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.

Barrier zone formation in host and nonhost trees inoculated with Ophiostoma ulmi. II. Ultrastructure

1991 ◽  
Vol 69 (9) ◽  
pp. 2074-2083 ◽  
Author(s):  
Danny Rioux ◽  
G. B. Ouellette
Keyword(s):  
Electron Microscopy ◽  
Dutch Elm Disease ◽  
Populus Balsamifera ◽  
Ulmus Americana ◽  
Light Microscope Level ◽  
Zone Formation ◽  
Ophiostoma Ulmi ◽  
Transmission Electron ◽  
Histochemical Tests ◽  
Barrier Zone

Barrier zone formation was studied in annual shoots and small branches of Ulmus americana L., Prunus pensylvanica L.f., and Populus balsamifera L. following inoculation with Ophiostoma ulmi (Buism.) Nannf. Ultrastructural observations showed that electron-opaque compounds, which usually were identified as containing phenolics by previous histochemical tests, were often present within cells of this tissue. Many lipidic globules were also observed within some barrier zone cells of Populus balsamifera. Additional wall layers, suberized or not, were frequently observed in these barrier zone cells. When histochemical tests for suberin at the light microscope level were strongly positive, the lamellation typical of suberin was evident in transmission electron microscopy. Gum canal formation in Prunus pensylvanica was found to be initiated and the canals widened predominantly by a lysogenous process. Key words: Dutch elm disease, nonhost plants, Ophiostoma ulmi, Ulmus americana, ultrastructure, gum canals, suberized layers.

Light microscope observations of histological changes induced by Ophiostoma ulmi in various nonhost trees and shrubs

1989 ◽  
Vol 67 (8) ◽  
pp. 2335-2351 ◽  
Author(s):  
Danny Rioux ◽  
G. B. Ouellette
Keyword(s):  
Dutch Elm Disease ◽  
Populus Balsamifera ◽  
Class Iii ◽  
Shrub Species ◽  
Histological Changes ◽  
Zone Formation ◽  
Ophiostoma Ulmi ◽  
Parenchyma Cells ◽  
Barrier Zone ◽  
Trees And Shrubs

Ophiostoma ulmi (the Dutch elm disease pathogen) was inoculated into 13 nonhost tree and shrub species. Four classes were recognized based on their susceptibility to this pathogen. In Prunus pensylvanica (class I), bubbles formed in vessel members within 3 days after inoculation, and gels formed 5 days later. At day 5, the vascular cambium covering the colonized zone became altered. A barrier zone was formed in 60% of the inoculated twigs. When twigs wilted, the vessels around the twig were occluded, and barrier zone formation was partial. In Populus balsamifera (class II), tyloses formed in vessels of invaded xylem within 8 days after inoculation followed by accumulation of compounds suspected to be phenolics in parenchyma cells. Barrier zone formation occurred in 66% of the inoculated twigs. In Sorbus americana (class III), a pronounced dark discoloration developed rapidly in the invaded xylem. Sparse gels and O. ulmi cells were present in vessel members. Gel formation was limited to vessels that were adjacent to parenchyma cells. Pit membranes of bordered and half-bordered pit pairs became thicker and more darkly stained than in controls. These observations suggest that the first steps of pathogenesis are induced by the action of harmful metabolites of O. ulmi. Few noticeable changes occurred in the species of class IV.

Barrier Zone Formation as a Resistance Mechanism of Elms to Dutch Elm Disease

IAWA Journal ◽  
1985 ◽  
Vol 6 (1) ◽  
pp. 71-77 ◽  
Author(s):  
K.J.M. Bonsen ◽  
R.J. Scheffer ◽  
D.M. Elgersma
Keyword(s):  
Time Course ◽  
Resistance Mechanism ◽  
Dutch Elm Disease ◽  
Host Responses ◽  
Moderate Degree ◽  
Zone Formation ◽  
Ophiostoma Ulmi ◽  
Time Course Study ◽  
High Degree ◽  
Barrier Zone

Host responses of elms susceptible and resistant to Dutch elm disease were histologically examined. In a time course study the susceptible elm clone Ulmus × hollandica 'Belgica' and U. × hollandica '390', a clone which shows a high degree of resistance to non-aggressive isolates and a moderate degree of resistance to aggressive isolates of Ophiostoma ulmi, were inoculated in twig or trunk with either an aggressive or a non-aggressive isolate of O. ulmi. For purposes of comparison, the susceptible elm U. americana and the more resistant clones U. × hollandica 'Groeneveld', U. 'Lobel' and U. 'Sapporo Autumn Gold' were included. Depending on clone-isolate compatibility, infected twigs reacted by a walling off process, by barrier zone formation, or failed to resist the infection and died. Trees inoculated into the trunk reacted comparably but in the case of a compatible combination they always formed a barrier zone and the cambium never died in the year of inoculation.

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.

Accumulation of mansonones in callus cultures of Ulmus americana L. in the absence of a fungal-derived elicitor

1997 ◽  
Vol 75 (3) ◽  
pp. 513-517 ◽  
Author(s):  
F. G. Meier ◽  
W. R. Remphrey
Keyword(s):  
Culture Media ◽  
Fungal Growth ◽  
Callus Cultures ◽  
Dutch Elm Disease ◽  
Ulmus Americana ◽  
Ophiostoma Ulmi ◽  
Medium Components ◽  
Tissue Culture Media ◽  
Wound Reaction ◽  
Accumulation Ability

The Dutch elm disease pathogens Ophiostoma ulmi (Buism.) Nannf. and Ophiostoma novo-ulmi Brasier elicit the production of phytoalexins called mansonones in the American elm (Ulmus americana L.). As part of a larger investigation, it was revealed that mansonone elicitation in callus culture does not require the Dutch elm disease pathogens, as has been reported in other studies. The objective of this study was to determine the nature and timing of the nonfungal elicited mansonone accumulation in U. americana callus. Initially, 7-week-old calli were subjected to inoculations with various fungal growth medium components. Mansonone production occurred in all treatments, indicating that it was stimulated prior to the addition of the medium components. Next, cotyledons and calli at various stages of development were analysed for the production of mansonones to determine the timing of its production. Mansonone production appeared to be correlated with the initiation of callus production and may be related to the callus wound reaction. As the callus aged, its colour changed from white–green to brown possibly as a result of phytoalexin accumulation. Additional experiments in which the cotyledon source, agar source, and type of plant tissue culture media were modified resulted in no change to the mansonone accumulation ability of the callus. The discrepancy between our results and those of other researchers could be due to differences in the method of mansonone quantification, namely, that our method is more sensitive and led to the detection of mansonones where previously none had been found. Further research must be done in this area to investigate this mansonone accumulation. Key words: phytoalexin, Dutch elm disease, mansonone, Ulmus americana, callus.

scholarly journals Variation in Response of Selected American Elm Clones to Ophiostoma ulmi

1995 ◽  
Vol 13 (3) ◽  
pp. 126-128 ◽  
Author(s):  
A.M. Townsend ◽  
S.E. Bentz ◽  
G.R. Johnson
Keyword(s):  
Dutch Elm Disease ◽  
Main Trunk ◽  
Ulmus Americana ◽  
Disease Symptoms ◽  
Ophiostoma Ulmi ◽  
American Elm ◽  
Causal Fungus ◽  
One Year ◽  
Crown Dieback ◽  
High Degree

Abstract Ramets of nine American elm (Ulmus americana L.) clones or cultivars were planted with ramets of Ulmus ‘Frontier’, Ulmus ‘Prospector’, and American elm seedlings in a randomized block, split-plot design. When they were three years old, the trees were inoculated in the main trunk on either one of two selected dates in May with a spore suspension of Ophiostoma ulmi, the causal fungus for Dutch elm disease (DED). Analyses of variance showed significant variation among clones and between inoculation dates in disease symptoms four weeks and one year after inoculation. Inoculations made on May 18 generally created significantly more symptoms than inoculations made only nine days later. Four-week symptom expression was influenced also by a significant interaction between clonal or seedling group and inoculation date. When data from both inoculation dates were combined, six American elm clones (‘American Liberty’, ‘Princeton’, 680, R18–2, 180, and 3) showed significantly fewer foliar symptoms after four weeks than the American elm seedlings and three other American elm clones. Five of these same six more tolerant American clones averaged significantly less crown dieback after one year than the other American clones or seedlings tested. One of the American elm clones (clone 3) showed a level of disease tolerance equal statistically to ‘Frontier’ and ‘Prospector’, two cultivars which have shown a high degree of tolerance to DED in other studies.

EVALUATION OF MONOSODIUM METHANE ARSENATE FOR THE SUPPRESSION OF NATIVE ELM BARK BEETLES, HYLURGOPINUS RUFIPES (EICHHOFF) (COLEOPTERA: SCOLYTIDAE)

1996 ◽  
Vol 128 (3) ◽  
pp. 435-441 ◽  
Author(s):  
I.L. Pines ◽  
A.R. Westwood
Keyword(s):  
Bark Beetles ◽  
Management Program ◽  
Dutch Elm Disease ◽  
Egg Hatch ◽  
Ulmus Americana ◽  
Ophiostoma Ulmi ◽  
Elm Bark Beetle ◽  
Hylurgopinus Rufipes ◽  
And Control ◽  
Elm Bark Beetles

AbstractThe native elm bark beetle, Hylurgopinus rufipes (Eichhoff), is the major vector of Dutch elm disease, Ophiostoma ulmi (Buisman) Nannf., in Manitoba. The herbicide Glowon™, monosodium methane arsenate (MSMA), was applied to a chainsaw cut in American elm, Ulmus americana L., tree stems to determine if the treated elms would become effective trap trees for H. rufipes. Three treatments were compared: treated with herbicide and girdled, girdled, and control. All herbicide-treated elms died within 18 days after application. Significantly higher numbers (P < 0.01) of native elm bark beetles were attracted to the herbicided elms, compared with the other treatments. Beetles bred only in the elms treated with herbicide. Of the total brood galleries constructed, 72% had no egg hatch while the remaining 28% had larval tunnels. Progeny adults emerged from less than 1% of the larval tunnels. MSMA application could supplement the Dutch elm disease management program in Manitoba.

Nonsporulation in the Dutch elm disease fungus Ophiostoma ulmi: evidence for control by a single nuclear gene

1994 ◽  
Vol 72 (4) ◽  
pp. 461-467 ◽  
Author(s):  
Wayne C. Richards
Keyword(s):  
Key Words ◽  
Genetic Control ◽  
Genetic Stability ◽  
Nuclear Gene ◽  
Dutch Elm Disease ◽  
Wild Type ◽  
Ulmus Americana ◽  
Disease Symptoms ◽  
Ophiostoma Ulmi ◽  
Yeast Phase

A single nuclear gene controls nonsporulation in a novel isolate of the Dutch elm disease fungus Ophiostoma ulmi (Buism.) Nannf. This has been clearly demonstrated through segregation of the nonsporulating phenotype-in meiotic products recovered from crosses between a mutant nonsporulating isolate (WRB2-1) and wild-type sporulating isolates, between F1 progeny and their parents, and between F1 progeny. All crosses between nonsporulating and sporulating isolates yielded a 1:1 ratio for these two phenotypes in the meiotic products, whereas all crossings between isolates of the same phenotype produced meiotic products of that phenotype. The genetic stability of the nonsporulating phenotype was clearly shown when no disease symptoms were observed following artificial inoculation of the nonsporulating progeny into white elm, Ulmus americana L. Exposure to trifluoperazine, a calmodulin inhibitor, did not shift the nonsporulating isolates to the yeast phase, which supports our findings that nonsporulation is under genetic control rather than metabolic control. Key words: nonsporulation, Ophiostoma ulmi, mutant, single nuclear gene, meiotic products.

External symptoms and histopathological changes following inoculation of elms putatively resistant to Dutch elm disease with genetically close strains of Ophiostoma

2005 ◽  
Vol 83 (6) ◽  
pp. 656-667 ◽  
Author(s):  
Abdelali Et-Touil ◽  
Danny Rioux ◽  
Fabienne M Mathieu ◽  
Louis Bernier
Keyword(s):  
Dutch Elm Disease ◽  
Vascular Wilt ◽  
Histopathological Changes ◽  
Ulmus Americana ◽  
Defence Reaction ◽  
Ophiostoma Ulmi ◽  
Host Pathogen Interaction ◽  
Pathogenicity Tests ◽  
Hybrid Clones ◽  
Different Levels

To better characterize the host–pathogen interaction leading to Dutch elm disease, pathogenicity tests were carried out under controlled conditions. Putative resistant hybrid clones 2213 and 2245 from the same Ulmus parvifolia Jacq. × Ulmus americana L. cross and putative resistant U. americana clone 503, as well as saplings of U. americana grown from seeds, were inoculated with strains of Ophiostoma ulmi (Buism.) Nannf. or Ophiostoma novo-ulmi Brasier, including strains H327 and AST27, which carry different alleles at the Pat1 pathogenicity locus and display different levels of aggressiveness. The occurrence of wilted leaves and xylem streaks in inoculated elms indicated that the three clones tested were in fact susceptible to Dutch elm disease, although clones 2213 and 2245 were less susceptible than other elm material tested. In addition to the usual histopathological changes induced during the development of Dutch elm disease on clones 2213 and 2245, such as the formation of alveolar structures, tyloses, gels, and barrier zones, microscopic observations also revealed the presence of cells exhibiting a yellow autofluorescence under blue illumination around xylem vessels invaded by the pathogen. This may represent a new defence reaction against Dutch elm disease. The more aggressive H327 strain induced different levels of xylem responses than the less aggressive AST27 strain.Key words: Dutch elm disease, vascular wilt, histopathology.

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.

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