RESUMO
Modern agriculture is primarily focused on the massive production of cereals and other food-based crops in a sustainable manner in order to fulfill the food demands of an ever-increasing global population. However, intensive agricultural practices, rampant use of agrochemicals, and other environmental factors result in soil fertility degradation, environmental pollution, disruption of soil biodiversity, pest resistance, and a decline in crop yields. Thus, experts are shifting their focus to other eco-friendly and safer methods of fertilization in order to ensure agricultural sustainability. Indeed, the importance of plant growth-promoting microorganisms, also determined as "plant probiotics (PPs)," has gained widespread recognition, and their usage as biofertilizers is being actively promoted as a means of mitigating the harmful effects of agrochemicals. As bio-elicitors, PPs promote plant growth and colonize soil or plant tissues when administered in soil, seeds, or plant surface and are used as an alternative means to avoid heavy use of agrochemicals. In the past few years, the use of nanotechnology has also brought a revolution in agriculture due to the application of various nanomaterials (NMs) or nano-based fertilizers to increase crop productivity. Given the beneficial properties of PPs and NMs, these two can be used in tandem to maximize benefits. However, the use of combinations of NMs and PPs, or their synergistic use, is in its infancy but has exhibited better crop-modulating effects in terms of improvement in crop productivity, mitigation of environmental stress (drought, salinity, etc.), restoration of soil fertility, and strengthening of the bioeconomy. In addition, a proper assessment of nanomaterials is necessary before their application, and a safer dose of NMs should be applicable without showing any toxic impact on the environment and soil microbial communities. The combo of NMs and PPs can also be encapsulated within a suitable carrier, and this method aids in the controlled and targeted delivery of entrapped components and also increases the shelf life of PPs. However, this review highlights the functional annotation of the combined impact of NMs and PPs on sustainable agricultural production in an eco-friendly manner.
RESUMO
Kidney bean (Phaseolus vulgaris) productivity and nutritional quality are declining due to less nutrient accessibility, poor soil health, and indigent agronomic practices in hilly regions, which collectively led to a fall in farmer's income, and to malnutrition in consumers. Addressing such issues, the present investigation was designed to assess the impact of Pseudomonas jesenii MP1 and Pseudomonas palleroniana N26 treatment on soil health, microbial shift, yield, and nutrient status of the kidney bean in the Harsil and Chakrata locations of Indian Central Himalaya. P. jesenii MP1 and P. palleroniana N26 were characterized as cold adaptive PGPR as they possessed remarkable in vitro plant growth promoting traits. Further, field trial study with PGPR treatments demonstrated remarkable and prolific influence of both strains on yield, kidney bean nutrient status, and soil health at both geographical locations, which was indicated with improved grain yield (11.61%-23.78%), protein (6.13%-24.46%), and zinc content (21.86%-61.17%) over control. The metagenomic study revealed that use of bioinoculants also concentrated the nutrient mobilizing and plant beneficial microorganisms in the rhizosphere of the kidney bean. Moreover, correlation analysis also confirmed that the plant growth-promoting traits of P. jesenii MP1 and P. palleroniana N26 are the basis for improved yield and nutrient status of the kidney bean. Further, cluster and principal component analysis revealed that both P. jesenii MP1 and P. palleroniana N26 exhibited pronounced influence on yield attributes of the kidney bean at both the locations. At the Harsil location, the P. jesenii MP1-treated seed demonstrated highest grain yield over other treatments, whereas at Chakarata, P. jesenii MP1, and P. palleroniana N26 treatment showed almost equal enhancement (~23%) in grain yield over control. The above results revealed that these bioinoculants are efficient plant growth promoters and nutrient mobilizers; they could be used as green technology to improve human health and farmer's income by enhancing soil health, yield, and nutrient status of the kidney bean at hilly regions.
RESUMO
The experimental study was contrived to characterize two zinc-solubilizing bacteria (ZSB), namely BMRR126 and BMAR64, and their role in zinc (Zn) biofortification of rice. These bacteria solubilized Zn profoundly, determined qualitatively by halo-zone formation on a solid medium and quantitatively in a liquid broth by AAS and SEM-EDX. The lowering of pH and contact angle assessment of the liquid broth unveiled the establishment of the acidic conditions in a medium suitable for Zn solubilization. The characterization of both isolates on the basis of 16S rRNA gene analysis was identified as Burkholderia cepacia and Pantoea rodasii, respectively. These strains were also found to have some plant probiotic traits namely phosphate solubilization, production of siderophore, indole acetic acid (IAA), exopolysaccharide (EPS), and ammonia. The field experiments were performed at two diverse locations and under all treatments; the simultaneous use of BMRR126 and BMAR64 with zinc oxide (ZnO) resulted in the highest growth and productivity of the paddy crop. The utmost Zn achievement in the grain was estimated in a treatment (T9) (25.07 mg/kg) containing a consortium of BMRR126 and BMAR64 along with ZnO for the Terai region. The treatment containing single ZSB bioinoculant BMRR126 (T7) showed an elevated Zn amount in the rice grain (33.25 mg/kg) for the Katchar region. The soil parameters (pH, EC, organic carbon, NPK, available Zn, and dehydrogenase activity) were also positively influenced under all bacterial treatments compared to the uninoculated control. Our study clearly accentuates the need for Zn solubilizing bacteria (ZSB) to provide the benefits of Zn-biofortification in different regions.