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 15 毫秒
1.
Ralstonia solanacearum causes a lethal bacterial wilt disease in many plants by colonizing the vascular tissues of the hosts. Upon inoculation of tomato seedlings through either leaf or root, the wilting symptoms occur first at the apical region and then proceed downward along the shoot. The systemic order of the disease initiation and progression in the host, independent of the site of pathogen inoculation, is yet to be investigated. To understand the disease progression more clearly, we have carried out a systematic study of the pathogen localization by GUS staining of inoculated tomato seedlings, at 24-hour intervals from 0 days post-inoculation (dpi) to 5 dpi. In both inoculation methods, pathogen colonization was observed at 1 dpi at the apical meristem as well as the cotyledon leaves, where the disease initiates. As the disease progressed, colonization by the pathogen towards the lower region of the shoot was observed. Disease consistency and pathogenicity magnitude were observed to be higher using the leaf inoculation method than the root inoculation method. Several R. solanacearum transposon-induced mutants that were reduced in virulence by root inoculation but virulent by leaf inoculation were obtained. Using GUS staining, it was observed that these mutants were unable to localize in the shoot region when inoculated in the root. Our study indicates that the apical meristem and the cotyledon leaves are the first regions to be colonized in inoculated tomato seedlings, which might explain the disease initiation from this region.  相似文献   

2.
Bacterial wilt is a serious problem affecting many important food crops. Recent studies have indicated that treatment with biotic or abiotic stress factors may increase the resistance of plants to bacterial infection. This study investigated the effects of magnesium oxide nanoparticles (MgO NP) on disease resistance in tomato plants against Ralstonia solanacearum, as well as its antibacterial activity. The roots of tomato seedlings were inoculated with R. solanacearum and then immediately treated with MgO NP; the treated plants showed very little inhibition of bacterial wilt. In contrast, when roots were drenched with a MgO NP suspension prior to inoculation with the pathogen, the incidence of disease was significantly reduced. Rapid generation of reactive oxygen species such as O2?˙ radicals was observed in tomato roots treated with MgO NP. Further O2?˙ was rapidly generated when tomato plant extracts or polyphenols were added to the MgO NP suspension, suggesting that the generation of O2?˙ in tomato roots might be due to a reaction between MgO NP and polyphenols present in the roots. Salicylic acid‐inducible PR1, jasmonic acid‐inducible LoxA, ethylene‐inducible Osm, and systemic resistance‐related GluA were up‐regulated in both the roots and hypocotyls of tomato plants after treatment of the plant roots with MgO NP. Histochemical analyses showed that β‐1,3‐glucanase and tyloses accumulated in the xylem and apoplast of pith tissues of the hypocotyls after MgO NP treatment. These results indicate that MgO NP induces systemic resistance in tomato plants against R. solanacearum.  相似文献   

3.
Bacterial wilt caused by Ralstonia solanacearum is a serious disease of peanut (Arachis hypogaea) in China. However, the molecular basis of peanut resistance to R. solanacearum is poorly understood. Arachis duranensis, a wild diploid species of the genus Arachis, has been proven to be resistant to bacterial wilt, and thus holds valuable potential for understanding the mechanism of resistance to bacterial wilt and genetic improvement of peanut disease resistance. Here, suppression subtractive hybridization (SSH) and macroarray hybridization were employed to detect differentially expressed genes (DEGs) in the roots of A. duranensis after R. solanacearum inoculation. A total of 317 unique genes were obtained, 265 of which had homologues and functional annotations. KEGG analysis revealed that a large proportion of these unigenes are mainly involved in the biosynthesis of phytoalexins, particularly in the biosynthetic pathways of terpenoids and flavonoids. Subsequent real‐time polymerase chain reaction (PCR) analysis showed that the terpenoid and flavonoid synthesis‐related genes showed higher expression levels in a resistant genotype of A. duranensis than in a susceptible genotype, indicating that the terpenoids and flavonoids probably played a fundamental role in the resistance of A. duranensis to R. solanacearum. This study provides an overview of the gene expression profile in the roots of wild Arachis species in response to R. solanacearum infection. Moreover, the related candidate genes are also valuable for the further study of the molecular mechanisms of resistance to R. solanacearum.  相似文献   

4.
Ralstonia solanacearum causes bacterial wilt disease in Solanaceae spp. Expression of the Phytophthora inhibitor protease 1 (PIP1) gene, which encodes a papain‐like extracellular cysteine protease, is induced in R. solanacearum‐inoculated stem tissues of quantitatively resistant tomato cultivar LS‐89, but not in susceptible cultivar Ponderosa. Phytophthora inhibitor protease 1 is closely related to Rcr3, which is required for the Cf‐2‐mediated hypersensitive response (HR) to the leaf mould fungus Cladosporium fulvum and manifestation of HR cell death. However, up‐regulation of PIP1 in R. solanacearum‐inoculated LS‐89 stems was not accompanied by visible HR cell death. Nevertheless, upon electron microscopic examination of inoculated stem tissues of resistant cultivar LS‐89, several aggregated materials associated with HR cell death were observed in xylem parenchyma and pith cells surrounding xylem vessels. In addition, the accumulation of electron‐dense substances was observed within the xylem vessel lumen of inoculated stems. Moreover, when the leaves of LS‐89 or Ponderosa were infiltrated with 106 cells mL?1 R. solanacearum, cell death appeared in LS‐89 at 18 and 24 h after infiltration. The proliferation of bacteria in the infiltrated leaf tissues of LS‐89 was suppressed to approximately 10–30% of that in Ponderosa, and expression of the defence‐related gene PR‐2 and HR marker gene hsr203J was induced in the infiltrated tissues. These results indicated that the response of LS‐89 is a true HR, and induction of vascular HR in xylem parenchyma and pith cells surrounding xylem vessels seems to be associated with quantitative resistance of LS‐89 to R. solanacearum.  相似文献   

5.
Clavibacter michiganensis subsp. michiganensis (Cmm), the causal agent of bacterial canker and wilt, causes severe economic losses in tomato net‐houses and greenhouses worldwide. In this study, seedlings which were transplanted and inoculated monthly over 2 years wilted and died earlier in the spring (21–24°C) and autumn (18–23°C) than in the winter (15–18°C) and summer (28–31°C): T50 (the time taken for 50% of the plants to wilt or die) was 2 and 3–4 months after inoculation, respectively. A highly significant correlation was found between the average temperatures during the first month after inoculation and T50; the shortest T50 mortality (70 days) was observed for an average temperature of 26°C. Expression of virulence genes (pat‐1, celA, chpC and ppaA) by Cmm was higher in plants inoculated in the spring than in those inoculated in the summer. In another set of experiments, seedlings were inoculated and maintained in controlled‐environment growth chambers for 2 weeks. Subsequently, they were transplanted and maintained in commercial‐type greenhouses for 4–5 months. The temperatures prevailing in the first 48 h after inoculation were found to affect Cmm population size and virulence gene expression and to have season‐long effects on bacterial canker development.  相似文献   

6.
When the biocontrol agent Pythium oligandrum (PO) colonizes the rhizosphere, it suppresses bacterial wilt disease in tomato (Solanum lycopersicum cv. Micro‐Tom) caused by Ralstonia solanacearum, and a homogenate of its mycelia exhibits elicitor activity, inducing an ethylene (ET)‐dependent defence response in Micro‐Tom. Since salicylic acid (SA) and jasmonic acid (JA) play an important role in plant defence responses to pathogens, the involvement of SA‐ and JA‐dependent signal transduction pathways in resistance to R. solanacearum was investigated in tomato roots treated with a mycelial homogenate of PO. Bacterial wilt disease was also suppressed in tomato cv. Moneymaker treated with the PO homogenate. However, the SA‐inducible PR‐1(P6) gene was not up‐regulated in either Micro‐Tom or Moneymaker. SA did not accumulate in homogenate‐treated roots in comparison with distilled water‐treated controls, even 24 h after inoculation. Induced resistance against R. solanacearum was not compromised in SA‐non‐accumulating NahG transgenic plants treated with the PO homogenate. On the other hand, the expression of the JA‐responsive gene for the basic PR‐6 protein was induced in both tomato cultivars treated with the PO homogenate. Furthermore, quantitative disease assays showed that the induced resistance against R. solanacearum was compromized in PO homogenate‐treated jai1‐1 mutant plants defective in JA signalling. These results indicated that the JA‐dependent signalling pathway is required for PO‐induced resistance against R. solanacearum in tomato.  相似文献   

7.
  相似文献   

8.
  相似文献   

9.
［目的］ 通过测试vasK基因突变株对番茄的致病力变化,评价该基因在青枯菌致病过程中的作用。［方法］根据青枯菌(Ralstonia solanacearum)中存在的Ⅵ型分泌系统基因簇中的核心基因vasK序列设计PCR引物,扩增并克隆vasK基因,将庆大霉素抗性基因(Gm)插入vasK基因内部,克隆至自杀质粒pK18mobsacB中,获得重组自杀质粒pK18 vasK Gm。将自杀质粒电转化至青枯菌GMI1000感受态细胞中,采用同源重组双交换法,将野生型vasK基因置换。对vasK基因突变菌株进行三步筛选和PCR扩增鉴定。［结果］ 筛选获得了具有庆大霉素抗性的目标基因被抗性基因替换的青枯菌突变株(GMI1000 m)。土壤接种番茄青枯菌结果显示,突变株GMI1000 m的致病性较野生型GMI1000明显下降。［结论］vasK基因在青枯菌致病过程中具有重要作用。  相似文献   

10.
Bacterial wilt caused by Ralstonia solanacearum is a destructive disease for many crops. The aim of this study was to investigate the phylogenetic relationships and genetic structure of an R. solanacearum population from diverse origins in Taiwan. All 58 tested isolates belonged to phylotype I, except the two biovar 2 isolates from potato. These belonged to phylotype IIB sequevar 1 and were identical to known potato brown rot strains, which were probably introduced. Phylotype I isolates were grouped into 10 sequevars. Sequevar 15 was predominant (34 out of 56 isolates). Its distribution covered the whole island and it was largely associated with solanaceous crops such as tomato, and with tomato field soil. A total of 14 haplotypes were identified based on a partial endoglucanase gene sequence. Parsimony network analysis revealed that haplotype A was the oldest haplotype in the local population. It encompassed all but one of the sequevar 15 isolates. Large variation in virulence on tomato was observed among the 58 isolates, and seven pathotypes were identified. Significant genetic differentiation was detected among pathotypes. Moreover, genetic differentiation was detected between biovar 3 and biovar 4 subgroups and between the strains associated with solanaceous and non‐solanaceous species, but none was detected between strains from different geographic origins. The results suggest that the phylotype I population in Taiwan is homogeneous, while mutation and local adaptation to specific ecological niches keep shaping the population.  相似文献   

11.
A multigene family encoding HLK effectors is well conserved in all Ralstonia solanacearum strains. The HLK family contains three paralogous members. We constructed single, double, and triple deletion mutants of hlk genes in R. solanacearum strain OE1-1 and characterized HLK effectors by comparing the phenotypes of the strains. HLK effectors exhibited some functional redundancy. While the triple deletion mutant was significantly impaired in virulence on tomato and multiplied less efficiently than the wild type in the leaves, the mutant was as virulent as the wild type on eggplant and tobacco.  相似文献   

12.
X. Li  Y. Liu  L. Cai  H. Zhang  J. Shi  Y. Yuan 《Plant pathology》2017,66(8):1345-1356
Tobacco bacterial wilt caused by Ralstonia solanacearum is a serious disease affecting tobacco cultivation in southwest China. The response surface methodology was employed to evaluate the optimal conditions of tobacco bacterial wilt, and green fluorescent protein gene (gfp) labelling was applied to monitor the location and survival dynamics of R. solanacearum (Rs::gfp) on tobacco roots and in soil under these optimal conditions. The results showed that the highest wilt incidence was 91.13%, which occurred when the population reached 6.6 × 106 CFU/g soil, the temperature was 30.55 °C, and the humidity was >81.42%. The Rs::gfp densely colonized the root tips and root hairs, and cells of Rs::gfp were observed intermittently in the elongation zone or at the point of the emerging lateral roots. The Rs::gfp number in the rhizosphere soil was 10.75‐, 73.13‐ and 74.86‐times higher than that in the bulk soil at 10, 15 and 20 days after transplantation, respectively. Increased colonization by Rs::gfp was related to the population of the pathogen, the environmental temperature and the humidity in the soil. These three conditions determined whether R. solanacearum would induce tobacco wilt. This is the first study to investigate factors affecting the virulence of a tobacco wilt bacterial pathogen, which is important for conducting field diagnosis and biocontrol of tobacco bacterial wilt.  相似文献   

13.
A leaf spot disease on wasabi plants grown in commercial greenhouses in the Fraser Valley of British Columbia was characterized. Mycelial growth and pycnidial formation were observed within lesions when leaves were incubated under conditions of high humidity. Isolation from diseased tissues consistently yielded colonies of a Phoma species. Sequence analysis of the rDNA internal transcribed spacer (ITS1‐5.8S‐ITS2) region of eight isolates showed 100% nucleotide sequence identity with Phoma wasabiae and Leptosphaeria biglobosa subspecies ‘occiaustralensis’ and 99.2% identity with L. biglobosa ‘canadensis’. Pathogenicity studies on wasabi leaves showed that wounding greatly facilitated infection and enhanced lesion development for most isolates but was not required for all isolates. Chlorotic areas appeared around the inoculation sites within 4 days, followed by necrosis. Isolates displayed a range of virulence, from weakly to highly virulent, on wasabi leaves. Similar results were observed on leaves of canola cultivar Westar, i.e. wounding significantly increased lesion size and isolates displayed a range of virulence. An isolate of Leptosphaeria maculans ‘brassicae’ from canola was highly virulent on wasabi and canola leaves, causing lesions similar to those of L. biglobosa ‘occiaustralensis’ while an isolate of L. biglobosa ‘canadensis’ from canola was weakly virulent on both hosts and required wounds to infect. These results demonstrate that isolates of L. biglobosa ‘occiaustralensis’ from wasabi are as virulent as L. biglobosa ‘canadensis’ on wasabi and canola leaves but in some cases were comparable in virulence to L. maculans ‘brassicae’.  相似文献   

14.
Bacterial wilt (BW), caused by Ralstonia solanacearum, is one of the most destructive bacterial diseases of Solanaceous species worldwide. The species infects plants in more than 200 species and 50 families and was ranked second in a list of the top 10 most scientifically and economically important bacterial plant pathogens [1]. The molecular mechanisms underlying resistance and the functions of R. solanacearum effectors are beginning to be uncovered, and much remains to be discovered. In this mini-review, we provide a summary of host resistance and R. solanacearum virulence mechanisms, with a focus on tomato.  相似文献   

15.
青枯菌通过Ⅲ型分泌系统向寄主植物细胞分泌100多种效应蛋白,对寄主植物的抗感病性产生影响。青枯菌效应蛋白RipQ启动子区存在典型的HrpB识别序列PIP box (5′-TTCGG-N15-TTCGC-3′),但其功能尚未明确。本研究分析了RipQ在青枯菌4种演化型菌株中的分布情况。以青枯菌GMI1000为出发菌,构建ripQ缺失突变体和过表达菌株,研究效应蛋白RipQ在青枯菌-番茄植物互作中的功能。结果显示,ripQ广泛分布于除演化型IV的不同青枯菌类群中。与野生型菌株相比,ripQ突变体在番茄上的致病力有一定程度的增强,而ripQ过表达菌株的致病力显著降低。突变体和过表达菌株在培养基中的生长与野生型没有区别,但过表达菌株在番茄体内的繁殖能力下降。RipQ过表达菌株侵染番茄后hrpB、hrpG和epsA基因表达量显著下调,且能够诱导番茄叶片H2O2的大量累积,过敏性坏死反应标志基因hin1和水杨酸信号通路标志基因PR1a的诱导表达。另外,在番茄上瞬时表达ripQ也可以观察到H2O2积累及叶片细胞坏...  相似文献   

16.
Large‐scale virulence tests using trees or saplings are expensive, time‐consuming and require a considerable amount of space. The suitability of using ‘Golden Delicious’ apples as a rapid screen for identifying Ophiostoma novo‐ulmi transformants with reduced virulence was thus evaluated. When a collection of O. novo‐ulmi field isolates belonging to subspecies novo‐ulmi or americana was inoculated to apples, members of subsp. novo‐ulmi induced, on average, larger necrotic lesions than subsp. americana isolates. The size of the lesions on apples was not correlated with mycelial growth rate of isolates on nutrient agar. Insertional mutants from O. novo‐ulmi subsp. novo‐ulmi isolate H327 were inoculated to ‘Golden Delicious’ apples and Ulmus parvifolia × U. americana saplings in parallel experiments. Results clearly indicated that the O. novo‐ulmi transformants included several exhibiting significantly altered levels of virulence. Variability among replicates within a treatment was reduced in apple inoculation data compared to elm sapling data. Overall, the ‘Golden Delicious’ apple assay was found to be an excellent means for rapidly assessing the virulence level of O. novo‐ulmi isolates.  相似文献   

17.
The viable but nonculturable (VBNC) state is induced in the bacterial wilt pathogen Ralstonia solanacearum under prolonged environmental stress. These VBNC cells lose their ability to grow on standard media such as CPG agar, but some of the cells can recover this ability on media supplemented with sodium pyruvate (SP), that degrades hydrogen peroxide. Recently, we suggested that some of the cells in the low-temperature-induced SP-recoverable VBNC state regained their ability to grow on CPG agar after exposure to moderate temperature. These revived cells also retained their virulence on tomato. Although R. solanacearum is detectable on semiselective media, VBNC cells are not detectable on any known semiselective media for the pathogen. To create a suitable medium to detect VBNC cells, we therefore added various compounds that can either degrade hydrogen peroxide or serve an antioxidant function in a semiselective medium, modified SMSA. SP at 5 g/l most improved the sensitivity of R. solanacearum detection. Furthermore, counts on modified SMSA plates for R. solanacearum that had been added to field soil also increased after the addition of 5 g/l SP. SP thus improved the medium’s sensitivity for the detection of R. solanacearum by rescuing a portion of the VBNC cells.  相似文献   

18.
To study the behavior and mutation of Ralstonia solanacearum in Solanum toxicarium, which is resistant to bacterial wilt, S. toxicarium was grown in aseptic culture and inoculated with R. solanacearum. Although 60%–80% of the inoculated plants were wilting after 2 to 3 days, most wilted plants had recovered by 20 days after inoculation. The pathogen was reisolated from over 98% of inoculated plant stems, but the percentage of recovery decreased the closer the isolation sites were toward the upper stem sections. Three colony types, characterized as fluidal white, nonfluidal red, and a mixture of fluidal white and nonfluidal red, were reisolated from the stems. Nonfluidal red colonies were less virulent on tomato plants than fluidal white colonies.  相似文献   

19.
Tomato chlorosis virus (ToCV) is an emerging crinivirus in Brazil that causes an economically important disease in tomato (Solanum lycopersicum) and other solanaceous species. ToCV is transmitted predominantly by the whitefly Bemisia tabaci Middle East‐Asia Minor 1 (MEAM1, formerly biotype B), in a semipersistent manner. As all cultivated tomato varieties and hybrids are susceptible to this crinivirus, the main alternatives for the control of the disease are the use of healthy seedlings for transplanting and the chemical control of the insect vector. The objective of this work was to evaluate the responses of tomato genotypes to infection with this crinivirus and their tolerance to the disease in order to support the development of other alternatives for disease control. Resistance to infection was evaluated by ToCV inoculation with viruliferous B. tabaciMEAM1 followed by virus detection by RT‐PCR and RT‐qPCR. To measure tolerance to the disease, plant development and fruit yield of ToCV‐infected and healthy plants were compared. Among 56 genotypes, only the lineage IAC‐CN‐RT (S. lycopersicum ‘Angela Gigante’ × S. peruvianum ‘LA 444‐1’) was highly resistant to infection with ToCV. Tolerance to the disease over two trials with different genotypes showed variable results. The effect of ToCV on plant development varied from 2.9% to 71.9% reduction, while yield loss varied from 0.2% to 51.8%. The highly ToCV‐resistant lineage IAC‐CN‐RT, which is also resistant to a Spanish isolate of ToCV, might be useful for tomato breeding programmes.  相似文献   

20.
A protocol for the specific detection and quantification of ‘Candidatus Liberibacter solanacearum’ in carrot seeds using real‐time PCR was developed. The bacterium was detected in 23 out of 54 carrot seed lots from 2010 to 2014, including seeds collected from diseased mother plants. The average total number of ‘Ca. L. solanacearum’ cells in individual seeds ranged from 4·8 ± 3·3 to 210 ± 6·7 cells per seed from three seed lots, but using propidium monoazide to target live cells, 95% of the cells in one seed lot were found to be dead. Liberibacter‐like cells were observed in the phloem sieve tubes of the seed coat and in the phloem of carrot leaf midrib from seedlings. The bacterium was detected as early as 30 days post‐germination, but more consistently after 90 days, in seedlings grown from PCR positive seed lots in an insect‐proof P2 level containment greenhouse. Between 12% and 42% of the seedlings from positive seed lots tested positive for ‘Ca. L. solanacearum’. After 150 days, symptoms of proliferation were observed in 12% of seedlings of cv. Maestro. ‘Candidatus Liberibacter solanacearum’ haplotype E was identified in the seeds and seedlings of cv. Maestro. No phytoplasmas were detected in seedlings with symptoms using a real‐time assay for universal detection of phytoplasmas. The results show that to prevent the entry and establishment of the bacterium in new areas and its potential spread to other crops, control of ‘Ca. L. solanacearum’ in seed lots is required.  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