首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
 用紫外诱变法获得的青枯无毒菌株诱导番茄,研究了诱导番茄细胞内防御酶系及组织粗提液抑菌活性的影响。结果表明:番茄经无毒菌株处理后,体内与抗病反应相关的苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)、多酚氧化酶(PPO)及超氧化物歧化酶(SOD)等防御酶系活性均显著增加。无毒菌株可诱导产生植株体外和体内对致病菌有抑制作用的抑菌物质。表明青枯无毒菌株产生诱导抗性的机制可能是激活了植物本身的抗病代谢过程。  相似文献   

2.
Plants contain defense mechanisms that prevent infection by most fungi. Some specialized fungi have the ability to overcome plant defenses. The Zea mays (maize) seed chitinase ChitA has been previously reported as an antifungal protein. Here we report that ChitA is converted to a modified form by a protein secreted by the ear-rot pathogen Bipolaris zeicola (Holomorph = Cochliobolus carbonum). In denaturing chitinase zymograms, ChitA activity was detected in protein extracts from healthy seeds, but not in those from diseased seeds of ears that had been inoculated with B. zeicola. Furthermore, addition of proteins from diseased seeds to those from healthy seeds resulted in the loss of detectable ChitA activity. This indicated that protein extracts from diseased seeds contained a molecule that targets ChitA. We determined that this molecule is a secreted protein we term B. zeicola chitinase modifying protein (Bz-cmp). We purified ChitA from maize seed and Bz-cmp from sterile cultures of B. zeicola. Biochemical experiments demonstrated that Bz-cmp catalytically converts ChitA into a modified form that has reduced molecular mass in SDS-PAGE gels. Native chitinase zymogram analysis of modified and unmodified ChitA demonstrated that, contrary to our initial observation, Bz-cmp does not impair ChitA's chitinase activity but rather its chitin-binding ability. Our findings suggest that ChitA is an important component of defense in developing maize seeds and identifies Bz-cmp as a potential contributor to pathogenicity.  相似文献   

3.
A virus causing a disease of tomato, prevalent in the southern provinces of Iran, with symptoms of leaf-curling, stunting, reduction of leaf size, leaf corrugation, shortening of internodes and severe reduction in fruit yield, was shown to be transmissible to healthy tomato plants by grafting and by whiteflies ( Bemisia tabaci ), but not by sap inoculation. Geminivirus DNA was detected in extracts of diseased tomato plants by dot-blot hybridization assays using as probes full-length cloned DNA of Australian, Italian (Sardinian) or Jordanian strains of tomato yellow leaf curl virus (TYLCV). Geminivirus coat protein was detected in whitefly inoculated plants by dot immunobinding assay using polyclonal antibody raised against Jordanian TYLCV. A limited survey using the dot-blot hybridization assay for virus detection indicated the presence of the virus in tomato-growing provinces of southern but not northern Iran. Whitefly transmission experiments to tomato under controlled greenhouse conditions showed that some isolates of TYLCV-like geminiviruses from different parts of Iran differ in symptomatology.  相似文献   

4.
Experiments on the effect of various compounds with plant growth regulating activity led to the hypothesis that conditions inhibitory to indoleacetic acid (IAA) action or leading to a decrease in the IAA level in cucumber seedlings would be unfavourable for the development of cucumber scab, caused byCladosporium cucumerinum. Susceptibility decreased as the result of treatment with growth retardants, which cause an increase in IAA-oxidase activity in the plants, whereas application of indoleacetic acid or compounds expected to decrease the rate of oxidative breakdown of IAA in the seedlings resulted in an increase of susceptibility. Growing the plants under various periods of illumination also influenced both the susceptibility of the plants and the IAA-oxidase activity in the hypocotyl tissue.To obtain further information about the relation between the increase in resistance and the increase in the rate of IAA oxidation, the effect of one compound, viz. L-threo-β-phenylserine (abbr. phenylserine) was studied in more detail. The rate of oxidative breakdown of IAA was increased in extracts of hypocotyls and cotyledons of plants treated with phenylserine as compared with extracts of tissue of untreated plants. Extracts of phenylserine-treated plants were found to contain a higher cofactor and/or a lower inhibitor content than those of control plants. The substances involved were not identified, but this result may indicate a shift in the concentrations of various phenols in the tissue.The question must remain open whether a shift in the concentration of phenols some-how effected by phenylserine treatment determines both degree of susceptibility and rate of IAA oxidation independently, or whether the rate of IAA breakdown and the resulting change in IAA content in the plants is directly related to the degree of susceptibility.  相似文献   

5.
Antisera were raised in rabbits to extracts from healthy corn plants and from plants infected with corn stunt spiroplasma (CSS); they were prepared by partially purifying sap or tissue homogenates from whole stems by differential centrifugation and filtration. The titres of CSS-specific antibody in the antisera to diseased plant extracts (DPE) were monitored by spiroplasma deformation tests. After cross-absorption against healthy plant extracts, the DPE antisera detected cultured CSS at concentrations exceeding 106 cells/ml, compared with less than 105 cells/ml for homologous antiserum, and reacted more strongly against extracts from diseased than from healthy plants. A comparison of techniques for extracting diseased plant tissues showed that the reaction of stems and midribs against cultured CSS antiserum was two to three times stronger if the samples were lyophilized before extraction. When extracts from lyophilized tissues were used as test antigens the DPE antisera discriminated between diseased and healthy corn stems, midribs and roots as effectively as antiserum to cultured CSS. Preliminary attempts to detect CSS in its vector, Dalbulus maidis , were complicated by non-specific reactions of insect tissue extracts but concentrations equivalent to at least one CSS-infected insect/ml of sample were detected by antiserum to cultured CSS.  相似文献   

6.
In 1997, virus-like symptoms were observed in dimorphotheca plants(Dimorphotheca sinuata) at two different locations in Greece. In a greenhouse near Heraklion (Crete), plants showed chlorotic patches mainly in the older leaves, and a mild stunting; near Katerini (Macedonia), garden plants showed chlorotic rings. Sap inoculation of healthy dimorphotheca plants with extracts from diseased plants from the two regions, reproduced each of the two diseases. Examination by electron microscopy (EM) of samples from diseased plants from the first region revealed filamentous particles, whereas samples from the second region showed quasi-spherical particles. The filamentous particles were decorated in EM with antibodies specific to lettuce mosaic potyvirus (LMV). Samples from the second location reacted with antibodies specific to tomato spotted wilt tospovirus (TSWV) in EL1SA tests. It is concluded that LMV and TSWV are the causal agents of the disease noticed in Heraklion and in Katerini, respectively. http://www.phytoparasitica.org posting May 31, 1999.  相似文献   

7.
 用聚丙烯酰胺凝胶电泳(PAGE)分析了不同抗性番茄等基因系GCR-267和GCR-267的叶片可溶性蛋白组成在接种TMV番茄O株后的变化。实验发现敏感品系GCR-26的叶片可溶性蛋白的组成,与健株相比较,TMV侵染株发生显著的变化。接种后7天,除一部分蛋白质含量减少外,还有四种为健株及抗性品系TMV接种株所没有的新蛋白质产生,它们在10%凝胶上的迁移率分别为Rf0.31、0.33、0.39和0.45,其中Rf0.38和Rf0.39两种蛋白质含量极大。接种后10天Rf0.31和Rf0.45两带趋于消失,但Rf0.33和0.39两带继续积累。经电泳和免疫双扩散试验证明Rf0.33蛋白带是TMV外壳蛋白:Rf0.39蛋白带与TMV外壳蛋白无关。该蛋白也不具有过氧化物酶,多酚氧化酶、酸性磷酸酶、酯酶、苹果酸脱氧酶,葡萄糖-6-磷酸脱氢酶或谷氨酸脱氢酶的催化活性,分子中不含有糖类物质。SDS-PAGE测定其分子量为14,200道尔顿。
抗性品系GCR-267的TMV接种株的叶片可溶性蛋白组成未出现象感病品系GCR-26那样的变化。
讨论了这种变化与番茄抗、感病性之间的关系。  相似文献   

8.
In this study, we investigated the ability of DL-3-aminobutyric acid (BABA) to protect tomato against bacterial wilt caused by Ralstonia solanacearum. This was combined with studies of accumulation of total phenolic compounds, free and total salicylic acid (SA), and activity of enzymes related to plant defence, i.e., polyphenol oxidase (PPO) and catalase (CAT). Under greenhouse conditions, tomato plants pre-treated by soil drenching with BABA profoundly reduced disease severity of bacterial wilt compared to plants receiving a soil drench with water. Thus, BABA reduced leaf wilting index by 75.3 % and vascular browning index by 69.9 %, without any in vitro inhibitory activity on the pathogen. BABA treatment significantly reduced the population of R. solanacearum in stems of tomato plants and additionally also significantly increased both fresh and dry weight of roots and shoots of tomato plants compared with the inoculated control. Application of BABA resulted in a high increase in PPO activity both in plants with and without inoculation. Compared to water-treated plants, treatment with BABA also induced a significant increase of total phenolic compounds as well as of free and total SA in leaves of both inoculated and non-inoculated tomato plants at all sampling times. CAT activity decreased in tomato plants treated with BABA in comparison with the water-treated control plants and the decrease in activity correlated with an increasing total SA accumulation. These findings suggest that BABA treatment resulted in induction of resistance to bacterial wilt in tomato.  相似文献   

9.
The causal agent of bacterial spot of capsicum and tomato grown in different regions in Yugoslavia was investigated. Isolations were made from diseased material collected in recent years. The biochemical and physiological characteristics of isolated bacteria were studied by standard bacteriological tests. The race of the pathogen was determined on differential cultivars of capsicum and tomato. The causal agent of the disease was identified according to the concepts of the time as Xanthomonas campestris pv. vesicatoria. Strains isolated from diseased capsicum were non-pectolytic and non-amylolytic, and did not infect tomato plants. According to the reaction of capsicum cv. Early Calwonder and its isogenic lines, these strains belonged to'pepper races'1 and 3 of X. vesicatoria. Tomato strains showed pectolytic and amylolytic activity and were not pathogenic to capsicum. Accordingly, the capsicum strains could now be considered to be X. axonopodis pv. vesicatoria and the tomato strains X. vesicatoria.  相似文献   

10.
FromGloeosporium olivarum Alm. cultures a phytotoxic substance has been isolated, which was obtained in a pure form as a white powder which decomposed at 205–210°C and, after acid hydrolysis, yielded glycine, aspartic acid and an as yet unidentified compound.The purified toxin induced symptoms on tomato cuttings, which were indistinguishable from those caused by the crude culture filtrate of the fungus.  相似文献   

11.
A few polyphenols (tannic acid and digallic acid), anthraquinone derivatives (rufianic acid and quinalizarin), and detergents (an alkylaryl sulfonate) proved to be especially effective inhibitors of pectolytic and cellulolytic enzymes of four phytopathogenic fungi. Some of these substances prevented the infection of tomato leaves withAlternaria solani. It appears, however, that inhibition of the germination of conidia was the crucial effect rather than inhibition of the enzymes. Alkylaryl sulfonate and rufianic acid were able to reduce the maceration of bean hypocotyls byRhizoctonia solani. Rufianic acid also counteracted tomato wilt, caused byFusarium oxysporum f.lycopersici, especially in the case of postinfectional application. On the other hand preinfectional rather than postinfectional application of rufianic acid had effect onVerticillium wilt of tomato.In one case, viz.Fusarium wilt, the mode of action of rufianic acid was investigated in greater detail. The presence of this substance could be demonstrated in the exudates of healthy and infected plants after application to the roots. The pectolytic and cellulolytic activity of the exudates and the pectinmethylesterase activity of stem extracts of infected, rufianic acid treated plants were reduced, as well as the quantity of mycelium in the stems. Possibly other mechanisms are also involved in the mode of action of rufianic acid.The prospects of using pectolytic enzyme inhibitors for the therapy of plant diseases are discussed.  相似文献   

12.
A liquid based Pseudomonas fluorescens (Pf1) bioformulation was found to contribute the restriction of Fusarium oxysporum f. sp. lycopersici in tomato roots by inducing defence enzymes. Induction of defence enzymes such as phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenoloxidase (PPO), catalase, β-1,3 glucanase and super oxide dismutase (SOD), was studied in tomato plants pretreated with liquid as well as a talc based formulation of Pf1 challenged with F. oxysporum f. sp. lycopersici in glasshouse vegetable production systems. There were increased activities of PAL, PO, PPO, catalase and β-1 3-glucanases in tomato plants treated with a combined application of seedling dip?+?soil application?+?foliar spray of liquid and talc formulation of Pf1 when compared to pathogen inoculated and untreated healthy controls. The activities of the above enzymes started to increase at 3rd day, reached maximum levels on 8-9th day and thereafter declined gradually. Similarly, native polyacralamide gel electrophoresis (PAGE) analysis revealed that one to six isoforms of the defence enzymes each with a higher intensity were expressed in these treatments, whereas fewer isoforms with less intensity were noticed in inoculated controls. These results suggest that the retardation of the invasion of F. oxysporum f. sp. lycopersici in tomato roots resulting from treatment with the liquid formulation of Pf1 was due to enhancement of activities of enzymes involved in the phenylpropanoid pathway. These results suggest that induced systemic resistance occurred in the treated tomato plants.  相似文献   

13.
感染叶锈菌(Puccinia triticina)的小麦病叶段經消毒后在无光条件下飼以充足养分能产生大量夏孢子堆;并在培养后40—50天仍能继續形成新鲜孢子堆,部分菌絲从叶段切面生出。經三苯基四唑化氯染色,质壁分离测定及切片鏡检观察証明寄主細胞在培养中存活的时限为10天左右。这些資料说明小麦锈菌具有一定腐生能力,作者对“绝对寄生性”的概念以及过敏反应的生物学基础作了評論。不同碳源中葡萄糖、果糖、蔗糖及甘油对叶段上孢子堆的形成都有极明显的促进作用;氮源以蛋白腖为佳,无机氮亦可代替。培养过程中夏孢子堆有时变黑而死亡,試驗証明这是由于酚类物质經多元酚酶作用而氧化,产生对菌具有更強毒性的醌类物质,最后形成黑色素。这一过程可以被还原性的抗坏血酸抑制。叶段上所产生夏孢子在合成培养基上能形成白色小菌落,对碳氮源的要求大体与叶段培养相同。飼标記葡萄糖(G_1~(14)及G_(1～6)~(14)标記)后测定証实锈菌及病組織葡萄糖酵解的HMP趋势較強,健組織则EMP趋势較強。病組織有机酸含G~(14)的量显著高于健組織;病健組織間叶綠素、醣及氨基酸中G~(14)的含量則无差异。抗、感病品种間醣的含量似无明显差异,酚的绝对含量与抗病性无相关,但抗病品种受病后酚类物质增加,感病品种則相反。感病組織中去氫酶活性及抗坏血酸含量則較抗病組織为高。对抗锈机制的理論也作了討論。  相似文献   

14.
The effect of indole-acetic acid (IAA) on the development of symptoms caused by Pythium ultimum on tomato plants was investigated using different bioassays. Application of IAA (5 μg ml−1) on tomato seedlings inoculated with P. ultimum did not affect their emergence suggesting that IAA did not affect the severity of Pythium damping-off. However, IAA was shown to influence the development of P. ultimum symptoms on tomato plantlets. Low concentrations of IAA (0–0.1 μg ml−1) within the rhizosphere of plantlets increased the severity of the symptoms caused by P. ultimum, while higher concentrations (10 μg ml−1), applied either by drenching to the growing medium or by spraying on the shoot, reduced the symptoms caused by this pathogen. In addition, the study demonstrated that P. ultimum produces IAA in liquid culture amended with L-tryptophan, tryptamine or tryptophol (200 μg ml−1) and in unamended culture.  相似文献   

15.
We characterised the host range and physical properties of Tomato chlorotic dwarf viroid. Among the 46 plant species inoculated with the viroid, two in the family Compositae and 23 in the family Solanaceae were found to be systemic hosts. The viroids in the crude sap from diseased tomato plants were thermally inactivated by heating to 100°C for at least 40 min. These viroids also lost their infectivity when diluted in phosphate buffer to at least 10−6, or after 3 days of incubation at room temperature. However, the infectivity of the viroids in dried crude sap from the plants persisted throughout the 50-day test period.  相似文献   

16.
Tomato is an important species grown in many countries, either in fields or greenhouses. Despite decades of improvement, it is still susceptible to diseases, thus requiring the use of chemical pesticides, especially in greenhouses. Nevertheless it is imperative to reduce the use of environmental-unfriendly phytochemicals and favor less toxic tools to fight pathogens. Plants possess elaborate mechanisms against diseases that can lead to resistance. In the present work, we investigate the induction of plant defenses by means of extracts from plants widespread and easy to find, also known for their antimicrobial properties. Aqueous extracts of pepper ‘Rocoto’, wild rue and ethanolic extracts of clove powder (whose inhibiting effect was assessed on Oidium sp. spores) were tested on tomato plants for their ability to induce expression of different defense genes (PRs and regulatory proteins) after spraying. As revealed by RT-qPCR, all extracts were able to induce mRNA accumulation of different PR and MAPK regulators for several hours upon treatment, with clove and wild rue being the strongest. This effect could also be reproduced in tomato plants after a second treatment, 15 days after the first. The same extracts were tested in tomato and tobacco plants via leaf infiltration, showing necrotic symptoms associated with the hypersensitive response, thus confirming the priming capacity of the extracts. The involvement of salicylic acid (SA) in these responses was verified by HPLC analysis and in SA-depleted transgenic tobacco (NahG). The results obtained suggest that natural antimicrobial extracts can be used to induce plant defenses and protect valuable crops. At the same time these low-cost extracts do not pose a threat to the environment or the farmer and can help reduce the farming costs, especially in developing countries.  相似文献   

17.
ABSTRACT Fusarium oxysporum and F. arthrosporioides, pathogenic on Orobanche aegyptiaca, were transformed with two genes of the indole-3-acetamide (IAM) pathway leading to indole-3-acetic acid (IAA) to attempt to enhance virulence. Transgenic F. oxysporum lines containing both the tryptophan-2-monooxyngenase (iaaM) and indole-3-acetamide hydrolase (iaaH) genes produced significantly more IAA than the wild type. IAM accumulated in culture extracts of F. oxysporum containing iaaM alone. F. arthrosporioides containing only iaaM accumulated IAM and an unidentified indole. Some transformants of F. oxysporum expressing only the iaaM gene also produced more IAA than the wild type. Sub-threshold levels (that barely infect Orobanche) of transgenic F. oxysporum expressing both genes and of F. arthrosporioides expressing iaaM were more effective in suppressing the number and size of Orobanche shoots than the wild type on tomato plants grown in soil mixed with Orobanche seed. Stimulating an auxin imbalance enhanced pathogen virulence by affecting the host in a manner similar to low doses of auxin herbicides such as 2,4-dichlorophenoxy acetic acid.  相似文献   

18.
Withania somnifera is an important medicinal plant native to the Indian-sub continent. Owing to the presence of a number of precious alkaloids, flavonoids and withanolides, it is widely used in the Indian and African systems of medicines. It is severely affected by phytoplasma present in the sieve tubes of phloem. With a view to micropropagate phytoplasma-free W. somnifera plants, an efficient and effective nested PCR-based system was developed for detection of associated phytoplasmas. Universal primers, designed from the 16S rDNA sequences of phytoplasmas, were applied in direct/nested-PCR. Total DNA extracts from leaf tissues of 33 suspected symptomatic and 11 non-symptomatic plants were subjected to direct PCR. The direct PCR products were subsequently employed as templates in nested PCR. The nested PCR could reamplify direct PCR products yielding a DNA fragment of 1.4 kb. A phytoplasma was detected in all the diseased plants and not from the healthy looking plants. Further, it was sensitive enough to amplify phytoplasma DNA obtained from crude DNA diluted up to 2500 times from naturally infected plants and also from various stages of in vitro-propagated diseased plants. Identical restriction fragment polymorphism enzyme profiles were obtained following restriction enzyme digestion of nested PCR products, obtained from five different plants, by EcoRI, AluI and RsaI restriction endonucleases. The developed nested PCR based system should facilitate indexing of the phytoplasma in different stages of in vitro-generated plants and probably identification of, as yet unknown, hosts and vectors of phytoplasma associated with phytoplasma disease of W. somnifera.  相似文献   

19.
Crown and root rot of tomato and sweet pepper can be caused by Phytophthora parasitica. In this work, 23 P. parasitica isolates from diseased pepper or tomato plants as well as 54 isolates from 23 monocrop tomato soils (from Spain and Chile) and one from a pepper soil were studied for their host–pathogen response. Results show significant host specificity for the isolates from tomato plants and tomato soils (63 of 64 isolates were unable to cause disease in pepper). None of the pepper plant/soil isolates showed pathogenicity on tomato, and only four of 14 reproduced their pathogenicity on pepper. Only one tomato isolate was pathogenic to both Solanaceae species. Two different inoculation protocols were evaluated (substrate irrigation and stem cutting). All isolates which expressed pathogenicity when stem inoculated also did it when root inoculated, but not vice-versa. Therefore, the recommended test protocol for tomato and pepper breeding programmes is that based on root inoculation by irrigation.  相似文献   

20.
A soilborne disease of lettuce, associated with necrosis and dieback, has been found with increasing frequency in California and Arizona over the last 10 years. An isometric virus, serologically related to Tomato bushy stunt virus (TBSV), was consistently isolated from lettuce plants with these disease symptoms. Back-inoculation to healthy lettuce plants and subsequent reisolation of the virus from symptomatic lettuce leaves suggested that this virus was the causal agent of this disease. A tombusvirus was also associated with a necrosis disease of greenhouse-grown tomatoes in Colorado and New Mexico. Complementary DNA representing the 3' end of viral genomic RNAs recovered from diseased lettuce and tomato plants had identical nucleotide sequences. However, these sequences were divergent (12.2 to 17.1%) from sequences of the previously described strains of TBSV, Petunia asteroid mosaic virus (PAMV), Artichoke mottled crinkle virus, and Carnation Italian ringspot virus. Additional tombusvirus isolates were recovered from diseased lettuce and tomato plants and these were most closely related to the TBSV-cherry strain (synonymous with PAMV) and to Cucumber necrosis virus based on comparison of 3'-end sequences (0.1 to 0.6% and 4.8 to 5.1% divergence, respectively). Western blot analysis revealed that the new tombusvirus isolated from diseased lettuce and tomato plants in the western United States is serologically distinct from previously described tombusvirus species and strains. Based on genomic and serological properties, we propose to classify this virus as a new tombusvirus species and name it Lettuce necrotic stunt virus.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号