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Root rot symptoms were observed in fields of alfalfa in Chifeng city, Inner Mongolia, China in 2016. Disease incidences of seven alfalfa varieties planted in 2014 ranged from 56% to 95%, while incidence of Gongnong No. 1 planted in 2016 was 8%, 31% and 76% in 2016, 2017 and 2018, respectively. Paraphoma isolates were consistently recovered from black necrotic root tissues of diseased plants with a frequency of 77.1%. Based on morphological characters and phylogenetic analysis of rDNA internal transcribed spacer (ITS), elongation factor 1-α (EF1-α) and β-tubulin (TUB), this fungus was identified as Paraphoma radicina. Glasshouse pathogenicity experiments showed that P. radicina significantly reduced above- and below-ground biomass of alfalfa plants 2 months after inoculation. Paraphoma radicina infected 70% of the plants inoculated with a root dip in conidia, and these symptoms were consistent with the symptoms in the field. Paraphoma radicina was successfully reisolated from disease roots of the inoculated alfalfa plants. This is the first report of P. radicina as the causal agent of alfalfa root rot in China. 相似文献
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以西番莲品种‘台农1号’为实验材料,通过电镜扫描技术比较观测TeMV和PWV侵染与健康西番莲的叶片、幼嫩果实外果皮组织形态结构,分析测定其叶片生理生化变化,研究西番莲病毒侵染对西番莲叶片和幼嫩果实外果皮组织结构和生理生化的影响。结果表明：TeMV与PWV侵染后,西番莲植株叶片的海绵组织细胞间隙缩小,发生成团堆积状排列,栅栏组织细胞萎缩,呈不规则长条形;幼嫩果实外表皮组织中石细胞层发生严重断裂,排列松散,海绵层细胞变得松散,且发生较严重的木质化现象;叶片与幼嫩果实外表皮表面纹理粗糙、褶皱,气孔保卫细胞萎缩,气孔周围组织皱缩、粗燥;感病果实外果皮表面上的腺毛凸起无序。病毒侵染后,感病植株第1～3叶的蔗糖含量较第4～6叶的高23.11%;健康叶片则相对平衡,降低了淀粉积累、PG酶、纤维素酶与PPO酶活性,提高了感病植株第1～3叶的α-淀粉酶、GS酶与POD酶活性。西番莲受TeMV与PWV侵染后,植株叶片第1～6叶营养物质分配不平衡,相关物质的合成分解与抗氧化防御酶系统受伤害,叶片与果实组织形态结构受到不同程度的损坏,植株正常吸收功能遭到破坏。 相似文献
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Danuta Chołuj Ewa B. Moliszewska 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(1):59-70
Alterations in some physiological processes in source leaves of sugar beet—such as chlorophyll and carbohydrate concentrations,
stomatal conductance, rate of net photosynthesis and transpiration, and activity of the photosynthetic apparatus during root
interaction with Aphanomyces cochlioides, were investigated. The influence of time of infection on plant health, yield quality and quantity was also examined. Plants
were infected at different times of their growth period: on the sowing day and 4 or 8 weeks after sowing. A variation treatment,
with non-pelleted seeds infected on the sowing day, was also analyzed. The experiment showed that development of disease symptoms
depends on the time of infection and seed protection. A significant root yield decrease was observed in case of late infection,
as compared to the yield of plants infected on the sowing day. The fresh weight of leaves was significantly increased where
there was late infection. The infected plants showed a lower content of K+, Na+ and α-amino-N than did the controls. Infection by A. cochlioides induced chlorophyll degradation mostly in older leaves with the occurrence of natural senescence processes. Chlorophyll fluorescence
parameters indicated that the photosynthetic apparatus of younger leaves was more sensitive to pathogen infection, when compared
to older ones. The photochemical efficiency of photosystem II was reduced in young leaves mainly due to disturbance of the
water-splitting system. In plants grown from non-pelleted seeds a strong impairment of PSII was observed only in those leaves
which developed during early pathogen infection. In young leaves of plants infected in the fourth week after sowing, inhibition
of the rate of net photosynthesis was correlated with the increase in intercellular CO2 concentration, indicating some disturbance in the carbon assimilation phase. In mature leaves of late infected plants the
reduction of photosynthesis net rate was associated with a decrease of stomatal conductance and an increase of diffusion resistance
to CO2 and H2O, which was also the cause of the transpiration rate inhibition. When the leaves developed during early infection, an increase
of specific leaf weight and accumulation of carbohydrates was observed. In mature leaves of non-protected plants infected
on the sowing day, the recovery of all physiological processes was observed together with a diminution of disease symptoms. 相似文献
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Xiaomei Guo Henrik U. Stotz 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(1):7-19
Oxalic acid is an essential virulence factor of Sclerotinia sclerotiorum that elicits wilting symptoms in infected host plants. Foliar wilting in response to oxalic acid is known to be dependent
on an increase in stomatal conductance. To determine whether stomatal regulation controls susceptibility to S. sclerotiorum, abscisic acid-insensitive and open stomata mutants of Arabidopsis thaliana were analyzed. Whereas abscisic acid-insensitive mutants were hypersusceptible to S. sclerotiorum, open stomata mutants were as susceptible as wild type. It was concluded that stomatal regulation does not control susceptibility
to S. sclerotiorum because open stomata mutants are known to only impair guard cells whereas abscisic acid-insensitive mutants also affect other
cell types. Guard cell-independent processes also control sensitivity to oxalic acid because oxalic acid was more toxic to
abscisic acid-insensitive mutants than to open stomata mutants. To explore a possible mechanism of toxicity, production of
reactive oxygen species was measured in plant cells after exposure to oxalic acid. Oxalic acid was found to elicit reactive
oxygen species production independently of abscisic acid. Nevertheless, cancellation of reactive oxygen species elicitation
after co-stimulation of wild-type guard cells with oxalic acid and abscisic acid provided evidence for antagonistic interaction
between both molecules. 相似文献
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Buthidazole (3-[5-(1,1-dimethylethyl)-1,3.4-thiadiazol-2-yl]-4-hydroxy-l-methyl-2-imidazolidinone) at concentrations of 10?6-10?4M did not affect germination of corn (Zea mays L.,‘Pioneer 3780’), redroot pigweed (Amaranlhus retroflexus L.), alfalfa (Medicago saliva L., ‘Vernal’), and quackgrass (Agropyron repens(L.) Beauv.) seeds. Stressing the seeds obtained from mature corn plants treated either pre-emergence or pre- plant incorporated with buthidazole at several rates by accelerated ageing and cold treatments further indicated that this herbicide did not affect germination. Total photosynthesis and dark respiration of corn plants 12 days after pre-emergence application and of redroot pigweed, alfalfa, and quackgrass plants after postemergence application of buthidazole at several rates were measured with an infrared CO2 analyser. The results suggested that buthidazole was a rapid inhibitor of photosynthesis of the sensitive redroot pigweed and quackgrass plants, with less effect on corn and alfalfa. Buthidazole did not affect respiration of the examined species except for a transitory increase in corn and alfalfa 12 days after pre-emergence or 4 h after postemergence treatment with buthidazole at 0.56 or 1.12 and 2.24 kg/ha, respectively. A long-term inhibition of quackgrass respiration 96 h after treatment with buthidazole at 1.12 and 224 kg/ha was also evident. 相似文献
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Vladimír Šašek Miroslava Nováková Petre I. Dobrev Olga Valentová Lenka Burketová 《European journal of plant pathology / European Foundation for Plant Pathology》2012,133(1):279-289
Resistance to infection in plants can be induced by treatment with various chemicals. One such compound is β-aminobutyric
acid (BABA). Its positive effect on disease resistance has been noted in several pathosystems. Here we demonstrate that treatment
with BABA protects Brassica napus plants from infection by the fungal pathogen Leptosphaeria maculans. Surprisingly, BABA also displayes in vitro antifungal activity against L. maculans with EC50 similar to the fungicide tebuconazole. Both spore germination and hyphal growth were affected. The toxic effect can be reverted
by addition of trypton to the culture medium. We hypothesised that BABA might inhibit inorganic nitrogen assimilation. Suppression
of disease progression in plants and antifungal activity in vitro was weaker for α-aminobutyric acid and negligible for γ-aminobutyric
acid. In contrast to a resistance inducer benzothiadiazole, the effect of BABA on disease development was nearly independent
of the timing of treatment, indicating possible antifungal activity in planta. On the other hand, quantification of multiple hormones and an expression analysis have shown that treatment with BABA induces
a synthesis of salicylic acid (SA) and expression of SA marker gene PR-1, but no evidence was observed for priming of SA responses to L. maculans. While we have not conclusively demonstrated how BABA suppresses the disease progression, our results do indicate that antifungal
activity is another mechanism by which BABA can protect plants from infection. 相似文献
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Dan M. Weinthal Sara Yablonski Sima Singer Isaac Barash Shulamit Manulis-Sasson Victor Gaba 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(3):289-302
Pantoea agglomerans pvs. gypsophilae and betae are related gall-forming bacteria. While P. agglomerans pv. beta initiates gall formation on both beet and gypsophila, the gypsophila pathovar causes gall formation only on gypsophila. PthG
is a type III effector determining host range of these pathogens, initiating the hypersensitivity response in beet, but is
a virulence factor in gypsophila. The role of PthG and its mode of action in pathogenicity remain unclear. Transgenic Nicotiana tabacum plants expressing pthG were created. PthG over-expression was often lethal, and surviving pthG-bearing lines showed morphological and developmental abnormalities such as leaf deformation and abnormal vascular branching,
dwarf stature, loss of apical dominance, seedling apical meristem loss, rapid germination, reduced fertility, plants which
cease growth for several weeks later producing a new lateral shoot, and loss of endophyte resistance (bearing unusual saprophyte
populations). Some transformants required light for seed germination and showed rapid seedling greening. In in vitro assays
PthG expression modified responses to auxin and cytokinin, inhibiting root and shoot production but not callus formation.
In vitro differentiation responses to light were modified by PthG expression. This effector may interfere in the plant auxin
signalling pathways resulting in higher observed auxin and ethylene levels, and subsequent blockage of root and shoot development.
Apparently PthG tunes the host response to high hormone levels, changing the developmental response. Since shoot and root
development are delayed, we hypothesize that callus/gall formation is supported by this activity. However, interference by
PthG with hormone and light signalling does not explain all the responses observed in pthG-bearing lines. 相似文献
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Matthew P. Daugherty Joao R. S. Lopes Rodrigo P. P. Almeida 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(3):333-340
Differences in the virulence of a pathogen among host species can occur because hosts differ in their resistance or tolerance
to infection or because of underlying genetic variation in the pathogen. The xylem-limited bacterium Xylella fastidiosa is pathogenic to dozens of plant species throughout the Americas, and is structured into genetically and biologically distinct
strains. In some plants X. fastidiosa causes striking leaf scorch symptoms and in others, such as alfalfa, stunting is the primary symptom. The mechanism by which
these symptoms occur has been debated. We tested the hypothesis that symptoms result from X. fastidiosa-induced water stress, and that the magnitude of water stress is strain-dependent. We mechanically inoculated alfalfa plants
with one of 14 isolates (5 identified genetically as “almond” and 9 as “grape” isolates), and compared stable carbon isotope
ratios among isolates. Infected plants showed significant isotopic shifts (up to 2% on average) relative to healthy plants
that were consistent with water stress. Moreover, there were significant differences in water stress among isolates, with
a tendency for grape isolates to cause more severe water stress than almond isolates. There was also a positive relationship
between plant infection level and isotopic shift (slope ± SE = 0.273 ± 0.068), which supports the hypothesis that X. fastidiosa symptoms result from bacterial multiplication and vessel occlusion. Unexpectedly, however, water stress was not correlated
with measures of alfalfa stunting. These results suggest X. fastidiosa induces strain-specific levels of water stress, but factors other than water stress alone are responsible for stunting. 相似文献
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Effects of Verticillium dahliae on tomato root morphology considering plant growth response and defence 
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下载免费PDF全文 The soilborne pathogen Verticillium dahliae invades its host via the root, and spreads systemically throughout the plant. Although a functional root system of appropriate size is essential for water and nutrient uptake, to date, effects of pathogens on root morphology have not been frequently investigated. Therefore, this study aims to improve knowledge of how V. dahliae infection impairs root morphological characteristics of tomato, considering plant growth and physiological responses, particularly those involved in defence in roots and leaves over a growing period of up to 28 days post‐inoculation. Verticillium dahliae infection suppressed the growth of both shoot and root. Diseased plants developed a smaller leaf area, and exhibited a reduction in the rate of photosynthesis and stomatal conductance. An early response to pathogen invasion in the host root was the up‐regulation of several defence‐related genes, such as proteinase inhibitor II (Pin2), β‐1,3‐glucanase A (GluA) and two pathogenesis‐related genes (PR‐1a, PR‐1b). However, this response did not prevent colonization of the roots by the pathogen. Although a high variability in pathogen density was found within the root system, a significant increase of both the specific root length and surface area was observed in response to pathogen invasion; these traits correlated with water use efficiency. Morphological changes of the root may represent an adaptive response evolved to sustain the supply of both water and nutrients in the presence of the pathogen. 相似文献
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Sheau-Fang Hwang Heping Wang Bruce D. Gossen Kan-Fa Chang George D. Turnbull Ron J. Howard 《European journal of plant pathology / European Foundation for Plant Pathology》2006,115(4):389-399
Foliar pathogens attack alfalfa wherever the crop is grown, but their impact, especially on seed production, is poorly understood. In greenhouse trials, leaf spot injury caused by inoculation with various pathogens reduced the crude protein content of infected alfalfa leaves by 22% compared with a healthy control. There was a negative relationship between disease injury and the photosynthetic efficiency of alfalfa plants, as determined by measuring chlorophyll fluorescence in leaves from inoculated vs. non-inoculated seedlings. In field trials at two sites in Alberta from 2001 to 2003, inoculation with Phoma medicaginis increased disease incidence in four of six trials, Phoma sclerotioides increased incidence in four of five trials, and Leptosphaerulina
trifolii and Stemphylium
botryosum increased incidence in two of six trials. There was a trend for inoculation treatments to reduce seed yield, despite high levels of background infection by indigenous pathogens. The fungicides benomyl and propiconazole inhibited radial growth of Phoma spp. in vitro and reduced disease incidence in inoculated greenhouse experiments. In field trials, applications of benomyl and propiconazole reduced disease incidence, but did not always increase seed yield. 相似文献
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Shohei Matsuura Yosuke Matsushita Reiko Kozuka Sachiko Shimizu Shinya Tsuda 《European journal of plant pathology / European Foundation for Plant Pathology》2010,126(1):111-115
Quantitative PCR revealed that Tomato chlorotic dwarf viroid (TCDVd) was present in substantial amounts in viroid-infected tomato flowers. Healthy tomato plants were arranged in two
different glasshouses, and plants were mechanically inoculated with TCDVd. Bumblebees (Bombus ignitus) were then introduced into the glasshouses to reveal whether the viroid was transmitted from infected source plants to neighbouring
healthy plants. TCDVd infection was found in neighbouring tomato plants more than 1 month after the introduction of the bees,
some of which expressed symptoms, in both glasshouses. Thus, bumblebees transmitted TCDVd from tomato to tomato by pollination
activities. 相似文献
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为明确金龟子绿僵菌Metarhizium anisopliae在促进植物生长和提高植物抗性方面的作用,以金龟子绿僵菌拌土种植紫花苜蓿Medicago sativa,于室内测定植株的生长参数、苜蓿斑蚜Therioaphis trifolii的取食选择性及其发育历期和繁殖力。结果表明,金龟子绿僵菌处理后7 d,植株株高比对照显著增加了0.87 cm;处理后14 d,植株分枝数为3.88个,根长为54.67 mm,均显著高于对照。株龄14 d的植株接入苜蓿斑蚜,至株龄28 d时,金龟子绿僵菌处理的植株株高、分枝数和根长均较对照显著增加;同时生物量、叶绿素含量和类胡萝卜素含量也有不同程度的升高。选择性试验结果显示,24 h内选择并驻留在金龟子绿僵菌处理植株叶片上的苜蓿斑蚜数量较对照显著减少28.57%。以金龟子绿僵菌处理的植株叶片饲喂苜蓿斑蚜,1～4龄若虫的发育均有所减缓,各龄若虫的发育历期均较对照叶片饲喂的各龄若虫有所延长,而成虫寿命较以对照叶片饲喂时显著缩短了30.09%,总生命历期显著缩短了18.83%。表明金龟子绿僵菌促进了紫花苜蓿植株的生长,同时增强了植株对苜蓿斑蚜的耐害性、排趋性与... 相似文献
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大麦黄矮病毒(barley yellow dwarf viruses,BYDVs)引起的小麦黄矮病严重威胁我国麦类生产,造成严重经济损失。植物中的miRNA调控植物生长发育、信号转导及对外界压力的反应,通过调控植物抗性基因的表达影响植物与病原物的互作。本研究对感染BYDV-GAV 后3 d、7 d及健康对照的‘小偃6号'小麦样品进行miRNA测序,合并去冗余后分别得到99、96、95个已知的miRNA序列和806、809、1 024个新miRNA序列。对这些miRNA进行差异表达分析,BYDV-GAV侵染后3 d和7 d的小麦样品,与对照相比上调表达的miRNA数量分别为3个和7个,下调表达的为14个和12个。将差异表达的miRNA利用psRNATarget进行靶基因预测,共得到1 254个靶标基因。靶基因的KEGG和GO富集分析,进一步明确了其功能及作用通路。对14个病毒病症状相关的靶基因进行定量分析,结果表明随病毒侵染时间的延长,这些靶基因出现差异性表达,显示miRNA参与了寄主与病毒的互作。研究结果有助于揭示BYDV-GAV与寄主小麦的互作机理。 相似文献
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为探讨烟草脆裂病毒（tobacco rattle virus,TRV）载体介导的基因沉默技术对朱顶红褪绿环斑病毒（Hippeastrum chlorotic ringspot virus,HCRV）运动蛋白基因NSm的沉默效应,以本氏烟Nicotiana tabacum为材料,构建靶向HCRV NSm序列的基因沉默表达载体pTRV2-NSm,经农杆菌Agrobacterium介导侵染烟苗,检测其侵染效率,人工接种HCRV到沉默表达载体处理过的烟苗,通过观察发病症状、统计病情并应用实时荧光定量PCR(quantitative real-time PCR,qRT-PCR)技术检测TRV介导的基因沉默体系对HCRV侵染的沉默效应。结果表明,pTRV2-NSm沉默表达载体对本氏烟植株的侵染率达到95.00%,并且对本氏烟的生长无明显影响;与对照相比,经沉默载体处理的烟草植株接种HCRV后发病率显著降低,在接种后14 d发病率下降了90个百分点,病毒积累量明显下降,随着时间延长pTRV2-NSm对病毒的抑制效果持续升高,在接种后14 d对病毒病的防治效果最高,达93.13%;qRT-PCR检测发... 相似文献
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Morphophysiological response of young olive trees to verticillium wilt under different surface drip irrigation regimes 下载免费PDF全文
下载免费PDF全文 A. Santos‐Rufo J. J. Hidalgo J. C. Hidalgo V. Vega D. Rodríguez‐Jurado 《Plant pathology》2018,67(4):848-859
The effects of irrigation on verticillium wilt in olive, in terms of morphological, biomass and physiological parameters were evaluated on pot‐grown trees maintained in the field for 3 years. Plants inoculated and noninoculated with Verticillium dahliae were irrigated to high and low range of soil water content (HR and LR) at daily (DF; about 2 days/event), weekly (WF) and daily‐weekly (DWF) drip‐irrigation frequency. Morphological parameters, relative biomass and biomass water‐use efficiency were higher at LR than at HR (with few exceptions) and at DF than at other frequencies in noninoculated and inoculated plants, but the fungus reduced those parameters by 17.0–38.5%. Lower root weight ratio, relative biomass and shoot length as area originated at HR in noninoculated plants, could be favourable to the accumulation of root infections and the amount of fungus per tissue length in inoculated plants because higher infection was known at HR. Moreover, higher aerial biomass and length promoted by irrigation at DF could prevent the more severe expression of symptoms, which occurred at WF and DWF in the presence of Verticillium. Negative correlations were found between indicated parameters and disease. Lower water stress (SΨ), and higher stomatal conductance (gs) and net photosynthesis at DF in noninoculated plants could limit the disease by improving water status, as SΨ was increased by the fungus only at WF and DWF, and gs and disease were negatively correlated. LR‐DF treatment minimized the disease and kept the growth, water‐use efficiency and physiological parameters in inoculated plants to levels close to noninoculated plants. 相似文献
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大麦黄矮病毒(barley yellow dwarf viruses,BYDVs)引起的小麦黄矮病严重威胁我国麦类生产,造成严重经济损失。植物中的miRNA调控植物生长发育、信号转导及对外界压力的反应,通过调控植物抗性基因的表达影响植物与病原物的互作。本研究对感染BYDV-GAV 后3 d、7 d及健康对照的‘小偃6号'小麦样品进行miRNA测序,合并去冗余后分别得到99、96、95个已知的miRNA序列和806、809、1 024个新miRNA序列。对这些miRNA进行差异表达分析,BYDV-GAV侵染后3 d和7 d的小麦样品,与对照相比上调表达的miRNA数量分别为3个和7个,下调表达的为14个和12个。将差异表达的miRNA利用psRNATarget进行靶基因预测,共得到1 254个靶标基因。靶基因的KEGG和GO富集分析,进一步明确了其功能及作用通路。对14个病毒病症状相关的靶基因进行定量分析,结果表明随病毒侵染时间的延长,这些靶基因出现差异性表达,显示miRNA参与了寄主与病毒的互作。研究结果有助于揭示BYDV-GAV与寄主小麦的互作机理。 相似文献
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ABSTRACT Digestive cysteine proteinases have been isolated from plant-parasitic nematodes as well as coleopteran and hemipteran insects. Phytocystatins, inhibitors of cysteine proteinases, are found in a number of plants where they may play a role in defense against pathogens and pests. The cDNAs of the phytocystatins from rice, oryzacystatin I (OC-I) and oryzacystatin II (OC-II), were expressed in alfalfa (Medicago sativa) plants under the control of the potato protease inhibitor II (PinII) promoter and the plants were evaluated for resistance to the root-lesion nematode (Pratylenchus penetrans). A PinII-beta-glucuronidase (GUS) gene was introduced into alfalfa to determine the pattern of gene expression from this promoter. Constitutive GUS expression was observed in leaf and root vascular tissue, and in some plants, expression was observed in leaf mesophyll cells. Mechanical wounding of leaves increased GUS expression approximately twofold over 24 h. Inoculation with root-lesion nematodes resulted in localized GUS expression. Populations of root-lesion nematodes in alfalfa roots from one line containing the PinII::OC-I transgene and one line containing the PinII::OC-II transgene were reduced 29 and 32%, respectively, compared with a transgenic control line. These results suggest that oryzacystatins have the potential to confer increased resistance to the root-lesion nematode in alfalfa. 相似文献