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Susceptibility level of cucumber downy mildew (Pseudoperonospora cubensis) to metalaxyl  [PDF]
Bagi Ferenc F.,Bala? Ferenc F.,Stoj?in Vera B.,Budakov Dragana B.
Zbornik Matice Srpske za Prirodne Nauke , 2009, DOI: 10.2298/zmspn0916141b
Abstract: Level of susceptibility of Pseudoperonospora cubensis isolate from Ratkovo to metalaxyl in concentrations 50, 100, 200, 400 and 800 μg/ml was investigated. The trials were conducted on cotyledon and fully developed young leaves using cucumber cultivar Haro . Reduced level of susceptibility was detected in metalaxyl concentrations of 50, 100 and 200 μg/ml because the intensity of sporulation in these treatments was on the same level as in control. Sporulation was also observed on developed leaves treated with metalaxyl in concentrations of 400 and 800 μg/ml.
Several infection factors of Pseudoperonospora cubensis

SHI Yanxia,LI Baoju,LIU Xuemin,

应用生态学报 , 2005,
Abstract: The study on the effects of temperature and humidity on the pathogenicity of Pseudoperonospora cubensis showed that the optimum temperature for the occurrence of cucumber downy mildew was 25-35 degrees C. An alternation of 15/35 degrees C was the most propitious to the infection of Pseudoperonospora cubensis, while the high temperature above 35 degrees C could kill the pathogens. 2 hours humid was enough for infection. Pseudoperonospora cubensis stored at -20 degrees C for 10 months and dried for 7 days could still infect cucumber. The infected cucumber leaves could continuously produce sporangium, with its quantity gradually decreased with time. The quantity of sporangium produced in vivo was more than that in vitro.
Expression Profiling of Cucumis sativus in Response to Infection by Pseudoperonospora cubensis  [PDF]
Bishwo N. Adhikari, Elizabeth A. Savory, Brieanne Vaillancourt, Kevin L. Childs, John P. Hamilton, Brad Day, C. Robin Buell
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0034954
Abstract: The oomycete pathogen, Pseudoperonospora cubensis, is the causal agent of downy mildew on cucurbits, and at present, no effective resistance to this pathogen is available in cultivated cucumber (Cucumis sativus). To better understand the host response to a virulent pathogen, we performed expression profiling throughout a time course of a compatible interaction using whole transcriptome sequencing. As described herein, we were able to detect the expression of 15,286 cucumber genes, of which 14,476 were expressed throughout the infection process from 1 day post-inoculation (dpi) to 8 dpi. A large number of genes, 1,612 to 3,286, were differentially expressed in pair-wise comparisons between time points. We observed the rapid induction of key defense related genes, including catalases, chitinases, lipoxygenases, peroxidases, and protease inhibitors within 1 dpi, suggesting detection of the pathogen by the host. Co-expression network analyses revealed transcriptional networks with distinct patterns of expression including down-regulation at 2 dpi of known defense response genes suggesting coordinated suppression of host responses by the pathogen. Comparative analyses of cucumber gene expression patterns with that of orthologous Arabidopsis thaliana genes following challenge with Hyaloperonospora arabidopsidis revealed correlated expression patterns of single copy orthologs suggesting that these two dicot hosts have similar transcriptional responses to related pathogens. In total, the work described herein presents an in-depth analysis of the interplay between host susceptibility and pathogen virulence in an agriculturally important pathosystem.
mRNA-Seq Analysis of the Pseudoperonospora cubensis Transcriptome During Cucumber (Cucumis sativus L.) Infection  [PDF]
Elizabeth A. Savory, Bishwo N. Adhikari, John P. Hamilton, Brieanne Vaillancourt, C. Robin Buell, Brad Day
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035796
Abstract: Pseudoperonospora cubensis, an oomycete, is the causal agent of cucurbit downy mildew, and is responsible for significant losses on cucurbit crops worldwide. While other oomycete plant pathogens have been extensively studied at the molecular level, Ps. cubensis and the molecular basis of its interaction with cucurbit hosts has not been well examined. Here, we present the first large-scale global gene expression analysis of Ps. cubensis infection of a susceptible Cucumis sativus cultivar, ‘Vlaspik’, and identification of genes with putative roles in infection, growth, and pathogenicity. Using high throughput whole transcriptome sequencing, we captured differential expression of 2383 Ps. cubensis genes in sporangia and at 1, 2, 3, 4, 6, and 8 days post-inoculation (dpi). Additionally, comparison of Ps. cubensis expression profiles with expression profiles from an infection time course of the oomycete pathogen Phytophthora infestans on Solanum tuberosum revealed similarities in expression patterns of 1,576–6,806 orthologous genes suggesting a substantial degree of overlap in molecular events in virulence between the biotrophic Ps. cubensis and the hemi-biotrophic P. infestans. Co-expression analyses identified distinct modules of Ps. cubensis genes that were representative of early, intermediate, and late infection stages. Collectively, these expression data have advanced our understanding of key molecular and genetic events in the virulence of Ps. cubensis and thus, provides a foundation for identifying mechanism(s) by which to engineer or effect resistance in the host.
Mechanisms of high temperature-induced Pseudoperonospora cubensis resistance of cucumber

SHI Yan-xia,LI Bao-ju,LIU Xue-min,

应用生态学报 , 2007,
Abstract: This paper studied the effects and control efficiency of high temperature on the pathogenicity and occurrence of Pseudoperonospora cubensis. The results showed that the P. cubensis resistance of cucumber was most obvious after treated at 40 degrees C for 2 h or at 45 degrees C for 1 h, with the control efficiency being 58. 40% and 45. 81% at the forth day, and 39. 35% and 37. 65% at the sixth day after P. cubensis inoculation, respectively. Under high temperature, the activities of peroxidase (POD), phenylalanine ammonia lyase (PAL) , chitinase (Cht), beta-1,3-glucanase (Glu) in cucumber leaf were significantly higher, and large amount of lignin was deposited on the cell wall of leaf tissue, indicating that after treated with high temperature, cucumber plant manifested an induced P. cubensis resistance.
Which Morphological Characteristics Are Most Influenced by the Host Matrix in Downy Mildews? A Case Study in Pseudoperonospora cubensis  [PDF]
Fabian Runge, Beninweck Ndambi, Marco Thines
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044863
Abstract: Before the advent of molecular phylogenetics, species concepts in the downy mildews, an economically important group of obligate biotrophic oomycete pathogens, have mostly been based upon host range and morphology. While molecular phylogenetic studies have confirmed a narrow host range for many downy mildew species, others, like Pseudoperonospora cubensis affect even different genera. Although often morphological differences were found for new, phylogenetically distinct species, uncertainty prevails regarding their host ranges, especially regarding related plants that have been reported as downy mildew hosts, but were not included in the phylogenetic studies. In these cases, the basis for deciding if the divergence in some morphological characters can be deemed sufficient for designation as separate species is uncertain, as observed morphological divergence could be due to different host matrices colonised. The broad host range of P. cubensis (ca. 60 host species) renders this pathogen an ideal model organism for the investigation of morphological variations in relation to the host matrix and to evaluate which characteristics are best indicators for conspecificity or distinctiveness. On the basis of twelve morphological characterisitcs and a set of twelve cucurbits from five different Cucurbitaceae tribes, including the two species, Cyclanthera pedata and Thladiantha dubia, hitherto not reported as hosts of P. cubensis, a significant influence of the host matrix on pathogen morphology was found. Given the high intraspecific variation of some characteristics, also their plasticity has to be taken into account. The implications for morphological species determination and the confidence limits of morphological characteristics are discussed. For species delimitations in Pseudoperonospora it is shown that the ratio of the height of the first ramification to the sporangiophore length, ratio of the longer to the shorter ultimate branchlet, and especially the length and width of sporangia, as well as, with some reservations, their ratio, are the most suitable characteristics for species delimitation.
The effect of high temperature regulation on the infection of Pseudoperonospora cubensis

LI Baoju,PENG Ren,PENG Xiawei,WANG Fujian,SHI Yanxia,ZHAO Aimei,

生态学报 , 2001,
Abstract: 采取温湿度相结合的方法来研究高温处理对黄瓜霜霉病菌(Pseudoperonospora cubensis Rostov)侵染的影响,比较研究了35-50℃4个温度梯度、50%-90%5个湿度组合处理对病菌致病性的影响。同一相对湿度条件下,随着温度的上升病菌致病性降低;40-50℃的高温范围内,在同一温度下随着湿度的不断升高,受处理病菌的致病能力逐渐下降。在RH80%以上、温度40℃以上时,病菌的致病力随着处理时间的延长而变弱;45℃以下的高温高湿处理病菌超过1h,病菌基本上没有致病性。通过高温控制苗期黄瓜霜霉病的研究,确定高温高湿防治苗期黄瓜霜霉病的最佳温湿度为45℃1h(RH80%)。通过高温致死菌诱导植株抗性的研究,初步明确高温处理致死的病菌可以短期诱导植株的抗性。
Evaluación de fungicidas convencionales e inductores de resistencia para el combate de Mildiú Velloso (Pseudoperonospora cubensis) en melón (Cucumis melo)
Méndez Leiva,William; Arauz,Luis Felipe; Ríos,Rodrigo;
Agronomía Costarricense , 2010,
Abstract: evaluation of conventional fungicides and disease resistance inducers for the control of downy mildew (pseudoperonospora cubensis) on melon (cucumis melo). cucurbit downy mildew, caused by the oomycete pseudoperonospora cubensis (berck & curtis) rostovtsev, is one of the most important diseases of melons in costa rica. the control of downy mildew by the application of conventional fungicides in combination with resistance inducers was investigated on melon (cucumis melo l.) cv. ‘ruidera’. two systemic fungicides, mefenoxam (1.96 kg a.i.ha-1) and dimethomorph (0.45 kg a.i.ha-1), and a sequence of the protectant fungicides chlorothalonil/mancozeb (2.01/1.20 kg a.i.ha-1), were applied, by themselves or in combination with application of each of 3 resistance inducers, phosphite (1.01 kg a.i.ha-1), menadione sodium bisulphite (msb, 0.14 kg a.i.ha-1) and acibenzolar- s-methyl (asm, 0.02 kg a.i.ha-1). controls with no fungicides or no inducers were included in the experiment. significant differences (p<0.05) in area under the disease progress curve (audpc) were observed among fungicides. the lowest values of audpc were obtained with the chlorothalonil/ mancozeb sequence, and with dimethomorph. mefenoxam was not effective. the combination with phosphite improved the efficacy of all the conventional fungicides. no effect in disease control was observed with the application of msb or asm, either alone or combined with conventional fungicides. the treatments chlorothalonil/mancozeb and dimethomorph were less expensive than other treatments with lower efficacy.
Evaluación de fungicidas sistémicos para el control del mildiú velloso (Pseudoperonospora cubensis Berk. & Curt.) Rost. en el cultivo del melón (Cucumis melo L.)
Ruiz-Sánchez, E.;Tún-Suárez, J. M.;Pinzón-López, L. L.;Valerio-Hernández, G.;Zavala-León, M. J.;
Revista Chapingo. Serie horticultura , 2008,
Abstract: the effectiveness of four systemic fungicides (azoxystrobin, 150 g·ha-1; dimethomorph, 225 g·ha-1; fosetil-al, 2 kg·ha-1; y triforine, 285 g·ha-1) for downy mildew control (pseudoperonospora cubensis) was evaluated in cantaloupe melon early sown at the yucatan state, mexico. the fungicides were sprayed at 36, 52 and 67 days after transplant (dat), and the disease intensity at 43, 60, and 75 dat, yield components, and fruit soluble solids concentration, were assessed. no significant difference on disease incidence (5.6-12.5%) was observed at 43 dat. disease incidence (73.3%) on dimetomorph treated plots was significantly lower than in the control plots at 60 dat. disease incidence reached 100% in all treatments in the last recorded date, 75 dat. disease severity, measured with horsfall-barratt scale, was significantly lower in dimetomorph treated plants in the three dates evaluated. the final disease severity was significantly lower in plants treated with dimetomorph or fosetil-al, in which 85 and 75%, respectively, less area under the disease progress curve (audpc) was observed than in the control plants. these fungicides also induced the highest number of fruits per plot, mean individual fruit weight, and total fruit yield. the fruit soluble solids concentrations were not significantly different among treatments. a linear negative effect (r2=0.84) of the disease severity (audpc) on the total fruit yield was found.
Evaluación de fungicidas convencionales e inductores de resistencia para el combate de mildiú velloso (Pseudoperonospora cubensis) en melón (Cucumis melo)  [cached]
William Méndez Leiva,Luis Felipe Arauz,Rodrigo Ríos
Agronomía Costarricense , 2010,
Abstract: El mildiú velloso, causado por el oomicete Pseudoperonospora cubensis (Berck & Curtis) Rostovtsev, es una de las enfermedades más importantes en el cultivo de melón en Costa Rica. En la presente investigación se estudió el efecto de la aplicación de 2 fungicidas sistémicos convencionales, mefenoxam (1,96 kg i.a.ha-1) y dimethomorph (0,45 kg i.a.ha-1) y una secuencia de 2 fungicidas protectores, clorotalonil/mancozeb (2,01/1,20 kg i.a.ha-1), en combinación con 3 inductores de resistencia, fosfito (1,01 kg i.a.ha-1), menadiona bisulfito sodio (MBS) (0,14 kg i.a.ha-1), acibenzolar-S-metil (ASM) (0,02 kg i.a.ha-1), más un testigo sin fungicida y otro sin inductor, sobre la severidad de la enfermedad en el melón cv Ruidera . Se encontraron diferencias significativas (p<0,05) en el área bajo la curva de progreso de la enfermedad entre los tratamientos fungicidas. La menor severidad se observó con los tratamientos clorotalonil/mancozeb y dimethomorph, en comparación con el mefenoxam. El fosfito fue el único inductor que resultó en diferencias significativas con respecto a los otros inductores y al testigo sin aplicación de inductores. No se determinaron interacciones estadísticamente significativas entre los fungicidas y los inductores de resistencia. El tratamiento que mostró la mayor eficiencia en el combate de la enfermedad fue clorotalonil/mancozeb+fosfito, con 4 aplicaciones de fungicidas y 2 del inductor de resistencia. Este tratamiento tuvo un costo económico menor que otros menos eficientes en el combate de la enfermedad.
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