Effects of amendments of ferulic acid on soil microbial communities in the rhizosphere of cucumber (Cucumis sativus L.)

Phenolic compounds are secondary metabolites often implicated in allelopathic interactions. However, how these compounds would affect soil microbial communities is not yet fully understood. In this experiment, effects of amendments of ferulic acid on soil dehydrogenase activity, microbial biomass carbon (MBC) content, and bacterial and fungal community structures and abundances in the rhizosphere of cucumber were evaluated. Polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and real-time PCR, on bacterial 16S rRNA genes or fungal ITS regions, were used to analyze bacterial and fungal community structures and sizes, respectively. Results showed that amendments of ferulic acid inhibited cucumber seedling growth, and stimulated soil dehydrogenase activity, MBC content, and bacterial and fungal community sizes. Amendments of ferulic acid also changed rhizosphere bacterial and fungal community structures. Bacterial and fungal communities responded differently to the ferulic acid amendment: numbers of visible bands and diversity indices of microbial community were lower in ferulic acid-amended soils than in the unamended soil for bacterial community, while were higher for fungal community. Overall, our results suggested that ferulic acid might account for the autotoxicity of cucumber through changing soil microbial communities. (C) 2012 Elsevier Masson SAS. All rights reserved.