Genetics and Molecular Biology of Agrocin Production and Sensitivity in Agrobacterium

Farrand, Stephen K.; Ryder, Maarten H.; O’Morchoe, S. B.; Shim, J.-S.; Kerr, A.

doi:10.1007/978-94-009-3555-6_6

Plant Pathogenic Bacteria

1987

DOI: 10.1007/978-94-009-3555-6_6

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Genetics and Molecular Biology of Agrocin Production and Sensitivity in Agrobacterium

Stephen K. Farrand¹,

Maarten H. Ryder²,

S. B. O’Morchoe³

et al.

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1993

2024

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Cited by 3 publications

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“…for the uptake of both agrocinopines and agrocin 84, which is present on tumor-inducing plasmids of sensitive strains (17,19,20,49). Cells that harbor both pAgK84 and pTi are pathogenic, because of virulence genes present on pTi, and produce and are immune to agrocin 84, because of genes present on pAgK84.…”

mentioning

confidence: 99%

Fate of Agrobacterium radiobacter K84 in the environment

Stockwell

Moore

Loper

1993

Appl Environ Microbiol

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Agrobacterium radiobacter K84 is an effective, commercially applied, biological control agent for the plant disease crown gall, yet little is known about the survival and dissemination of K84. To trace K84 in the environment, spontaneous antibiotic-resistant mutants were used. Growth rates and phenotypes of streptomycinor rifampin-resistant K84 were similar to those of the parental K84, except the rifampin-resistant mutant produced less agrocin 84 as determined by bioassay. K84 and a strain of Agrobacterium tumefaciens established populations averaging 105 CFU/g in the rhizosphere of cherry and persisted on roots for 2 years. K84 established rhizosphere populations between 104 and 106 CFU/g on cherry, ryegrass, and 11 other herbaceous plants. Populations of K84 declined substantially in fallow soil or water over a 16-week period. K84 was detected in the rhizosphere of ryegrass located up to 40 cm from an inoculum source, indicating lateral dissemination of K84 in soil. In gall tissue on cherry, K84 established populations of 105 CFU/g, about 10to 100-fold less than that of the pathogen. These data demonstrate that K84 persists for up to 2 years in a field environment as a rhizosphere inhabitant or in association with crown gall tissue. Agrobacterium radiobacter (Beijerinck and van Delden) Conn K84 is used commercially to control crown gall, a tumorigenic plant disease caused by a ubiquitous soil-borne pathogen, Agrobacterium tumefaciens (41, 42). Losses due to crown gall can be extensive, particularly in the nursery industry, where each galled plant must be culled. Wounds caused by the routine practice of root pruning may be colonized and infected byA. tumefaciens when seedlings are planted in nursery soils infested with the pathogen. During the infection process, A. tumefaciens transfers the T-DNA region of the tumor-inducing plasmid (pTi) into the plant cell (58). Incorporation of T-DNA into the plant genome results in the formation of a hyperplastic growth called a gall. The gall provides a nutrient-rich environment for further bacterial growth. Galls can weaken, reduce the aesthetic quality, and eventually kill the host plant. There are no effective chemical controls currently available for crown gall. Strain K84 has demonstrated remarkable and widespread success as an agent for the biological control of crown gall (40). K84 has been used commercially for more than a decade in many regions of the world, including Australia,

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Fate of Agrobacterium radiobacter K84 in the environment

Stockwell

Moore

Loper

1993

Appl Environ Microbiol

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Effect of Antibiosis on Antagonist Dose-Plant Disease Response Relationships for the Biological Control of Crown Gall of Tomato and Cherry

Johnson¹,

DiLeone²

1999

Phytopathology®

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The crown gall pathosystem was used to evaluate a model that describes the dose-response relationship between biological control agents and plant pathogens. The model predicts that this relationship can become asymptotic, such that increased antagonist doses cannot compensate for deficiencies in disease suppression. Wounded roots of tomato (Lycopersicon esculentum) and cherry (Prunus mahaleb) plants were dipped into different concentrations of the biological control organism Agrobacterium radiobacter strain K84 prior to inoculation with the pathogen A. tumefaciens. Pathogen strains sensitive or resistant to the antibiotic agrocin 84 were used, and for tomato experiments, a derivative of A. radiobacter strain K84 that does not produce agrocin 84 also was included as an experimental treatment. As predicted by the dose-response model, the amount of disease suppression per unit of antagonist decreased with increasing antagonist dose and became asymptotic at high antagonist densities. Control of crown gall of tomato was nearly complete with the combination of A. radiobacter K84 and an agrocin 84-sensitive strain of A. tumefaciens. Pathogen resistance to agrocin 84 or lack of agrocin 84 production by A. radiobacter resulted in antagonist dose-crown gall incidence relationships that were apparently asymptotic at levels of control significantly less than 100%. For field-grown cherry, similar dose-response relationships were observed with higher asymptotic levels of disease suppression obtained when trees were inoculated with an agrocin 84-sensitive A. tumefaciens strain compared with an agrocin 84-resistant pathogen strain. The differences among bacterial strain combinations in the magnitude of the asymptote defined by the dose-response relationships suggest that A. radiobacter impacts a smaller proportion of the pathogen population when the activity of agrocin 84 is muted.

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Evaluation of Chemical and Biological Products for Control of Crown Gall on Rose

Oksel,

Liyanapathiranage,

Parajuli

et al. 2024

Pathogens

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Crown gall is a soil-borne bacterial disease caused by Agrobacterium tumefaciens, leading to significant economic losses in many plant species. For the assessment of the biological and chemical products on crown gall, each plant’s crown region and roots were wounded, and then were dipped into their respective treatments. After the treatments, the plants were inoculated with a suspension of pathogenic A. tumefaciens isolate FBG1034 and maintained in a greenhouse for six months to assess them for gall formation. A quantitative real-time PCR assay was performed to quantify the A. tumefaciens using the chvE gene. Biological products such as the Agrobacterium radiobacter strain K1026, and strains 1 and 2, resulted in the lowest average root gall diameter and significantly reduced the crown gall diameter to stem diameter ratio, and the chemical product copper octanoate reduced the number of crown and root galls as well as the crown and root gall diameter compared to the inoculated, non-treated control. Moreover, both the A. radiobacter strain K1026 and strain 1 treatments resulted in an approximately 85% and 65% reduction in crown and root gall incidence, respectively, in both of the trials compared to the inoculated, non-treated plants. The findings of this study indicate that the use of biological and chemical products could help to suppress crown and root gall disease in rose plants.

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Genetics and Molecular Biology of Agrocin Production and Sensitivity in Agrobacterium

Cited by 3 publications

References 22 publications

Fate of Agrobacterium radiobacter K84 in the environment

Fate of Agrobacterium radiobacter K84 in the environment

Effect of Antibiosis on Antagonist Dose-Plant Disease Response Relationships for the Biological Control of Crown Gall of Tomato and Cherry

Evaluation of Chemical and Biological Products for Control of Crown Gall on Rose

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