Selektion der Soja und deren Symbiosepartner auf Kühletoleranz und Effizienz der biologischen Stickstoff-Fixierung

Summary

In Central Europe low temperature is limiting soybean growth and biological nitrogen fixation (BNF). The BNF efficiency was shown to increase with bradyrhizobia strains selected for their cold tolerance. Significant bradyrhizobia x soybean variety interactions were reported. Co-inoculation with arbuscular mycorrhiza fungi (AMF) may promote bradyrhizobia and improve plant phosphorus uptake. The aim of this study is to identify (i) bradyrhizobia showing improved nodulation under cool conditions, (ii) bradyrhizobia x soybean variety and (iii) bradyrhizobia x AMF interactions. In 2011 twelve bradyrhizobia inoculants were tested with three soybean (Glycine max [L.]) varieties under three temperature regimes (14/10°C, 16/12°C, 22/20 °C) in a pot trial. In 2012 the five most promising bradyrhizobia were inoculated on twenty soybean varieties and an additional trial testing co-inoculated bradyrhizobia and AMF strains was conducted. A significant bradyrhizobia x temperature interaction was found for the number of nodules per plant and the SPAD values (indirect chlorophyll measurement; p ≤ 0,001). Significant bradyrhizobia x variety interactions were observed (p ≤ 0,01). The present results show that the selection of cold tolerant inoculants is as important as adapted soybean varieties. The efficiency of single bradyrhizobia x soybean variety combinations depends on the temperature regime.