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Cropping practices modulate the impact of glyphosate on arbuscular mycorrhizal fungi and rhizosphere bacteria in agroecosystems of the semiarid prairie

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Abstract:

A growing body of evidence obtained from studies performed under controlled conditions suggests that glyphosate use can modify microbial community assemblages. However, few studies have examined the influence of glyphosate in agroecosystems. We examined 4 wheat-based production systems typical of the Canadian prairie over 2 years to answer the following question: Does preseeding of glyphosate impact soil rhizosphere microorganisms? If so, do cropping practices influence this impact? Glyphosate caused a shift in the species dominating the arbuscular mycorrhizal fungal community in the rhizosphere, possibly through the modification of host plant physiology. Glyphosate stimulated rhizobacterial growth while having no influence on saprotrophic fungi, suggesting a greater abundance of glyphosate-tolerant 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in bacteria than in fungi. Glyphosate stimulated rhizosphere bacteria in pea but not in urea-fertilized durum wheat, which is consistent with inhibition of EPSPS tolerance to residual glyphosate through high ammonium levels. Mitigation of the effects of glyphosate on rhizosphere bacteria through tillage suggests a reduction in residual glyphosate activity through increased adsorption to soil binding sites upon soil mixing. The influence of glyphosate on Gram-negative bacteria was mitigated under drought conditions in 2007. Our experiment suggests that interactions between soil fertility, tillage, and cropping practices shape the influence of glyphosate use on rhizosphere microorganisms.

Keywords: arbuscular mycorrhiza fungi; champignons mycorhizes arbusculaires; communauté microbienne de la rhizosphère; cropping practices; glyphosate; labour; pratiques culturales; rhizosphere microbial community; tillage

Document Type: Research Article

DOI: http://dx.doi.org/10.1139/w2012-080

Affiliations: 1: Northwest A&F University, Yangling, Shaanxi, 712100, People’s Rebublic of China. 2: Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, Box 1030 Airport Road, Swift Current, SK S9H 3X2, Canada.

Publication date: August 24, 2012

More about this publication?
  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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