Microbiological factors affecting the colonisation of soil aggregates by Fusarium oxysporum f. sp. raphani

Koki Toyota, Karl Ritz, Iain M. Young

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24 Scopus citations


To elucidate factors that affect the colonization of soil aggregates by Fusarium oxysporum f. sp. raphani PEG-4 (hereafter PEG-4), microcosms were designed which comprised a row of three soil aggregates 4 6 mm dia. placed 2 mm apart on silicone rubber podia. The central aggregate was sterile and inoculated with PEG-4. The lateral aggregates were non-sterile or treated in various ways to affect their microbiological status. Following incubation, propagule populations of PEG-4 in the lateral aggregates were enumerated. The degree to which PEG4 colonized non-sterile aggregates was less than 1% of the control (sterile aggregates). When non-sterile aggregates were dried to 200 kPa or antibiotics were added to them to inhibit bacteria, colonization by PEG-4 did not differ greatly from the control, suggesting that the suppressing factors might be of fungal origin. That PEG-4 colonized chloroform-fumigated aggregates, where there was a relative abundance of bacteria supported this hypothesis. In addition sterile aggregates which had been colonized by a range of soil fungi generally inhibited PEG-4 to a greater extent than aggregates which had been colonized by single strains of bacteria. The fungal strains that showed the greatest resistance to the establishment of PEG-4 were closely related to it (F. oxysporum f. sp. raphani, F. nivale, F. oxysporum f. sp. cucumerinum). An antibiotic-producing bacteria, Burkholdier cepacia MRT 11, was also effective at inhibiting PEG-4. Outcomes of interactions between PEG-4 and the other microbes on agar plates were poorly correlated with the outcomes in the aggregate system. We suggest that such aggregate-based systems may be useful in screening putative biocontrol agents since they are soil-based and effects can be readily assessed.
Original languageEnglish (US)
Pages (from-to)1513-1521
Number of pages9
JournalSoil Biology and Biochemistry
Issue number10-11
StatePublished - Jan 1 1996
Externally publishedYes

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Generated from Scopus record by KAUST IRTS on 2023-02-15

ASJC Scopus subject areas

  • Soil Science
  • Microbiology


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