Pathological anatomy of the Dutch elm disease. Distribution and development of Ceratocystis ulmi in elm tissues

1970 ◽  
Vol 48 (11) ◽  
pp. 2043-2057 ◽  
Author(s):  
René Pomerleau
Keyword(s):  
Dead Wood ◽  
Dutch Elm Disease ◽  
Primary Wall ◽  
Pathological Anatomy ◽  
Millipore Filter ◽  
Ulmus Americana ◽  
Histological Studies ◽  
Bordered Pits ◽  
Parenchyma Cells ◽  
Host Tissues

Extensive histological studies carried out, during 3 years, on more than 200 white elms (Ulmus americana L.), young and old, artificially or naturally inoculated with Ceratocystis ulmi (Buis.) C. Moreau, add more precision on the spread and location of the fungus in host tissues and the site of the pathogenesis. With new and improved techniques, characteristic spores and hyphae of the pathogen were clearly observed in vessels and never in other tissues and were sharply differentiated from cell contents and artifacts. Double bordered pits or the thin primary wall between secondary thickenings is the only means of passage of the fungus from one vessel to another. All fungus elements in culture and in tree are 1.0 μ or more in diameter, and no living structure of this species passed through a millipore filter of 1.2 μ. Hyphae and spores, observed in fibers and parenchyma cells in dead wood or close to a dead area of the stem, were attributed to other fungi.Clusters of spores and hyphae, frequently found in vessels of all types and sizes, do not alone explain leaf wilting.

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.

STUDIES ON THE INFECTION PROCESS OF CERATOCYSTIS ULMI (BUISM.) C. MOREAU IN AMERICAN ELM TREES

1962 ◽  
Vol 40 (12) ◽  
pp. 1567-1575 ◽  
Author(s):  
G. B. Ouellette
Keyword(s):  
Seasonal Changes ◽  
Cell Walls ◽  
Growth Ring ◽  
Infection Process ◽  
Dutch Elm Disease ◽  
Ulmus Americana ◽  
American Elm ◽  
Bordered Pits ◽  
Rapid Spread ◽  
Per Se

Histological studies of controlled beetle and artificially infected American elm trees (Ulmus americana L.) show that the pathogen of the Dutch elm disease, Ceratocyslis ulmi (Buism.) C. Moreau, grows extensively in all tissues of the xylem. The pathogen produces numerous small spores and hyphae, which pass from cell to cell by means of pits and direct penetration of the walls. This explains the rapid spread of the fungus in the host. Disintegration of bordered pits and of cell walls occurs as infection develops. Acute symptoms of the disease are attributed primarily to complete plugging of the vessels of small branches by the fungus and disintegration products. Gradual or partial plugging of vessels of stems and larger branches and disintegration of cell walls per se are postulated as contributing to the chronic symptoms of the disease. Crossing of the fungus from one growth ring to the next in branches is described.Host reactions to the fungus and seasonal changes in nutrients are discussed in relation to resistance. In beetle-inoculated trees, it was found that wounds extending from the crotch down the sides of the branch were the most favorable for the establishment of infection.

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.

Localisation structurale et ultrastructurale d'activités peroxydasiques dans les parois du mésophylle et des fibres en cours de lignification chez l'alfa (Stipa tenacissima)

1984 ◽  
Vol 62 (12) ◽  
pp. 2644-2649 ◽  
Author(s):  
M. Harche
Keyword(s):  
Peroxidase Activity ◽  
Oxidase Activity ◽  
Cell Walls ◽  
Secondary Wall ◽  
Outer Part ◽  
Potassium Cyanide ◽  
Primary Wall ◽  
Stipa Tenacissima ◽  
Parenchyma Cells

Using diaminobenzidine as substrate, peroxidase activity was localized in the walls of parenchyma cells and differentiating fibres. In mature fibres and parenchyma a slight activity could be recognized in primary walls only. In parenchyma cells, peroxidase activity was fairly inhibited with heat, potassium cyanide, and aminotriazole, which could indicate the presence of catalase within the cell walls. However, in plasmodesmatal regions peroxidases were- resistant to the above inhibitors. Syringaldazine oxidase activity was present only in the primary wall and the outer part of the secondary wall of differentiating fibres. The parallelism between lignification and peroxidase activity in the secondary walls supports the hypothesis of the involvement of these enzymes in the lignification process.

The fine structure of the pits of Eucalyptus regnans (F. Muell.) and their relation to the movement of liquids into the wood

1960 ◽  
Vol 8 (1) ◽  
pp. 51 ◽  
Author(s):  
J Cronshaw
Keyword(s):  
Secondary Wall ◽  
Structural Features ◽  
Cellulose Microfibrils ◽  
Primary Wall ◽  
Detailed Structure ◽  
Eucalyptus Regnans ◽  
Pit Membrane ◽  
Parenchyma Cells ◽  
Ray Parenchyma ◽  
Ray Parenchyma Cells

Observstion in the electron microscope of carbon replicas of the pits of vessels, ray parenchyma cells, fibres, and tracheids of Eucalyptus regnans has shown the detailed structure of the pit borders and the pit closing membranes. In all cases in the mature wood the primary wall is left apparently without modification as the pit membrane. Unlike the borders of the pits of fibre tracheids and tracheids, the pit borders of the vessels are not separate; the cellulose microfibrils of a border may be common to several pits. The pit borders of fibre traoheids and tracheids are developed as separate entities and have a structure similar to the pit borders of softwood tracheids. The structure of the secondary wall layers associated with the pits is described and related to the structure of the pits. The fine structural features of the pits, especially of the pit closing membranes, are discussed in relation to the movement of liquids into wood.

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