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1.
Streptomyces is a genus known for its ability to protect plants against many pathogens and various strains of this bacteria have been used as biological control agents. In this study, the efficacy of Streptomyces philanthi RM-1-138, S. philanthi RL-1-178, and Streptomyce mycarofaciens SS-2-243 to control various strains of Botrytis cinerea was evaluated both in vitro and in vivo. In vitro studies using confrontation tests on PDA plates indicated that the three strains of Streptomyces spp. inhibited the growth of 41 strains of B. cinerea. Volatile compounds produced by Streptomyces spp. had an influence on the growth of ten strains of B. cinerea while its culture filtrate at low concentration (diluted at 10?3) showed a complete inhibition (100%) of spore germination of B. cinerea strain BC1. A significant protection efficacy of tomato against B. cinerea was observed on both whole plant test (57.4%) and detached leaf test (60.1%) with S. philanti RM-1-138. Moreover, this antagonistic strain had a preventive and a curative effect. These results indicated that S. philanthi RM-1-138 may have the potential to control gray mold caused by B. cinerea on tomato but further work is required to enhance its efficacy and its survival in planta.  相似文献   

2.
The compatibility of two biological inoculants, Trichoderma harzianum, a mycoparasitic biological control fungus and Piriformospora indica, a root colonizing plant-growth promoting endophytic fungus was evaluated using tissue cultured black pepper plantlets. We report, for the first time, the ability of P. indica to colonize black pepper, a perennial climber. T. harzianum inhibited the growth of P. indica in an in vitro dual culture plate assay. Simultaneous inoculation with both biological inoculants of tissue cultured black pepper plantlets negatively influenced root colonization by P. indica. However, when P. indica was applied initially followed 30 days later by T. harzianum, there was increased root colonization by the root endophyte P. indica and beneficial effects were found on the growth of the black pepper plants. The present study also showed that the efficacy of inoculation of the two fungal biological agents can be increased by sequential application of P. indica at the hardening stage followed by T. harzianum during transplanting into a soil-sand mixture.  相似文献   

3.
Biological control of wilt of egg plant (Solanum melongena L.) caused by Fusarium solani was made with the application of five Trichoderma species, T. harzianum, T. viride, T. lignorum, T. hamatum and T. reesei. The effect of volatile and non-volatile antibiotics of Trichoderma origin on growth inhibition of the wilt pathogen was studied. T. harzianum showed maximum growth inhibition (86.44 %) of the pathogen through mycoparasitism. The non-volatiles produced by the Trichoderma species exhibited 100 % growth inhibition of the pathogen under in vitro condition. Production of siderophores and fungal cell wall degrading enzymes, chitinase and β-1,3-glucanase were found. Treatments with two most efficient Trichoderma species, T. harzianum and T. viride resulted in the decreasing population of Fusarium solani in soil thereby deterring disease incidence in field condition.  相似文献   

4.

Background  

There is no dedicated database available for Expressed Sequence Tags (EST) of the chili pepper (Capsicum annuum), although the interest in a chili pepper EST database is increasing internationally due to the nutritional, economic, and pharmaceutical value of the plant. Recent advances in high-throughput sequencing of the ESTs of chili pepper cv. Bukang have produced hundreds of thousands of complementary DNA (cDNA) sequences. Therefore, a chili pepper EST database was designed and constructed to enable comprehensive analysis of chili pepper gene expression in response to biotic and abiotic stresses.  相似文献   

5.
Recent studies have revealed several examples of intimate associations between insects and Actinobacteria, including the Southern Pine Beetle Dendroctonus frontalis and the Spruce Beetle Dendroctonus rufipennis. Here, we surveyed Streptomyces Actinobacteria co-occurring with 10 species of Dendroctonus bark beetles across the United States, using both phylogenetic and community ecology approaches. From these 10 species, and 19 other scolytine beetles that occur in the same trees, we obtained 154 Streptomyces-like isolates and generated 16S sequences from 134 of those. Confirmed 16S sequences of Streptomyces were binned into 36 distinct strains using a threshold of 0.2% sequence divergence. The 16S rDNA phylogeny of all isolates does not correlate with the distribution of strains among beetle species, localities, or parts of the beetles or their galleries. However, we identified three Streptomyces strains occurring repeatedly on Dendroctonus beetles and in their galleries. Identity of these isolates was corroborated using a house-keeping gene sequence (efTu). These strains are not confined to a certain species of beetle, locality, or part of the beetle or their galleries. However, their role as residents in the woodboring insect niche is supported by the repeated association of their 16S and efTu from across the continent, and also having been reported in studies of other subcortical insects.  相似文献   

6.
Tomato (Lycopersicon esculentum) is important widely grown vegetable in India and its productivity is affected by bacterial wilt disease infection caused by Ralstonia solanacearum. To prevent this disease infection a study was conducted to isolate and screen effective plant growth promoting rhizobacteria (PGPR) antagonistic to R. solanacearum. A total 297 antagonistic bacteria were isolated through dual culture inoculation technique, out of which forty-two antagonistic bacteria were found positive for phlD gene by PCR amplification using two primer sets Phl2a:Phl2b and B2BF:BPR4. The genetic diversity of phlD + bacteria was studied by amplified 16S rDNA restriction analysis and demonstrated eleven groups at 65% similarity level. Out of these 42 phlD + antagonistic isolates, twenty exhibited significantly fair plant growth promoting activities like phosphate solubilization (0.92–5.33%), 25 produced indole acetic acid (1.63–7.78 μg ml−1) and few strains show production of antifungal metabolites (HCN and siderophore). The screening of PGPR (phlD +) for suppression of bacterial wilt disease in glass house conditions was showed ten isolated phlD + bacteria were able to suppress infection of bacterial wilt disease in tomato plant (var. Arka vikas) in the presence R. solanacearum. The PGPR (phlD +) isolates s188, s215 and s288 was observed to be effective plant growth promoter as it shows highest dry weight per plant (3.86, 3.85 and 3.69 g plant−1 respectively). The complete absence of wilt disease symptoms in tomato crop plants was observed by these treatments compared to negative control. Therefore inoculation of tomato plant with phlD + isolate s188 and other similar biocontrol agents may prove to be a positive strategy for checking wilt disease and thus improving plant vigor.  相似文献   

7.
This paper discusses a number of experiments performed, involving the fusion by an electric field of mesophyll protoplasts from Solanum tuberosum cv. Bintje, S. tuberosum dihaploid clones 243, 299 and the wild tuberous disease-resistant species S. bulbocastanum and S. pinnatisectum. Three fusion experiments (S. bulbocastanum + S. tuberosum dihaploid 243, S. pinnatisectum + S. tuberosum cv. Bintje and S. pinnatisectum + S. tuberosum dihaploid 299) yielded 542 calli, the 52 ones of which produced shoots. Obtained regenerants were estimated by the flow-cytometry (FC) and RAPD analysis to determine hybrid plants.The utilisation of the FC as a useful method for detecting somatic hybrids is also discussed in this paper. The combination S. bulbocastanum + S. tuberosum dihaploid 243 led to the creation of eight somatic hybrids, the combination S. pinnatisectum + S. tuberosum cv. Bintje yielded four somatic hybrids and the combination S. pinnatisectum + S. tuberosum dihaploid 299 resulted in no hybrid regenerants. Morphology in vitro, growth vigour and production of tuber-like structures were evaluated in hybrid plants. Plants were transferred in vivo for further estimation (acclimatization, habitus evaluation and tuberization ability).  相似文献   

8.
Capsaicinoids are responsible for the pungent taste of chili pepper fruits of Capsicum species. Capsaicinoids are biosynthesized through both the phenylpropanoid and the branched-fatty acids pathways. Fragments of Comt (encoding a caffeic acid O-methyltransferase), pAmt (a putative aminotransferase), and Kas (a β-keto-acyl-[acyl-carrier-protein] synthase) genes, that are differentially expressed in placenta tissue of pungent chili pepper, were individually inserted into a Pepper huasteco yellow veins virus (PHYVV)-derived vector to determine, by virus-induced gene silencing, irrespective of whether these genes are involved in the biosynthesis of capsaicinoids. Reduction of the respective mRNA levels as well as the presence of related siRNAs confirmed the silencing of these three genes. Morphological alterations were evident in plants inoculated with PHYVV::Comt and PHYVV::Kas constructs; however, plants inoculated with PHYVV::pAmt showed no evident alterations. On the other hand, fruit setting was normal in all cases. Biochemical analysis of placenta tissues showed that, indeed, independent silencing of all three genes led to a dramatic reduction in capsaicinoid content in the fruits demonstrating the participation of these genes in capsaicinoid biosynthesis. Using this approach it was possible to generate non-pungent chili peppers at high efficiency.  相似文献   

9.
Rice brown spot, caused by Bipolaris oryzae, can be a serious disease causing a considerable yield loss. Trichoderma harzianum is an effective biocontrol agent for a number of plant fungal diseases. Thus, this research was carried out to investigate the mechanisms of action by which T. harzianum antagonizes Bipolaris oryzae in vitro, and the efficacy of spray application of a spore suspension of T. harzianum for control of rice brown spot disease under field conditions. In vitro, the antagonistic behavior of T. harzianum resulted in the overgrowth of B. oryzae by T. harzianum, while the␣antifungal metabolites of T.␣harzianum completely prevented the linear growth of B. oryzae. Light and scanning electron microscope (SEM) observations showed no evidence that mycoparasitism contributed to the aggressive nature of the tested isolate of T. harzianum against B. oryzae. Under field conditions, spraying of a spore suspension of T. harzianum at 108 spore ml−1 significantly reduced the disease severity (DS) and disease incidence (DI) on the plant leaves, and also significantly increased the grain yield, total grain carbohydrate, and protein, and led to a significant increase in the total photosynthetic pigments (chlorophyll a and b and carotenoids) in rice leaves.  相似文献   

10.
Cytoplasmic male sterility (CMS) in plants is known to be associated with novel open reading frames (ORFs) that result from recombination events in the mitochondrial genome. In this study Southern and Northern blot analyses using several mitochondrial DNA probes were conducted to detect the presence of differing band patterns between male fertile and CMS lines of chili pepper (Capsicum annuum L.). In the CMS pepper, a novel ORF, termed orf456, was found at the 3′-end of the coxII gene. Western blot analysis revealed the expression of an approximately 17-kDa product in the CMS line, and the intensity of expression of this protein was severely reduced in the restorer pepper line. To investigate the functional role of the ORF456 protein in plant mitochondria, we carried out two independent experiments to transform Arabidopsis with a mitochondrion-targeted orf456 gene construct by Agrobacterium-mediated transformation. About 45% of the T1 transgenic population showed the male-sterile phenotype and no seed set. Pollen grains from semi-sterile T1 plants were observed to have defects on the exine layer and vacuolated pollen phenotypes. It is concluded that this newly discovered orf456 may represent a strong candidate gene – from among the many CMS-associated mitochondrial genes – for determining the male-sterile phenotype of CMS in chili pepper. GenBank accession number DQ116040 (orf456 genomic sequence), DQ126683 (pepper coxII genomic sequence)  相似文献   

11.
12.
Two non-conventional chemicals, ZnSO4 (10−4 mM) and oxalic acid (4 mM) were tested (alone as well as in combination with seeds bacterized with Pseudomonas syringae strain PUR46 and vermicompost substitution in the potting soil), for their ability to suppress collar rot of chickpea (Cicer arietinum) caused by Sclerotium rolfsii under greenhouse conditions. ZnSO4 and oxalic acid were applied as pre-inoculation foliar spray on chickpea and subsequently challenged with S. rolfsii. Both the chemicals provided significant protection to chickpea compared to control (100% plant mortality) when used alone as well as in combination with PUR46 and vermicompost. However, ZnSO4 was more effective than oxalic acid against S. rolfsii. Amongst the treatments tried, plant mortality was least when ZnSO4 was used in combination with seed bacterization with PUR46 and 25% vermicompost substitution. The findings indicate the utility of integration of the above factors in managing collar rot efficiently.  相似文献   

13.
To enhance bacterial wilt resistance in tomato plants and simplify the protocol of Agrobacterium tumefaciens mediated gene transfer, parameters affecting transformation efficiency in tomato have been optimized. A. tumefaciens strain EHA101, harboring a recombinant binary expression vector pTCL5 containing the Xa21 gene under the control of the CaMV 35S promoter was used for transformation. Five cultivars of tomato (Rio Grande, Roma, Pusa Ruby Pant Bahr and Avinash) were tested for transformation. Transformation efficiency was highly dependent on preculture of the explants with acetosyringone, acetosyringone in co-cultivation media, shoot regeneration medium and pre-selection after co-cultivation without selective agent. One week of pre-selection following selection along with 400 μM acetosyringone resulted in 92.3% transient GUS expression efficiency in Rio Grande followed by 90.3% in Avinash. The presence and integration of the Xa21 gene in putative transgenic plants was confirmed by polymerase chain reaction (PCR) and Southern blot analyses with 4.5–42.12% PCR-positive shoots were obtained for Xa21 and hygromycin genes, respectively. Transgenic plants of the all lines showed resistance to bacterial wilt. T1 plants (resulting from self-pollination of transgenic plants) tested against Pseudomonas solanacearum inoculation in glasshouse, showed Mendelian segregation.  相似文献   

14.
This study was undertaken to explore the role of Trichoderma sp. in phosphate (P) solubilization and antagonism against fungal phytopathogens. All fungal isolates (SE6, KT6, KT28, and BRT11) and a standard culture of T. harzianum (Th-std) were able to antagonize two fungal phytopathogens (Sclerotium rolfsii and Rhizoctonia solani) of chickpea (Cicer arietinum L.) wilt complex. Transmission electron microscopic studies (TEM) further confirmed ultra-cytological changes in the sclerotia of S. rolfsii parasitized by Trichoderma sp. All fungal cultures exhibited production of NH3 and siderophore, but only BRT11, SE6, and Th-std could produce HCN. Among all the cultures tested, isolate KT6 was found to be most effective for solubilization of ferric phosphate releasing 398.4 μg ml−1 phosphate while isolates BRT11 and SE6 showed more potential for tricalcium phosphate (TCP) solubilization releasing 449.05 and 412.64 μg ml−1 phosphate, respectively, in their culture filtrates. Part of this study focused on the influence of abiotic stress conditions such as pH, temperature, and heavy metal (cadmium) on phosphate (TCP) solubilizing efficiency. Two selected cultures KT6 and T. harzianum retained their P solubilizing potential at varying concentrations of cadmium (0–1000 μg ml−1). Isolate KT6 and standard culture of T. harzianum released 278.4 and 287.6 μg ml−1 phosphate, respectively, at 1000 μg ml−1cadmium. Maximum solubilization of TCP was obtained at alkaline pH and at 28°C temperature. Isolate BRT11 was found most alkalo-tolerant releasing 448.0 μg ml−1 phosphate at pH 9.  相似文献   

15.
A Streptomyces strain, NT0401, was isolated from soil that selectively inhibited Microcystis strains but did not affect other microorganisms. Based on its morphology, physiology and 16S rDNA sequence, it was identified as Streptomyces grisovariabilis. The active substance produced by NT0401 was a water-soluble compound with a Mr <1 kDa that was stable over a broad pH range and at 100°C for 20 min. This organism should be a potential environment-friendly strain for control of Microcystis blooms.  相似文献   

16.
In this report, the diversity of Actinobacteria associated with the marine sponge Hymeniacidon perleve collected from a remote island of the South China Sea was investigated employing classical cultivation and characterization, 16S rDNA library construction, 16S rDNA-restriction fragment length polymorphism (rDNA-RFLP) and phylogenetic analysis. A total of 184 strains were isolated using seven different media and 24 isolates were selected according to their morphological characteristics for phylogenetic analysis on the basis of their 16S rRNA gene sequences. Results showed that the 24 isolates were assigned to six genera including Salinispora, Gordonia, Mycobacterium, Nocardia, Rhodococcus and Streptomyces. This is the first report that Salinispora is present in a marine sponge from the South China Sea. Subsequently, 26 rDNA clones were selected from 191 clones in an Actinobacteria-specific 16S rDNA library of the H. perleve sample, using the RFLP technique for sequencing and phylogenetic analysis. In total, 26 phylotypes were clustered in eight known genera of Actinobacteria including Mycobacterium, Amycolatopsis, Arthrobacter, Brevibacterium, Microlunatus, Nocardioides, Pseudonocardia and Streptomyces. This study contributes to our understanding of actinobacterial diversity in the marine sponge H. perleve from the South China Sea.  相似文献   

17.
Phytophthora drechsleri damping-off is one of the most important diseases of cucumber (Cucumis sativus). Salinity is a serious problem for crop production and affects diversity and activity of soil microorganisms. Application of salt-tolerant biocontrol agents may be beneficial in order to protect plants against pathogenic fungi in saline soils. In this study, a total of 717 Streptomyces isolates were isolated from the rhizosphere of cucumber, out of which two isolates showed more than 70% inhibitory effect against P. drechsleri and had cellulase activity in the presence and absence of NaCl. In a greenhouse experiment, two Streptomyces isolates with the highest antagonistic activity, strains C 201 and C 801, reduced seedling damping-off of cucumber caused by P. drechsleri by 77 and 80%, respectively, in artificially infested soils. Strain C 201 increased dry weight of seedlings up to 21% in greenhouse experiments. Phylogenetic analyses of 16S rRNA gene sequence reveals that strains C 201 and C 801 are closely related to S. rimosus and S. monomycini respectively. Increased activity of polyphenol oxidase (PPO) and peroxidase (POX) enzymes in Streptomyces-treated plants proved the biocontrol-induced systemic resistance (ISR) in cucumber plants against P. drechsleri.  相似文献   

18.

Aims

To identify Rhizobium strains’ ability to biocontrol Sclerotium rolfsii, a fungus that causes serious damage to the common bean and other important crops, 78 previously isolated rhizobia from common bean were assessed.

Methods

Dual cultures, volatiles, indole-acetic acid (IAA), siderophore production and 16S rRNA sequencing were employed to select strains for pot and field experiments.

Results

Thirty-three antagonistic strains were detected in dual cultures, 16 of which were able to inhibit ≥84% fungus mycelial growth. Antagonistic strains produced up to 36.5 μg mL?1 of IAA, and a direct correlation was verified between IAA production and mycelium inhibition. SEMIA 460 inhibited 45% of mycelial growth through volatile compounds. 16S rRNA sequences confirmed strains as Rhizobium species. In pot condition, common bean plants grown on S. rolfsii-infested soil and inoculated with SEMIA 4032, 4077, 4088, 4080, 4085, or 439 presented less or no disease symptoms. The most efficient strains under field conditions, SEMIA 439 and 4088, decreased disease incidence by 18.3 and 14.5% of the S. rolfsii-infested control.

Conclusions

Rhizobium strains could be strong antagonists towards S. rolfsii growth. SEMIA 4032, 4077, 4088, 4080, 4085, and 439 are effective in the biological control of the collar rot of the common bean.
  相似文献   

19.
Chili pepper (Capsicum annum L.) is an important economic crop that is severely destroyed by the filamentous oomycete Phytophthora capsici. Little is known about this pathogen in key chili pepper farms in Punjab province, Pakistan. We investigated the genetic diversity of P. capsici strains using standard taxonomic and molecular tools, and characterized their colony growth patterns as well as their disease severity on chili pepper plants under the greenhouse conditions. Phylogenetic analysis based on ribosomal DNA (rDNA), β-tubulin and translation elongation factor 1α loci revealed divergent evolution in the population structure of P. capsici isolates. The mean oospore diameter of mating type A1 isolates was greater than that of mating type A2 isolates. We provide first evidence of an uneven distribution of highly virulent mating type A1 and A2 of P. capsici that are insensitive to mefenoxam, pyrimorph, dimethomorph, and azoxystrobin fungicides, and represent a risk factor that could ease outpacing the current P. capsici management strategies.  相似文献   

20.
Verticillium wilt (Verticillium dahliae) is an economically important disease for many high-value crops. The pathogen is difficult to manage due to the long viability of its resting structures, wide host range, and the inability of fungicides to affect the pathogen once in the plant vascular system. In chile pepper (Capsicum annuum), breeding for resistance to Verticillium wilt is especially challenging due to the limited resistance sources. The dominant Ve locus in tomato (Solanum lycopersicum) contains two closely linked and inversely oriented genes, Ve1 and Ve2. Homologs of Ve1 have been characterized in diverse plant species, and interfamily transfer of Ve1 confers race-specific resistance. Queries in the chile pepper WGS database in NCBI with Ve1 and Ve2 sequences identified one open reading frame (ORF) with homology to the tomato Ve genes. Comparison of the candidate CaVe (Capsicum annuum Ve) gene sequences from susceptible and resistant accessions revealed 16 single nucleotide polymorphisms (SNPs) and several haplotypes. A homozygous haplotype was identified for the susceptible accessions and for resistant accessions. We developed a cleaved amplified polymorphic sequence (CAPS) molecular marker within the coding region of CaVe and screened diverse germplasm that has been previously reported as being resistant to Verticillium wilt in other regions. Based on our phenotyping using the New Mexico V. dahliae isolate, the marker could select resistance accessions with 48% accuracy. This molecular marker is a promising tool towards marker-assisted selection for Verticillium wilt resistance and has the potential to improve the efficacy of chile pepper breeding programs, but does not eliminate the need for a bioassay. Furthermore, this work provides a basis for future research in this important pathosystem.  相似文献   

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