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Soil properties, seasonality and crop growth stage exert a stronger effect on rhizosphere prokaryotes than the fungal biocontrol agent Fusarium oxysporum f.sp. strigae.

Authors
  • Musyoki, Mary K1
  • Cadisch, Georg1
  • Zimmermann, Judith1
  • Wainwright, Henry2
  • Beed, Fen3
  • Rasche, Frank1
  • 1 Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, Stuttgart, Germany. , (Germany)
  • 2 The Real IPM Company, P.O. Box 4001-01002, Madaraka, Thika, Kenya. , (Kenya)
  • 3 AVRDC-The World Vegetable Center, East and Southeast Asia, P.O. Box 1010 (Kasetsart), Bangkok 10903, Thailand. , (Thailand)
Type
Published Article
Journal
Applied Soil Ecology
Publisher
Elsevier
Publication Date
Sep 01, 2016
Volume
105
Pages
126–136
Identifiers
DOI: 10.1016/j.apsoil.2016.03.021
PMID: 31007391
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Fusarium oxysporum f.sp. strigae (Fos) is an effective biocontrol agent (BCA) against the parasitic weed Striga hermonthica. It acts in the rhizosphere of several tropical cereals, where it may interfere with indigenous microbial populations. To test this impact, we assessed in a 2-season field experiment at two contrasting tropical agro-ecological sites the response of nitrifying and total indigenous prokaryotic communities in the rhizosphere of maize to the exposure of the Fos-BCA "Foxy-2". At early leaf development (EC30), flowering (EC60) and senescence (EC90) stage of maize, rhizosphere samples were obtained and subjected to community analysis of bacterial and archaeal amoA (ammonia monooxigenase) (AOB, AOA) and 16S rRNA genes. Abundance and community composition of all studied genes were predominantly influenced by soil type, crop growth stage and seasonality. No major effect of "Foxy-2" was found. Notably, total archaeal community relative to bacteria dominated in the clayey soil which was linked to its strong soil organic carbon (SOC) background. Compared to bacterial nitrifiers, domination of nitrifying archaea increased towards senescence stage which was explained by biochemical differences in organic resource availability between the crop growth stages. During the short rain season, the higher archaeal abundance was mainly driven by increased availability of organic substrates, i.e., extractable organic carbon. Our findings suggested that archaea had greater rhizosphere competence than "Foxy-2" in soils with higher clay and SOC contents. We verified that "Foxy-2" in maize rhizospheres is compatible with nitrifying prokaryotes under the given environments, in particular in clayey soils dominated by archaea.

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