Abstract
In order to reduce chemical fertilization and improve the sustainability of common wheat (Triticum aestivum L.) cultivation, maintaining at the same time high production and quality standards, this study investigated the effects of three commercial biofertilizers on rhizosphere bacterial biomass, biodiversity and enzymatic activity, and on plant growth and grain yield in a field trial. The wheat seeds were inoculated with the following aiding microrganisms: (i) a bacterial consortium (Azospirillum spp. + Azoarcus spp. + Azorhizobium spp.); and two mycorrhizal fungal-bacterial consortia, viz. (ii) Rhizophagus irregularis + Azotobacter vinelandii, and (iii) R. irregularis + Bacillus megaterium + Frateuria aurantia, and comparisons were made with noninoculated controls. We demonstrate that all the biofertilizers significantly enhanced plant growth and nitrogen accumulation during stem elongation and heading, but this was translated into only small grain yield gains (+1%–4% vs controls). The total gluten content of the flour was not affected, but in general biofertilization significantly upregulated two high-quality protein subunits, i.e., the 81 kDa high-molecular-weight glutenin subunit and the 43.6 kDa low-molecular-weight glutenin subunit. These effects were associated with increases in the rhizosphere microbial biomass and the activity of enzymes such as β-glucosidase, α-mannosidase, β-mannosidase, and xylosidase, which are involved in organic matter decomposition, particularly when Rhizophagus irregularis was included as inoculant. No changes in microbial biodiversity were observed. Our results suggest that seed-applied biofertilizers may be effectively exploited in sustainable wheat cultivation without altering the biodiversity of the resident microbiome, but attention should be paid to the composition of the microbial consortia in order to maximize their benefits in crop cultivation.
Highlights
The use of microbial inoculants is of strategic interest for their potential to replace chemical fertilizers and pesticides in agricultural systems, and improve environmental sustainability.Plant-aiding microorganisms, often referred to as plant growth-promoting rhizobacteria (PGPR) (Gupta et al, 2015) and arbuscular mycorrhizal fungi (AMF) (Igiehon and Babalola, 2017), interact with plants roots (Hayat et al, 2010) by enhancing growth, mineral nutrition, drought tolerance, and disease resistance (Nadeem et al, 2013).Bacteria can beneficially contribute to plant growth via N2fixation and solubilization of low mobile nutrients
The soil microbial enzymatic activity response allowed us to clearly separate treatments by principal coordinate analysis (PCoA) (Figure 1), which showed that the R-N and R-PK treatments were more distant from the untreated controls (CO)
Two of the biofertilizers studied here, i.e., TN composed of a bacteria consortium (Azospirillum spp. + Azoarcus spp. + Azorhizobium spp.), and R-N, a fungalbacterial consortium (Rhizophagus irregularis + Azotobacter vinelandii), have already been successfully applied in open field by foliar spraying before stem elongation (Dal Cortivo et al, 2017; Dal Cortivo et al, 2018)
Summary
Bacteria can beneficially contribute to plant growth via N2fixation and solubilization of low mobile nutrients. Biological N2-fixation is carried out by various symbiotic and nonsymbiotic bacteria (Shridhar, 2012). Symbiotic PGPR fix atmospheric N2 mainly within plant roots, with many genera involved, such as Rhizobium, Sinorhizobium, Bradyrhizobium, Mesorhizobium, and Azorhizobium. The latter can enter plant roots intercellularly and colonize the xylem of wheat, rice, corn, and other nonlegume crops without forming real symbiotic structures (Cocking, 2003), Azorhizobium caulinodans is known to form both stem and root nodules in Sesbania rostrata (Robertson et al, 1995)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
