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1.
Common bean seed lots collected from different seed dealers and Malawii agriculture station were screened for the presence of Xanthomonas axonopodis pv. phaseoli. In the laboratory the pathogen was isolated following the routine laboratory assay method, i.e. direct plating method using yeast extract-dextrose-calcium carbonate agar medium (YDC). Yellow, convex, mucoid colonies of Xanthomonas were consistently isolated on YDC from seed samples. The presumptive pathogen was confirmed by isolation on semiselective medium, such as mTBM and MD5A. Further, the pathogen was confirmed by biochemical, physiological and, finally, the pathogenicity tests. Five samples out of seven were positive for Xanthomonas. The isolates were found to cause common blight of 3-week-old common bean plants by 7 d after inoculation. Bacteria with the same characteristics as those inoculated were re-isolated from the infected plants.  相似文献   

2.
The objective of this study was to screen Streptomyces spp. for biological control of root and stem rot (Sclerotium rolfsii) and bacterial wilt (Ralstonia solanacearum), the very destructive diseases of chili pepper in Thailand. About 265 isolates of Streptomyces spp. were tested for their inhibitory effects on S. rolfsii mycelial growth on dual culture plates. Then, 14 promising isolates were further tested for their effects on R. solanacearum growth. Three effective isolates further identified as S. mycarofaciens SS-2-243, S.philanthi RL-1-178 and S. philanthi RM-1-138 were selected and proved to produce both antifungal and antibacterial substances in the culture medium. S. philanthi RM-1-138 strongly inhibited seed germination and seedling growth of chili pepper in laboratory tests. Therefore, it was not used in the following studies. When tested in greenhouse conditions, the efficacy of S. philanthi RL-1-178 in suppressing Sclerotium root and stem rot of chili pepper was approximately equal to that of Trichoderma harzianum NR-1-52 or that of carboxin treatment. S. mycarofaciens SS-2-243 and S. philanthi RL-1-178 suppressed Ralstonia wilt of chili pepper in a way that was similar to streptomycin sulfate treatment and it was observed that T. harzianum NR-1-52 had no effect on the bacterial wilt. Under field conditions where the soil was inoculated with two pathogens, the results showed that S. philanthi RL-1-178 could protect the chili pepper plants from S. rolfsii and R. solanacearum infection better than S. mycarofaciens SS-2-243 or T. harzianum NR-1-52. S. philanthi RL-1-178 treatment resulted in 58.75% survival of chili pepper plants and its efficacy was not significantly different from the carboxin-and-streptomycin sulfate treatment.  相似文献   

3.
Endophytic bacteria of eggplant, cucumber and groundnut were isolated from different locations of Goa, India. Based on in vitro screening, 28 bacterial isolates which effectively inhibited Ralstonia solanacearum, a bacterial wilt pathogen of the eggplant were characterized and identified. More than 50% of these isolates were Pseudomonas fluorescens in which a vast degree of variability was found to exist when biochemical characteristics were compared. In greenhouse experiments, the plants treated with Pseudomonas isolates (EB9, EB67), Enterobacter isolates (EB44, EB89) and Bacillus isolates (EC4, EC13) reduced the wilt incidence by more than 70%. All the selected isolates reduced damping off by more than 50% and improved the growth of seedlings in the nursery stage. Most of the selected antagonists produced an antibiotic, DAPG, which inhibited R. solanacearum under in vitro conditions and might have been responsible for reduced wilt incidence under in vivo conditions. Also production of siderophores and IAA in the culture medium by the antagonists was recorded, which could be involved in biocontrol and growth promotion in crop plants. From our study we conclude that Pseudomonas is the major antagonistic endophytic bacteria from eggplants which have the potential to be used as a biocontrol agent as well as plant growth-promoting rhizobacteria. Large scale field evaluation and detailed knowledge on antagonistic mechanism could provide an effective biocontrol solution for bacterial wilt of solanaceous crops.  相似文献   

4.
The presence of Burkholderia, Cupriavidus, and Ralstonia species in northeastern Mexico was investigated. An analysis of the root surrounding soil from different agricultural plants led to the isolation of Burkholderia and Cupriavidus species but no Ralstonia strains. Most Cupriavidus species were unknown and grouped into two clusters according to ARDRA profiles. The 16S rRNA sequence analysis showed that the Cupriavidus isolates were highly related among them and with different Cupriavidus species with validated names. However, SDS-PAGE profiles were distinct among the different ARDRA profiles and to other Cupriavidus species examined, suggesting new species in the genus. This shows that Cupriavidus is more widely associated with plants than previously appreciated. The BCC isolate was 99% similar to B. cenocepacia by recA sequence analysis. Additionally, most Cupriavidus strains from the two largest groups grew on media containing up to 0.1 mg/ml of copper, 10.0 mg/ml arsenic and 1.0 mg/ml zinc. Burkholderia strains grew on media containing up to 10.0 mg/ml zinc, 5.0 mg/ml arsenic and 0.1 mg/ml copper.  相似文献   

5.
In addition to antibiotic properties, medicinal plants are important sources of chemicals with potential application as pesticides. The present study deals with antitermitic potential of seed extracts of Withania somnifera (Indian ginseng), Croton tiglium (jamalgoota) and Hygrophila auriculata (talimkhana). The seed extracts caused changes in tunneling behaviour, number of bacterial colonies in hindgut and activities of enzymes in midgut of Odontotermes obesus. C. tiglium showed the lowest LT50 (12.85 and 2.65 h) among the three seed extracts at concentrations of 50% (half dilution of the extract) and 100% (extract without dilution), respectively. There was no tunneling in soil treated with 100% concentration of seed extracts of W. somnifera and C. tiglium. Numbers of bacterial colonies in the gut of termites from soils treated with 50% and 100% concentrations of the three plants did not differ significantly, but they differed from those in termites from untreated soil. At 50% concentrations of seed extracts of the tested plants, the difference in hindgut enzyme activities was not obvious, however, at 100% concentrations the enzyme activities in the termites from soils treated with seed extracts significantly differed from controls and differences were also recorded between the plants.  相似文献   

6.
Bacterial spot caused by Xanthomonas spp. is an important tomato and pepper disease worldwide. Recent outbreaks of bacterial spot disease in Central Brazil and Canada have been attributed to Xanthomonas gardneri, which is also recognized as group D of Xanthomonas campestris pv. vesicatoria. Carotenoid-like pigments called xanthomonadins, which are diagnostic for yellow Xanthomonas spp., were extracted from X. gardneri. It was shown that the model plant Arabidopsis thaliana, member of the Brassicaceae family, can develop disease symptoms in response to different isolates of X. gardneri. Secretion of enzymes has been shown to play an important role in pathogenicity for different pathogens, and to begin to understand the interaction of X. gardneri and A. thaliana, a biochemical analysis of secreted proteins in the presence of A. thaliana leaves was performed. Different enzymatic activities such as for cellulase, α-arabinofuranosidase, pectinase, invertase and xylanase were assayed. In the presence of leaves, cellulase activity was highest after 60 and 72 h of growth and α-arabinofuranosidase activity was detected between 12 and 72 h of growth. Pectinase, invertase and xylanase activities were not detected. Cellulase and α-arabinofuranosidase activities may be important for X. gardneri acquisition of plant nutrients through degradation of cellulose fibers and hemicellulose of the cell wall, respectively, to the invasion of the host tissue and/or may generate signal molecules that are recognized by the plant. This is the first study to address how X. gardneri responds to host plant tissue.  相似文献   

7.
The propagation of Givotia rottleriformis Griff. is difficult as a result of long seed dormancy associated with poor seed germination. The present study was undertaken to develop a protocol to overcome seed dormancy by culture of zygotic embryo axes and then develop an efficient method for micropropagation of Givotia. Best germination frequency (78.3%) was achieved from mature zygotic embryo axes isolated from acid-scarified fresh seeds when cultured on Murashige and Skoog (MS) medium (half-strength major salts) with 28.9 μM gibberellic acid (GA3). Efficient plant conversion was achieved by transfer of 10-d-old germinated embryos to MS medium (half-strength major salts) supplemented with 1.2 μM kinetin (KN) and 0.5 μM indole-3-butyric acid (IBA). However, acid scarification of 1-yr-old seeds decreased the germination frequency of zygotic embryo axes in comparison to those obtained from non-acid-scarified seeds which germinated (96.2%) and converted into plants (80.3%) on MS basal (half-strength major salts) medium. Multiple shoot bud induction was achieved by culture of shoot tips derived from in vitro germinated seedlings on MS medium with 0.5 μM thidiazuron for 4 wk, and the shoots elongated after transfer to a secondary medium with 1.2 μM KN. A maximum number of 7.8 shoots per explant with an average shoot length of 3.2 cm was achieved after two subcultures on this medium. The in vitro regenerated shoots rooted (41.5%) on half-strength MS medium with 0.5 μM IBA. The in vitro generated seedlings and micropropagated plants were established in soil with a survival frequency of 70% and 60%, respectively.  相似文献   

8.
Embryo-rescue was used to facilitate interspecific hybridization of Cucumis anguria L. and C. zeyheri Sond. Embryos were excised from developing fruits at one week intervals for six weeks after hand pollination. Medium containing coconut water was the most suitable for initial germination, and a medium with ascorbic acid was the best for embryo development and plant recovery. Viable plants were obtained from embryos and these plants showed morphological characteristics different from both parents. The analysis of the leucine aminopeptidase (LAP) locus revealed three hybrid types, H1.1, H1.2 and H2.  相似文献   

9.
10.
This study investigated the factors affecting in vitro flowering of Perilla frutescens. The shoots regenerated from cotyledonary and hypocotyl explants cultured on Murashige and Skoog (MS) medium supplemented with benzyladenine (BA) and indole-3-acetic acid, each at 0.5 mg l−1, were excised and transferred to MS medium containing 30 g l−1 of sucrose, 8.25 g l−1 of ammonium nitrate, and 1.0 mg l−1 of BA. After 40 d of culture, 86.2% of shoots flowered and most of which self-fertilized in vitro and produced mature fruits with viable seeds. These seeds were germinated and plants were grown to maturity and flowered in soil under greenhouse conditions. The in vitro flowering system reported in this study may facilitate rapid breeding of P. frutescens and offers a model system for studying the physiological mechanism of flowering.  相似文献   

11.
An efficient somatic embryogenesis system for Physalis pubescens L. (husk tomato) was developed prior to transformation. Subsequently, cotyledonary explants of P. pubescens were transformed with a chimeric construct containing an iaaM gene from driven by the fruit-specific promoter 2A12 to develop parthenocarpic fruits. Following selection of explants on Murashige and Skoog (MS) medium containing containing 75 mg l−1 kanamycin (Km), 36 km-resistant callus clusters were recovered, and these were regenerated into whole plants. Expression of the iaaM gene was detected in confirmed transgenic fruits. The 0.9-kb 2A12 promoter was capable of directing expression of the introduced iaaM gene in transgenic P. pubescens fruits, but iaaM expression was absent from both leaves and flowers. Quantitative measurements of indole-3-acetic acid (IAA) content during fruit development indicated that the IAA levels in transgenic lines increased from anthesis through young fruits and peaked at fruit maturity. On average, IAA contents in transgenic fruits were two-fold higher than those in control fruits. Under greenhouse condition, vegetative growth, morphology, and the flowering of transgenic plants were comparable to those of control plants. However, the fruits of transgenic lines ripened earlier and had fewer seeds per fruit than did control plants.  相似文献   

12.
In vitro culture is an important aid for ex situ conservation of rare, endemic or threatened plants. In this work, we establish an efficient method for the seed germination, seedling development, and axillary shoot propagation of Centaurea zeybekii Wagenitz. The seeds, collected from a wild population, were surface sterilised and cultured on various in vitro germination media. The effects of photoperiod and temperature on seed germination were also investigated. Germinations were obtained after 6 weeks in culture and the radicle emergence was evaluated as a main indicator. A high frequency of germination was obtained on distilled water supplemented with vitamines and 1 mg/L GA3. Although the seed germination frequencies were not affected by photoperiod, the highest germination frequency was obtained at 24 ± 2°C. A high frequency of axillary shoot proliferation was produced on MS medium supplemented with 1 mg/L BA. Then, the axillary shoots were separated and transferred to MS medium with or without plant growth regulators for rooting. Rhizogenezis was promoted after 6 weeks only in MS and 1/2 MS media containing 0.5 mg/L IBA. The rooting process was very slow and the percentage of shoot rooting was also very low (15%). The present study not only enables reinforcement of wild plant populations using ex situ growth of individuals, but it also helps to large number of aseptic seedling to use it in clonaly micropropagation studies.  相似文献   

13.
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   

14.
Six pea (Pisum sativum L.) cultivars (Adept, Komet, Lantra, Olivin, Oskar, Tyrkys) were transformed via Agrobacterium tumefaciens strain EHA105 with pBIN19 plasmid carrying reporter uidA (β-glucuronidase, GUS, containing potato ST-LS1 intron) gene under the CaMV 35S promoter, and selectable marker gene nptII (neomycin phosphotransferase II) under the nos promoter. Two regeneration systems were used: continual shoot proliferation from axillary buds of cotyledonary node in vitro, and in vivo plant regeneration from imbibed germinating seed with removed testa and one cotyledon. The penetration of Agrobacterium into explants during co-cultivation was supported by sonication or vacuum infiltration treatment. The selection of putative transformants in both regeneration systems carried out on media with 100 mg dm−3 kanamycin. The presence of introduced genes was verified histochemically (GUS assay) and by means of PCR and Southern blot analysis in T0 putative transformants and their seed progenies (T1 to T3 generations). Both methods, but largely in vivo approach showed to be genotype independent, resulting in efficient and reliable transformation system for pea. The in vivo approach has in addition also benefit of time and money saving, since transgenic plants are obtained in much shorter time. All tested T0 – T3 plants were morphologically normal and fertile.This research was supported by the National Agency for Agricultural Research (grants No. QE 0046 and QF 3072) and Ministry of Education of the Czech Republic (grant No. ME 433).  相似文献   

15.
Interspecies fusants are formed between Agaricus bisporus and Agaricus bitorquis by protoplast fusion technique. Protoplasts were isolated and regenerated by using Novozyme 234 lytic enzyme. Twenty slow growing isolates were separated from the protoplast regenerated colonies, which were assumed as homokaryons (putative homokaryons). These twenty isolates were subjected to growth rate, colony morphology and spawn run studies for screening of true homokaryons. Antifungal markers were developed for selection of fusants.  相似文献   

16.
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   

17.
Sunflower (Helianthus annuus) stem canker caused by Diaporthe helianthi is one of the most important sunflower diseases in Croatia. Until recently, sunflower was the only known host for D. helianthi. In our research carried out in the area of Eastern Croatia, isolates of Diaporthe/Phomospis were collected from Xanthium italicum, X. strumarium and Arctium lappa. Using morphological, cultural and molecular ITS rDNA data, isolates from these weeds were identified as D. helianthi. The following isolates were used in the pathogenicity test: one isolate originated from sunflower (Su5/04), three from X. italicum (Xa2, Xa3 and Xa5), two from X. strumarium (Xa9 and Xa12), one from Xanthium sp. (Xa13) and one from A. lappa (Ar3). According to the results, it was determined that isolate Xa5 (originated from X. italicum) was the most pathogenic to sunflower stems. The average length of the lesion was 11.3 cm. The lowest level of pathogenicity was found in Xa9 (isolated from X. strumarium). The length of the lesion was 0.1 cm.  相似文献   

18.
A Sebacinales species was recovered from a clone library made from a pooled rhizosphere sample of Nicotiana attenuata plants from 14 native populations. Axenic cultures of the related species, Piriformospora indica and Sebacina vermifera, were used to examine their effects on plant performance. Inoculation of N. attenuata seeds with either fungus species stimulated seed germination and increased growth and stalk elongation. S. vermifera inoculated plants flowered earlier, produced more flowers and matured more seed capsules than did non-inoculated plants. Jasmonate treatment during rosette-stage growth, which slows growth and elicits herbivore resistance traits, erased differences in vegetative, but not reproductive performance resulting from S. vermifera inoculation. Total nitrogen and phosphorous contents did not differ between inoculated and control plants, suggesting that the performance benefits of fungal inoculation did not result from improvements in nutritional status. Since the expression of trypsin proteinase inhibitors (TPI), defensive proteins which confer resistance to attack from Manduca sexta larvae, incur significant growth and fitness costs for the plant, we examined the effect of S. vermifera inoculation on herbivore resistance and TPI activity. After 10 days of feeding on S. vermifera-inoculated plants, larval mass was 46% higher and TPI activity was 48% lower than that on non-inoculated plants. These results suggest that Sebacina spp. may interfere with defense signaling and allow plants to increase growth rates at the expense of herbivore resistance mediated by TPIs.  相似文献   

19.
The aim of this study was to assess the diagnostic properties of the two selective plating media and a chromogenic medium for identification of Bacillus cereus. The 324 isolates were B. cereus (37%), Bacillus weihenstephanensis (45%) or Bacillus thuringiensis (18%), as identified by a new combination of techniques. All isolates were growing on mannitol–egg yolk–polymyxin agar (MYP), and they did not form acid from mannitol. However, a significant lower number of B. thuringiensis isolates did not show lecithinase activity. All isolates were also growing on polymyxin–egg yolk–mannitol–bromothymol blue agar (PEMBA); however, 11% isolates indicated that they did produce acid from mannitol, and 15% isolates did not show any lecithinase activity. Five of the isolates did not grow at all on the chromogenic agar, and 14 of the growing isolates were β-glucosidase negative. It is concluded that the two recommended selective plating media MYP and PEMBA for detection of B. cereus group bacteria both have their limitations for identification of some B. cereus, B. weihenstephanensis or B. thuringiensis. However, MYP is preferable compared to PEMBA. The chromogenic medium has its own advantages and limitations, and some of the limitations seem to be solved by incubation at 30°C instead of the recommended 37°C.  相似文献   

20.
Summary We describe an in vitro propagation protocol for Zingiber petiolatum (Holttum), I. Theilade, a rare species from the southern part of Thailand. Fruits were surface-sterilized and seeds germinated on Murashige and Skoog medium (MS) medium supplemented with 3% sucrose. Three-month-old seedlings were used as initial plant material for in vitro propagation. Terminal buds of the plants were inoculated on MS medium containing 6-benzylaminopurine (BA; 2.2–35.5 μM) alone or in combination with 1-naphthaleneacetic acid (0.5 μM). Eight weeks after inoculation, the cultures were transferred to MS medium without plant growth regulators for 4wk. The cultures transferred from MS medium with 17.8 μM BA revealed the highest shoot induction rate of 6.1±0.7 shoots per explant. Rooting was spontaneously achieved in MS medium without plant growth regulators. Rooted plants were successfully transplanted to soil.  相似文献   

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