scholarly journals Horizontal and vertical movement of Pseudomonas fluorescens toward exudate of Macrophomina phaseolina in soil: influence of motility and soil properties

2002 ◽  
Vol 157 (2) ◽  
pp. 139-148 ◽  
Author(s):  
Tanuja Singh ◽  
Alok K. Srivastava ◽  
Dilip K. Arora
Keyword(s):  
Soil Properties ◽  
Pseudomonas Fluorescens ◽  
Macrophomina Phaseolina ◽  
Vertical Movement ◽  
Soil Influence

Phosphorus auditing cannot account for all of the phosphorus applied to different pasture soils

Soil Research ◽  
2004 ◽  
Vol 42 (1) ◽  
pp. 89 ◽  
Author(s):  
L. L. Burkitt ◽  
C. J. P. Gourley ◽  
P. W. G. Sale
Keyword(s):  
Soil Properties ◽  
Sorption Capacity ◽  
Vertical Movement ◽  
Single Application ◽  
Macropore Flow ◽  
P Sorption ◽  
P Sorption Capacity ◽  
Sampling Zone ◽  
P Movement ◽  
Total P

Five field sites established in the high rainfall zone of southern Victoria were used to examine the downwards vertical movement of phosphorus (P) fertiliser on soils which ranged in P sorption capacity. Fertiliser was applied either as a single application of 280 kg P/ha at the beginning of the experiment (April 1998), or as 35�kg�P/ha reapplied every 6 months (totalling 210 kg P/ha by the end of the third year). Soil cores were sampled in June 2001 to a depth of 40 cm, and soil at depths of 0–5, 5–10, 10–20, 20–30, and 30–40 cm was analysed for a range of soil properties and total P concentration.Total P concentration changed very little down the profile, indicating that there was minimal vertical movement of P fertiliser below the 10 cm layer of 5 pasture soils following the single application of 280 kg P/ha or 35 kg P/ha reapplied every 6 months. Soils with low to moderate surface P sorption capacity showed a trend for higher total P concentrations at depth. However, quantitative relationships between vertical P movement and soil properties at depth were poor. A P audit resulted in variable recovery of the applied P (45–128%) in the surface 40 cm at each of the 5 sites. Consistently low P recoveries were achieved at one site, where the surface soil had a high P sorption capacity. Some applied P may have bypassed the high P sorbing surface layers at this site through macropore flow and moved beyond the 40 cm sampling zone, or have been lost to surface runoff. These results question the usefulness of P audit or mass-balance methods for accounting for P movement in a pasture-based system, as spatial heterogeneity of soil properties, both horizontally and vertically, was high in the current study.

Influence of growth and environmental conditions on cell surface hydrophobicity ofPseudomonas fluorescensin non-specific adhesion

1999 ◽  
Vol 46 (1) ◽  
pp. 28-37 ◽  
Author(s):  
T K Jana ◽  
A K Srivastava ◽  
K Csery ◽  
D K Arora
Keyword(s):  
Cell Surface ◽  
Pseudomonas Fluorescens ◽  
Environmental Conditions ◽  
Prolonged Exposure ◽  
Cell Surface Hydrophobicity ◽  
Tween 80 ◽  
Macrophomina Phaseolina ◽  
Surface Hydrophobicity ◽  
Proteinase K ◽  
Outer Cell

The relative cell surface hydrophobicity (CSH) of 18 soil isolates of Pseudomonas fluorescens, determined by phase exclusion, hydrophobic interaction chromatography (HIC), electrostatic interaction chromatography (ESIC), and contact angle, revealed large degrees of variability. Variation in the adhesion efficiency to Macrophomina phaseolina of the hyphae/sclerotia of these isolates was also examined. Two such isolates with maximum (32.8%; isolate 12-94) and minimum (12%; isolate 30-94) CSH were selected for further study. Early- to mid-log exponential cells of these isolates were more hydrophobic than those in stationary phase, and the CSH of these isolates was also influenced by fluctuations in temperatures and pH. Isolate 12-94 exhibited high CSH (32.3%) at 30°C, compared to lower values (28-24%) in the higher temperature range (35-40°C). Increasing concentrations of either Zn2+, Fe3+, K+, and Mg2+in the growth medium were associated with the increased CSH. Trypsin, pepsin, and proteinase K (75 to 150 μg·mL-1) reduced the CSH of isolate 12-94 cells. CSH was reduced, following exposure to DTT, SDS, Triton X-100, or Tween 80. Prolonged exposure of cells to starvation (60 days) also caused a significant decline in CSH. Several protein bands (18, 21, 23, 26 kDa) of the outer cell membrane were absent in 60-day starved cells compared to unstarved cells. In conclusion, our findings demonstrate that CSH of P. fluorescens isolates may contribute to non-specific attachment/adhesion onto M. phaseolina hyphae/sclerotia, and the efficiency of adhesion is regulated by growth and other environmental conditions. Key words: adhesion, hydrophobicity, Pseudomonas fluorescens, Macrophomina phaseolina

Induced resistance and control of charcoal rot in Cicer arietinum (chickpea) by Pseudomonas fluorescens

2001 ◽  
Vol 79 (7) ◽  
pp. 787-795 ◽  
Author(s):  
Alok K Srivastava ◽  
Tanuja Singh ◽  
T K Jana ◽  
Dilip K Arora
Keyword(s):  
Pseudomonas Fluorescens ◽  
Cicer Arietinum ◽  
Induced Resistance ◽  
Time Course ◽  
Induced Systemic Resistance ◽  
Macrophomina Phaseolina ◽  
Systemic Resistance ◽  
Charcoal Rot ◽  
Chemical Inducers ◽  
Rot Disease

Pseudomonas fluorescens isolate 4-92 induced systemic resistance against charcoal rot disease in chickpea (Cicer arietinum L.) caused by Macrophomina phaseolina (Tassi) Goidanich. Time-course accumulation of pathogenesis-related (PR) proteins (chitinases and glucanases) in chickpea plants inoculated with P. fluorescens was significantly (P = 0.05) higher than in control plants. The level of chitinases and glucanases increased by 6.6- to 7-fold up to 4 days postinoculation; thereafter, little decrease in the activity of PR proteins was observed. Root-colonizing populations of P. fluorescens were at a maximum 2 days after transplantation at different inoculum concentrations, and decreased over time. Inoculation of root tips of chickpea by P. fluorescens, 2,6-dichloroisonicotinic acid, and o-acetylsalicylic acid induced systemic resistance against charcoal rot. Disease was 33 to 55.5% higher in control plants than in plants inoculated with chemical inducers or P. fluorescens. Single treatment of plants with P. fluorescens increased disease resistance by 33%, whereas combined application of P. fluorescens with either of the chemical inducers was most effective in inducing the resistance by 2- to 2.25-fold. The time-course study shows that an interval of at least 2 days was required between induction treatment and challenge inoculation. Biocontrol efficacy of P. fluorescens against charcoal rot disease in chickpea was demonstrated under greenhouse conditions.Key words: biological control, induced resistance, Macrophomina phaseolina, Pseudomonas fluorescens.

scholarly journals Identification and Manipulation of Soil Properties To Improve the Biological Control Performance of Phenazine-Producing Pseudomonas fluorescens

2003 ◽  
Vol 69 (6) ◽  
pp. 3333-3343 ◽  
Author(s):  
Bonnie H. Ownley ◽  
Brion K. Duffy ◽  
David M. Weller
Keyword(s):  
Soil Properties ◽  
Pseudomonas Fluorescens ◽  
Soil Ph ◽  
Ammonium Nitrogen ◽  
Disease Suppression ◽  
Gaeumannomyces Graminis ◽  
Total Carbon ◽  
Principal Component Factor Analysis ◽  
Biocontrol Activity ◽  
Take All

ABSTRACT Pseudomonas fluorescens 2-79RN10 protects wheat against take-all disease caused by Gaeumannomyces graminis var. tritici; however, the level of protection in the field varies from site to site. Identification of soil factors that exert the greatest influence on disease suppression is essential to improving biocontrol. In order to assess the relative importance of 28 soil properties on take-all suppression, seeds were treated with strain 2-79RN10 (which produces phenazine-1-carboxylate [PCA+]) or a series of mutants with PCA+ and PCA− phenotypes. Bacterized seeds were planted in 10 soils, representative of the wheat-growing region in the Pacific Northwest. Sixteen soil properties were correlated with disease suppression. Biocontrol activity of PCA+ strains was positively correlated with ammonium-nitrogen, percent sand, soil pH, sodium (extractable and soluble), sulfate-sulfur, and zinc. In contrast, biocontrol was negatively correlated with cation-exchange capacity (CEC), exchangeable acidity, iron, manganese, percent clay, percent organic matter (OM), percent silt, total carbon, and total nitrogen. Principal component factor analysis of the 16 soil properties identified a three-component solution that accounted for 87 percent of the variance in disease rating (biocontrol). A model was identified with step-wise regression analysis (R 2 = 0.96; Cp statistic = 6.17) that included six key soil properties: ammonium-nitrogen, CEC, iron, percent silt, soil pH, and zinc. As predicted by our regression model, the biocontrol activity of 2-79RN10 was improved by amending a soil low in Zn with 50 μg of zinc-EDTA/g of soil. We then investigated the negative correlation of OM with disease suppression and found that addition of OM (as wheat straw) at rates typical of high-OM soils significantly reduced biocontrol activity of 2-79RN10.

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