Fluazifop-P-butyl (herbicide) affects richness and structure of soil bacterial communities

Fusilade (fluazifop-P-butyl) is an extensively used herbicide in legumes cropping systems; nevertheless, the extent of its ecological risk remains unknown. The aim of this work is to estimate the impact of this herbicide on some key enzyme activities, namely acid phosphatase, urease and FDA, and the effect on soil bacterial communities in the rhizosphere of pea (Pisum sativum). Acid phosphatase, urease and FDA showed a high decrease following the application of fluazifop-P-butyl mainly at ten-fold field rate. Grain yield was also severely affected at this concentration (−50%). T-RFLP analysis of 16S rDNA revealed a significant effect of fluazifop-P-butyl application on richness and structure of soil bacterial communities. Putative taxonomic assignation of induced TRFs revealed a marked pattern of acidogenic bacteria like as Staphylococcus, Escherichia, Desulfobacter, Clostridium, Paludibacter and other sulfate-reducing bacteria like as Desulfocella halophila and Desulfocurvus vexinensis. These bacteria may participate in the acidogenesis and the production of propionic acid from the fluazifop-P-butyl after hydrolytic cleavage. They are also known to play important roles in the global biogeochemical sulfur cycles. Unfortunately, some potential human pathogens were also stimulated. Moreover, many putative plant-growth-promoting bacteria belonging to the genera Streptomyces and Bacillus were found to be inhibited in the bulk soil and rhizosphere. The fluazifop-P-butyl effect on bacterial diversity was more pronounced in the rhizosphere compared to bulk soil or uncultivated soil which may suggest that a major component of this effect is mediated by the root system.