Arid regions cover a large part of the Earth's surface and are at risk of increased agricultural activity and expected shifts in climate. Unfortunately, there is still a lack of comprehensive knowledge about the impact of land use on soil quality in these soils. Using a state factor approach, we studied the effects of different land use types on soil physico-chemical and biological characteristics in the Bhuj region of Kutch, Gujarat (India). Our analysis identified six key land uses: barren land (BL), natural forest (NF), grazing land (GL), and cultivated land under monocropping (MC), intercropping (IC), and crop rotation (CR). Our findings demonstrated significantly higher levels of soil organic carbon (SOC), calcium carbonate (CaCO3), plant-available nutrients (nitrogen, potassium, sodium, calcium, and magnesium), and enzyme activities in NF and GL (P < 0.05) than cultivated land and BL. For instance, SOC content in NF and GL exceeded that in cultivated land by 130

In the study, plant growth promoting rhizobacteria (PGPR) indigenous to arid western Rajasthan were isolated and screened for plant growth promoting (PGP) capabilities. Ten isolates showing multiple PGP activities were identified as Pseudomonas sp. G6-3, Staphylococcus sp. G6-4, Bacillus badius G8-6, Agrobacterium sp. G8-7, Bacillus pseudomycoides G10-1, Staphylococcus capitis subsp. capitis G11-4, Bacillus paralicheniformis G11-5, Bacillus subtilis G12-3, Stenotrophomonas pavanii G12-4, and Solibacillus isronensis G21-9. Physiological profiling of these isolates demonstrated them to be tolerant to drought (25% PEG-6000), high temperature (40 degrees C), alkalinity (pH 10.0), and salinity (4.5% NaCl). These PGPR significantly improved clusterbean seedling characteristics in moisture stress-induced hydroponic flask cultures and pots. PGPR inoculation of clusterbean in drought-induced pots significantly enhanced the plant dry weight by 15-33%, plant water potential by 5-8%, and the relative water content of leaves by 4-16%. There was also a significant reduction in the levels of anti-oxidant enzymes and proline in plant tissues under drought conditions, which indicated lower levels of stress experienced by the treated plants. These were translated into yield enhancements by 13-15% under rainfed conditions. The study demonstrates the ability of stress tolerant PGPR from arid western Rajasthan in enhancing drought resilience of arid legumes besides promoting their growth, and their potential utility in sustainable arid agriculture systems.

Arid and semi-arid regions are vast reservoirs of hardy organisms, including plant species and the associated microorganisms. An important crop of these regions is the pearl millet which serves as a source of food and feed, especially in the rainfed tracts. The inherent hardiness of the crop has attracted researchers from all over the world to unveil its underlying biology as well as to assess the role of associated microflora in imparting the hardiness that allow pearl millet to survive under very harsh climatic conditions. The pearl millet-associated microbiome consists of the rhizospheric (within the rhizosphere), phyllospheric (on the leaf surfaces) and endophytic (within the internal tissues) microbial communities. These microorganisms play a critical role in plant health and growth by improving the uptake of essential nutrients, protecting plants from pathogens, and enhancing drought and disease tolerance. This has been demonstrated in several studies wherein microbial inoculation of pearl millet resulted in increased protection from diseases like downy mildew, enhanced drought and high temperature tolerance and improved plant characteristics including yield. Exploring native stress tolerant and plant growth promoting microorganisms and unraveling their effect on molecular biology and biochemistry of pearl millet plants holds huge potential for their utilization in sustainable arid and semi-arid agriculture systems.

Pearl millet (Pennisetum glaucum L.), a member of the Poaceae family, is a widely cultivated cereal crop and considered to be one of the most important millet crops globally due to its remarkable drought tolerance, adaptability to marginal environments, and high nutritional value. This scientometric study aims to identify the most relevant sources of information in the field of pearl millet research in India during 2000-2022. A total of 844 documents from 181 sources were identified, indicating a moderate level of research activity. The average citations per document were 13.42, suggesting that the research landscape in India has received a reasonable level of attention in the scientific community. The highest number of articles published were in 2021 (55) followed by 2020 (51) and 2018 (44). The data showed that the Indian Journal of Agricultural Sciences was the most prolific and the other journals maintained a relatively stable production over time. The most frequent topics were downy mildew, Sclerospora graminicola, and sorghum. The results suggest that India has established collaborative relationships with various countries worldwide to produce scientific papers.

The study describes green synthesis of diverse nanoparticles using a single platform technology using water extract of powdered coffee and clove/polyphenols of coffee and clove under mild environmental conditions. Treatment of the respective chloride salt solutions/chloride salt combinations, with sodium bicarbonate (NaHCO3) in presence of polyphenolic plant extract yielded 6.5–26.8% nanoparticles of Mn, Zn, Cu, Co, Fe, Ni, and P, with diameters ranging from 1.0 to 99.7 nm. The nanoparticles were found to be stable for more than 15 days. Their potential in enhancing crop growth was also examined by treating pearl millet plants to foliar sprays of the synthesized nanoparticles. Green-synthesized Fe nanoparticles had a greater effect in enhancing the plant biomass when compared with commercially available Fe nanoparticles. The nanoparticle spray also did not affect the soil microflora adversely. The biological route to nanoparticle synthesis, utilizing indigenous plant products is a cost-effective approach, and their potential to be utilized as both reducing and stabilizing agents in the process offers a green platform for nanoparticle synthesis.

A huge diversity of microorganisms from the surrounding habitat form association with plants throughout their life cycle. Chiefly, plant-microbial associations are governed by the micro and macro habitat, as well as growth-stage of the plant. This phenomenon of highly selective plant-microbial association could serve as a major breakthrough in passing the bottleneck of microbe-mediate mitigation of abiotic stresses in plants, and development of climate-smart agricultural systems in changing agro-climate scenario. Associative microbes are capable of specifically perceiving and responding to the plant-signals relating to colonization and development of beneficial associations. These microbes colonize the plant-phyllosphere and rhizosphere; execute a variety of metabolic activities to yield different bioactive compounds capable of inducing a range of physicochemical responses in plants, which ultimately result in development of induced systemic tolerance conditions that makes plant relatively more resilient to the adverse environmental circumstances. This chapter principally summarizes the beneficial plant-microbe interactions under drought and salinity stress conditions. Further, the role of beneficial microbes in other abiotic stresses is also discussed along with the recent advancements and future outlook in this area.

Crop plants are often subjected to a multitude of nonoptimal environmental factors that hinder their growth and productivity. Sustainable agricultural production requires the adoption of efficient, low-cost, and nonpolluting routes to crop management. This calls attention to the vast diversity of soil microflora that has immense potential in promoting plant growth besides alleviating diverse stresses. Plant growth-promoting rhizobacteria (PGPRs) and fungi form beneficial relationships with plants, and their interactions evoke local and systemic responses in plants through several molecular and cellular mechanisms upon perception of environmental cues. This enables plants to cope with stressors such as temperature extremes, drought, flooding, salinity, and heavy metal pollutants. Such beneficial plant-microbe associations are known to facilitate germination, growth, and productivity of plants under multiple stresses. The chapter strives to garner a better understanding of the underlying mechanisms involved in the microbe-mediated abiotic stress mitigation and their potential utility in agricultural production systems.

The increasing costs of energy, equipment, labor and the growing concernover soil loss have paved the way to development of reduced-tillage systems in placeof conventional tillage. These residue-retaining reduced-tillage systems are especiallyeffective in controlling soil erosion and substantially enhancing soil water storage. Thismodification of the soil microclimate by reduced-tillage exerts beneficial effects on thesoil microbial communities which plays a great role in nutrient transformations. Whileminimum tillage allows for minimal soil disturbance during field operations, no-tillagerefers to the complete absence of tillage. In practice, if one desires to reap equal orhigher yields and better environmental performance with minimum tillage than withconventional tillage systems, several components need to be applied to a conservationagriculture system. This can lead to variable yield responses with the minimum-/no-till management system, especially in a rainfed agro-ecology. Here we review thesuitability of reduced-tillage in arid regions, especially with reference to India whereexperiments on minimum tillage started in the early eighties. The results show limitedsuccess with this concept in Indian arid region, where climate and residue availabilityare a matter of concern. So, successful implementation of reduced-tillage systems as apotential solution to sustainable agricultural intensification needs 1) better understandingof crop and environmental variables and 2) appropriate adoption measures with ampleinstitutional and technology support, over a long term.

Microorganisms are known to inhabit domains that lie outside the perceived boundaries of life. These organisms, known as extremophiles, not only adapt to severe environmental conditions but also often require extreme conditions for growth and survival. These include the thermophiles (high temperature loving microorganisms), psychrophiles (low temperature loving microorganisms), acidophiles (acid-loving microorganisms), alkaliphiles (alkali-loving microorganisms), halophiles (salt-loving microorganisms) and barophiles or piezophiles (high pressure loving microorganisms). To enable their viability in regions that are 'empty' in a biological sense, these organisms possess unique physiological and metabolic specialties. Microbial response to environmental parameters, like ambient temperature, Ph, and salinity of the medium, atmospheric pressure, etc., are manifested through modifications of cell organelles, biomolecules, and the resultant cellular changes. Besides the intrinsic physiological stability, an overall shift in metabolic pathways with the predominance of secondary and intermediate pathways that detour central metabolism, also provides the extremophiles with functional stability under diverse conditions. These properties have attracted research on their molecular machinery which has unveiled their immense biotechnological potential. This chapter offers an insight into the 'extremophilic' nature of microorganisms and comprehends the adaptive strategies that they manifest in order to be able to survive under extreme limits of environmental factors.

Increasing fertilizer demands and dwindling mineral reserves warrant sustainable alternatives for plant fertilization. Organo-mineral fertilizers (OMFs) based on indigenous materials which are unutilized commercially are a possible option. The study describes the effect of novel OMF of phosphorus (OMF-P) and potassium (OMF-K), developed respectively from insoluble low-grade rock phosphate and feldspar on plant growth. The experiment was conducted in a glass chamber partitioned into two blocks, one with soil and the other with soil supplemented with 1% OMF-P or 1% OMF-K. Pearl millet plants were grown in the chambers for 45 days and the roots and soil from different chamber blocks were separated and analyzed. Root volume, fresh and dry weights, average root length, diameter and number of root tips were significantly increased with OMF-P/OMF-K and plants showed improved growth and plant height. The release and availability of P/K in soil was confirmed with isolations of P- and K-solubilizing fungi from the blocks with OMF along with significantly higher values of available P (0.006 mg g−1) and K (0.01 mg g−1) recorded from these blocks compared to control chambers. Moreover, the OMF prills did not exhibit any adverse effects on the plants and on soil microflora. The release of soluble P and K from the OMF is attributed to the presence of P and K solubilizers in soil, since conditions favourable for their selective enrichment are created. The OMF prills developed could address issues of deteriorating mineral reserves and associated environmental degradation, besides providing a sustainable management option.

Plants and microorganisms sense and respond to biotic and abiotic signals in the environment to competitively optimize their fitness. These specific adjustments which are pertinent to prevailing environmental conditions bring about distinct signal-induced behavioural responses that appear intelligent. A suite of cellular and molecular networks underlie the generation of such attributes in plants and microorganisms. Recent advances in systems biology have gained insights from these biomolecular networks in fabricating biomimetic signaling circuits. Detailed interpretations, however, reveal the behavioural responses to be a conditioned alertness as a result of prudent signal perception. The review, therefore, examines the concept of 'intelligence' in the plant and microbial world and tries to ascertain whether their interactive responses are an outcome of pure intelligence or sheer response.

Sustainable enhancement in food production from less available arable land must encompass a balanced use of inorganic, organic, and biofertilizer sources of plant nutrients to augment and maintain soil fertility and productivity. The varied responses of microbial inoculants across fields and crops, however, have formed a major bottleneck that hinders its widespread adoption. This necessitates an intricate analysis of the inter-relationships between soil microbial communities and their impact on host plant productivity. The concept of “biased rhizosphere,” which evolved from the interactions among different components of the rhizosphere including plant roots and soil microflora, strives to garner a better understanding of the complex rhizospheric intercommunications. Moreover, knowledge on rhizosphere microbiome is essential for developing strategies for shaping the rhizosphere to benefit the plants. With the advent of molecular and “omics” tools, a better understanding of the plant-microbe association could be acquired which could play a crucial role in drafting the future “biofertilizers.” The present review, therefore aims to (a) to introduce the concepts of rhizosphere hotspots and microbiomes and (b) to detail out the methodologies for creating biased rhizospheres for plant-mediated selection of beneficial microorganisms and their roles in improving plant performance.

Lignocellulosic biomass is currently the most promising alternative energy source for realizing sustainable demands of agrarian economies. Its natural recalcitrance to degradation necessitates a detailed study on the complex biochemistry involved in bioconversion of this lignin-carbohydrate complex. A comprehension of the enzymology and role of principal and accessory glycosyl hydrolases involved in biomass degradation are, hence, noteworthy in this context and the xyloglucan-active hydrolases warrant special mention. These are enzymes which carry out hydrolysis and transglucosylation of xyloglucan, the major hemicellulosic polysaccharide in plant biomass. The structurally complex xyloglucans cover and cross-link the cellulosic microfibrils in plant cell walls and make cellulose inaccessible to saccharification by cellulases. Solubilisation of biomass polysaccharides and release of sugars are central to the biomass-to-bioethanol process. Complete conversion of biomass carbohydrates requires a suite of hydrolytic enzymes, which may be designed specifically to accommodate the predominant and subsidiary biomass-cleaving enzymes. Xyloglucan hydrolases which are known to act synergistically with cellulases and xylanases in loosening the plant cell wall are vital enzymes to be deployed for successful bioconversion processes. This chapter is an insight into the capacity of these accessory, but indispensable, hydrolytic enzymes in unlocking the inaccessible biomass polysaccharides for increased sugar recovery and thereby, in drafting the fuels of future.

The present study reports the diversity in extracellular proteins expressed by the filamentous fungus, Aspergillus terreus CM20 with respect to differential hydrolytic enzyme production profiles in submerged fermentation (SmF) and solid-state fermentation (SSF) conditions, and analysis of the extracellular proteome. The SSF method was superior in terms of increase in enzyme activities resulting in 1.5-3 fold enhancement as compared to SmF, which was explained by the difference in growth pattern of the fungus under the two culture conditions. As revealed by zymography, multiple isoforms of endo-β-glucanase, β-glucosidase and xylanase were expressed in SSF, but not in SmF. Extracellular proteome profiling of A. terreus CM20 under SSF condition using liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) identified 63 proteins. Functional classification revealed the hydrolytic system to be composed of glycoside hydrolases (56%), proteases (16%), oxidases and dehydrogenases (6%), decarboxylases (3%), esterases (3%) and other proteins (16%). Twenty families of glycoside hydrolases (GH) (1, 3, 5, 7, 10, 11, 12, 15, 16, 28, 30, 32, 35, 43, 54, 62, 67, 72, 74 and 125), and one family each of auxiliary activities (AA7) and carbohydrate esterase (CE1) were detected, unveiling the vast diversity of synergistically acting biomass-cleaving enzymes expressed by the fungus. Saccharification of alkali-pretreated paddy straw with A. terreus CM20 proteins released high amounts of glucose (439.63±1.50mg/gds), xylose (121.04±1.25mg/gds) and arabinose (56.13±0.56mg/gds), thereby confirming the potential of the enzyme cocktail in bringing about considerable conversion of lignocellulosic polysaccharides to sugar monomers.

A successful lignocellulosic ethanol production process needs to address the technological impediments such as cost-competitiveness and sustainability of the process. Effective biomass utilization requires a repertoire of enzymes including various accessory enzymes. Developing an enzyme preparation with defined hydrolytic activities can circumvent the need for supplementing cellulases with accessory enzymes for enhanced hydrolysis. With this objective, mixture design approach was used in the present study to enhance glycoside hydrolase production of a fungal isolate, Aspergillus terreus CM20, by determining the proportion of different lignocellulosic components as enzyme inducers in the culture medium. A mixture of paddy straw and wheat straw (1.42:1.58) resulted in improved cellulolytic activities. The precipitated crude enzyme showed higher CMCase (365.03 18 IU g-1), FPase (161.48 IU g-1), avicelase (15.46 IU g-1), β-glucosidase (920.92 IU g-1) and xylanase (9627.79 IU g-1) activities. The potential of the crude enzyme for saccharification of alkali pretreated paddy straw was also tested. Under optimum conditions, saccharification released 25.0 g L-1 of fermentable sugars. This indicates the superiority of the crude enzyme produced with respect to its hydrolytic enzyme components.

The current study was aimed at optimizing the fermentation conditions for efficient ethanol production from biologically pretreated paddy straw. The yeast strain Saccharomyces cerevisiae LN1 showed highest fermentation efficiency at pH 5.0 and temperature 30 °C. Paddy straw pretreated with fungus Myrothecium roridum LG7 was saccharified with indigenous holocellulase from Aspergillus niger SH3 producing total sugar yield of 26.14 mg/ml with 19.23 mg/ml of glucose. Enzymatic hydrolysate was then fermented using S. cerevisiae LN1 to observe the effect of nutrient supplementation (yeast extract, MgSO 4 ·7H 2 O and (NH 4 ) 2 SO 4 ) on ethanol production. Higher ethanol was produced from saccharified material fermented without supplementation of any nutrient source. With the scale-up of ethanol production under optimized conditions in 7L bioreactor, 4.46 g/l of ethanol was produced with fermentation efficiency of 47.2 %. TLC of enzymatic hydrolysate confirmed the presence of p-coumaric acid, ferulic acid, vanillic acid, gallic acid and many other aromatic compounds and inhibitors in the saccharified material which limit fermentation efficiency of yeast strain. Thus, optimization of fermentation conditions can lead to development of a cost-effective process for efficient ethanol production, exploitation of which also requires removal of aromatic compounds and inhibitors which may hinder the ethanol production efficiency.

•Fugal isolates with high hydrolytic potential isolated from cold environment.•Cold active holocellulase from Aspergillus niger SH3 was characterized.•Experimental mixture design was employed to enhance enzyme production.•A. niger SH3 holocellulase showed high saccharification efficiency at low temperature.