Herbaspirillum colonization increases growth and nitrogen accumulation in aluminium-tolerant rice varieties

Authors

  • Prasad Gyaneshwar,

    1. Crop, Soil and Water Sciences Division, International Rice Research Institute, MCPO Box 3127, 1271 Makati City, Philippines;
    2. Present address: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
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  • Euan K. James,

    Corresponding author
    1. Centre for High Resolution Imaging and Processing, MSI/WTB Complex, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK;
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  • Pallavolu M. Reddy,

    1. Crop, Soil and Water Sciences Division, International Rice Research Institute, MCPO Box 3127, 1271 Makati City, Philippines;
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  • Jagdish K. Ladha

    1. Crop, Soil and Water Sciences Division, International Rice Research Institute, MCPO Box 3127, 1271 Makati City, Philippines;
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Author for correspondence: Euan K. James Tel: +44 (0)138 234 4741 Fax: +44 (0)138 234 5893 Email: e.k.james@dundee.ac.uk

Summary

  •  Varieties of rice (Oryza sativa) differing in tolerance to aluminium (Al) were evaluated for their N-fixation ability after inoculation with a gusA-marked strain of Herbaspirillum seropedicae Z67.
  •  Under axenic conditions, by 30 d, inoculation resulted in enhanced nitrogenase activity, d. wt, total N and total C content only in the Al-tolerant varieties, and one (cv. Moroberekan) showed significantly more 15N2 incorporation than an Al-sensitive variety (‘IR45’). There were no differences in the number of the bacteria colonizing the different varieties, but the Al-tolerant ones secreted larger amounts of C in their root exudates, and bacteria colonizing the roots of cv. Moroberekan strongly expressed gusA and NifH proteins.
  •  Under glasshouse conditions, by 30 d, inoculation resulted in increased growth of both cvs IR45 and Moroberekan, but the latter showed significantly greater nitrogenase activity and 15N dilution. In a long-term experiment, by 120 d, cv. Moroberekan showed a significant increase in N content after inoculation.
  •  Herbaspirilla were localized on and within roots and aerial parts of cvs Moroberekan and IR45 under both growth conditions. The role of N fixation in growth promotion of rice by H. seropedicae is discussed in terms of availability of C.

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