Rhizosphere Regulation of Preinfection Behavior of Oomycete Plant Pathogens

Nelson, Eric B.

doi:10.1007/3-540-29420-1_16

Cited by 9 publications

(8 citation statements)

References 164 publications

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“…on May 12, 2018 by guest http://aem.asm.org/ spermosphere but also on the rapid colonization of seeds and seedling surfaces, ultimately resulting in embryo or seedling infection (11). Our results have shown that P. ultimum colonization levels on cucumber seeds are reduced when E. cloacae is active.…”

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confidence: 60%

Differential Interference with Pythium ultimum Sporangial Activation and Germination by Enterobacter cloacae in the Corn and Cucumber Spermospheres

Windstam

Nelson

2008

Appl Environ Microbiol

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Differential protection of plants by Enterobacter cloacae was studied by investigating early sensing and response behavior of Pythium ultimum sporangia toward seeds in the presence or absence of E. cloacae. Ten percent of P. ultimum sporangia were activated within the first 30 min of exposure to cucumber seeds. In contrast, 44% of the sporangia were activated as early as 15 min after exposure to corn seeds with over 80% sporangial activation by 30 min. Germ tubes emerged from sporangia after 2.5 and 1.0 h in the cucumber and corn spermospheres, respectively. Seed application of the wild-type strain of E. cloacae (EcCT-501R3) reduced sporangial activation by 45% in the cucumber spermosphere, whereas no reduction was observed in the corn spermosphere. Fatty acid transport and degradation mutants of E. cloacae (strains EcL1 and Ec31, respectively) did not reduce sporangial activation in either of the spermospheres. Although wild-type or mutant strains of E. cloacae failed to reduce seed colonization incidence, pathogen biomass on cucumber seeds was reduced in the presence of E. cloacae strains EcCT-501R3 and Ec31 by 4 and 8 h after sowing, respectively. By 12 h, levels of P. ultimum on cucumber seeds treated with E. cloacae EcCT-501R3 did not differ from levels on noninoculated seeds. On corn seeds, P. ultimum biomass was not affected by the presence of any E. cloacae strain. When introduced after sporangial activation had occurred, E. cloacae failed to reduce P. ultimum biomass on cucumber seeds compared with that on nontreated seeds. Also, increasing numbers of sporangia used to inoculate seeds yielded increased pathogen biomass at each sampling time. This indicates a direct link between the level of seed-colonizing biomass of P. ultimum and the number of activated and germinated sporangia in the spermosphere, suggesting that E. cloacae suppresses P. ultimum seed infections by reducing sporangial activation and germination within the first 30 to 90 min after sowing.

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confidence: 60%

Differential Interference with Pythium ultimum Sporangial Activation and Germination by Enterobacter cloacae in the Corn and Cucumber Spermospheres

Windstam

Nelson

2008

Appl Environ Microbiol

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“…In view that for small times metastable patterns resemble the stationary states in the zero-diffusion limit, we shall use the stationary solutions (15) and (17). Therefore, the stationary value of c at equilibrium is given by 2c(R 0 ) − δv ∞ (R 0 ).…”

Section: Approximate Equilibrium Solutionsmentioning

confidence: 99%

“…In the same fashion, Figure 8 shows the cross-sections for the concentration v of bacteria. The solid plot (red) shows the plateau (15) with an analytical radius equal to R 1 = 0.0423. The dotted (blue) graph represents the numerically computed plateau with D v = 0 at time t = 9.8039, with radius R 1 = 0.0412.…”

Section: Small Diffusion: 0 < D Vmentioning

confidence: 99%

“…There is strong experimental evidence of zoospore chemotaxis (see, e.g., Islam and Tahara [5]) and of negative zoospore chemotaxis for certain species (see [13,14]). Moreover, it is well documented that amino acids may act as chemo-repellent molecules for certain zoospores (see Nelson [15]). Under such considerations (even though it is not clear whether this biocontrol mechanism is of chemotactic nature alone) we find it reasonable to assume that the inhibition process has a chemotactic component.…”

Section: Introductionmentioning

confidence: 99%

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A Chemotactic Model for Interaction of Antagonistic Microflora Colonies: Front Asymptotics and Numerical Simulations

et al. 2013

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This paper studies a two-dimensional chemotactic model for two species in which one of them produces a chemo-repellent for the other. It is shown asymptotically and numerically how the chemical inhibits the invasion of a moving front for the second species and how stable steady states, which depend on the chemical concentration, can be reached. The results qualitatively explain experimental observations by Swain and Ray [1] showing that colonies of bacteria produce metabolite agents which prevent the invasion of fungi.

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“…P. ultimum has the capacity to rapidly switch from a quiescent state to active growth in the presence of seeds of a suitable host (16). Since P. ultimum spends the greater part of its life cycle as sporangia or oospores in a dormant state in soil, seed exudates are critical in triggering this developmental transition (17,25).…”

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Temporal Release of Fatty Acids and Sugars in the Spermosphere: Impacts on Enterobacter cloacae -Induced Biological Control

Windstam

Nelson

2008

Appl Environ Microbiol

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The aim of this study was to determine the temporal release of fatty acids and sugars from corn and cucumber seeds during the early stages of seed germination in order to establish whether sugars found in exudate can prevent exudate fatty acid degradation by Enterobacter cloacae. Both saturated (long-chain saturated fatty acids [LCSFA]) and unsaturated (long-chain unsaturated fatty acids [LCUFA]) fatty acids were detected in corn and cucumber seed exudates within 15 min after seed sowing. LCSFA and LCUFA were released at a rate of 26.1 and 6.44 ng/min/seed by corn and cucumber seeds, respectively. The unsaturated portion of the total fatty acid pool from both plant species contained primarily oleic and linoleic acids, and these fatty acids were released at a combined rate of 6.6 and 0.67 ng/min/seed from corn and cucumber, respectively. In the absence of seed exudate sugars, E. cloacae degraded linoleic acid at rates of 29 to 39 ng/min, exceeding the rate of total fatty acid release from seeds. Sugars constituted a significant percentage of corn seed exudate, accounting for 41% of the total dry seed weight. Only 5% of cucumber seed exudate was comprised of sugars. Glucose, fructose, and sucrose were the most abundant sugars present in seed exudate from both plant species. Corn seeds released a total of 137 g/seed of these three sugars within 30 min of sowing, whereas cucumber seeds released 0.83 g/seed within the same time frame. Levels of glucose, fructose, and sucrose found in corn seed exudate (90 to 342 g) reduced the rate of linoleic acid degradation by E. cloacae to 7.5 to 8.8 ng/min in the presence of either sugar, leaving sufficient concentrations of linoleic acid to activate Pythium ultimum sporangia Our results demonstrate that elevated levels of sugars in the corn spermosphere can prevent the degradation of LCUFA by E. cloacae, leading to its failure to suppress P. ultimum sporangial activation, germination, and subsequent disease development.

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Rhizosphere Regulation of Preinfection Behavior of Oomycete Plant Pathogens

Cited by 9 publications

References 164 publications

Differential Interference with Pythium ultimum Sporangial Activation and Germination by Enterobacter cloacae in the Corn and Cucumber Spermospheres

Differential Interference with Pythium ultimum Sporangial Activation and Germination by Enterobacter cloacae in the Corn and Cucumber Spermospheres

A Chemotactic Model for Interaction of Antagonistic Microflora Colonies: Front Asymptotics and Numerical Simulations

Temporal Release of Fatty Acids and Sugars in the Spermosphere: Impacts on Enterobacter cloacae -Induced Biological Control

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