Grass seed infection following inundation with Pyrenophora semeniperda

Seed infection by the seed-borne pathogen Pyrenophora semeniperda was demonstrated following inundative applications of the fungus to several annual grass weeds and wheat. The optimum time for applying inoculum was found to be around mid-anthesis in wheat. Applications of inoculum during and after anthesis in field experiments resulted in seed infection that manifested as stromatal development which affected germination or reduced seedling vigour. In an initial field experiment, >70% of Bromus diandrus seeds exhibited stromata of P. semeniperda. In a field comparison of inoculum types, conidial suspensions resulted in the greatest level of seed infection of B. diandrus compared with several types of inoculum containing mycelium fragments. Inundation of Avena fatua, Lolium rigidum, Hordeum leporinum, Vulpia bromoides and B. diandrus under field conditions with conidia of P. semeniperda also resulted in either the failure of infected seeds to germinate or a reduction of seedling vigour. It is concluded that the use of P. semeniperda as a seed-borne bioherbicide may be a biologically reasonable tactic, and the many logistical and technological constraints impeding its development are discussed.     

Celery leaf spot: sources of inoculum

The relative importance of infected celery seed, infected leaf debris in the soil, and infected wild celery, in the incidence of Septoria leaf spot in cultivated celery has been investigated. Infection can be caused when the sole source of inoculum is viable spores on the seed surface; such spores are considered to be the main cause of disease outbreaks. Of all the seed samples examined, 93% were infected by Septoria spp. In untreated seed samples, 40% carried viable spores which survived for up to 15 months on seed stored in the laboratory, and for longer periods on seed stored at -20d? C. However, ageing of seed is not recommended as a commercial control measure. The fungus was not found in seed embryos or endosperms but mycelium was present in pericarps and testas. Unconfirmed evidence suggests that in favourable circumstances new spores might be produced in old seed-borne pycnidia.     

Effect ofAspergillus parasiticus soil inoculum on invasion of peanut seeds

Environmental control plots adjusted to late season drought and elevated soil temperatures where inoculated at peanut planting with low and high levels of conidia, sclerotia, and mycelium from a brown conidial mutant ofAspergillus parasiticus. Percentage infection of peanut seeds from undamaged pods was greatest for the subplot containing the high sclerotial inoculum (15/cm² soil surface). Sclerotia did not germinate sporogenically and may have invaded seeds through mycelium. In contrast, the mycelial inoculum (colonized peanut seed particles) released large numbers of conidia into soil. Soil conidial populations of brownA. parasiticus from treatments with conidia and mycelium were positively correlated with the incidence of seed infection in undamaged pods. The ratio ofA. flavus to wild-typeA. parasiticus in soil shifted from 7:3 to 1:1 in the uninoculated subplot after instigation of drought, whereas in all subplots treated with brownA. parasiticus, the ratio of the two species became approximately 8:2. Despite high levels of brownA. parasiticus populations in soil, nativeA. flavus often dominated peanut seeds, suggesting that it is a more aggressive species. Sclerotia of wild-typeA. parasiticus formed infrequently on preharvest peanut seeds from insect-damaged pods.     

Chlamydospores of Schizophyllum commune

Summary The detection of chlamydospores of Schizophyllum commune in liquid medium is described. The short thick walled cells are formed by intercalary septation which leads also to modification of the septal complex. The chemical composition of the cell walls of chlamydospores is similar to the composition of the vegetative mycelium.     

A rapid technique for evaluating the biodeterioration potential of polyurethane elastomers

Summary The technique described provides a rapid method for screening thermoplastic polyurethanes against deteriogenic micro-organisms using thin films (0.4–0.5 mm thick) of plastic prepared in an electric plantens press. The films are inoculated with a spore suspension of Gliocladium roseum and can be viewed directly under the light microscope for evaluation of surface effects; selective staining can be used to reveal fungal mycelium. Results can be obtained within a week which correlate with longer term tests using commercial samples. The technique can also be used to isolate potential polyurethane deteriorating micro-organisms from the environment and to confirm their biodeteriogenic activities.     

Effects of initial inoculation density of Paenibacillus polymyxa on colony formation and starch‐hydrolytic activity in relation to root rot in ginseng

Aims: To examine the relationships between population growth and biological characters of the plant‐growth‐promoting rhizobacterium Paenibacillus polymyxa GBR‐1. Methods and Results: Population growth, colony formation, starch‐hydrolytic activity, and ginseng root rot caused by P. polymyxa GBR‐1 isolated from a rotten ginseng root were examined in vitro and in vivo at high [1 × 10⁸ colony‐forming units (CFU) ml^?1] and low (1 × 10⁶ CFU ml^?1) initial inoculum densities. Paenibacillus polymyxa GBR‐1 showed strong starch‐hydrolytic activity on modified starch agar with relatively low starch content, but only at certain incubation temperatures (18 and 23°C); the high‐density inoculum produced bacterial colonies about nine times thicker than those formed from the lower inoculum density. Light, scanning electron, and transmission electron microscopy showed that the thick colonies from the high‐density inoculum were filled with extracellular polymeric substances (EPS), in which a relatively small number of ovoid‐rod‐shaped bacterial cells (mostly endospore‐bearing cells) were distributed. In contrast, the thin colonies from the low‐density inoculum were composed of massive vegetative cells with a rectangular rod shape and minimum EPS. Fluorescent in situ hybridization (FISH) revealed that the β‐amylase gene was expressed only in bacterial cells from the thick colonies formed from the high‐density inoculum, but not in those from the low‐density inoculum. The culture filtrate from the thick colonies produced a hydrolytic clear zone on modified starch agar, degraded starch granules in various manners, and produced rot symptoms on ginseng root tissues. Conclusions: The biological properties of colony formation, starch hydrolysis, and ginseng tissue rotting by P. polymyxa GBR‐1 are interrelated; they are influenced by the initial bacterial population density but not by the in situ and the final population densities. Significance and Impact of the Study: Knowledge of disease‐inducing characters of P. polymyxa GBR‐1 can be used in the development of biocontrol strategies.     

Reclassification of Pichia membranifaciens sensu Kurtzman

Forty strains which were stocked as Pichia membranifaciens sensu Kurtzman and 9 strains stocked as Candida valida, anamorphs of P. membranifaciens, in the Institute for Fermentation, Osaka (IFO) were reclassified based on the data of base composition of nuclear DNA, DNA/DNA hybridization, coenzyme Q system, electrophoretic karyotype, and base sequence of 18S rDNA. P. membranifaciens complex was assigned into 3 groups: (I) P. membranifaciens group, including 25 strains with high DNA homologies to the type strain of P. membranifaciens (72–98%); (II) P. manshurica group, including 18 strains with high DNA homology of 79–95% to the type strain of P. manshurica; and a group including the remaining 6 strains, which had low DNA homology to the above two species. GC content was 42.9–45.3 mol% for the P. membranifaciens group, 40.0–42.0 mol% for the P. manshurica group, and 27.2–44.7 mol% for the remaining group. All three groups had ubiquinone Co Q-7. Of the 6 anomalous strains, IFO 0162 was identified as Pichia deserticola, and IFO 0839 and IFO 0840 were identified as Issatchenkia occidentalis; but IFO 0842, IFO 0843, and IFO 1788 were thought to be unknown strains.     

Internal mycelium of Pseudoperonospora cubensis, the causal agent of cucurbit downy mildew

The internal mycelium of Pseudoperonospora cubensis has been observed in transmission and scanning electron microscopic preparations. The internal mycelium may be inter- or intracellular. Haustoria of short swollen bundles of hyphae have been observed. Actively growing hyphae contain numerous mitochondria, nuclei, active dictyosomes, low amounts of storage materials (lipid) and microbody-like structures with a laminate inclusion. Thick walled hyphae with a diameter which is smaller than the actively growing hyphae have been observed. These thick wallcd hyphae contain large amounts of reserve material (lipid) and it is suggested that they may function as resting propagules.     

Development of ovule,fruit and seed of Xyris (Xyridaceae,Poales) and taxonomic considerations

The development of the ovule, fruit and seed of Xyris spp. was studied to assess the embryological characteristics of potential taxonomic usefulness. All of the studied species have (1) orthotropous, bitegmic and tenuinucellate ovules, with a micropyle formed by both the endostoma and exostoma; (2) a cuticle in the ovules and seeds between the nucellus/endosperm and the inner integument and between the inner and outer integuments; (3) helobial, starchy endosperm; (4) a reduced, campanulate and undifferentiated embryo; (5) a seed coat formed by a tanniferous endotegmen, endotesta with thick‐walled cells and exotesta with thin‐walled cells; and (6) a micropylar operculum formed from inner and outer integuments. The pericarp is composed of a mesocarp with cells containing starch grains and an endocarp and exocarp formed by cells with U‐shaped thickened walls. The studied species differ in the embryo sac development, which can be of the Polygonum or Allium type, and in the pericarp, which can have larger cells in either endocarp or exocarp. The Allium‐type embryo sac development was observed only in Xyris spp. within Xyridaceae. Xyris also differs from the other genera of Xyridaceae by the presence of orthotropous ovules and a seed coat formed by endotegmen, endotesta and exotesta, in agreement with the division of the family into Xyridoideae and Abolbodoideae. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 619–628.     

The survival on chrysanthemum roots of epiphytic mycelium of Mycosphaerella ligulicola

Mycosphaerella ligulicola has been shown to survive as epiphytic mycelium on the root surface of chrysanthemum cuttings: such survival could continue throughout the life of the glasshouse crop. Symptomless surface colonization of roots of cuttings could be induced in non-sterile soil from an inoculum of (a) mycelium and sclerotia or (b) conidia (Ascochyta state); the colonization could spread upwards over the root surface. After 12 weeks survival as an epiphyte on chrysanthemum roots the fungus was still pathogenic to unrooted cuttings. Although the root surfaces of twelve other plants could be colonized by M. ligulicola the fungus survived on these roots for not more than 8 weeks.     

Survival of inoculum of the leaf blight fungus Phytophthora colocasiae infecting taro, Colocasia esculenta in the Solomon Islands

Phytophthora colocasiae was successfully isolated by baiting with detergent-treated taro leaf discs 8 cm diameter placed on water slurries of soil, on suspensions of macerated infected leaf lesions or on the washings from petioles of harvested plants. Taro root tips, detached or left on corms, were not susceptible to zoospores of P. colocasiae nor were detached root tips of Lupinus angustifolius. Cubes of taro corm used as baits, and agar selective for Phycomycetes which was inoculated directly with soil, both became too heavily overrun by Phythium splendens to allow detection of P. colocasiae. Investigations indicated that inoculum on lesions of detached leaves and in soil remains viable for only a few days. Petiole bases which comprise the bulk of the ‘tops’ used for vegetative propagation, lost detectable natural inoculum rapidly (2 days) if stored dry, but less rapidly (14 days) if planted immediately in the field. Artifically augmenting surface inoculum with naturally produced sporangia considerably extended the periods of detectability, probably by increasing the chances that a few propagules would survive, especially during dry storage. Incubation of inoculated tops in high humidity led to active infection and sporulation on petioles, especially on cut ends, a situation that might be paralleled under suitable moisture conditions in the field. Of several aroid species tested by artificial inoculation only Alocasia macrorrhiza was susceptible. Natural infection of this plant has not been seen, making it an unlikely alternate host of P. colocasiae under field conditions. Thus perennation between taro crops is effected by shortlived surface propagules and possibly also by mycelium within lesions on petioles. Reduction of the former and prevention of the latter might be achieved by dry storage of tops for 2 to 3 wk.     

Fruit structure of Amborella trichopoda (Amborellaceae)

The indehiscent fruitlets of the apparently basalmost extant angiosperm, Amborella trichopoda, have a pericarp that is differentiated into five zones, a thin one‐cell‐layered skin (exocarp), a thick fleshy zone of 25–35 cell layers (outer mesocarp), a thick, large‐celled sclerenchymatous zone (unlignified) of 6–18 cell layers (middle mesocarp), a single cell layer with thin‐walled (silicified?) cells (inner mesocarp), and a 2–4‐cell‐layered, small‐celled sclerenchymatous zone (unlignified) derived from the inner epidermis (endocarp). The border between inner and outer mesocarp is not even but the inner mesocarp forms a network of ridges and pits; the ridges support the vascular bundles, which are situated in the outer mesocarp. In accordance with previous observations by Bailey & Swamy, no ethereal oil cells were observed in the pericarp; however, lysigenous cavities as mentioned by these authors are also lacking; they seem to be an artefact caused by re‐expanding dried fruits. The seed coat is not sclerified. The fruitlets of Amborella differ from externally similar fruits or fruitlets in other basal angiosperms, such as Austrobaileyales or Laurales, in their histology. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 148 , 265–274.     

Stilbella aciculosa: A Potential Biocontrol Fungus against Rhizoctonia solani

A semi‐solid fermentation product of the potential biocontrol fungus Stilbella aciculosa was formulated on wheat bran: water (1:1, w/w) and incubated 5, 10 and 15 days before addition to soil infested with the pathogen Rhizoctonia solani. Generally, preparations did not reduce survival of the pathogen in infested beet seed but they did prevent saprophytic growth of the pathogen from beet seed into soil. The magnitude of reduction by the 15‐day‐old inoculum was greater than that by the 5‐day‐old inoculum. Ten‐day‐old bran preparations of S. aciculosa at rates of 0.5 and 1.0% (w/w) in soil prevented post‐emergence damping‐off of cotton, radish and sugar beet in the glasshouse and a rate of 1.0% gave stands similar to those in the non‐infested control soil. The antagonist, grown on perlite formulated with molasses, cornmeal, alfalfa tissue or corn stover, prevented damping‐off of cotton in a naturally infested soil. However, the stands were not as great as that in soil planted with pentachloronitrobenzene (PCNB)‐treated seed. Toxic metabolites, produced by S. aciculosa developing on various substrates, slightly inhibited the growth of R. solani in culture and induced cytoplasmic leakage of the pathogen mycelium.     

Transfer of Alternaria macrospora from Cotton Seed to Seedling: Light and Scanning Electron Microscopy of Colonization

Alternaria macrospora is transferred from an infected seed, through the plant stem to the cotyledon and sporulates on its surface. However, at the beginning of the process, there is no difference between resistant and susceptible plants. In later stages, lower levels of fungal mycelium and sporulation were detected on the seedlings of a resistant cultivar. The fungus grew inside the plant from the underground to the upper parts. The mycelia which originated from surface spores could penetrate, through stomata and result in leaf colonization. A. macrospora sporulated ultimately on plant surfaces whereas the internal leaf tissue was colonized by mycelium only. This study suggests that cotyledon infection is a result of seed infection.     

Tricholoma matsutake– an assessment of in situ and in vitro infection by observing cleared and stained whole roots

 Structures present within field-collected Tricholoma matsutake/Pinus densiflora ectomycorrhizas and in vitro infections of P. densiflora roots by T. matsutake were observed by clearing, bleaching and staining whole lateral roots and mycorrhizas. Field mycorrhizas were characterized by a lack of root hairs, by the presence of a sparse discontinuous mantle composed of irregularly darkly staining hyphae over the root surface, primarily behind the root cap, and by the presence of Hartig net mycelium within the root cortex. Hartig net 'palmettis' were classified into three basic structures, each with distinctive morphologies. Aerial hyphae, bearing terminal swellings, were observed emanating from the mantle. Cleared, bleached and stained in vitro-infected roots possessed multibranched hyphal structures within the host root cortex and aerial hyphae bearing terminal swellings were observed arising from the mycelium colonizing the root surface. T. matsutake on P. densiflora conforms to the accepted morphology of an ectomycorrhiza. This staining protocol is particularly suited to the study of Matsutake mycorrhizal roots and gives rapid, clear, high-contrast images using standard light microscopy while conserving spatial relationships between hyphal elements and host tissues. Accepted: 26 August 1999     

The role of seed-tuber and stem inoculum in the development of gangrene in potatoes

To determine the relative importance of seed tubers and stems as sources of inoculum for potato gangrene in progeny tubers, different levels of inoculum of Phoma exigua var. foveata were established in field experiments by planting rotting or contaminated seed tubers and by inoculating stems shortly before haulm desiccation. The pathogen was only occasionally detected by isolation from inside green stems in June and July on plants growing from contaminated but unrotted seed. The incidence of pycnidia on desiccated stems increased with increasing concentration of inoculum contaminating seed tubers and with increasing time interval between desiccation and harvest. Stem infection was probably derived from inoculum on seed tubers spreading via the soil to the stem bases. Stem inoculation of plants growing from uninoculated or uncontaminated seed greatly increased both the gangrene potential of progeny tubers (defined as % wounds with gangrene after uniformly damaging tubers and storing them at 5°C for 12 wk), and tuber contamination (defined as % wounds with gangrene after spreading tuber-borne soil onto test tuber slices and storing them at 5°C for 8 wk). However, when stems of plants growing from rotting or contaminated seed were cut at ground level and removed before desiccation, gangrene potential of progeny tubers was only slightly less than that of tubers from untreated plots. There was no evidence that soil inoculum or aerial spread played a significant role in disease development. Gangrene potential and contamination of progeny tubers were related to Contamination levels on seed tubers. Some transmission also occurred from rotted seed tubers to progeny. Inoculum levels around progeny tubers increased rapidly after desiccation even in plots where stems had previously been cut at soil level and removed to eliminate pycnidial development above ground as a source of inoculum. Both gangrene potential and contamination of progeny tubers were greater on cv. Ulster Sceptre than on cv. Pentland Crown. The results showed that the inoculum on seed tubers, whether from rots or surface contamination, contributed more to the contamination of progeny tubers at harvest than did the inoculum from pycnidia on stems following desiccation of the haulm.     

Effect of aromatic plant species on vesicular-arbuscular mycorrhizal establishment in Pistacia terebinthus

The inoculation of Pistacia terebinthus with vesicular-arbuscular mycorrhizal (VAM) fungi and the spread of the infection were studied using a mixed cropping system, under glasshouse conditions, with Salvia officinalis, Lavandula officinalis and Thymus vulgaris colonized by Glomus mosseae as an inoculation method. This method was compared with soil inoculum placed under the seed or distributed evenly in the soil. Indirect inoculation with all the aromatic plants tested significantly increased VAM root colonization of P. terebinthus compared with the use of soil inoculum, although the effect on plant growth was different for each one of the aromatic species used as inoculum source. Inoculation with L. officinalis and T. vulgaris were the best treatments resulting in high VAM colonization and growth enhancement of P. terebinthus.     

Effects of phosphate fertilization,lime amendments and inoculation with VA-mycorrhizal fungi on soybeans in an acid soil

Soybeans [Glycine max (L.) Merr. cv. Essex] were grown in nonsterile acid (pH. 5.2) infertile Wynnville silt loam (Glossic Fragiudult) in a glasshouse. The effects of P fertilization and lime were determined by inoculation with two VAM-fungi (VAMF): Glomus fasciculatum (Gf) and Glomus etunicatum (Ge). An important factor affected by the interaction between applied lime (soil acidity), applied P, and VAMF inoculation was the soil Al. Five application rates of P as KH₂PO₄ and three rates of lime were tested. Potassium was equalized with KCl (muriate of potash). P-efficiency (g seed/mg P kg^-1 soil) by vesicular-arbuscular mycorrhiza (VAM) was maximal at 20 mg P kg^-1 soil at all lime and VAMF treatments. VAMF inoculation increased plant survival and protected the soybeans from leaf scorch, thereby substituting for the effects of lime and P. The Ge inoculum was superior in ameliorating leaf scorch in the nonlimed soil. The Gf inoculum required more lime and P than the Ge inoculum to increase seed yield relative to the noninoculated controls containing only native VAMF. Both inocula increased root Al uptake and extractable soil Al in the acid soil without apparent adverse effects on root or shoot. The ability of the VAMF inocula to enhance the efficiency of applied P and decrease seed Cl concentration was increased by lime. Seed yield (Y) was negatively related to seed Cl concentration (X) where Y=aX^-b. Both VAMF inoculation and lime application reduced this negative relationship and may have increased the tolerance to both Cl and soil Al.     

Triton X-100 in Giemsa Staining of Blood Parasites

The effects of a surface active agent, Triton X-100, were studied in the routine Giemsa staining of seven blood parasites: Plasmodium vivax, Trypanosoma cruzi, T. lewisi, Leishmania donovani, Toxoplasma gondii, and microfilariae of Dirofilaria immitis and of Wuchereria bancrofti. Concentrations of Triton X-100 ranging from 0.01% to 0.5% were used in staining (a) both thick and thin blood films of all organisms except L. donovani, (b) tissue smears of L. donovani, and (c) tissue and peritoneal fluid smears of T. gondii. In general, the addition of the detergent to the Giemsa solution resulted in cleaner preparations and better stained organisms. Morphological details were more distinct, thus facilitating microscopical detection and identification of species. The most beneficial concentration of Triton X-100 was found to be 0.1%. Since it has a hemolytic effect on erythrocytes, concentrations above 0.01% cannot be used in staining thin blood films. It is suggested also that the use of Triton-Giemsa may help prevent transfer of some of these organisms from one slide to another during mass staining procedures as it has been demonstrated to do with malaria parasites (Brooke and Donaldson, 1950).