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When cultivating pumpkin crops in most agricultural regions of the world, one of the most aggressive diseases is real powdery mildew, the damage of plants in which, under optimal soil and climatic conditions for the pathogen, reaches 100%. In the open and protected ground, among the cultivated representatives of the Cucurbitaceae family, the most widespread and harmful are the species Sphaerotheca fuliginea (Schlecht ex Fr.) Poll and Erysiphe cichoracearum f. sp. cucurbitacearum (DC ex Merat). In regions where both phytopathogens are present, mixed infections may occur, making identification difficult, and, accordingly, further plant protection measures. The pathogens of this powdery mildew of pumpkin crops have different requirements for temperature and humidity. During the growing season, there may be a change in species composition when conditions change, for example, when a new season begins. Symptoms of the disease in the form of a white or yellowish powdery plaque in the form of rounded spots (mainly on the leaves) can manifest themselves at all stages of plant development, the susceptibility of which increases by the beginning of fruiting. According to biological characteristics, S. fuliginea and E. cichoracearum are obligate biotrophic pathogens, unable to exist independently without living photosynthetic tissue, except for the wintering (sexual) stage of teleomorphs in the form of globular kleistothecia. At this stage, it is not difficult to differentiate pathogens by the morphology of kleistothecium. When analyzing the plant material of melons with the naked eye, S. fuliginea and E. cichoracearum cause similar symptoms of damage, but by microscopy these organisms can be distinguished by a complex of morphological characteristics. Taxonomically significant features are: the location of the mycelium, the formation of conidia (single or chain), the presence or absence of noticeable fibrosin bodies, the features of the appressoria, the size and shape of the conidia, as well as the position and type of their sprout tubes. The works of Russian and foreign scientists have shown the possibility of determining the types and physiological races of pathogens using an indirect method: reactions to differentiator plants. To date, about 30 physiological races of the pathogen Podosphaera xanthii (Sphaerotheca fuliginea) and 2 races of E. cichoracearum are known. However, this method does not always correlate with the methods of molecular analysis. Determination of the species composition of powdery mildew pathogens is a starting point for the development of a further strategy for the cultivation of pumpkin crops and in breeding work for resistance to this disease.

Copyright of Hortscience Journal of Suez Canal University is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Plant Protection & Pathology is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pesticides is considered one of the most hazardous compounds that caused serious health implications to man and environment. However, their use is perquisite to guarantee a high yield especially, for greenhouse cucumber production. In fact, the process success depend on spraying coverage, rate and early detection of infection symptoms. In this study, a novel remote sensing approach for detecting Powdery Mildew symptoms in cucumber (Cu-cumis sativus) leaves has been developed. The experiment was conducted under greenhouse conditions. An unmanned vehicle platform used to carry the remote sensing sensors. Infected leaves were then analyzed using a pioneer image processing model. In this model, leaves were classified according to different feature especially, the reflect color. Image processing results were then assessed using ground reference data (lab analysis). The accuracy assessment of remotely-sensed data was ground reference data were comparable. Because changes in infected leaves associated with the imagery model data, we conclude that remotely-sensed data derived from the unmanned vehicle sensor data hold promise for detecting Powdery Mildew symptoms in cucumber leaves. [ABSTRACT FROM AUTHOR]

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.

Foliar sprays of three plant resistance inducers, including chitosan (CH), potassium sorbate (PS) (C6H7kO2), and potassium bicarbonates (PB) (KHCO3), were used for resistance inducing against Erysiphe cichoracearum DC (powdery mildew) infecting okra plants. Experiments under green house and field conditions showed that, the powdery mildew disease severity was significantly reduced with all tested treatments of CH, PS, and PB in comparison with untreated control. CH at 0.5% and 0.75% (w/v) plus PS at 1.0% and 2.0% and/or PB at 2.0% or 3.0% recorded as the most effective treatments. Moreover, the highest values of vegetative studies and yield were observed with such treatments. CH and potassium salts treatments reflected many compounds of defense singles which leading to the activation power defense system in okra plant. The highest records of reduction in powdery mildew were accompanied with increasing in total phenolic, protein content and increased the activity of polyphenol oxidase, peroxidase, chitinase, and ß-1,3-glucanase in okra plants. Meanwhile, single treatments of CH, PS, and PB at high concentration (0.75%, 2.0%, and/or 3.0%) caused considerable effects. Therefore, application of CH and potassium salts as natural and chemical inducers by foliar methods can be used to control of powdery mildew disease at early stages of growth and led to a maximum fruit yield in okra plants. [ABSTRACT FROM AUTHOR]

DC. were significantly higher in the transgenic tobacco than in wild-type tobacco (p < 0.05). The activities of peroxidase (POD) and catalase (CAT), after inoculation with E. cichoracearum DC., were higher in the transgenic tobacco than in the wild-type. Conversely, the malondialdehyde (MDA) content was significantly lower in the transgenic tobacco than the wild-type before and after inoculation. In addition, our study also indicated that the resistance to E. cichoracearum DC. might involve the salicylic acid (SA) and jasmonic acid (JA) pathways, because the expression levels of pathogenesis-related gene 1 (PR-1a) and coronatine-insensitive 1 (COI1) were significantly increased and decreased, respectively, after inoculation with E. cichoracearum DC. The present study supports the notion that PR-1a and POD participate in resistance to E. cichoracearum DC. in the transgenic tobacco plants. [ABSTRACT FROM AUTHOR]

A double-stranded RNA (dsRNA) HBJZ1506 recovered from the phytopathogenic fungus Erysiphe cichoracearum infecting Calendula officinalis in Jingzhou, Hubei Province, China, was sequenced. HBJZ1506 comprises 11,908 nucleotides (nt) and contains a 11,859-nt-long open reading frame (ORF) coding for a polypeptide that is 61 % identical to that of a putative endornavirus named grapevine endophyte endornavirus (GeEV). The putative polyprotein has an RNA-dependent RNA polymerase (RdRp) domain and an RNA helicase domain, which show homology to and have an arrangement that is similar to that of their counterparts in approved or putative endornaviruses. In a phylogenetic tree constructed using amino acid sequences of the RdRp region of HBJZ1506 and selected endornaviruses, HBJZ1506 clustered with endornaviruses and formed a well-supported monophyletic branch with GeEV. These results suggest that HBJZ1506 might represent a novel endornavirus, for which the name Erysiphe cichoracearum endornavirus (EcEV) is proposed. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Fifteen okra varieties/Lines (Green water, Hybrid-133 Sanam, Laxmy, PMF-Beauty, Sabzpari, Super Star, Adventa Selection, Okra1548, JK-Tetra-6, Okra-7100, Pusa Sawani, Kirn, Click-5769 and OH-152 were cultivated in experimental area of Department of Plant Pathology, University of Agriculture, Faisalabad on April 10,2011to determine their response against powdery mildew of okra under augmented design. No cultivar was found immune. Sabzpari and Hybrid-133 expressed resistant response (2-3%), while Okra-7100, Adventa selection, Okra-1548 and Kirn exhibited moderately resistant (7-9%) while Super star, PMF-Beauty and OH-152 were found moderately susceptible (23-29%) Pusa Swani, JK-Tetra-6, Laxmy and Green water were susceptible (42-47%), while Sanam and Click-5769 were highly susceptible with 76-85% disease incidence. [ABSTRACT FROM AUTHOR]

The Robinia pseudoacacia plant extract has been reported to have protective effect against cucumber powdery mildew ( Sphaerotheca fuliginea ). In this study, the active compound of R. pseudoacacia was isolated from the plant extract, and the structure was identified to be d -Pinitol by nuclear magnetic resonance. d -Pinitol, as a known compound, has important physiological activity on plant osmotic tolerance and medicinal activities on human health. This study is the first to report the antifungal activity of d -pinitol on an obligate parasite S. fuliginea and tried to develop a phytochemical fungicide. The evaluation in the growth chamber showed that the control effect of d -pinitol and its formulation against cucumber powdery mildew disease was 80.7% and 94.4%, at a concentration of 0.5 mg/ml. This formulation was further tested in a greenhouse to evaluate its control effect against cucumber ( S. fuliginea ) and tobacco ( Erysiphe cichoracearum ) powdery mildew under natural condition. The efficacy of d -pinitol in both trials was better than that of positive control at the recommended concentration. The content of d -pinitol in this plant was 25 mg/g (w/w, dry leaves weight) as determined by gas chromatography. The abundant biomass of d -pinitol in R. pseudoacacia plant extract makes it more economical in practical use. Our study provides a base for the future exploitation of d -pinitol as a natural phytochemical fungicide. [ABSTRACT FROM AUTHOR]

Certain plant-derived agents (PDA) which could induce resistance in okra leaves against powdery mildew (Erysiphe cichoracearum) and biochemical changes in treated leaves were investigated during 2011 and 2012 growing seasons. At the two-leaf old, four- and eight-week leaves of the greenhouse-grown okra plants were sprayed with either PDA two days before inoculation with conidia. Among all tested PDA, neem seed oil (NSO) caused the highest protection, followed by jojoba oil (JO) and extract ofReynoutria sachalinensis. Moreover, levels of total protein, activity of peroxidase, polyphenyloxidase and chitinase and total phenols content of treated two-leaf old highly increased after application of NSO and JO, but not by the pathogen (untreated control). Finally, based on conidia germination, lack of the fungitoxic effect of JO and RE and also the slight effect of NSO (9–13.75%) may demonstrate the main role of these agents for inducing resistance through the activation of biochemical defence in treated leaves. [ABSTRACT FROM AUTHOR]

Powdery mildew caused by Podosphaera xanthii is an important disease of melon, and race 2F is the predominant race in most areas of China. Resistance to P. xanthii race 2F in melon K7-1 was controlled by a dominant gene, designated Pm- 2F, in a 106-member population of recombinant inbred lines derived from K7-1× susceptible K7-2. Using bulked segregant analysis with molecular markers, we have identified two polymorphic simple sequence repeats (SSR) to determine that Pm- 2F is located on linkage group II. Comparative genomic analyses using mapped SSR markers and the cucumber genome sequence showed that the melon chromosomal region carrying Pm- 2F is homologous to a 288,223 bp genomic region on cucumber chromosome (chr) 1. The SSR markers on chr 1 of cucumber, SSR02734, SSR02733 and CS27 were found linked with Pm- 2F. Comparative mapping showed that two SSR markers (SSR02734 and CMBR8) flanked the Pm- 2F locus and two nucleotide binding site-leucine-rich repeat resistance genes were identified in the collinear region of cucumber. A cleaved amplified polymorphic sequence (CAPS) marker was developed from the sequence of resistance genes and it delimits the genomic region carrying Pm- 2F to 0.8 cM. The evaluation of 165 melon accessions and 13 race differential lines showed that the newly developed CAPS (CAPS- Dde I) marker can be used as a universal marker for effective marker assisted selection in melon powdery mildew resistance breeding. The putative resistance gene cluster provides a potential target site for further fine mapping and cloning of Pm- 2F. [ABSTRACT FROM AUTHOR]

High-performance liquid chromatographic (HPLC) analysis of chloroform fraction (CF) of cow urine showed rich pool of phenolic acids. Antifungal and antibacterial bioassays of CF have shown its tremendous efficacy against some fungal plant pathogens as well as human pathogenic bacteria at very low concentrations. The CF also inhibited powdery mildew (Erysiphe cichoracearum) of balsam (Impatiens balsamania) under field conditions during pre- and post-inoculation treatments. HPLC analysis of pre- and post-inoculation-treated plant leaves indicated that CF induced phenolic acid synthesis as compared to control. The results revealed that CF of cow urine has the potential for controlling some important human diseases. The result on balsam powdery mildew is a good signal that CF may also be effective against other plant diseases in the field. [ABSTRACT FROM AUTHOR]

Abstract: Plant injuries activate signal transduction cascades mediated by the plant hormones, which lead to enhanced expression of defence related genes and/or to changes in the emission of volatile organic compounds that can act as semiochemicals. In this research we demostrated that infection with the biotrophic pathogen Golovinomyces cichoracearum (DC.) V.P. Heluta (ex Erysiphe cichoracearum DC.), the causal agent of powdery mildew, led in the susceptible host Nicotiana tabacum L. cv Havana 425 to an increased emission of volatile compounds including Methyl-jasmonate (MeJA), (E)-2-hexenal and (E)-β-ocimene. Furthermore we investigated the role of these volatiles in the plant–pathogen interaction. Exogenous application of MeJA induced in tobacco an increase in the transcripts level of the defence related genes lipoxygenase, allene oxide cyclase and defensin and a decrease in the severity of the infection. Qualitative and quantitative differences in volatile compounds emission were showed also in MeJA-treated plants, where the emission of (E)-β-ocimene was significantly increased instead (E)-2-hexenal was not detected. Application of (E)-2-hexenal reduced the severity of powdery mildew while application of (E)-β-ocimene did not. Since (E)-2-hexenal did not activate in tobacco the accumulation of the above reported genes transcripts and the plant cell death, the reduction of the infection severity could be attributable to its inhibitory activity on the fungal germ tube growth. Our data highlight the contributions of natural substances that can act, directly or indirectly, against phytopathogens. In the global context of sustainability, food safety and environmental protection, such semiochemicals represent an alternative and promising approach to integrated pest management. [Copyright &y& Elsevier]

The powdery mildew disease caused by Erysiphe cichoracearum on Oxalis corniculata and O. corymbosa was recorded for the first time from Uttar Pradesh, India. The symptoms of disease appeared in the first week of March on the upper surface of leaves and then on other green parts of the plant. The development of few cleistothecia on the upper surface of leaves was also observed in the last week of April, when conidial production was slowed down and ceased. The infected plants remained stunted due to reduction in size and number of the leaves. The effect of severe infection of E. cichoracearum on O. corniculata also led to a premature defoliation and early death of the plants. The disease severity was more on Oxalis corniculata as compared to O .corymbosa. The frequency of occurrence of disease on O. corniculata was 75.8 % as compared to 46.0 % on O. corymbosa. [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]

Neem cake is used as a soil amendment. It releases nutrient into the soil very slowly. It is also an insect repellent. It improves the physical as well as biological conditions of the soil such as soil aeration, water holding capacity and also the microflora in the rhizosphere. Aqueous extract of neem cake was used against powdery mildew (Erysiphe cichoracearum) of balsam (Impatiens balsaminia) in the field at 25, 50, 75 and 100%. The efficacy was observed even at low concentrations (25%). Foliar application of aqueous extract of neem cake induced synthesis of phenolic acids in balsam. Maximum phenolic acid was detected in balsam plant leaves treated with 50% neem cake followed by 75% in both pre-and post-inoculation treatments. The induction of phenolic acid in plants was correlated with the induction of resistance in treated plants against powdery mildew. [ABSTRACT FROM AUTHOR]

We report a role for the Arabidopsis (Arabidopsis thaliana) RESURRECTION1 (RST1) gene in plant defense. The rst1 mutant exhibits enhanced susceptibility to the biotrophic fungal pathogen Erysiphe cichoracearum but enhanced resistance to the necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola. RST1 encodes a novel protein that localizes to the plasma membrane and is predicted to contain 11 transmembrane domains. Disease responses in rst1 correlate with higher levels of jasmonic acid GA) and increased basal and B. cinerea-induced expression of the plant defensin PDF1.2 gene but reduced E. cichoracearum-inducible salicylic acid levels and expression of pathogenesis-related genes PR1 and PR2. These results are consistent with rst1's varied resistance and susceptibility to pathogens of different life styles. Cuticular lipids, both cutin monomers and cuticular waxes, on rst1 leaves were significantly elevated, indicating a role for RST1 in the suppression of leaf cuticle lipid synthesis. The rst1 cuticle exhibits normal permeability, however, indicating that the disease responses of rst1 are not due to changes in this cuticle property. Double mutant analysis revealed that the coil mutation (causing defective JA signaling) is completely epistatic to rst1, whereas the ein2 mutation (causing defective ethylene signaling) is partially epistatic to rst1, for resistance to B. cinerea. The rst1 mutation thus defines a unique combination of disease responses to biotrophic and necrotrophic fungi in that it antagonizes salicylic acid-dependent defense and enhances JA-mediated defense through a mechanism that also controls cuticle synthesis. [ABSTRACT FROM AUTHOR]

The occurrence and geographic distribution of powdery mildew on cucurbits was studied in the Czech Republic, Austria, France, Germany, Great Britain, Italy, Slovakia, Slovenia, Spain, Switzerland, the Netherlands, as well as in Turkey and Israel, during the period 1995–2000. In total, 599 leaf samples with powdery mildew symptoms were collected from cucurbits from 166 locations within the Czech Republic; an additional 69 samples were collected from 42 locations elsewhere. Two powdery mildews ( Golovinomyces cichoracearum and Podosphaera xanthii) were identified. The host range included the cultivated cucurbits ( Cucumis melo, C. sativus, Cucurbita pepo, C. maxima, and Citrullus lanatus) and several other species. P. xanthii was the only powdery mildew pathogen found in Spain, Israel, and Turkey. P. xanthii and G. cichoracearum were detected in the other surveyed countries, occurring in both mixed infections and separately. In the more northerly latitudes and higher elevations, G. cichoracearum is more often the single species. G. cichoracearum was the dominant powdery mildew species in the Czech Republic (detected in 98.8% of the locations there); P. xanthii was found as the lone species in 1.2% of locations. At 28.4% of locations, G. cichoracearum was found with P. xanthii as mixed infections. The hyperparasitic fungus Ampelomyces quisqualis was found in 30% of the samples from the Czech Republic and was also recorded in Austria, Italy, Slovenia, Switzerland, and Great Britain. [ABSTRACT FROM AUTHOR]

Eight red chicory (Cichorium intybus L. var. silvestre Bisch.) cultivars were screened for plant characteristics, yield, resistance to Erysiphe cichoracearum and their persistence of bolting over a two-year period (2002 and 2003 growing seasons) in central Slovenia. On two years with meteorologically different conditions the highest total and marketable weight of heads (i.e. total weight – weight of removed damaged leaves) were obtained from cv. 'Averto', followed by cv. 'Mesola' and 'Rubino'. The most compact heads in both years, were produced by cv. 'Palla rossa-super'. Less productive cultivars of red chicory were on average the most infected with the powdery mildew caused by E. cichoracearum. In 2002 the fungus occurred in a substantially larger extent than in 2003, which was less favourable for spread of the pathogen. The higher temperatures, prevailing in summer 2003, presumably promoted a greater percentage of bolting in plants. Among eight cultivars studied through two years, cv. 'Castel Franco', 'Averto' and 'Mesola' drew no incidence of bolters.

Powdery mildew, caused by Erysiphe cichoracearum or Podosphaera fusca, is a common disease of gerbera daisy (Gerbera jamesonii) grown in Florida. Previous studies demonstrated that silicon reduces powdery mildew in Arabidopsis, cucumber, grape, strawberry, and wheat. In this study, two silicon (Si) sources, calcium silicate and potassium silicate, were evaluated for their ability to reduce powdery mildew in gerbera 'Snow White'. The effect of calcium silicate in flower quality and the silicon uptake was also determined. Calcium silicate was not effective in reducing powdery mildew or in improving flower quality. The silicon content of gerberas treated with potassium silicate was slightly greater than that in plants treated with calcium silicate. However, the severity of powdery mildew was not reduced by potassium silicate. The results suggest that silicon may not be useful for managing this disease of gerbera daisy, possibly due to the low accumulation of silicon by gerbera leaves. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Plant Protection Research is the property of Institute of Plant Protection and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

The role and essentiality of silicon (Si) in plant biology have been debated for >150 years despite numerous reports describing its beneficial properties. To obtain unique insights regarding the effect of Si on plants, we performed a complete transcriptome analysis of both control and powdery mildew-stressed Arabidopsis plants, with or without Si application, using a 44K microarray. Surprisingly, the expression of all but two genes was unaffected by Si in control plants, a result contradicting reports of a possible direct effect of Si as a fertilizer. In contrast, inoculation of plants, treated or not with Si, altered the expression of a set of nearly 4,000 genes. After functional categorization, many of the upregulated genes were defense-related, whereas a large proportion of down-regulated genes were involved in primary metabolism. Regulated defense genes included R genes, stress-related transcription factors, genes involved in signal transduction, the biosynthesis of stress hormones (SA, JA, ethylene), and the metabolism of reactive oxygen species. In inoculated plants treated with Si, the magnitude of down-regulation was attenuated by >25%, an indication of stress alleviation. Our results demonstrate that Si treatment had no effect on the metabolism of unstressed plants, suggesting a nonessential role for the element but that it has beneficial properties attributable to modulation of a more efficient response to pathogen stress. [ABSTRACT FROM AUTHOR]

A cDNA encoding gallerimycin, a novel antifungal peptide from the greater wax moth Galleria mellonella, was isolated from a cDNA library of genes expressed during innate immune response in the caterpillars. Upon ectopic expression of gallerimycin in tobacco, using Agrobacterium tumefaciens as a vector, gallerimycin conferred resistance to the fungal pathogens Erysiphe cichoracearum and Sclerotinia minor. Quantification of gallerimycin mRNA in transgenic tobacco by real-time PCR confirmed transgenic expression under control of the inducible mannopine synthase promoter. Leaf sap and intercellular washing fluid from transgenic tobacco inhibited in vitro germination and growth of the fungal pathogens, demonstrating that gallerimycin is secreted into intercellular spaces. The feasibility of the use of gallerimycin to counteract fungal diseases in crop plants is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Little is known at the molecular level about the transporters involved in nutrient transfer in the plant/powdery mildew interaction. A PCR-based approach was used to identify and isolate a partial-length cDNA coding for an isoform of the plasma membrane H+-ATPase (EcPMA1) in the biotrophic pathogenic fungus Erysiphe cichoracearum. Southern analysis suggests that EcPMA1 exists as a single-copy gene. Sequence analysis indicated a high similarity of EcPMA1 to other fungal H+-ATPases. Expression of EcPMA1 increases in infected Arabidopsis leaves as the disease progresses, correlating with the growth of the pathogen. [Copyright &y& Elsevier]

Abstract: Disease severity (percentage of the leaf area infected) caused by Erysiphe cichoracearum D.C. Ex Mérat powdery mildew on squash (Cucurbita maxima Dutch) was assessed by analysis of visual and digital images. To evaluate the accuracy of these methods, their estimates were compared with actual disease values severity obtained from a digital pattern. A panel of five evaluators did the visual assessments (VIS) and the image analysis assessment considered two capture protocols: scanner (IAS) and digital photography (IAC) using ArcView GIS 3.2 software. The digital pattern was developed with the Adobe® Photoshop 5.0 software using the leaf digital images obtained with the scanner. The procedure to validate and compare the methodologies was based on the -hypothetical variance test proposed by Freese (1960, Forest Sci. 6(2), 139–145) and the estimated error limit (Rennie and Wiant, 1978, Resour. Invent. Notes 14, 1–3), respectively. The results showed a lack of agreement between the estimates from the IAS, IAC and VIS against the digital pattern. The advantages and limitations of using visual analysis and image analysis to assess the squash powdery mildew severity are discussed. [Copyright &y& Elsevier]

Investigates the genetics of the resistance to powdery mildew of flax caused by Oidium lini in Canada. Identification of several resistant Canadian and introduced cultivars; Putative dominant genes that play a role in flax's resistance to powdery mildew.

Abstract: As plants mature it has been observed that some become more resistant to normally virulent pathogens. The ability to manifest the Age-Related Resistance (ARR) response in Arabidopsis to Pseudomonas syringae pathovars tomato (Pst) coincided with the transition to flowering in plants both delayed and accelerated in the transition to flowering. ARR was also associated with a change in PR-1 gene expression, such that young plants expressed PR-1 abundantly at 3 days post inoculation (dpi) while mature plants expressed much less. The Arabidopsis ARR response requires SA accumulation via isochorismate synthase (ICS1) . ICS1 was expressed one dpi with virulent and avirulent Pst in both young and mature plants. The ARR response was also effective versus avirulent Pst providing an additional 4-fold limitation in bacterial growth. Arabidopsis ARR was found to be ineffective against two necrotrophs, Erwinia carotovora subspecies carotovora (bacterium) and Botrytis cinerea (fungus) and one obligate biotroph, Erysiphe cichoracearum (fungus). However, mature wild type, SA-deficient sid2 and NahG plants supported little growth of the obligate biotrophic oomycete, Peronospora parasitica. Therefore ARR to P. parasitica appears to be SA-independent, however the level of ARR resistance was somewhat reduced in these mutants in some experiments. Thus, there may be numerous defence pathways that contribute to adult plant resistance in Arabidopsis. [Copyright &y& Elsevier]

Chitin is a major component of fungal walls and insect exoskeletons. Plants produce chitinases upon pathogen attack and chito-oligomers induce defense responses in plants, though the exact mechanism behind this response is unknown. Using the ATH1 Affymetrix microarrays consisting of about 23,000 genes, we examined the response of Arabidopsis (Arabidopsis thaliana) seedlings to chito-octamers and hydrolyzed chitin after 30 rain of treatment. The expression patterns elicited by the chito-octamer and hydrolyzed chitin were similar. Microarray expression profiles for several genes were verified via northern analysis or quantitative reverse transcription-PCR. We characterized T-DNA insertion mutants for nine chito-oligomer responsive genes. Three of the mutants were more susceptible to the fungal pathogen, powdery mildew, than wild type at measured by conidiophore production. These three mutants included mutants of genes for two disease resistance-like proteins and a putative E3 ligase. The isolation of loss-of-function mutants with enhanced disease susceptibility provides direct evidence that the chito-octamer is an important oligosaccharide elicitor of plant defenses. Also, this study demonstrates the value of microarray data for identifying new components of uncharacterized signaling pathways. [ABSTRACT FROM AUTHOR]