Phosphorus fertilizer responsive bacteria and fungi in canola (Brassica napus L.) roots are correlated with plant performance

Abstract

Background Canola (Brassica napus L.) has high phosphorus demand, but its seedlings are sensitive to seed-placed phosphorus fertilizers. Optimizing phosphorus fertilizer managements (rates and placements) for canola is critical and can be aided by a better understanding of the root-associated microbiome, as it plays key roles in improving phosphorus availability through mineralization and solubilization. Methods We conducted a two-year field experiment applying monoammonium phosphate fertilizers at three rates (no addition, recommended, and high rates at 0, 17, and 32 kg P ha− 1 year− 1) using two opener placements (narrow at 2.5 cm vs. wide at 10 cm) which affect seedbed concentration of phosphorus. Canola performance was evaluated, and rhizosphere and root bacterial and fungal microbiomes were profiled by DNA amplicon sequencing. Results High-rate and near-seed placement of phosphorus (32 kg P ha− 1 in the 2.5 cm opener) consistently reduced canola seedling emergence but not biomass and yield, which were higher in 2020 than in 2019. Yearly variations and plant growth stages impacted both the rhizosphere and root microbiomes, while phosphorus fertilization only affected the root microbiome. Specifically, phosphorus fertilization enriched root genera Burkholderia-Caballeronia-Paraburkholderia, Luteibacter, Amaurodon, Trichoderma, and Penicillium. Conversely, Chryseobacterium, Chitinophaga, Flavobacterium and Olpidium were more prevalent in roots without phosphorus addition. Canola yield was positively correlated with the abundance of Burkholderia-Caballeronia-Paraburkholderia and Trichoderma in roots. Conclusions Phosphorus fertilizer rates and placements affect canola germination but not seed yield. Profiling of phosphorus-responsive bacteria and fungi in the roots suggests that phosphorus fertilization can have a lasting impact on the canola root microbiome, modulating plant growth responses to soil phosphorus availability.