Ultrastructural cell wall modifications in secondary xylem of American elm surviving the acute stage of Dutch elm disease: vessel members

1981 ◽  
Vol 59 (12) ◽  
pp. 2411-2424 ◽  
Author(s):  
G. B. Ouellette
Keyword(s):  
Vessel Wall ◽  
Coating Layer ◽  
Acute Stage ◽  
Dutch Elm Disease ◽  
Disease Stage ◽  
Ulmus Americana ◽  
Tree Resistance ◽  
Pit Membrane ◽  
Dense Band ◽  
Ultrastructural Characteristics

Modified vessel wall layers and their ultrastructural characteristics in branches of artificially inoculated elm (Ulmus americana L.) trees surviving the acute disease stage and of naturally infected, chronically diseased trees are described. Walls of large early-wood vessels in zones where disease action was prevalent have a strong stain reaction and may be uniformly or locally three to four times thicker than normal.In smaller vessels (some including vessel tracheids), an extra lignified-like, often discontinuous layer may be present. This layer is generally demarcated from the normal by a dense band. Pit membranes and vessel end plates are likewise much thickened through the presence of an opaque material similar to that of the pit membrane. This material differs from that forming the coating layer which like tyloses is generally present inside the thickened or extra vessel wall layer.The possible significance of these observations, particularly in relation to disease development and tree resistance, is discussed.

Bordered pit and ray morphology involvement in elm resistance to Ophiostoma novo-ulmi

2009 ◽  
Vol 39 (2) ◽  
pp. 420-429 ◽  
Author(s):  
Juan A. Martín ◽  
Alejandro Solla ◽  
Luis G. Esteban ◽  
Paloma de Palacios ◽  
Luis Gil
Keyword(s):  
Vessel Wall ◽  
Fungal Growth ◽  
Principal Component ◽  
Dutch Elm Disease ◽  
Mean Values ◽  
Anatomical Features ◽  
Wall Area ◽  
Pit Membrane ◽  
Vessel Wall Area ◽  
Component Loadings

The main objective of this study was to identify differential anatomical features between Ulmus pumila L. and Ulmus minor Mill. clones resistant to Dutch elm disease and U. minor clones susceptible to Dutch elm disease, with a focus on the intervascular pits and medullary rays. Resistant elms showed lower mean values than susceptible elms for pit membrane diameter, pit aperture area, pit membrane abundance per vessel-wall area, ray width, and ray tangential area. A principal component analysis of the parameters measured revealed slight differentiation between species but clearly grouped U. minor clones according to their susceptibility group. In comparison with susceptible elms, the pit structure observed in resistant elms may limit passive fungal spread within the sapflow, lower the probability of fungal cells passively reaching pit membranes, and reduce the vulnerability of the xylem to cavitation. Similarly, the ray structure observed in the resistant elms is likely to reduce the amount of easily accessible nutrients available for fungal growth as well as the rate of radial colonization in comparison with susceptible elms. Examination of the principal component loadings suggested that susceptible U. minor clones were mainly characterized by enhanced values of pit membrane abundance per vessel-wall area relative to resistant U. minor trees.

Ultrastructural cell wall modifications in secondary xylem of American elm surviving the acute stage of Dutch elm disease: fibres

1981 ◽  
Vol 59 (12) ◽  
pp. 2425-2438 ◽  
Author(s):  
G. B. Ouellette
Keyword(s):  
Cell Wall ◽  
Tension Wood ◽  
Secondary Xylem ◽  
Acute Stage ◽  
Dutch Elm Disease ◽  
Tubular Structures ◽  
Ulmus Americana ◽  
American Elm ◽  
Innermost Layer ◽  
Host Parasite

Various ultrastructural cell wall modifications of fibres have been observed in artificially or naturally infected American elm (Ulmus americana L.) trees surviving the acute stage of the Dutch elm disease caused by Ceratocystis ulmi (Buism.) C. Moreau. Bands of fibres with gelatinous (SG) layers characteristic of tension wood are frequent in or near invaded tissues; similar layers are also present sometimes in cells identifiable as parenchyma. The SG layer is often different from that observed in healthy trees. Masses or bands of dense material are present which often extend perpendicular as tubular structures to the plasmalemma location. Also, orientation of fibrils in such layers may be disordinate. One or more additional lignified-like layers alternating with additional SG-like or other opaque layers may occur inside the first SG layer. The innermost layer in these cases is often lamellate.Small intracellular locules delimited by one or two wall layers also occur in other cells.The possible significance of these observations in host–parasite relationships of the disease is briefly discussed.

The Microscopy of Compatibility and Incompatibility in Ulmus

1985 ◽  
Vol 43 ◽  
pp. 504-505
Author(s):  
B. L. Redmond ◽  
Christopher F. Bob
Keyword(s):  
Dutch Elm Disease ◽  
Economic Losses ◽  
Hybrid Progeny ◽  
Ulmus Pumila ◽  
Ulmus Americana ◽  
American Elm ◽  
Asian Species ◽  
Ulmus Parvifolia ◽  
Initial Appearance ◽  
Chinese Elm

The American Elm (Ulmus americana L.) has been plagued by Dutch Elm Disease (DED), a lethal disease caused by the fungus Ceratocystis ulmi (Buisman) c. Moreau. Since its initial appearance in North America around 1930, DED has wrought inexorable devastation on the American elm population, triggering both environmental and economic losses. In response to the havoc caused by the disease, many attempts have been made to hybridize U. americana with a few ornamentally less desirable, though highly DED resistant, Asian species (mainly the Siberian elm, Ulmus pumila L., and the Chinese elm Ulmus parvifolia Jacq.). The goal is to develop, through breeding efforts, hybrid progeny that display the ornamentally desirable characteristics of U. americana with the disease resistance of the Asian species. Unfortunately, however, all attempts to hybridize U. americana have been prevented by incompatibility. Only through a firm understanding of both compatibility and incompatibility will it be possible to circumvent the incompatibility and hence achieve hybridization.

Barrier zone formation in host and nonhost trees inoculated with Ophiostoma ulmi. I. Anatomy and histochemistry

1991 ◽  
Vol 69 (9) ◽  
pp. 2055-2073 ◽  
Author(s):  
Danny Rioux ◽  
G. B. Ouellette
Keyword(s):  
Principal Component ◽  
Dutch Elm Disease ◽  
Populus Balsamifera ◽  
Ulmus Americana ◽  
Zone Formation ◽  
Ophiostoma Ulmi ◽  
Parenchyma Cells ◽  
Zone Cell ◽  
Histochemical Tests ◽  
Barrier Zone

Barrier zone formation was studied in small branches of Ulmus americana L., Prunus pensylvanica L.f., and Populus balsamifera L. following inoculation with Ophiostoma ulmi (Buism.) Nannf. (the Dutch elm disease pathogen). Barrier zones were continuous in the nonhosts whereas they were generally discontinuous in U. americana; barrier zone formation also occurred at a later stage of infection in the latter than in the former. Barrier zones were formed of parenchyma cells and fibers in U. americana, mainly of parenchyma cells in Prunus pensylvanica, and of fibers in Populus balsamifera. Fibers as a principal component of barrier zones are described for the first time. Histochemical tests revealed that the proportion of lignin was higher in barrier zone cell walls than in elements of the noninvaded xylem. Barrier zones contained suberized cells, the number of which was progressively greater in the order U. americana, Prunus pensylvanica, and Populus balsamifera. However, many fibers of U. americana occasionally formed a continuous barrier zone and had an internal layer that was slightly suberized. In addition, phenolic compounds were usually detected within barrier zone cells of these species. Key words: Dutch elm disease, nonhost plants, Ophiostoma ulmi, Ulmus americana, anatomy, histochemistry.

scholarly journals Evaluation of 19 American Elm Clones for Tolerance to Dutch Elm Disease

2005 ◽  
Vol 23 (1) ◽  
pp. 21-24 ◽  
Author(s):  
A. M. Townsend ◽  
S. E. Bentz ◽  
L. W. Douglass
Keyword(s):  
Block Design ◽  
Dutch Elm Disease ◽  
Stem Cuttings ◽  
Ulmus Americana ◽  
American Elm ◽  
Foliar Symptoms ◽  
Randomized Block Design ◽  
New Harmony ◽  
Crown Dieback ◽  
Valley Forge

Abstract Rooted stem cuttings of 19 American elm (Ulmus americana L.) cultivars and selections, and rooted cuttings of two non-American elm selections, U. carpinifolia Gleditsch 51 and 970 (U. glabra Huds. x (U. wallichiana Planch. x U. carpinifolia)), along with a group of American elm seedlings, were planted in a randomized block design. When the trees were nine years old, they were inoculated with a mixed spore suspension of Ophiostoma ulmi (Buisman) C. Nannf. and Ophiostoma novo-ulmi Brasier, the causal fungi for Dutch elm disease (DED). Analyses of variance showed highly significant variation among clones in foliar symptoms 4 weeks after inoculation and in crown dieback one and two years after inoculation. After two years, 13 of the American clones showed significantly less dieback than the American elm seedlings, and 18 American clones showed significantly less injury than a randomly chosen, unselected American elm clone, 57845. The American clones with the most DED-tolerance were cultivars ‘Valley Forge,’ ‘Princeton,’ ‘Delaware,’ and ‘New Harmony,’ and selections N3487, R18-2, 290, 190, and GDH. The non-American selections 51 and 970 also exhibited high levels of disease tolerance. Most susceptible were American clones 57845, ‘Augustine,’ Crandall, W590, and the American elm seedlings. The most disease-tolerant American elm selections identified in this study are being evaluated further for possible naming and release to the nursery industry.

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