Effects of Seed-Applied Biofertilizers on Rhizosphere Biodiversity and Growth of Common Wheat (Triticum aestivum L.) in the Field

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 b-glucosidase, a-mannosidase, bmannosidase, 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.

The Status of Soil Microbiome as Affected by the Application of Phosphorus Biofertilizer: Fertilizer Enriched with Beneficial Bacterial Strains

“…Rhizosum PK ® is a biofertilizer containing i.a. Bacillus megaterium and Frateuria aurantia which were found to exhibit potassium-mobilizing properties [49][50][51]. A study conducted by Mengual et al [52] showed that the introduction of microbial inoculants to the soil positively the affected activities of urease, protease and β-glucosidase with significant changes occurring in the case of urease and protease.…”

Improvement of Soil Microbial Diversity through Sustainable Agricultural Practices and Its Evaluation by -Omics Approaches: A Perspective for the Environment, Food Quality and Human Safety

“…However, several biotic and abiotic factors may impact on the ability of plant-aiding microorganisms to successfully colonize the rhizosphere. Therefore, PGPM should tolerate nutrient- or water-limited conditions, be affine for root exudates, and compete with the resident rhizobacteria by secreting antibiotics [ 76 ]. For instance, [ 74 , 115 ] investigated the action of plant-derived protein hydrolysates (PHs) biostimulant and the effects of the mycorrhizal inoculation on morpho-physiological traits and metabolic profile of tomato and durum wheat respectively, grown under limited water availability.…”

“…Recent studies have investigated the effects on the rhizosphere microbial communities of different types of microbial consortia (consisting of PGPRs alone or in association with AMFs) and biostimulant substances coated on crop seeds. All microbial consortia and biostimulant substances significantly enhance plant growth and nitrogen accumulation in wheat and maize, without affecting the endogenous microbial diversity or the composition of the rhizospheric microbial community, rather stimulating rare bacterial taxa, some of which involved in plant growth and pathogen resistance [ 61 , 76 , 81 ]. This suggests that seed-applied biofertilizers may be exploited effectively in sustainable cultivation.…”

“…In this regard, the development of protocols for amplification and quantification of nucleic acids even when present at very low number, a droplet digital PCR application could be a valid solution for the detection of inoculated PGPM to soil samples [ 117 ]. In addition, -Omics analyses, in particular NGS analyses, although much more expensive, are also very useful and rapid methodologies for a relative quantitative evaluation of the microorganism or microorganism consortia applied as biofertilizers on root tissues and in the rhizosphere soil, starting from the first stage of plant development to the end of vegetative growth [ 61 , 76 , 81 ]. Moreover, the determination of the entire genomic DNA sequence (WGS) of a microbial strain could also be a powerful approach to investigate the survival efficiency in the soil/rhizosphere of the inoculum [ 119 ].…”

“…Other authors have reported improvements in food quality, which can be attributed to microorganisms. For instance, recent field research on the application of different soil microbial consortia to common wheat has highlighted heightened plant growth and nitrogen accumulation in the phases of stem elongation and heading, as well as upregulation of two gluten protein subunits, which are important indicators of flour quality [ 76 , 142 ]. Similarly, [ 82 ] demonstrated that the resilient cereal Tritordeum was better adapted to organic farming compared to conventional farming through an increased abundance of beneficial bacteria (Bacteroidetes) in the soil microbial community of the rhizosphere.…”