122 research outputs found
Structural and Biochemical Changes in Salicylic-Acid-Treated Date Palm Roots Challenged with<i>Fusarium oxysporum</i>f. sp.<i>albedinis</i>
No full textHistochemical and ultrastructural analyses were carried out to assess structural and biochemical changes in date palm roots pretreated with salicylic acid (SA) then inoculated withFusarium oxysporumf. sp.albedinis(Foa). Flavonoids, induced proteins, and peroxidase activity were revealed in root tissues of SA-treated plants after challenge by Foa. These reactions were closely associated with plant resistance to Foa. Host reactions induced after inoculation of SA-treated plants with Foa included the plugging of intercellular spaces, the deposition of electron-dense materials at the sites of pathogen penetration, and several damages to fungal cells. On the other hand, untreated inoculated plants showed marked cell wall degradation and total cytoplasm disorganization, indicating the protective effects provided by salicylic acid in treated plants.</jats:p
Lignification: are lignins biosynthesized via simple combinatorial chemistry or via proteinaceous control and template replication?
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Isolates/DNA of species used in this investigation and evaluation of species specificity of the TaqMan assay.
No full text<p>1 Dr. Bud Platt Agriculture and Agri-Food, Prince Edward Island, Canada</p><p>2 Dr. Bill Fry, Cornell University, Ithaca, NYC, USA</p><p>4 Dr. Fouad Daayf, University of Manitoba, Winnipeg, Manitoba</p><p>5 Dr. Michael Coffey, University of California Riverside, Riverside, California, USA</p><p>6 Dr. Schmale, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA</p><p>Fluorescence is indicated as detected (+) or undetected (−) for <i>Phytophthora</i> species.</p
Induction of defense genes and secondary metabolites in saskatoons (Amelanchier alnifolia Nutt.) in response to Entomosporium mespili using jasmonic acid and Canada milkvetch extracts
No full textEntomosporium leaf and berry spot represent the most important disease of saskatoons (Amelanchier alnifolia Nutt.). This disease, caused by the ascomycete Entomosporium mespili (D.C.) Sacc., is difficult to control via conventional methods and no known saskatoon cultivar carries resistance to this pathogen. The aim of the present study was to enhance existing and induced defense responses of saskatoons using two host defense inducers, namely jasmonic acid and an extract from Canada milkvetch on two saskatoon cultivars, Smoky and Martin. Both inducers exhibited an ability to differentially induce the synthesis/accumulation of defense-related genes including those encoding for PR-1, PR-2, PR-5, LOX and PAL. Pre-treatment of saskatoon leaves with these inducers reduced the disease levels especially when applied to the moderately susceptible cultivar Martin. An accumulation of various hydroxycinnamic acid and proanthocyanidin derivatives also correlated with the disease levels recorded on both cultivars. Results are discussed on the basis of the induced pathways in an attempt to lay the ground for a better understanding of this hostpathogen interaction. In the meantime,wehave shown that the use of defense enhancers may be useful in integrated management strategies to control entomosporium leaf and berry spot in saskatoons spot in saskatoons.Fil: Wolski, Erika Alejandra. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata; ArgentinaFil: Henriquez, Maria A.. University Of Manitoba; CanadáFil: Adam, Lorne R.. University Of Manitoba; CanadáFil: Badawi, Mohamed. University Of Manitoba; CanadáFil: Andreu, Adriana Balbina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Biológicas; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Hadrami, Abdelbasset El . University Of Manitoba; CanadáFil: Daayf, Fouad. University Of Manitoba; Canad
Defense gene expression in corn (Zea mays L.) in response to Clavibacter nebraskensis, the causal agent of Goss’s Wilt and Leaf Blight
No full textGoss’s wilt and leaf blight is a growing concern for corn growers in Manitoba, Canada. Little is known about the genetic interaction between corn and the bacterial pathogen, Clavibacter nebraskensis (Cn). The objective of this study was to investigate at the molecular level, how corn can defend against Cn. Two lines of corn screened as susceptible (CO447) and tolerant (CO450) to Goss’s wilt and leaf blight, respectively, were inoculated with Cn strains that possess different aggressiveness levels. The highly aggressive Cn strain (CMN14-5-1) produced severe symptoms on CO447, which quickly developed water soaked lesions, and then within a couple days, developed into necrotic lesions. However, symptoms on CO450 exhibited signs of chlorosis, freckling, and necrosis that did not progress, beyond the initial 6 days after inoculation, with the same strains, which were signs of programmed cell death (PCD) within the corn plant. Similar results were observed with the less aggressive Cn strain (DOAB232), though symptoms were less severe. Area under disease progress curve values were estimated for both lesion length and disease severity, which yielded significant differences amongst treatments. Analysis of the expression of 31 genes associated with plant defense was performed on plants challenged with each Cn strain. Four genes, peptidyl-prolyl cis-trans isomerase (PPI), ras-related protein 7 (Rab7), ribosome-inactivating proteins (RIP2), and respiratory burst oxidase homolog protein D (rbohD) were upregulated in CO450 RbohD is one of the genes responsible for reactive oxygen species (ROS) production, a key factor in PCD, so can be considered a defense factor in this study. Four genes, jasmonate-zim-domain protein 20 (jaz20), β subunit ATP synthase (βATP), allene oxide synthase (ZmAOS), and guanosine triphosphate (GTP)-binding protein (RabE1C) were upregulated in CO447. Based on their differential expression in the two corn lines in response to one or the strain, some genes may be suggested as contributors to either susceptibility or tolerance to Goss’s wilt and leaf blight. Along with other findings in Drs. Daayf, Tambong, and Stasolla’s lab, this knowledge can represent a foundation for developing cultivars with higher resistance to Cn.May 202
“Secreted in Xylem” Genes (SIX Genes): Relationship to the Aggressiveness of Fusarium oxysporum f. sp. albedinis
No full textFusarium oxysporum f. sp. Albedinis (Foa) is the causal agent of Bayoud disease, responsible for the loss of 75% of date palm trees in Morocco and posing a threat to its cultivation across North Africa. This study examined ten Foa isolated from various Moroccan locations for the presence of the transposable element Fot1 and the distribution of “Secreted in Xylem” (SIX) genes. Pathogenicity assays on date palm seedlings revealed varying levels of aggressiveness among isolates, with a positive correlation between aggressiveness and SIX gene count. Highly aggressive isolates harbored 9–12 SIX genes, while hypo-aggressive and moderately aggressive isolates carried 0–6. SIX2, SIX6, SIX7, SIX11, SIX12, and SIX13 were differently dispersed among aggressive isolates, whereas SIX12 and SIX13 were present in all aggressive isolates, suggesting their potential role in virulence. This study is the first to highlight a correlation between Foa aggressiveness and SIX gene distribution, providing a foundation for future functional analyses to elucidate their role in pathogenicity
The potential impact of pathogens on honey bee, Apis mellifera L., colonies and possibilities for their control
No full textExcessive honey bee colony losses all over the world are believed to be caused by multiple stressors. In this thesis, I characterized and quantified pathogen levels in honey bee colonies, studied their interactions with each other and with their associated parasite vectors, examined factors that influence their combined impacts on honey bees and developed methods to manage honey bee viruses so that colony losses can be minimized. My baseline study of virus prevalence and concentration in healthy and unhealthy (showing visible signs of disease) colonies in Canada showed that seven economically important viruses (DWV, BQCV, IAPV, KBV, SBV, ABPV, and CBPV) were all widely distributed in Canada. Differences in concentration and prevalence of some viruses were found between unhealthy and healthy colonies but these differences may have been due in part to seasonal or regional effects. Studies of the impact of viruses on worker bee populations over winter showed different factors were correlated with bee loss in different environments. Spring concentrations of DWV and mean abundance of Varroa (Varroa destructor) were positively correlated with bee loss and negatively correlated with spring population size in outdoor-wintered colonies. Fall concentration of IAPV was negatively correlated with spring population size of colonies in indoor-wintering environments but not in outdoor-environments. My study showed that it is important to consider location of sampling when associating pathogen loads with bee loss with Nosema and BQCV. Seasonal patterns of parasites and pathogens were characterized for each wintering methods (indoor and outdoor). My results revealed lower ABPV and Nosema ceranae prevalence and lower DWV concentration in genetically diverse than genetically similar colonies. I showed that within colony genetic diversity may be an important evolutionary adaptation to allow honey bees to defend against a wide range of diseases. In laboratory studies, I showed that feeding DWV to larvae in the absence of Varroa causes wing deformity and decreased survival rates of adult bees relative to bees not fed DWV. Finally, I showed that RNA silencing can be used to reduce DWV concentrations in immature and adult bees, reduce wing deformity in emerging adults, and increase their longevity relative to controls.May 201
Effects of glucan and eicosapetaeonoic acids on differential regulation on phenilpropanoids and mevalonic pathways during potato response to Phytophthora infestans
No full textThe effects of Phytophthora infestans glucans, eicosapentaenoic acid (EPA) and isolates of this pathogen, on the differential expression of eight genes from the phenylpropanoid and the mevalonate (Ac-MVA) pathways were analyzed in potato by semi-quantitative RT-PCR and qRT-PCR. The application of EPA had an elicitor effect in Russet Burbank (RB) and Defender (DF) in response to inoculation with a US8 isolate of P. infestans, thereby reducing symptoms of late blight. Such effect was associated with the expression of PAL-1 and PAL-2, since the latter occurred only when EPA was followed by inoculation, whereas these genes were down-regulated in individual treatments RB + EPA, RB + US8, DF + EPA, and DF + US8. The glucan fraction did not by itself suppress phenylpropanoid genes, but its combination with the pathogen resulted in a down-regulation of PAL-1, PAL-2 and CHS. The addition of the glucan fraction to the elicitor EPA, had a negative effect (RB + EPA + GL + US8) since plants showed higher disease symptoms than the ones pretreated with water then infected with US8, and in comparison with RB + EPA + US8 and RB + GL + US8. Exclusive up-regulation of 4CL in DF + US11 and of CHS in DF + EPA + GL + US8, DF + EPA + US11, DF + GL + US11 and DF + EPA + GL + US11, where late blight lesions were not detected, could be associated with potato protection against late blight. Along with previous findings in this pathosystem, these data suggest that genetic resistance in potato against P. infestans is not the result of isolated reactions against the pathogen, but rather the combination of many factors in-line with a polygenic/horizontal resistance.Fil: Henriquez, Maria A.. University Of Manitoba; CanadáFil: Wolski, Erika Alejandra. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Molina, Oscar I.. University Of Manitoba; CanadáFil: Adam, Lorne R.. University Of Manitoba; CanadáFil: Andreu, Adriana Balbina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Biológicas; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Daayf, Fouad. University Of Manitoba; Canad
Priming canola resistance to blackleg with weakly aggressive isolates leads to an activation of hydroxycinnamates
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