Browsing by Author "Ajay Shankar"

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Appraisal of Visible/IR and microwave datasets for land surface fluxes estimation using machine learning techniques
(Elsevier Ltd, 2024) Ajay Shankar; Vishal Prasad; Prashant K. Srivastava; Akash Anand; Vikas Dugesar
Land surface fluxes such as Soil Moisture (SM) and Soil Temperature (ST) are very important variables for many applications that includes agriculture water management, weather and climate prediction, natural disasters etc. Further, they are important for understanding soil processes, hydrological balances as well as changes in microbial population. Mapping of the soil moisture content at various depth is crucial for the sustenance of water resources and also to understand about the development of crops in forms of quality and yield. With changing environmental conditions, there is a need of approaches for estimating SM and ST in various climatic and geographic situations. Towards this, Earth Observation datasets at higher resolutions from satellites such as Sentinel 1 and 2, could play an important role in the monitoring of SM and ST over the larger areas. For estimation of SM and ST, machine learning approaches could be effective. This research looked into the possibilities of using Earth Observation (EO) data of Sentinel-1 (S1) and Sentinel-2 (S2) simultaneously to estimate SM and ST by using the machine learning methods such as random forest (RF) and Support Vector Machines (SVM). The coefficient of correlation (r), root mean square error (RMSE), and Bias are utilized in model enactment for accuracy and comparative analysis of the models used. The overall analysis indicates that the SVM model (r = 0.85, RMSE = 2.54, Bias = −0.05) is the second most appropriate after the RF model (r = 0.89, RMSE = 2.34, Bias = 0) for estimating land surface fluxes (SM and ST). © 2024 Elsevier Ltd
Comparative Evaluation of Fertility Status in Drought Impacted Soils of Hamirpur, Uttar Pradesh
(Indian journals, 2023) Ajay Shankar; Vishal Prasad
Drought causes the depletion of soil nutrient and thereby reduction in its fertility. Thus, assessment of soil for fertility status in drought affected region is very essential to sustain the nutrient quality of soil under the influence of climate change for sustainable production of food crops. It may also put on the alert about evolving problems in drought prone regions. The surface soils from 10 cm depth were collected from Hamirpur district, which is vulnerable to drought and heat waves, with an average annual rainfall of 864 mm. The physicochemical properties and nutrient quality of soil along with microbial population were evaluated. The pH values were neutral to alkaline and textures were clay, silty clay loam and loam types. Soil moisture ranged from 7 to 49% and it showed positive correlation with water holding capacity (WHC) (r=0.43*). Electrical conductivity ranged from 45 to 167.8 μS cm-1. The organic carbon (OC) content had low to medium value (0.37 to 2.97%), lower amounts of available N (13.8-64 kg ha-1), high values of available P (86.4 to 255 kg ha-1) and a very low to very high available K (65.9 to 1062.4 kg ha-1). Overall, a prevailing impact of climate change and parent material was found on WHC, K and P distribution and the relationship between nutrients and bacterial colony forming units revealed WHC, OC, P and K are major driving forces for bacterial populations which are supposed to be one of the foremost and important players for maintaining the fertility of the soils. © 2023, Indian journals. All rights reserved.
Desiccation-tolerant rhizobacteria
(Elsevier, 2020) Ajay Shankar; Anjali Singh; Shivani Chaudhary; Vishal Prasad
Keeping in mind the various types of direct and indirect impacts of drought on plant and human, it is necessary to overcome or mitigate the drought stress to fulfil everyone’s needs. Researchers all over the globe are doing rigorous work to find-out strategies to mitigate the drought stress like development of drought-tolerant varieties, shifting the crop calendars, resource management practices, traditional breeding and genetic engineering. Most of these are not cost-effective. Some have time limitations and some have ethical issues. Therefore the ecofriendly approaches are more appreciable nowadays. One such strategy could be stress-tolerant plant growth promoting rhizobacteria (PGPR) having capabilities to enhance plant growth under stressful environment. Therefore screening and characterization is crucial for selecting the potential drought-tolerant PGPR. This chapter tries to show the significance of bacterial mediated drought tolerance in agricultural crops for agricultural water stress management in a sustainable way. © 2021 Elsevier Inc. All rights reserved.
Enhanced resistance to fungal pathogens through selective utilization of useful microbial genes
(Elsevier, 2018) Anjali Singh; Shivani Chaudhary; Ajay Shankar; Vishal Prasad
Fungal pathogens of crop plants are responsible for huge losses in crop productivity worldwide. By selective utilization of useful microbial genes in plant systems through the transgenic approach these fungal pathogens can be effectively managed and loss in crop productivity can be minimized. Microbial genes coding for mitogen-activated protein kinases, chitinases, glucanases, and peroxidases have effectively been overexpressed in plants and successful control of fungal pathogens have been achieved along with reductions in losses to the crop yield. This chapter aims to highlight several of such useful microbial genes effective against fungal pathogens of plants and their selective utilization. © 2019 Elsevier B.V. All rights reserved.
Hydropriming and biopriming improve medicago truncatula seed germination and upregulate dna repair and antioxidant genes
(MDPI AG, 2020) Chiara Forti; Ajay Shankar; Anjali Singh; Alma Balestrazzi; Vishal Prasad; Anca Macovei
Seed germination is a critical parameter for the successful development of sustainable agricultural practices. While seed germination is impaired by environmental constraints emerging from the climate change scenario, several types of simple procedures, known as priming, can be used to enhance it. Seed priming is defined as the process of regulating seed germination by managing a series of parameters during the initial stages of germination. Hydropriming is a highly accessible and economic technique that involves soaking of seeds in water followed by drying. Biopriming refers to the inoculation of seeds with beneficial microorganism. The present study aims to investigate whether hydropriming and biopriming could enhance seed germination. Thereby, the germination of Medicago truncatula seeds exposed to hydropriming and/or Bacillus spp. isolates was monitored for two-weeks. The seeds were sown in trays containing two types of in situ agricultural soils collected from Northern India (Karsara, Varanasi). This region is believed to be contaminated by solid waste from a nearby power plant. Phenotypic parameters had been monitored and compared to find the most appropriate combination of treatments. Additionally, qRT-PCR was used to evaluate the expression levels of specific genes used as molecular indicators of seed quality. The results show that, while hydropriming significantly enhanced seed germination percentage, biopriming resulted in improved seedling development, represented by increased biomass rather than seedling length. At a molecular level, this is reflected by the upregulation of genes involved in DNA damage repair and antioxidant defence. In conclusion, hydropriming and biopriming are efficient to improve seed germination and seedling establishment in soils collected from damaged sites of Northern India; this is reflected by morphological parameters and molecular hallmarks of seed quality. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Phosphate Solubilizing Microorganisms: Multifarious Applications
(Springer, 2023) Mahendra Kumar; Ajay Shankar; Shivani Chaudhary; Vishal Prasad
Phosphorus is a key element for plant growth and development. Phosphate sources are available in soil present in both forms organic as well as inorganic. Due to its highly reactive nature, phosphate forms insoluble complex with several metal ions (Fe, Al, and Ca) and becomes unavailable for plant uptake and thus acts as a major limiting factor. Phosphate solubilizing microorganisms (PSMs) such as bacteria, fungi, and actinomycetes possess the ability to solubilize insoluble phosphate and convert into available form as orthophosphate ions thereby helping in plant growth, crop yield, and simultaneously improve soil health. In addition, these PSMs also play major role in various other key activities of environmental significance. A few such activities include ecological restoration, heavy metal decontamination and immobilization, promoting sustainable agricultural practices in saline-alkaline and other unsuitable soils. Overall, these PSMs are evolving as worthy candidates with multifarious application for environmental sustainability. This chapter covers several aspects of phosphate solubilization and mobilization by PSMs in the soil and further describes several other beneficial applications of these PSMs. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023.
Polyketide and its derivatives
(Elsevier, 2018) Anjali Singh; Shivani Chaudhary; Ajay Shankar; Vishal Prasad
Polyketides are a distinct and important class of secondary metabolites which are produced by several diverse types of living organisms and are employed in providing them with certain survival advantages. Polyketides have high biological activity and structurally they are complex organic compounds. The naturally occurring polyketides and their derivatives have significant pharmaceutical values and several drugs are either derived from them or are inspired by them. This chapter highlights some of the characteristic features of these polyketides and their derivatives along with their biosynthetic pathways. © 2019 Elsevier B.V. All rights reserved.
Potential of desiccation-tolerant plant growth-promoting rhizobacteria in growth augmentation of wheat (Triticum aestivum L.) under drought stress
(Frontiers Media S.A., 2023) Ajay Shankar; Vishal Prasad
Wheat (Triticum aestivum L.) yield and physiology are adversely affected due to limited water availability. However, desiccation-tolerant plant growth-promoting rhizobacteria (DT-PGPR) are potential candidates that can overcome the negative impacts of water stress. In the present study, a total of 164 rhizobacterial isolates were screened for desiccation tolerance up to −0.73 MPa osmotic pressure, of which five isolates exhibited growth and expression of plant growth properties under the influence of desiccation stress of −0.73 MPa. These five isolates were identified as Enterobacter cloacae BHUAS1, Bacillus cereus BHUAS2, Bacillus megaterium BHUIESDAS3, Bacillus megaterium BHUIESDAS4, and Bacillus megaterium BHUIESDAS5. All five isolates exhibited plant growth-promoting properties and production of exopolysaccharide (EPS) under the impact of desiccation stress. Furthermore, a pot experiment on wheat (variety HUW-234) inoculated with the isolates Enterobacter cloacae BHUAS1, Bacillus cereus BHUAS2, and Bacillus megaterium BHUIESDAS3 exhibited a positive influence on the growth of wheat under the condition of water stress. A significant improvement in plant height, root length, biomass, chlorophyll and carotenoid content, membrane stability index (MSI), leaf relative water content (RWC), total soluble sugar, total phenol, proline, and total soluble protein, were recorded under limited water-induced drought stress in treated plants as compared with non-treated plants. Moreover, plants treated with Enterobacter cloacae BHUAS1, Bacillus cereus BHUAS2, and Bacillus megaterium BHUIESDAS3 depicted improvement in enzymatic activities of several antioxidant enzymes such as guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). Beside this significant decrease in electrolyte leakage, H2O2 and malondialdehyde (MDA) contents were also recorded in treated plants. From the results obtained, it is evident that E. cloacae BHUAS1, B. megaterium BHUIESDAS3, and B. cereus BHUAS2 are the potential DT-PGPR having the capability to sustain growth and yield, alleviating the deleterious effect of water stress in wheat. Copyright © 2023 Shankar and Prasad.
Rhizobacteria: Tools for the management of plant abiotic stresses
(CRC Press, 2016) Anjali Singh; Ajay Shankar; Vijai Kumar Gupta; Vishal Prasad
Plants are continuously exposed to a plethora of threats originating from different biotic and abiotic stressors, which have escalated over time due to change in global climate pattern as well as human interferences and the subject of stress is imperative in influencing plant growth and crop production all around the world. Diverse methods like use of plants with natural tolerance or plants with modified tolerance by use of stress-related genes are available for alleviation of such stresses. Nevertheless, the use of rhizospheric microorganisms having plant growth-promoting traits has also been proved to be effective under stressful conditions. Such microbes can symbiotically or non-symbiotically alleviate the effects of stress and enhance plant growth. Therefore, diverse microbial species and strains are isolated, screened, tested, and used as microbial inoculums worldwide. The vast influence of rhizospheric microbes toward the growth and production of crop plants can be environmentally and economically significant. This chapter highlights the management and mitigation of various abiotic stressors and their effects on plants by exploring the opportunities available with the rhizobacterial microbes. © 2017 by Taylor & Francis Group, LLC.
Usefulness of penicillium in enhancing plants resistance to abiotic stresses
(Elsevier, 2017) Shivani Chaudhary; Ajay Shankar; Anjali Singh; Vishal Prasad
Plants have limited protection against environmental stresses like extremes of temperature, high light, flooding, drought, the presence of toxic metals and environmental organic contaminants, radiation and high salt. These stresses cause great damage to plants and decrease their productivity. Some soil microorganisms including bacteria and fungi can help plants to partially overcome the deleterious effects of a number of different environmental stresses. Several of the fungi known as plant growth-promoting fungi may facilitate plant growth either by promoting the acquisition of nutritional resources, such as nitrogen, phosphorus, or iron, by preventing or decreasing the damage to plants abiotic stresses, or by directly stimulating plant growth by either providing plant hormones, such as auxin, cytokinin, or gibberellin. Penicillium is one such fungus that has various plant-growth-promoting characteristics like production of phytohormones, phosphate solubilization, synthesis of amino acids, secretion of various antioxidative enzymes, and biologically active secondary metabolites. All these properties favor plant growth and help plants cope with abiotic stresses. This chapter summarizes the role of Penicillium in plants exposed to abiotic stresses. © 2018 Elsevier B.V. All rights reserved.