Co-inoculation and inoculation methods of plant growth-promoting bacteria in wheat yield performance

Abstract

Several studies have reported the beneficial effects of inoculation of Azospirillum brasilense in wheat, but only a few of them have related the co-inoculation of A. brasilense and Rhizobium sp. and the evaluation of different inoculation methods. This study aimed i) to verify the efficiency of plant growth-promoting bacteria (PGPB) in subtropical environments, ii) to verify the efficiency of co-inoculation of A. brasilense and Rhizobium sp., and iii) to verify the efficiency of the management of different inoculation methods in the wheat crop. The experiments were carried out in Londrina and Apucarana, State of Paraná, Brazil, under a complete randomized block design, with four replications and nine treatments: T1) absence of nitrogen (N) topdressing, T2) 30 kg ha−1 of N topdressing, T3) 60 kg ha−1 of N topdressing, T4) A. brasilense Ab-V5 in the seeds, T5) A. brasilense Ab-V5 in post-emergence, T6) A. brasilense Ab-V5 + Rhizobium sp. 53GRM1 in the seeds, T7) A. brasilense Ab-V5 + Rhizobium sp. 53GRM1 in post-emergence, T8) commercial inoculant (A. brasilense Ab-V5 + Ab-V6) in the seeds, and T9) commercial inoculant (A. brasilense Ab-V5 + Ab-V6) in post-emergence. The number of ears per linear meter, number of spikelets, number of grains per spikelet, number of grains per ear, thousand-grain weight, number of spikelets to ears ratio, leaf nitrogen content, and grain yield were evaluated. Leaf N content and yield components showed no alterations due to the inoculation and co-inoculation performed both in the seed and in the post-emergence of seedlings. Treatments T3, T7, and T9 showed the highest means of grain yield (2077.50, 1743.12, and 1660.62 kg ha−1, respectively), demonstrating that co-inoculation with A. brasilense Ab-V5 + Rhizobium sp. 53GRM1 and inoculation with A. brasilense Ab-V5 + Ab-V6, both in post-emergence of seedlings, have the potential to replace the topdressing nitrogen fertilization in wheat.