Contribution à l'étude du Bayoud, fosariose du palmier-dattier. I. Étude du cultivar sensible Deglet-Nour

1990 ◽  
Vol 68 (10) ◽  
pp. 2054-2058 ◽  
Author(s):  
Béatrice Mathéron ◽  
Abdellatif Benbadis
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fusarium Oxysporum ◽  
Spore Germination ◽  
Date Palm ◽  
Wilt Disease ◽  
Root Epidermis ◽  
Bordered Pits ◽  
Early Reaction ◽  
Scanning Electron

Date palm seedlings were inoculated at the two-leaf stage with Fusarium oxysporum f. sp. albedinis, the causal agent of Bayoud. Following spore germination, hyphae bore a bole through the walls of the root epidermis and penetrated into the cortical parenchyma. The fungus then grows inter- or intra-cellularly towards the central cylinder and enters the xylem vessels. There, it continues to grow towards the leaves. The progression from vessel to vessel is achieved through bordered pits. The cultivar Deglet-Nour, known for its susceptibility to this wilt disease, exhibited no early reaction to the presence of the parasite in its tissues. Key words: date palm, Fusarium oxysporum f. sp. albedinis, scanning electron microscopy.

scholarly journals Scanning electron microscopy and enzymatic analysis in Agave americana during Fusarium oxysporum infection

2020 ◽  
Vol 38 (3) ◽  
Author(s):  
Sheila Jazmín Reyes-Zambrano ◽  
Carlos Alberto Lecona-Guzmán ◽  
Federico Antonio Gutiérrez-Miceli ◽  
Nancy Santana-Buzzy ◽  
Ignacio Islas-Flores ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fusarium Oxysporum ◽  
Enzymatic Analysis ◽  
Agave Americana ◽  
Scanning Electron

La quitinasa y <em>B</em>-1,3-glucanasa desempeñan una función importante en la reacción de defensa contra patógenos fúngicos. En <em>Agave americana</em> existe poca información sobre el comportamiento de estas proteínas en respuesta a la infección de <em>Fusarium oxysporum</em>. En este estudio, se realizó un análisis de microscopía electrónica de barrido (MEB) en raíces de A. americana infectadas con <em>F. oxysporum</em> y se evaluó la actividad de quitinasa y <em>B</em>-1,3-glucanasa en raíces de <em>A. americana</em> a 0, 7, 15 y 30 días después de inoculación con<em> F. oxysporum</em>. MEB reveló que 15 días después de la inoculación (DDI) son suficientes para que el hongo infecte las raíces de<em> A. americana</em>. La actividad de quitinasa en plantas infectadas incrementó significativamente a los 15 DDI con respecto a las plantas no infectadas, mientras que la actividad de <em>B</em>-1,3 glucanasa no presentó diferencia estadística significativa con plantas testigo. Los resultados sugieren que, en respuesta a la infección por <em>F. oxysporum</em>, <em>A. americana</em> activa proteínas PRs de tipo quitinasas.

Direct in siut identification of cellulose microfibrils associated with Rhizobium leguminosarum biovar trifolii attached to the root epidermis of white clover

1995 ◽  
Vol 41 (2) ◽  
pp. 202-207 ◽  
Author(s):  
Pedro F. Mateos ◽  
David L. Baker ◽  
Saleela Philip-Hollingsworth ◽  
Andrea Squartini ◽  
Angelo D. B. Paruffo ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
White Clover ◽  
Rhizobium Leguminosarum ◽  
Root Surface ◽  
Cellulose Microfibrils ◽  
Enzyme Cytochemistry ◽  
Root Epidermis ◽  
Scanning Electron

Firm attachment of Rhizobium species to the legume root epidermis involves the elaboration of extracellular microfibrils extending from the bacteria and contacting the root surface at multiple sites. We investigated the nature of these extracellular microfibrils associated in situ with Rhizobium leguminosarum bv. trifolii colonized on the root epidermal surface of its legume host, white clover (Trifoiium repens L.). Scanning electron microscopy of seedling roots inoculated with the wild-type strain ANU843 showed that these extracellular microfibrils were associated with the bacteria attached not only to root hairs but also to the non-root-hair epidermis and the external environment under the influence of the developing root. Polystyrene microspheres adsorbed to the root surface did not accumulate similar microfibrils, ruling out their formation by nonspecific deposition of mucigel or self-assembly of rhizoplane fibrils of plant origin. An isozyme of cellulase was purified from Streptomyces sp. strain A20, shown to exhibit high substrate specificity for β-1,4-glucans, and used in enzyme cytochemistry to investigate the nature of these extracellular microfibrils. Combined scanning electron microscopy and computer-assisted image analysis indicated that the extracellular microfibrils associated with attached bacteria were degraded by a brief exposure to the purified cellulase but not by a broad-spectrum protease. These results provide direct in situ evidence of the cellulosic nature of the extracellular microfibrils associated with cells of R. leguminosarum bv. trifolii that have colonized the root environment of its legume host, white clover.Key words: Rhizobium, clover, cellulose microfibrils, enzyme cytochemistry, surface ecology, rhizoplane.

Hyphal interactions between a mycoparasite, Pythium nunn, and several soil fungi

1984 ◽  
Vol 30 (12) ◽  
pp. 1482-1487 ◽  
Author(s):  
R. Lifshitz ◽  
M. Dupler ◽  
Y. Elad ◽  
R. Baker
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Rhizoctonia Solani ◽  
Fusarium Oxysporum ◽  
Host Range ◽  
Phase Contrast ◽  
Soil Fungi ◽  
Limited Host Range ◽  
Pythium Nunn ◽  
Scanning Electron

The modes of hyphal interaction between a mycoparasite, Pythium nunn, and several soil fungi were studied by both phase-contrast and scanning-electron microscopy. In the zone of interaction, Pyth. nunn massively coiled around and subsequently lysed hyphae of Pyth. ultimum and Pyth. vexans. In contrast, Pyth. nunn penetrated and eventually parasitized hyphae of Rhizoctonia solani, Pyth. aphanidermatum, Phytophthora parasitica, and Phyto. cinnamomi by forming appressoriumlike structures. However, Pyth. nunn was not mycoparasitic against Fusarium oxysporum f.sp. cucumerinum or Trichoderma koningnii and was destroyed by T. harzianum and T. viride. These observations demonstrated that Pyth. nunn was a necrotrophic mycoparasite, with a limited host range and differential modes of action among suscepts.

The Distribution and Structure of Pits Between Vessels and Imperforate Tracheary Elements in Angiosperm Woods

IAWA Journal ◽  
2008 ◽  
Vol 29 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Yuzou Sano ◽  
Tomohiro Ohta ◽  
Steven Jansen
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Field Emission ◽  
Tracheary Element ◽  
Interspecific Variation ◽  
Tracheary Elements ◽  
Bordered Pits ◽  
Vessel Elements ◽  
Scanning Electron

This study focuses on the interspecific variation in the distribution and structure of pits between vessels and imperforate tracheary elements. Specimens from the outer sapwood of eight species, in which vessel elements are frequently in contact with fibres and/or tracheids, were prepared using two different techniques and examined by field-emission scanning electron microscopy. In three species in which vessels are surrounded by vasicentric tracheids and/or fibres with distinctly bordered pits, pit pairs frequently occurred in walls between vessels and imperforate tracheary elements. In the five species in which vessels are in contact with fibres with indistinctly bordered pits, no or very few pit pairs were present, and blind pits were often found. Blind pits were exclusively present in vessel elements in some species, while they were restricted to imperforate tracheary elements in other species. The nature of vessel to imperforate tracheary element pitting appears to depend on tracheary element specialization.

scholarly journals Scanning Electron Microscopy of Spore Germination in Dictyostelium discoideum

1972 ◽  
Vol 112 (3) ◽  
pp. 1383-1386 ◽  
Author(s):  
R. P. George ◽  
R. M. Albrecht ◽  
K. B. Raper ◽  
I. B. Sachs ◽  
A. P. MacKenzie
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Dictyostelium Discoideum ◽  
Spore Germination ◽  
Scanning Electron

Cytological studies on the infection of barley cultivars with known resistance genotypes by Rhynchosporium secalis

1990 ◽  
Vol 68 (9) ◽  
pp. 1953-1961 ◽  
Author(s):  
H. Lehnackers ◽  
W. Knogge
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Spore Germination ◽  
Leaf Surface ◽  
Rhynchosporium Secalis ◽  
Susceptible Cultivar ◽  
Infection Cycle ◽  
Fungal Development ◽  
Barley Cultivars ◽  
Scanning Electron

Seven races of Rhynchosporium secalis were screened for their virulence on a variety of barley cultivars. Four races were identified as virulent on cultivar Atlas 46 (resistance loci Rrs1 and Rrs2) but virulent on the near-isogenic cultivar Atlas (Rrs2). For one of these races, US238.1, the fungal infection cycle was followed on the susceptible cultivar by means of light and scanning electron microscopy. From a comparative analysis of fungal development on the susceptible and resistant cultivars, two lines of plant defense emerged: (i) inhibition of spore germination on the leaf surface and (ii) prevention of the establishment of the subcuticular stroma. Investigations of the development of race US238.1 on different barley cultivars with and without Rrs1 and on F1 individuals from different crosses excluded involvement of Rrs1 in the inhibition of spore germination. Possible pathogenicity mechanisms are discussed. Key words: leaf scald, microscopy, plant resistance.

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