Biological control of damping-off of sugar-beet and cotton with Chaetomium globosum or a fluorescent Pseudomonas sp.

Seed treatment with ascospores of Chaetomium globosum reduced damping-off of sugar-beet caused by seed-borne Phoma betae and soil-borne Pythium ultimum or Rhizoctonia solani in growth chamber experiments. Seed treatment with a fluorescent Pseudomonas sp. controlled Ph. betae and P. ultimum but not R. solani. Coating cotton seeds with ascospores controlled P. ultimum and R. solani damping-off. In some experiments, biological seed treatments were equally or more effective than seed treatment with captan. However, greater variability in disease control occurred with the antagonists than with captan. Fifty percent of freshly harvested ascospores of C. globosum germinated in 8 h on water agar. When ascospores were stored under air-dried conditions for 3 days to 2.5 years, germination increased to > 90%. Under same storage conditions, survival of Pseudomonas sp. was detected after 4 months. Antagonistic activities observed in vitro were hyphal coiling of C. globosum on R. solani, and mycostasis was induced by C. globosum or Pseudomonas sp. on agar and soil. The presumed cause of mycostasis is the diffusible antifungal metabolites which may also be involved in the biological control of damping-off.

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Secondary Metabolite- and Endochitinase-Dependent Antagonism toward Plant-Pathogenic Microfungi of Pseudomonas fluorescens Isolates from Sugar Beet Rhizosphere

Applied and Environmental Microbiology ◽

10.1128/aem.64.10.3563-3569.1998 ◽

1998 ◽

Vol 64 (10) ◽

pp. 3563-3569 ◽

Cited By ~ 113

Author(s):

Mette Neiendam Nielsen ◽

Jan Sørensen ◽

Johannes Fels ◽

Hans Christian Pedersen

Keyword(s):

Biological Control ◽

Cell Wall ◽

Sugar Beet ◽

Pseudomonas Fluorescens ◽

Secondary Metabolite ◽

Pythium Ultimum ◽

Medium Composition ◽

Fungal Antagonism ◽

Lipopeptide Antibiotic

ABSTRACT Forty-seven isolates representing all biovars of Pseudomonas fluorescens (biovars I to VI) were collected from the rhizosphere of field-grown sugar beet plants to select candidate strains for biological control of preemergence damping-off disease. The isolates were tested for in vitro antagonism toward the plant-pathogenic microfungi Pythium ultimum and Rhizoctonia solani in three different plate test media. Mechanisms of fungal inhibition were elucidated by tracing secondary-metabolite production and cell wall-degrading enzyme activity in the same media. Most biovars expressed a specific mechanism of antagonism, as represented by a unique antibiotic or enzyme production in the media. A lipopeptide antibiotic, viscosinamide, was produced independently of medium composition by P. fluorescens bv. I, whereas the antibiotic 2,4-diacetylphloroglucinol was observed only in glucose-rich medium and only in P. fluorescens bv. II/IV. Both pathogens were inhibited by the two antibiotics. Finally, in low-glucose medium, a cell wall-degrading endochitinase activity in P. fluorescens bv. I, III, and VI was the apparent mechanism of antagonism toward R. solani. The viscosinamide-producing DR54 isolate (bv. I) was shown to be an effective candidate for biological control, as tested in a pot experiment with sugar beet seedlings infested with Pythium ultimum. The assignment of different patterns of fungal antagonism to the biovars of P. fluorescens is discussed in relation to an improved selection protocol for candidate strains to be used in biological control.

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Variability in Sensitivity to Metalaxyl in vitro, Pathogenicity, and Control of Pythium spp. on Sugar Beet

Plant Disease ◽

10.1094/pdis.1998.82.8.896 ◽

1998 ◽

Vol 82 (8) ◽

pp. 896-899 ◽

Cited By ~ 26

Author(s):

J. R. Brantner ◽

Carol E. Windels

Keyword(s):

Sugar Beet ◽

Disease Control ◽

Seed Treatment ◽

Linear Growth ◽

Pythium Ultimum ◽

Infested Soil ◽

Pathogenicity Tests ◽

And Control ◽

Treatment Sensitivity

Pythium ultimum var. sporangiiferum (76 isolates) and P. aphanidermatum (21 isolates) cultured from diseased sugar beet seedlings in Minnesota and North Dakota were tested for sensitivity to metalaxyl, pathogenicity on sugar beet, and disease control by metalaxyl seed treatment. Sensitivity to metalaxyl (effective concentration causing 50% growth inhibition [EC50]) was determined by linear growth on corn meal agar amended with 0, 0.01, 0.1, 1, 10, and 100 μg a.i. metalaxyl ml-1 after 48 h in the dark at 21 ± 1°C. Variation among isolates was significant (P = 0.05) within and between species, and EC50 values averaged 0.16 (range: 0.05 to 1.30 μg ml-1) for P. ultimum var. sporangiiferum and 2.06 (range: 1.19 to 3.12 μg ml-1) for P. aphanidermatum. In pathogenicity tests on sugar beet, most isolates of P. ultimum var. sporangiiferum (72 of 76) and all of P. aphanidermatum significantly (P = 0.05) decreased final stands compared to the noninoculated control. There was no correlation between aggressiveness in the absence of metalaxyl and in vitro sensitivity to metalaxyl. When Pythium-infested soil was planted with seed treated with metalaxyl at the standard (0.625 g a.i. kg-1) or half rate, some isolates that were least sensitive to metalaxyl in vitro resulted in a significant (P = 0.05) reduction in disease control. These results may explain, at least in part, why producers do not attain expected stands when they plant metalaxyl-treated sugar beet seed.

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Bio-priming Seed Treatment for Biological Control of Pythium ultimum Preemergence Damping-off in sh2 Sweet Corn

Plant Disease ◽

10.1094/pd-74-0368 ◽

1990 ◽

Vol 74 (5) ◽

pp. 368 ◽

Cited By ~ 96

Author(s):

Nancy W. Callan

Keyword(s):

Biological Control ◽

Seed Treatment ◽

Sweet Corn ◽

Pythium Ultimum ◽

Damping Off

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Biological control of cucumber and sugar beet damping-off caused by Pythium ultimum with bacterial and fungal antagonists

Journal of Applied Microbiology ◽

10.1046/j.1365-2672.2002.01658.x ◽

2002 ◽

Vol 92 (6) ◽

pp. 1078-1086 ◽

Cited By ~ 62

Author(s):

D.G. Georgakopoulos ◽

P. Fiddaman ◽

C. Leifert ◽

N.E. Malathrakis

Keyword(s):

Biological Control ◽

Sugar Beet ◽

Pythium Ultimum ◽

Damping Off

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Comparison of Muscodor albus Volatiles with a Biorational Mixture for Control of Seedling Diseases of Sugar Beet and Root-Knot Nematode on Tomato

Plant Disease ◽

10.1094/pdis-91-2-0220 ◽

2007 ◽

Vol 91 (2) ◽

pp. 220-225 ◽

Cited By ~ 37

Author(s):

E. Grimme ◽

N. K. Zidack ◽

R. A. Sikora ◽

G. A. Strobel ◽

B. J. Jacobsen

Keyword(s):

Sugar Beet ◽

Meloidogyne Incognita ◽

Pythium Ultimum ◽

In Vivo Studies ◽

Damping Off ◽

Root Knot Nematode ◽

Seedling Diseases ◽

Muscodor Albus

A biorational synthetic mixture of organic components mimicking key antimicrobial gases produced by Muscodor albus was equivalent to the use of live M. albus for control of seedling diseases of sugar beet (Beta vulgaris) caused by Pythium ultimum, Rhizoctonia solani AG 2-2, and Aphanomyces cochlioides. The biorational mixture provided better control than the live M. albus formulation for control of root-knot nematode, Meloidogyne incognita, on tomato (Lycopersicon esculentum). The biorational mixture provided control of damping-off equal to a starch-based formulation of the live fungus for all three sugar beet pathogens, and significantly reduced the number of root-knot galls on tomato roots compared with a barley-based formulation. Rate studies with the biorational mixture showed that 2 and 0.75 µl/cm3 of soil were required to provide optimal control of Rhizoctonia and Pythium damping-off of sugar beet, respectively. Five microliters of biorational mixture per milliliter of water was required for 100% mortality in 24 h for Meloidogyne incognita in in vitro studies. In in vivo studies, 1.67 µl of the biorational mixture/cm3 of sand resulted in fewer root-knot galls than a Muscodor albus infested ground barley formulation applied at 5 g/liter of sand.

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Seed Treatment with Ethanol Extract of Serratia marcescens is Compatible with Trichoderma Isolates for Control of Damping-off of Cucumber Caused by Pythium ultimum

Plant Disease ◽

10.1094/pdis-09-15-1039-re ◽

2016 ◽

Vol 100 (7) ◽

pp. 1278-1287 ◽

Cited By ~ 5

Author(s):

Daniel P. Roberts ◽

Dilip K. Lakshman ◽

Laurie F. McKenna ◽

Sarah E. Emche ◽

Jude E. Maul ◽

...

Keyword(s):

Biological Control ◽

Disease Control ◽

Seed Treatment ◽

Sandy Loam ◽

Ethanol Extract ◽

Pythium Ultimum ◽

Damping Off ◽

Integrated Disease Control ◽

Loam Soil ◽

Trichoderma Isolates

Environmentally friendly control measures for soilborne plant pathogens are needed that are effective in different soils when applied alone or as components of an integrated disease control strategy. An ethanol extract of Serratia marcescens N4-5, when applied as a cucumber seed treatment, effectively suppressed damping-off caused by Pythium ultimum in potting mix and in a sandy loam soil. Plant stand associated with this treatment was similar to that of seed treated with the chemical pesticide Thiram in the sandy loam soil. The N4-5 ethanol extract did not consistently provide significant disease control in a loam soil. The N4-5 ethanol extract was compatible with two Trichoderma isolates, not affecting in vitro or in situ colonization of cucumber by these biological control fungi. Control of damping-off of cucumber was never diminished when this ethanol extract was applied as a seed treatment in combination with in-furrow application of the Trichoderma isolates, and disease control was improved in certain instances with these combinations in the loam soil. Data presented here indicate that the N4-5 ethanol extract is compatible with certain beneficial fungi, suggesting that this extract can be used as a component of integrated disease control strategies featuring biological control fungi.

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Mutagenesis of β-1,3-Glucanase Genes in Lysobacter enzymogenes Strain C3 Results in Reduced Biological Control Activity Toward Bipolaris Leaf Spot of Tall Fescue and Pythium Damping-Off of Sugar Beet

Phytopathology ◽

10.1094/phyto-95-0701 ◽

2005 ◽

Vol 95 (6) ◽

pp. 701-707 ◽

Cited By ~ 59

Author(s):

Jeffrey D. Palumbo ◽

Gary Y. Yuen ◽

C. Christine Jochum ◽

Kristin Tatum ◽

Donald Y. Kobayashi

Keyword(s):

Biological Control ◽

Sugar Beet ◽

Tall Fescue ◽

Leaf Spot ◽

Mutational Analysis ◽

Pythium Ultimum ◽

In Vitro Assays ◽

Damping Off ◽

Control Activity ◽

Lysobacter Enzymogenes

Lysobacter enzymogenes produces extracellular lytic enzymes capable of degrading the cell walls of fungi and oomycetes. Many of these enzymes, including β-1,3-glucanases, are thought to contribute to the biological control activity expressed by several strains of the species. L. enzymogenes strain C3 produces multiple extracellular β-1,3-glucanases encoded by the gluA, gluB, and gluC genes. Analysis of the genes indicates they are homologous to previously characterized genes in the related strain N4-7, each sharing >95% amino acid sequence identity to their respective counterparts. The gluA and gluC gene products encode enzymes belonging to family 16 glycosyl hydrolases, whereas gluB encodes an enzyme belonging to family 64. Mutational analysis indicated that the three genes accounted for the total β-1,3-glucanase activity detected in culture. Strain G123, mutated in all three glucanase genes, was reduced in its ability to grow in a minimal medium containing laminarin as a sole carbon source. Although strain G123 was not affected in antimicrobial activity toward Bipolaris sorokiniana or Pythium ultimum var. ultimum using in vitro assays, it was significantly reduced in biological control activity against Bipolaris leaf spot of tall fescue and Pythium damping-off of sugar beet. These results provide direct supportive evidence for the role of β-1,3-glucanases in biocontrol activity of L. enzymogenes strain C3.

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Sensitivity of Rhizoctonia solani AG-2-2 from Sugar Beet to Fungicides

Plant Disease ◽

10.1094/pdis-04-16-0525-re ◽

2016 ◽

Vol 100 (12) ◽

pp. 2427-2433 ◽

Cited By ~ 4

Author(s):

Sahar Arabiat ◽

Mohamed F. R. Khan

Keyword(s):

Sugar Beet ◽

Rhizoctonia Solani ◽

Root Rot ◽

The United States ◽

Damping Off ◽

Growth Assay ◽

The Mean ◽

Crown And Root Rot ◽

Mean Concentration

Rhizoctonia damping-off and crown and root rot caused by Rhizoctonia solani are major diseases of sugar beet (Beta vulgaris L.) worldwide, and growers in the United States rely on fungicides for disease management. Sensitivity of R. solani to fungicides was evaluated in vitro using a mycelial radial growth assay and by evaluating disease severity on R. solani AG 2-2 inoculated plants treated with fungicides in the greenhouse. The mean concentration that caused 50% mycelial growth inhibition (EC50) values for baseline isolates (collected before the fungicides were registered for sugar beet) were 49.7, 97.1, 0.3, 0.2, and 0.9 μg ml−1 and for nonbaseline isolates (collected after registration and use of fungicides) were 296.1, 341.7, 0.9, 0.2, and 0.6 μg ml−1 for azoxystrobin, trifloxystrobin, pyraclostrobin, penthiopyrad, and prothioconazole, respectively. The mean EC50 values of azoxystrobin, trifloxystrobin, and pyraclostrobin significantly increased in the nonbaseline isolates compared with baseline isolates, with a resistant factor of 6.0, 3.5, and 3.0, respectively. Frequency of isolates with EC50 values >10 μg ml−1 for azoxystrobin and trifloxystrobin increased from 25% in baseline isolates to 80% in nonbaseline isolates. Although sensitivity of nonbaseline isolates of R. solani to quinone outside inhibitors decreased, these fungicides at labeled rates were still effective at controlling the pathogen under greenhouse conditions.

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