Initiation and development of Erysiphe necator chasmothecia and their role in the epidemiology of grapevine powdery mildew in southern Syria

Powdery mildew caused by <em>Erysiphe necator</em> is the most important fungal disease of grapevine in southern Syria. The purpose of this study was to determine the development of chasmothecia and their role as a primary inoculum in spring. Leaves and/or branches were examined by a stereo binocular from July to December 2014 and 2015. The number of chasmothecia was estimated on both surfaces of the leaves, and their viability was estimated by microscopic examination. During 2 years of survey chasmothecia were detected in 45.5% of vineyards. The initial development of chasmothecia on infected leaves was observed in the second half of July. Their numbers increased from July to October, and the sudden reduction at the beginning of November was noted. Chasmothecia were formed on 38.7% of infected leaves, with 12.5%, 18.4%, and 7.5% on the upper, under and on both surfaces of infected leaves respectively. Chasmothecia were more frequent on the leaf under side (0.6 / leaf) than on the leaf upper side (0.4 / leaf), but their occurrence on both sides together was relatively low (0.2 / leaf), and their numbers were highly variable between vineyards and years. Microscopic examination showed that chasmothecia contained 1–5 (usually three) asci with 1–4 (usually three) ascospores in each asci, and 65.6% of chasmothecia were empty. Their viability decreased between December and February, with an average viability of 1.2% and 0.2% in March and April, respectively. Chasmothecia were not detected on bark and ascospores were not trapped at the beginning of the season. These results indicate that the ascospores have no or little role in the initiation of spring infection. To the best of our knowledge, this is the first report of <em>E. necator</em> chasmothecia development and their role in the initiating infection on grapevine in Syria.

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Overwintering form of Erysiphe necator, the causal agent of grapevine powdery mildew in southern Syria

Journal of Plant Protection Research ◽

10.1515/jppr-2017-0017 ◽

2017 ◽

Vol 57 (2) ◽

pp. 129-135 ◽

Cited By ~ 1

Author(s):

Nujoud Alimad ◽

Walid Naffaa ◽

Fawaz Azmeh

Keyword(s):

Powdery Mildew ◽

Winter Season ◽

Causal Agent ◽

Bud Break ◽

Erysiphe Necator ◽

First Report ◽

Primary Inoculum ◽

Grapevine Powdery Mildew ◽

Histopathological Studies ◽

Grapevine Buds

AbstractThe main aims of this study were to determine the overwintering form and the primary inoculum ofErysiphe necator,the causal agent of grapevine powdery mildew in southern Syria. Eleven vineyards located at five different geographical sites were visited every week from March to November in 2014 and 2015. The results of field and histopathological studies showed thatE. necatorsurvived as mycelium in dormant grapevine buds during the winter season. The first flag shoots were observed shortly after bud break in spring. The number of flag shoots varied greatly according to vineyards, cultivars and years, being present on 27.4 to 61.9% of the grapevines in 2014, and on 5.2 to 40% of the grapevines in 2015. The percentage of flag shoots on the same grapevine also varied according to the year, cultivar and location. It was between 4.3 to 9.4% in 2014, and 2.1 to 3.6% in 2015. The disease was observed only on Balady and Black cultivars. Conidia were released from the second week of May to early September. The first conidia were trapped around mid-May, and the first secondary symptoms were observed on leaves from mid-May to early June according to the site. Chasmothecia were observed on leaves in 45.5% of the studied vineyards. The first observation of chasmothecia on leaves was in July, and their numbers varied greatly between vineyards and years. Chasmothecia were not detected on bark, nor were ascospores trapped at the beginning of the season. These results confirmed that the ascospores did not have any role in the initiation of spring infection. To the best of our knowledge, this is the first report of the overwintering form ofE. necatorin Syria.

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Genetic Structure and Aggressiveness of Erysiphe necator Populations during Grapevine Powdery Mildew Epidemics

Applied and Environmental Microbiology ◽

10.1128/aem.01200-08 ◽

2008 ◽

Vol 74 (20) ◽

pp. 6327-6332 ◽

Cited By ~ 30

Author(s):

Josselin Montarry ◽

Philippe Cartolaro ◽

François Delmotte ◽

Jérôme Jolivet ◽

Laetitia Willocquet

Keyword(s):

Powdery Mildew ◽

Latency Period ◽

Growing Season ◽

Spore Production ◽

Erysiphe Necator ◽

Genetic Groups ◽

Grapevine Powdery Mildew ◽

Temporal Differentiation ◽

Group A ◽

Group B

ABSTRACT Isolates of the causal ascomycete of grapevine powdery mildew, Erysiphe necator, correspond to two genetically differentiated groups (A and B) that coexist on the same host. This coexistence was analyzed by investigating temporal changes in the genetic and phenotypic structures of E. necator populations during three epidemics. Group A was present only at the start of the growing season, whereas group B was present throughout all three epidemics. Group A was less aggressive in terms of germination and infection efficiency but was more aggressive than group B in terms of the latency period, lesion diameter, and spore production. Our results are consistent with a temporal differentiation of niches, preventing recombination, and suggest an association between the disease level and the frequencies of genetic groups.

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First report of powdery mildew on Cissus rhombifolia caused by Erysiphe necator in the Czech Republic

Australasian Plant Disease Notes ◽

10.1007/s13314-012-0044-z ◽

2012 ◽

Vol 7 (1) ◽

pp. 43-45

Author(s):

Sung-Eun Cho ◽

Ji-Hyun Park ◽

Libor Jankovský ◽

Hyeon-Dong Shin

Keyword(s):

Czech Republic ◽

Powdery Mildew ◽

Erysiphe Necator ◽

The Czech Republic ◽

First Report

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Using a limited mapping strategy to identify major QTLs for resistance to grapevine powdery mildew (Erysiphe necator) and their use in marker-assisted breeding

Theoretical and Applied Genetics ◽

10.1007/s00122-010-1511-6 ◽

2010 ◽

Vol 122 (6) ◽

pp. 1059-1073 ◽

Cited By ~ 71

Author(s):

S. Riaz ◽

A. C. Tenscher ◽

D. W. Ramming ◽

M. A. Walker

Keyword(s):

Powdery Mildew ◽

Marker Assisted Breeding ◽

Erysiphe Necator ◽

Major Qtls ◽

Mapping Strategy ◽

Grapevine Powdery Mildew

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First Report of Powdery Mildew Caused by Podosphaera xanthii on Cucurbita argyrosperma in Mexico

Plant Disease ◽

10.1094/pdis-11-21-2458-pdn ◽

2021 ◽

Author(s):

José Francisco Díaz-Nájera ◽

Sergio Ayvar-Serna ◽

Antonio Mena-Bahena ◽

Guadalupe Arlene Mora-Romero ◽

Karla Yeriana Leyva-Madrigal ◽

...

Keyword(s):

Powdery Mildew ◽

Microscopic Examination ◽

Disease Incidence ◽

Phylogenetic Analyses ◽

Its Region ◽

Likelihood Method ◽

28S Rrna ◽

Podosphaera Xanthii ◽

Voucher Specimen ◽

First Report

Cucurbita argyrosperma, commonly named as winter or cushaw squash, is highly sought for its seeds, which have important uses in culinary arts. During the autumn 2021, powdery mildew-like signs and symptoms were observed on cushaw squash in several commercial fields located in Cocula, Guerrero, Mexico. Signs were initially appeared as whitish powdery patches on both sides of leaves and then covering entire leaves and causing premature senescence. The disease incidence was estimated to be 80% in about 1000 plants in two fields. The mycelium was amphigenous, persistent, white in color, and occurred in dense patches. A voucher specimen was deposited in the Herbarium of the Colegio Superior Agropecuario del Estado de Guerrero under the accession number CSAEG22. For the morphological characterization by light microscopy, fungal structures were mounted in a drop of lactic acid on a glass slide. Microscopic examination showed nipple-shaped hyphal appressoria. Conidiophores (n = 30) were straight, 100 to 190 × 10 to 12 μm and produced 2 to 6 conidia in chains. Foot-cells were cylindrical, 41 to 78 μm long, followed by 1 to 2 shorter cells. Conidia (n = 100) were ellipsoid-ovoid to barrel-shaped, 29.5 to 39.1 × 19.4 to 22.7 μm, and contained conspicuous fibrosin bodies. Germ tubes were produced from a lateral position on conidia. Chasmothecia were not observed during the growing season. The morphological characters were consistent with those of the anamorphic state of Podosphaera xanthii (Braun and Cook 2012). For further confirmation, total DNA was extracted from conidia and mycelia following the CTAB method (Doyle and Doyle 1990), and the internal transcribed spacer (ITS) region and part of the 28S gene were amplified by PCR, and sequenced. The ITS region of rDNA was amplified using the primers ITS5/ITS4 (White et al. 1990). For amplification of the 28S rRNA partial gene, a nested PCR was performed using the primer sets PM3 (Takamatsu and Kano 2001)/TW14 (Mori et al. 2000) and NL1/TW14 (Mori et al. 2000) for the first and second reactions, respectively. Phylogenetic analyses using the Maximum Likelihood method, including ITS and 28S sequences of isolates of Podosphaera spp. were performed and confirmed the results obtained in the morphological analysis. The isolate CSAEG22 grouped in a clade with isolates of Podosphaera xanthii. The ITS and 28S sequences were deposited in GenBank under accession numbers OL423329 and OL423343, respectively. Pathogenicity was confirmed by gently dusting conidia from infected leaves onto ten leaves of healthy C. argyrosperma plants. Five non-inoculated leaves served as controls. The plants were maintained in a greenhouse at 25 to 35 ºC, and relative humidity of 60 to 70%. All inoculated leaves developed similar signs to the original observation after 10 days, whereas control leaves remained symptomless. Microscopic examination of the fungus on inoculated leaves showed that it was morphologically identical to that originally observed on diseased plants, fulfilling Koch’s postulates. Podosphaera xanthii has been previously reported on C. maxima, C. moschata, and C. pepo in Mexico (Yañez-Morales et al. 2009; Farr and Rossman 2021). To our knowledge, this is the first report of P. xanthii causing powdery mildew on C. argyrosperma in Mexico. This pathogen is a serious threat to C. argyrosperma production in Mexico and disease management strategies should be developed.

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No Indication of Strict Host Associations in a Widespread Mycoparasite: Grapevine Powdery Mildew (Erysiphe necator) Is Attacked by Phylogenetically Distant Ampelomyces Strains in the Field

Phytopathology ◽

10.1094/phyto-10-11-0270 ◽

2012 ◽

Vol 102 (7) ◽

pp. 707-716 ◽

Cited By ~ 17

Author(s):

Alexandra Pintye ◽

Zsolt Bereczky ◽

Gábor M. Kovács ◽

László G. Nagy ◽

Xiangming Xu ◽

...

Keyword(s):

Powdery Mildew ◽

Environmental Fate ◽

Phylogenetic Analyses ◽

Inter Simple Sequence Repeat ◽

Issr Markers ◽

Genetic Distances ◽

Nuclear Ribosomal Dna ◽

Erysiphe Necator ◽

Grapevine Powdery Mildew ◽

Powdery Mildew Fungi

Pycnidial fungi belonging to the genus Ampelomyces are common intracellular mycoparasites of powdery mildews worldwide. Some strains have already been developed as commercial biocontrol agents (BCAs) of Erysiphe necator and other powdery mildew species infecting important crops. One of the basic, and still debated, questions concerning the tritrophic relationships between host plants, powdery mildew fungi, and Ampelomyces mycoparasites is whether Ampelomyces strains isolated from certain species of the Erysiphales are narrowly specialized to their original mycohosts or are generalist mycoparasites of many powdery mildew fungi. This is also important for the use of Ampelomyces strains as BCAs. To understand this relationship, the nuclear ribosomal DNA internal transcribed spacer (ITS) and partial actin gene (act1) sequences of 55 Ampelomyces strains from E. necator were analyzed together with those of 47 strains isolated from other powdery mildew species. These phylogenetic analyses distinguished five major clades and strains from E. necator that were present in all but one clade. This work was supplemented with the selection of nine inter-simple sequence repeat (ISSR) markers for strain-specific identification of Ampelomyces mycoparasites to monitor the environmental fate of strains applied as BCAs. The genetic distances among strains calculated based on ISSR patterns have also highlighted the genetic diversity of Ampelomyces mycoparasites naturally occurring in grapevine powdery mildew. Overall, this work showed that Ampelomyces strains isolated from E. necator are genetically diverse and there is no indication of strict mycohost associations in these strains. However, these results cannot rule out a certain degree of quantitative association between at least some of the Ampelomyces lineages identified in this work and their original mycohosts.

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