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The article discusses a 2021 report on the powdery mildew infection of Corylus avellana in Spain caused by Erysiphe corylacearum. It states that infected hazelnut plants had the symptoms or roundish spots of white mycelium on the adaxial side of the leaves, with fruit also being affected and damaged. Also noted is the first occurrence of E. corylacearum causing powdery mildew on hazelnut in Spain in the report.

On absorption by plants, silicon ( Si) offers protection against many fungal pathogens, including powdery mildews. The mechanisms by which Si exerts its prophylactic role remain enigmatic, although a prevailing hypothesis suggests that Si positively influences priming. Attempts to decipher Si properties have been limited to plants able to absorb Si, which excludes the model plant Arabidopsis because it lacks Si influx transporters. In this work, we were able to engineer Arabidopsis plants with an Si transporter from wheat ( TaLsi1) and to exploit mutants ( pad4 and sid2) deficient in salicylic acid ( SA)-dependent defence responses to study their phenotypic response and changes in defence expression against Golovinomyces cichoracearum ( Gc) following Si treatment. Our results showed that TaLsi1 plants contained significantly more Si and were significantly more resistant to Gc infection than control plants when treated with Si, the first such demonstration in a plant transformed with a heterologous Si transporter. The resistant plants accumulated higher levels of SA and expressed higher levels of transcripts encoding defence genes, thus suggesting a role for Si in the process. However, TaLsi1 pad4 and TaLsi1 sid2 plants were also more resistant to Gc than were pad4 and sid2 plants following Si treatment. Analysis of the resistant phenotypes revealed a significantly reduced production of SA and expression of defence genes comparable with susceptible controls. These results indicate that Si contributes to Arabidopsis defence priming following pathogen infection, but highlight that Si will confer protection even when priming is altered. We conclude that Si-mediated protection involves mechanisms other than SA-dependent defence responses. [ABSTRACT FROM AUTHOR]

A series of new N, N′-diacylhydrazine derivatives were synthesized efficiently under microwave irradiation. Their structures were characterized by 1H NMR, MS, and elemental analysis. Various biological activities of these compounds were tested. Most of them exhibited higher herbicidal activities against dicotyledonous weeds than monocotyledonous weeds. In addition, favorable in vivo fungicidal activities were also found of these compounds against Cladosporium cucumerinum, Corynespora cassiicola, Sclerotinia sclerotiorum(Lib.)de Bary, Erysiphe cichoracearum, and Colletotrichum orbiculare (Berk aLMont) Arx. All compounds displayed excellent plant growth regulatory activities: 100% inhibition was achieved against the radicle growth of cucumber. To further investigate the structure-activity relationship, comparative molecular field analysis was performed on the basis of herbicidal activity data, resulting in a statistically reliable model with good predictive power ( r2 = 0.913, q2 = 0.556). Based on the calculation, five additional novel compounds were designed and synthesized. Satisfyingly, compound 4u displayed excellent herbicidal activity (94.7%) at 1500 g/ha, although it is less active than 2,4-D. Meanwhile, this compound also exhibited good fungicidal activity against C. orbiculare (Berk aLMont) Arx (82.16%). [ABSTRACT FROM AUTHOR]

Systemic acquired resistance (SAR) is an inducible defence mechanism which plays a central role in protecting plants from microbial pathogen attack. Guided by bioassays, a new chemical inducer of SAR was isolated from the extracts of Strobilanthes cusia and identified to be 3-acetonyl-3-hydroxyoxindole (AHO), a derivative of isatin. Tobacco plants treated with AHO exhibited enhanced resistance to tobacco mosaic virus (TMV) and to the fungal pathogen Erysiphe cichoracearum (powdery mildew), accompanied by increased levels of pathogenesis-related gene 1 ( PR-1) expression, salicylic acid (SA) accumulation and phenylalanine ammonia-lyase activity. To study the mode of action of AHO, its ability to induce PR-1 expression and TMV resistance in nahG transgenic plants expressing salicylate hydroxylase, which prevents the accumulation of SA, was analysed. AHO treatment did not induce TMV resistance or PR-1 expression in nahG transgenic plants, suggesting that AHO acts upstream of SA in the SAR signalling pathway. In addition, using two-dimensional gel electrophoresis combined with mass spectrometry, five AHO-induced plant proteins were identified which were homologous to the effector proteins with which SA interacts. Our data suggest that AHO may represent a novel class of inducer that stimulates SA-mediated defence responses. [ABSTRACT FROM AUTHOR]

Arabidopsisdoes not support the growth and asexual reproduction of the barley pathogen,Blumeria graminisf. sp.hordei Bgh). A majority of germlings fail to penetrate the epidermal cell wall and papillae. To gain additional insight into this interaction, we determined whether the salicylic acid (SA) or jasmonate (JA)/ethylene (ET) defence pathways played a role in blocking barley powdery mildew infections. Only theeds1mutant andNahGtransgenics supported a modest increase in penetration success by the barley powdery mildew. We also compared the global gene expression patterns ofArabidopsisinoculated with the non-host barley powdery mildew to those inoculated with a virulent, host powdery mildew,Erysiphe cichoracearum.Genes repressed by inoculations with non-host and host powdery mildews relative to non-inoculated control plants accounted for two-thirds of the differentially expressed genes. A majority of these genes encoded components of photosynthesis and general metabolism. Consistent with this observation,Arabidopsisgrowth was inhibited following inoculation withBgh, suggesting a shift in resource allocation from growth to defence. A number of defence-associated genes were induced during both interactions. These genes likely are components of basal defence responses, which do not effectively block host powdery mildew infections. In addition, genes encoding defensins, anti-microbial peptides whose expression is under the control of the JA/ET signalling pathway, were induced exclusively by non-host pathogens. Ectopic activation of JA/ET signalling protectedArabidopsisagainst two biotrophic host pathogens. Taken together, these data suggest that biotrophic host pathogens must either suppress or fail to elicit the JA/ET signal transduction pathway. [ABSTRACT FROM AUTHOR]

In two meteorologically quite different years, 2002 and 2003, efficacy of three natural substances with a fungicidal activity (sulphur, soya lecithin, salicylic acid) for control ofErysiphe cichoracearumon chicory was tested. In a block designed field experiment, there were statistically significant differences in the mean index of infection of exterior leaves, in the mean total weight and mean net weight of the plants (= total weight − weight of removed damaged leaves). There was also a significant difference in firmness of the heads of nine chicory varieties that was established in both years. In 2002, when no extreme weather conditions occurred, the fungus spread to a substantially larger extent. Yet no statistically significant differences were found in the efficacy of environmentally friendly fungicidal substances for control of the fungus. In the hotter and drier year of 2003, which was less favourable for spread of the pathogen, sulphur-containing fungicide was the most effective. In 2002, chicory yield was lower than in 2003. Generally, yield loss due to removal of damaged leaves was from 30.7 to 45.0% in the first year, and from 11.3 to 24.8% in the second. The highest mean total yield and net yield of chicory were in plants, which were treated three times with sulphur-containing fungicide. In 2002, the most firm heads were in plants treated with sulphur. In 2003, no significant differences among substances were detected. The most infected with the powdery mildew caused byE. cichoracearum, were the less productive varieties of chicory. A statistically significant relationship was not found between the firmness of the heads and the degree of infection. Among different parameters in this experiment, the only relevant and high statistically significant positive correlation (r2 = 0.71) was determined between the total weight of the plants and yield loss of chicory due to infection with the fungus in question. [ABSTRACT FROM AUTHOR]

Benzothiadiazole (BTH), as Bion WG50, and acetylsalicylic acid (ASA) treatments of potato foliage of field- and glasshouse-grown potato plants were compared for control of two foliar diseases, early blight (Alternaria solani ) and powdery mildew (Erysiphe cichoracearum ). The effect of these treatments on harvested tubers wound-inoculated with the dry rot fungus (Fusarium semitectum ) was also evaluated. BTH (50 mg a.i. L-1 ) gave almost complete control of both foliar pathogens on inoculated glasshouse-grown plants and reduced the severity of leaf spotting diseases (mainly early blight) in the field. BTH (100 mg a.i. L-1 ) and ASA (400 mg a.i. L-1 ) reduced the severity of dry rot in field-grown tubers in some post-harvest wound-inoculated treatments but not others and a similar reduction occurred with tubers inoculated post-harvest from BTH-treated plants grown under glasshouse conditions. BTH treatment increased β-1,3-glucanase activity in leaves > stem > tubers > stolons but not in roots. Increased enzyme activity was recorded for up to 45 days post-treatment. [ABSTRACT FROM AUTHOR]

To further the understanding of the natural genetic diversity for disease resistance to powdery mildew (Erysiphe cichoracearum) in Arabidopsis thaliana, quantitative trait loci analysis was undertaken on recombinant inbred lines derived from a cross between the resistant accession Warschau-1 and the susceptible Columbia-0. Powdery mildew grew less well on Warschau-1, but the resistance was not associated with a specific block in the infection sequence. Two potential powdery mildew disease-resistance loci were identified and mapped, one with a major effect and one with a minor effect on disease resistance. The two loci acted in an additive manner to confer resistance, and together they explained 65% of the variation in resistance. In addition, the major powdery mildew disease-resistance locus was genetically mapped to the bottom of chromosome III, a region containing the powdery mildew resistance loci RPW7, RPW8 and RPW10. Unlike resistance mediated by the RPW8 locus in the accession Moscow-1, resistance in Warschau-1 was not correlated with the hypersensitive response, highlighting the influence of genetic background or environmental factors on the expression of disease resistance. Together with the powdery mildew resistance loci described in other studies, these results suggest that A. thaliana is a useful source of natural powdery mildew disease resistance, which potentially can be utilized in fundamental studies and as a tool for applied studies. [ABSTRACT FROM AUTHOR]

Studies whether protection of tobacco Havana 425 against compatible Erysiphe cichoracearum, by a necrotic strain of potato virus Y, induces accumulation of hydroxyproline-rich glycoproteins (HRPG). Determination of whether the leaves protected by the virus underwent a further increase in HRPG.

The relative incidence of Erysiphe cichoracearum and Sphaerotheca fuliginea, both agents of powdery mildew of cucurbits, was determined from 275 samples of mildewed leaves of cucurbits collected in 1994 from five regions of France. E. cichoracearum was identified in 9 to 39% of the mildewed leaf samples from four of the regions but was not detected in samples from the Mediterranean island of Corsica. The genetic structure of the French population of E. cichoracearum was examined using RFLPs of the ribosomal internal transcribed spacers amplified by PCR, random amplified polymorphic DNA (RAPD) markers, pathogenicity and mating-type tests. Forty-one isolates, including one from England, were analysed. Cluster analysis from 147 RAPD fragments using 16 primers revealed the existence of three distinct genetic lineages corresponding to three rDNA haplotypes (designated groups A, B and C). Bootstrap, genetic diversity, gametic disequilibrium and private allele analyses supported this differentiation. The genetic differentiation observed in the French population was not related to the geographical origin of the isolates. Group A isolates may be more specialized on melon as, with one exception, they were of race 1 (growth on four of the five melon cultivars tested) in comparison with group B and C isolates, which were of race 0 (growth on IranH only). Thus, the genetic differentiation observed may indicate a host-specialized subdivision within the French population of E. cichoracearum from cucurbits. Gametic disequilibrium analysis among RAPD loci and biological observations suggest that the sexual stage is of minor importance for epidemics of E. cichoracearum on cucurbits. [ABSTRACT FROM AUTHOR]

Perithecia of Erysipbe cichoracearum (powdery mildew) were found on several, but not all, accessions of Lactuca serriola, L. saligna, L. aculeata and L. serriola X L. sativa hybrid. Their occurrence varied between Lactuca species and different accessions of the same species. Perithecia were globular, had a mean diameter of 125.5 /im and contained an average 13-14 asci. Asci had mean dimensions of 55.0 X 26.1 fan and each contained two ascospores which measured an average 17.4 X 10.6/im. There were however significant differences in the dimensions of spores and other structures obtained from different Lactuca accessions. [ABSTRACT FROM AUTHOR]

Local infections of either TMV or TNV in tobacco plants cv. Havana 425 (hypersensitive to TMV) proved effective in inducing systemic resistance to subsequent inoculation with the powdery mildew fungus Erysiphe cichoracearum DC. The proportion of leaf surface invaded by this pathogen and the amount of conidia it produced were both significantly lower in virus inoculated plants than in non-inoculated controls. However, the decrease in sporulation rate was less regularly observed than the reduction in leaf area infected. TMV was more effective than TNV in protecting tobacco plants from powdery mildew. E. cichoracearum is thus added to the list of challenge pathogens to which TMV or TNV are known to induce resistance in the host plants. Necrotic lesions caused to the leaves by local treatment with Ethephon (an ethylene-releasing compound) also conferred to tobacco some degree of systemic resistance to the same fungal pathogen, more frequently visible as a reduction of leaf area invaded. The protection due to the Ethephon lesions was in present experiments less marked than that of TMV. No effects against subsequent powdery mildew infection were obtained when point freeze necrotic lesions were provoked on the plants. [ABSTRACT FROM AUTHOR]

Determines the hydroxyproline-rich glycoprotein accumulation in TMV-tobacco showing systematic acquired resistance (SAR) to powdery mildew. Structural integrity of primary cell walls; Activation of SAR against Erysiphe cichoracearum; Restriction of the penetration of fungal hyphae.

The powdery mildew species Eysiphe cichoracenrum has a described host range of over 300 plant species from among several families. Host-range testing indicates host-specialized subdivision within this taxonomic species. However, the extent of subdivision remains largely undetermined among host-limited forms. We have characterized diversity among field collections of E. cichoracearum from a variety of hosts, and from other powdery mildew species, with RFLPs from a PCR amplified ribosomal DNA (rDNA) segment. The E. cichoracearum samples expressed six distinct RFLP haplotypes. Each haplotype was specific to either a single host or to a set of related host species. These haplotypes formed a continuum of divergence ranging from about 18-35% average pairwise distance from one another, while those from other mildew species clustered at consistently higher average pairwise distances from E. cichoracearum and from each other. Our findings support earlier suggestions, based on host-range and morphologicalcharacterizations, that E. cichorncearum is a complex of morphologically similar, but host-limited forms. Also, comparisons of rDNA haplotype distance between E. cichoracearum and Blumeria (Eysiphe) graminis were consistently greater than between E. cichoracearum and Sphaerotheca fulginea. This result supports earlier questions concerning the monophyletic nature of Eysiphe. [ABSTRACT FROM AUTHOR]

The article focuses on record of Erysiphe corylacearum on Corylus avellana in Switzerland and in central Europe. It mentions molecular phylogenetic analysis showed that the Swiss strains had identical ITS sequences to those of E. corylacearum from Azerbaijan, Georgia, Iran and Turkey. It also mentions pathogen differs from the native hazelnut powdery mildew Phyllactinia guttata, with which it sometimes co-occurs,by forming mycelia on the upper leaf surface and having smaller chasmothecia.

This article provides information on a severe attack of Powdery Mildew seen on some experimental plots of ornamental pyrethrum at Luddington, Warwickshire, England in August 1953. The varieties most severely affected were E. M. Robinson, Queen Mary and James Kelway. Cleistocarps typical of Erysiphe spp. were present on some of the leaves, but the identity of this fungus is difficult to determine. It is obviously near to Erysiphe cichoracearum DC. and it may be E. polyphaga Hammarlund, although the spores are larger than those recorded for this fungus on other hosts.