Diversity of nifH gene pools in the rhizosphere of two cultivars of sorghum (Sorghum bicolor) treated with contrasting levels of nitrogen fertilizer

Authors

  • Marcia Reed Rodrigues Coelho,

    1. Instituto de Microbiologia Prof. Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
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  • Marjon De Vos,

    1. Instituto de Microbiologia Prof. Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
    2. Molecular Ecology Group, Laboratory of Microbiology, Wageningen Universiteit, Wageningen, The Netherlands
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  • Newton Portilho Carneiro,

    1. EMBRAPA/CNPMS – Empresa Brasileira de Pesquisa Agropecuária, Centro Nacional de Pesquisas de Milho e Sorgo, Sete Lagoas, MG, Brazil
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  • Ivanildo Evódio Marriel,

    1. EMBRAPA/CNPMS – Empresa Brasileira de Pesquisa Agropecuária, Centro Nacional de Pesquisas de Milho e Sorgo, Sete Lagoas, MG, Brazil
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  • Edilson Paiva,

    1. EMBRAPA/CNPMS – Empresa Brasileira de Pesquisa Agropecuária, Centro Nacional de Pesquisas de Milho e Sorgo, Sete Lagoas, MG, Brazil
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  • Lucy Seldin

    1. Instituto de Microbiologia Prof. Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
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  • Editor: Yaacov Okon

Correspondence: Lucy Seldin, Laboratório de Genética Microbiana, Instituto de Microbiologia Prof. Paulo de Góes, Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Bloco I, Ilha do Fundão, Rio de Janeiro, RJ, Brazil. Tel.: +55 21 2562 6741; fax: +55 21 2560 8344; e-mails: lseldin@micro.ufrj.br and lucy@seldin.com.br

Abstract

The diversity of nitrogen-fixing bacteria was assessed in the rhizospheres of two cultivars of sorghum (IS 5322-C and IPA 1011) sown in Cerrado soil amended with two levels of nitrogen fertilizer (12 and 120 kg ha−1). The nifH gene was amplified directly from DNA extracted from the rhizospheres, and the PCR products cloned and sequenced. Four clone libraries were generated from the nifH fragments and 245 sequences were obtained. Most of the clones (57%) were closely related to nifH genes of uncultured bacteria. NifH clones affiliated with Azohydromonas spp., Ideonella sp., Rhizobium etli and Bradyrhizobium sp. were found in all libraries. Sequences affiliated with Delftia tsuruhatensis were found in the rhizosphere of both cultivars sown with high levels of nitrogen, while clones affiliated with Methylocystis sp. were detected only in plants sown under low levels of nitrogen. Moreover, clones affiliated with Paenibacillus durus could be found in libraries from the cultivar IS 5322-C sown either in high or low amounts of fertilizer. This study showed that the amount of nitrogen used for fertilization is the overriding determinative factor that influenced the nitrogen-fixing community structures in sorghum rhizospheres cultivated in Cerrado soil.

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