Effectiveness of tailocins produced by Pseudomonas fluorescens SF4c in controlling the bacterial-spot disease in tomatoes caused by Xanthomonas vesicatoria (original) (raw)
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Antibacterial activity of some commercial bacteriotoxicants against tomato bacterial spot disease caused by the bacterium, Xanthomonas vesicatoria was screened in vitro and in vivo. Antagonistic effect of tested bacteriotoxicants i.e. Bio arc " Bacillus megaterium 2.5x10 7 CFU/g " (at conc. 1.5, 2.5 and 3.5 g/L), garlic oil (at conc. 0.3, 0.5 and 1.0%), oxytetracycline (at conc. 12.0, 12.5 and 13.0 µg/ml) and copper oxychloride (at conc. 1.0, 1.5, 2.0 g/L) was achieved. All tested treatments had clear significant inhibitory effects in vitro on growth of X. vesicatoria with increasing concentration of each bacteriotoxicant in comparing with control treatment. Maximum inhibitory effect was attained by copper oxychloride at 2.0 g/L (6.87 mm) followed by oxytetracycline at 13.0 µg/ml (4.70 mm), garlic oil at 1.0% (3.90 mm) and Bio arc at 3.5 g/L (2.83 mm). Applying of median concentration of each tested commercial bacteriotoxicant under open field condition individually in regular or in un-regular succession (in program form) as foliar spray considerably and significantly reduced bacterial spot disease development (disease % and disease severity %). Maximum reduction in disease development was achieved by applying prog-4 which served as treated control (sprayed with copper oxychloride) followed by prog-8 and prog-10, respectively. All tested treatments (programs) were significantly increased total tomato yield. Moreover, all tested programs increased clearly total phenol content, peroxidase, polyphenoloxidase and chitinase activity as well as, increased vitamin C content.
Rafidain Journal of Science
Two different plant extracts, thyme (Thymus vulgaris) and eucalyptus (Eucalyptus sp.), two bacterial strains, Pseudomonas fluorescens L18 and Bacillus subtilis K3, one antibiotic (Streptomycin) and one bactericide (copper sulphate) were tested for their control efficacy against Tomato Bacterial Spot caused by the bacterium Xanthomonas campestirs pv.vesicatoria under vitro and in vivo conditions. Two different concentrations of each extract was used, under lab and greenhouse conditions. The eucalyptus extract had better effect than the thyme extract in both conditions. The inhibition zone in Petri dishes was 11.25 mm and 6.99 mm and the reduction of disease severity index in plants was 40.7% and 35.6% respectively. The Pseudomonas fluorescens L18 strain had much better and was more effective than the Bacillus subtilis K3 strain in reduction the disease severity in plants. The disease severity index was reduced by 29.3% and 18.2% respectively. Streptomycin used as antibiotic had a great effect on reduction of the disease severity index 83.5% and inhibition zone 22.5mm. Copper sulphate reduced the disease severity index by 87% and had 38.1mm inhibition zone and had the best effect compared with other treatments.
Biocontrol of tomato bacterial spot by novel Bacillus and Pseudomonas strains
European Journal of Plant Pathology, 2021
Bacterial spot is a disease that affects tomato worldwide reducing its yield and quality. It is caused by different Xanthomonas spp., among which is Xanthomonas vesicatoria. Copper-based bactericides are generally used to control this disease, although nowadays sustainable strategies are being searched to efficiently replace their use. Our aim was to select native bacteria from tomato rhizosphere with biocontrol properties against X. vesicatoria. We selected, characterized, and identified three novel strains, two closely related to Bacillus velezensis (VMA11p and VM05) and one closely related to Pseudomonas soli (VMAP1), that in vitro antagonized X. vesicatoria. We evaluated the efficacy of the three rhizobacteria and their cell-free supernatants to control bacterial spot using the model tomato-X. vesicatoria in plants grown in pots, in greenhouse conditions. Bacterial suspensions of VMA11p and VMAP1, applied to the soil by irrigation, significantly (P < 0.05) reduced bacterial spot severity by 53.9% and 44.2%, respectively. Nevertheless, the most effective strategy to control bacterial spot was achieved using the cell-free supernatant produced by VMA11p, VM05 or VMAP1 applied as foliar spray, which significantly (P < 0.05) reduced the severity of the disease by 98.5%, 94.2% and 75.2%, respectively. None of the treatments reduced the growth of tomato plants. Our results suggest that the use of these novel strains of Bacillus and Pseudomonas and/or their metabolic products could be used for the development of biocontrol strategies for the management of bacterial spot in tomato.
Microbiological research, 2005
Following the relatively successful biological control of bacterial speck of tomato under Weld conditions at several locations (Phytopathology 92 , similar selection and testing strategies were employed in an eVort to isolate an eVective biological control agent for bacterial spot of tomato. Fifty potential biological control agents were isolated from tomato foliage in Alabama (AL) and Florida (FL) and tested under greenhouse conditions in AL for the ability to reduce the foliar severity of bacterial spot of tomato (Lycopersicon esculentum), which is caused by either Xanthomonas campestris pv. vesicatoria or Xanthomonas vesicatoria. Three pseudomonads that provided protection against bacterial speck also were included in the tests. The strains which were most eYcacious (i.e., high mean percentage reduction) and consistent (i.e., low standard deviation) in reducing bacterial spot severity in repeated greenhouse experiments were selected for Weld experiments conducted over the period 1996-1998. Among these strains were Cellulomonas turbata BT1, which provided the highest mean reduction in disease severity [45.2% (SD D 21.0)], and Pseudomonas syringae Cit7 [36.4% (SD D 12.2)], which was the most consistent. Field experiments were conducted in Shorter, AL; Bradenton and Sanford, FL; Clinton, North Carolina; Wooster, Ohio; and London, Ontario, Canada. The highest mean reductions in severity of bacterial spot on foliage, averaged across all locations, were provided by P. syringae Cit7 [28.9% (SD D 11.6)] and Pseudomonas putida B56 [23.1% (SD D 7.4)]. The eYcacy and consistency of P. syringae Cit7 against bacterial spot were very similar to those achieved against bacterial speck [28.3% (SD D 12.7)] (Phytopathology 92 ). Unfortunately, neither the bacterial strains nor the standard copper bactericides consistently reduced disease incidence on fruit. 2004 Elsevier Inc. All rights reserved.
Plant Disease, 2005
Two strains of plant growth-promoting rhizobacteria, two systemic acquired resistance inducers (harpin and acibenzolar-S-methyl), host-specific unformulated bacteriophages, and two antagonistic bacteria were evaluated for control of tomato bacterial spot incited by Xanthomonas campestris pv. vesicatoria in greenhouse experiments. Untreated plants and plants treated with copper hydroxide were used as controls. The plant growth-promoting rhizobacteria or a tap water control were applied as a drench to the potting mix containing the seedlings, while the other treatments were applied to the foliage using a handheld sprayer. The plant growth-promoting rhizobacteria strains, when applied alone or in combination with other treatments, had no significant effect on bacterial spot intensity. Messenger and the antagonistic bacterial strains, when applied alone, had negligible effects on disease intensity. Unformulated phage or copper bactericide applications were inconsistent in performance un...
American Journal of Agricultural and Biological Sciences, 2011
Problem statement: Phytopatogenic bacteria cause several damages to plants with important economical consequences. They provoke losses of product quality affecting all commercial chain of crops, for this reason, their control is a priority. Approach: We evaluated antagonist capacity of newly isolated Pseudonomas fluorescens strains against three important phytopatogenic bacteria (Clavibacter michiganensis, Xanthomonas axonopodis and Erwinia carotovora). Soils from commercial cropping of Capsicum annum L of several Mexican regions were used to isolate P. fluorescens strains. Results: Isolates producing flourescein were purified on King B agar and biochemically identified. Crude extracts with and without cells were produced in King B broths and their antagonist capacities were evaluated by the plate diffusion procedure on nutritive agar. Conclusion: Obtained results demonstrated that cell free extracts exhibited a limited antagonist capacity in comparison of those extracts with cells, which showed an excellent capacity to inhibit the growth of C. michiganensis, X. axonopodis and E. carotovora, demonstrating the intracellular nature of the bioactive metabolites associated to bacterial growth inhibition.
International Journal of Agriculture Sciences, 2017
Bacterial leaf spot caused by Xanthomonas campestris pv. viticola (Nayudu) Dye has emerged as an important disease in grape growing regions of Maharashtra. In this study the bactericidal effect of different chemicals and biological agents were assessed in in-vitro conditions. Eleven different commercially formulated chemicals (streptocycline, bronopol, mancozeb, copper sulphate, copper oxychloride, copper hydroxide, carbendazim, difenoconazole, validamycin, kasugamycin and potassium phosphite) were tested at 50, 100, 500, 1000, 2000 and 3000 ppm concentrations. Three biological agents viz., Bacillus subtilis, Trichoderma as perolloides and Pseudomonas fluorescens were also evaluated against X. campestris pv. viticola. Among different chemicals, streptocycline, mancozeb and bronopol showed significant inhibition of the pathogen while kasugamycin, copper oxychloride and copper hydroxide exhibited a low efficacy with respect to control of the bacteria. Copper sulphate, validamycin, difenoconazole, carbendazim and potassium phosphate showed no inhibition at all tested concentrations. In biological agents B. subtilis and T. asperolloides have potential against X. campestris pv. viticola, pathogen of bacterial leaf spot disease of grapes.
Isolation trials of bacteria associated to leaf spot collected from various locations in Egypt yielded 39 bacterial isolates. Following purification, the isolated bacteria were identified as Bacillus spp. (15 isolates), Pseudomonas spp. (12 isolates), and Xanthomonas campestris pv. vesicatoria "Xcv" (12 isolates). Both Bacillus spp. and Pseudomonas spp. had the higher frequency, being 38.46 and 30.77%, respectively than Xcv (30.77%). I1, I3, I4, I6, I9, I10, I11, and I12 had a low pathogenicity index exclusively on pepper plants. The antibacterial capabilities of five tested bacteriotoxicants were evaluated against Xcv in vitro. Copper oxychloride had the greatest increase in the inhibitory zone, followed by oxytetracycline then hydrogen peroxide, and clove oil treatments, being 6.32, 5.45, 5.14, and 4.52 mm, respectively. In vivo, all treatments examined outperformed the control treatment in terms of reducing bacterial leaf spot disease evaluation. All evaluated treatments increased total pepper production. Copper-treated control treatment resulted in the greatest increase in total fruit yield (23.68 kg/plot) during two successive growing seasons (2019/2020 and 2020/2021). The oxytetracycline, curcumin, clove oil, and hydrogen peroxide treatments all had a great effect on increasing total fruit yield. The investigated treatments enhanced total phenols content and oxidative enzymes activity in pepper leaves as compared to the treated-copper control and untreated control treatments. Curcumin, followed by clove oil and thenhydrogen peroxide, provided the greatest rise in the determined oxidative enzymes activities in leaves. In terms of vitamin-C increase percentage, all evaluated bacteriotoxicants enhanced vitamin-C content.
Strategies for Improving the Efficacy of Bacteriophages for Controlling Bacterial Spot of Tomato
2002
of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science STRATEGIES FOR IMPROVING THE EFFICACY OF BACTERIOPHAGES FOR CONTROLLING BACTERIAL SPOT OF TOMATO By Botond Balogh May 2002 Chairman: Dr. Jeffrey B. Jones Co-chairman: Dr. Timur M. Momol Major Department: Plant Pathology Bacterial spot, caused by the bacterium Xanthomonas campestris pv. vesicatoria, is one of the major tomato diseases in Florida. The disease is routinely controlled by the application of copper-mancozeb, a mixture of chemical pesticides; however, there is no adequate control measure when the environmental conditions are conducive for disease development. A novel method for controlling this disease is the application of a mixture of bacteriophages, viruses that infect bacteria. However, these control agents are rapidly degraded by harmful environmental factors such as sunlight or desiccation, which delimits the efficacy ...