Glyphosate and glyphosate-resistant crop interactions with rhizosphere microorganisms

Summary

This review synthesises evidence on glyphosate impacts on rhizosphere microorganisms in transgenic glyphosate-resistant crops, drawing on long-term field studies from Missouri (1997–2007). The authors document significant increases in root-colonising Fusarium following glyphosate application to GR soybean and maize, alongside shifts in manganese availability, nodulation, and phytopathogen-antagonistic bacterial interactions. The findings suggest that root-exuded glyphosate may alter microbial community structure and function, with implications for soil health and the need for polyphasic microbial assessment methods to fully evaluate GR crop technologies.

Regional applicability

The study was conducted in the United States (Missouri), so direct applicability to United Kingdom conditions would require consideration of differences in soil type, climate, and cropping systems. However, the findings are relevant to UK policy and practice regarding glyphosate use and adoption of herbicide-resistant crops, particularly in relation to soil health and microbial function assessment, though UK climate and soil conditions may generate different microbial responses.

Key measures

Root colonisation frequency by Fusarium; soil populations of Fusarium and rhizosphere bacteria; manganese transformation; plant-available nutrient status; nodulation rates; phytopathogen-antagonistic bacterial activity

Outcomes reported

The study documented effects of glyphosate applied to glyphosate-resistant soybean and maize on root colonization, soil microbial populations, and specific microbial functions including manganese transformation, phytopathogen-antagonistic bacterial interactions, and nitrogen nodulation. Field assessments measured changes in Fusarium root colonisation and selected rhizosphere bacterial populations across multiple years and sites.

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