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Nevain A. S. Messiha Ariena H. C. van Bruggen Anne D. van Diepeningen Oscar J. de Vos Aad J. Termorshuizen N. N. A. Tjou-Tam-Sin J. D. Janse 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(4):367-381
Ralstonia solanacearum race 3 biovar 2, the causative agent of potato brown rot (bacterial wilt), is an economically important disease in tropical,
subtropical and temperate regions of the world. In view of previous reports on suppression of the disease by organic amendments,
and the expansion of organic agriculture, it was timely to compare the effects of organic and conventional management and
various amendments on brown rot development in different soils (type: sand or clay; origin: Egypt or the Netherlands). Brown
rot infection was only slightly reduced in organically compared to conventionally managed sandy soils from Egypt, but organic
management significantly increased disease incidence and pathogen survival in Dutch sandy and clay soils, which correlated
with high DOC contents in the organic Dutch soils. There was no correlation between disease incidence or severity and bacterial
diversity in the potato rhizosphere in differently managed soils (as determined by 16S DGGE). NPK fertilization reduced bacterial
wilt in conventional Egyptian soils but not in Dutch soils. Cow manure amendment significantly reduced disease incidence in
organic Dutch sandy soils, but did not affect the bacterial population. However, cow manure did reduce densities of R. solanacearum in Egyptian sandy soils, most probably by microbial competition as a clear shift in populations was detected with DGGE in
these and Dutch sandy soils after manure amendment. Amendment with compost did not have a suppressive effect in any soil type.
The absence of a disease suppressive effect of mineral and organic fertilization in Dutch clay soils may be related to the
already high availability of inorganic and organic nutrients in these soils. This study shows that the mechanism of disease
suppression of soil-borne plant pathogens may vary strongly according to the soil type, especially if quite different types
of soil are used. 相似文献
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Jan Peter van der Hoek Wim F. van der Hoek Abraham Klapwijk 《Water, air, and soil pollution》1988,37(1-2):41-53
A new, strong base, macro-porous anion exchange resin, Amberlite IRA 996, appeared to be more nitrate selective than sulfate selective in treating high nitrate concentrations (18 mg NO inf3 sup? -N L?1) in potable water. When regeneration is carried out in a closed circuit in which a biological denitrification reactor is incorporated to remove nitrate from the regenerant, regeneration salt requirement and brine production can be minimized. In this combination of ion exchange and biological denitrification, regeneration with 30 g NaHCO3 L?1) is possible in 6 hr at a flow rate of 11 BV hr?1. Accumulation of sulfate in the closed regeneration circuit does not affect the nitrate capacity of the resin. 相似文献
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H. M. G. van der Werf J. Hoek M. J. Soepboer 《Journal of Agronomy and Crop Science》1989,162(1):43-48
A proportion of the maize seed sold in the Netherlands is genetically impure. The most common form of genetic impurity in hybrid seed production is the accidental self-pollination of the female parent. Varying quantities of selfed seeds were added to certified seedlots of three-way cross hybrids. These mixtures were tested in nine field experiments, in 1985 and 1986.
Whole plant dry matter yield decreased by 40 to 45 kg/ha per percent of selfed seed added. The effect of selfed seed on dry matter yield did not differ significantly in the hybrids studied. 相似文献
Whole plant dry matter yield decreased by 40 to 45 kg/ha per percent of selfed seed added. The effect of selfed seed on dry matter yield did not differ significantly in the hybrids studied. 相似文献
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Effects of polyunsaturated fatty acids on the proliferation of mitogen stimulated bovine peripheral blood mononuclear cells 总被引:1,自引:0,他引:1
Thanasak J Müller KE Dieleman SJ Hoek A Noordhuizen JP Rutten VP 《Veterinary immunology and immunopathology》2005,104(3-4):289-295
The present study aimed at analysis of the effects of polyunsaturated fatty acid (PUFA), linoleic acid (LA, C18:2n - 6) and linolenic acid (LNA, C18:3n - 3) on bovine peripheral blood mononuclear cells (PBMC) in vitro. Both mitogen (ConA)-induced proliferative lymphocyte responsiveness during 4 days of culture and eicosanoid (prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4))) production during 36 h were determined in relation to the absence or presence of various concentrations of LA and LNA (0, 1, 5, 25, 125 and 250 microM). Mitogen-driven proliferative responses of lymphocytes tended to be uninfluenced in the presence of lower concentrations of LA, whereas significant inhibition was observed at the higher concentrations of LA (125 and 250 microM). However, increasing amounts of LNA did not affect the proliferation. ConA stimulation induced a clear PGE(2) response, which significantly decreased in the presence of 250 microM of LA. In addition, increasing amounts of LNA, but not LA, led to a significant decrease in LTB(4) levels. However, The production of LTB(4) did not alter due to mitogenic stimulation. In conclusion, the present study shows that bovine mononuclear cells may functionally be influenced by the presence of PUFA in their environment. Further studies need to be conducted to clarify in vivo consequences of these findings in a situation of PUFA enriched rations in ruminants. 相似文献
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ABSTRACT The effect of mixed cropping on disease suppressiveness of soils was tested for two cropping systems, Brussels sprouts-barley and triticale-white clover. Disease suppressiveness of field soils was evaluated in bioassays for the soilborne pathogens Rhizoctonia solani, Fusarium oxysporum f. sp. lini, and Gaeumannomyces graminis var. tritici. For both cropping systems, mixed cropping did not enhance disease suppressiveness of the soils. In some cases, soil cropped to barley alone was significantly more suppressive to F. oxysporum f. sp. lini than soils cropped to Brussels sprouts or the mixture of Brussels sprouts and barley. Analyses of the diversity of the indigenous bacterial and fungal microflora by denaturing gradient gel electrophoresis of amplified 16S- and 18S-rDNA fragments, respectively, revealed, in most cases, no significant differences between mixed and mono-cropped soils. In conclusion, in this study, mixed cropping of soils with Brussels sprouts and barley or with triticale and white clover did not enhance microbial diversity or disease suppressiveness of soils to three different soilborne plant pathogens. 相似文献
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Possible Root Infection of Cercospora beticola in Sugar Beet 总被引:1,自引:0,他引:1
Jessica Vereijssen Hans J.H.M. Schneider Aad A.J. Termorshuizen 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(1):103-106
A potential primary infection site of the foliar pathogen Cercospora beticola in sugar beet is described. Sugar beet seedlings of the susceptible cv. Auris were grown in a standard soil for 14 days. A monoconidial culture of a C. beticola isolate was grown to produce conidia. In experiment 1, roots were immersed in a conidial suspension of isolate code IRS 00-4, or in tap water (control), for 2 days. After incubation seedlings were potted in a peat – fine river sand mixture and placed at low relative humidity (RH) (<80%) or high RH (100%). Twelve days after infection, seedlings at high RH showed more disease incidence (90%) than seedlings grown at low RH (disease incidence = 25%), whereas no disease symptoms developed in the control seedlings. Cercospora leaf spots (CLSs) developed on the cotyledons, leaves, petioles and stems of the seedlings. In experiment 2, roots were immersed in a conidial suspension of isolate code IRS 00-2 for 5 h. Thirty-four days after infection at high RH, 100% disease incidence was observed in the treated seedlings and one CLS in the control treatment. First indications of leaf spot development were observed as reddish purple discolouration of individual parenchymatic cells. Because splash dispersal and symptoms due to infested soil were excluded, we showed that it is possible to obtain CLS symptoms in sugar beet seedlings when their roots were immersed in conidial suspensions of C. beticola, thus demonstrating that roots can be a primary infection site. 相似文献
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Thanasak J Jorritsma R Hoek A Noordhuizen JP Rutten VP Müller KE 《Veterinary research》2004,35(1):103-112
Dexamethasone is a potent therapeutic for treatment of the fatty liver syndrome or primary ketosis in post partum dairy cows. Reservations exist, however, among practitioners with respect to the risk of immunosuppression induced by corticosteroids. The aim of this study was to investigate the effect of a single injection of dexamethasone-21-isonicotinate on distinct immune functions of postpartum dairy cows because only scarce information is available on the effects of corticosteroid preparations when administered at a dosage and frequency for treatment of the fatty liver syndrome or primary ketosis. Sixteen Swedish red-pied dairy cows, between days 9 and 15 post partum, were allotted to either a control group (n = 8) or a treatment group (n = 8). The cows in the treatment group received a single intramuscular injection of a dexamethasone-21-isonicotinate suspension at a dosage of 0.02 mg/kg i.m. at the start of the experiment. White blood cell counts and selected lymphocyte functions (lymphocyte proliferation, expression of lymphocyte markers and the b2 and a4 chain of adhesion molecules belonging to the integrin family) and some parameters of the energy metabolism (glucose, insulin) were determined before the administration of corticosteroids (day 0) and subsequently at days 2, 4, 7 and 9 of the experiment. Changes in glucose and insulin were within the target range for treatment of the fatty liver syndrome or primary ketosis. Significant (P < 0.05) increases in the number of circulating white blood cells were observed in treated cows on the second day following treatment which was exclusively caused by an increase in the number of circulating neutrophils. Lymphocyte blastogenesis in response to ConA and the percentages of lymphocytes positive for CD2, CD4, CD8, CD49d and CD18 as well as the intensity of CD49d expression did not differ between the treatment and control groups. There was, however, a significant reduction (P < 0.01) in the intensity of CD18 expression on lymphocytes in the treated animals on the fourth day after treatment. In conclusion, a single administration of dexamethasone-21-isonicotinate in a dosage of 0.02 mg/kg i.m. at two weeks post partum in healthy cows had a significant but highly transient effect on CD18 expression on lymphocytes and the number of peripheral blood neutrophils, but did not affect lymphocyte blastogenesis or lymphocyte subpopulation patterns in peripheral blood. 相似文献
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Cattle genetically selected for twin ovulations and births (Twinner) exhibit increased ovarian follicular development, increased ovulation rate, and greater blood and follicular fluid IGF-1 concentrations compared with contemporary cattle not selected for twins (Control). Experimental objectives were to 1) assess relationships among aromatase (CYP19A1), IGF-1 (IGF1), IGF-2 receptor (IGF2R), and FSH receptor (FSHR) mRNA expression in small (≤5 mm) antral follicles and 2) determine their association with increased numbers of developing follicles in ovaries of Twinner females. Ovaries were collected from mature, cyclic (d 3 to 6) Twinner (n = 11), and Control (n = 12) cows at slaughter and pieces of cortical tissue were fixed and embedded in paraffin. Expression of mRNA was evaluated by in situ hybridization using (35)S-UTP-labeled antisense and sense probes for CYP19A1, FSHR, IGF1, and IGF2R mRNA. Silver grain density was quantified within the granulosa and theca cells of individual follicles (2 to 7 follicles/cow) by Bioquant image analysis. Follicles of Twinners tended to be smaller in diameter than Controls (1.9 ± 0.1 vs. 2.3 ± 0.1 mm; P = 0.08), but thickness of granulosa layer did not differ (P > 0.1) by genotype. Relative abundance of CYP19A1 (P < 0.01) and FSHR (P < 0.05) mRNA was greater in granulosa cells of Twinners vs. Controls, respectively, whereas IGF2R mRNA expression was less in both granulosa (P < 0.01) and theca (P < 0.05) cells in follicles of Twinners vs. Controls, respectively. Abundance of CYP19A1 mRNA in granulosa cells was correlated negatively with IGF2R mRNA expression in both granulosa (r = -0.33; P < 0.01) and theca (r = -0.21; P = 0.05) cells. Expression of IGF1 mRNA was primarily in granulosa cells, including cumulus cells, and its expression did not differ between Twinners vs. Controls (P > 0.10). Detected increases in CYP19A1 and FSHR, but not IGF1, mRNA expression along with decreases in IGF2R mRNA expression in individual follicles of Twinners support the hypothesis that increased follicular development and steroidogenesis in Twinner females result from increased extra-ovarian IGF-1 production. Furthermore, a reduction in follicular IGF2R mRNA expression accompanied by a reduction in receptor numbers would increase availability of free IGF-2 and its stimulation of follicular development in Twinners. 相似文献