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1.
Effects of light leaf spot (Pyrenopeziza brassicae) on yield of winter oilseed rape (Brassica napus)
H. SU B D L FITT S J WELHAM C E SANSFORD K G SUTHERLAND 《The Annals of applied biology》1998,132(3):371-386
The relationship between development of light leaf spot and yield loss in winter oilseed rape was analysed, initially using data from three experiments at sites near Aberdeen in Scotland in the seasons 1991/92, 1992/93 and 1993/94, respectively. Over the three seasons, single-point models relating yield to light leaf spot incidence (% plants with leaves with light leaf spot) at GS 3.3 (flower buds visible) generally accounted for more of the variance than single-point models at earlier or later growth stages. Only in 1992/93, when a severe light leaf spot epidemic developed on leaves early in the season, did the single-point model for disease severity on leaves at GS 3.5/4.0 account for more of the variance than that for disease incidence at GS 3.3. In 1991/92 and 1992/3, when reasonably severe epidemics developed on stems, the single-point model for light leaf spot incidence (stems) at GS 6.3 accounted for as much of the variance. Two-point (disease severity at GS 3.3 and GS 4.0) and AUDPC models (disease incidence/severity) accounted for more of the variance than the single-point model based on disease incidence at GS 3.3 in 1992/93 but not in the other two seasons. Therefore, a simple model using the light leaf spot incidence at GS 3.3 (x) as the explanatory variable was selected as a predictive model to estimate % yield loss (yr): yr= 0.32x– 0.57. This model fitted all three data sets from Scotland, When data sets from Rothamsted, Rosemaund and Thurloxton in England were used to test it, this single-point predictive model generally fitted the data well, except when yield loss was clearly not related to occurrence of light leaf spot. However, the regression lines relating observed yield loss to light leaf spot incidence at GS 3.3 often had smaller slopes than the line produce, by the model based on Scottish data. 相似文献
2.
Factors affecting development of phoma canker (Leptosphaeria maculans) on stems of winter oilseed rape (Brassica napus) in southern England 总被引:2,自引:0,他引:2
P SUN B D L FITT J M STEED C T UNDERWOOD J S WEST 《The Annals of applied biology》2001,139(2):227-242
In winter oilseed rape experiments at Rothamsted in 1997/98 (cvs Lipton and Capitol), 1998/99 (cv. Apex) and 1999/2000 (cvs Apex, Lipton and Capitol), development of crown canker and phoma stem lesions in spring was related to development of phoma leaf spot in the previous autumn/winter. There were differences in thermal time (degree‐days) from the first appearance of phoma leaf spot (autumn) to the first appearance of crown canker (spring) between cultivars (cvs Lipton and Capitol, 1220–1240; cv. Apex, 1120–1140 degree‐days) but not between growing seasons. In 1998/99 and 1999/2000, fungicide (November) treatment delayed the start of crown canker development in the spring but did not affect the rate of increase in severity. In 1997/98, fungicide treatments did not delay the appearance of crown canker but decreased the rate of increase in crown canker severity. In all three seasons, fungicide treatments generally decreased the proportions of plants at harvest with crown canker severity scores 3 or 4 and increased the proportions with scores 0 or 1. There were differences between seasons in the distributions of crown canker severity scores at harvest. The severity of both crown canker and phoma stem lesions increased linearly with accumulated degree‐days in plots with or without fungicide treatment in 1997/98 (cv. Lipton), 1998/99 (cv. Apex) and 1999/2000 (cv. Apex). Regressions showed that severity of crown canker at harvest in July was related to severity in the spring in 1997/98 (early June, cv. Lipton), 1998/99 and 1999/2000 (April, cv. Apex). 相似文献
3.
S.J. Powers E.J. Pirie A.O. Latunde-Dada B.D.L. Fitt 《The Annals of applied biology》2010,157(1):55-70
Development of phoma leaf spot (caused by Leptosphaeria maculans) on winter oilseed rape (canola, Brassica napus) was assessed in two experiments at Rothamsted in successive years (2003–04 and 2004–05 growing seasons). Both experiments compared oilseed rape cultivars Eurol, Darmor, Canberra and Lipton, which differ in their resistance to L. maculans. Data were analysed to describe disease development in terms of increasing numbers of leaves affected over thermal time from sowing. The cultivars showed similar patterns of leaf spot development in the 2003–04 experiment when inoculum concentration was relatively low (up to 133 ascospores m−3 air), Darmor developing 5.3 diseased leaves per plant by 5 May 2004, Canberra 6.6, Eurol 6.8 and Lipton 7.5. Inoculum concentration was up to sevenfold greater in 2004–05, with Eurol and Darmor developing 2.4 diseased leaves per plant by 16 February 2005, whereas Lipton and Canberra developed 2.8 and 3.0 diseased leaves, respectively. Based on three defined periods of crop development, a piece-wise linear statistical model was applied to the progress of the leaf spot disease (cumulative diseased leaves) in relation to appearance (‘birth’) and death of leaves for individual plants of each cultivar. Estimates of the thermal time from sowing until appearance of the first leaf or death of the first leaf, the rate of increase in number of diseased leaves and the area under the disease progress line (AUDPL) for the first time period were made. In 2004–05, Canberra (1025 leaves ×°C days) and Lipton (879) had greater AUDPL values than Eurol (427) and Darmor (598). For Darmor and Lipton, the severity of leaf spotting could be related to the severity of stem canker at harvest. Eurol had less leaf spotting but severe stem canker, whereas Canberra had more leaf spotting but less severe canker. 相似文献
4.
The luminescent properties and crystal structure of Sr(1.5‐x)‐(1.5y)Mg0.5SiO4:xEu2+,yCe3+ blue phosphor synthesized by co‐precipitation method
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In order to improve the luminescent performance of silicate blue phosphors, Sr(1.5‐x)‐(1.5y)Mg0.5SiO4:xEu2+,yCe3+ phosphors were synthesized using one‐step calcination of a precursor prepared by chemical co‐precipitation. The crystal structure and luminescent properties of the phosphors were analyzed using X‐ray diffraction and fluorescence spectrophotometry, respectively. Because the activated ions (Eu2+) can occupy two different types of sites (Sr1 and Sr2), the emission spectrum of Eu2+ excited at 350 nm contains two single bands (EM1 and EM2) in the wavelength range 400–550 nm, centered at 463 nm, and the emission intensity first increases and then decreases with increasing concentrations of Eu2+ ions. Co‐doping of Ce3+ ions can greatly enhance the emission intensity of Eu2+ by transferring its excitation energy to Eu2+. Because of concentration quenching, a higher substitution concentration of Ce3+ can lead to a decrease in the intensity. Meanwhile, the quantum efficiency of the phosphor is improved after doping with Ce3+, and a blue shift phenomenon is observed in the CIE chromaticity diagram. The results indicate that Sr(1.5‐x)‐(1.5y)Mg0.5SiO4:xEu2+,yCe3+ can be used as a potential new blue phosphor for white light‐emitting diodes. 相似文献
5.
Epidemiology of Leptosphaeria maculans in relation to forecasting stem canker severity on winter oilseed rape in the UK 总被引:2,自引:0,他引:2
J. S. WEST J. E. BIDDULPH B. D. L. FITT P. GLADDERS 《The Annals of applied biology》1999,135(2):535-546
In the UK, ascospores of Leptosphaeria maculans first infect leaves of oilseed rape in the autumn to cause phoma leaf spots, from which the fungus can grow to cause stem cankers in the spring. Yield losses due to early senescence and lodging result if the stem cankers become severe before harvest. The risk of severe stem canker epidemics needs to be forecast in the autumn when the pathogen is still in the leaves, since early infections cause the greatest yield losses and fungicides have limited curative activity. Currently, the most effective way to forecast severe stem canker is to monitor the onset of phoma leaf spotting in winter oilseed rape crops, although this does not allow much time in which to apply a fungicide. Early warnings of risks of severe stem canker epidemics could be provided at the beginning of the season through regional forecasts based on disease survey and weather data, with options for input of crop-specific information and for updating forecasts during the winter. The accuracy of such forecasts could be improved by including factors relating to the maturation of ascospores in pseudothecia, the release of ascospores and the occurrence of infection conditions, as they affect the onset, intensity and duration of the phoma leaf spotting phase. Accurate forecasting of severe stem canker epidemics can improve disease control and optimise fungicide use. 相似文献
6.
Stem and leaf photosynthesis were measured in Glycine max var. essex (soybean) and Sparteum junceum (Spanish broom). The significance of stem photosynthesis to whole plant growth was evaluated by blocking stem photosynthesis with black straw sections. The growth of S. junceum was reduced by 18% when black straws were used in comparison to clear straws. The whole plant growth of G. max was not influenced by blocking the stem carbon contribution. Mean midday leaf photosynthesis was 12 μmol CO2 m–2 s–1 and 17 μmol CO2 m–2 s–1 for G. max and 5. junceum, respectively. Mean midday stem photosynthesis of S. junceum was 6.5 μmol CO2 m–2 s–1; however, positive net photosynthesis did not occur in G. max stems. Water stress caused a proportionally greater decrease in leaf photosynthesis compared to that of stems during diurnal cycles of photosynthesis in S. junceum. As a result the contribution to canopy carbon gain by stem photosynthesis increased from 38% to 48% of the total plant carbon gain under reduced water availability. 相似文献
7.
A promising RVO4:Eu3+,Li+@SiO2 (R = Gd,Y and Gd/Y) red‐emitting phosphor with improved luminescence (cd/m2) and colour purity for optical display applications
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Urlagaddala Rambabu Nagegownivari Ramachandra Munirathnam Busireddy Sudhakar Reddy Sandip Chatterjee 《Luminescence》2016,31(1):141-151
Red emission intensity was optimized in three stages, by investigating the effects of: (i) host composition (Gd, Y and Gd/Y), (ii) codoping Li+ as a sensitizer and, finally, (iii) with a SiO2 shell coating as a protecting layer. Lanthanide vanadate powder phosphors were synthesized using a modified colloidal precipitation technique. The effects of SiO2 coating on phosphor particles were characterized using scanning electron microscopy (SEM)‐EDAX, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and photoluminescence (PL) measurements. An improvement in the PL intensity on Li codoping was due to improved crystallinity, which led to higher oscillating strengths for the optical transitions, and also a lowering of the inversion symmetry of Eu3+ ions. Red emission intensity due to 5D0 → 5D2 transition of the phosphor Y0.94VO4:Eu3+0.05,Li+0.01 was enhanced by 22.28% compared with Y0.95VO4:Eu3+0.05, and was further improved by 58.73% with SiO2 coating. The luminescence intensity (I) and colour coordinates (x, y) of the optimized phosphor Y0.94VO4:Eu3+0.05,Li+0.01@SiO2, where I = 13.07 cd/m2 and (x = 0.6721, y = 0.3240), were compared with values for a commercial red phosphor (Y2O2S:Eu3+), where I = 27 cd/m2 and (x = 0.6522, y = 0.3437). The measured colour coordinates are superior to those of the commercial red phosphor, and moreover, match well with standard NTSC values (x = 0.67, y = 0.33). Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
8.
Xin‐Yuan Sun Wen‐Feng Wang Shou‐Qiang Sun Liang‐Wu Lin De‐Yi Li Ling‐Ping Zhou 《Luminescence》2013,28(3):384-391
BaGd2‐xO4:xEu3+ and Ba1‐yGd1.79‐2yEu0.21Na3yO4 phosphors were synthesized at 1300°C in air by conventional solid‐state reaction method. Phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra and thermoluminescence (TL) spectra. Optimal PL intensity for BaGd2‐xO4:xEu3+ and Ba1‐yGd1.79‐2yEu0.21Na3yO4 phosphors at 276 nm excitation were found to be x = 0.24 and y = 0.125, respectively. The PL intensity of Eu3+ emission could only be enhanced by 1.3 times with incorporation of Na+ into the BaGd2O4 host. Enhanced luminescence was attributed to the flux effect of Na+ ions. However, when BaGd2O4:Eu3+ phosphors were codoped with Na+ ions, the induced defects confirmed by TL spectra impaired the emission intensity of Eu3+ ions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
9.
A series of sequential polypeptides (LysiRj)n (R is Leu, Ser, or Gly) and random copolypeptides, (Lysx, Leuy)n, were synthesized. Their conformation in NaDodSO4 solution was determined by CD. Only (Lys-Leu)n, (Lys-Ser)n, and (Lys3-Ser)n adopt a stable β-form in the surfactant solution; (Lys-Ser2)n, (Lys-Ser3)n, (Lys2-Ser2)n, and (Lys2-Ser)n have an unstable β-form, which reverts to an unordered form in high NaDodSO4 concentrations, even though both Ser and DodSO-bound Lys+ are β-formers. In contrast, (Lys-Gly)n remains unordered in NaDodSO4 solution. On the other hand, Lys-rich (Lys2-Leu)n forms an unstable helix and (Lys2-Leu2)n a stable helix in NaDodSO4 solution. In 25 mM NaDodSO4 (Lysx, Leuy)n also forms a helix up to x = 75 and reverts to the β-form at x = 90. This compares with the helical conformation of (Lysx, Alay)n up to x = 65 and its β-form at x = 90, suggesting that Leu is an even stronger helix-former than Ala. Our results may provide a plausible explanation for the increase in helicity and disruption of the β-form for many proteins in NaDodSO4 solution, that is, the polypeptide chain of a protein usually favors a helical conformation over a β-form in the presence of excess surfactant. 相似文献
10.
11.
Dr Wayne R. Leifert Amanda L. Aloia Olgatina Bucco Edward J. McMurchie 《Molecular membrane biology》2013,30(6):507-517
G-protein coupled receptors (GPCRs) form a ternary complex of agonist, receptor and G-proteins during primary signal transduction at the cell membrane. Downstream signalling is thought to be preceded by the process of dissociation of Gα and Gβγ subunits, thus exposing new surfaces to interact with downstream effectors. We demonstrate here for the first time, the dissociation of heterotrimeric G-protein subunits (i.e., Gα and Gβγ) following agonist-induced GPCR (α2A-adrenergic receptor; α2A-AR) activation in a cell-free assay system. α2A-AR membranes were reconstituted with the G-proteins (±hexahistidine-tagged) Gαi1 and Gβ1γ2 and functional signalling was determined following activation of the reconstituted receptor:G-protein complex with the potent agonist UK-14304, and [35S]GTPγS. In the presence of Ni2+-coated agarose beads, the activated his-tagged Gαi1his-[35S]GTPγS complex was captured on the Ni2+-presenting surface. When his-tagged Gβ1γ2 (Gβ1γ2his) was used with Gαi1, the [35S]GTPγS-bound Gαi1 was not present on the Ni2+-coated beads, but rather, it was separated from the β1γ2(his)-beads, demonstrating receptor-induced dissociation of Gα and Gβγ subunits. Treatment of the reconstituted α2A-AR membranes containing Gβ1γ2his:Gαi1 with imidazole confirmed the specificity for the Ni2+:G-protein surface dissociation of Gαi1 from Gβ1γ2his. These data demonstrate for the first time, the complete dissociation of the G-protein subunits and extend observations on the role of G-proteins in the assembly and disassembly of the ternary complex in the primary events of GPCR signalling. 相似文献
12.
This paper theoretically analyses the relationship between surplus energy, which is available for either somatic growth or reproduction, and body weight. From the data of metabolism and growth of the biwamasu, Oncorhynchus rhodurus, obtained by Miura et al., a Bernoulli's differential equation is induced to represent the relationship between body weight and the sum of surplus energy and active metabolic rate. Solving this equation gives the amount of surplus energy, f(Wx), as follows:f(Wx) = (αWx1−γ+β1−γ)1/(1−γ)−Wx, in which α, β and γ are constants and Wx is body weight at age x. The function is applied to ten fish populations and consequently it is found to be useful for a wider age range and a wider variety of fishes than the conventional function. 相似文献
13.
M. R. Witt S. E. Westh-Hansen P. Baad Rasmussen S. Hastrup M. Nielsen 《Journal of neurochemistry》1996,67(5):2141-2145
Abstract: It has been shown previously that unsaturated free fatty acids (FFAs) strongly enhance the binding of agonist benzodiazepine receptor ligands and GABAA receptor ligands in the CNS in vitro. To investigate the selectivity of this effect, recombinant human GABAA/benzodiazepine receptor complexes formed by different subunit compositions (αxβyγ2, x = 1, 2, 3, and 5; y = 1, 2, and 3) were expressed using the baculovirus-transfected Sf9 insect cell system. At 10?4M, unsaturated FFAs, particularly arachidonic (20:4) and docosahexaenoic (22:6) acids, strongly stimulated (>200% of control values) the binding of [3H]flunitrazepam ([3H]FNM) to the α3β2γ2 receptor combination in whole cell preparations. No effect or small increases in levels of unsaturated FFAs on [3H]FNM binding to α1βxγ2 and α2βxγ2 receptor combinations were observed, and weak effects (130% of control values) were detected using the α5β2γ2 receptor combination. The saturated FFAs, stearic and palmitic acids, were without effect on [3H]FNM binding to any combination of receptor complexes. The hydroxylated unsaturated FFAs, ricinoleic and ricinelaidic acids, were shown to decrease the binding of [3H]FNM only if an α1β2γ2 receptor combination was used. Given the heterogeneity of the GABAA/benzodiazepine receptor subunit distribution in the CNS, the effects of FFAs on the benzodiazepine receptor can be assumed to vary at both cellular and regional levels. 相似文献
14.
《Archives of animal nutrition》2013,67(3):235-239
Auf der Grundlage einer Analyse von Energieumsatzmessungen an ausgewachsenen Rindern (Ochsen) bei Verfütterung von 110 Rationen sehr heterogener Nährstoffzusammensetzung werden folgende Vorhersagegleichungen für Brutto‐ (y1), verdauliche (y2) und umsetzbare Energie (y3) sowie für die Energieansatzwirkung von Rationen (y) (kJ) mitgeteilt: y1 ‐ 23.6z1 + 34.0z2 + 17.3z3 + 16,0z4 + 19, 1z5 y2 = 23.6x1 + 34.0x2 + 17.3x3 + 16.0x4 + 18.0x5 y3‐ 17.3x1 + 34.0x2+15.9x3+ 15.1x4+15.4x5 y = (6.5x1 + 26.6x2 + 10.1x3 + 7.5x4 + 8.9xs)( ‐ 0.5574 + 0.04050x6 ‐ 0,0002633x6 2) z1 = Rohprotein(g) x, ‐ verdl. Rohprotein(g) z2 ‐ Rohfett(g) x2 = verdl. Rohfett(g) z3 ‐ Stärke(g) x3 = verdl. Stärke(g) z4 ‐ Zucker(g) x4 = verdl. Zucker(g) z5 ‐ N‐freie Reststoffe(g) x5 = verdl. N‐freie Reststoffe(g) x6 ‐ Verdaulichkeit der Energie der Ration(%) (x6 ≤ 77) 相似文献
15.
The effect of water depth on bacterial biomass and their ability to synthesise DNA, by measuring their rate of [3H]-thymidine incorporation, was investigated in the northeast Atlantic at three sites of varying water depth (1100–3580 m) and sediment characteristics. Thymidine incorporation rates (y) in surficial sediments varied between 0.028 and 1.44 pmol h–1 g–1 and showed an exponential relationship with depth (x) according to the equation y= 2.05e–0.0011x (r=0.9830 for n=7, P<0.001). However, this relationship failed when a layer of phytodetritus was found overlying the surface sediment and [3H]-thymidine incorporation rates increased by 80–339%. In contrast, bacterial numbers varied between 1.09 and 11.96 × 108 cells g–1 (dry weight) and showed no significant relationships with water depth or sediment POC/TN content. Significant exponential relationships were also found between water depth (x) and the POC (y
1) and total nitrogen (TN, y
2) content of surficial sediments according to the following equations: where y
1 = 719e–0.0003x (r=0.8700 for n=9, P<0.01) and y
2 = 76e–0.0002x(r=0.7582 for n=9 P<0.02). These relationships were irrespective of the presence or absence of an overlying layer of phytodetritus. This suggests that the POC and TN content of these surficial deep sea sediments is directly related to the flux of material through the water column, which significantly impacts bacterial production. 相似文献
16.
Sr2ZnWO6:Eu3+,Bi3+,Li+: a potential white‐emitting phosphor for near‐ultraviolet white light‐emitting diodes
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Yuanyuan Ma Weiguang Ran Weina Li Chunyan Ren Haiyan Jiang Jinsheng Shi 《Luminescence》2016,31(3):665-670
A series of Sr2ZnWO6 phosphors co‐doped with Eu3+, Bi3+ and Li+ were prepared using the Pechini method. The samples were tested using X‐ray diffraction and luminescence spectroscopy. The results show that the samples can be effectively excited by near‐ultraviolet (UV) and UV light. The introduction of Bi3+ and Li+ significantly enhances the fluorescence emission of Sr2ZnWO6:Eu3+ and changes the light emitted by the phosphors from bluish‐green to white. When excited at 371 nm, Sr2–x–zZn1–yWO6:xEu3+,yBi3+,zLi+ (x = 0.05, y = 0.05, z = 0.05, 0.1 and 0.15) samples emit high‐performance white light. Intense red–orange emission is also observed when excited by UV light. The obtained phosphor is a potential white‐emitting phosphor that could meet the needs of excitation sources with near‐UV chips. In addition, this phosphor might have promising application as a red–orange emitting phosphor for white light‐emitting diodes based on UV light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
17.
Luminescence enhancement of (Sr1–xMx)2SiO4:Eu2+ phosphors with M (Ca2+/Zn2+) partial substitution for white light‐emitting diodes
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Eu2+‐doped Sr2SiO4 phosphor with Ca2+/Zn2+ substitution, (Sr1–xMx)2SiO4:Eu2+ (M = Ca, Zn), was prepared using a high‐temperature solid‐state reaction method. The structure and luminescence properties of Ca2+/Zn2+ partially substituted Sr2SiO4:Eu2+ phosphors were investigated in detail. With Ca2+ or Zn2+ added to the silicate host, the crystal phase could be transformed between the α‐form and the β‐form of the Sr2SiO4 structure. Under UV excitation at 367 nm, all samples exhibit a broad band emission from 420 to 680 nm due to the 4f65d1 → 4f7 transition of Eu2+ ions. The broad emission band consists of two peaks at 482 and 547 nm, which correspond to Eu2+ ions occupying the ten‐fold oxygen‐coordinated Sr.(I) site and the nine‐fold oxygen‐coordinated Sr.(II) site, respectively. The luminescence properties, including the intensity and lifetime of Sr2SiO4:Eu2+ phosphors, improved remarkably on Ca2+/Zn2+ addition, and promote its application in white light‐emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
A series of single‐phase full‐color emitting Li2Sr1−x−ySiO4:xDy3+,yEu3+ phosphors were synthesized by solid‐state reaction and characterized by X‐ray diffraction and photoluminescence analyses. The samples showed emission peaks at 488 nm (blue), 572 nm (yellow), 592 nm (orange) and 617 nm (red) under 393 nm excitation. The photoluminescence excitation spectra, comprising the Eu–O charge transfer band and 4f–4f transition bands of Dy3+ and Eu3+, range from 200 to 500 nm. The Commission Internationale de I'Eclairage chromaticity coordinates for Li2Sr0.98−xSiO4:0.02Dy3+,xEu3+ phosphors were simulated. By manipulating Eu3+ and Dy3+ concentrations, the color points of Li2Sr1−x−ySiO4:xDy3+,yEu3+ were tuned from the greenish‐white region to white light and eventually to reddish‐white region, demonstrating that a tunable white light can be obtained by Li2Sr1−x−ySiO4:xDy3+,yEu3+ phosphors. Li2Sr0.98−xSiO4:0.02Dy3+, xEu3+ can serve as a white‐light‐emitting phosphor for phosphor‐converted light‐emitting diode. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
19.
For the model y = α + βx + ? (model I) of linear regression we dealt with in KUHNERT and HORN (1980) the determination of a confidence interval for that x0 where the expectation Ey reaches a given value y0. Here we start with realizations of random variables y (i = 1,…, m) being independent of x which are given in addition to the realizations of-y. Now y0 denotes the unknown value of \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sum \limits_{i = 1}^m $\end{document} ciEy and x0 the x-value where the expectation Ey reaches that value y0. For this x0 we give a confidence interval. Applications stem from dose response assays. 相似文献
20.
Quantitative resistance against Leptosphaeria maculans in Brassica napus is difficult to assess in young plants due to the long period of symptomless growth of the pathogen from the appearance of leaf lesions to the appearance of canker symptoms on the stem. By using doubled haploid (DH) lines A30 (susceptible) and C119 (with quantitative resistance), quantitative resistance against L. maculans was assessed in young plants in controlled environments at two stages: stage 1, growth of the pathogen along leaf veins/petioles towards the stem by leaf lamina inoculation; stage 2, growth in stem tissues to produce stem canker symptoms by leaf petiole inoculation. Two types of inoculum (ascospores; conidia) and three assessment methods (extent of visible necrosis; symptomless pathogen growth visualised using the GFP reporter gene; amount of pathogen DNA quantified by PCR) were used. In stage 1 assessments, significant differences were observed between lines A30 and C119 in area of leaf lesions, distance grown along veins/petioles assessed by visible necrosis or by viewing GFP and amount of L. maculans DNA in leaf petioles. In stage 2 assessments, significant differences were observed between lines A30 and C119 in severity of stem canker and amount of L. maculans DNA in stem tissues. GFP-labelled L. maculans spread more quickly from the stem cortex to the stem pith in A30 than in C119. Stem canker symptoms were produced more rapidly by using ascospore inoculum than by using conidial inoculum. These results suggest that quantitative resistance against L. maculans in B. napus can be assessed in young plants in controlled conditions. Development of methods to phenotype quantitative resistance against plant pathogens in young plants in controlled environments will help identification of stable quantitative resistance for control of crop diseases. 相似文献