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Intercellular hypha (IH) of Melampsora euphorbiae in the intercellular space (IS) of leaf tissue of Euphorbia peplus. Note the septum (S), haustorial mother cell (HMC) and penetration peg (arrow). Bar l 2 µm. Fig. 2. Cell of intercellular hypha (IH), following PATCHSP procedure, showing two nuclei (n). Note that the hyphal wall (arrow) is more intensely stained than the host cell wall (HW). Bar l 0n5 µm. Figs 3-4. Penetration of E. peplus mesophyll cells by M. euphorbiae. Fig. 3. Haustorium mother cell (HMC) in close attachment to the host cell wall (HW) at the penetration site, where a tiny peg (arrow) is starting to form. The HMC contains nucleus (n), endoplasmic reticulum (er) and ribosome-rich cytoplasm. UA\LC staining. Bar l 0n5 µm. Fig. 4. Point of entry of penetration peg (pg) from haustorium mother cell (HMC) through the host cell wall (HW). The host wall and collar (CO) show similar density of staining after PATCHSP procedure. Note the continuity of plasmalemma (arrow) in HMC and inner layer of the penetration peg. Note also the constriction (arrowhead) of the penetration peg. Bar l 0n25 µm.
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Ultrastructural and cytochemical investigations of the interaction between Melampsora euphorbiae and its host Euphorbia peplus are described. Two types of collar around the haustorial neck could be recognized, corresponding to the maturity of the haustorium. Using various lectin-gold complexes as probes, different glycoconjugates were revealed in t...
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... hyphae of the dikaryotic phase of M. euphorbiae in infected leaf tissue of E. peplus were septate ( Fig. 1) and usually showed two nuclei per cell (Fig. 2) as well as the normal cytoplasmic organelles of eukaryotic cells (Figs 1-3). Haustoria developed from specialized haustorium mother cells (HMC) which adhered to the host cell wall (Fig. 3). A very slender penetration hypha (180-200 nm diam.) emerged from the HMC at the point of contact ...
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... hyphae of the dikaryotic phase of M. euphorbiae in infected leaf tissue of E. peplus were septate ( Fig. 1) and usually showed two nuclei per cell (Fig. 2) as well as the normal cytoplasmic organelles of eukaryotic cells (Figs 1-3). Haustoria developed from specialized haustorium mother cells (HMC) which adhered to the host cell wall (Fig. 3). ...
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... the probes listed in Table 1, specific sugar residues were detected and localized in fungal (Table 2) and host cells (Table 3). Incubation of infected Euphorbia leaves with WGA\ovomucoid-gold complex, resulted in labelling of chitin (a β-1,4-linked N-acetylglucosamine polymer) in hyphal walls, more intensively on septa than on longitudinal walls (Fig. 10). Urediniospore walls were labelled (Figs 11, 12), but 15 ...
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... of infected Euphorbia leaves with WGA\ovomucoid-gold complex, resulted in labelling of chitin (a β-1,4-linked N-acetylglucosamine polymer) in hyphal walls, more intensively on septa than on longitudinal walls (Fig. 10). Urediniospore walls were labelled (Figs 11, 12), but 15 16 ...
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... 15-19. Rust-infected leaf tissue of E. peplus following treatment with ConA-gold complex. Fig. 15. Glycogen particles (gp) of the hyphae under the uredinium are heavily labelled. Bar l 0n5 µm. Fig. 16. Glycogen particles of intercellular hypha (IH) also heavily labelled but no label occurs over fungal wall (arrowhead). Bar l 1 µm. Fig. 17. Strong positive reaction of starch grain (arrowhead) in host chloroplast but not over walls ...
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... 15-19. Rust-infected leaf tissue of E. peplus following treatment with ConA-gold complex. Fig. 15. Glycogen particles (gp) of the hyphae under the uredinium are heavily labelled. Bar l 0n5 µm. Fig. 16. Glycogen particles of intercellular hypha (IH) also heavily labelled but no label occurs over fungal wall (arrowhead). Bar l 1 µm. Fig. 17. Strong positive reaction of starch grain (arrowhead) in host chloroplast but not over walls (arrow) of haustorium (H) or host cell (HW). Bar l 0n5 µm. Fig. 18. Some labelling over cytoplasm of ...
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... 15-19. Rust-infected leaf tissue of E. peplus following treatment with ConA-gold complex. Fig. 15. Glycogen particles (gp) of the hyphae under the uredinium are heavily labelled. Bar l 0n5 µm. Fig. 16. Glycogen particles of intercellular hypha (IH) also heavily labelled but no label occurs over fungal wall (arrowhead). Bar l 1 µm. Fig. 17. Strong positive reaction of starch grain (arrowhead) in host chloroplast but not over walls (arrow) of haustorium (H) or host cell (HW). Bar l 0n5 µm. Fig. 18. Some labelling over cytoplasm of intercellular hypha (IH) but very little over wall. Fungal vacuoles (v) and lipid droplets (L) are unlabelled. Bar l 0n5 µm. Fig. 19. Membranes ...
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... uredinium are heavily labelled. Bar l 0n5 µm. Fig. 16. Glycogen particles of intercellular hypha (IH) also heavily labelled but no label occurs over fungal wall (arrowhead). Bar l 1 µm. Fig. 17. Strong positive reaction of starch grain (arrowhead) in host chloroplast but not over walls (arrow) of haustorium (H) or host cell (HW). Bar l 0n5 µm. Fig. 18. Some labelling over cytoplasm of intercellular hypha (IH) but very little over wall. Fungal vacuoles (v) and lipid droplets (L) are unlabelled. Bar l 0n5 µm. Fig. 19. Membranes of myelin-like structure in host cell are heavily labelled. Bar l 1 ...
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... Bar l 1 µm. Fig. 17. Strong positive reaction of starch grain (arrowhead) in host chloroplast but not over walls (arrow) of haustorium (H) or host cell (HW). Bar l 0n5 µm. Fig. 18. Some labelling over cytoplasm of intercellular hypha (IH) but very little over wall. Fungal vacuoles (v) and lipid droplets (L) are unlabelled. Bar l 0n5 µm. Fig. 19. Membranes of myelin-like structure in host cell are heavily labelled. Bar l 1 ...
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... spines embedded in the outer wall of mature urediniospores gave no chitin reaction. The haustorium wall, extrahaustorial matrix and extrahaustorial membrane (Fig. 13) as well as primary walls of host cells (Figs 10, 14) were, however, almost free of labelling. Cytoplasm, mitochondria, oil drops and vacuoles of both fungus and host remained unlabelled (Figs 10, 14). Surprisingly, however, this probe also bound to the secondary wall of xylem vessels (Fig. 14). The density of distribution of gold ...
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... spines embedded in the outer wall of mature urediniospores gave no chitin reaction. The haustorium wall, extrahaustorial matrix and extrahaustorial membrane (Fig. 13) as well as primary walls of host cells (Figs 10, 14) were, however, almost free of labelling. Cytoplasm, mitochondria, oil drops and vacuoles of both fungus and host remained unlabelled (Figs 10, 14). ...
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... haustorium wall, extrahaustorial matrix and extrahaustorial membrane (Fig. 13) as well as primary walls of host cells (Figs 10, 14) were, however, almost free of labelling. Cytoplasm, mitochondria, oil drops and vacuoles of both fungus and host remained unlabelled (Figs 10, 14). Surprisingly, however, this probe also bound to the secondary wall of xylem vessels (Fig. 14). ...
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... extrahaustorial matrix and extrahaustorial membrane (Fig. 13) as well as primary walls of host cells (Figs 10, 14) were, however, almost free of labelling. Cytoplasm, mitochondria, oil drops and vacuoles of both fungus and host remained unlabelled (Figs 10, 14). Surprisingly, however, this probe also bound to the secondary wall of xylem vessels (Fig. 14). The density of distribution of gold particles was greatly reduced over sections treated with WGA-gold complex preincubated with N-acetyl-chitotriose. When ConA gold conjugate was used to detect α--mannose and\or α--glucose residues, heavy binding was observed to the glycogen-like granules in the hyphal cytoplasm (Figs 15, 16), ...
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... however, this probe also bound to the secondary wall of xylem vessels (Fig. 14). The density of distribution of gold particles was greatly reduced over sections treated with WGA-gold complex preincubated with N-acetyl-chitotriose. When ConA gold conjugate was used to detect α--mannose and\or α--glucose residues, heavy binding was observed to the glycogen-like granules in the hyphal cytoplasm (Figs 15, 16), starch grains in host cell (Fig. 17), and to a myelin-like profile of concentric membranes (Fig. 19), but not to host or fungal walls (Figs 16-18). Weak labelling was also observed in the cytoplasm of the fungus (Fig. 18). ...
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... of distribution of gold particles was greatly reduced over sections treated with WGA-gold complex preincubated with N-acetyl-chitotriose. When ConA gold conjugate was used to detect α--mannose and\or α--glucose residues, heavy binding was observed to the glycogen-like granules in the hyphal cytoplasm (Figs 15, 16), starch grains in host cell (Fig. 17), and to a myelin-like profile of concentric membranes (Fig. 19), but not to host or fungal walls (Figs 16-18). Weak labelling was also observed in the cytoplasm of the fungus (Fig. 18). Treatment of the sections with ConA-gold complex, previously absorbed to α--mannose or α--glucose, gave negative results. After incubation with the ...
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... treated with WGA-gold complex preincubated with N-acetyl-chitotriose. When ConA gold conjugate was used to detect α--mannose and\or α--glucose residues, heavy binding was observed to the glycogen-like granules in the hyphal cytoplasm (Figs 15, 16), starch grains in host cell (Fig. 17), and to a myelin-like profile of concentric membranes (Fig. 19), but not to host or fungal walls (Figs 16-18). Weak labelling was also observed in the cytoplasm of the fungus (Fig. 18). Treatment of the sections with ConA-gold complex, previously absorbed to α--mannose or α--glucose, gave negative results. After incubation with the Ricinus communis agglutinin I (RCA I )-gold complex, to detect ...
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... however, this probe also bound to the secondary wall of xylem vessels (Fig. 14). The density of distribution of gold particles was greatly reduced over sections treated with WGA-gold complex preincubated with N-acetyl-chitotriose. When ConA gold conjugate was used to detect α--mannose and\or α--glucose residues, heavy binding was observed to the glycogen-like granules in the hyphal cytoplasm (Figs 15, 16), starch grains in host cell (Fig. 17), and to a myelin-like profile of concentric membranes (Fig. 19), but not to host or fungal walls (Figs 16-18). Weak labelling was also observed in the cytoplasm of the fungus (Fig. 18). ...
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... α--mannose and\or α--glucose residues, heavy binding was observed to the glycogen-like granules in the hyphal cytoplasm (Figs 15, 16), starch grains in host cell (Fig. 17), and to a myelin-like profile of concentric membranes (Fig. 19), but not to host or fungal walls (Figs 16-18). Weak labelling was also observed in the cytoplasm of the fungus (Fig. 18). Treatment of the sections with ConA-gold complex, previously absorbed to α--mannose or α--glucose, gave negative results. After incubation with the Ricinus communis agglutinin I (RCA I )-gold complex, to detect α--galactose, an increase in labelling was observed in the walls of intercellular hyphae (Fig. 20), and in haustorial and ...
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... the Ricinus communis agglutinin I (RCA I )-gold complex, to detect α--galactose, an increase in labelling was observed in the walls of intercellular hyphae (Fig. 20), and in haustorial and host cell walls (Fig. 22). The vesicular structures inside intercellular hyphae identified as lomasomes (Littlefield & Heath, 1979) were heavily labelled ( Fig. 21) but other cytoplasmic components of both host and fungus were not significantly labelled (Figs 20-22). In a control test including previous adsorption of the RcA I -gold complex on -galactose, no labelling was ...
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... better evidence for the occurrence of chitin in plant cell walls, the specificity of WGA-ovomucoid-gold labelling of secondary wall material in E. peplus xylem vessels requires further investigation. The density of gold particles at this site (Fig. 14) and their absence from the primary walls, strikingly resemble the labelling of xylem elements in healthy roots of Hevea brasiliensis demonstrated by Nicole & Benhamou (1991). These observations and similar reports (Chamberland et al., 1995 ;Benhamou & Asselin, 1989) have been interpreted ...
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The aims of this study were to isolate trimethylamine (TMA)-resistant bacteria from waste of fish merchant, identify them, and investigate the efficiency of TMA removal by Euphorbia milii with and without inoculated bacteria. The best bacteria strain which was chosen from TMA utilization test was identified as Bacillus thuringiensis by 16S rRNA seq...
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... The majority of the rusts have a neckband on their dikaryotic haustorium (Rijkenberg and Truter 1973;Coffey 1976;Harder 1978;Borland and Mims 1980;Al-Khesraji and Losel 1981;Heath and Bonde 1983;Harder 1984;Longo and Bruscaglioni 1986;Baka 1992Baka , 1996aBaka , b, 2002Baka , 2014Losel 1992b, 1998). The neckband may serve as a seal to prevent an apoplastic flow of materials along the neck wall, according to theories put forth by Coffey et al. (1972) and Coffey (1976), or it may serve as a site of material exchange between the fungus and its host (Heath 1976;Baka and Losel 1998). There may be different haustorial morphologies (Rice 1927). ...
... Intercellular hyphae of the dikaryotic phase of M. euphorbiae in infected leaf tissue of Euphorbia peplus were septate and usually showed two nuclei per cell as well as the normal cytoplasmic organelles of eukaryotic cells (Baka and Losel 1998). Haustoria developed from specialized haustorium mother cells (HMC) which adhered to the host cell wall (Fig. 21a). ...
... Acknowledgments As the author of this chapter, I would like to thank Elsevier Publishing Company for granting me permission to use some of the previously published images of my papers to be included in this chapter. The published papers are: - Baka ZAM, Losel DM (1998) Ultrastructure and lectin-gold cytochemistry of the interaction between the rust fungus Melampsora euphorbiae and its host Euphorbia peplus. Mycol Res 102: 1387-1398. ...
In this chapter, the monokaryotic and dikaryotic haustoria of some rust fungi are compared. Generally, the pycnial and aecial stages of infection produce the first type, while the uredial and telial stages produce the second type. Plant pathogens called rust fungi can infect a variety of commercially significant crop species and make them diseased. The urediospore-derived dikaryotic stage penetrates plant tissue through stomata openings, grows between plant cells, and subsequently produces highly specialized D-haustoria inside mesophyll cells. The haustorial neck of this haustorium is greatly constricted at the penetration site and shows an electron-dense area, the neckband, on the neck wall. The basidiospore-derived-monokaryotic stage typically directly penetrates plant epidermal cells, producing an intracellular hypha, which then branches out into an intercellular mycelium, which develops intracellular M-haustoria. As a result, both growth phases result in the production of intracellular structures, or haustoria. The only plant structure that has been penetrated is the cell wall because the haustoria are still covered by the invaginated plant plasma membrane. The function of rust haustoria is also discussed.KeywordsRust fungiHaustoriumHaustorial mother cellMonokaryotic haustoriumDikaryotic haustoriumExtrahaustorial matrixExtrahaustorial membraneNeckbandNutrient uptake
... Previous electron micrographs showed that the uredial haustorium of P. poarum was surrounded by the host nucleus, separated from it by a narrow region of the cytoplasm (Al-Khesraji and Losel 1981). Littlefield and Bracker (1972) reported encasements were deposited from the host cell wall and also generated resistance against the specific host as documented by Baka and Losel (1998). Host wall-like material installation is induced by parasite invasion (Walles 1974) or after haustoria development in host cells (Mims and Glidewell 1978;Baka 1987). ...
This study investigated the impact of the rust fungus, Puccinia lagenophorae on its host, Senecio aegyptius using both light (LM) and transmission (TEM) electron microscopy. The chloroplast numbers decreased during the aecial and telial stages of the pathogen (53.7 and 56.6%, respectively). The nucleus volumes were increased during both stages (10.9 and 14.1%, respectively). Infected chloroplasts and nuclei showed changes in their shape and ultrastructure. Instead of the M-haustorium, a collar was created around the D-haustorium. A neck encasing developed in both types of necrotic haustoria. This encasement may serve as the host cell’s protection against toxins created after the death of haustoria. The severe changes in the chloroplasts and nuclei of this host plant after infection by this pathogen may give this pathogen the possibility of controlling this serious weed. Future research in the molecular mechanism may explore the biological control of weeds for local farm agroecology.
... Ultracytochemical studies on the localization of different carbohydrate fractions, particularly chitin, in the fungal cell wall and cell components have been conducted by many authors (Benhamou 1988;Baka and Lösel 1998). This localization may throw light on how the chitinolytic actinomycetes can be used as biocontrol agents against fungal phytopathogens. ...
Antagonistic actinomycete strains isolated from the environment are valuable tools for an eco-friendly, healthy, and safe control of phytopathogenic fungi. We have evaluated the culture filtrate of Streptomyces griseorubens E44G, an actinomycete strain isolated from soil, on the growth and ultrastructure of hyphal cells of the phytopathogenic fungus Fusarium oxysporum f. sp. lycopersici, the causal agent of Fusarium wilt disease of tomato. The effect of the Streptomyces culture filtrate on some of the carbohydrate fractions in the hyphal cell of the pathogen using gold-labeled lectin complexes was also elucidated. Of the concentrations of S. griseorubens E44G culture filtrate tested, the highest (400 μL) had the most potent antifungal effect on the mycelial growth of the fungus. At this concentration, some changes in the morphology of the fungal hyphae were observed by scanning electron microscopy, and a number of dramatic changes in the ultrastructure of the hyphal cells of the fungus were observed by transmission electron microscopy. Ultracytochemical localization of carbohydrate fractions of the hyphal cell of the fungus revealed the presence of a very high quantity of chitin in the cell wall which was digested following exposure to the culture filtrate of S. griseorubens E44G, indicating the presence of a chitinase enzyme in that filtrate. The ultracytochemical investigations also indicated the presence of mannose, glucose, and galactose in the fungal cell wall, as well as the absence of glucosides. Moreover, the fungal cell cytoplasm contained glucosides and galactose but not chitin. These results confirm that the chitinase enzyme was produced by S. griseorubens E44G and that this enzyme may play a role in the potential of this strain as an antifungal agent against F. oxysporum f. sp. lycopersici.
... This technique has been widely used to gain further insight into viral (van Lent & Verduin, 1991), bacterial (Brown & Mansfield, 1991; Boher et al ., 1996; Vian et al ., 1996; Murdoch et al ., 1999) and fungal (VandenBosch et al ., 1989; Bonfante-Fasolo & Perotto, 1991; Nicole & Benhamou, 1993; Chamberland, 1994; phenols (Grandmaison et al ., 1993; Boher et al ., 1996), cell wall degrading or stiffening enzymes (Benhamou et al ., 1991; Nicole et al ., 1992; Nicole et al ., 1994; Tenberge et al ., 1999; Hilaire et al ., 2001) and pectins (Golotte et al ., 1993; Nicole & Benhamou, 1993; Rodriguez-Galvez & Mendgen, 1995; Vian et al ., 1996; Murdoch et al ., 1999). In rust-infected plants, some work has been done to gain a more precise insight into changes in cell wall chemistry during the interaction between host and fungus, particularly along intracellular haustoria (Xu & Mendgen, 1997; Baka & Lösel, 1998). However, an extensive study of which cell wall components are degraded and which remain intact during the interaction of a host plant and a specific intercellular biotrophic pathogen is lacking. ...
The intercellular ascomycetous pathogen Cymadothea trifolii, causing sooty blotch of clover, proliferates within leaves of Trifolium spp. and produces a complex structure called interaction apparatus (IA) in its own hyphae. Opposite the IA the plant plasmalemma invaginates to form a bubble. Both structures are connected by a tube with an electron-dense sheath. Using immunocytochemistry on high-pressure frozen and freeze-substituted samples, we examined several plant and fungal cell wall components, including those in new host wall appositions at the interaction site, as well as a fungal polygalacturonase. Within the tube linking IA and host bubble, labelling was obtained for cellulose and xyloglucan but not for rhamnogalacturonan-I and homogalacturonans. The IA labelled for chitin and beta-1,3-glucans, and for a fungal polygalacturonase. Plant wall appositions reacted with antibodies against callose, xyloglucans and rhamnogalacturonan-I. Cymadothea trifolii partly degrades the host cell wall. Structural elements remain intact, but the pectin matrix is dissolved. A fungal polygalacturonase detected in the IA is probably a key factor in this process. Owing to the presence of chitin and beta-1,3-glucans, the IA itself is considered an apoplastic compartment.
This chapter throw the light on the interaction between the host and its rust infection. This interaction includes phosohatase activity, vascular infection, and ultracytochemical localization of carbohydrate fractions using gold-lectin conjugation method. Phosphatase activities have been localized cytochemically at haustorial-host interfaces of spermogonial-aecial and uredinial stages of the presented rust fungi. ATPase activity, similar to that of the wall-lining plasmalemma of the host cell, was associated with the extrahaustorial membrane of the filamentous monokaryotic (M) haustoria of the spermogonial-aecial infections but not with the dikaryotic (D-) haustoria of the uredinial infection. Aecial stages of P. lagenophora were accompanied by dense fungal growth in leaf veins of Senecio vulgaris host cells were penetrated by unspecialized, filamentous, fungal structures. No vascular infection by the dikaryon was found in the uredinial-telial phases of P. punctiformis on thistle leaves, although specialized D-haustoria were present with high frequency in mesophyll cells. These observations are consistent with the hypothesis that access to host translocates, afforded by vascular penetration, may compensate for the probably lower efficiency of the unspecialized filamentous haustoria found in spermogonial and aecial stages. Cytochemical investigations of the interaction between Melampsora euphorbiae and its host Euphorbia peplus are described. Using various lectin-gold complexes as probes, different glycoconjugates were revealed in the fungus and host. Chitin was found in walls of urediniospores and intercellular hyphae but not in haustoria. D-glucose and or D-mannose were strongly indicated in host starch grains and glycogen particles inside the intercellular hyphae, but only lightly in the fungal cytoplasm. Galactose residues and L-fucose were detected in fungal walls, more strongly in those of intercellular hyphae than haustoria. Galactose was also localized cytochemically in lomasome membranes of the fungus. β-glucosides were detected in the fibrillar wall material bordering intercellular spaces of host tissue.KeywordsRust fungiATP-ase activityVascular infection
Puccinia punctiformis
Puccinia lagenophorae
Uromyces euphorbiae
Lectin-gold complexes
The ultrastructure of intercellular hyphae and dikaryotic haustoria of Uromyces euphorbiae, and the host response to haustorial invasion was investigated. The intercellular hyphae share common characteristics with those of other uredinial stages of rust fungi. Three types of septa were recognized inside the intercellular hypha. This study showed that the extrahaustorial membrane was possibly formed before the development of the haustorium. The periodic acid-thiocharbohydrazide-silver proteinate technique showed that the haustorial mother cell wall at the penetration site, and the haustorial wall contained more carbohydrates than other fungal structures. In addition, the neckband, present around the haustorial neck, contains different material from those of the rest of the haustorial neck wall. The close associations of host organelles, such as the nucleus, chloroplasts, mitochondria, endoplasmic reticulum and microtubules, with the haustorium, is described.
Rust fungi (Basidiomycota; Order Uredinales) belong to the largest groups of fungi, with more than 6000 recognized species. Rust diseases have accompanied human history from the beginning of agriculture in the Fertile Crescent and Central America, by threatening the health and productivity of the earliest cereal (wheat, barley, maize) and legume (pea, bean) crops. In antiquity, the Romans have practiced the ceremony of the Robigalia, to sacrifice to and to appease Robigo, the god of cereal rust diseases. In the 17th century, French laws ordered the eradication of barberry bushes surrounding fields of wheat to avoid stem rust epidemics, before the causal agent of the disease (P. graminis f. sp. tritici) had even been recognized.
An annotated list of the rust fungi (Uredinales or Pucciniales) of French Guiana is presented. It enumerates 68 species of which 57 are new reports for the department and 3, Aecidium plukenetiae, Puccinia kourouensis and P. parianicola, are new to science. Dicheirinia guianensis and Hapalophragmium angylocalycis are excluded from the French Guianan mycobiota. New host plants are reported for Batistopsora crucis-filii, B. pistila, Cerotelium ficicola, C. sabiceae, Crossopsora piperis, Desmella aneimiae, Endophyllum guttatum, Kweilingia divina, Puccinia lateritia, Uredo anthurii and Uromyces anguriae. Previously undescribed characters are presented for Achrotelium lucumae, Chaconia ingae, Cerotelium sabiceae, Prospodium amapaensis, Sphenospora smilacina and Uromyces wulffiae-stenoglossae. Chaconia ingae showed haustorial complexes comprising both intracellular hyphae and D-haustoria. In Cerotelium sabiceae, the haustorial mother cells retained the nuclei while D-haustoria were enucleate. The occurrence of these haustorial types in tropical rust fungi is discussed. Internal basidium formation is described for the first time in Sphenospora: teliospores of S. smilacina produced external or internal basidia. The species richness and composition of the French Guianan rust mycobiota are discussed in a neotropical context.
An electron- and light-microscopic study revealed that D-haustoria of Chrysomyxa rhododendri (DC.) De Bary and Chrysomyxa pirolata Winter were pedicellate and had a more or less tuber-shaped haustorial body. The haustorial necks were wrapped by a fold of the extrahaustorial membrane (velopedunculate haustorial type). The aecioid uredinia of Chrysomyxa rhododendri and Chrysomyxa empetri (Pers.) Schröter were covered by a one-layered peridium of the pucciniastreous type. In Chrysomyxa pirolata, young uredinia were covered by one to three layers of sterile fungal cells. In all investigated species, urediniospore mother cells were formed blastically by proliferating basal cells. Subsequent cell divisions of the urediniospore mother cells led to the formation of urediniospores and intercalary cells. In Chrysomyxa rhododendri, the intercalary cells had a pronounced proximal thickening of the radial wall. In Chrysomyxa pirolata andChrysomyxa empetri, the wall was uniformly thickened. Telial morphology of Chrysomyxa rhododendri and Chrysomyxa pirolata was very similar. In Chrysomyxa rhododendri, the probasidia formed true chains without intercalary cells, and they are probably of thallic origin. During maturation they partly separated at their septa by dissolution of the primary wall of the septa between the probasidia. No sterile elements were present in the telia. The occurrence of velopedunculate D-haustoria and a uredinial peridium of the pucciniastreous type confirm the systematic position of Chrysomyxa close to pucciniastreous rusts, Cronartium, and Coleosporium within Melampsoraceae.
Aluminum chloride (AlCl(3)) and sodium metabisulfite (Na(2)S(2)O(5)) have received increasing attention as antifungal agents for the control of plant diseases. In an effort to understand their toxic action on fungi, ultrastructural changes and membrane damage in Fusarium sambucinum (Ascomycota) and Heterobasidion annosum (Basidiomycota) in response to salt exposure was investigated using transmission electron microscopy. Conidial membrane damage was quantified using SYTOX Green stain, which only enters altered membranes. The results showed that mortality of the conidia was generally closely associated with SYTOX stain absorption in F. sambucinum treated with Na(2)S(2)O(5) and in H. annosum treated with AlCl(3) or Na(2)S(2)O(5), suggesting that these salts cause membrane alterations. For both fungi, ultrastructural alterations in conidia treated with AlCl(3) and Na(2)S(2)O(5) included membrane retraction, undulation, and invagination. At higher concentrations or exposure periods to the salts, loss of membrane integrity, cytoplasmic leakage, and cell rupture were observed. Ultrastructural alterations and increased SYTOX stain absorption in salt-treated conidia appear consistent with a mode of action where AlCl(3) and Na(2)S(2)O(5) alter membrane integrity and permeability.
