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Title Functional diversity and impact of mostly novel nitrogen-fixing bacteria associated with wild plants and crops from Northern regions of Namibia

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Short title Functional diversity of nitrogen-fixing bacteria

Author(s) Burbano, C.; Bahulikar, R.; Demba-Diallo, M.; Hurek, T.; Reinhold-Hurek, B.

Presenting author Reinhold-Hurek, Barbara

Institution(s) General Microbiology, University Bremen, Bremen, Germany

Keywords Nitrogen fixation; Oryza; plant growth promotion; Mopane

Abstract Biological nitrogen fixation (BNF) is in focus of this project as it counterbalances nitrogen losses and improves soil fertility and plant nutrition for a more sustainable land use. Results of the previous project phases suggest that in wild rice, activity of these bacteria and thus contribution to a more sustainable soil use might be particularly high. Oryza longistaminata showed high activity of root-associated diazotrophs and abundant vegetative growth at several sites at the river bank of the Okavango (Namibia), and might be a valuable resource as cattle fodder, for which management for sustainable use should be developed. The robustness of the N2-fixing system towards disturbances such as different flooding levels and cutting were studied with molecular ecological methods that detect abundance and diversity of nitrogenase gene (nifH)-mRNA transcripts. These methods have been improved by the use of LNAs. Water levels were shown to have a strong impact on diversity and activity of root-associated diazotrophs. In agricultural crops in the Kavango area, such as maize, Sorghum bicolor and Pennisetum glaucum, a wide range of putatively plant-growth-promoting endophytic bacteria was isolated that might be used for more sustainable agricultural production. Another underexplored plant system is Mopane (Colophospermum mopane). This legume tree is widely distributed and utilized in Southern Africa on low-fertility soils, however nothing is known about rhizobial nodule symbionts. No nodules were found on small or large trees; however a root zone of active nitrogen fixation was detected below the root surface. This zone might represent a novel type of symbiotic tissue, as the abundantly expressed nitrogenase genes are non-rhizobial.

Congress Topic Microbiology

Topic No. 7.1
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Ref. No. 518