Ultrastructure of virus-like particles in Plasmopara halstedii

1992 ◽  
Vol 70 (2) ◽  
pp. 334-339 ◽  
Author(s):  
T. J. Gulya ◽  
T. P. Freeman ◽  
D. E. Mayhew
Keyword(s):  
Downy Mildew ◽  
Systemic Infection ◽  
Fungal Mycelium ◽  
Thin Sections ◽  
Plasmopara Halstedii ◽  
Double Stranded Rna ◽  
Virus Like Particles ◽  
Virus Like Particle ◽  
Membrane Bound ◽  
Race 2

Virus-like particles were observed in five North Dakota isolates of Plasmopara halstedii race 2, the causal agent of sunflower downy mildew. Virus-like particles were observed in fungal mycelium within sunflower seedlings showing typical symptoms of systemic infection as well as from seedlings displaying "twisted leaf syndrome." Virus-like particles were never observed in sunflower cells. The particles were isometric in shape and measured 23–26 nm in thin sections and 32 nm after phosphotungstic acid staining. Virus-like particles occurred dispersed throughout the cytoplasm and in membrane-bound organelles. Both crystalline and noncrystalline arrays were common. The particles were observed in haustoria, intercellular hypha, sporangiophores, zoosporangia, and oospores. Four species of double-stranded RNA were detected in sunflower tissue infected with P. halstedii; none were detected in healthy sunflower tissue. This is only the second report of an isometric, virus-like particle occurring in a member of the Peronosporales. Key words: mycovirus, downy mildew, Helianthus annuus.

scholarly journals DISTRIBUTION AND RACE COMPOSITION OF DOWNY MILDEW (Plasmopara halstedii (Farl.) Berl. and de Toni) IN BULGARIA / EXTENSION Y RAZAS DEL MILDIU (Plasmopara halstedii (Farl.) Berl. y de Toni) EN BULGARIA / ÉTENDUE ET RACES DE LA ROUILLE (Plasmopara halstedii (Farl.) Berl. and de Toni) EN BULGARIE

Helia ◽  
2000 ◽  
Vol 23 (33) ◽  
pp. 25-32
Author(s):  
P.S. Shindrova
Keyword(s):  
Downy Mildew ◽  
Resistance Gene ◽  
The Other ◽  
Plasmopara Halstedii ◽  
North West ◽  
North East ◽  
Race 1 ◽  
Race 2 ◽  
Production Areas ◽  
Number Of Authors

SUMMARY Downy mildew caused by the fungus Plasmopara halstedii is the main disease on sunflower in Bulgaria. In recent years a number of authors have reported the occurrence of new more virulent races of the pathogen. According to other authors these races demonstrate resistance to the fungicides used up to now. This fact is rather alarming and imposes the necessity of annual researches with the aim of following the changes in the downy mildew race variability. In the period 1995-1997 downy mildew isolates were collected from the following locations: Bourgas, Boyanovo, Karnobat, Ognyanovo, Selanovtsi, Kroushari, Lovech, Koubrat, Brashlyan, Sitovo, Tervel, Targovishte, IWS “Dobroudja” and Dobrich. The samples were assessed for virulence on a set of sunflower differential - lines under greenhouse conditions. The obtained results do not reveal a great race variability of downy mildew population in Bulgaria. In the period of study two races of the pathogen were identified: race 1 which infects the differential lines without genes for resistance to the pathogen. It is distributed in all sunflower production areas of the country. The other one is race 2. It is of limited distribution and has been registered in individual fields of north-east and north-west Bulgaria. It attacks the differential lines carrying the resistance gene Pl-1.

Early stages of infection of resistant and susceptible sunflower seedlings by three races of Plasmopara halstedii

1985 ◽  
Vol 63 (10) ◽  
pp. 1725-1729 ◽  
Author(s):  
A. Bruce Gray ◽  
W. E. Sackston
Keyword(s):  
Helianthus Annuus ◽  
Downy Mildew ◽  
Hypersensitive Reaction ◽  
Red River ◽  
Plasmopara Halstedii ◽  
Helianthus Annuus L ◽  
Red River Valley ◽  
European Race ◽  
Race 2 ◽  
Germ Tubes

Resistance in sunflower (Helianthus annuus L.) to downy mildew (Plasmopara halstedii (Farl.) Berl. et de Toni) is conditioned by a series of Pl. genes. Races 1 (European race), 2 (Red River race), and 3 (a new North American race encountered in the Red River valley in 1980) formed similar infection structures on inoculated seedlings whether susceptible or resistant to races 1 and 2; all cultivars tested were susceptible to race 3. The zoospores encysted and produced germ tubes and appressoria on the roots and hypocotyls. Penetration occurred and mycelium and haustoria developed in both compatible and incompatible host–pathogen combinations. Resistance did not appear to involve a hypersensitive reaction occurring prior to penetration.

Ultrastructure of Plasmopara halstedii containing virus-like particles

1991 ◽  
Vol 49 ◽  
pp. 216-217
Author(s):  
Thomas Freeman ◽  
Thomas Gulya
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Helianthus Annuus ◽  
Downy Mildew ◽  
Systemic Disease ◽  
Disease Symptoms ◽  
Plasmopara Halstedii ◽  
Transmission Electron ◽  
Race 2 ◽  
Standard Techniques

Mycoviruses have been found in more than 100 species of fungi and it is estimated that they may occur in as many as 500 species (Buck, 1986; Hollings, 1978; and Lemke, 1981). Mycoviruses range in size from small, isometric particles (25 nm in diameter) to long, flexuous rods exceeding 2000 nm in length, with the majority being isometric particles ranging in size from 25-50 nm (Buck, 1986). Mycoviruses hae been reported in all groups of fungi, but have been least frequently observed in the Oomycetes.Sunflower (Helianthus annuus) seedlings were inoculated with a North Dakota isolate of race 2 Plasmopara halstedii, the causal agent of sunflower downy mildew. Systemic disease symptoms developed within 14 days and samples were prepared for transmission electron microscopy using standard techniques.

Seed infection and latent infection of sunflowers by Plasmopara halstedii

1974 ◽  
Vol 52 (1) ◽  
pp. 231-238 ◽  
Author(s):  
Yigal Cohen ◽  
W. E. Sackston
Keyword(s):  
Downy Mildew ◽  
Latent Infection ◽  
Systemic Infection ◽  
Seed Infection ◽  
Plasmopara Halstedii ◽  
Widespread Dissemination

Sunflowers bud-inoculated with Plasmopara halstedii became systemically infected with downy mildew and produced infected seeds at 15 to 30 °C. Oospores were observed in seeds of inoculated and also naturally infected plants from the field. Infected seeds gave rise to symptomless plants. Infected seeds proved effective as inoculum, inducing infection in 14 to 89% of the plants inoculated at 20 °C. Most of the infections (80%) were symptomless (latent).Systemic infection occurred, but latent infection was more frequent, in plants grown in soil containing debris of mildewed plants. Latent infection also occurred in uninoculated plants through belowground contact with systemically infected plants. Seed produced by plants with latent infection may carry the pathogen, and may give rise to more plants with latent infection, accounting for widespread dissemination of the disease before plants with typical symptoms are observed.

Membrane-bound vesicles associated with the microvilli in the midgut of the freshwater microcrustacean, Daphnia magna

1983 ◽  
Vol 41 ◽  
pp. 480-481
Author(s):  
Patricia L. Jansma
Keyword(s):  
Daphnia Magna ◽  
Intestinal Epithelial Cells ◽  
Uranyl Acetate ◽  
Intestinal Epithelial ◽  
Chlamydomonas Reinhardii ◽  
Thin Sections ◽  
Saturated Water ◽  
Cacodylate Buffer ◽  
Membrane Bound ◽  
Ethanol Series

The presence of the membrane bound vesicles or blebs on the intestinal epithelial cells has been demonstrated in a variety of vertebrates such as chicks, piglets, hamsters, and humans. The only invertebrates shown to have these microvillar blebs are two species of f1ies. While investigating the digestive processes of the freshwater microcrustacean, Daphnia magna, the presence of these microvillar blebs was noticed.Daphnia magna fed in a suspension of axenically grown green alga, Chlamydomonas reinhardii for one hour were narcotized with CO2 saturated water. The intestinal tracts were excised in 2% glutaraldehyde in 0.2 M cacodyl ate buffer and then placed in fresh 2% glutaraldehyde for one hour. After rinsing in 0.1 M cacodylate buffer, the sample was postfixed in 2% OsO4, dehydrated with a graded ethanol series, infiltrated and embedded with Epon-Araldite. Thin sections were stained with uranyl acetate and Reynolds lead citrate before viewing with the Philips EM 200.

An Electron Microscopic Study of the Acute Effects of Hypothalamic Releasing Factors on the Anterior Pituitary Gland

1968 ◽  
Vol 26 ◽  
pp. 232-233
Author(s):  
P.W. Coates ◽  
E.A. Ashby ◽  
L. Krulich ◽  
A. Dhariwal ◽  
S. McCann
Keyword(s):  
Anterior Pituitary ◽  
Microscopic Investigation ◽  
Uranyl Acetate ◽  
Electron Microscopic Investigation ◽  
Electron Microscopic ◽  
Tissue Samples ◽  
Thin Sections ◽  
Dense Membrane ◽  
Membrane Bound ◽  
Releasing Factors

The morphologic effects on somatotrophs of crude sheep hypothalamic extract prepared from stalk-median eminence were studied by electron microscopy in conjunction with concurrently run bioassays performed on the same tissue samples taken from young adult male Sherman rats.Groups were divided into uninjected controls and injected experimentals sacrificed at 5', 15', and 30' after injection. Half of each anterior pituitary was prepared for electron microscopic investigation, the other half for bioassay. Fixation using collidine buffered osmium tetroxide was followed by dehydration and embedment in Maraglas. Uranyl acetate and lead citrate were used as stains. Thin sections were examined in a Philips EM 200.Somatotrophs from uninjected controls appeared as described in the literature (Fig. 1). In addition to other components, these cells contained moderate numbers of spherical, electron-dense, membrane-bound granules approximately 350 millicrons in diameter.

The ultrastructure of the double membrane-bound bodies and endoplasmic reticulum in serial sections of wheat spot mosaic-affected wheat plants

1990 ◽  
Vol 48 (3) ◽  
pp. 694-695
Author(s):  
M. H. Chen ◽  
C. Hiruki
Keyword(s):  
Endoplasmic Reticulum ◽  
High Resolution ◽  
Membrane Structure ◽  
Mosaic Disease ◽  
Serial Sections ◽  
Thin Sections ◽  
Double Membrane ◽  
Southern Alberta ◽  
Membrane Bound ◽  
Scanning Em

Wheat spot mosaic disease was first discovered in southern Alberta, Canada, in 1956. A hitherto unidentified disease-causing agent, transmitted by the eriophyid mite, caused chlorosis, stunting and finally severe necrosis resulting in the death of the affected plants. Double membrane-bound bodies (DMBB), 0.1-0.2 μm in diameter were found to be associated with the disease.Young tissues of leaf and root from 4-wk-old infected wheat plants were fixed, dehydrated, and embedded in Spurr’s resin. Serial sections were collected on slot copper grids and stained. The thin sections were then examined with a Hitachi H-7000 TEM at 75 kV. The membrane structure of the DMBBs was studied by numbering them individually and tracing along the sections to see any physical connection with endoplasmic reticulum (ER) membranes. For high resolution scanning EM, a modification of Tanaka’s method was used. The specimens were examined with a Hitachi Model S-570 SEM in its high resolution mode at 20 kV.

Symptoms Development as Tools to Differentiate Dorizontal Resistance in Sunflower

Agrotek ◽  
2018 ◽  
Vol 2 (6) ◽  
Author(s):  
Cipta Meliala ◽  
Felicity Fear ◽  
Denis Tourvieille de Labrouhe
Keyword(s):  
Downy Mildew ◽  
Natural Infection ◽  
Resistance Mechanism ◽  
Good Method ◽  
Vegetative Stage ◽  
Horizontal Resistance ◽  
Symptom Development ◽  
Plasmopara Halstedii ◽  
Controlled Conditions ◽  
Symptom Progression

Downy mildew symptoms caused by Plasmopara halstedii encountered in sunflower plantation are varied. This variation may be related to the resistance mechanism presented by plant to the invasion of the fungus. Our objectives were firstly is to evaluate symptom development after fungus race 710 inoculation on some vegetative stage of susceptible hybrid. Second objective is to evaluate the reaction some sunflower genotypes after fungus inoculation. The study was conducted under controlled conditions or under netting cages in the field. The development of downy mildew symptoms were affected by all factors studied. Shoot inoculation may present a good method to produce downy mildew symptom similar to the natural infection. Downy mildew symptom progression may be used to screen a genotype with a horizontal resistance.

scholarly journals Immunogenicity of HIV-1-Based Virus-Like Particles with Increased Incorporation and Stability of Membrane-Bound Env

Vaccines ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 239
Author(s):  
Christopher A. Gonelli ◽  
Hannah A. D. King ◽  
Charlene Mackenzie ◽  
Secondo Sonza ◽  
Rob J. Center ◽  
...  
Keyword(s):  
Neutralizing Antibody ◽  
Antibody Responses ◽  
Neutralization Activity ◽  
Virus Like Particles ◽  
Antibody Isotypes ◽  
Immunodeficiency Virus ◽  
Proline Substitution ◽  
Membrane Bound ◽  
Antibody Epitopes ◽  
Hiv 1

An optimal prophylactic vaccine to prevent human immunodeficiency virus (HIV-1) transmission should elicit protective antibody responses against the HIV-1 envelope glycoprotein (Env). Replication-incompetent HIV-1 virus-like particles (VLPs) offer the opportunity to present virion-associated Env with a native-like structure during vaccination that closely resembles that encountered on infectious virus. Here, we optimized the incorporation of Env into previously designed mature-form VLPs (mVLPs) and assessed their immunogenicity in mice. The incorporation of Env into mVLPs was increased by replacing the Env transmembrane and cytoplasmic tail domains with those of influenza haemagglutinin (HA-TMCT). Furthermore, Env was stabilized on the VLP surface by introducing an interchain disulfide and proline substitution (SOSIP) mutations typically employed to stabilize soluble Env trimers. The resulting mVLPs efficiently presented neutralizing antibody epitopes while minimizing exposure of non-neutralizing antibody sites. Vaccination of mice with mVLPs elicited a broader range of Env-specific antibody isotypes than Env presented on immature VLPs or extracellular vesicles. The mVLPs bearing HA-TMCT-modified Env consistently induced anti-Env antibody responses that mediated modest neutralization activity. These mVLPs are potentially useful immunogens for eliciting neutralizing antibody responses that target native Env epitopes on infectious HIV-1 virions.

scholarly journals Updated Characterization of Races of Plasmopara halstedii and Entomopathogenic Fungi as Endophytes of Sunflower Plants in Axenic Culture

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 268
Author(s):  
Pedro Miranda-Fuentes ◽  
Ana B. García-Carneros ◽  
Leire Molinero-Ruiz
Keyword(s):  
Plant Growth ◽  
Downy Mildew ◽  
Entomopathogenic Fungi ◽  
Genetic Resistance ◽  
Axenic Culture ◽  
Plasmopara Halstedii ◽  
Successful Establishment ◽  
Axenic Conditions ◽  
Highly Virulent

The management of downy mildew (Plasmopara halstedii) in sunflower, is heavily dependent on genetic resistance, whilst entomopathogenic fungi (EF) can reduce other sunflower diseases. In this work, we characterized P. halstedii from Spain and other countries collected in the past few years. Twenty-three races were identified (the most frequent in Spain being 310, 304, 705 and 715), with an increasing proportion of highly virulent races. Five isolates from countries other than Spain overcame the resistance in RHA-340. In addition, we assessed the efficacy of five EF against downy mildew and their effects on sunflower growth in axenic conditions. None of the entomopathogens reduced disease severity, nor did they have any effect on plant growth when applied together with P. halstedii. In contrast, three EF reduced some of the plant growth variables in the absence of the pathogen. Microbiological and molecular diagnostics suggest that the axenic system and the short experimental time used in this study did not favor the successful establishment of EF in the plants or their potential biocontrol effect. Our results show a shift in P. halstedii racial patterns and suggest that soil as a growth substrate and long infection times are needed for EF effectiveness against downy mildew.

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