Effect of Foliar Applied Plant Elicitors on Microbial and Nematode Populations in the Root Zone of Potato

Abstract

Systemic acquired resistance (SAR) is a process whereby a plant that successfully resists a pathogen becomes highly resistant to subsequent infection not only by the original pathogen but also by a wide variety of pathogens. Most SAR research has focused on resistance in leaves, so much less is known about the effectiveness of foliar applications of SAR compounds in the protection of plant roots and associated microorganisms in soil. This study was conducted to determine if foliar SAR‐inducing applications (BTH or harpin) negatively impact the potato root system beneficial rhizosphere microbial populations and activity or influence pathogenic nematode populations. Foliar applications of benzo (1,2,3) thiadiazole‐7‐carbothioic acid S‐methyl ester (BTH) and the microbial protein harpin applied in various combinations, timings, and rates showed no effects on microbial biomass, culturable bacteria, Pseudomonas populations, or N‐mineralization potentials over 2 years. No stimulatory or inhibitory effects on major bacterial populations were observed, indicating that SAR induction does not have a negative effect on general microbial populations or activities. BTH and harpin both reduced the numbers of lesion nematodes (Pratylenchus spp.) by potato harvest. BTH reduced root knot nematodes, Meloidogyne chitwoodi at the end of the season. In addition, BTH and high‐dose harpin (applied at the 4× rate) reduced the nematode infection index in comparison to the control. The SAR elicitors increased the population densities of nontarget free‐living nematodes in the soil compared to the control. Potato yields were not affected by plant elicitors but BTH and harpin both reduced the number of culled potatoes 26% compared to the control. Future studies are designed to determine if these plant elicitors have any direct effect on rhizosphere diversity or if plants with active defense pathways alter carbon flow and root exudates into the soil.     

基于ARSIS策略的SAR影像与多光谱遥感小波融合

针对南方多云多雨、光学遥感数据不易获取的特点,在江苏省宝应县设置了区域试验,探索了ENVISAT/SAR影像与HJ-1A星多光谱遥感融合的模式与效果。基于ARSIS策略,利用Mallat小波变换和波段间交互构造模型IBSM,对SAR影像和HJ-1A/CCD影像进行小波分解与低频、高频系数重构,然后通过小波逆变换得到信息融合影像。针对低频与高频影像的不同区域特征使用不同的融合规则,以增强融合过程的自适应性。对融合影像进行了主观与相应的定量评价,并与PCA变换、IHS变换等传统方法进行比较。最后,利用GPS矢量样点提取了小波融合前后影像的波段值与NDVI信息,对融合效果做了进一步的分析与说明。结果表明,小波融合、IHS变换、PCA变换影像光谱扭曲度平均值分别为0.1016、0.3261、1.2772,其中小波融合方法的值最小。三者的信息熵平均值分别为14.7015、11.8993和13.2293,以小波融合方法的值最高。说明小波融合方法在提高空间分别率的同时,较好的增强了光谱保持能力,信息解译效果明显优于PCA变换和IHS变换2种方法。     

灌溉水质与灌溉沟坡度对华北土壤径流和侵蚀的影响

Irrigation-induced soil erosion seriously affects the sustainability of irrigated agriculture. The effects of irrigation water quality and furrow gradient on runoff and soil loss were studied under simulated furrow irrigation in laboratory using a soil collected from an experimental station of China Agricultural University, North China. The experimental treatments were different combinations of irrigation water salt concentrations of 5, 10, 20, and 30 mmol_c L^-1, sodium adsorption ratios (SAR) of 0.5, 5.0, and 10.0 (mmol_c L^-1)^0.5, and furrow gradients of 1%, 3%, and 5%, with distilled water for irrigation at 3 furrow gradients as controls. The experimental data indicated that total runoff amount, sediment concentration in runoff, and total soil loss amount generally decreased with increasing salt concentration in irrigation water but increased with its sodicity and furrow gradient. The effects of water quality and furrow gradient on soil loss were greater than those on runoff, and the increase of furrow gradient decreased the influence of water quality on soil loss. When the salt concentration increased from 5 to 30 mmol_c L^-1 at SAR of 10.0 (mmol_c L^-1)^0.5, total runoff amount, sediment concentration, and total soil loss amount decreased by 3.89%, 52.1%, and 53.92%, and 10.57%, 38.86%, and 42.03% at the furrow gradients of 1% and 5%, respectively. However, they respectively increased by 3.37%, 45.34%, and 55.36%, and 3.86%, 10.77%, and 13.91% when SAR increased from 0.5 to 10.0 (mmol_c L^-1)^0.5 at the salt concentration of 5 mmol_c L^-1. Irrigation water quality and furrow gradient should be comprehensively considered in the planning and management of furrow irrigation practices to decrease soil loss and improve water utilization efficiency.     

Effect of water quality on exchange phase — solution phase behavior of three soils

The effect of total electrolyte concentration (TEC) and sodium adsorption ratio (SAR) of water on ESR‐SAR relationships of clay (Typic Haplustert), clay loam (Vertic Haplustept) and silt loam (Lithic Haplorthent) soils was studied in a laboratory experiment. Twenty four solutions, encompassing four TEC levels viz., 5, 10, 20, and 50 mmol_c l^—1 and six SAR levels viz., 2.5, 5, 10, 15, 20, and 30 mmol^1/2l^—1/2 were synthesized to equilibrate the soil samples using pure chloride salts of calcium, magnesium, and sodium at Mg:Ca = 1:2. SAR of equilibrium solution decreased as compared to the equilibrating solution and more so in waters of low salt concentration and high SAR. At low electrolyte concentration, high SAR values were not attained in the equilibrium solution because of addition of calcium and magnesium from the mineral dissolution and from the exchange phase. Irrespective of TEC, exchangeable sodium in all the soils increased by about 4.5 to 5‐fold and irrespective of SAR, it increased by about 1.4‐ to 1.8‐fold. A positive interaction of TEC and SAR influenced the ESP build‐up and CEC played a major role in the visual disparity in sodication of these soils. At higher TEC levels, considerable increase in ESP was observed when it was corrected for anion exclusion and more so in silt loam followed by clay loam and clay soils. The values for Gapons' constant were in the range 0.0110—0.0176, 0.0142—0.0246, and 0.0189—0.0344 mmol^—1/2l^1/2 in clay, clay loam, and silt loam soils, respectively. Increase in TEC from 5 to 50 mmol_c l^—1 resulted in 5.84, 8.33, and 9.77 % decrease in Gapons' constant of clay, clay loam, and silt loam soils, respectively. The soils exhibited differential affinity for Ca²⁺, Mg²⁺ or Na⁺ under different quality waters. Regression coefficients of ESR‐SAR relationship were lower for low TEC as compared with high TEC waters. The exchange equilibrium was strongly affected by TEC of the solution phase. Variation in soil pH was gradual with respect to TEC and SAR of equilibrating solution and no sharp change was observed. Soluble salt concentration was doubled upon equilibration with low salt waters at all SAR levels in all the soils. However, the salt concentration remained unchanged upon equilibration with high salt waters. Considering pH 8.5 a boundary between soil salinity and sodicity, ESP values attained at TEC 5 mmol_c l^—1 were 7.34, 8.02, and 14.32 for clay, clay loam, and silt loam soils, respectively.     

Leaching and reclamation of calcareous saline‐sodic soil by moderately saline and moderate‐SAR water using gypsum and calcium chloride

Lysimeter experiments were conducted with sandy‐clay‐loam soil to study the efficiency of two amendments in reclaiming saline‐sodic soil using moderately saline and SAR (sodium‐adsorption ratio) irrigation water. Gypsum obtained from industrial phosphate by‐products and reagent grade Ca chloride were applied to packed soil columns and irrigated with moderately saline (ECe = 2.16 dS m^–1), moderate‐SAR water (SAR = 4.8). Gypsum was mixed with soil prior to irrigation at application rates of 5, 10, 15, 20, 25, and 32 Mg ha^–1, and Ca chloride was dissolved directly in leaching water at application rates of 4.25, 8.5, 12.75, 17.0, and 21.25 Mg ha^–1, respectively. The highest application rate in both amendments resulted in 96% reduction of total Na in soil. The hydraulic conductivity (HC) of soils receiving gypsum increased in all treatments. The highest HC value of 6.8 mm h^–1 was obtained in the highest application rate (32 Mg ha^–1), whereas the lowest value of 5.2 mm h^–1 was observed with the control treatment. Both amendments were efficient in reducing soil salinity and sodicity (exchangeable‐sodium percentage, ESP); however, Ca chloride was more effective than gypsum as a reclaiming material. Exchangeable Na and soluble salts were reduced with gypsum application by 82% and 96%, and by 86% and 93% with Ca chloride application, respectively. Exchangeable Ca increased with increasing amendment rate. Results of this study revealed that sodium was removed during cation‐exchange reactions mostly when the SAR of effluent water was at maximum with subsequent passage of 3 to 4 pore volumes. Gypsum efficiently reduced soil ESP, soil EC, leaching water, and costs, therefore, an application rate of 20 Mg ha^–1 of gypsum with 3 to 4 pore volumes of leaching water is recommended for reclaiming the studied soil.     

新疆小拟南芥NPR1基因对植物系统获得性抗性的影响

旨在研究小拟南芥NPR1基因的第三内含子对基因表达的影响。克隆出带有第三内含子的小拟南芥NPR1基因,构建诱导型植物表达载体并对拟南芥进行农杆菌遗传转化,经5 mmol/L外源水杨酸12 h诱导,利用Real-time PCR技术检测拟南芥病程相关蛋白的表达量。结果显示野生型拟南芥的NPR1、PR-1、PR-2、PR-5表达量高于转基因拟南芥;相对于野生型拟南芥,转基因拟南芥中SOD、POD酶活显著降低,而CAT酶活增加未达到显著水平。结果表明转入含有第三内含子的Ap.NPR1基因,转基因植株系统获得性抗性途径受到抑制,植株抗病性降低,说明第三内含子使得系统获得性抗性途径的基因表达受到抑制。     

SAR与水稻广谱抗病基因工程研究进展

植物系统获得性抗性（SAR）是植物受到病原菌侵染而产物的防御反应植物广谱抗病性的理论基础.进行水稻广谱抗病基因工程育种的研究对水稻生产和环境保护具有重要的意义.本文简述了植物广谱抗病性的理论基础、植物系统获得性抗性（SAR）的基本概念和特点,以及在植物基因工程育种中所应用的一些广谱抗病基因的特点,并对水稻广谱抗病基因工程育种的研究进展进行了论述,最后对水稻广谱抗病基因基因工程育种进行了展望.     

柑橘SAR及其信号转导基因CsSABP2在黄龙病菌侵染中的响应特征

【背景】柑橘系统获得性抗性(systemic acquired resistance,SAR)在柑橘抗黄龙病(Huanglongbing,HLB)过程中起着重要作用。水杨酸(SA)和水杨酸甲酯(MeSA)信号互换是激活植物SAR的关键信号转导途径,但其在抗HLB危害中的作用依然不清楚。【目的】以柑橘HLB不同耐病品种为材料,研究柑橘SAR及其信号转导的关键酶基因CsSABP2(salicylic acid binding protein 2)在HLB病原菌‘Candidatus Liberibacter asiaticus’(CLas)侵染中的响应特征,了解柑橘SAR及CsSABP2响应CLas侵染的作用。【方法】从SAR Marker基因CsPR1、CsPR2、CsPR5表达、活性氧H₂O₂水平和淀粉含量变化等方面分析CLas侵染、外施SA和MeSA调控柑橘SAR的特征。进一步,基于易感HLB锦橙(Citrus sinensis)和耐HLB酸柚(C. grandis)感染CLas转录组测序比较分析,筛选和克隆响应CLas侵染的CsSABP2...     

大豆疫霉菌、水杨酸和创伤诱导的拟南芥蛋白质谱的比较研究

 【目的】系统获得抗性（system acquired resistance,SAR）是植物抵抗病原菌侵染的一种复杂机制,本研究旨在鉴定大豆疫霉菌（Phytophthora sojae）诱导的拟南芥系统获得抗性相关的蛋白质。【方法】利用双向电泳分离创伤、水杨酸（Salicylic acid,SA）和大豆疫霉菌诱导的拟南芥叶片的总蛋白,并对28个差异表达的蛋白点进行了MALDI-TOF质谱鉴定。【结果】这28个蛋白点的表达模式可分为3种类型：13个点的表达随着伤口、SA和 P.sojae的诱导而上调;11个点的表达随着伤口、SA和 P.sojae的诱导而下调;4个点在伤口和P.sojae处理中的表达行为与SA处理相反。这些蛋白质涉及了物质代谢酶、调节因子或分子伴侣、氧化还原酶、防御相关蛋白、蛋白激酶、叶绿体蛋白和功能未知蛋白等复杂的生物学功能。【结论】创伤、SA和P.sojae诱导的拟南芥系统获得抗性涉及的抗性组分有很大的重叠,在信号传导网络上也存在一定的交叉。蛋白质组分析为研究复杂的植物抗性机制提供了可行的技术手段。     

6-BA和保水剂对切花月季瓶插寿命的影响

初步探讨了6-BA和保水剂对月季切花的保鲜作用与生理生化基础,与对照(清水)相比,经10mg/L6-BA和10mg/L6-BA 0.3%保水剂处理的月季切花,花枝的保水能力提高,花枝硬挺,并延缓质膜相对透性的增加、蛋白质的降解及MDA的产生,从而延长月季切花的瓶插寿命(2~3d),但后者各项指标均优于前者,效果更佳。