Ultrastructure of the Host-Parasite Relationships of Pseudoperonospora humuli on Hops

1977 ◽  
Vol 25 (6) ◽  
pp. 585 ◽  
Author(s):  
RD Pares ◽  
AD Greenwood
Keyword(s):  
Leaf Tissue ◽  
Host Cells ◽  
Wall Structure ◽  
Infected Leaf ◽  
Cell Penetration ◽  
Pseudoperonospora Humuli ◽  
Host Cell Wall ◽  
Staining Techniques ◽  
Host Parasite ◽  
Infected Leaf Tissue

Infected leaf tissue was examined at 3, 4, 5 and 6 days after inoculation, after different fixing and staining techniques. One example of stomata1 penetration was seen. Examples of cell penetration and haustorium development were examined in detail. Haustoria penetrate host cells by altering host cell wall structure, and lomasomes are frequently present in the haustorium neck. Haustoria do not have nuclei and in early stages have abundant mitochondria that gradually decrease in number as infection advances.

Growth-inhibiting Fungicides Affect Detection of Phytophthora ramorum from Infected Foliage and Roots

2014 ◽  
Vol 15 (1) ◽  
pp. 36-40 ◽  
Author(s):  
Nina Shishkoff
Keyword(s):  
Root Colonization ◽  
Leaf Tissue ◽  
Phytophthora Ramorum ◽  
Infected Leaf ◽  
Inoculum Production ◽  
Affect Detection ◽  
Flow Through ◽  
Whole Plants ◽  
Infected Leaf Tissue ◽  
Growth Inhibiting

Growth-inhibiting fungicides are used routinely to control common and regulated Oomycete pathogens. This study investigated whether such fungicides could affect detection of Phytophthora ramorum from plant tissue, both foliage and roots. Whole plants of Rhododendron × ‘Cunningham's White’ were inoculated with P. ramorum and treated 3 days later with fosetyl-Al, mefenoxam, or propamocarb. The foliage was sampled over time to see if fungicides prevented successful culturing of the pathogen from infected leaf tissue or interfered with detection using real-time PCR or ELISA. Mefenoxam significantly reduced the ability to culture the pathogen from leaves for the first 6 weeks while recovery from leaves treated with other fungicides did not differ from water-treated controls; detection using PCR or ELISA was not affected by fungicide application. The roots of Viburnum cuttings were inoculated with P. ramorum and then treated 4 days later with fosetyl-Al, mefenoxam, or propamocarb. The amount of inoculum in flow through water samples taken weekly for 5 weeks was quantified and percent root colonization determined at the end of the experiment. Propamocarb had no effect on inoculum production or root infection, while viable inoculum production was significantly decreased in fosetyl-Al- or mefenoxam-treated plants over 5 weeks, and root colonization was significantly decreased. Accepted for publication 23 January 2014. Published 18 March 2014.

scholarly journals A Virus Infecting Hibiscus rosa-sinensis Represents an Evolutionary Link Between Cileviruses and Higreviruses

2021 ◽  
Vol 12 ◽  
Author(s):  
Alejandro Olmedo-Velarde ◽  
John Hu ◽  
Michael J. Melzer
Keyword(s):  
Phylogenetic Analyses ◽  
Leaf Tissue ◽  
Spherical Particles ◽  
Infected Leaf ◽  
Spot Virus ◽  
Reading Frame ◽  
Reverse Transcription Pcr ◽  
Foliar Symptoms ◽  
Landscape Plants ◽  
Infected Leaf Tissue

Hibiscus (Hibiscus spp.) are popular ornamental and landscape plants in Hawaii which are susceptible to foliar diseases caused by viruses belonging to the genera Cilevirus and Higrevirus (family Kitaviridae). In this study, a virus infecting H. rosa-sinensis plants displaying foliar symptoms consistent with infection by a kitavirus, including yellow chlorotic blotches with a green perimeter, was characterized. The genome consisted of two RNAs 8.4 and 4.4 kb in length, and was organized most similarly to cileviruses, but with important distinctions. These included the location of the p29 homolog as the 3′-terminal open reading frame (ORF) of RNA2 instead of its typical locus at the 3′-end of RNA1; the absence of a p15 homolog on RNA2 and the adjacent intergenic region which also harbors small putative ORFs of unknown function; and the presence of an ORF encoding a 10 kDa protein at the 3′-terminal end of RNA1 that was also found to be present in the hibiscus green spot virus 2 genome. Spherical particles approximately 55–65 nm in diameter were observed in infected leaf tissue, and viral RNA was detected by reverse-transcription PCR in individual mites collected from symptomatic plants tentatively identified as Brevipalpus yothersi. Although phylogenetic analyses placed this virus between the higrevirus and cilevirus clades, we propose the tentative taxonomic placement of this virus, designated hibiscus yellow blotch virus (HYBV), within the genus Cilevirus.

An ultrastructural study of the marine diatom Licmophora hyalina and its parasite Ectrogella perforons. I. Infection of host cells

1980 ◽  
Vol 58 (11) ◽  
pp. 1280-1290 ◽  
Author(s):  
Chandralata Raghu Kumar
Keyword(s):  
Plasma Membrane ◽  
Germ Tube ◽  
Host Cells ◽  
Marine Diatom ◽  
Electron Microscopic ◽  
Fungal Parasite ◽  
Successful Infection ◽  
Host Cell Wall ◽  
Host Plasma Membrane ◽  
Host Parasite

An electron microscopic study has been made on the infection and penetration of the marine diatom Licmophora hyalina Agardh by Ectrogella perforons Petersen, an obligate fungal parasite of diatoms. The zoospores encyst on the host cell wall. The nucleus of the cyst may be situated proximal or distal to the host wall. A germ tube is produced from the side where the nucleus is situated. The germ tube may be branched or unbranched. The penetrating germ tube swells distally, develops an appressorium at the site of penetration of the host wall, and pierces the host wall in the form of an infection peg. The infection peg is smaller in diameter than the germ tube and the appressorium. Successful infection takes place always at the areolae of the diatom wall. The infection peg may directly inject its contents by piercing the subfrustular layer of the diatom wall or may grow for some distance beneath the subfrustular layer. At the site of entry the host plasma membrane invaginates and surrounds the fungal protoplast. Initially, the host–parasite interface consists of a two-layered envelope of which the outer one is the host plasma membrane and the inner one the fungal plasma membrane.

INCORPORATION OF CYTIDINE-H3 INTO THE PRIMARY LEAF OF WHEAT FOLLOWING INFECTION WITH PUCCINIA RECONDITA ROB. EX DESM.

1963 ◽  
Vol 41 (10) ◽  
pp. 1501-1508 ◽  
Author(s):  
J. Nielsen ◽  
R. Rohringer
Keyword(s):  
Host Cell ◽  
Ribonucleic Acid ◽  
Host Tissue ◽  
Host Cells ◽  
Puccinia Recondita ◽  
Infected Leaf ◽  
Cell Nuclei ◽  
Short Term ◽  
Wheat Leaves ◽  
Host Parasite

In short-term experiments, cytidine-H3 was fed to rusted and healthy areas of wheat leaves. The incorporated activity, presumably residing in ribonucleic acid, was detected by microautoradiographic methods. Most of the label was found to be incorporated in host cell nuclei. Little incorporation occurred in extranuclear structures of host cells, including chloroplasts. Very long autoradiographic exposure times failed to reveal any incorporation into the fungus.Host cells in infected leaf areas contained considerably less label in their nuclei and cytoplasm than those in cells further from the site of infection. This effect of the fungus extended over some distance into uninvaded host tissue, but not beyond 100 μ from the periphery of the mycelium. The decreased cytidine incorporation in the affected host tissue is not caused by possible changes in pool size of endogenous cytidine. The significance of these results for the host–parasite interaction is briefly discussed.

scholarly journals Survival and Persistence of Alternaria dauci in Carrot Cropping Systems

Plant Disease ◽  
2002 ◽  
Vol 86 (10) ◽  
pp. 1115-1122 ◽  
Author(s):  
B. M. Pryor ◽  
J. O. Strandberg ◽  
R. M. Davis ◽  
J. J. Nunez ◽  
R. L. Gilbertson
Keyword(s):  
Crop Residue ◽  
Cropping Systems ◽  
Mineral Soil ◽  
Leaf Tissue ◽  
Infected Leaf ◽  
Alternaria Dauci ◽  
Carrot Seed ◽  
Infected Leaf Tissue ◽  
Over Time ◽  
Seedling Infection

Alternaria dauci was recovered in California from carrot crop residue and from volunteer carrot plants in fallow carrot fields. The fungus was not recovered from common weeds surrounding fallow fields. To evaluate further the survival of A. dauci on carrot crop residue, infected carrot leaf tissue was placed in fields or in soil in greenhouse pots, and recovered over time. In California, A. dauci was recovered from infected leaf tissue in both fallow and irrigated fields for as long as 1 year. In Florida, A. dauci was recovered from infected leaf tissue in fallow fields for up to 30 weeks. In greenhouse experiments, A. dauci was recovered from infected leaf tissue for as long as 1 year in dry soil, but only up to 30 weeks in soil that was watered weekly. To determine the infectivity of A. dauci borne on carrot crop residue, infected carrot crops were incorporated into organic and mineral field soils, and soil samples were collected over time. Carrot seed were planted in collected soil, and seedling infection by A. dauci was recorded. Seedling infection was detected up to 13 and 14 weeks after crop incorporation in organic and mineral soil, respectively. Seedling infection was detected for up to 5 weeks in soil that remained dry compared with 3 weeks in flooded soil.

Host – parasite relationships between the fungus Leptosphaerulina crassiasca and peanut

1992 ◽  
Vol 70 (9) ◽  
pp. 1724-1733 ◽  
Author(s):  
Mei-Lee Wu ◽  
Richard T. Hanlin
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Germ Tube ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Detached Leaves ◽  
Host Cell Wall ◽  
Host Parasite ◽  
Germ Tubes ◽  
Infection Hypha

The mode of penetration and infection of the peanut leaf by Leptosphaerulina crassiasca were studied by means of light and electron microscopy. The attachment of the multicellular ascospores to the leaf surface was by a mucilagenous sheath that covered the ascospores at maturity. This sheath expanded rapidly in moisture and it extended along the germ tube as it elongated. Two types of germ tubes appeared to be formed, a short one and a relatively long one. Short germ tubes were not delimited by septa, and they penetrated the cuticle and host epidermal cell wall directly without appressorium formation. Penetration occurred 2–6 h after inoculation. The wall was breached by a relatively broad infection hypha that expanded in width inside the host cell wall. The lack of mechanical rupture at the infection site indicated that penetration may involve enzymatic activity. Intracellular hyphae were present in the epidermal cells, but only intercellular hyphae occurred in the palisade and spongy mesophyll tissues. The intercellular hyphae were frequently appressed to the outer surface of the host cell wall. Infected areas rarely exceeded 1 mm in diameter, and they were only sparsely colonized by hyphae of the pathogen. Host cells in the vicinity of hyphae underwent senescence and death. One to 2 months after inoculation, pseudothecia formed in the dead tissues of detached leaves. In some instances the presence of penetration hyphae by short germ tubes induced the formation of a papilla inside the host cell wall, which either restricted growth of the infection hypha or resulted in the death of the germ tube and the cell from which it arose. Long germ tubes were delimited by simple septa and they terminated in an appressorium; however, details of their behavior were not studied. Key words: Arachis hypogaea, Ascomycotina, Dothideales, leaf scorch, pepper spot.

A physiological study of Panicum maximum infected by Phyllachora paspalicola

1984 ◽  
Vol 62 (11) ◽  
pp. 2283-2289 ◽  
Author(s):  
M. E. C. Rey ◽  
H. M. Garnett
Keyword(s):  
Leaf Tissue ◽  
Infected Leaf ◽  
Panicum Maximum ◽  
Tissue Concentrations ◽  
Bisphosphate Carboxylase ◽  
Morphological Studies ◽  
Transmission Electron ◽  
Bundle Sheath Cells ◽  
Leaf Pathogen ◽  
Infected Leaf Tissue

Detailed morphological studies of the leaf pathogen Phyllachora paspalicola (tarspot) on its host Panicum maximum Jacq. have been previously described. This research reports physiological changes in leaf tissue infected by P. paspalicola. Aspects of photosynthetic and nitrogen metabolism were studied in healthy and tarspot-infected leaf tissue. Concentrations of glucose, fructose, and sucrose in infected and noninfected leaves were also measured. Gross and net photosynthetic rates declined significantly in tarspot-infected leaves at high disease intensities (>25%). Chlorophyll content declined in leaves exhibiting >25% infection. Transmission electron microscopy revealed disruption of lamellae and formation of large lipid bodies in infected mesophyll and bundle sheath cells. Significant changes in some C4 enzymes, such as NADP malate dehydrogenase, aspartate aminotransferase, ribulose-1,5-bisphosphate carboxylase, phosphoenolpyruvate carboxylase, were noted in tarspot-infected leaves. Small differences in the activities of NADP–malate enzyme and alanine aminotransferase were also observed. Activity of the respiratory enzyme succinate dehydrogenase was also stimulated in intensely infected leaves. An increase in nitrate levels was measured as ascopore sporogenesis occurred. At sporulation and during postsporulation, total nitrogen declined in leaves exhibiting intense infection (>25%). A small increase in glucose and fructose content occurred in leaves exhibiting mature fruiting bodies, whereas a significant (p = 0.05) increase in sucrose content was observed in infected leaves.

The Alternaria brassicae – Nectria inventa host–parasite interface

1977 ◽  
Vol 55 (4) ◽  
pp. 448-454 ◽  
Author(s):  
A. Tsuneda ◽  
W. P. Skoropad
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Host Cells ◽  
Alternaria Brassicae ◽  
Adhesive Material ◽  
Large Hole ◽  
Mature Conidium ◽  
Host Cell Wall ◽  
Host Parasite

The Verticillium state of Nectria inventa is a destructive parasite of Alternaria brassicae. Tropic growth of parasite hyphae towards hyphae and conidia of A. brassicae occurs in the vicinity of the host. Upon contact, the parasite hyphae often form appressorium-like bodies on the host cells and produce fibrous adhesive material at the host–parasite interface. Conidia are penetrated more commonly than hyphae. Penetration of the septa in hyphae results in a separation of cells. Penetration of a mature conidium also occurs commonly at a septum. The presence of a large hole in the wall of the host cell and the meshwork of material at the penetration site suggest that enzymatic breakdown of host cell wall occurs. Juvenile conidia are penetrated usually at the basal pore.

THE PHYSIOLOGY OF HOST–PARASITE RELATIONS: XV. FINE STRUCTURE IN RUST-INFECTED WHEAT LEAVES

1965 ◽  
Vol 43 (10) ◽  
pp. 1285-1292 ◽  
Author(s):  
Michael Shaw ◽  
M. S. Manocha
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Susceptible Variety ◽  
Host Cells ◽  
Resistant Variety ◽  
Subcellular Organelles ◽  
Detached Leaves ◽  
Host Cell Wall ◽  
Wheat Leaves ◽  
Host Parasite

Electron microscopy showed that the haustoria of P. graminis tritici on wheat were characterized by numerous mitochondria, an extensive endoplasmic reticulum, densely packed ribosomes, and a well-defined plasma membrane (plasmalemma), which was often invaginated by lomasomes. No evidence was obtained for cytoplasmic connections between the parasite and its host. Many of the haustoria formed on a resistant variety, Khapli, were necrotic but others were closely similar to those formed on a susceptible variety, Little Club. The haustorial necks were surrounded by a collar-like sheath formed by an extension of the host cell wall. The haustoria merely invaginated host protoplasts from which they were separated by granular encapsulations. The latter were apparently secreted mainly by the host and developed faster in Khapli than in Little Club. The presence of haustoria also induced the formation of an extensive, smooth-surfaced endoplasmic reticulum in the host, a contraction and fragmentation of the vacuole, an increase in the volume of the cytoplasm, and, ultimately, the complete degeneration of the host cells. The processes of breakdown of the subcellular organelles in the host were very similar to those which have been observed in uninfected cells in detached leaves senescing on water.

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