Influence of nitrogen fertilization on diazotrophic communities in the rhizosphere of the Jerusalem artichoke (Helianthus tuberosus L.).

Abstract Diazotrophsin the soil may be influenced by plant factors as well as nitrogen (N) fertilization. In this study, we investigated potential diazotrophiccommunities in the rhizosphereof the Jerusalem artichoke( Helianthustuberosus L.) supplied with differing amounts of N. The community structure of N 2 -fixing bacteria was profiled using the length heterogeneity polymerase chain reaction (LH-PCR) and terminal restriction fragment length polymorphism(T-RFLP) based on a variation in the nifH gene. Higher numbers of diazotrophswere detected by T-RFLP compared to LH-PCR. The lowest number of N 2 -fixing bacteria was observed in the rhizospheresoil with high N fertilization. T-RFLP was a better method than LH-PCR for profiling microbial diversity of diazotrophsusing multidimensional scaling(MDS) and analysis of similarity (ANOSIM) of fingerprints as well as diversity measures. The supply of N fertilizer appeared to negatively influence the abundance of diazotrophsin the rhizophere of the Jerusalem artichoke.