short lengths of polyvinyl chloride tubing, through which wheat seedlings were grown. Coarse debris (retained by 420 μ aperture sieves) was most infectious and usually caused lesions within 3 weeks; whole soil and especially fine debris (< 420 μ) caused fewer and less severe infections, which often became apparent only after 3 weeks. Slight infectivity of the sediment fractions was attributed to imperfect separation of debris. Soil sampled in crop or stubble rows caused more infections than soil from between rows. Usually seedling infection was made manifest by root lesions and runner hyphae, but these symptoms were not always plain or conclusive. Many seedling roots that rotted when kept moist and in the light produced perithecia within 6 weeks. Although perithecia formed on some roots where neither lesions nor hyphae were found, they did not form on all diseased roots. More needs to be known about the factors influencing perithecial formation before it can be used as a reliable confirmatory test.     

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.     

Experiments using sterilized apple-leaf discs to study the mode of action of urea in suppressing perithecia of Venturia inaequalis (Cke.) Wint.

Laboratory experiments using sterilized apple-leaf discs showed that treatment of leaves with urea during the early stages of perithecial initiation induced a high nitrogen content of the leaves, which prevented further development of perithecia although mycelial growth was unaffected. Treatments applied at a later stage of fungal development inhibited both perithecial and mycelial growth. Some of the bacteria isolated from urea-treated leaves in the field restricted perithecial development, particularly when applied in the first month after inoculation with suspensions of conidia from sexually compatible strains of the fungus. One isolate, a Pseudomonas sp., was shown to be important in the decomposition of apple leaves.     

EFFECT OF TEMPERATURE,LIGHT AND pH ON GROWTH,PHOTOSYNTHESIS AND RESPIRATION OF THE DINOFLAGELLATE PERIDINIUM CINCTUM FA. WESTII IN LABORATORY CULTURES1

Optimum light, temperature, and pH conditions for growth, photosynthetic, and respiratory activities of Peridinium cinctum fa. westii (Lemm.) Lef were investigated by using axenic clones in batch cultures. The results are discussed and compared with data from Lake Kinneret (Israel) where it produces heavy blooms in spring. Highest biomass development and growth rates occurred at ca. 23° C and ≥50 μE· m^?2·s¹ of fluorescent light with energy peaks at 440–575 and 665 nm. Photosynthetic oxygen release was more efficient in filtered light of blue (BG 12) and red (RG 2) than in green (VG 9) qualities. Photosynthetic oxygen production occurred at temperatures ranging from 5° to 32° C in white fluorescent light from 10 to 105 μE·m^?2·s^?1 with a gross maximum value of 1500 × 10^?12 g·cell^?1·h^?1 at the highest irradiance. The average respiration amounted to ca. 12% of the gross production and reached a maximum value of ca. 270·10^?12 g·cell^?1·h^?1 at 31° C. A comparison of photosynthetic and respiratory Q₁₀-values showed that in the upper temperature range the increase in gross production was only a third of the corresponding increase in respiration, although the gross production was at maximum. Short intermittent periods of dark (>7 min) before high light exposures from a halogen lamp greatly increased oxygen production. Depending on the physiological status of the alga, light saturation values were reached at 500–1000 μE·m^?2·s^?1 of halogen light with compensation points at 20–40 μE·m^?2·s^?1 and I_k-values at 100–200 μE·m^?2·s^?1. The corresponding values in fluorescent light in which it was cultured and adapted, were 25 to 75% lower indicating the ability of the alga to efficiently utilize varying light conditions, if the adaptation time is sufficient. Carbon fixation was most efficient at ca. pH 7, but the growth rates and biomass development were highest at pH 8.3.     

Phenotypic Diversity among Alleles at the PER-1 Locus of NEUROSPORA CRASSA

Comparison of 11 perithecial color mutants suggested that all were alleles at the per-1 locus but nonetheless separable into two groups because of phenotypic differences. Three of the mutant strains produced orange perithecia and black ascospores, and eight produced paler, yellow perithecia and white ascospores. Perithecial phenotype was dependent upon the genotype of the protoperithecial parent; ascospore phenotype, upon the genotype of the individual ascospore. No evidence was found that the white ascospores were due to chromosomal rearrangements. No separation of the perithecial and ascospore phenotypes by recombination was observed in a cross between one of the mutants and a per-1+ strain. However, apparent low levels of recombination in crosses between some of the mutants indicated possible genetic complexity at the per-1 locus. The phase specificity of the per-1 mutations and the possible nature and mode of expression of the orange and yellow perithecial pigments are 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。     

Effect of Trichoderma harzianum on perithecial production of Gibberella zeae on wheat straw

Conidial suspensions and cell-free filtrates of Trichoderma harzianum isolates were evaluated for their effectiveness in reducing perithecial and ascospore production of Gibberella zeae on wheat straw. Isolate T-22, which is registered in the US as a biological control agent (Plant Shield™), was included in the study as a positive control. When co-inoculated with G. zeae all 11 isolates of T. harzianum significantly reduced perithecial numbers on wheat straw. Five T. harzianum isolates, including T-22, reduced perithecial formation by 70% or greater. All isolates of G. zeae, varied in their ability to produce perithecia. Isolate 192132 produced the greatest number of perithecia and was used to further evaluate the effect of application time of the T. harzianum isolates. Perithecial reduction was highest (96-99%) when T. harzianum conidial suspension or cell-free filtrate was applied to straw 24 h prior to inoculation with G. zeae. Control was less effective when T. harzianum was applied at the same time (co-inoculated) or 24 h after G. zeae. Treatments which reduced perithecial numbers also reduced ascospore numbers; however, the average numbers of ascospores per perithecia were not significantly lowered. Field trials showed significant reduction of perithecia on residues treated with T. harzianum prior to placement on the soil surface. Both T. harzianum and G. zeae were re-isolated from residues sampled in July and August after 30 and 60 days of exposure to the environment.     

Perithecial Formation in Gelasinospora reticulispora VII: Action Spectra in UV Region for the Photoinduction and the Photoinhibition of Photoinductive Effect Brought by Blue Light

An action spectrum for photoinduction of perithecial formationafter a prior 72 h dark growth period was determined in theUV region with apically growing mycelia of a sordariaceous fungus,Gelasinospora reticulispora. The spectrum exhibited a peak at280 nm. Quantum effectiveness of 280 nm irradiation was ca.1.7 times higher than that of 450 nm light. The number of peritheciainduced by UV radiation was saturated at a lower level as comparedwith blue light. UV radiation having a fluence greater thanthe saturation level decreased the number of induced perithecia.UV radiation that was given after a saturating exposure to inductiveblue light inhibited the inductive effect of blue light. Anaction spectrum for this inhibition exhibited a peak between260 and 270 nm. Monochromatic light beyond 350 nm had no inhibitoryeffect. Inhibitory effects of UV radiation given after inductiveblue light irradiation were observed in the fluence range wherephotoinductive effects of UV radiation became obvious. Therefore,the true height of the UV peak in the photoinduction actionspectrum,when free of distortion from the inhibitory effect, should behigher than the peak obtained in this study. (Received August 20, 1983; Accepted November 4, 1983)     

Action Spectrum of the Photoinduced Sexual Stage in the Fungus Nectria haematococca Berk. and Br. var cucurbitae (Snyder and Hansen) Dingley

An action spectrum was determined for the photoinduced formation of perithecia in a homothallic strain of Nectria haematococca Berk. and Br. var. cucurbitae (Snyder and Hansen) Dingley. Dose-response curves for perithecial formation were obtained from 340 to 510 nanometers at 10-nanometer intervals. Radiation longer than 510 nanometers was not effective for inducing perithecial formation. The action spectrum indicated peaks of activity near 360, 440, and 480 nanometers with shoulders near 420 and 460 nanometers. Minima occurred near 350 nanometers, 390 to 410 nanometers, and 470 nanometers. The general shape of this action spectrum appears to be similar to those obtained for many different near ultraviolet-blue-sensitive organisms in which a flavoprotein molecule was postulated to be the photoreceptor.     

Perithecium morphogenesis in Sordaria macrospora

The perithecium of the self-fertile ascomycete Sordaria macrospora provides an excellent model in which to analyse fungal multicellular development. This study provides a detailed analysis of perithecium morphogenesis in the wild type and eight developmental mutants of S. macrospora, using a range of correlative microscopical techniques. Fundamentally, perithecia and other complex multicellular structures produced by fungi arise by hyphal aggregation and adhesion, and these processes are followed by specialization and septation of hyphal compartments within the aggregates. Perithecial morphogenesis can be divided into the ascogonial, protoperithecial, and perithecial stages of development. At least 13 specialized, morphologically distinct cell-types are involved in perithecium morphogenesis, and these fall into three basic classes: hyphae, conglutinate cells and spores. Conglutinate cells arise from hyphal adhesion and certain perithecial hyphae develop from conglutinate cells. Various hypha-conglutinate cell transitions play important roles during the development of the perithecial wall and neck.     

Perithecial formation in Gelasinospora reticulispora II. Promotive effects of near-ultraviolet and blue light after dark incubation

Hyphae of Gelasinospora reticulispora growing on corn meal agarat 25?C required light of form perithecia. This response tolight was highly correlated to the length of the preliminarydark period, i.e. the photoinduction of perithecia never occurredin cultures grown in the dark for periods of 27 hr or less,whereas hyphae became photosensitive if incubated for 30 hror longer in the dark. The perithecia became simultaneouslyvisible with the 30 to 48 hr dark-grown hyphae irrespectiveof the different dark periods, but time courses for cultureshaving 54 hr or longer of darkness were dependent upon the timewhen light was given. Light induced perithecia only in the dark-grown portions ofthe hyphae. The longer the dark period, the more the sensitivityto light increased when the most effective range of wavelenghtswas shifted from near-ultraviolet to blue. Light of green andlonger wavelenghts was not at all effective irrespective ofthe duration of darkness. The photoinduced stimulus was notmovable from the irradiated to the unirradiated portions. (Received August 3, 1973; )     

Field and laboratory studies of the effect of urea on ascospore production of Venturia inaequalis (Cke.) Wint

Applications of urea after harvest but before leaf-fall restricted perithecial production by Venturia inaequalis. Immersion of detached leaves in urea appeared to be the most effective method of preventing perithecial formation, although spraying attached leaves was equally effective when leaf abscission occurred within a week of treatment. A high nitrogen content within the leaf was one of the major factors contributing to suppression. Urea-treated leaves decomposed rapidly, thus destroying the overwintering substrate for the fungus. When apple plants (clone M. 111) were sprayed in autumn with 5 % urea, followed by a second (pre-bud-burst) application at 2 %, ascospore production in the spring was suppressed. The second treatment appeared to prevent the release of ascospores from mature perithecia.     

RESPONSE OF PROROCENTRUM MARIAE-LEBOURIAE (DINOPHYCEAE) TO LIGHT OF DIFFERENT SPECTRAL QUALITIES AND IRRADIANCES: GROWTH AND PIGMENTATION1

Growth and pigment concentrations of the, estuarine dinoflagellate, Prorocentrum mariae-lebouriae (Parke and Ballantine) comb. nov., were measured in cultures grown in white, blue, green and red radiation at three different irradiances. White irradiances (400–800 nm) were 13.4, 4.0 and 1.8 W · m^?2 with photon flux densities of 58.7 ± 3.5, 17.4 ± 0.6 and 7.8 ± 0.3 μM quanta · m^?2· s^?1, respectively. All other spectral qualities had the same photon flux densities. Concentrations of chlorophyll a and chlorophyll c were inversely related to irradiance. A decrease of 7- to 8-fold in photon flux density resulted in a 2-fold increase in chlorophyll a and c and a 1.6- to 2.4-fold increase in both peridinin and total carotenoid concentrations. Cells grown in green light contained 22 to 32% more peridinin per cell and exhibited 10 to 16% higher peridinin to chlorophyll a ratios than cells grown in white light. Growth decreased as a function of irradiance in white, green and red light grown cells but was the same at all blue light irradiances. Maximum growth rates occurred at 8 μM quanta · m^?2· s^?1 in blue light, while in red and white light maximum growth rates occurred at considerably higher photon flux densities (24 to 32 μM quanta · m^?2· s^?1). The fastest growth rates occurred in blue and red radiation. White radiation producing maximum growth was only as effective as red and blue light when the photon flux density in either the red or blue portion of the white light spectrum was equivalent to that of a red or of blue light treatment which produced maximum growth rates. These differences in growth and pigmentation indicate that P. mariae-lebouriae responds to the spectral quality under which it is grown.     

Relations entre production et localisation de mycosporine et morphogenèses reproductrices chez le Pyrénomycète Gnomonia leptostyla

Relations between production and localisation of mycosporin and reproductive morphogenesis in the Pyrenomycete Gnomonia leptostyla.
The production of mycosporin (P310) has been analysed in Gnomonia leptostyla (FT.) Ces. et de Not. during mycelial growth and reproductive morphogenesis (macroconidiogenesis, microconidiogenesis and differentiation of perithecia). Conidiogenesis is induced in illuminated cultures while darkness promotes perithecial development. At 20°C, the cultures produce either macroconidia or perithecia with abortive sporophyte. Microconidia differentiation and perithecia maturation require low temperature (10°C). Mycosporin is, at all times, present in the thallus. However, the concentration of mycosporin in highest in the conidiogenous thallus, intermediate in the perithecial thallus. and lowest in the vegetative mycelium. In the conidiogenous thallus, macroconidia and microconidia are both sites of mycosporin accumulation. On the contrary, in the perithecial thallus, mycosporin levels are not higher in perithecia than in mycelia, even during their maturation period. The quantitative variations of mycosporin during the thallus development and its accumulation inside conidia suggest translocation from sites of synthesis towards reproductive cells.