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 management for canola is critical and can benefit from insights into the root-associated microbiota, which enhances phosphorus availability through mineralization and solubilization.

Methods

We conducted a two-year field experiment applying monoammonium phosphate fertilizer at three rates (no addition, recommended rate, and high rate 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). Canola performance was evaluated, and rhizosphere and root bacterial and fungal microbiota was 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) reduced canola seedling emergence but not biomass or yield, which were higher in 2020 than in 2019. Yearly variations and plant growth stages impacted the rhizosphere and root microbiota, while phosphorus fertilization only affected the root microbiota. Phosphorus fertilization enriched Burkholderia-Caballeronia-Paraburkholderia, Luteibacter, Amaurodon, Trichoderma, and Penicillium in roots, Conversely, Chryseobacterium, Chitinophaga, Flavobacterium and Olpidium were more prevalent in roots without phosphorus addition. Yield positively correlated with the relative abundance of Burkholderia-Caballeronia-Paraburkholderia and Trichoderma in roots.

Conclusions

Phosphate fertilizer rates and placements affected canola germination but not yield. Profiling of phosphorus-responsive root microbes suggests that phosphate fertilizer rate and placement at seeding can have a lasting impact on the canola root microbiota as the plant matures, modulating plant growth responses to soil phosphorus availability.