Pseudomonas Fluorescens Isolates Research Articles

The Addition of Several Mineral Sources on Growing Media of Fluorescent Pseudomonad for the Biosynthesis of Hydrogen Cyanide

All Fluorescent pseudomonad is a group of rhyzobacteria which these days often utilized on plant disease control. The growing media is an absolute requirement which needs to be considered for the growth and cultivation of bacteria. The mineral source contained in growing media of bacteria may affect the production of hydrogen cyanide compound. The objectives of the research were to obtain the best source of minerals for biosynthesis of cyanide acid compounds by fluorescent pseudomonad isolates PfPj1, PfPb1, PfPj2, Kd7, Cas, Cas3, and LAHp2. This research is a qualitative experimental research including observation of hydrogen cyanide compound produced after the growing media of fluorescent pseudomonad bacteria added with several mineral sources. The treatments were given: A = ZnSO4.7H2O 0.5 mM addition, B = CoCl2.6H2O 0.5 mM addition, and C = Fe2SO4.7H2O 0.5 mM addition. From the result of the research, it was concluded that the addition of ZnSO4.7H2O mineral resources on the growing media of fluorescent pseudomonad isolate Cas and Cas3 produced the best hydrogen cyanide. Whereas addition of CoCl2.6H2O mineral source on the growing media showed poor hydrogen cyanide production for all fluorescent pseudomonad isolates

Enhancing total lipid and stearidonic acid yields in Buglossoides arvensis through PGPR inoculation.

This study was performed to identify bacterial isolates capable of enhancing total lipid and stearidonic acid (SDA) yields in Buglossoides arvensis. Pot experiments were conducted to screen the effects of 40 bacterial isolates on different B. arvensis growth parameters. Five isolates increased total lipid and SDA yields by at least 20%. These isolates were tested in a second pot experiment and in field trials. The second pot experiment confirmed that all isolates significantly increased total lipid and SDA yields over controls. Plants inoculated with four bacterial strains experienced significantly higher shoot weights, however, the increase in shoot weight decreased over time. Three isolates led to higher total seed numbers. In field trials, the inoculations had no significant effect on seed or lipid yields. However, isolate Pseudomonas fluorescens LBUM677 significantly increased SDA yield by 33% as compared to control plants. This strain was also the most efficient biofilm producer. Pseudomonas fluorescens LBUM677 can significantly increase SDA yield in B. arvensis under controlled and field conditions. Using bacterial strains to increase plant yield is of great interest under commercial settings. Pseudomonas fluorescens LBUM677 shows promise to promote SDA accumulation in B. arvensis under production conditions.

Ecological applications of Pseudomonas as a biopesticide to control two-spotted mite Tetranychus urticae: chitinase and HCN production

Abstract The two-spotted spider mite (Tetranychus urticae Koch) is an important pest of many horticultural crops. A study was conducted to evaluate the effect of three fluorescent Pseudomonas isolates obtained from rhizospheric soil of tomato (Solanum lycopersicon) in Agadir, Morocco: Q110B, Q036B and Q172B, as potential biological control agents for T. urticae. Both acaricide and repellent activities were assessed on homogenous adult mites. The acaricidal activity test evaluated five concentrations of bacterial suspensions: 0 (control), 102, 104, 106, 108, and 1010 cfu · ml−1, while only the 1010 cfu ∙ ml−1 concentration of each bacterium was used for the repellent bioassay. The mortality rate and repellentindex were recorded 24, 48 and 72 h after application. Results indicated that the survival rate of T. urticae was reduced (p ≤ 0.01) by all three bacterial isolates compared to control. Within the 24–72 h time period the mortality rates ranged from 8 to 87%, 16 to 99%, and 13 to 89%, for Q110B, Q036B and Q172B isolates, respectively. The isolate Q036B (LC50 = 0.598 cfu · ml−1) provided higher mortality rates than Q172B and Q110B with LC50 values of 90,846 and 169,585 cfu · ml−1, respectively. Repellent activity was also the highest with Pseudomonas Q036B having a 71% repellence index at 48 h after application. Regarding the mechanism of action, all three isolates produced hydrogen cyanide, and exhibited protease and cellulose activities, although only Q036B and Q172B had potential chitinase action. Identification analysis showed that the isolates were either Pseudomonas putida (Q172B) or P. fluorescens (Q110B and Q036B). Our results indicate that the P. fluorescens isolate Q036B is a promising candidate for biological control of T. urticae, and has potential to contribute to an integrated pest management program to control this important pest. Then the fruits produced will be qualified as safe for consumers and the environment. The present work was customized to give support for policy decision makers as an agroecological potential meeting needs of industries and ecological balance.

Characterization of phosphate solubilizing fluorescent pseudomonads from the rhizosphere of Aloe vera (L.)

ABSTRACTSoil phosphorous (P) deficiency is a major constraint to plant production which is overcome by adding inorganic-phosphate as chemical fertilizers. Fluorescent pseudomonads are the diverse group of bacteria able to mobilize sparingly soluble phosphate form. Total three hundred seven fluorescent Pseudomonas isolates were obtained from the Aloe barbadensis (Miller) rhizosphere. These Pseudomonas strains were further evaluated in vitro for their ability to solubilize phosphate and to produce indole acetic acid (IAA), hydrogen cyanide (HCN), siderophore and 1-aminocyclopropane 1- carboxylate (ACC) deaminase. Fifty three (36.8%) isolates produced IAA and 52 (36.1%) isolates produced siderophores whereas 36 (25.0%) and 31 (21.5%) isolates produced HCN and ACC deaminase, respectively. A positive correlation existed between siderophore and ACC deaminase producers. Cluster analysis showed rhizosphere as the major factor influencing the ecological distribution and physiological characterization of phosphate solubilizing bacteria (PSB). Based on partial 16S rRNA gene sequencing PSB were identified as Pseudomonas putida, Pseudomonas sp. and Pseudomonas plecoglossicida with highest phosphate solubilization ability. In conclusion, these phosphate solubilizing fluorescent pseudomonads would help in understanding their role in phosphorus solubilization and identification of potent phosphorus solubilizers from the rhizosphere of commercially grown A. barbadensis.

Protective role of epiphytic fluorescent Pseudomonas on natural postharvest decay of tomato at room temperature.

Following harvest, tomato fruits are susceptible to attack by many fungal pathogens, but healthy fruits may also harbor beneficial microflora, which can delayed the spoilage of fruit. In this study, 30 isolates of epiphytic fluorescent Pseudomonas were isolated from healthy fruits of lemon, melon, grapefruit, tomato and orange. Twelve isolates were identified on molecular basis by amplifying 16S rDNA using a genus-specific primer set PA-GS-F 5’-GACGGGTGAGTAATGCCTA-3’ and PA-GS-R F 5’-CACTGGTGTTCCTTCCTATA-3’ on a conserved sequence of the genus Pseudomonas with a product size ~618 bp. Three potential isolates were examined for their ability to delayed the postharvest natural spoilage and maintained the physiochemical properties during storage for fifteen days in season 2013 and 2014. All three isolates showed promising control of postharvest diseases of tomato in comparison with control in both seasons up to fifteen days of storage at room temperature (23±4 oC, Rh 25-70%). The epiphytic bacterial isolates has delayed the fruit weight loss and maintained fruit firmness, total solids, pH and titratable acidity. Isolates also slowed the accumulation of lycopene indicating their potential in controlling the major changes in physiochemical properties. In both season Pseudomonas treated tomatoes showed no or negligible infestation of common postharvest fungi and bacteria as compared to control and positive control (1% K-sorbate).

Phylogenetic relationships of fluorescent Pseudomonad isolates associated with bacterial canker of stone fruit trees in Kurdistan province, Iran

Bacterial canker is one of the most important diseases of stone fruit trees in various locations of Kurdistan province, Iran. Genetic diversity and evolutionary relationships among 20 fluorescent pseudomonads isolated from stone fruit trees with symptoms similar to bacterial canker were investigated using a polyphasic approach by means of phenotypic characterizations, repetitive PCR using the REP and ERIC primers and multilocus sequence typing (MLST) of four housekeeping genes (gapA, rpoD, gyrB and gltA). The pathogenicity of strains was carried out under greenhouse conditions. Twelve strains produced an expected amplified DNA fragment of about 752-bp which indicated the presence of the syrB gene. Based on MLST, these strains belonged to P. syringae species complex and included in the genomospecies 1, phylogroup 2b and 2d. Phylogenetic analysis of the other eight fluorescent pseudomonad strains by using gyrB and rpoD sequences allowed the identification of strains into P. fluorescens, P. putida and P. lutea groups. Unweighted pair group method analysis (UPGMA) of genomic fingerprints obtained by rep-PCR revealed 17 different patterns which grouped P. syringae strains into three clusters clearly separated from other fluorescent pseudomonads. MLST confirmed the genetic variability among strains obtained by rep-PCR. Grouping identified of P. syringae strains by both rep-PCR and MLST was related to geographic locations of strains.

Postharvest biological control of blue mold of apple by Pseudomonas fluorescens during commercial storage and potential modes of action

Three Pseudomonas fluorescens isolates, 1–112, 2–28 and 4–6, isolated from the rhizosphere of pulse crops were tested for their ability to suppress Penicillium expansum (blue mold) on ‘McIntosh’ and ‘Spartan’ apples in commercial cold storage, and their possible mechanisms of action were investigated in vitro. On ‘McIntosh’ apples the decay incidence and lesion diameter of blue mold were significantly reduced by isolates 1–112 and 4–6 compared with control fruits after 15 weeks storage at 1°C. On ‘Spartan’ apples only isolate 2–28 provided significant levels of disease control after 15 weeks of storage at 1°C. In dual culture and in volatile tests all three isolates of P. fluorescens significantly inhibited conidial germination and mycelial growth of P. expansum in vitro. All three isolates were positive for the production of protease, but negative for cellulase, chitinase and glucanase. Molecular evidence for the potential for synthesis of the antibiotic, phenazine-1-carboxylic acid, in isolates 1–112 and 4–6 and of hydrogen cyanide in isolate 2–28 was obtained by polymerase chain reaction of phzCD and hcnBC genes, respectively. Genes for 2,4-diacetylphloroglucinol, pyoluteorin and pyrrolnitrin production were not detected in any of the P. fluorescens isolates. Scanning electron microscopy indicated that all three P. fluorescens isolates adhered to the fungal hyphae and colonized the wounds of apples, but only isolate 1–112 was able to colonize conidia of the fungal pathogen. P. fluorescens’ ability to compete for nutrients and space and produce inhibitory metabolites that target conidial germination and mycelial growth may be the basis for its control of P. expansum on apple.

Identification of siderophore producing and cynogenic fluorescent Pseudomonas and a simple confrontation assay to identify potential bio-control agent for collar rot of chickpea

In soil, plant roots coexist with bacteria and fungi that produce siderophores capable of sequestering the available iron. Microbial cyanogenesis has been demonstrated in many species of fungi and in a few species of bacteria (e.g., Chromobacterium and Pseudomonas). Fluorescent Pseudomonas isolates P29, P59, P144, P166, P174, P187, P191 and P192 were cyanogenic and produced siderophores in the presence of a strong chelater 8-Hydroxyquinoline (50 mg/l). A simple confrontation assay for identifying potential antagonists was developed. Fluorescent Pseudomonas isolates P66, P141, P144, P166 and P174 were antagonistic against both Rhizoctonia solani and Sclerotium rolfsii. Vigorous plant growth was observed following seed bacterization with P141, P200 and P240. In field experiments, seed bacterization with selected bacterial isolates resulted in reduced collar rot (S. rolfsii) incidence.

Crop specific plant growth promoting effects of ACCd enzyme and siderophore producing and cynogenic fluorescent Pseudomonas

Fluorescent Pseudomonas, aerobic, Gram-negative bacteria possess many traits that make them well suited as biocontrol and growth promoting agents. Our study revealed that isolates vary in mechanisms involved in the antagonist interactions against pathogen and growth stimulatory effects on host plant. Most of the potential antagonistic fluorescent Pseudomonas identified were avid iron chelators (P233, P201, 176, P76 and, P76). Wide variation in ACCd enzyme production was observed. ACCd enzyme assay tested P141 > P247 > P126, as potential ACCd enzyme producer. Cynogenic fluorescent Pseudomonas isolates P76 and P124 exerted strong inhibitory against S. rolfsii. However, another cynogenic fluorescent Pseudomonas P179 had no influence against R solani and S. rolfsii which remains unexplained. Noticeable crop specific plant growth stimulation exerted by different fluorescent Pseudomonas was observed on wheat (P124), chickpea (P72), lathyrus (P85, P216), greengram (P11), blackgram (P99, P233); bottlegourd (P248, P167); rice (P176, P247).

Analysis of genetic diversity among the isolates of Pseudomonas fluorescens isolated fromonion rhizosphere region

Pseudomonas fluorescens was isolated from different onion growing areas of Tamil Nadu, India and they were screened against Fusarium oxysporum f.sp. cepae in vitro . RAPD analysis was carried out using twelve random primers, each of them consisted of 10 base pairs. Analysis of the genetic co-efficient matrix derived from the scores of RAPD profile, showed that minimum and maximum per cent similarities among Pseudomonas fluorescens isolates were in the range of 10 to 92 per cent, respectively. Cluster analysis by using the unweighted pair-group method with arithmetic average (UPGMA), clearly separated the isolates into 2 major clusters (A and B) confirming the genetic diversity among the isolates of Pseudomonas fluorescens isolated from onion.

English

Cyclic lipopeptides (CLPs) with antibiotic, biosurfactant producing fluorescent pseudomonads were isolated from sugar beet-maize intercropped in sandy loam soils at Maize Research Station, Vagarai, TNAU. Approximately 20 fluorescent pseudomonads from sandy loam soils were isolated by using two different growth media. The strains were distinguished based on their growth, CFU/g, fluorescence, and pigment production. Growth inhibition of maize pathogens by CLP producing fluorescent pseudomonads strains were studied by dual culture experiments. The impact of CLP producing flurorescent pseudomonads strain on the zoospores of Downy mildew pathogen of maize was studied by direct microscopy and encysted zoospores were observed. Invitro, biochemical experiments confirmed the presence of Viscosinamide producing strain among the fluorescent pseudomonads isolates in terms of utilization of C and N sources. The particular strain was tested for its growth promoting activity by treating the maize seeds for their germination, and seedling vigour performance. Fluorescent pseudomonads can be affiliated to group under CLP producing biotypes/biovars. Purification of CLP (Viscosinamide) and characterization by HPLC analysis was carried out. Pot culture experiments were conducted to test the performance of CLP producing Pf strains in maize crop for testing their disease resistance. These biovars with antibiotic properties are the potential targets for the disease management in maize. CLPs in general receive considerable attention as potent antimicrobial drugs. Key words: Cyclic lipopeptides, fluorescent pseudomonads, viscosinamide, zoospores, antifungal.

Detection of antimicrobial traits in fluorescent pseudomonads and molecular characterization of an antibiotic pyoluteorin.

Thirty isolates of fluorescent pseudomonads were obtained from rhizosphere of different crops in Raichur, India. The fluorescent pseudomonad strains were characterized in vitro for biochemical traits, antimicrobial traits, and pyoluteorin antibiotic production. All the isolates that showed fluorescent pigment production under UV light were rod shaped, Gram negative, positive for oxidase, catalase and citrate utilization tests, and negative for indole test. Out of 30 isolates, 07 isolates were positive for HCN production, 15 isolates were positive for H2S production, and all the isolates were positive for siderophore production. Among all the isolates, RFP-22 showed the maximum percent inhibition of mycelium (46.66 %) of Rhizoctonia solani, the pathogen, and the remaining isolates showed the moderate to least inhibition of mycelium growth of R. solani. The 16S rRNA analysis confirmed that the antibiotic positive isolates belonged to genus Pseudomonas. The amplification of 779 bp region in isolates RFP- 4 and RFP-19 corresponded to pyoluteorin antibiotic-coding pltB gene. Further characterization of pyoluteorin antibiotic through TLC and TOF–MS analysis confirmed the presence of pyoluteorin at 274.26 (g/mol) peak and 2.10 min retention time. Biochemical and molecular analyses confirmed the antagonism of Pseudomonas and isolate through pyoluteorin production.

Fluorescent Pseudomonas Mediated Alleviation of Trivalent Chromium Toxicity in Ragi Through Enhanced Antioxidant Activities

Heavy metal pollution due to incessant industrialization is a major concern as it affects the growth and productivity of many plants through structural damage, growth inhibition and decline in physiological functions. In the present study, ragi, a crop with strong sustainability against environmental variations, has been used as an experimental plant in alleviating chromium stress using isolates of fluorescent Pseudomonas (FP). Forty-two FP isolates from rhizosphere soils, both from polluted and non-polluted sites of Karnataka, were morphologically and biochemically characterized and screened for plant growth promoting (PGP) traits viz., Indole-like compounds, siderophore, phosphate solubilization, ammonia and vigour index. Best thirteen isolates based on PGP traits were shortlisted for further studies out of which ragi plants were treated with three isolates (JUP2, JUP5, and JUP9) under chromium stress under green house studies based on their growth promoting traits. The plant leaf samples were analyzed biochemically for total proteins, phenolic content and enzymatic and non-enzymatic antioxidants. The results showed that the priming with three Pseudomonas isolates contributed in positive physiological variation, pertaining to chromium induced oxidative stress, in host plant. Additionally, significant growth inhibition by heavy metal toxicity was also alleviated by Pseudomonas priming.

Lower Frequency and Diversity of Antibiotic-Producing Fluorescent Pseudomonads in Rhizosphere of Indian Rapeseed–Mustard (Brassica juncea L. Czern.)

Fluorescent pseudomonads are one of the most important microbial communities which play a key role in rhizosphere to enhance plant growth-promotion and protection. The diverse groups of antibiotics viz. 2,4-diacetylphloroglucinol (DAPG), phenazine-1-carboxylic acid (PCA) and pyoluteorin (PLT) are produced by fluorescent pseudomonads inhibiting growth of fungal pathogens which results in health upliftment of plants. The present study, discusses about frequency and diversity of 138 antibiotic-producing fluorescent pseudomonads isolated from eight genotypes of rapeseed mustard rhizosphere (Brassica juncea L. Czern.). The plant growth promoting traits and antibiotics (DAPG, PCA and PLT) production of isolates were examined by using polymerase chain reaction (PCR), thin layer chromatography (TLC) and dot blot-hybridization. Among 138 isolates, 47, 25 and 9 % of isolates were positive in indole production, phosphate solubilization and antagonism potential against Sclerotinia sclerotiorum (causal agent of white mold disease in rapeseed mustard), respectively. PCR amplifications showed that none of the isolates had phlD (DAPG) and phzC (PCA) genes, but four isolates (UKA-2, UKA-8, UKA-11, UKA-66) had pltB (PLT) gene, which was further confirmed by TLC and DNA dot-blot hybridization. BOX profiles of pltB positive isolates were distinct, showing unique genetic diversity in the small population. The four pltB positive fluorescent pseudomonad isolates could be used as promising bio-control and plant growth-promoting inoculants for Indian rapeseed mustard.

Fluorescent Pseudomonas Strains with only Few Plant-Beneficial Properties Are Favored in the Maize Rhizosphere.

Plant Growth-Promoting Rhizobacteria (PGPR) enhance plant health and growth using a variety of traits. Effective PGPR strains typically exhibit multiple plant-beneficial properties, but whether they are better adapted to the rhizosphere than PGPR strains with fewer plant-beneficial properties is unknown. Here, we tested the hypothesis that strains with higher numbers of plant-beneficial properties would be preferentially selected by plant roots. To this end, the co-occurrence of 18 properties involved in enhanced plant nutrition, plant hormone modulation, or pathogen inhibition was analyzed by molecular and biochemical methods in a collection of maize rhizosphere and bulk soil isolates of fluorescent Pseudomonas. Twelve plant-beneficial properties were found among the 698 isolates. Contrarily to expectation, maize preferentially selected pseudomonads with low numbers of plant-beneficial properties (up to five). This selection was not due to the predominance of strains with specific assortments of these properties, or with specific taxonomic status. Therefore, the occurrence of only few plant-beneficial properties appeared favorable for root colonization by pseudomonads.

Interactive Effect of Fluorescent Pseudomonads Rhizobacteria and Zn on the Growth, Chemical Composition, and Water Relations of Pistachio (Pistacia vera L.) Seedlings under NaCl Stress

ABSTRACTThe role of fluorescent pseudomonads isolates (pf0, pf1, pf2, and pf3) and zinc (Zn) (0 and 5 mg kg−1 soil) interactions in alleviating salinity in pistachio seedlings were investigated. The experiment was conducted following completely randomized design with three replicates. The results revealed that salinity decreased the growth parameters, while application of PGPR (plant growth-promoting rhizobacteria) and Zn increased these parameters. Application of PGPR significantly enhanced phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), Zn, Ca/sodium (Na), and K/Na contents, while decreased the accumulation of Na and chloride (Cl). Application of PGPR and Zn increased the phenolic compounds, sucrose, membrane stability index (MSI), and relative water content (RWC) but reduced the malondialdehyde (MDA) amount. A positive correlation was observed between Zn concentrations with seedling dry weights, phenolic compounds, MSI, and RWC contents. These results indicated that the combined application of PGPR and Zn could be a simple treatment for growth and establishment of pistachio seedlings under Zn deficiency and soil salinity.

Örtü Toprağında Bulunan Bazı Yararlı Bakterilerin Kültür Mantarı Agaricus bisporus’un Gelişimi ve Verimi Üzerine Etkileri

This research was carried out to determine the interaction between some bacteria naturally existing in casing soil and Agaricus bisporus (Sylvan Hauser A15) hypha in laboratory (in vitro) and cultivation (in vivo) conditions, and to confirm its effects on mushroom yield. Totally 32 bacteria (3 Gram (+) and 29 Fluorescent Pseudomonads) was isolated from casing soil and healthy sporophores. As a result of in vitro experiment carried out to determine the effects of bacteria on mycelium growth of A. bisporus, 24 bacterial isolates were found more effective at the rate of 2 to 115% than control treatment. To determine the effects of bacterium, chosen at the end of in vitro experiments, on mushroom yield in cultivation conditions, three experiments were established in March, May and July in 2008. At the end of experiments, bacterial isolates provided 8 – 40 % increase in total yield. Population density and change in population number related to time was observed during growing period, after the inoculation of bacterial isolates into casing soil. According to the results, Pseudomonas fluorescens (T 4/2 and Ş 8), P.putida (Ş 2/1 and Ş 10) and Bacillus mycoides (T 7/2) bacterial isolates were colonized successfully both in casing soil and sporophores.

Isolation of <i>Pseudomonas fluorescens</i> Species from faba Bean Rhizospheric Soil and Assessment of Indole Acetic Acid Production: In Vitro Study, Ethiopia

The microbial inoculants that are used in agriculture include phytohormone synthesis which have role to increase crop growth and yield products. Some microbes have a potential to synthesize plant hormone through utilize the root exudates of plant in rhizospheric area. The objective of this study was to isolate some Pseudomonas fluorescens species from rhizospheric soil of faba bean and tested their indole acetic acid production. Isolation of Pseudomonas fluorescens isolates were carried out on King’s B medium. All isolates Pseudomonas fluorescens were tseted for indole acetic acid production have a potential to produce phytohormone. The test Pseudomonas fluorescens isolates culture were inoculated in the nutrient broth with L-tryptophan 500 mg/l at 28 ± 2°C for one week. The results indicated that all most of the isolates tested possess plant growth promoting traits (phytohormone). So it could be concluded that all isolate Pseudomonas fluorescens can be used as plant growth promoting bacteria for synthesis of plant hormone resulting to increase of the plant growth and yield.

Isolation of <i>Pseudomonas flurescens</i> from Rhizosphere of Faba Bean and Screen Their Hydrogen Cyanide Production Under in Vitro Stduy, Ethiopia

Hydrogen cyanide is a highly toxic volatile compound which interferes with the cellular respiration by inhibiting the cytochrome oxidase enzyme in mitochondria. Root area of crops were consisting several bacteria that may have beneficial aspects. The objective of this study was to investigate the qualitative capability of hydrogen cyanide production by Pseudomonas fluorescens species isolates. Isolation of Pseudomonas fluorescens isolates were carried out on King’s B medium. Twelve Pseudomonas fluorescens species were isolated from the Rhizosphere of Fabaceae family namely faba bean screened for the production of hydrogen cyanide. For the production of hydrogen cyanide, Pseudomonas fluorescens isolates were streaked into King’s B agar plates supplemented with glycine. Total of Pseudomonas fluorescens isolates had a potential to produce hydrogen cyanide. Therefore, these isolated can be used as a biological control against plant pathogen microbes.

Biological control of cotton seedling diseases by fluorescent pseudomonas spp

Seedling root rot seen in many plants including cotton is an important disease that leads to large economic losses. Human health and the environment are negatively affected as a result of using fungicides for disease control. The goal of this study was to determine the effects of fluorescent Pseudomonas (FP) bacteria against seedling root rot pathogens both in vitro and in vivo conditions. 59 FP isolates obtained from the rhizosphere of cotton and weeds on the field were tested by dual-culture assays in vitro. After applying effective FP isolates on the seeds, antagonistic effects against the seedling root rot pathogens were investigated in a climate chamber. Resulting of dual-culture tests, FP40 had maximum effect (49.60%) against Rhizoctonia solani. Besides, FP51, FP48 and FP35 had highest impact as 43.80%, 43.50%, and 43.10% against Fusarium sp., respectively. Pythium deliense was mostly effected by FP57 (59.80%), FP52 (57.80%) and FP56 (57.60%). While isolates FP35 and FP57 provided protection over 70% against all three pathogens in a climate chamber, they were as effective as commercial fungicides (Vitavax and Maxim) and biofungicide (Subtilex) and shown promising results.