The infection process of Puccinia xanthii f. sp. ambrosiae-trifidae on Ambrosia trifida

Botany ◽  
2011 ◽  
Vol 89 (11) ◽  
pp. 771-777 ◽  
Author(s):  
Ping Zhang ◽  
Guo-zhong Lu ◽  
Xiao-dong Sun ◽  
Wei Zhang ◽  
Bo Qu ◽  
...  
Keyword(s):  
Leaf Surface ◽  
Rust Fungus ◽  
Infection Process ◽  
Host Tissue ◽  
Liaoning Province ◽  
Invasive Weed ◽  
Ambrosia Trifida ◽  
Teliospore Germination ◽  
Germ Tubes ◽  
Host Tissues

Puccinia xanthii Schwein. f. sp. ambrosiae-trifidae S.W.T. Batra is an obligate parasitic rust fungus of Ambrosia trifida Linn. Field investigations in Liaoning Province, China, showed that it is an effective biocontrol agent of this alien invasive weed. Its infection of the plant was observed by light microscopy combined with Coomassie Brilliant Blue R-250 staining. We report the infection process, including teliospore germination and basidiospore formation on the host leaf surface, penetration of host tissue, and development of fungal hyphae within the host tissue. Fresh teliospores began to germinate from the germ pore within 1 h under suitable conditions and soon produced basidiospores or secondary basidiospores. Basidiospores falling on host leaves germinated from the end of the basidiospore opposite to the apiculus. Appressoria of germ tubes tended to orient along leaf epidermis cell ridges or at junctions near stomata rather than fixing randomly on the leaf surface. These germ tubes grew for short or longer distances before forming appressoria. The rust fungus directly penetrated the host epidermis by infectious pegs rather than through stomata. Within host tissues, the rust fungus formed intraepidermal vesicles, primary hyphae, intracellular hyphae, and M-haustoria. The intricate infectious structures formed by P. xanthii f. sp. ambrosiae-trifidae on or in host tissues suggest that the rust fungus is a suitable organism for researching the interaction between the pathogen and host plant.

scholarly journals Transfer of label from 3H-glucose in Digitaria eriantha leaves to the rust fungus Puccinia digitariae Pole Evans.

1985 ◽  
Vol 33 (8) ◽  
pp. 809-812 ◽  
Author(s):  
M E Rey ◽  
H M Garnett
Keyword(s):  
Primary Infection ◽  
Secondary Infection ◽  
Rust Fungus ◽  
Infection Process ◽  
Bremia Lactucae ◽  
Infection Structures ◽  
Obligate Parasites ◽  
Digitaria Eriantha ◽  
Germ Tubes

Digitaria eriantha pentzii was fed 3H-glucose prior to inoculation with uredospores of Puccinia digitariae Pole Evans. Twenty-one hours after inoculation, uptake of label from 3H-glucose by the primary infection structures of P. digitariae was demonstrated employing autoradiography. These results indicate that an exchange of nutrients between host and pathogen occurs very early on in the infection process, during the formation of the primary infection structures. Despite contrary reports that obligate parasites receive no nutrition before establishment of haustoria, this study supports the work of Andrews (Can J Bot 53:1103, 1975), who demonstrated uptake of 3H-glucose label from lettuce cotyledons into the primary and secondary infection vesicles, appressoria, and germ tubes of Bremia lactucae.

Morphology of infection of onion leaves by Alternaria porri

1994 ◽  
Vol 72 (8) ◽  
pp. 1164-1170 ◽  
Author(s):  
Theresa A. S. Aveling ◽  
Heidi G. Snyman ◽  
F. H. J. Rijkenberg
Keyword(s):  
Electron Microscopy ◽  
Epidermal Cell ◽  
Leaf Surface ◽  
Infection Process ◽  
Mesophyll Cells ◽  
Transmission Electron ◽  
Close Proximity ◽  
Alternaria Porri ◽  
Infected Cells ◽  
Germ Tubes

Conidial germination of Alternaria porri, formation of prepenetration structures, penetration of the onion leaf surface, and the postpenetration processes were studied using light, scanning electron, and transmission electron microscopy. Ninety-six percent of conidia germinated at 25 °C within 24 h of inoculation. Each conidium formed several germ tubes that grew in any direction across the leaf surface. Each germ tube usually terminated in a bulbous appressorium formed directly on the epidermal cell (52.4% of appressoria) or on a stoma (48.6% of appressoria). Following direct penetration of the outer epidermal cell wall or the stoma, bulbous primary hyphae developed below the appressoria. Secondary hyphae developed from the primary hyphae within 48 h after inoculation and grew within the intercellular spaces penetrating mesophyll cells. The changes in ultrastructure of cells in close proximity to hyphae and of infected cells are described. Key words: Allium cepa, electron microscopy, infection process, purple blotch.

Cytoplasmic dynamics of the tubulin and actin cytoskeletons during teliospore germination and basidiospore formation in a rust fungus

1996 ◽  
Vol 54 ◽  
pp. 798-799
Author(s):  
Robert W. Roberson ◽  
William P. Sharp ◽  
John P. Shields ◽  
Steve Sayegh ◽  
Bader F. Al-Anzi
Keyword(s):  
Cell Biology ◽  
Plant Pathogens ◽  
Developmental Stages ◽  
Rust Fungus ◽  
Complex Life Cycle ◽  
Model Organisms ◽  
Teliospore Germination ◽  
Basidiomycetous Fungus ◽  
Temporally Correlated ◽  
Germ Tubes

Gymnosporangium clavipes C. & P. is a basidiomycetous fungus belonging to a common and destructive group of plant pathogens known to as the rusts. The rusts are best known for their damage to economically important crops including corn, wheat, oats, and barley and have become important model organisms in cell biology studies. Of all the stages in their complex life cycle, perhaps the most interesting are those involved in teliospore germination and basidiospore formation.As illustrated with scanning electron microscopy teliospores of G. clavipes are ellipsoidal spores consisting of an apical and basal cell (Fig. 1). Upon germination of the teliospore, four discrete morphological events occur that give rise to mature basidiospores. These events include: i) emergence of germ tubes (Fig. 2), ii) formation of three septal cross walls segmenting the germ tube into four compartments (Fig. 3), iii) growth of a single sterigma from each compartment, (Fig. 4) and iv) enlargement of sterigmal tips to form individual basidiospores (Fig. 5). The objective of this research was to determine whether these developmental stages were temporally correlated with changes in the organization of the tubulin and actin cytoskeletons.

scholarly journals The infection process of Colletotrichum fuscum on oregano leaves and stems

2021 ◽  
Vol 20 (5) ◽  
pp. 97-106
Author(s):  
Beata Zimowska ◽  
Ewa Dorota Król
Keyword(s):  
Infection Process ◽  
Host Tissue ◽  
Conidial Suspension ◽  
Origanum Vulgare ◽  
Time Intervals ◽  
Necrotic Spots ◽  
Stems And Leaves ◽  
Germ Tubes ◽  
Scanning Electron ◽  
Direct Placement

Anthracnose, caused by Colletotrichum fuscum, produces regular necrotic spots on oregano leaves and stems, causing severe crop losses. In this study, Koch’s postulates were fulfilled and infection process was investigated using scanning electron microscopy. Leaves and stems of Origanum vulgare were inoculated and incubated at 24°C in wet chambers under high relative humidity. Pathogenicity experiments demonstrated that all tested C. fuscum isolates had infected stems and leaves of oregano. Of all inoculation methods, direct placement of colonized agar plugs on injured epidermis and soaking plant organs in conidial suspension were the most effective. The behavior of the conidia deposited on the oregano leaves was investigated at different time intervals after inoculation: at 12, 18, 32, 48, 67 and 98 h. Conidia produced an appressoria of varying shapes which has been formed at the end of germ tubes of different lengths. Penetration to host tissue through stomata was observed. Acervuli formed on the leaves surface after 98 h after inoculation, typically with sharp pointed setoses.

Morphogenetic properties of the skin axolotl limb regeneration

Development ◽  
1980 ◽  
Vol 58 (1) ◽  
pp. 265-288
Author(s):  
Jonathan M. W. Slack
Keyword(s):  
Limb Regeneration ◽  
Host Tissue ◽  
Tissue Formation ◽  
Cellular Composition ◽  
Posterior Half ◽  
Tail Bud ◽  
Threshold Theory ◽  
Anterior Side ◽  
Immunological Rejection ◽  
Host Tissues

A study has been made of the morphogenetic properties of anterior and posterior skin from the lower forelimb of the axolotl. The basic experiment consisted of a graft of a half cuff of skin from a donor to a host limb followed by a 2-week healing period, amputation through the graft, and a study of the resulting regenerate. Limbs with double posterior skin formed double posterior regenerates and, in contrast, limbs with double anterior skin formed normal or slightly hypomorphic regenerates. Posterior skin from post-metamorphic animals had a similar but weaker effect to that from ordinary axolotls. Immunological rejection of allografts could be completely avoided if the donor limb was transplanted to the flank of the host when both were at the stage of tail-bud embryos, and the skin graft was later carried out between the supernumerary limb and one of the host limbs. This technique was used to show that immunological rejection does not affect the formation of duplicates from the limbs with double posterior skin, and to facilitate the studies of the cellular provenance of the regenerate. The cellular composition of duplicate regenerates was studied by using both triploid donors and triploid hosts. It was shown that the posterior side of the duplications consisted wholly of host tissue and the anterior side consisted of mixed donor and host tissue. Formation of the duplicated regenerate therefore seems to involve positional reprogramming of both donor and host tissues together with metaplasia of the donor tissue. It was not possible to inhibit the duplication-inducing property of posterior skin by treatment with a variety of enzymes. A model based on the serial threshold theory of regeneration is advanced to explain the results.This model successfully accounts for the observed non-equivalence of anterior and posterior skin, and also explains the different regeneration behaviour of anterior and posterior half limbs, the limited regeneration of double anterior limbs, and the pattern expansion and contraction shown by regenerates from double posterior limbs.

Resistance mechanisms in Lycopersicon spp. to tomato powdery mildew (Oidium neolycopersici)

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. S141-S144 ◽  
Author(s):  
A. Lebeda ◽  
B. Mieslerová ◽  
L. Luhová ◽  
K. Mlíčková
Keyword(s):  
Germ Tube ◽  
Leaf Surface ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Host Tissue ◽  
Tissue Response ◽  
Limited Information ◽  
Oidium Neolycopersici ◽  
Conidium Germination ◽  
Tomato Powdery Mildew

Limited information on the resistance mechanisms in Lycopersicon spp. to Oidium neolycopersici is still available. Macroscopically the resistance is characterized by a very low amount of mycelium development and a lack of sporulation. The leaf surface did not effectively inhibite conidium germination, however significant differences in germ tube and appressorium development were recorded. A large variation was observed in host tissue response. The prevailing resistance mechanism was hypersensitivity (HR). Considerable changes of peroxidase and catalase activities during pathogenesis were detected among tested wild Lycopersicon spp. There was positive correlation between increasing of peroxidase activity and extent of necrosis. Histochemistry showed large differences in production of superoxid ions, H<sub>2</sub>O<sub>2</sub> and peroxidase in Lycopersicon spp. with various level of resistance.

RIBONUCLEASE ACTIVITY IN RUSTED WHEAT LEAVES

1961 ◽  
Vol 39 (4) ◽  
pp. 775-784 ◽  
Author(s):  
R. Rohringer ◽  
D. J. Samborski ◽  
C. O. Person
Keyword(s):  
Leaf Rust ◽  
Direct Evidence ◽  
Specific Activity ◽  
Host Tissue ◽  
Ribonuclease Activity ◽  
Rnase Activity ◽  
Rnase Inhibitor ◽  
Germination Medium ◽  
Wheat Leaves ◽  
Host Tissues

Extracts from primary leaves of Lee wheat were prepared at various days following inoculation with races of leaf rust and tested for ribonuclease (RNase) activity. As early as 24 hours after inoculation there was a marked increase in the specific activity of the enzyme in extracts of rusted host tissues. A further increase in activity was observed during later stages of infection, with the susceptible and resistant reacting tissue differing only in the degree of their response. Extracts from noninoculated control leaves exhibited a constant RNase activity throughout the period of observation. The germination medium and extracts from germinating uredospores contained comparatively little RNase activity. No direct evidence was obtained either for the possible release of the enzyme from particulate cellular fractions of the host tissue as a result of infection or for the removal of an RNase inhibitor in the host tissue responding to infection.

Rod-shaped and spherical viruslike particles in cowpea rust fungus

1978 ◽  
Vol 56 (8) ◽  
pp. 963-975 ◽  
Author(s):  
John G. McDonald ◽  
Michèle C. Heath
Keyword(s):  
Phosphotungstic Acid ◽  
Rust Fungus ◽  
Ammonium Molybdate ◽  
Size Distributions ◽  
Wide Diameter ◽  
Thin Sectioning ◽  
Rigid Rod ◽  
Viruslike Particles ◽  
The Stability ◽  
Germ Tubes

Three types of rod-shaped viruslike particles (VLPs) (a short rigid rod (RR), 260 × 12 nm. a long narrow-diameter flexuous rod (NFR), 660 × 10 nm, and a long wide-diameter flexuous rod (WFR), 740 × 16 nm) and a spherical VLP (35 nm in diameter) were found in extracts of uredospores, germ tubes, and pustules of cowpea rust, negatively stained with ammonium molybdate. Both the size distributions and the stability of these VLPs was affected by the choice of stain since when phosphotungstic acid was used, two additional length classes of the RR (150 nm and 90 nm) were noted, and this stain tended to disassemble the WFR by unwinding the helix of this particle. The WFR also disassembled at pHs 4and5 in 10 mM acetate but only at pH 4 in the presence of 0.2 M NaCl. Examination of cowpea rust by thin sectioning revealed the presence of four types of VLPs. Morphologies of these particle types were consistent with the data obtained by negative staining.

scholarly journals Host-Specific Activation of Entomopathogenic Nematode Infective Juveniles

Insects ◽  
2018 ◽  
Vol 9 (2) ◽  
pp. 59 ◽  
Author(s):  
Valentina Alonso ◽  
Shyon Nasrolahi ◽  
Adler Dillman
Keyword(s):  
Entomopathogenic Nematodes ◽  
Morphological Changes ◽  
Entomopathogenic Nematode ◽  
Infection Process ◽  
Bacterial Symbiont ◽  
Infective Juvenile ◽  
Free Living ◽  
Initial Infection ◽  
Host Tissues ◽  
Insect Parasites

Entomopathogenic nematodes (EPNs) are potent insect parasites and have been used for pest control in agriculture. Despite the complexity of the EPN infection process, hosts are typically killed within 5 days of initial infection. When free-living infective juveniles (IJs) infect a host, they release their bacterial symbiont, secrete toxic products, and undergo notable morphological changes. Collectively, this process is referred to as “activation” and represents the point in a nematode’s life cycle when it becomes actively parasitic. The effect of different host tissues and IJ age on activation, and how activation itself is related to virulence, are not well understood. Here, we employed a recently developed bioassay, which quantifies IJ activation, as a tool to address these matters. Appreciating that activation is a key part of the EPN infection process, we hypothesized that activation would positively correlate to virulence. Using the EPNs Steinernema carpocapsae and S. feltiae we found that EPN activation is host-specific and influenced by infective juvenile age. Additionally, our data suggest that activation has a context-dependent influence on virulence and could be predictive of virulence in some cases such as when IJ activation is especially low.

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