Colonization of the developing rhizosphere of sugar beet seedlings by potential biocontrol agents applied as seed treatments

Walker, Richard B.; Rossall, S.; Asher, M. J. C.

doi:10.1046/j.1365-2672.2002.01523.x

Cited by 21 publications

(15 citation statements)

References 25 publications

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“…A similar gradient of colonization has been observed in the sugar beet rhizosphere for different rifampicin-resistant mutants of Arthrobacter histidinolovorans, Bacillus megaterium, Cytophaga johnsonae, P. fluorescens, and P. syringae by Walker et al (2002). After germination of the seeds, the abundance of the bacteria increased rapidly by three to five orders of magnitude.…”

Section: Discussionsupporting

confidence: 73%

Strain-specific colonization pattern of Rhizoctonia antagonists in the root system of sugar beet

Zachow¹,

Fatehi²,

Cardinale³

et al. 2010

FEMS Microbiology Ecology

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To develop effective biocontrol strategies, basic knowledge of plant growth promotion (PGP) and root colonization by antagonists is essential. The survival and colonization patterns of five different biocontrol agents against Rhizoctonia solani AG2-2IIIB in the rhizosphere of greenhouse-grown sugar beet plants were analysed in single and combined treatments. The study included bacteria (Pseudomonas fluorescens L13-6-12, Pseudomonas trivialis RE(*) 1-1-14, Serratia plymuthica 3Re4-18) as well as fungi (Trichoderma gamsii AT1-2-4, Trichoderma velutinum G1/8). Microscopic analysis by confocal laser scanning microscopy revealed different colonization patterns for each DsRed2/green fluorescent protein-labelled strain. Bacteria and T. velutinum G1/8 colonized the root surface and the endorhiza in single and co-culture, while for T. gamsii AT1-2-4, only the transfer of spores was observed. Whereas Pseudomonas strains formed large microcolonies consisting of hundreds of cells, S. plymuthica was arranged in small endophytic clusters or clouds around the entire root system. In co-culture, each strain showed its typical pattern and occupied specific niches on the root, without clear evidence of morphological interactions. PGP was only observed for four strains with rhizosphere competence and not for T. gamsii AT1-2-4. The results provide useful information on which combination of strains to test in larger biocontrol experiments directed to applications.

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Section: Discussionsupporting

confidence: 73%

Strain-specific colonization pattern of Rhizoctonia antagonists in the root system of sugar beet

Zachow¹,

Fatehi²,

Cardinale³

et al. 2010

FEMS Microbiology Ecology

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“…It has previously been shown that bacteria could colonize plant surfaces, such as roots and leaves, often by forming aggregates or microcolonies (Assmus et al 1995;Dandurand et al 1997;von der Weid et al 2005). Different biocontrol strains are known to colonize different regions of plants (Tombolini et al 1999;Ramos et al 2000;Walker et al 2002). We observed that GFP-tagged B. subtilis N11 introduced into soil could be found as aggregates attached to the surface of plant roots after inoculation.…”

Section: Discussionmentioning

confidence: 57%

A new bioorganic fertilizer can effectively control banana wilt by strong colonization with Bacillus subtilis N11

Zhang

et al. 2011

Plant Soil

172

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Fusarium wilt is one of the most serious diseases caused by a soil-borne pathogen affecting banana production. The goal of this study was to evaluate the capability of a novel bio-organic fertilizer (BIO2) that integrated the biocontrol agent Bacillus subtilis N11, and mature composts to control Fusarium wilt of banana in pot experiments. The results showed that the application of the BIO2 significantly decreased the incidence rate of Fusarium wilt compared to the control. To determine the antagonistic mechanism of the strain, we also studied the colonization of the natural biocontrol agent on banana roots using a GFP marker. The studies were performed in a hydroponic culture system, a sand system and a natural soil system. The results indicated that the bacteria colonized predominantly by forming biofilms along the elongation and differentiation zones of the roots. The fact that similar observations were obtained in all three systems suggests that colonization by N11 can be studied in a defined system. The population of B. subtilis N11 in the rhizosphere and on banana roots was also monitored. We speculate that the colonization pattern of B.subtilis N11 can be linked to the mechanism of protection of plants from fungal infection.

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“…As for fungicide seed treatments, the discovery of a single broadspectrum biological control agent active against all 3 major soilborne pathogens of beets is unlikely. In addition, poor colonisation of the rhizosphere by the biological control agent is a major constraint of seed treatment biological control (Walker et al 2002).…”

Section: Control Of the Soilborne Pathogens Of Beet Pre-planting Treamentioning

confidence: 99%

Management of soilborne diseases of beetroot in Australia: a review

Martin¹

2003

Aust. J. Exp. Agric.

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Soilborne fungal diseases threaten the viability of the Australian processing beetroot industry. Globally, Pythium spp., Aphanomyces cochlioides and Rhizoctonia solani are the predominant soilborne fungal pathogens responsible for a root rot complex in beet crops. In Australia, the disease problems have been exacerbated in recent years because crops are now grown virtually year round, and under environmental conditions favourable to infection. This has lead to increased inoculum levels in soils sown to beetroot. Moreover, nowhere in the world does there seem to be a single strategy that is completely efficacious in controlling these pathogens, so an effective management strategy will almost certainly involve a combination of tactics. The most likely combination seems to involve fungicide seed treatments, rotations of gramineous or biofumigant crops and the use of disease-resistant varieties of beet. The first of these, fungicidal seed dressings, are a cost-effective means of reducing pathogen inoculum and protecting young beets from infection. Hymexazol may be particularly useful in the Australian system, since it is active against both Pythium and Aphanomyces. To combat Rhizoctonia, it should be applied in combination with either pencycuron or toclophos methyl. Second, rotations of gramineous crops, such as maize or oats, or biofumigant brassica crops, such as white mustard, brussel sprouts or cabbage should also reduce the build-up of inoculum and offers a tactic to relieve the problem in the longer term. Third, alternative beetroot cultivars with resistance to Rhizoctonia have now been developed in USA breeding programs and should be considered by the Australian industry. Resistant varieties are potentially very useful since they offer a long-term approach to disease management that can be easily incorporated into existing production systems. Fourth, the alteration of sowing dates to avoid periods of high disease risk (e.g. confining sowing to the cooler, drier months) needs to be seriously considered by the Australian industry if it is committed to disease management. There is also evidence to suggest that seed priming may warrant consideration as a tool to use in combination with fungicide dressings to reduce disease in young plants. Biological seed treatments and soil fumigation appear to be tactics of limited value to the Australian beet industry.

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Colonization of the developing rhizosphere of sugar beet seedlings by potential biocontrol agents applied as seed treatments

Cited by 21 publications

References 25 publications

Strain-specific colonization pattern of Rhizoctonia antagonists in the root system of sugar beet

Strain-specific colonization pattern of Rhizoctonia antagonists in the root system of sugar beet

A new bioorganic fertilizer can effectively control banana wilt by strong colonization with Bacillus subtilis N11

Management of soilborne diseases of beetroot in Australia: a review

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