Cytological observations of early infection process by Fusarium oxysporum f. sp. radicis-lycopersici in tomato plants

1984 ◽  
Vol 62 (6) ◽  
pp. 1232-1244 ◽  
Author(s):  
Pierre Mathieu Charest ◽  
G. B. Ouellette ◽  
F. J. Pauzé
Keyword(s):  
Fusarium Oxysporum ◽  
Cortical Area ◽  
Middle Lamella ◽  
Infection Process ◽  
Coating Material ◽  
Plant Diseases ◽  
Host Cells ◽  
Cortical Cells ◽  
Host Cell Wall ◽  
Root Tissues

A survey of the initial infection phases of Fusarium oxysporum Schlecht. f. sp. radicis-lycopersici Jarvis and Shoemaker in tomato roots demonstrated that the epidermis was colonized from 12 to 24 h after inoculation. Until 96 h the pathogen was usually limited to the outer cortical area, where fungal cells were found to be either intercellular or intracellular. Host cell wall thickenings and papilla formation were noticeable in the cortical cells but totally absent in the endodermis and the vascular stele. In the cortical area, cytoplasm and walls of affected host cells were mostly disintegrated when the whole root tissues were colonized about 144 h after inoculation. Between 96 and 120 h, hyphae were visible in the endodermis, and 24 h later the vascular stele was colonized. In the latter area, parenchyma cells generally reacted as in the inner cortical area and invasion of vessels proceeded directly through middle lamella and pit membranes. When colonized, vessels contained fibrillogranular material interspersed with bubbles and an osmiophilic coating material. This coating material lined the vessel secondary wall and pit cavities and appeared thicker in the more occluded vessels. The possible implications of these observations on symptoms expression in this and similar plant diseases are discussed.

scholarly journals Phenylacetic Acid and Methylphenyl Acetate From the Biocontrol Bacterium Bacillus mycoides BM02 Suppress Spore Germination in Fusarium oxysporum f. sp. lycopersici

2020 ◽  
Vol 11 ◽  
Author(s):  
Je-Jia Wu ◽  
Jenn-Wen Huang ◽  
Wen-Ling Deng
Keyword(s):  
Fusarium Oxysporum ◽  
Spore Germination ◽  
Phenylacetic Acid ◽  
Hyphal Growth ◽  
Plant Diseases ◽  
Bacillus Mycoides ◽  
Tomato Root ◽  
Spore Attachment ◽  
Bacterium Bacillus ◽  
Root Tissues

Bacillus mycoides strain BM02 originally isolated from the tomato rhizosphere was found to have beneficial functions in tomato by promoting plant growth and reducing the severity of Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol). Cytological experiments demonstrated B. mycoides BM02 reduced Fol invasion by reducing spore attachment and increasing hyphal deformation in hydroponics-grown tomato root tissues. Two volatile antifungal compounds, phenylacetic acid (PAA) and methylphenyl acetate (MPA), were identified from the culture filtrates of B. mycoides BM02 by GC-MS analysis. Chemically synthesized PAA, and to a lower extent MPA, suppressed spore germination but have no effects on the hyphal growth of Fol. Our results indicated that the biocontrol agent B. mycoides BM02 produced an array of bioactive compounds including PAA and MPA to suppress plant diseases caused by Fol and other pathogenic microorganisms.

scholarly journals Cytological Analysis of Defense-Related Mechanisms Induced in Pea Root Tissues in Response to Colonization by Nonpathogenic Fusarium oxysporum Fo47

2001 ◽  
Vol 91 (8) ◽  
pp. 730-740 ◽  
Author(s):  
Nicole Benhamou ◽  
Chantal Garand
Keyword(s):  
Fusarium Oxysporum ◽  
Fungal Growth ◽  
Defense Responses ◽  
Root Surface ◽  
Outer Cortex ◽  
Cortical Cells ◽  
Symbiotic Associations ◽  
Wall Appositions ◽  
Rapid Stimulation ◽  
Root Tissues

The ability of nonpathogenic Fusarium oxysporum, strain Fo47, to trigger plant defense reactions was investigated using Ri T-DNA-transformed pea roots. Cytological investigations of strain Fo47-inoculated roots showed that the fungus grew actively at the root surface and colonized a number of epidermal and cortical cells, inducing marked host cell metabolic changes. In roots inoculated with pathogenic F. oxysporum f. sp. pisi, the pathogen multiplied abundantly through much of the tissues, whereas in Fo47-inoculated roots, fungal growth was restricted to the epidermis and the outer cortex. Invading cells of strain Fo47 suffered from serious alterations, a phenomenon that was not observed in control roots in which F. oxysporum f. sp. pisi grew so actively that the vascular stele was invaded within a few days. Strain Fo47 establishment in the root tissues resulted in a massive elaboration of hemispherical wall appositions and in the deposition of an electron-opaque material frequently encircling pathogen hyphae and accumulating in the noninfected xylem vessels. This suggests that the host roots were signaled to defend themselves through the rapid stimulation of a general cascade of nonspecific defense responses. The specific relationship established between strain Fo47 and the root tissues is discussed in relation to other types of plant-fungus interactions, including pathogenic and symbiotic associations.

Studies on the haustorium of Castilleja (Scrophulariaceae). II. The endophyte

1973 ◽  
Vol 51 (5) ◽  
pp. 923-931 ◽  
Author(s):  
David R. Dobbins ◽  
Job Kuijt
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Light Microscope ◽  
Cell Walls ◽  
Host Cells ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Host Cell Wall ◽  
Dark Staining ◽  
Host Tissues

The portion of the Castilleja haustorium within the host, the endophyte, was examined at the light-and electron-microscopic levels. The endophyte consists of a stalk of lipid-containing cells and digitate cells at its tip. Vessels run the length of the endophyte. There is a harmonious meshing between host cortical cells and those of the endophyte flank, suggesting that penetration is accomplished, in part, by cell dissolution. Crushing of cells also occurs during endophyte invasion as host phloem tissues are severely buckled and cell walls are greatly folded. Some features of digitate cells include dense cytoplasm, an abundance of endoplasmic reticulum, lateral walls that are thickened as well as those on the side adjacent to the host, and an ability to conform to the contours of host tissues. Often digitate cells are divided by very thin walls that are hardly visible under the light microscope. It is suggested that the thick cell walls may function as "free space" in the absorption of materials from the host. Within the endophyte, vessels differentiate and may contain either a finely granular, dark-staining material or a more coarsely granular, light-staining material. The particles of the latter have irregular shapes. Although granular materials are thus carried by some vessels, cells resembling the structurally intermediate "phloeotracheids" were not seen. Connections through the cell wall were not observed between parasite and host; however, within the endophyte plasmodesmata were highly branched and often contained median nodules. Transfer-like cells which have irregularly thickened walls occurred in the endophyte. Host tissues next to digitate cells appeared to be in a degraded state. Invaginations of the plasmalemma were common and small flattened vesicles were formed in some host cells from the disrupted tonoplast. In several instances, the cytoplasm had receded from the host cell wall and a "beaded" material was present in both vacuoles and large vesicles. The host cell wall at times had a very loose fibrillar appearance. Some host tracheids were occluded with a dense and dark-staining material. The xylem strands of the parasite are connected to the host xylem either by cell wall dissolution or by actual penetration of a digitate cell into a host xylary cell. The penetrating cell subsequently differentiates into a vessel member. A summary and general discussion are given to relate the two portions of the haustorium, the upper haustorium and the endophyte. The mass of new information gained in this study leads us to encourage the application of plastic embedding and sectioning techniques to further light-microscope studies on haustoria.

scholarly journals ENHANCED RESISTANCE OF TOMATO PLANTS TO FUSARIUM OXYSPORUM F.SP. RADICIS-LYCOPERSICI UPON TREATMENT WITH CHITOSAN: CYTOCHEMICAL ASPECTS OF INDUCED RESISTANCE

HortScience ◽  
1994 ◽  
Vol 29 (4) ◽  
pp. 254d-254
Author(s):  
Nicole Benhamou
Keyword(s):  
Fusarium Oxysporum ◽  
Plant Protection ◽  
Host Cells ◽  
Root Pathogen ◽  
Tomato Plants ◽  
Enhanced Resistance ◽  
Infected Root ◽  
Physical Barriers ◽  
Wall Appositions ◽  
Root Tissues

Chitosan, a polymer of β-1,4-d-glucosamine derived from crabshell chitin, was applied to tomato plants before inoculation with the root pathogen Fusarium oxysporum f.sp. radicis-lycopersici. Whether chitosan was applied by leaf spraying, root coating, or seed coating, it reduced the number of root lesions caused by the fungus and increased the formation of physical barriers in infected root tissues. Formation of wall appositions such as papillae and occlusion of xylem vessels with coating substances were among the most typical features of host reactions. Another type of response was the accumulation of globular structures and electron-opaque masses in host cells neighboring colonized areas. Gold cytochemistry revealed that callose and lignin-like material were the main structural compounds induced in response to chitosan treatment and infection. Biochemical investigations showed that PR proteins as well as enzymes of the secondary metabolism were also significantly induced. The potential of chitosan as a biocontrol compound is discussed in relation to its ability to enhance plant protection against root pathogens.

Structural aspects of Ascochyta blight of lentil

1995 ◽  
Vol 73 (3) ◽  
pp. 485-497 ◽  
Author(s):  
S. J. Roundhill ◽  
B. A. Fineran ◽  
A. L. J. Cole ◽  
M. Ingerfeld
Keyword(s):  
Seed Quality ◽  
Ascochyta Blight ◽  
Light And Electron Microscopy ◽  
Middle Lamella ◽  
Infection Process ◽  
Epidermal Cells ◽  
Host Cells ◽  
Wall Material ◽  
Structural Level ◽  
Susceptible Host

Ascochyta fabae Speg. f.sp. lentis (Gossen et al. 1986) causes lesions on the leaf, stem, and pod of lentil (Lens culinaris Medik.), thereby reducing seed quality and yield. Lesion formation was studied in two cultivars, Laird and Invincible, using light and electron microscopy of intact and excised leaves and stems inoculated with spore suspension. Spores germinated usually within 6 h of inoculation and germ tubes grew for varying distances along the leaf surface before forming an appressorium, sometimes within less than 10 h. A penetration peg then either directly entered the underlying epidermal cell, or grew as a subcuticular hypha for a short distance before entering the cell. The first response of epidermal cells to presence of the fungus was an aggregation of cytoplasm abutting the site of infection. This was followed closely by deposition of a papilla. Some relatively thick papillae were seen at 29 h postinoculation. The fungus then grew into the papilla and formed an infection vesicle. In susceptible host cells, the protoplasm became necrotic before hyphae grew into the lumen of the cell from the infection vesicle. In more resistant cells, the infection vesicle often became surrounded by electron-dense wall material developed by the host. The fungus remained in susceptible epidermal cells for up to 4 days, amongst remnants of the protoplast, before spreading to the adjacent mesophyll. Hyphae grew into intercellular spaces of the mesophyll and remained there for 2 – 3 days before penetrating the cells. The mesophyll reacted in a similar way to infection as did the epidermis, with only host cells close to the fungus becoming affected. Cultivar Laird was found to be less susceptible to infection than cv. Invincible. At the structural level, the infection process was found to be similar except that in cv. Laird the infection vesicle more frequently became surrounded by electron-dense wall material formed by the host. In stem tissue of cv. Laird the middle lamella was also occasionally thickened with electron-dense material deposited on either side of it. After the degeneration of host tissue, pycnidia-bearing spores were formed 10 – 14 days after inoculation of the leaf. Key words: Ascochyta, lentil, ultrastructure, infection process.

scholarly journals Treatment with the Mycoparasite Pythium oligandrum Triggers Induction of Defense-Related Reactions in Tomato Roots When Challenged with Fusarium oxysporum f. sp. radicis-lycopersici

1997 ◽  
Vol 87 (1) ◽  
pp. 108-122 ◽  
Author(s):  
Nicole Benhamou ◽  
Patrice Rey ◽  
Mohamed Chérif ◽  
John Hockenhull ◽  
Yves Tirilly
Keyword(s):  
Plant Defense ◽  
Fusarium Oxysporum ◽  
Host Cell ◽  
Cell Walls ◽  
Pythium Oligandrum ◽  
Tomato Plants ◽  
Host Cytoplasm ◽  
Defense Reactions ◽  
Tomato Roots ◽  
Root Tissues

The influence exerted by the mycoparasite Pythium oligandrum in triggering plant defense reactions was investigated using an experimental system in which tomato plants were infected with the crown and root rot pathogen Fusarium oxysporum f. sp. radicis-lycopersici. To assess the antagonistic potential of P. oligandrum against F. oxysporum f. sp. radicis-lycopersici, the interaction between the two fungi was studied by scanning and transmission electron microscopy (SEM and TEM, respectively). SEM investigations of the interaction region between the fungi demonstrated that collapse and loss of turgor of F. oxysporum f. sp. radicis-lycopersici hyphae began soon after close contact was established with P. oligandrum. Ultrastructural observations confirmed that intimate contact between hyphae of P. oligandrum and cells of the pathogen resulted in a series of disturbances, including generalized disorganization of the host cytoplasm, retraction of the plasmalemma, and, finally, complete loss of the protoplasm. Cytochemical labeling of chitin with wheat germ agglutinin (WGA)/ovomucoid-gold complex showed that, except in the area of hyphal penetration, the chitin component of the host cell walls was structurally preserved at a time when the host cytoplasm had undergone complete disorganization. Interestingly, the same antagonistic process was observed in planta. The specific labeling patterns obtained with the exoglucanase-gold and WGA-ovomucoid-gold complexes confirmed that P. oligandrum successfully penetrated invading cells of the pathogen without causing substantial cell wall alterations, shown by the intense labeling of chitin. Cytological investigations of samples from P. oligandrum-inoculated tomato roots revealed that the fungus was able to colonize root tissues without inducing extensive cell damage. However, there was a novel finding concerning the structural alteration of the invading hyphae, evidenced by the frequent occurrence of empty fungal shells in root tissues. Pythium ingress in root tissues was associated with host metabolic changes, culminating in the elaboration of structural barriers at sites of potential fungal penetration. Striking differences in the extent of F. oxysporum f. sp. radicis-lycopersici colonization were observed between P. oligandrum-inoculated and control tomato plants. In control roots, the pathogen multiplied abundantly through much of the tissues, whereas in P. oligandrum-colonized roots pathogen growth was restricted to the outermost root tissues. This restricted pattern of pathogen colonization was accompanied by deposition of newly formed barriers beyond the infection sites. These host reactions appeared to be amplified compared to those seen in nonchallenged P. oligandrum-infected plants. Most hyphae of the pathogen that penetrated the epidermis exhibited considerable changes. Wall appositions contained large amounts of callose, in addition to be infiltrated with phenolic compounds. The labeling pattern obtained with gold-complexed laccase showed that phenolics were widely distributed in Fusarium-challenged P. oligandrum-inoculated tomato roots. Such compounds accumulated in the host cell walls and intercellular spaces. The wall-bound chitin component in Fusarium hyphae colonizing P. oligandrum-inoculated roots was preserved at a time when hyphae had undergone substantial degradation. These observations provide the first convincing evidence that P. oligandrum has the potential to induce plant defense reactions in addition to acting as a mycoparasite.

The illustrated life cycle of Microbotryum on the host plant Silene latifolia

Botany ◽  
2010 ◽  
Vol 88 (10) ◽  
pp. 875-885 ◽  
Author(s):  
Angela Maria Schäfer ◽  
Martin Kemler ◽  
Robert Bauer ◽  
Dominik Begerow
Keyword(s):  
Life Cycle ◽  
Light And Electron Microscopy ◽  
Laboratory Data ◽  
Infection Process ◽  
Host Cells ◽  
Silene Latifolia ◽  
Long Distance ◽  
Biological Studies ◽  
Plant Parasitic

The plant-parasitic genus Microbotryum (Pucciniomycotina) has been used as a model for various biological studies, but fundamental aspects of its life history have not been documented in detail. The smut fungus is characterized by a dimorphic life cycle with a haploid saprophytic yeast-like stage and a dikaryotic plant-parasitic stage, which bears the teliospores as dispersal agents. In this study, seedlings and flowers of Silene latifolia Poir. (Caryophyllaceae) were inoculated with teliospores or sporidial cells of Microbotryum lychnidis-dioicae (DC. ex Liro) G. Deml & Oberw. and the germination of teliospores, the infection process, and the proliferation in the host tissue were documented in vivo using light and electron microscopy. Although germination of the teliospore is crucial for the establishment of Microbotryum, basidium development is variable under natural conditions. In flowers, where the amount of nutrients is thought to be high, the fungus propagates as sporidia, and mating of compatible cells takes place only when flowers are withering and nutrients are decreasing. On cotyledons (i.e., nutrient-depleted conditions), conjugation occurs shortly after teliospore germination, often via intrapromycelial mating. After formation of an infectious hypha with an appressorium, the invasion of the host occurs by direct penetration of the epidermis. While the growth in the plant is typically intercellular, long distance proliferation seems mediated through xylem tracheary elements. At the beginning of the vegetation period, fungal cells were found between meristematic shoot host cells, indicating a dormant phase inside the plant. By using different microscopy techniques, many life stages of Microbotryum are illustrated for the first time, thereby allowing new interpretations of laboratory data.

scholarly journals An endometrial organoid model of Chlamydia-epithelial and immune cell interactions

2020 ◽  
Author(s):  
Lee Dolat ◽  
Raphael H. Valdivia
Keyword(s):  
Epithelial Cell ◽  
Cell Biology ◽  
Immune Cell ◽  
Three Dimensional ◽  
Time Lapse ◽  
Cell Types ◽  
Infection Process ◽  
Host Cells ◽  
Cell Diversity ◽  
Intracellular Organelles

ABSTRACTOur understanding of how the obligate intracellular bacterium Chlamydia trachomatis reprograms the cell biology of host cells in the upper genital tract is largely based on observations made in cell culture with transformed epithelial cell lines. Here we describe a primary spherical organoid system derived from endometrial tissue to recapitulate epithelial cell diversity, polarity, and ensuing responses to Chlamydia infection. Using high-resolution and time-lapse microscopy, we catalogue the infection process in organoids from invasion to egress, including the reorganization of the cytoskeleton and positioning of intracellular organelles. We show this model is amenable to screening C. trachomatis mutants for defects in the fusion of pathogenic vacuoles, the recruitment of intracellular organelles, and inhibition of cell death. Moreover, we reconstructed a primary immune cell response by co-culturing infected organoids with neutrophils, and determined that the effector TepP limits the recruitment of neutrophils to infected organoids. Collectively, our model details a system to study the cell biology of Chlamydia infections in three dimensional structures that better reflect the diversity of cell types and polarity encountered by Chlamydia upon infection of their animal hosts.Summary statement3D endometrial organoids to model Chlamydia infection and the role of secreted virulence factors in reprogramming host epithelial cells and immune cell recruitment

scholarly journals Differently Directional Effects of Tebuconazole-Based Disinfectant of Seeds “Bunker” on the Growth of Winter Wheat Shoots and Roots

2020 ◽  
Vol 34 ◽  
pp. 3-19
Author(s):  
O. I. Grabelnych ◽  
◽  
E. A. Polykova ◽  
A. V. Korsukova ◽  
N. S. Zabanova ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Active Ingredient ◽  
Root Length ◽  
Thiobarbituric Acid ◽  
Shoot Length ◽  
Plant Diseases ◽  
Initial Stage ◽  
Significant Stimulation ◽  
Chlorophylls A And B ◽  
Root Tissues

Derivatives of a triazole are used not only as fungicides to prevent infection of plants, but also for treatment. These drugs are actively used against plant diseases caused by basidiomycetes, ascomycetes, and some deuteromycetes. Due to their chemical stability, they have a long-term protective effect, and their solubility in water ensures their movement from the roots to the aerial part of plants. The aim of this work was to study the effect of seed treatment with tebuconazole-containing preparation “Bunker” on the growth of shoots and roots of winter wheat in the light and physiological and biochemical parameters. We used a fungicide of prophylactic and therapeutic action tebuconazole-containing seed treater “Bunker” (August, Russia), the active ingredient of which is tebuconazole (60 g/L). The shoot length and total root length, wet and dry biomass, as well as the content of photosynthetic pigments, reactive oxygen species – hydrogen peroxide (H2O2) and lipid peroxidation products (LPO) reacting with thiobarbituric acid (TBA-RP) in the tissues of shoots and roots were analyzed. The content of chlorophylls a and b and carotenoids in the extract was determined spectrophotometrically at wavelengths of 665, 649, and 440 nm, respectively. The obtained results indicate that the action of the drug is aimed at inhibiting the growth of shoots and reducing the ratio of shoot length to root length, while on the 7-9th day of growth, the effectiveness of its action is higher, and the most significant effect is exerted by an increased dose of the disinfectant (1.5 μL/g). It was found statistically significant stimulation of root growth on the 9th day of cultivation, regardless of the dose of the dressing agent. Despite the significant growth-inhibiting effect, treatment with Bunker was not accompanied by activation of oxidative processes in shoot tissues, with the exception of an increase in the content of H2O2 and TBA-RP at the initial stage of growth (5 days). In root tissues, the content of H2O2 and TBA did not change under the action of the studied preparation. No differences in the content of chlorophylls a and b and carotenoids in the tissues of wheat shoots after treatment with the studied fungicide were found. Based on the data obtained, it can be concluded that seed dressing agents containing tebuconazole as an active ingredient can be used to ensure plant resistance to moisture deficiency and improve mineral nutrition.

Characteristics of a disease of Sphagnum fuscum caused by Scleroconidioma sphagnicola

2001 ◽  
Vol 79 (10) ◽  
pp. 1217-1224 ◽  
Author(s):  
A Tsuneda ◽  
M H Chen ◽  
R S Currah
Keyword(s):  
Cell Wall ◽  
Fungal Pathogen ◽  
Infected Leaf ◽  
Disease Development ◽  
Cortical Cells ◽  
Necrotrophic Pathogen ◽  
Sphagnum Fuscum ◽  
Entire Plant ◽  
Host Cell Wall ◽  
Advanced Stages

Scleroconidioma sphagnicola Tsuneda, Currah & Thormann, a dematiaceous hyphomycetous fungus, was found to cause a disease of Sphagnum fuscum (Schimp.) Klinggr. Hyphae of S. sphagnicola penetrated into chlorophyllose cells of host leaves and caused degeneration of chloroplasts, resulting in chlorosis of the infected leaves. Parasite hyphae often grew inside the host cell wall, and cavities were created around the hyphae. The invaded cell wall of Sp. fuscum appeared swollen and showed wavy deformation. In advanced stages of disease development, infected leaf chlorophyllose cells and stem cortical cells were necrotic and the entire plant became brown, shriveled, and brittle. Hyphae of S. sphagnicola began to form microsclerotia during early stages of disease development. Microsclerotia either formed conidiogenous cells on their surface or remained metabolically inactive and did not form conidiogenous cells. It was concluded that S. sphagnicola is a necrotrophic pathogen of Sp. fuscum, and its morphological and phenological features show remarkable adaptations for dispersal and colonization as a pathogen in bog habitats.Key words: moss, fungal pathogen, pathogenesis, chlorosis, necrosis, microsclerotia.

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