Studies on conidial germination and initial growth of the grapevine powdery mildew Uncinula necator on artificial substrates

1989 ◽  
Vol 30 (4) ◽  
pp. 415-421 ◽  
Author(s):  
R. Blaich ◽  
C. Heintz ◽  
R. Wind
Keyword(s):  
Powdery Mildew ◽  
Conidial Germination ◽  
Artificial Substrates ◽  
Uncinula Necator ◽  
Initial Growth ◽  
Grapevine Powdery Mildew

Release, germination, and pathogenicity of ascospores of Uncinula necator under controlled conditions

1998 ◽  
Vol 76 (5) ◽  
pp. 777-781 ◽  
Author(s):  
F Jailloux ◽  
T Thind ◽  
M Clerjeau
Keyword(s):  
Powdery Mildew ◽  
Vitis Vinifera ◽  
Storage Conditions ◽  
Vitis Vinifera L ◽  
Uncinula Necator ◽  
Grapevine Powdery Mildew ◽  
Germination Ability ◽  
Ascospore Release ◽  
Probable Role ◽  
Leaf Disks

A laboratory technique was standardized for studying the release, maturation, germination, and pathogenicity of ascospores of Uncinula necator (Schw.) Burr. Surface disinfestation and wetting of grape (Vitis vinifera L.) leaf disks bearing cleistothecia collected in the vineyard before incubation in a humid chamber for 48 h at 20°C were found essential for obtaining the release of ascospores (8 ascospores/cm2). Storage conditions involving periodic wetting treatments of cleistothecia at 5°C during 110 days were necessary to induce both ascospore release (80 ascospores/cm2) and germination ability (62%). The matured ascospores were pathogenic on healthy leaf disks at 20°C indicating their probable role as a primary inoculum source. This technique can be helpful in studying the inheritance of characteristics such as pathogenicity and fungicidal resistance.Key words: cleistothecia, ascospores, maturation, germination, pathogenicity, Uncinula necator, grapevine, powdery mildew.

scholarly journals Distributions of Sensitivities to Three Sterol Demethylation Inhibitor Fungicides Among Populations of Uncinula necator Sensitive and Resistant to Triadimefon

1997 ◽  
Vol 87 (8) ◽  
pp. 784-791 ◽  
Author(s):  
Eugene O. Erickson ◽  
Wayne F. Wilcox
Keyword(s):  
Powdery Mildew ◽  
Active Form ◽  
Correlation Coefficients ◽  
The Other ◽  
Cross Resistance ◽  
Uncinula Necator ◽  
Previous Exposure ◽  
Grapevine Powdery Mildew ◽  
Dmi Fungicides ◽  
Demethylation Inhibitor

Single-conidial isolates of Uncinula necator from (i) a population representing two vineyards with no previous exposure to sterol demethylation inhibitor (DMI) fungicides (“unexposed,” n = 77) and (ii) a population representing two vineyards in which powdery mildew was poorly controlled by triadimefon after prolonged DMI use (“selected,” n = 82) were assayed to determine distributions of sensitivities to the DMI fungicides triadimenol (the active form of triadimefon), myclobutanil, and fenarimol. Median 50% effective dose (ED50) values (micrograms per milliliter) in the selected versus unexposed populations were 0.06 versus 1.9 for triadimenol, 0.03 versus 0.23 for myclobutanil, and 0.03 versus 0.07 for fenarimol, respectively. Isolates were grouped into sensitivity classes according to their ED50 values, and those from the selected population were categorized as resistant if the frequency of their sensitivity class had increased significantly relative to levels found in the unexposed population (ED50 values exceeding 0.56, 0.18, and 0.18 μg/ml for triadimenol, myclobutanil, and fenarimol, respectively). Of the 76 isolates defined as resistant to triadimenol, 64% were classified as cross-resistant to myclobutanil, 18% were classified as cross-resistant to fenarimol, and 17% were classified as resistant to all three fungicides; 25% of the isolates classified as resistant to myclobutanil also were classified as resistant to fenarimol. Similar cross-resistance relationships were revealed when all isolates were examined by regressing log ED50 values for each fungicide against those for the remaining two fungicides to determine the correlation coefficients (e.g., r = 0.85 for triadimenol versus myclobutanil and 0.56 for triadimenol versus fenarimol). The restricted levels of cross-resistance indicated by these data, particularly between fenarimol and the other two fungicides, is in sharp contrast to the high levels of cross-resistance among DMIs reported for some other pathogens and has significant implications with respect to programs for managing grapevine powdery mildew and DMI resistance.

scholarly journals Suppression of Grapevine Powdery Mildew by a Mycophagous Mite

Plant Disease ◽  
2005 ◽  
Vol 89 (12) ◽  
pp. 1331-1338 ◽  
Author(s):  
Heather S. Melidossian ◽  
Robert C. Seem ◽  
Greg English-Loeb ◽  
Wayne F. Wilcox ◽  
David M. Gadoury
Keyword(s):  
Powdery Mildew ◽  
Vitis Vinifera ◽  
Uncinula Necator ◽  
Laboratory Studies ◽  
Rapid Loss ◽  
Infection Efficiency ◽  
Grapevine Powdery Mildew ◽  
Grape Powdery Mildew

Orthotydeus lambi reduced the severity of grape powdery mildew (Uncinula necator) on fruit and foliage of Vitis vinifera ‘Chardonnay’ and ‘Riesling’ in repeated field and laboratory trials. Vines were infested with O. lambi at two densities (5 or 30 mites per leaf) at each of two times (2 to 3 weeks prebloom and 1 week postbloom). Overall, powdery mildew on the berries and foliage was suppressed by early (prebloom) mite releases at both densities, but only by the higher density in late (postbloom) releases. In a separate trial, when foliage was infested at 30 mites per leaf but mites were excluded from certain fruit clusters, severity of powdery mildew was significantly reduced on the mite-free clusters of mite-infested shoots. Thus, O. lambi may suppress powdery mildew on the fruit by reducing inoculum from foliar infections. In laboratory studies, both immature and mature mites reduced infection efficiency, colony expansion, and sporulation of the mildew colonies; but immature mites were more voracious feeders, consuming more pathogen biomass per unit of mite biomass. Mites tore at the mycelium and conidia with their palps during feeding, leading to leakage, rapid loss of hyphal turgor, and collapse of hyphae.

scholarly journals Effects of Humidity on the Development of Grapevine Powdery Mildew

2003 ◽  
Vol 93 (9) ◽  
pp. 1137-1144 ◽  
Author(s):  
J. E. Carroll ◽  
W. F. Wilcox
Keyword(s):  
Powdery Mildew ◽  
Management Practices ◽  
Absolute Humidity ◽  
Uncinula Necator ◽  
Disease Development ◽  
Optimum Temperature ◽  
Test Range ◽  
Grapevine Powdery Mildew ◽  
Conidium Germination

The effects of humidity on powdery mildew development on grape seedlings and the germination of Uncinula necator conidia in vitro were examined. Studies were conducted at an optimum temperature of 25 ± 2°C. Disease on foliage was markedly affected by humidity levels in the test range of 39 to 98% relative humidity (RH), corresponding to vapor pressure deficits (VPD) of 1,914 to 61 Pa. Incidence and severity increased with increasing humidity to an optimum near 85% RH, and then appeared to plateau or decrease marginally at higher values. Conidial density and chain length also were proportional to humidity, but were influenced less strongly. There was a strong, positive linear relationship between humidity level and frequency of conidium germination with RH treatments of ≤84%. However, germination frequency fell sharply at RH levels above a mean of 87%. All measures of humidity were equally accurate in predicting germination responses; however, VPD was slightly more effective than RH in accounting for effects on disease development and pathogen sporulation, and both were more effective than absolute humidity. Humidity appears to play a significant role in grapevine powdery mildew epidemiology, confirming the benefits of management practices to avoid and mitigate high humidity in the vineyard canopy.

scholarly journals Content of trans-resveratrol in leaves and berries of interspecific grapevine (Vitis sp.) varieties

2009 ◽  
Vol 26 (Special Issue) ◽  
pp. S13-S17 ◽  
Author(s):  
P. Bábíková ◽  
N. Vrchotová ◽  
J. Tříska ◽  
M. Kyseláková
Keyword(s):  
Powdery Mildew ◽  
Downy Mildew ◽  
Plasmopara Viticola ◽  
Fungal Diseases ◽  
Uncinula Necator ◽  
Botryotinia Fuckeliana

The aim of this project was to study changes in the content of <i>trans</i>-resveratrol in berries and leaves of grapevine (<i>Vitis</i> sp.) infested by fungal diseases, especially by <i>Botryotinia fuckeliana</i> Whetzel, called as grey mildew, <i>Plasmopara viticola</i> (Berk. & M.A. Curtis) Berl & De Toni, called downy mildew and <i>Uncinula necator</i> (Schw.) Burr, called powdery mildew. In our experiments two white and two blue varieties were used. Contents of <i>trans</i>-resveratrol were determined in healthy and infested leaves and in healthy berries. Infested leaves of white varieties contained more <i>trans</i>-resveratrol than those of blue varieties. The content of <i>trans</i>-resveratrol in berries was lower than that in leaves.

Role of Overwintering Forms of Erysiphe necator in Epidemiology of Grapevine Powdery Mildew in Palestinian Vineyards

2014 ◽  
Vol 2 (1) ◽  
pp. 20-25
Author(s):  
Ruba Abuamsha ◽  
Hajaj Hajjeh ◽  
Mazen Salman
Keyword(s):  
Powdery Mildew ◽  
Temporal Evolution ◽  
Control Strategies ◽  
Temporal Distribution ◽  
Field Surveys ◽  
Sequence Characterized Amplified Region ◽  
Grapevine Powdery Mildew ◽  
Fungal Populations ◽  
Bud Breaking

The overwintering modes of E. necator were studied on Palestinian vineyards, through observations on the differentiation and maturation of cleistothecia and on the occurrence of flag-shoots (deriving from overwintering mycelium) in vineyards. Field surveys were carried out in 17 vineyards for the presence of Flag shoots and cleistothecia, both forms were not observed. Genetic structure and composition of E. necator populations were investigated by application of already available SCAR (Sequence Characterized Amplified Region) primers specific for the "flag-shoot" and "ascospore" biotypes. These primers were used to evaluate the dynamics of the spatial and temporal distribution of the two biotypes, into fungal populations present in 8 vineyards, with different cultivars and spray histories, in various Palestinian districts (Hebron, Bethlehem, Jerusalem, Ramallah, Jericho, Nablus, Jenin, Tulkarm). 397 samples were analyzed by the uses of the primer pairs UnE-UnF in PCR reactions. All samples were found to be of the ascospore biotypes. This finding shows that the “flag shoot” biotype, appears soon after bud breaking and disappears later, while the “ascospore” biotype is more frequently associated to later infections and bunches damages. Such information would be helpful to understand the reasons underlying possible temporal evolution of the pathogen's populations in vineyards, and can have important implications for powdery mildew rationale control strategies.

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