Designing Synergistic Biostimulants Formulation Containing Autochthonous Phosphate-Solubilizing Bacteria for Sustainable Wheat Production

Abstract

Applying phosphate-solubilizing bacteria (PSB) as biofertilizers has enormous potential for sustainable agriculture. Despite this, there is still a lack of information regarding the expression of key genes related to phosphate-solubilization (PS) and efficient formulation strategies. In this study, we investigated rock PS by Ochrobactrum sp. SSR (DSM 109610) by relating it to bacterial gene expression and searching for an efficient formulation. The quantitative PCR (qPCR) primers were designed for PS marker genes glucose dehydrogenase (gcd), pyrroloquinoline quinone biosynthesis protein C (pqqC), and phosphatase (pho). The SSR-inoculated soil supplemented with rock phosphate (RP) showed a 6-fold higher expression of pqqC and pho compared to inoculated soil without RP. Additionally, an increase in plant phosphorous (P) (2%), available soil P (4.7%), and alkaline phosphatase (6%) activity was observed in PSB-inoculated plants supplemented with RP. The root architecture improved by SSR, with higher root length, diameter, and volume. Ochrobactrum sp. SSR was further used to design bioformulations with two well-characterized PS, Enterobacter spp. DSM 109592 and DSM 109593, using the four organic amendments, biochar, compost, filter mud (FM), and humic acid. All four carrier materials maintained adequate survival and inoculum shelf life of the bacterium, as indicated by the field emission scanning electron microscopy analysis. The FM-based bioformulation was most efficacious and enhanced not only wheat grain yield (4–9%) but also seed P (9%). Moreover, FM-based bioformulation enhanced soil available P (8.5–11%) and phosphatase activity (4–5%). Positive correlations were observed between the PSB solubilization in the presence of different insoluble P sources, and soil available P, soil phosphatase activity, seed P content, and grain yield of the field grown inoculated wheat variety Faisalabad-2008, when di-ammonium phosphate fertilizer application was reduced by 20%. This study reports for the first time the marker gene expression of an inoculated PSB strain and provides a valuable groundwork to design field scale formulations that can maintain inoculum dynamics and increase its shelf life. This may constitute a step-change in the sustainable cultivation of wheat under the P-deficient soil conditions.

In-depth characterization of phytase-producing plant growth promotion bacteria isolated in alpine grassland of Qinghai-Tibetan Plateau

“…The qPCR verification of BPPs has been reported in several bacterial strains, such as Shen et al (2016) , who reported a BPP gene (phyPf) cloned from Pseudomonas fluorescens JZ-DZ1, where the results of qPCR proved that the secretion of phytase was regulated by phyPf. In particular, some reports indicate that the activity of microbial phosphatases was determined by the interaction between functional gene abundance, soil available P content, and substrate availability ( Suleman et al, 2018 ; Rasul et al, 2021 ; Yahya et al, 2022 ). Therefore, screening of PGPBs with phytase genes can help identify the new microbial taxa capable of mineralizing organic P.…”

Integrated analysis of potential microbial consortia, soil nutritional status, and agro-climatic datasets to modulate P nutrient uptake and yield effectiveness of wheat under climate change resilience

“…The results showed an increase in grain yield (2%–14%) and seed P content (3%–5%) in inoculated treatments with a reduced application of DAP as compared to uninoculated controls. Previous studies indicated that P-solubilizing microorganisms showed the best effect with reduced application of DAP fertilizers ( Rasul et al., 2019 ; Rosa et al., 2020 ; Yahya et al., 2022 ). Higher seed P content might be due to P translocation to seed because of PSB inoculation ( Feng et al., 2021 ).…”

“…Therefore, for designing the optimal inoculant formulation, a well-characterized FM-based carrier material was used in the study. Other contributing factors for the maintenance of microbial viability are the constitutional essential elements in FM, predominantly silicon (Si), iron (Fe), P, calcium (Ca), magnesium (Mg), carbon (C), and oxygen (O) ( Yahya et al., 2022 ). Studies showed that a significant amount of Si, Fe, P, Ca, and Mg in FM made it a suitable product as a source of nutrients ( Dotaniya et al., 2016 ).…”

“…Three filter mud (FM) and soil-specific consortia-based bioformulations were developed. FM, an agro-industrial by-product of sugar cane ( Yahya et al., 2022 ), was ground and sieved through a 2-mm sieve and further autoclaved before inoculation. The bacterial suspension (300 ml) of each consortium (1 × 10 9 CFU ml -1 ) was then aseptically and uniformly mixed in 700 g of FM, packed in polythene bags, and incubated at 28°C ( Pastor-Bueis et al., 2019 ).…”

Phosphorus solubilizing microorganisms: potential promoters of agricultural and environmental engineering

“…Biostimulants: Researches were carried out to Investigate the use of PSMs and other microorganisms as biostimulants to enhance plant growth and productivity, as well as the ability of plants to cope with environmental stress (Yahya et al, 2022).…”