Nematode assemblages and soil microbial communities in soils associated with glyphosate-resistant soybean

Abstract

The introduction of genetically modified glyphosate-resistant (GR) crops led to increased use of glyphosate, with potential long-term effects on biological soil communities. Abundance and diversity of plant-parasitic and non-parasitic nematodes, as well as microbial community structure in the rhizosphere of GR and conventional soybean (CS) plants as well as native plants (mainly grasses) that grew in natural veld (NV), were investigated during one growing season. No significant differences (p ≥ 0.05) existed between the non-parasitic nematode trophic groups (dominated by bacterivores) and different plant-parasitic nematodes (dominated by the family Hoplolaimidae) that were present in all soils where GR and CS crops were grown or in NV areas. Faunal analysis of non-parasitic nematodes indicated that 83% of the sites contained enriched, but unstructured soil food-webs while 17% were identified as enriched and structured. No significant differences (p ≥ 0.05) existed for microbial community structures among the GR, CS and NV ecosystems with soils from all three primarily dominated by bacteria. Positive relationships were found between nematode trophic groups and their corresponding microbial prey. This emphasises the value of these organisms as indicators of soil quality and also the impact that agricultural practices can have on soil food webs.