Host–parasite interfaces in a resistant and a susceptible cultivar of Solanum tuberosum inoculated with Phytophthora infestans: leaf tissue

1976 ◽  
Vol 54 (16) ◽  
pp. 1956-1970 ◽  
Author(s):  
Hans R. Hohl ◽  
Elisabeth Suter
Keyword(s):  
Phytophthora Infestans ◽  
Light And Electron Microscopy ◽  
Potato Cultivar ◽  
Leaf Tissue ◽  
Tissue Level ◽  
Fungal Hypha ◽  
Susceptible Cultivar ◽  
Susceptible Host ◽  
Focus Of Infection ◽  
Host Parasite

Host–parasite interfaces in leaves from a resistant (Eba) and a susceptible (Bintje) potato cultivar inoculated with Phytophthora infestans were studied using light and electron microscopy. Host penetration occurs similarly in both cultivars either through stomata or directly through the epidermis. In the susceptible host the fungus spreads throughout the tissue intercellularly and transcellularly, whereas in the resistant host it remains confined to the focus of infection. Yet in both cases live, normal-appearing hyphae can be observed even after 5 days. The appearance of haustoria in both cultivars is similar: they are either surrounded by an extrahaustorial matrix alone or in combination with wall appositions (collars or encasements). Structures with cytological features between those of haustoria and transcellular hyphae were also recorded, indicating a variety of host–parasite interactions within leaf tissue. Sporulation has been observed on the susceptible cultivar but not on the resistant one. The results suggest that cellular reactions against the intruding fungal hypha are qualitatively similar in both cultivars but that at the tissue level the intercellular spread of the pathogen and its sporulation are prevented in the resistant host but not in the susceptible host.

Host–parasite interfaces in a resistant and a susceptible cultivar of Solanum tuberosum inoculated with Phytophthora infestans: tuber tissue

1976 ◽  
Vol 54 (9) ◽  
pp. 900-912 ◽  
Author(s):  
Hans R. Hohl ◽  
Peter Stössel
Keyword(s):  
Solanum Tuberosum ◽  
Phytophthora Infestans ◽  
Susceptible Cultivar ◽  
Potato Tubers ◽  
Tuber Tissue ◽  
Susceptible Host ◽  
Transmission Electron ◽  
Wall Appositions ◽  
Host Parasite ◽  
Extrahaustorial Matrix

Host–parasite interfaces in potato tubers (Solanum tuberosum) of a resistant (Eba) and a susceptible (Bintje) cultivar inoculated with Phytophthora infestans were studied with transmission electron microscopy. In the resistant host the fungal haustoria are typically small and surrounded by an electron-dense extrahaustorial matrix and electron-transparent wall appositions, normally in form of complete encasements. Wall appositions are generally lacking in the susceptible host or occasionally are found as a collar at the base of the rather large haustorium, which is surround by a well developed extrahaustorial matrix. Since wall appositions probably contain largely a callose-like material, potential roles of fungal glucanases in this host–parasite system are discussed.

Ultrastructure of the interaction between Pyrenophora teres and a susceptible barley host

1979 ◽  
Vol 57 (1) ◽  
pp. 40-47 ◽  
Author(s):  
L. Van Caeseele ◽  
J. Grumbles
Keyword(s):  
Epidermal Cell ◽  
Light And Electron Microscopy ◽  
Leaf Tissue ◽  
Pyrenophora Teres ◽  
Barley Cultivar ◽  
Mesophyll Cells ◽  
Initial Penetration ◽  
Cell Layers ◽  
Epidermal Cell Wall ◽  
Host Parasite

Host–-parasite interfaces in leaves of a susceptible barley cultivar inoculated with Pyrenophora teres were studied using light and electron microscopy. Entry into the host rarely occurred through stomata, normal entry was by penetration into epidermal cells. Disruption of cell contents was evident in all initial penetration sites. After penetrating the epidermal cell, the fungus produced a large infection vesicle which gave rise to one or sometimes two intracellular hyphae. Hyphae spread down through the leaf tissue intracellularly for one or two cell layers and intercellularly thereafter. A septum, coincident with the external epidermal cell wall, was present in the infection peg located between the appressorium and the vesicle. Prior to leaving the epidermal cell, hyphae swelled to produce appressorium-like structures. These hyphae were sometimes septate at the point of exit. At sites where the infection had penetrated only four or five cell layers deep, the cellular contents of the mesophyll cells were relatively unaffected despite the presence of intercellular hyphae. However, when hyphae occasionally penetrated a host cell, gross disruption of their contents was apparent.

Internal gas atmospheres, ethanol, and leakage of electrolytes from a flood-tolerant and a flood-susceptible sweet potato cultivar as influenced by anaerobiosis

1983 ◽  
Vol 61 (12) ◽  
pp. 3399-3404 ◽  
Author(s):  
Ling A. Chang ◽  
Larry K. Hammett ◽  
David M. Pharr
Keyword(s):  
Sweet Potato ◽  
Electrolyte Leakage ◽  
Potato Cultivar ◽  
Enriched Environment ◽  
Potato Cultivars ◽  
Susceptible Cultivar ◽  
Low Concentrations ◽  
Gas Atmosphere ◽  
High Concentrations

The postanaerobic behavior of sweet potato roots from a flood-tolerant cultivar, 'Centennial,' and a flood-susceptible cultivar, 'Caromex,' was studied. High concentrations of CO2 and low concentrations of O2 were present in the internal atmosphere of 'Caromex' roots even after the anaerobically pretreated roots were restored to air for a few days, whereas in 'Centennial,' the internal gas atmosphere was less affected by anoxia. Ethanol accumulation in 'Caromex' was consistently higher than in 'Centennial,' and the postanaerobic changes were different between cultivars. An inducation of electrolyte leakage was observed from both cultivars immediately after roots were exposed to a CO2-enriched environment for 48 h. The leakage became greater in 'Caromex' after a 3-day aerobic exposure. In 'Centennial,' leakage of electrolytes due to CO2 treatment diminished at the end of 3 days. Application of ethanol to the discs had no immediate effect on electrolyte leakage in either cultivar under a N2 environment. However, anaerobiosis alone resulted in higher electrolyte leakage. It remains to be determined that the postanaerobic patterns of 'Caromex' and 'Centennial' are characteristic of flood-susceptible and flood-tolerant sweet potato cultivars in general.

Trophoblast transferrin and transferrin receptors in the host–parasite relationship of human pregnancy

1979 ◽  
Vol 204 (1154) ◽  
pp. 83-97 ◽  
Keyword(s):  
Iron Transport ◽  
Light And Electron Microscopy ◽  
Biological Significance ◽  
Transformed Cells ◽  
Specific Factor ◽  
Transferrin Receptors ◽  
Immunological Recognition ◽  
Parasite Relationship ◽  
Cellular Replication ◽  
Host Parasite

Transferrin and specific transferrin receptors are demonstrated on the microvillous surface of syncytiotrophoblast in human immature and term placentae by immunohistological techniques with the use of light and electron microscopy. That the distribution of transferrin is limited to the materno-foetal interface supports the hypothesis that binding of maternal transferrin to trophoblast receptors is involved in the process of iron transport to the foetus. Parallel studies with baboon placentae demonstrate the presence of trophoblast receptors which bind both baboon and human transferrin, thereby putting forward an experimental model which might be used to test the biological significance of placental transferrin receptors in primates. In addition, investigation of a large number of human cell lines shows that many transformed cells, but no normal cells (such as blood lymphocytes) or cells from primary culture (such as neonatal foreskin fibroblasts), possess the ability to bind transferrin to their membranes. These findings suggest that transferrin receptors may play important biological roles in addition to that of iron transport from mother to foetus. One such role could be the limitation of iron in intervillous spaces, thus depriving iron-requiring microorganisms of iron, hence serving as a non-specific factor of resistance for placentae. Another role for foetal transferrin receptors on trophoblasts could be to bind maternal transferrin at the materno-foetal interface, thus frustrating maternal immunosurveillance. This is similar to a mechahism used by schistosomes in the host-parasite relation where host proteins are bound by the parasite to escape immunological recognition. The presence of transferrin receptors on transformed cells suggests that this mechanism might also be employed by tumour cells. Finally, in view of previous studies which show that transferrin is required by stimulated lymphocytes to pass from the G 1 to the S phase of cellular replication, it is proposed that trophoblast transferrin receptors could limit the amount of transferrin in intervillous spaces and thus impede the proliferation and possible cytotoxicity of maternal activated lymphocytes at the materno-foetal interface.

Induction of a proteinase K inhibitor in a potato cultivar with a high degree of field resistance against Phytophthora infestans

2000 ◽  
Vol 109 (1) ◽  
pp. 14-20 ◽  
Author(s):  
Mariana L. Feldman ◽  
Claudia R. Oliva ◽  
Claudia A. Casalongué ◽  
Gustavo R. Daleo
Keyword(s):  
Phytophthora Infestans ◽  
Potato Cultivar ◽  
Field Resistance ◽  
Proteinase K ◽  
High Degree

Synchronization of host-parasite cycles by means of diapause: host influence and parasite response to involuntary host shifting

Parasitology ◽  
2008 ◽  
Vol 135 (11) ◽  
pp. 1343-1352 ◽  
Author(s):  
M. A. CALERO-TORRALBO ◽  
F. VALERA
Keyword(s):  
Ecological Factors ◽  
Susceptible Host ◽  
Incubation Periods ◽  
Carnus Hemapterus ◽  
Merops Apiaster ◽  
The Mean ◽  
Rate Of Emergence ◽  
The One ◽  
Host Parasite ◽  
Host Influence

SUMMARYMany parasites require synchronization of their infective phases with the appearance of susceptible host individuals and, for many species, diapause is one of the mechanisms contributing to such coincidence. A variety of ecological factors, like changes in host temperature produced by involuntary host shifting (substitution of the usual host by an infrequent one), can modify host-parasite synchronization of diapausing ectoparasites of endothermic species. To understand the influence of host shifting on the mechanisms of parasite synchronization, we conducted experiments using the system formed by the ectoparasitic fly Carnus hemapterus and its avian hosts. We simulated the occurrence of the usual host and natural cases of host shifting by exposing overwintering carnid pupae from Bee-eater nests (Merops apiaster) to the earlier incubation periods of two Carnus host species that frequently reoccupy Bee-eater nests. Pupae exposed to host shifting treatments advanced the mean date of emergence and produced an earlier and faster rate of emergence in comparison with pupae exposed both to the control (absence of any host) and Bee-eater treatments. The effect was more evident for the treatment resembling the host with the most dissimilar phenology to the one of the usual host. Our results show that host temperature is an environmental cue used by this nest-dwelling haematophagous ectoparasite and reveal that Carnus hemapterus has some potential to react to involuntary host shifting by means of plasticity in the termination of diapause.

Host life-history variation in response to parasitism

Parasitology ◽  
1985 ◽  
Vol 90 (1) ◽  
pp. 205-216 ◽  
Author(s):  
D. J. Minchella
Keyword(s):  
Genetic Variation ◽  
Life History ◽  
Parasitic Infection ◽  
Host Susceptibility ◽  
Life History Variation ◽  
Susceptible Host ◽  
Finite Set ◽  
Host Life ◽  
Host Parasite ◽  
Parasite Populations

Over half of all living species of plants and animals are parasitic, which by definition involves intimate association with and unfavourable impact on hosts (Price, 1980). This paper will only consider parasites whose ‘unfavourable impact’ adversely affects the birth and/or mortality rates of their hosts (Anderson, 1978). Most organisms are potential hosts and must deal with the problem of parasitism. The probability of parasitic infection of a host is influenced by both environmental and genetic factors. Traditionally it was assumed that a host was either resistant or susceptible to a particular parasite and therefore the interaction between a parasite and potential host had only two possible outcomes: either the resistant host rebuffed the parasitic attack and remained uninfected or the parasite successfully invaded and significantly reduced the reproductive success of the susceptible host. This approach, however, ignored the intraspecific genetic variation present within both host and parasite populations (Wakelin, 1978). Since the outcome is determined by the interaction of a finite set of host genes and parasite genes, genetic variation in host susceptibility and parasite infectivity (Richards, 1976; Wakelin, 1978) suggests that more than two outcomes are possible. Variation in host and parasite genomes does not begin and end at the susceptibility/infectivity loci. Other genes may also influence the outcome of host–parasite interactions by altering the life-history patterns of hosts and parasites, and lead to a variety of outcomes.

scholarly journals Development and ultrastructure observations of secondary hyphae of Podosphaera leucotricha on apple cultivars of varying susceptibility to powdery mildew

2017 ◽  
Vol 38 (SI 2 - 6th Conf EFPP 2002) ◽  
pp. 425-428
Author(s):  
E. Rakhimova
Keyword(s):  
Electron Microscopy ◽  
Powdery Mildew ◽  
Light And Electron Microscopy ◽  
Dense Material ◽  
Podosphaera Leucotricha ◽  
Powdery Mildew Fungus ◽  
Full Complement ◽  
Apple Cultivars ◽  
Host Parasite

The development and ultrastructure feature of secondary hyphae of Podosphaera leucotricha were studied using light and electron microscopy. The percentage of development and length of secondary hyphae, differed in compatible and incompatible combinations. In compatible host-parasite combinations, hyphal cells of powdery mildew fungus contained a full complement of fungal organelles. There were differences of hyphal ultrastructure in compatible and incompatible host-parasite combinations, the main one was the appearance of dense material inside the nucleus, in the cytoplasm, and a few mitochondria.

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