Efficacy of native antagonistic bacterial isolates in biological control of crown gall disease in Egypt

Agrobacterium vitis is the causal agent of crown gall disease in grapevine, which can be severe in many regions worldwide. Vitis vinifera cultivars are highly susceptible to freeze injury, providing the wounds necessary for infection by A. vitis. Wound position in relation to the uppermost bud of cuttings was determined to be important in tumor development. Inoculated wounds below buds developed tumors, whereas wounds opposite the bud did not, implying that indole-3-aectic acid flow contributes to tumor formation. If auxin was applied to wounds prior to inoculation with a tumorigenic A. vitis strain, all sites of inoculation developed tumors, accompanied by an increased amount of callus in the cambium. Wounds inoculated with an A. vitis biological control strain F2/5 prior to application of the pathogen did not develop galls. A closer examination of these wounds determined that callus cells formed in the cambium during wound healing are susceptible to transformation by the pathogen. Although the mechanism by which F2/5 prevents transformation is unknown, our observations suggest that F2/5 inhibits normal wound healing by inducing necrosis in the cambium.

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Complete Genome Sequence Data of Nonpathogenic Strain Rhizobium vitis VAR03-1, a Biological Control Agent for Grapevine Crown Gall Disease

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-07-20-0181-a ◽

2020 ◽

Vol 33 (12) ◽

pp. 1451-1453

Author(s):

Yoshiteru Noutoshi ◽

Atsushi Toyoda ◽

Tomoya Ishii ◽

Kirara Saito ◽

Megumi Watanabe ◽

...

Keyword(s):

Biological Control ◽

Genome Sequence ◽

Crown Gall ◽

Complete Genome ◽

Sequence Data ◽

Biological Control Agent ◽

Suppressive Effect ◽

Control Agent ◽

Crown Gall Disease ◽

Nonpathogenic Strain

Crown gall disease in grapevine is caused by pathogenic strains of Rhizobium vitis with a tumor-inducing (Ti) plasmids. A nonpathogenic strain, VAR03-1 of R. vitis, has been isolated from the grapevine root of nursery stock and it was shown to act as a biological control agent to crown gall disease. Its disease-suppressive effect was observed even when it was coinoculated with the pathogen in a 1:1 ratio. Here, we present the complete genome data of R. vitis VAR03-1, assembled by sequencing reads obtained by both PacBio and Illumina technologies with annotation. This genome sequence could contribute to investigations of the molecular basis underlying the biocontrol activity as well as the root-colonization ability of this bacterial strain. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

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Construction of a Range of Derivatives of the Biological Control Strain Agrobacterium rhizogenes K84: a Study of Factors Involved in Biological Control of Crown Gall Disease

Applied and Environmental Microbiology ◽

10.1128/aem.64.10.3977-3982.1998 ◽

1998 ◽

Vol 64 (10) ◽

pp. 3977-3982 ◽

Cited By ~ 20

Author(s):

Nicholas C. McClure ◽

Ali-Reza Ahmadi ◽

Bruce G. Clare

Keyword(s):

Biological Control ◽

Agrobacterium Rhizogenes ◽

Crown Gall ◽

Biological Control Agent ◽

Control Process ◽

Dry Weight ◽

Control Strain ◽

Crown Gall Disease ◽

Derivatives Of

ABSTRACT The biological control strain Agrobacterium rhizogenesK84 is an effective agent in the control of Agrobacteriumpathogens, the causative agents of crown gall disease. A number of factors are thought to play a role in the control process, including production of the specific agrocins 84 and 434, which differ in the spectra of pathogenic strains that they inhibit in vitro. A range of derivatives of strain K84 has been developed with every combination of the three resident plasmids, pAgK84, pAgK434, and pAtK84b, including a plasmid-free strain. These derivatives produced either both, one, or neither of the characterized agrocins 84 and 434 and were isolated by plasmid curing, conjugation, and Tn5 transposon mutagenesis. The ability of the derivative strains to inhibit gall formation on almond roots was compared to that of the wild-type K84 parent. Treatment with the plasmid-free derivative did not result in a significant level of control of an A. rhizogenes pathogen based on numbers or dry weight of galls formed on injured almond roots. The presence of plasmid pAgK84, pAgK434, or pAtK84b significantly enhanced the biological control efficacy of K84 derivatives, and the highest level of control was observed with strains harboring two or more plasmids. The results observed with strains deficient in agrocin 434 production suggest that this product may play an important role in the biological control of A. rhizogenes pathogens. The involvement of plasmid pAgK84b in biological control has not previously been reported. This study supports the conclusion that multiple factors are involved in the success of strain K84 as a biological control agent.

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