Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 445690
Title Oligotrophic bacteria and root disease suppression in organically managed soils
Author(s) Senechkin, I.V.
Source University. Promotor(en): Ariena van Bruggen, co-promotor(en): Leo van Overbeek. - Wageningen : Wageningen University - ISBN 9789461738035 - 141
Department(s) Biological Farming Systems
Biointeracties and Plant Health
PE&RC
Publication type Dissertation, internally prepared
Publication year 2013
Keyword(s) bodempathogenen - plantenziekteverwekkers - thanatephorus cucumeris - fusarium oxysporum - bodembacteriën - bodembeheer - biologische landbouw - linum usitatissimum - vlas - modellen - bodemweerbaarheid - soilborne pathogens - plant pathogens - soil bacteria - soil management - organic farming - flax - models - soil suppressiveness
Categories Cultural Control
Abstract

The objective of this thesis was to obtain a better understanding of soil health in terms of microbial and chemical characteristics as well as suppression of soil borne plant pathogens. Organic soils were chosen as an appropriate model for studying soil health. Four different organic amendments were applied on two experimental fields with different crop history, providing a diverse range of soil quality levels. Many soil microbial variables were measured, including copiotrophic and oligotrophic bacterial populations, the abundance and diversity of Eubacteria, Alphaproteobacteria, Pseudomonas and fungal communities, as well as several microbial genes involved in nitrogen cycling. Plant disease suppressiveness was used as a quantitative integrative parameter reflecting the health status of soils. Rhizoctonia solani on beet and Fusarium oxysporum on flax were selected as pathosystems; areas under disease progress curves were measured in bioassays with differentially amended field soils and were related to soil parameters. Combined rather than single amendments enhanced Fusarium suppression, but Rhizoctonia suppression was more related to crop history than organic amendments. No universal correlations were found between disease suppression and microbial and chemical parameters, although pH and organic matter affected microbial communities and Fusarium wilt. A significant relation between ammonia oxidizing bacteria and disease suppression was observed for both pathogens; this relation was likely indirect via nitrogen availability and pH. No direct relationship was found between quantities of N cycling genes and disease suppression. A specific emphasis was put on the potential role of oligotrophic bacteria in soil health and disease suppression. Bacteria isolated on low carbon medium (10 mg C/L) were repeatedly transferred onto this medium to select true oligotrophic bacteria. Most isolates could grow on both low carbon and higher carbon (1000 mg C/L) media and belonged to Streptomyces, Rhizobium, Bradyrhizobium and Mesorhizobium. A new oligotrophic isolate was identified as Collimonas sp. IS343 and its interaction with R. solani was studied. This strain was better adapted to oligotrophic conditions than a copiotrophic Collimonas reference strain and was more effective in controlling R. solani. This thesis provided a better understanding of some aspects of soil health and emphasized the role of oligotrophic bacteria, a poorly understood but very important group of soil inhabitants.

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