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    Accumulation of cell-wall bound phenolic compounds and phytoalexin in Arabidopsis thaliana leaves following inoculation with pathovars of Pseudomonas syringae
    (Elsevier Ireland Ltd, 2006) Soylu, S
    Here we have examined genetically well-defined interactions in leaves of Arabidopsis ecotype Col-5 during compatible and incompatible interactions with isogenic pairs of Pseudomonas syringae pathovars tomato (Pst) DC3000 and phaseolicola (Pph) 1448A strains differing only in the presence or absences of cloned avr genes that determine the compatibility and incompatibility of the reaction. Strain Pst DC3000 was virulent causing formation of a spreading lesion surrounded by a chlorotic halo. The bean pathogen Pph 1448A (as a non-host pathogen) caused no visible symptoms apart from very patchy discolouration after 3 days. The presence of the avirulence genes avrPpiA and avrPphB in Pph 1448A led to a rapid or slow HR owing to interaction with the resistance genes RPM1 and RPS5 respectively. The hrpL mutant of Pph failed to produce symptoms. Microscopical and biochemical studies were used for in situ localization of plant molecules involved in plant resistance such as autofluorescent phenolics, lignin and camalexin. A strong correlation was observed between the timing and extent of cell death and high levels of phenolic and lignin accumulation in cell-walls and cytoplasm of cells undergoing the HR, whereas no staining of lignin-like material was observed during the compatible interaction. Accumulation of phytoalexin, camalexin, was associated with tissue necrosis whether during the HR or a susceptible response. Although high levels of camalexin were found within tissues inoculated with the virulent strain DC3000, the earliest detection of camalexin occurred during HR following inoculation with avirulent strain. The results indicate that accumulation of phenolics but not camalexin may be involved in resistance against bacterial pathogens used in this study. (c) 2006 Elsevier Ireland Ltd. All rights reserved.
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    Antimicrobial activities of the essential oils of various plants against tomato late blight disease agent Phytophthora infestans
    (Springer, 2006) Soylu, EM; Soylu, S; Kurt, S
    The aim of this study was to find an alternative to synthetic fungicides currently used in the control of devastating oomycete pathogen Phytophthora infestans, causal agent of late blight disease of tomato. Antifungal activities of essential oils obtained from aerial parts of aromatic plants such as oregano (Origanum syriacum var. bevanii), thyme (Thymbra spicata subsp. spicata), lavender (Lavandula stoechas subsp. stoechas), rosemary (Rosmarinus officinalis), fennel (Foeniculum vulgare), and laurel (Laurus nobilis), were investigated against P. infestans. Both contact and volatile phase effects of different concentrations of the essential oils used were determined by using two in vitro methods. Chemical compositions of the essential oils were also determined by GC-MS analysis. Major compounds found in essential oils of thyme, oregano, rosemary, lavender, fennel and laurel were carvacrol (37.9%), carvacrol (79.8), borneol (20.4%), camphor (20.2%), anethole (82.8%) and 1,8-cineole (35.5%), respectively. All essential oils were found to inhibit the growth of P. infestans in a dose-dependent manner. Volatile phase effect of oregano and thyme oils at 0.3 mu g/ml air was found to completely inhibit the growth of P. infestans. Complete growth inhibition of pathogen by essential oil of fennel, rosemary, lavender and laurel was, however, observed at 0.4-2.0 mu g/ml air concentrations. For the determination of the contact phase effects of the tested essential oils, oregano, thyme and fennel oils at 6.4 mu g/ml were found to inhibit the growth of P. infestans completely. Essential oils of rosemary, lavender and laurel were inhibitory at relatively higher concentrations (12.8, 25.6, 51.2 mu g/ml respectively). Volatile phase effects of essential oils were consistently found to be more effective on fungal growth than contact phase effect. Sporangial production was also inhibited by the essential oil tested. Light and scanning electron microscopic (SEM) observation on pathogen hyphae, exposed to both volatile and contact phase of oil, revealed considerable morphological alterations in hyphae such as cytoplasmic coagulation, vacuolations, hyphal shrivelling and protoplast leakage.
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    Basal defenses induced in pepper by lipopolysaccharides are suppressed by Xanthomonas campestris pv. vesicatoria
    (Amer Phytopathological Soc, 2004) Keshavarzi, M; Soylu, S; Brown, I; Bonas, U; Nicole, M; Rossiter, J; Mansfield, J
    The nonpathogenic hrcC mutant of Xanthomonas campestris pv. vesicatoria 85-10
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    Cellular reactions in Arabidopsis following challenge by strains of Pseudomonas syringae
    (Academic Press Ltd- Elsevier Science Ltd, 2005) Soylu, S; Brown, I; Mansfield, JW
    Reactions to strains of the bean halo-blight pathogen Pseudomonas syringae pv. phaseolicola (Pph) strain 1448A and the Arabidopsis and tomato pathogen P.s. pv. tomato (Pst) strain DC3000 were examined by transmission electron microscopy. Wild-type and hrpL mutant strains of Pph failed to multiply in the accession Columbia (Col)-5, but did not cause a hypersensitive reaction (HR). Symptomless non-host resistance to 1448A and the hrpL mutant was associated with the progressive alteration of the plant cell wall adjacent to bacteria, following the accumulation of membrane bound vesicles within the cytoplasm at reaction sites. Large papillae containing callose accumulated within challenged plant cells. Papillae also formed in the pmr4-1 mutant of Col-0 which lacks an inducible callose synthase but immunocytochemical labelling demonstrated that they contained very little beta-1, 3 glucan. Some papillae formed in Col-5 in response to the virulent pathogen DC3000, but they dispersed during cell collapse and lesion formation. Transconjugants of Pph expressing the avirulence genes avrPpiA and avrPphB matching the RPM1 and RPS5 resistance genes, caused rapid and slow HR development, respectively. Although corpse morphology was observed our observations suggest that in Arabidopsis, plant cell death during the HR is programmed but represents a variant of necrosis rather than apoptosis. Cerium chloride staining revealed the accumulation of H2O2 at reaction sites. The strongest H2O2 response was found during the HR activated by avrPpiA but localised generation of peroxide was also found at sites of papilla deposition next to 1448A or the hrpL mutant. Accumulation of H2O2 during the HR, but not during wall alterations, was strongly suppressed by inhibition of NADPH oxidase. The differential effect of the inhibitor suggests an alternative source of H2O2 to modify the plant wall. Extension of peroxide-driven cross-linking reactions to bacterial cell walls may contribute to the restriction of bacterial multiplication. The lowest level of H2O2 occurred during the compatible reaction to DC3000. Characterisation of the cellular co-ordination of basal (non-host) resistance has revealed several potential targets for bacterial effector proteins. (c) 2005 Elsevier Ltd. All rights reserved.
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    Chemical composition and antifungal activity of the essential oil of Artemisia annua L. against foliar and soil-borne fungal pathogens
    (Eugen Ulmer Gmbh Co, 2005) Soylu, EM; Yigitbas, H; Tok, FM; Soylu, S; Kurt, S; Baysal, Ö; Kaya, AD
    The chemical composition of the essential oil of Artemisia annua L. was determined by GC/MS analysis. Among the thirty-seven constituents found, camphor (31.7 %), artemisia ketone (22.3 %), 1,8-cincole (10.1 %), caryophyllene oxide (7.1 %), alpha-copaene (3.4 %) and camphene (3-3 %) were the major components. The in vitro antifungal activity of the essential oil was evaluated against economically important foliar and soil-borne fungal pathogens of tomato, including Sclerotinia sclerotiorum, Botrytis cinerea, Phytophthora infestans and Verticillium dahliae. Both contact and volatile phase effects of different concentrations of the essential oil were determined by using two different methods. Amongst the fungal isolate, S. sclerotiorum was found to be highly sensitive to volatile and contact phase of the essential oil. Minimum fungicidal concentrations of the volatile phase of the essential oil for S. sclerotiorum, B. cinerea, P. infestans and V. dahliae were 1.6, 2.4, 2.4 and 4.4 mu g/ml air, respectively. The essential oil in the contact phase showed minimum fungicidal concentration ranging from 6.4 mu g/ ml to 51.2 mu g/ml. Volatile and contact phase of the essential oils, at 2.4 and 51.2 mu g/ml concentrations, were found to completely inhibit the conidial germination and germ tube elongation of both fungal pathogen tested.
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    First report of alternaria leaf blight caused by Alternaria dauci on carrot in Turkey
    (Blackwell Publishing Ltd, 2005) Soylu, S; Kurt, S; Soylu, EM; Tok, FM
    [Abstract Not Available]
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    First report of cercospora leaf spot on Swiss chard caused by Cercospora beticola in Turkey
    (Blackwell Publishing Ltd, 2003) Soylu, S; Soylu, EM; Kurt, S
    [Abstract Not Available]
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    First report of crater rot caused by Rhizoctonia carotae on carrots (Daucus carota) in Turkey
    (Wiley, 2005) Kurt, S; Soylu, EM; Soylu, S; Tok, FM
    [Abstract Not Available]
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    First report of downy leaf spot of walnuts caused by Microstroma juglandis in Turkey
    (Blackwell Publishing Ltd, 2003) Kurt, S; Soylu, EM; Soylu, S
    [Abstract Not Available]
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    First report of phloeospora leaf spot on mulberry caused by Phloeospora maculans (= Cylindrosporium maculans) in the East Mediterranean region of Turkey
    (Blackwell Publishing Ltd, 2003) Soylu, S; Kurt, S; Soylu, EM
    [Abstract Not Available]
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    First report of powdery mildew caused by Erysiphe heraclei on dill (Anethum graveolens) in Turkey
    (Blackwell Publishing Ltd, 2003) Soylu, EM; Soylu, S
    [Abstract Not Available]
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    First report of powdery mildew caused by Leveillula taurica on leek (Allium porrum) in Turkey
    (Wiley, 2004) Kurt, S; Soylu, S; Soylu, EM; Tok, FM
    [Abstract Not Available]
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    First report of powdery mildew caused by Podosphaera phaseoli (syn. Sphaerotheca phaseoli) on cowpea (Vigna sinensis) in Turkey
    (Blackwell Publishing Ltd, 2004) Soylu, EM; Soylu, S; Kurt, S
    [Abstract Not Available]
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    First report of powdery mildew on mulberry caused by Phyllactinia guttata in the eastern Mediterranean region of Turkey
    (Blackwell Publishing Ltd, 2001) Kurt, S; Soylu, S
    [Abstract Not Available]
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    Induction of defence-related enzymes and resistance by the plant activator acibenzolar-S-methyl in tomato seedlings against bacterial canker caused by Clavibacter michiganensis ssp michiganensis
    (Blackwell Publishing Ltd, 2003) Baysal, Ö; Soylu, EM; Soylu, S
    Using tomato seedlings, the plant defence activator acibenzolar-S-methyl (benzo-[1,2,3]-thiadiazole-7-carbothioic acid-S-methyl ester, ASM; Bion 50 WG) was assayed for its ability to induce resistance against Clavibacter michiganensis ssp. michiganensis, the causal agent of bacterial canker of tomato. In ASM-pretreated plants, reduction in disease severity (up to 76.3%) was correlated with lower bacterial growth (up to 68.2% lower) during the time course of infection. To understand the possible mechanism of action of ASM, alterations in the activities of peroxidase (POX) and chitinase were assessed as markers of resistance. The enhanced resistance of ASM-treated plants was associated with significant increases in the activities of POX and chitinase.
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    Induction of disease resistance and antioxidant enzymes by acibenzolar-S-methyl against bacterial canker (Clavibacter michiganensis subsp michiganensis) in tomato
    (Springer, 2003) Soylu, EM; Soylu, S; Baysal, Ö
    The plant defence activator acibenzolar-S-methyl (Bion) was assayed on tomato seedlings for its ability to induce multicomponent defence response against Clavibacter michiganensis subsp. michiganensis (Cmm). Pretreatment of plants with ASM reduced the severity of the disease as well as the growth of the bacteria in planta. In ASM-treated plants, reduction in disease severity (up to 75 %) was correlated with the suppression of bacterial growth (up to 68.2%) during the time course of infection. In plants treated with ASM, activities of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione S-transferase (GST) were estimated as markers of resistance. The results indicated that ASM treatment led to enhanced activities of SOD and GST in tomato leaves. A slightly increase in SOD and GST activities was also found in Cmm-infected leaves. However, the increase in enzyme activities occurred much more rapidly and was more strongly enhanced in Cmm-infected leaves that were previously treated with ASM. The involvement of both enzymes in ASM mediated resistance in tomato is discussed.
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    Induction of disease resistance by the plant activator, acibenzolar-S-methyl (ASM), against bacterial canker (Clavibacter michiganensis subsp michiganensis) in tomato seedlings
    (Elsevier Sci Ireland Ltd, 2003) Soylu, S; Baysal, Ö; Soylu, EM
    The plant defence activator acibenzolar-S-methyl (benzo [1,2,3]thiadiazole-7-carbothioic acid-S-methyl ester, ASM; Bion 50 WG) was assayed on tomato seedlings for its ability to induce resistance against Clavibacter michiganensis subsp. michiganensis (Cmm), the causal agent of bacterial canker of tomato. Pre-treatment of plants with ASM reduced the severity of the disease as well as the growth of the bacteria in planta. In ASM-treated plants, reduction in disease severity (up to 75%) was correlated with suppression of bacterial growth (up to 68.2%) during the time course of infection. In plants treated with ASM, activities of peroxidase (POX) and glutathione peroxidase (GPX) were determined as markers of resistance. Applications of ASM induced a progressive and significant increase of both enzymes in locally treated tissues. Such responses were expressed earlier and with a much higher magnitude when ASM-treated seedlings were challenged with the pathogen, thus providing support to the concept that a signal produced by the pathogen is essential for triggering enhanced synthesis and accumulation of these enzymes. No such activities were observed in water-treated control plants. Therefore, the slower symptom development and reduction in bacterial growth in ASM-treated plants might be due to the increase in activity of both oxidative and antioxidative protection systems in planta. (C) 2003 Elsevier Ireland Ltd. All rights reserved.
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    Light and electron microscopy of the compatible interaction between Arabidopsis and the downy mildew pathogen Peronospora parasitica
    (Wiley, 2003) Soylu, EM; Soylu, S
    In this study, we focused on compatible interactions between Peronospora parasitica isolate Emoy-2 and wild-type (Oy-0) and mutant (Ws-eds1 ) Arabidopsis thaliana accessions by using light and transmission electron microscopy (TEM). Light microscopy of compatible interactions revealed that conidia germinated and penetrated through the anticlinal cell walls of two epidermal cells. Rapid spreading of the hyphal growth with formation of numerous haustoria within the mesophyll cells was subsequently followed by profuse sporulation in the absence of host cell necrosis on both wild-type and mutant accessions. TEM observations revealed that coenocytic intercellular hyphae ramified and spread intercellularly throughout the host tissue forming several haustoria in host mesophyll cells. Intracellular haustoria were lobed with the diameter of 6-7 mum. Each haustorium was connected to intercellular hyphae in the absence of apparent haustorial neck. The cytoplasm of the haustorium included the organelles characteristic of the pathogen. Callose-like deposits were frequently observed at sites of penetration around the proximal region of the haustorial neck. Apart from a few callose ensheatments, no obvious response was observed in host cells following formation of haustoria. Most of mesophyll cells contained normal haustoria and the host cytoplasm displayed a high degree of structural integrity. Absence of host cell wall alteration and cell death in penetrated host cell of both accessions suggest that the pathogen exerts considerable control over basic cellular processes and in this respect, response to this biotroph oomycete differs considerably from responses to other pathogens such as necrotrophs.
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    Preliminary characterization of race-specific elicitors from Peronospora parasitica and their ability to elicit phenolic accumulation in Arabidopsis
    (Priel Publ, 2003) Soylu, S; Soylu, EM
    Intercellular washing fluid (IWF) obtained from the susceptible Arabidopsis accession Ws-eds1 inoculated with Peronospora parasitica isolate Emoy-2, contained an elicitor of necrosis with ecotype specificity towards Arabidopsis accessions with particular resistance genes. This elicitor caused necrosis on the highly resistant accessions La-er, Nd-1 and partly on Col-5, but not on the susceptible accessions Ws-eds1 and Oy-0. In resistant plants, injection of IWF caused hypersensitive reaction (HR)-like cell collapse which was associated with the accumulation of phenolics and lignin-like material in walls of cells undergoing cell death. The elicitor is sensitive to proteinase K and pronase enzymes, heating and autoclaving but insensitive to periodate oxidation, freezing and thawing, and is not dialyzable. Results suggest that the elicitor is a protein. Fractionation experiments using size-exclusion membranes revealed that elicitor activity has a molecular weight in excess of 100 kDa.