Effects of inoculation of wheat (Triticum aestivum) with rhizosphere bacteria in Victoria, Australia

Abstract

Context: Wheat (Triticum aestivum) is an important food crop around the world. Its value depends on high grain yield and high protein content, which requires large inputs of nitrogenous fertiliser. Aims: The aim of this study was to test if inoculation with a N2-fixing bacterium could improve wheat yield and/or protein content. Method: RMBMTa1 bacteria were isolated from soil in a wheat field at Horsham, Victoria, Australia. Wheat was inoculated with this bacterium in pot and field experiments with three factors: (1) one treatment of N2-fixing bacterium with isolate RMBMTa1; (2) two N treatments (ammonium sulfate, AS; urea); and (3) four N fertiliser rates (1, 50, 100, 150 kg ha−1). Key results: RMBMTa1 was closest (93%) to Paraburkholderia species based on 16S sequencing. In the pot trial, inoculated treatments had the greatest grain dry weight with 100 kg ha−1AS, potentially doubling profit per hectare. In a field trial during a drought year, inoculation reduced grain weight by 9% but increased grain protein by 50%, with a maximum at 100 kg ha−1AS, thus increasing its grading. Conclusions: Inoculating with RMBMTa1 increased both grain yield and protein content when rainfall did not limit yield. Larger-scale coordinated trials of inoculation of wheat varieties with other such native bacteria are needed to test if they offer similar benefits across a range of farming conditions. Implications: RMBMTa1 could potentially increase the value of the wheat crop while saving on input costs and pollution from nitrogenous fertiliser.