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.

scholarly journals Soil Chemical and Physical Properties Associated with Suppression of Take-all of Wheat by Trichoderma koningii

1997 ◽  
Vol 87 (11) ◽  
pp. 1118-1124 ◽  
Author(s):  
Brion K. Duffy ◽  
Bonnie H. Ownley ◽  
David M. Weller
Keyword(s):  
United States ◽  
Soil Ph ◽  
Nitrate Nitrogen ◽  
The United States ◽  
Disease Suppression ◽  
Soil Parameters ◽  
Principal Component Factor Analysis ◽  
Trichoderma Koningii ◽  
Biocontrol Activity ◽  
Take All

Trichoderma koningii, originally isolated from a take-all-suppressive soil in Western Australia, has been shown to protect wheat against take-all disease and increase grain yield in field trials in Australia, China, and the United States. However, within a region, the level of protection provided by T. koningii can dramatically vary between field sites. We evaluated suppression of take-all by this fungus in eight silt loams from the Pacific Northwest of the United States and the influence of 21 abiotic soil parameters on biocontrol activity. While T. koningii significantly increased plant growth and reduced disease severity in all eight silt loams, the level of protection varied significantly among the soils. Disease suppression was not associated with the conduciveness of a soil to take-all, but rather to the supportiveness of a soil to biocontrol activity. Biocontrol activity was positively correlated with iron, nitrate-nitrogen, boron, copper, soluble magnesium, and percent clay, and negatively correlated with soil pH and available phosphorus. Principal component factor analysis using these eight variables resulted in a three-component solution that accounted for 95% of the variation in disease rating. Least squares regression analysis (R2 = 0.992) identified a model that included nitrate-nitrogen, soil pH, copper, and soluble magnesium, and described the variance in take-all suppression by T. koningii. Potential applications of these results include amending soil or inoculants with beneficial factors that may be lacking in the target soil and customizing biocontrol treatments for sites that have parameters predictive of a favorable environment for disease suppression.

scholarly journals Role of Gluconic Acid Production in the Regulation of Biocontrol Traits of Pseudomonas fluorescens CHA0

2009 ◽  
Vol 75 (12) ◽  
pp. 4162-4174 ◽  
Author(s):  
Patrice de Werra ◽  
Maria Péchy-Tarr ◽  
Christoph Keel ◽  
Monika Maurhofer
Keyword(s):  
Pseudomonas Fluorescens ◽  
Gluconic Acid ◽  
Acid Production ◽  
Disease Suppression ◽  
Gaeumannomyces Graminis ◽  
Antifungal Compounds ◽  
Enhanced Production ◽  
Biocontrol Activity ◽  
Gluconic Acid Production

ABSTRACT The rhizobacterium Pseudomonas fluorescens CHA0 promotes the growth of various crop plants and protects them against root diseases caused by pathogenic fungi. The main mechanism of disease suppression by this strain is the production of the antifungal compounds 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT). Direct plant growth promotion can be achieved through solubilization of inorganic phosphates by the production of organic acids, mainly gluconic acid, which is one of the principal acids produced by Pseudomonas spp. The aim of this study was to elucidate the role of gluconic acid production in CHA0. Therefore, mutants were created with deletions in the genes encoding glucose dehydrogenase (gcd) and gluconate dehydrogenase (gad), required for the conversion of glucose to gluconic acid and gluconic acid to 2-ketogluconate, respectively. These enzymes should be of predominant importance for rhizosphere-colonizing biocontrol bacteria, as major carbon sources provided by plant root exudates are made up of glucose. Our results show that the ability of strain CHA0 to acidify its environment and to solubilize mineral phosphate is strongly dependent on its ability to produce gluconic acid. Moreover, we provide evidence that the formation of gluconic acid by CHA0 completely inhibits the production of PLT and partially inhibits that of DAPG. In the Δgcd mutant, which does not produce gluconic acid, the enhanced production of antifungal compounds was associated with improved biocontrol activity against take-all disease of wheat, caused by Gaeumannomyces graminis var. tritici. This study provides new evidence for a close association of gluconic acid metabolism with antifungal compound production and biocontrol activity in P. fluorescens CHA0.

Changes in take-all (Gaeumannomyces graminis var. tritici), Rhizoctonia root rot (Rhizoctonia solani) and soil pH in continuous wheat with annual applications of nitrogenous fertiliser in Western Australia

1988 ◽  
Vol 28 (3) ◽  
pp. 333 ◽  
Author(s):  
GC MacNish
Keyword(s):  
Soil Ph ◽  
Root Rot ◽  
Ammonium Nitrogen ◽  
Gaeumannomyces Graminis ◽  
Continuous Cropping ◽  
Rhizoctonia Root Rot ◽  
Continued Use ◽  
Effect On Yield ◽  
Gaeumannomyces Graminis Var Tritici ◽  
Take All

Experiments were conducted to test the hypotheses that: (i) continuous cropping with wheat would lead to a decline in take-all, (ii) ammonium nitrogen would reduce take-all compared with nitrate nitrogen, and (iii) that both sources of nitrogen would lead to a decline in soil pH. Attempts were also made to confirm that rhizoctonia root rot would vary unpredictably in continuous wheat and would be reduced by nitrogen. Wheat was grown without nitrogen (Nil) or with sodium nitrate (SN) or ammonium sulfate (AS) for 11, 10 and 9 consecutive years at Newdegate, Esperance and Mount Barker respectively. Rates of nitrogen were 50, 25 and 45 kg ha-1 at Newdegate, Esperance and Mount Barker respectively. A decline in take-all incidence was established at Newdegate, and plots treated with AS generally had a lower take-all incidence than did plots without nitrogen or treated with SN. At Esperance, a decline in take-all incidence was established only in AS treated plots. Take-all incidence was lower in plots treated with AS than plots without nitrogen or treated with SN in 6 years out of 10 at Esperance. No take-all decline was observed at Mount Barker and take-all incidence was rarely lower in plots treated with AS than in those without nitrogen or treated with SN. All treatments reduced soil pH at Newdegate and Esperance, which were weakly buffered sites, but at Mount Barker (a highly buffered site) only AS reduced pH. Rhizoctonia root rot was not found at Mount Barker. At Newdegate and Esperance it first occurred in the eighth and fifth crops respectively. Incidence peaked at about 60% of plants being affected in the ninth crop at Newdegate and 95% in year 7 at Esperance, and then declined to less than 5% at both sites. Applications of nitrogen had no effect on incidence of rhizoctonia root rot. Yields varied considerably between sites and years. Combining results for all years at each site showed that AS increased yield at all sites and SN increased yields at Newdegate and Mount Barker compared with no nitrogen. The continued use of AS at Mount Barker eventually had an adverse effect on yield.

Failure of liming to increase grain yield of wheat and triticale in acid soils may be due to the associated increase in incidence of take-all (Gaeumannomyces graminis var. tritici)

1987 ◽  
Vol 27 (3) ◽  
pp. 411 ◽  
Author(s):  
GM Murray ◽  
BJ Scott ◽  
Z Hochman ◽  
BJ Butler
Keyword(s):  
Regression Analysis ◽  
Grain Yield ◽  
Soil Ph ◽  
New South ◽  
Acid Soils ◽  
Gaeumannomyces Graminis ◽  
South Wales ◽  
Expected Increase ◽  
Gaeumannomyces Graminis Var Tritici ◽  
Take All

Lime was applied at rates from 0 to 5.0 t ha-1 at 4 sites in southern and central New South Wales. A root and crown disease characterised by basal stem blackening affected up to 60% of wheat plants and 80% of triticale plants when the soil pH in 0.01 mol L-1 CaCl2 was above 5.0 at all 4 sites. Below pH 4.8, incidence was less than 5%. The take-all fungus, Gaeumannomyces graminis var. tritici, was consistently associated with this symptom. Losses in grain yield from the disease ranged from 26 to 77% depending on site. Regression analysis indicates that each 10% increase in plants with basal stem blackening decreased yield by 0.76%. These results demonstrate that the disease can reverse the expected increase in yield after liming, and that progressive acidification of the soils in the region may have caused the present reduced amount of take-all.

scholarly journals Biocontrol Traits of Pseudomonas spp. Are Regulated by Phase Variation

2003 ◽  
Vol 16 (11) ◽  
pp. 1003-1012 ◽  
Author(s):  
Daan van den Broek ◽  
Thomas F. C. Chin-A-Woeng ◽  
Kevin Eijkemans ◽  
Ine H. M. Mulders ◽  
Guido V. Bloemberg ◽  
...  
Keyword(s):  
Phase I ◽  
Phase Ii ◽  
Phase Variation ◽  
Antagonistic Activity ◽  
Vital Role ◽  
Disease Suppression ◽  
Gene Encoding ◽  
Antifungal Metabolites ◽  
Biocontrol Activity ◽  
Take All

Of 214 Pseudomonas strains isolated from maize rhizosphere, 46 turned out to be antagonistic, of which 43 displayed clear colony phase variation. The latter strains formed both opaque and translucent colonies, designated as phase I and phase II, respectively. It appeared that important biocontrol traits, such as motility and the production of antifungal metabolites, proteases, lipases, chitinases, and biosurfactants, are correlated with phase I morphology and are absent in bacteria with phase II morphology. From a Tn5luxAB transposon library of Pseudomonas sp. strain PCL1171 phase I cells, two mutants exhibiting stable expression of phase II had insertions in gacS. A third mutant, which showed an increased colony phase variation frequency was mutated in mutS. Inoculation of wheat seeds with PCL1171 bacteria of phase I morphology resulted in efficient suppression of take-all disease, whereas disease suppression was absent with phase II bacteria. Neither the gacS nor the mutS mutant was able to suppress take-all, but biocontrol activity was restored after genetic complementation of these mutants. Furthermore, in a number of cases, complementation by gacS of wild-type phase II sectors to phase I phenotype could be shown. A PCL1171 phase I mutant defective in antagonistic activity appeared to have a mutation in a gene encoding a lipopeptide synthetase homologue and had lost its biocontrol activity, suggesting that biocontrol by strain PCL1171 is dependent on the production of a lipopeptide. Our results show that colony phase variation plays a regulatory role in biocontrol by Pseudomonas bacteria by influencing the expression of major biocontrol traits and that the gacS and mutS genes play a role in the colony phase variation process. Therefore phase variation not only plays a role in escaping animal defense but it also appears to play a much broader and vital role in the ecology of bacteria producing exoenzymes, antibiotics, and other secondary metabolites.

scholarly journals Biological Control of Wheat Root Diseases by the CLP-Producing Strain Pseudomonas fluorescens HC1-07

2014 ◽  
Vol 104 (3) ◽  
pp. 248-256 ◽  
Author(s):  
Ming-Ming Yang ◽  
Shan-Shan Wen ◽  
Dmitri V. Mavrodi ◽  
Olga V. Mavrodi ◽  
Diter von Wettstein ◽  
...  
Keyword(s):  
Biological Control ◽  
Pseudomonas Fluorescens ◽  
Root Rot ◽  
Gaeumannomyces Graminis ◽  
Protease Production ◽  
Ionization Mass ◽  
Soilborne Disease ◽  
Rhizoctonia Root Rot ◽  
Take All

Pseudomonas fluorescens HC1-07, previously isolated from the phyllosphere of wheat grown in Hebei province, China, suppresses the soilborne disease of wheat take-all, caused by Gaeumannomyces graminis var. tritici. We report here that strain HC1-07 also suppresses Rhizoctonia root rot of wheat caused by Rhizoctonia solani AG-8. Strain HC1-07 produced a cyclic lipopeptide (CLP) with a molecular weight of 1,126.42 based on analysis by electrospray ionization mass spectrometry. Extracted CLP inhibited the growth of G. graminis var. tritici and R. solani in vitro. To determine the role of this CLP in biological control, plasposon mutagenesis was used to generate two nonproducing mutants, HC1-07viscB and HC1-07prtR2. Analysis of regions flanking plasposon insertions in HC1-07prtR2 and HC1-07viscB revealed that the inactivated genes were similar to prtR and viscB, respectively, of the well-described biocontrol strain P. fluorescens SBW25 that produces the CLP viscosin. Both genes in HC1-07 were required for the production of the viscosin-like CLP. The two mutants were less inhibitory to G. graminis var. tritici and R. solani in vitro and reduced in ability to suppress take-all. HC1-07viscB but not HC-07prtR2 was reduced in ability to suppress Rhizoctonia root rot. In addition to CLP production, prtR also played a role in protease production.

scholarly journals Corn and Rice Cultivation Affect Soil Organic and Inorganic Carbon Storage through Altering Soil Properties in Alkali Sodic Soils, Northeast of China

2020 ◽  
Vol 12 (4) ◽  
pp. 1627
Author(s):  
Jingjing Wang ◽  
Jie Tang ◽  
Zhaoyang Li ◽  
Wei Yang ◽  
Ping Yang ◽  
...  
Keyword(s):  
Soil Properties ◽  
Soil Ph ◽  
Inorganic Carbon ◽  
Terrestrial Ecosystems ◽  
Invertase Activity ◽  
Rice Cultivation ◽  
Total Carbon ◽  
Exchangeable Sodium ◽  
Sodic Soils ◽  
Crop Cultivation

Soil organic carbon (SOC) and soil inorganic carbon (SIC) play essential roles in carbon cycling in terrestrial ecosystems; however, the effects of crop cultivation on them are still poorly understood, especially in alkali sodic soils widely distributed in semiarid regions. Alkali sodic soils from cornfields and paddies with cultivation years of 5, 15, and 25 were analyzed here to assess the response of soil properties and soil carbon pools to crop cultivation. Soil pH and exchangeable sodium percentages decrease in accordance with cultivation years, while enzyme activity (amylase, invertase, and catalase) shows a contrary trend. Soil pH and exchangeable sodium percentages are negatively correlated with SOC, but positively correlated with SIC. Redundancy analysis reveals an obvious relationship between SOC and invertase activity. The percentage of δ13CSOC found here is approximately –24.78‰ to –22.97‰ for cornfields and approximately –26.54‰ to –23.81‰ for paddies, suggesting that crop cultivation contributes to SOC sequestration and stocking, increasing with cultivation years. The percentage of δ13CSIC found here is approximately 1.90‰ to 3.73‰, proving that lithogenic inorganic carbon is the major SIC, where the stock decreases with increasing cultivation years. Significant total carbon stock loss is observed in cornfields, while it is preserved at 120 Mg ha−1 in paddies. We conclude here from the results that corn and rice cultivation reduce alkali sodic conditions in soil, thereby improving soil enzymes and favoring SOC stocking, but reducing SIC stocks.

The influence of soil-pH on the saprophytic growth in soil of the take-all fungus Gaeumannomyces graminis var tritici

Soil Research ◽  
1991 ◽  
Vol 29 (5) ◽  
pp. 627 ◽  
Author(s):  
OF Glenn ◽  
K Sivasithamparam
Keyword(s):  
Soil Ph ◽  
Calcium Ions ◽  
Indirect Effects ◽  
Growth Response ◽  
Gaeumannomyces Graminis ◽  
Direct Effects ◽  
Disease Response ◽  
Effects Of Ph ◽  
Gaeumannomyces Graminis Var Tritici ◽  
Take All

Experiments were conducted firstly, to determine whether there was a difference in saprophytic growth response of the pathogen to pH in soil from that on agar. Secondly, we examined whether the response to liming involved a sensitivity of the fungus to the concentration of hydrogen (H+) or calcium ions (Ca2+). The saprophytic growth of the take-all fungus showed that, although it is sensitive to soil pH, each strain behaves differently, and this behaviour cannot be predicted from agar studies. It seems unlikely, therefore, that the observed disease response to soil pH resulted from direct effects on the saprophytic phase of the fungus. There was no indication that increase in the Ca2+ in soil played any part in the growth response of the fungus. The potential for other indirect effects of pH on nutrient availability to the plant and to other stages in the disease cycle is discussed.

scholarly journals Changes in Soil Properties and Bacterial Community Composition with Biochar Amendment after Six Years

Agronomy ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 746
Author(s):  
Shuxiu Fan ◽  
Jiacheng Zuo ◽  
Hangyu Dong
Keyword(s):  
Bacterial Community ◽  
Soil Properties ◽  
Community Composition ◽  
Soil Ph ◽  
Relative Abundance ◽  
Bacterial Community Composition ◽  
Soil Characteristics ◽  
Total Carbon ◽  
Available Phosphorus ◽  
Biochar Amendment

Changes in soil physicochemical properties and bacterial community composition were investigated six years after biochar amendment at 0%, 4%, 8% and 12% (w/w), which were coded as C0, C1, C2 and C3, respectively. Results showed that some soil characteristics were sustainable, as they were still affected by biochar addition after six years. Compared to the control, biochar-treated soils had higher pH, total carbon (TC), C/N, total nitrogen (TN), available phosphorus (AP) and available potassium (AK). Soil pH, C/N and the content of TC, TN and AK all increased along with the increase of biochar dosage. The results of Illumina MiSeq sequencing demonstrated that biochar enhanced soil bacteria diversity and modified the community composition over time. The relative abundance of Nitrospirae and Verrucomicrobia phylum increased but that of Acidobacteria phylum decreased significantly in biochar amended soils. The addition of biochar also enriched some bacterial genera, such as uncultured Nitrosomonadace, uncultured Gemmatimonadac, uncultured Nitrospiraceae and Magnetovibrio. In particular, the relative abundance of uncultured Nitrospiraceae was enhanced by 16.9%, 42.8% and 73.6% in C1, C2 and C3, respectively, compared to C0. Biochar has a potential role in enhancing the abundance of bacteria involved in N cycling. Soil pH, TC, TN, TK and AK, were closely related to alterations in the composition of the soil bacterial community. Meanwhile, these soil properties were significantly influenced by biochar amendment, which indicates that biochar affected the soil microbial community indirectly by altering the soil characteristics in the long term.

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