An isolate of 'Candidatus Phytoplasma australiense' group associated with Nivun Haamir dieback disease of papaya in Israel     

A. Gera  M. Mawassi  M. Zeidan  S. Spiegel  M. Bar-Joseph 《Plant pathology》2005,54(4):560-560

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Modeling the survival of two soilborne pathogens under dry structural solarization     

Shlevin E  Saguy IS  Mahrer Y  Katan J 《Phytopathology》2003,93(10):1247-1257

ABSTRACT Structural (space) solarization of a closed, empty greenhouse for sanitation involves dry heating to 60 degrees C and higher and low relative humidity (RH), under a fluctuating temperature and RH regime. Survival of inocula of Fusarium oxysporum f. sp. radicis-lycopersici and Sclerotium rolfsii during structural solarization was studied for 4 years (total of 12 experiments) in an attempt to develop a dynamic model for expressing the thermal inactivation of the pathogens. After 20 days of exposure, the populations of F. oxysporum f. sp. radicis-lycopersici and S. rolfsii were reduced by 69 to 95% and by 47.5 to 100%, respectively. The Weibull distribution model was applied to describe pathogen survival. The Weibull rate parameter, b, was found to follow an exponential (for F. oxysporum f. sp. radicis-lycopersici) and the Fermi (for S. rolfsii) functions at constant temperatures. To improve the applicability of the model, fluctuating conditions of both temperature and RH were utilized. The Weibull distribution derivative, expressed as a function of temperature and moisture, was numerically integrated to estimate survival of inocula exposed to structural solarization. Deviations between experimental and calculated values derived from the model were quite small and the coefficient of determination (R (2)) values ranged from 0.83 to 0.99 in 9 of 12 experiments, indicating that ambient RH data should be considered. Structural solarization for sanitation could be a viable component in integrated pest management programs.  相似文献   

Nematicidal activity of essential oils and their components against the root-knot nematode     

Oka Y  Nacar S  Putievsky E  Ravid U  Yaniv Z  Spiegel Y 《Phytopathology》2000,90(7):710-715

ABSTRACT Nematicidal activity of essential oils extracted from 27 spices and aromatic plants were evaluated in vitro and in pot experiments. Twelve of the twenty-seven essential oils immobilized more than 80% of juveniles of the root-knot nematode Meloidogyne javanica at a concentration of 1,000 mul/liter. At this concentration, most of these oils also inhibited nematode hatching. Essential oils of Carum carvi, Foeniculum vulgare, Mentha rotundifolia, and Mentha spicata showed the highest nematicidal activity among the in vitro tested oils. These oils and those from Origanum vulgare, O. syriacum, and Coridothymus capitatus mixed in sandy soil at concentrations of 100 and 200 mg/kg reduced the root galling of cucumber seedlings in pot experiments. The main components of these essential oils were tested for their nematicidal activity. Carvacrol, t-anethole, thymol, and (+)-carvone immobilized the juveniles and inhibited hatching at >125 mul/liter in vitro. Most of these components mixed in sandy soil at concentrations of 75 and 150 mg/kg reduced root galling of cucumber seedlings. In 3-liter pot experiments, nematicidal activity of the essential oils and their components was confirmed at 200 and 150 mg/kg, respectively. The results suggest that the essential oils and their main components may serve as nematicides.  相似文献   

Parasitism of <Emphasis Type="Italic">Trichoderma</Emphasis> on <Emphasis Type="Italic">Meloidogyne javanica</Emphasis> and role of the gelatinous matrix     

Edna Sharon  Ilan Chet  Ada Viterbo  Meira Bar-Eyal  Harel Nagan  Gary J. Samuels  Yitzhak Spiegel 《European journal of plant pathology / European Foundation for Plant Pathology》2007,118(3):247-258

Trichoderma (T. asperellum-203, 44 and GH11; T. atroviride-IMI 206040 and T. harzianum-248) parasitism on Meloidogyne javanica life stages was examined in vitro. Conidium attachment and parasitism differed beween the fungi. Egg masses, their derived eggs and second-stage juveniles (J2) were parasitized by Trichoderma asperellum-203, 44, and T. atroviride following conidium attachment. Trichoderma asperellum-GH11 attached to the nematodes but exhibited reduced penetration, whereas growth of T. harzianum-248 attached to egg masses was inhibited. Only a few conidia of the different fungi were attached to eggs and J2s without gelatinous matrix; the eggs were penetrated and parasitized by few hyphae, while J2s were rarely parasitized by the fungi. The gelatinous matrix specifically induced J2 immobilization by T. asperellum-203, 44 and T. atroviride metabolites that immobilized the J2s. A constitutive-GFP-expressing T. asperellum-203 construct was used to visualize fungal penetration of the nematodes. Scanning electron microscopy revealed the formation of coiling and appressorium-like structures upon attachment and parasitism by T. asperellum-203 and T. atroviride. Gelatinous matrix agglutinated T. asperellum-203 and T. atroviride conidia, a process that was Ca²⁺-dependent. Conidium agglutination was inhibited by carbohydrates, including fucose, as was conidium attachment to the nematodes. All but T. harzianum could grow on the gelatinous matrix, which enhanced conidium germination. A biomimetic system based on gelatinous-matrix-coated nylon fibers demonstrated the role of the matrix in parasitism: T. asperellum-203 and T. atroviride conidia attached specifically to the gelatinous-matrix-coated fibers and parasitic growth patterns, such as coiling, branching and appressoria-like structures, were induced in both fungi, similarly to those observed during nematode parasitism. All Trichoderma isolates exhibited nematode biocontrol activity in pot experiments with tomato plants. Parasitic interactions were demonstrated in planta: females and egg masses dissected from tomato roots grown in T. asperellum-203-treated soil were examined and found to be parasitized by the fungus. This study demonstrates biocontrol activities of Trichoderma isolates and their parasitic capabilities on M. javanica, elucidating the importance of the gelatinous matrix in the fungal parasitism.  相似文献   

Evaluation of Trichoderma spp. as a Biocontrol Agent Against Soilborne Fungi and Plant-parasitic Nematodes in Israel     

Yitzhak Spiegel  Ilan Chet 《Integrated Pest Management Reviews》1998,3(3):169-175

The optimal conditions required to market Trichoderma as a biocontrol agent against soilborne fungi and nematodes are discussed. These include a proper formulation, an efficient delivery system, and alternative methods for Trichoderma's application.The implementation of Trichoderma in integrated pest management (IPM) can be achieved using a soil treatment which combines reduced amounts of biocides/fungicides and the Trichoderma preparation. Biocontrol activity can be increased by combining two (or more) types of biocontrol agents. Moreover, the construction of a genetically modified Trichoderma can lead to the improvement of certain traits which are absent or not highly expressed in the native microorganism isolated from its natural habitat.Different Trichoderma harzianum and T. lignorum isolates were tested for their nematicidal activity against the root-knot nematode Meloidogyne javanica. In short-term experiments, improved growth of nematode-infected plants and decreases in the root-galling index and the number of eggs per gram of root were achieved when nematode-infested soils were pre- exposed to the T. harzianum preparations. A long-term experiment resulted in improved growth and higher yield of nematode-infected plants, but no significant change in the galling index, either by pre-exposure of the fungus to the soil or by enrichment in the root-ball.As biocontrol is an integral part of the IPM philosophy, judicious use of Trichoderma against soilborne pathogens, when demonstrated to be consistently effective, practical and economic, can serve as a model for the introduction and implementation of other biocontrol means into IPM.  相似文献   

Abscisic acid, gibberellin and cell viability in cereal aleurone   总被引：3，自引：0，他引：3  

Paul C. Bethke  Angelika Fath  Yoav N. Spiegel  Yong-sic Hwang  Russell L. Jones 《Euphytica》2002,126(1):3-11

The aleurone layer of cereals is a secretory tissue whose activity is regulated by abscisic acid (ABA) and gibberellins (GAs). Whereas GA triggers enzyme synthesis and secretion and initiates a program that culminates in cell death, ABA prevents enzyme production and cell death. Reactive oxygen species (ROS) are key players in regulating cell viability and GA sensitizes the aleurone cell to ROS. Sensitivity of GA-treated cells results in part from a reduction in steady-state amounts of mRNAs encoding enzymes that scavenge ROS. mRNAs encoding catalase, superoxide dismutase and ascorbate peroxidase are almost undetectable in aleurone layers 24 h after incubation in GA. For layers incubated in ABA, however, the amounts of these mRNAs increase. Western blotting and enzyme activity assays confirm that GA but not ABA reduced the amount and activity of ROS scavenging enzymes (Fath et al., 2001b). Substantial amounts of ROS are produced by enzymes engaged in lipid metabolism, and by the electron transport chain in the mitochondria. Aleurone layers contain abundant stores of triglycerides and ROS are produced as these lipids are rapidly converted to sugars. We hypothesize that the ROS produced in GA-treated aleurone cells bring about cell death by disrupting the plasma membrane. Aleurone cells incubated in ABA, on the other hand, are better able to maintain redox balance. ABA does not initiate rapid triglyceride metabolism, and the activities of ROS-scavenging enzymes remain high in ABA-treated cells. We conclude that GA initiates a metabolic cascade in aleurone cells that results in death from ROS. ABA maintains viability by keeping ROS under control. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Prolactin and growth hormone release by morphine in the rat: different receptor mechanisms   总被引：5，自引：0，他引：5  

K Spiegel  I A Kourides  G W Pasternak 《Science (New York, N.Y.)》1982,217(4561):745-747

Concentrations of prolactin and growth hormone in the serum of rats were significantly increased by morphine. Dose response studies demonstrated that maximum prolactin release required lower doses of morphine than those needed for the maximum growth hormone response. Selective blockade of mu 1 (high affinity) opiate receptor with the irreversible antagonist naloxazone reduced morphine-induced peak concentrations of prolactin by 80 percent while increasing peak growth hormone levels by 250 percent. These results suggest different receptor mechanisms for the opiate modulation of the two hormones. The mu 1 (high affinity) receptor sites appear to mediate the morphine-induced release of prolactin but not growth hormone.  相似文献   

PTSD and Vietnam Veterans     

Vermetten E  Bremner JD  Skelton L  Spiegel D 《Science (New York, N.Y.)》2007,315(5809):184-7; author reply 184-7

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Suppressive compost: when plant pathology met microbial ecology     

Yitzhak Hadar 《Phytoparasitica》2011,39(4):311-314

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Agriculture as a source of phosphorus causing eutrophication in Central and Eastern Europe   总被引：5，自引：0，他引：5  

P. Csathó    I. Sisák    L. Radimszky    S. Lushaj    H. Spiegel    M. T. Nikolova    N. Nikolov    P. &#;ermák    J. Klir    A. Astover    A. Karklins    S. Lazauskas    J. Kopi&#;ski    C. Hera    E. Dumitru    M. Manojlovic    D. Bogdanovi&#;    S. Torma    M. Lesko&#;ek  & A. Khristenko 《Soil Use and Management》2007,23(S1):36-56

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