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.

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.

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.

Lack of association between tolerance to the elm phytoalexin mansonone E and virulence in Ophiostoma novo-ulmi

1994 ◽  
Vol 72 (9) ◽  
pp. 1355-1364 ◽  
Author(s):  
Robert H. Proctor ◽  
Raymond P. Guries ◽  
Eugene B. Smalley
Keyword(s):  
Key Words ◽  
Linear Growth ◽  
Field Isolate ◽  
Fungal Species ◽  
Dutch Elm Disease ◽  
Wild Type ◽  
Weakly Virulent

The effect of the elm phytoalexin, mansonone E, on linear growth of 17 fungal species was examined to determine whether the Dutch elm disease fungus Ophiostoma novo-ulmi is more tolerant of mansonone E than other fungi. Linear growth of O. novo-ulmi was less inhibited by mansonone E than that of most, but not all, other fungi examined, suggesting that O. novo-ulmi is relatively tolerant of mansonone E. To determine whether this tolerance is required for pathogenicity, we generated mutants of O. novo-ulmi with reduced tolerance to mansonone E by N-methyl-N′-nitro-N-nitrosoguanidine mutagenesis followed by a screen for reduced tolerance to 1,2-naphthoquinone, a compound similar in structure to mansonones. Reduced tolerance to 1,2-naphthoquinone and mansonone E was accompanied by reduced tolerance to another elm phytoalexin, mansonone F. Two mutants exhibited wild-type levels of virulence on three elms, while three other mutants exhibited markedly reduced virulence compared with the wild-type field isolate from which they were derived. When the weakly virulent mutants were crossed with wild-type isolates, progeny that had wild-type levels of virulence but low tolerance to mansonone E were recovered. These results suggest that although O. novo-ulmi is relatively tolerant of mansonone E, this tolerance may not be required for high levels of virulence on elm. Key words: Ophiostoma novo-ulmi, mansonone, phytoalexin, Dutch elm disease.

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.

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.

Mutations in Ophiostoma ulmi induced by N-methyl-N′-nitro-N-nitrosoguanidine

1990 ◽  
Vol 68 (2) ◽  
pp. 225-231 ◽  
Author(s):  
L. Bernier ◽  
M. Hubbes
Keyword(s):  
Dutch Elm Disease ◽  
Recessive Mutation ◽  
Wild Type ◽  
Ophiostoma Ulmi ◽  
Cell Age ◽  
Disease Mutations ◽  
Nuclear Locus ◽  
Type Strains ◽  
Yeastlike Cells ◽  
Incubation Buffer

Mutations were induced in Ophiostoma ulmi, the causal agent of Dutch elm disease, by treating yeastlike cells of wild-type strains with the alkylating agent N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). The induced frequency of mutation, assessed by scoring the frequency of benomyl-resistant mutants among the surviving population, was highest in treatments that left from 4 to 10% survivors. The survival rate of the cells was affected by mutagen concentration and length of exposure to MNNG, as well as by cell concentration, cell age, pH, and chemical composition of the incubation buffer. Optimal conditions for routine induction of mutants were obtained by resuspending exponentially growing cultures in phosphate buffer at pH 7.5 (2.0 × 107 cells/mL) and treating the cells with MNNG (20 μg/mL) for 90 min with agitation. The proportion of auxotrophs among the survivors increased at least 200-fold when mutagenesis was followed by nystatin enrichment. Most auxotrophs tested were sexually fertile and carried a recessive mutation at a single nuclear locus. The benomyl-resistant phenotype was dominant. Key words: Ophiostoma ulmi, Dutch elm disease, mutations, N-methyl- N′-nitro-N-nitrosoguanidine.

Inheritance and characterization of a dark-germinating, light-inhibited mutant in the fern Ceratopteris richardii

1991 ◽  
Vol 69 (12) ◽  
pp. 2616-2619 ◽  
Author(s):  
Rodney J. Scott ◽  
Leslie G. Hickok
Keyword(s):  
Genetic Analysis ◽  
Key Words ◽  
Nuclear Gene ◽  
Sexual Cycle ◽  
Wild Type ◽  
Ceratopteris Richardii ◽  
Mutant Selection ◽  
Light Inhibition ◽  
Selection For

Selection for a dark-germinating mutant was made with X-irradiated spores of Ceratopteris richardii. A single mutant line (HαDG1) was recovered and analyzed for its germination responses under different light–dark treatments and for transmission of the trait through a complete sexual cycle. HαDG1 was characterized by two phenotypes, dark germination and light inhibition of germination. These responses were exactly opposite from wild-type responses. The level of dark germination for a particular spore batch was stable through time, whereas light inhibition was unstable with time. Genetic analysis indicated that both phenotypes are associated with a single nuclear gene mutation that has been designated dkg1. Key words: fern, photomorphogenesis, mutant selection, germination, spore.

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.

scholarly journals Variation in Growth and Response to Ophiostoma ulmi among Advanced-Generation Progenies and Clones of Elms

1996 ◽  
Vol 14 (3) ◽  
pp. 150-154
Author(s):  
A. M. Townsend ◽  
L. W. Douglass
Keyword(s):  
Female Parent ◽  
Clonal Plants ◽  
General Combining Ability ◽  
Dutch Elm Disease ◽  
Field Plot ◽  
Disease Symptoms ◽  
Ophiostoma Ulmi ◽  
Causal Fungus ◽  
Parent Female ◽  
Advanced Generation

Abstract Controlled pollinations between five disease-tolerant elm (Ulmus L.) clones (Number 970, ‘Urban’, and clones that were later named ‘Homestead’, ‘Pioneer’, and ‘Prospector’) yielded 686 seedlings. Various crosses produced from zero to over 90 seedlings. Only one of four female parents produced any viable selfed seedlings. At age four, all seedlings were inoculated with Ophiostoma ulmi, (Buism.) C. Nannf., the causal fungus for Dutch elm disease. A factorial analysis showed male parent, female parent, and male x female interaction influenced disease symptoms 4 and 8 weeks after inoculation. After a few years of further evaluation of the seedlings, 10 clones were selected for a combination of disease- and insect-tolerance and horticultural desirability. These clones were propagated and established along with four disease-tolerant cultivars and American elm seedlings in a replicated field plot. Three-year-old clonal plants inoculated with O. ulmi varied significantly in their disease symptoms 4 weeks, 1 year, and 2 years after inoculation. Even clones from the same full-sib family showed significant differences in disease tolerance. Results indicate that both specific and general combining ability are important in determining tolerance to Dutch elm disease.

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.

Sign in / Sign up

Export Citation Format

Share Document