RESUMO
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.
RESUMO
This study appraises the antioxidant and antimicrobial attributes of various solvent extracts (absolute methanol, aqueous methanol, absolute ethanol, aqueous ethanol, absolute acetone, aqueous acetone, and deionized water) from bark, leaves and seeds of Pongamia pinnata (L.) Pierre. Maximum extraction yield of antioxidant components from bark (16.31%), leaves (11.42%) and seeds (21.51%) of P. pinnata was obtained using aqueous methanol (20:80). Of the extracts tested, the bark extract, obtained with aqueous methanol, exhibited greater levels of total phenolics [6.94 g GAE/100 g dry weight (DW)], total flavonoids (3.44 g CE/100 g DW), inhibition of linoleic acid peroxidation (69.23%) and DPPH radical scavenging activity (IC(50) value, 3.21 µg/mL), followed by leaves and seeds extracts. Bark extract tested against a set of bacterial and fungal strains also revealed the strongest antimicrobial activity with the largest inhibition zone and lowest minimum inhibitory concentration (MIC). HPLC analysis of aqueous methanol extracts from bark, leaves and seeds indicated the presence of protocatechuic, ellagic, ferulic, gallic, gentisic, 4-hydroxybenzoic and 4-hydroxycinnamic acids in bark (1.50-6.70 mg/100 g DW); sorbic, ferulic, gallic, salicylic and p-coumaric acids in leaves (1.18-4.71 mg/100 g DW); vanillic, gallic and tannic acids in seeds (0.52-0.65 mg/100 g DW) as the main phenolic acids. The present investigation concludes that the tested parts of P. pinnata, in particular the bark, have strong potential for the isolation of antioxidant and antimicrobial agents for functional food and pharmaceutical uses.
