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1.
Cultivars with introgressed natural resistance genes have been widely used for plant disease control, especially in the control of virus diseases, for which no effective chemical control agent is available. However, we often encounter virus mutants that break down or overcome the resistance. In this review, recent studies will be discussed with respect to breakdown of plant virus resistance.  相似文献   

2.
The 2326 nucleotides of the 3′-terminal region of Carnation vein mottle virus (CVMV) RNA, which included part of the nuclear inclusion b gene, the complete coat protein (CP) gene and the entire 3′-noncoding region (3′-NCR) were determined. The region encoding the CP gene is 843 nucleotides long and the deduced protein consists of 280 amino acids. A search of the EMBL and PIR databases showed that the amino acid sequence of CVMV CP most resembled that of Plum pox virus with a similarity of 67.9%. The 3′-NCR of CVMV RNA is 541 nucleotides long, second longest in the genus Potyvirus. These results indicate that CVMV is closely related to Plum pox virus but is a distinct species in the genus Potyvirus. Received 8 October 1999/ Accepted in revised form 9 January 2000  相似文献   

3.
Journal of Plant Diseases and Protection - Beet black scorch virus (BBSV) was surveyed in major sugar beet cultivation areas in Iran in 2008–2013 growing seasons. A total of 148 out of 308...  相似文献   

4.
A number of chemical and biological agents are known as inducers of systemic acquired resistance (SAR) to tobacco mosaic virus (TMV) in tobacco plants. In the present study, a local spray application of the non-protein amino acid DL-β-aminobutyric acid (BABA) was effective in enhancing resistance to TMV in tobacco plants containing the N gene. In contrast, the isomer α-aminobutyric acid (AABA) showed a much lower activity whereas γ-aminobutyric acid (GABA) was completely inactive, indicating a strong isomer specificity of aminobutyric acid in triggering enhanced virus resistance.Rapid cell death was detected in tobacco leaf tissues after foliar application of BABA, subsequently resulting in the development of macroscopically visible, necrotic lesions. BABA-induced cell death was associated with the rapid generation of superoxide and hydrogen peroxide. As further consequences, the occurrence of lipid peroxidation in treated tissues, a local and systemic increase of salicylic acid (SA) levels and the expression of PR-1a, a molecular marker of SAR in tobacco, could be observed. None of these responses was detectable after treatment with GABA.Enhancement of virus resistance by BABA was found to be strictly dependent on SA-mediated signal transduction since it could not be detected in salicylate hydroxylase (nahG) expressing transgenic tobacco plants. These findings suggest that in tobacco, primary processes triggered by foliar application of BABA, resemble those initiated by microbes during a hypersensitive response (HR) that result in SAR activation.  相似文献   

5.
Surveys of thrips and Tomato spotted wilt virus (TSWV) on weeds were conducted in the eastern Mediterranean region of Turkey during the years 2004–2006. Thrips species were collected by vigorously shaking weedy plants into a white container for 15 sec. Plant material collected during field surveys and plants which were used for mechanical inoculation of TSWV, were tested by DAS–ELISA. The weed species Ranunculus muricatus, Melilotus officinalis, Sinapis arvensis and Portulaca oleracea were used for the virus transmission experiments in an enclosed high plastic tunnel and in cage experiments. Western flower thrips, Frankliniella occidentlis (Pergande) (Thysanoptera: Thripidae), was the most common thrips, inhabiting 80 of the 82 weed species sampled. Adults of F. occidentalis and thrips larvae were significantly more abundant on S. arvensis than on the other weed species sampled (P<0.05). Adult and larval thrips showed peak densities on most weeds in April or May. Summer annual weeds were not good hosts for reproduction of the thrips. A total of 90 samples from 17 plant species belonging to 11 plant families were ELISA positive for TSWV. No TSWV was detected on 65 weed species belonging to 26 plant families. High numbers of plant samples infected by TSWV were obtained in P. oleracea (21 samples) and in R. muricatus (15 samples). In field surveys symptoms of TSWV were detected on only R. muricatus. Incidence of the TSWV on weeds ranged between 5% and 25%. Transmission rates of TSWV by F. occidentalis to the weeds ranged from 33% to 83% in the pepper plastic tunnel and cage experiments.  相似文献   

6.
Spread patterns of a Grapevine leafroll-associated virus 1 (GLRaV-1) epidemic and a mealybug infestation survey over 10 year were recorded in two Burgundy French vineyards to investigate the relation between them. The temporal evolution of leafroll spread at both study sites was compared on disease incidence data with logistic regression models. We first tested if the spatial distribution of the disease and the mealybug were aggregated using permutation methods, then we tested the independence between the two spatial patterns by randomly shifting one pattern. In Bonzon, an increase from 5 % to 86 % of leafroll prevalence was observed over an 8-year time span, whereas leafroll prevalence remained stable around 5 % in Marsannay-la-Côte during the same period. In Bonzon, the disease spread rapidly from older neighbouring vineyards in four main patches while no spread of the disease was recorded from infected vines in Marsannay-la-Côte. The mealybug Phenacoccus aceris was recorded on 74 % of vines in Bonzon throughout the study and only 6 % of vines in Marsannay-la-Côte. In the latter location, the disease was not associated with the presence of the mealybug, so that it may have arisen from infected plant material escaping the sanitary inspection. In Bonzon, the significant statistical correlation between the mealybug distribution and diseased plants suggests that P. aceris was responsible for the rapid spread of GLRaV-1 in the vineyard. This is the first report of GLRaV-1 natural spread in Europe.  相似文献   

7.
Many animals obtain reliable information about potential mates, including whether they are parasitised or not, mostly from olfactory cues in urine. Previous experiments with rodents have shown that females can detect parasites in males that are potentially transmissible during copulation, so that females can directly avoid infection by discriminating against parasitised males. Here, using choice tests, we examine whether female rats can distinguish males infected with the tapeworm Hymenolepis diminuta Rudolphi, 1819, a parasite with a complex life cycle and thus not directly transmissible among rats. Female rats tended to spend more time investigating the urine of non-parasitised males than that of parasitised males. The magnitude of the parasite burden in the infected males had no effect on the females' preference for the non-parasitised males. We also found that parasitised males had lover testosterone levels in their blood than non-parasitised males. These results suggest that females use cues in male urine reflecting either the presence of the parasite and/or lower testosterone levels to avoid parasitised males and possibly secure resistance genes for their offspring.  相似文献   

8.
Sixteen isolates of Chinese yam necrotic mosaic virus (ChYNMV) were collected from nine sites in Japan and one site in Korea, and 1098 nucleotides of the 3-terminal of the genome were sequenced. Identity of the coat protein gene was 95.5%–99.7% among the isolates. Substitution in the deduced amino acids of the coat protein ranged from 0 to 7, mainly in the N-terminal region. The 3-untranslated region consisted of 231 nucleotides, which had 96.5%–100% nucleotide identity among the isolates. Sequence diversity was considerably less in ChYNMV than in Yam mosaic virus or Japanese yam mosaic virus.  相似文献   

9.
When leaf-halves of Samsun NN tobacco or bean plants were floated on a solution of 10–15 M eosin Y after inoculation with tobacco mosaic virus (TMV) and kept at 20° C, local lesion formation was markedly diminished. There was also a decrease in the size of the lesions.Depending on the temperature very strong fluorescence due to callose formation was seen around the lesions in eosin Y-treated leaf-halves of Samsun NN tobacco and bean plants. It lasted from 3–5 days after inoculation, whereas fluorescence around lesions in the water-treated control leaves disappeared within 2–3 days after inoculation.When leaf discs of Samsun tobacco, a systemic host for TMV, were floated on a solution of eosin Y after inoculation with TMV and kept at 20°C for 5 days, TMV multiplication was not prevented. Callose deposition could be detected, neither in eosin Y-treated nor in water-treated control leaves.The relation between the inhibition of local lesion formation and the accumulation of callose in eosin Y-treated leaves is discussed.Samenvatting Het is bekend dat er een verband bestaat tussen afzetting van callose en de vorming van lokale lesies bij verschillende virus-waardplantcombinaties. Tevens staat vast dat eosine ophoping van callose op zeefplaten veroorzaakt. Onderzocht werd nu of eosine Y van invloed is op de vorming van lokale lesies en tevens ophoping van callose veroorzaakt in bladeren van Samsun NN-tabak en boon, geïnoculeerd met tabaksmozaïekvirus (TMV).Het bleek dat bladhelften van tabak die, na inoculatie met TMV, bij 20°C gedreven hadden op een oplossing van 10 of 15 M eosine Y, minder en kleinere lesies hadden dan de controlehelften die op water hadden gedreven (Tabel 1; Fig. 1). Bij 25°C werden deze effecten niet waargenomen (Fig. 2). Een concentratie van 15 M veroorzaakte wat beschadiging van de bladeren (verbruining van een deel van de zijnerven).Bij bladhelften van de boon was geen beschadiging te zien bij een concentratie van 15 M. Bij bonebladeren geïnoculeerd met TMV bleek behandeling met eosine Y zowel bij 20°C als bij 25°C en zelfs bij 30°C minder en kleinere lesies tot gevolg te hebben (Tabel 2; Fig. 3 en 4).Als gezonde bladhelften van Samsun NN-planten te drijven waren gelegd op water verscheen er callose in de buurt van het wondvlak (Fig. 5). Deze ophoping van callose was sterker als de bladhelften hadden gedreven op eosine Y in concentraties van 10 of 15 M (Fig. 6). In de zijnerven, die als gevolg van de behandeling met 15 M bruin waren geworden, was eveneens een sterke fluorescentie als gevolg van de aanwezigheid van callose te zien (Fig. 7 en 8).Als bladhelften van Samsun NN-planten na inoculatie met TMV te drijven waren gelegd op oplossingen van 10 of 15 M bij een temperatuur van 20°C bleek er niet alleen een reductie in aantal en afmeting van de lesies opgetreden te zijn, maar ook sterke fluorescentie als gevolg van aanzienlijke callose-afzettingen rondom de in hun uitbreiding geremde lesies (Fig. 9). De sterke fluorescentie verdween zelfs niet 3–5 dagen na inoculatie, hoewel bij bladeren die op water hadden gedreven dit al na 2–3 dagen het geval was (Fig. 10). Hadden de bladhelften na inoculatie echter bij 25°C op eosine Y gedreven dan was de fluorescentie rondom de lesies dezelfde als in de bladhelften die op water hadden gedreven.Bij bladhelften van gezonde bonen was niet veel ophoping van wondcallose waarneembaar en evenmin stimuleerde eosine Y de vorming ervan. Wel bracht deze stof een ophoping van callose teweeg op de zeefplaten van bladnerven (Fig. 11). Eveneens was er in de met eosine Y behandelde bladhelften fluorescentie in delen van de zijnerven (Fig. 12).Bij bonebladeren die waren geïnoculeerd met TMV was een sterke afzetting van callose te zien rondom de lesies die zich niet meer uitbreidden als gevolg van behandeling met eosine Y bij temperaturen tussen 20°C en 30°C (Fig. 13). In de controlehelften die op water hadden gedreven verdween de fluorescentie binnen 2 dagen na inoculatie (Fig. 14).Hadden bladschijfjes van Samsun-tabak na inoculatie met TMV gedreven op een oplossing van eosine Y dan bleek de virusvermeerdering in deze schijfjes niet geremd te zijn (Tabel 3).We kunnen concluderen dat er een correlatie bestaat tussen de hoeveelheid afgezette callose in de bladeren en de uiteindelijke grootte van de lokale lesies. De vraag blijft echter nog wel bestaan of callose-afzetting inderdaad de verspreiding van virus naar naburige cellen verhindert.  相似文献   

10.
Abstract

The granulosis virus (GV) of sugarcane shoot borer, Chilo infuscatellus Snelt., was found to be transmitted vertically when the fourth instar larvae were microfed with the virus at a sublethal dose of 1.1 x 103 inclusion bodies/larva. The virus infection was found to alter the sex ratio in pupae in favour of male (1 : 5.70—♀ : ♂) from the normal 1 : 1 ratio. The per cent pupation and adult emergence were also significantly reduced. No adults emerged from abnormal pupae that lacked pigmentation on the ventral surface of the first abdominal segment. The GV was also found to be transmitted from the infected adult to the offspring through eggs and 50% of the larvae that hatched were found to die due to virosis.  相似文献   

11.
Journal of Plant Diseases and Protection - Citrus tatter leaf virus (CTLV), a strain of apple stem grooving virus, is a virus of citrus that is of commercial importance for trifoliate orange...  相似文献   

12.
ABSTRACT Interactions between viruses in plants are common, and some viruses depend on such interactions for their survival. Frequently, a virus lacks some essential molecular function that another provides. In "helper-dependent" virus complexes, the helper virus is transmitted independently by a vector, whereas the dependent virus depends on molecular agents associated with the helper virus for transmission by a vector. A general mathematical model was developed of the dynamics of host plant infection by a helper-dependent virus complex. Four categories of host plants were considered: healthy, infected with helper virus alone, infected with dependent virus alone, and infected with both viruses. New planting of the host crop was constrained by a maximum abundance due to limitation of the cropping area. The ratio of infection rate to host loss rate due to infection is proposed as an important epidemiological quantity, A, that can be used as a measure of the mutual adaptation of the virus and host. A number of alternative equilibria of host infection could occur and were determined exclusively by parameter values; it was informative to display their distribution in the parameter plane: (1/A)(helper) versus (1/A)(dependent). A simple analysis of the distribution of the final equilibria illustrated that the dependent virus could affect the survival of the helper virus, so facilitation between the two can be reciprocal. The distribution of the final equilibria also indicated that a well-adapted helper virus increases the opportunity for a dependent virus to evolve and survive, and the model, therefore, explains why infection with a helper virus usually causes no or little damage to plants, whereas infection with a dependent virus or mixed infection with both often causes very severe damage.  相似文献   

13.
The ability of o,p′DDT to bind to the 8S moiety in the uterine cytosol or to interfere with the binding of 3H-estradiol-17β (3H-E2) to that binding component was investigated utilizing a 10–30% sucrose gradient sedimentation analysis. Attempts to demonstrate the binding of radiolabeled o,p′DDT to the 8S receptor in the mouse and rabbit were not successful, presumably due to the relatively low specific activity of the radiolabeled o,p′DDT, however, binding to the “nonspecific” 4S site(s) was detected. On the other hand, the addition of nonlabeled o,p′DDT inhibited the binding of 3H-E2 to the 8S receptor. Thus, o,p′DDT (2 μM) suppressed by 58% the binding of 3H-E2 (2 nM) in the 8S region in ovariectomized adult mice. Similarly, in immature rats three concentrations of o,p′DDT (16, 32, and 96 μM) inhibited by 39.5, 52.9, and 59.7% respectively, the binding of 3H-E2 (2.8 nM). Similar results were obtained with uterine preparations from mature rats. However, the suppression of binding of 3H-E2 in the 8S region resulted in an increased binding in the 3–4S region.A Scatchard plot analysis of the binding of 3H-E2 in the presence of o,p′DDT revealed the same number of binding sites as in the absence of o,p′DDT, indicating that o,p′DDT did not “destroy” the binding capacity. Also, this analysis revealed that o,p′DDT merely caused a decrease in the ratio of the bound to free E2, indicating that o,p′DDT binds to the receptor and thus interferes with E2 binding.In addition, our observations that the administration of o,p′DDT to immature female rats causes a marked increase in the levels of the uterine nuclear binding sites (nuclear estogren receptor) is a further indication that o,p′DDT acts as a typical estrogenic compound. However, whether o,p′DDT has antiestrogenic activity as well has not been established.  相似文献   

14.
Journal of Plant Diseases and Protection - Cecidochares connexa is currently the only effective biological control agent of Chromolaena odorata an invasive weed in West Africa. Recently, an...  相似文献   

15.
Sixty-four isolates of Bean yellow mosaic virus (BYMV) from cultivated and naturalized gladioli were divided into two pathogenic groups, necrotic spot (NS) and chlorotic spot (CS) groups on Chenopodium quinoa. NS-type isolates (S-22N and E-24N), CS-type isolates (S-22C and E-92C), and broad bean isolates (Sb-50C and Sb-12C) differed in their pathogenicity on Antirrhinum majus, Nicotiana benthamiana, Phaseolus vulgaris, Spinacia oleracea and Vigna unguiculata. The four gladiolus isolates were different from BYMV-B, -P, -O and C1YVV-N in their pathogenicity on these plants, while the two broad bean isolates were similar to BYMV-B, originally from broad bean. The nucleotide (nt) sequences of the 3′-terminal region of the BYMV RNA genome of the two NS-type isolates, the two CS-type isolates, the two broad bean isolates and BYMV-B, -P and -O were determined. In a phylogenetic tree based on the CP amino acid (aa) sequences, the two NS-type isolates clustered together (identity 98.4% and 98.2% at the nt and aa level, respectively). The two CS-type isolates clustered with BYMV-O (93.2 to 99.3% nt identity and 95.6 to 98.5% aa identity). The two broad bean isolates clustered with BYMV-B (99.0 to 99.5% nt identity and 98.9 to 99.6% aa identity). BYMV-P clustered with BYMV-CS (identity 97.7% and 99.3% at the nt and aa level, respectively). The obtained sequences were compared with those of the 3′-terminal regions of seven published BYMV isolates. In a phylogenetic tree based on deduced aa sequences, BYMV isolates were divided into four clusters. Received 1 July 1999/ Accepted in revised form 22 May 2000  相似文献   

16.
17.
Journal of Plant Diseases and Protection - Potato virus Y (PVY) is a destructive plant virus causing important damage in different crops, particularly in potato. PVY is transmitted in a...  相似文献   

18.
BACKGROUND: Glutathione S‐transferases (GSTs) have received considerable attention in insects for their roles in insecticide resistance. Laodelphax striatellus (Fallén) is a serious rice pest. L. striatellus outbreaks occur frequently throughout eastern Asia. A key problem in controlling this pest is its rapid adaptation to numerous insecticides. In this research, nine cDNAs encoding GSTs in L. striatellus were cloned and characterised. RESULTS: The cloned GSTs of L. striatellus belonged to six cytosolic classes and a microsomal subgroup. Exposure to sublethal concentrations of each of the six insecticides, DDT, chlorpyrifos, fipronil, imidacloprid, buprofezin and beta‐cypermethrin, quickly induced (6 h) up‐expression of LsGSTe1. The expression of LsGSTs2 was increased by chlorpyrifos, fipronil and beta‐cypermethrin. Furthermore, exposure of L. striatellus to fipronil, imidacloprid, buprofezin and beta‐cypermethrin increased the expression of the LsGSTm gene after 24 or 48 h. CONCLUSION: This work is the first identification of GST genes from different GST groups in Auchenorrhyncha species and their induction characteristics with insecticide types and time. The elevated expression of GST genes induced by insecticides might be related to the enhanced tolerance of this insect to insecticides and xenobiotics. Copyright © 2012 Society of Chemical Industry  相似文献   

19.
ABSTRACT The root-knot nematode Meloidogyne incognita is a major pathogen of a range of important crops. Currently, control is typically achieved by the use of nematicides. However, recent work suggests that manipulating the ability of roots to slough off border cells, which then act as a decoy to the nematode, can significantly decrease damage to the roots. We investigated the attractiveness of border cells to M. incognita and the response of the nematode to border cells in close proximity. We found very limited attraction, in that nematodes did not preferentially alter direction to move toward the border cells, but a large and significant increase in nematode speed was observed once they were in the immediate vicinity of border cells. We discuss the results in the context of physical and biological mechanisms in relation to the control of pathogenic nematodes.  相似文献   

20.
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