The current investigation gives insights into a comparative analysis of bacterial endophyte Bacillus subtilis M-4 (BS) and chemical fungicide (CF) for disease management of charcoal rot in soybean. BS shows mycelial growth inhibition of Macrophomina phaseolina (MP) during in vitro conditions. Upon BS application significant changes were observed in the plants at their physiological, histological, and molecular levels as compared to the chemical fungicide under greenhouse conditions. Moreover, BS treatment suppresses the charcoal rot disease in soybean by reducing the stress markers viz; LPx (53.34 Schematic presentation of BS and CF effect on soybean during charcoal rot disease. Created with BioRender.com (acceded on 14 March 2022).

Nitrogen (N) and sulfur (S) are essential nutrient elements, and their deficiency affects crop growth, productivity, and nutrient uptake due to their multifaceted role in plant metabolism, which has been well documented. Therefore, agricultural management strategies that can overcome these deficiencies are the need of the hour. In this context, a study was undertaken with the objective to assess the impacts of N and S applications, either basally or through split application (12.5, 25 and 50 kg ha−1), on the nutrient uptake, productivity, use efficiency, and micronutrient content status in soybean seeds, and also the change in soil nutrient zinc (Zn) and iron (Fe) content at different critical stages of soybean crop growth. The field trial was conducted utilizing a randomized complete-block design, and comprised fourteen treatments with varying N and S quantities. N and S were applied through basal and split applications in different combinations. The salient findings indicated that the highest seed, straw yield, N, and S uptake were obtained with the application of N25+25, S25+25, and did not significantly vary with N25+25, S12.5+12.5, N50, and N25+S50. The highest N use efficiency was recorded with the application of N25+S50, and S use efficiency with the application of N25+25, S25+25. The split application of N and S as N25+25, S25+25 significantly increased soil Zn and Fe content at R2 and R5 stages of soybean crop growth, as well as seed Zn and Fe uptake. It can be concluded that the basal and split application of N and S at the rate of 25 kg ha−1 can improve soybean productivity through increased mobilization and assimilation by plants. The findings indicated that applying N and S separately, with 25 kg ha−1 each basally and at the R2 stage resulted in the highest nutrient uptake, and seed and straw yields. The nutrient use efficiencies, along with Zn and Fe uptake by seeds, exhibited noticeable improvements with this split application approach compared to the control. Furthermore, the soil Zn and Fe contents also experienced enhancements due to the split application of both Nand S fertilizers. These results underscore the potential benefits of temporally adopting optimized fertilizer application strategies to maximize agricultural productivity while ensuring efficient nutrient utilization and soil health maintenance. Further research and field trials could provide deeper insights into the long-term impacts and scalability of this approach across different crop varieties and environmental conditions.

The soil rhizosphere pH, enzymatic activities (dehydrogenase, β-glucosidase, and arylsulfatase), microbial respiration rates, soil microbial biomass-C, soil microbial biomass-N and soil microbial biomass-S were used to monitor the impact of nitrogen (N) and sulfur (S) applications. The randomized block design experiment was conducted comprised fourteen treatments, varying N and S applications in timing and quantity at specific growth stages, with three replications. The results showed a significant increase in soil enzymatic and microbial activities after incorporation of N and S in the soil. The research highlights the efficacy of N and S (25 N kg ha− 1 as basal + 25 N kg ha− 1 at the R2 stage + 12.5 S kg ha− 1 as basal + 12.5 S kg ha− 1 at the R2 stage) in enhancing crucial variables, dehydrogenase, β-glucosidase, and aryl sulfatase activities, alongside microbial respiration and microbial biomass-C, N, and S during soybean growth at R2 and R5 stages. Notably, N treatments consistently lowered rhizosphere pH, with significant decreases observed, and combined N and S treatments also contributed to pH reductions compared to controls, while sulfur-only treatments maintained similar or slightly lower pH levels. Incorporating N and S boosted soil enzymatic and microbial activities while decreasing pH, with split dosing of N and S enhanced key variables in soybean, underscoring the intricate interactions between nutrients and soil dynamics. These findings provide valuable insights into optimizing nutrient management practices for improved soil health and crop productivity.

Arbuscular mycorrhizal (AM) fungi are being used as a new generation of biofertilizers to increase plant growth by improving plant nutrition and bio-protection. However, because of the obligatory nature of the plant host, large-scale multiplication of AM propagules is challenging, which limits its applicability. This study evaluates the ability of Burkholderia arboris to increase AM production in soybean mill waste and vermicompost amended by soil–sand mixture planted with sorghum as a host plant. The experiment was conducted in a nursery using a completely randomized design with four inoculation treatments (B. arboris, AM fungi, B. arboris + AM fungi, and control) under sterilized and unsterilized conditions. AM production was investigated microscopically (spore density and root colonization), and biochemically (AM-specific lipid biomarker, 16:1ω5cis derived from neutral lipid fatty acid (NLFA), and phospholipid fatty acid (PLFA) fractions from both soil and roots). Integrating B. arboris with AM fungi in organically amended pots was found to increase AM fungal production by 62.16 spores g−1 soil and root colonization by 80.85

Arbuscular mycorrhizal fungi (AMF) are widely known to improve plant and soil health by forming an obligate symbiotic relationship with most terrestrial plants. AMF biofertilizers can significantly reduce the need for synthetic inputs. The contribution of AMF to crop yield enhancement and ecological services is widely documented. Apart from agriculture, AMF applications have also found a significant position in forestry, agroforestry, horticulture, and restoring natural ecosystems. AMF promote soil aggregation, sequester soil C, and improve soil health by modifying the physical and nutritional state of the rhizosphere. Considering soil salinization and heavy metal pollution, AMF could act as bio-ameliorators. The production of AMF biofertilizers is challenging due to their obligate symbiotic nature which requires the presence of actively growing plant roots to complete their life cycle. AMF infectious propagules include arbuscules, spores, vesicles, and hyphae (intraradical and extraradical). Each of these can infect a plant and be used for AMF production. Several methods have been introduced to mass-produce AMF such as hydroponics, aeroponics, substrate-based, on-farm, and in vitro techniques. Substrate-based and on-farm production are simpler, while in vitro method ensures contamination-free inoculum. Hydroponics and aeroponics do not need a substrate but require a complex setup. The mass multiplication of AMF is widely attempted across the globe, but its success is a determinant of numerous factors that are often overlooked. This chapter tries to elucidate the various AMF inoculum production processes and their influencing elements. In addition, attempts have been made to comprehend how AMF inoculum could be adapted to a variety of crops and soil types to increase the benefits received from AMF in sustainable agriculture.

In a changing climate, conservation tillage and agronomic biofortification are essential for enhancing crop yield, nutritional security, carbon stocks, and soil quality. Consequently, a field study was conducted in central India to assess the short-term (4 years) effects of crop establishment techniques (CETs) and agronomic biofortification methods (ABMs) on soil health indicators, grain yield, and quality in the soybean-wheat cropping system. The experiment followed a split-plot design with two CETs in the main plots (permanent broad bed furrow, PBBF, and conventional tillage, CT) and eight ABMs, each with three replications. The results indicated that PBBF and ABMs (seed inoculation with the microbial strains MDSR 14 + MDSR 34, and soil and foliar application of Zn+Fe) improved soil carbon stock (by 49.6% and 52.4%), available nitrogen, phosphorus, potassium, available Zn (by 30.0%), and Fe (by 21.9%) after the fourth year of the study. Similarly, PBBF and microbial inoculation increased soil enzyme activities (dehydrogenase, acid phosphatase, and beta-glucosidase), substrate-induced respiration, and microbial biomass carbon content. As a result, a higher soybean equivalent yield (5.59% higher in PBBF and 14.2% higher with foliar spray of Zn+Fe) and seed quality attributes (crude protein yield, grain Zn, and Fe) were observed in PBBF and the foliar spray of Zn and Fe treatments compared to CT and control, respectively. Overall, adopting the short-term PBBF system, microbial inoculation, and soil and foliar application of Zn and Fe improved rhizosphere biochemical properties, yield, and seed quality in the soybean-wheat system. The field study was conducted to assess the short-term effects of permanent broad bed furrow (PBBF) and agronomic biofortification methods (ABMs) under the soybean-wheat system. PBBF and ABMs improved soil quality indicators, resulting in the highest soybean equivalent yield and enhanced seed quality attributes. Therefore, PBBF and ABMs are recommended for farmers' adoption to address soil nutrient deficiencies and human malnutrition. image

The importance of soil sustainability in achieving sustainable development goals and global environmental agreements has been widely recognized. Understanding the biological processes of soil is crucial to decipher the soil-climate feedback mechanism. Soil metabolomics is a scientific study of low molecular weight metabolites in soil, both known and unknown, and is a potential application to assess the metabolic-scenario within the soil biological community. Although soil metabolomics has been applied in assessing different aspects of soil processes, it is still in its infancy, contributing to only a small percentage of published papers on metabolomics approaches. This highlights the need for further research and focus in this area. This review discusses the emerging perception of soil metabolite dynamics and its significance in soil ecosystem function. It covers the different groups of metabolites present in soil, extraction procedures, methodological biases, and advanced instrumentation for analysis. Targeted and untargeted metabolomics techniques are presented, with nuclear magnetic resonance (NMR) and mass spectrometry (MS) found to be the most widely used methods. The review also explores soil metabolomics application in various soil ecosystem services. Water-soluble, bio-available metabolites, and volatile metabolites are found to be the most crucial info chemicals underlying soil-plant-microbe interactions. Soil metabolomics has also been successful in characterizing soil organic matter and humus in terms of low molecular weight metabolites, indicating the direct contribution of microbes in stable organic matter formation. Additionally, it has helped in deciphering signature metabolites in response to ecotoxicity imparted by heavy metals, nanoparticles, and other soil pollutants. The strengths and weaknesses of metabolomics approaches are also discussed. Finally, key research prospects are highlighted to further improve our understanding of soil metabolomics' application in providing soil ecosystem services.

To ensure the sustainability of crop production and ecosystem functioning, a thorough understanding of the mechanisms governing soil carbon (C) sequestration and soil health is essential. This study examined the effects of three nutrient management practices (organic, inorganic, and integrated) and two cropping systems (soybean-wheat and soybean-chickpea), on arbuscular mycorrhizal fungi (AMF) and soil C-sequestration in a long-term (12 years) field experiment. We measured the stocks of soil organic carbon, total glomalin–related soil protein, pertinent soil quality parameters such as microbial biomass carbon, and β-glucosidase activity along with AMF biomass [microscopic parameters and 16:1ω5cis phospholipid fatty acid (AM PLFA) and neutral lipid fatty acid (AM NLFA)]. It was observed that the measures of AMF biomass were positively correlated with the soil organic carbon stocks, total glomalin–related soil protein stocks, and soil quality parameters. Organic practice recorded significantly higher AMF spores, mycorrhizal colonization percentage, AM PLFA (2.58 nmol g−1 soil), AM NLFA (7.95 nmol g−1 soil), soil organic carbon stocks (15.78 Mg ha−1), total glomalin–related soil protein stocks (2.10 Mg ha−1), and soil quality parameters such as microbial biomass carbon, and β-glucosidase activity than inorganic and integrated practices. In comparison to soybean-chickpea, C-sequestration was higher in soybean-wheat. Principal component analysis validated the said results and differentiated soybean-wheat under organic practice from the rest of the treatments. In conclusion, our results suggest that organic management in conjunction with soybean-wheat crop rotation enhances AMF and can be recommended for improving soil quality and C sequestration without compromising crop yield.

There are fewer studies on Trichoderma diversity in agricultural fields. The rhizosphere of 16 crops was analyzed for Trichoderma species in 7 districts of Rajasthan state of India. Based on DNA sequence of translation elongation factor 1α (tef-1α), and morphological characteristics, 60 isolates were identified as 11 species: Trichoderma brevicompactum, species in Harzianum clade identified as T. afroharzianum, T. inhamatum, T. lentiforme, T. camerunense, T. asperellum, T. asperelloides, T. erinaceum, T. atroviride, T. ghanense, and T. longibrachiatum. T. brevicompactum is the most commonly occurring strain followed by T. afroharzianum. No new species were described in this study. T. lentiforme, showed its first occurrence outside the South American continent. The morphological and cultural characteristics of the major species were observed, described, and illustrated in detail. The isolates were tested for their antagonistic effect against three soilborne plant pathogens fungi: Sclerotium rolfsii, Rhizoctonia solani, and Fusarium verticillioides in plate culture assays. One of the most potent strains was T. afroharzianum BThr29 having a maximum in vitro inhibition of S. rolfsii (76.6%), R. solani (84.8%), and F. verticillioides (85.7%). The potential strain T. afroharzianum BThr29 was also found to be efficient antagonists against soil borne pathogens in in vivo experiment. Such information on crop selectivity, antagonistic properties, and geographic distribution of Trichoderma species will be beneficial for developing efficient Trichoderma-based biocontrol agents.

The term “biological control” or “Biocontrol” have been used in different fields of biology, most notably Entomology and Plant Pathology. The organism that suppresses the pest or pathogen is referred to as the biological control agents (BCAs) which are used now-a-days instead of Biopesticides. Many terms have been used for this technology. Among the agents some also can increase plant growth, so these should be considered as plant growth promoting agents. Since the current day emphasis is on sustainable agriculture therefore, possibility of seed/planting material treatment and biopriming of nurseries with biopesticides/ BCAs should be given priority at all levels. The biological control agents have been used singly and in consortium as the advancement in biological control strategies are expanded. Different microbial consortia can also be used for better control of plant diseases. Species of the multifaceted microbes viz., Trichoderma , Aspergillus , Penicillium , Mycorrhiza , Bacillus , Pseudomonas etc. registered in various formulations (granular/liquid) and marketed in various trade names, are such examples which may be included in any category. Manufacturers and marketing agents are selling diverse range of biologicals for crop protection. Selection and improvisation of biological agents is a very important task before it is commercialized. The release of microbial strains requires a detailed research including morphology, biochemistry, lab, greenhouse and field evaluation. The strains need to be registered in a government regulatory organization so that the commercialization becomes effective. Changing roles and new terminologies of microbe(s) based products, is challenging to both, academicians, and regulatory authorities due to extensive procedures and expensive registration. An optimistic hope would be a simplified procedure and less expensive registration to support and develop biologicals-based products for growers. Challenges like microbial sustainability, compatibility, application for seed, field, spray without contamination or loss of microbes from mixing with natural resources are the focus of research, academics, and industry.

Sclerotium rolfsii Sacc. is one of the important soil borne pathogen causing stem rot of groundnut prevalent in all growing area worldwide. The present study aimed on the identification of native Trichoderma isolates, and its efficacy against the stem rot pathogen in groundnut at field level. Thirty-five isolates of Trichoderma spp. isolated from the groundnut rhizosphere were comparatively evaluated for their biocontrol potential against S. rolfsii Sacc. and growth promoting traits in groundnut. The morphological studies of the 35 isolates were supported molecularly by amplifying of ITS region and classified into four species namely, T. asperellum, T. citrinoviride, T. longibrachiatum and T. harzianum which were further subjected to biocontrol efficacy tests. The highly efficient representative isolates namely, T. harzianum Thar23, T. asperellum Tasp49, T. longibrachiatum Tlongi5 and T. citrinoviride Tcitri2 were evaluated to produce lytic enzymes and growth promoting traits. The comparative study of these isolates revealed that, T. harzianum Thar23 produced significant (P < 0.05) amount of lytic enzymes viz., chitinase (31.36 U/ml), β 1, 3 glucanase (4.1 U/ml) and protease (2.76 U/ml). T. harzianum Thar23 promotes plant growth traits namely germination efficacy (31.48

Drought is the most important factor limiting the activity of rhizobia during N-fixation and plant growth. In the present study, we isolated Bradyrhizobium spp. from root nodules of higher trehalose-accumulating soybean genotypes and examined for moisture stress tolerance on a gradient of polyethylene glycol (PEG 6000) amended in yeast extract mannitol (YEM) broth. In addition, the bradyrhizobial strains were also evaluated for symbiotic effectiveness on soybean. Based on 16S rDNA gene sequences, four bradyrhizobial species were recovered from high trehalose-accumulating genotypes, i.e., two Bradyrhizobium liaoningense strains (accession number KX230053, KX230054) from EC 538828 and PK-472, respectively, one Bradyrhizobium daqingense (accession number KX230052) from PK-472, and one Bradyrhizobium kavangense (accession number MN197775) from Valder genotype having low trehalose. These strains, along with two native strains, viz., Bradyrhizobium japonicum (JF792425), Bradyrhizobium liaoningense (JF792426), and one commercial rhizobium, were studied for nodulation, leghaemoglobin, and N-fixation abilities on soybean under sterilized sand microcosm conditions in a completely randomized design. Among all the strains, D-4A (B. daqingense) followed by D-4B (B. liaoningense) was found to have significantly higher nodulation traits and acetylene reduction assay (ARA) activity when compared to other strains and commercial rhizobia. The bradyrhizobia isolates showed plant growth promotion traits such as indole acetic acid (IAA), exopolysaccharide (EPS), and siderophore production, phosphate-solubilizing potential, and proline accumulation. The novel species B. daqingense was reported for the first time from Indian soil and observed to be a potential candidate strain and should be evaluated for conferring drought tolerance in soybean under simulated stress conditions.

Micronutrient silicon (Si) is receiving increasing attention in agriculture for its benefits to plant growth and stress tolerance. Plants have developed a highly efficient Si-transport mechanism that entails the localization of Si-transporter proteins such as Low silicon1 (Lsi1), Low silicon2 (Lsi2), Low silicon3 (Lsi3), and Low silicon6 (Lsi6), as well as the expression profiling that establishes a highly coordinated network between these proteins, facilitating Si uptake and accumulation. It has also been discovered that silicon (Si) can promote plant growth and alleviate a variety of biological and abiotic stressors. In this review paper, the effects of Si on plant–pathogen interactions are analyzed from physical, biochemical, and molecular perspectives. The addition of silica improves the plant’s physiological and chemical characteristics, including its defence mechanisms, hormonal modulation, and gene expression patterns. Si activates defence-related enzymes, promotes the production of antimicrobial compounds, regulates signal pathways, and induces the expression of defence-related genes. This results in combined resistance that dominates the biochemical/molecular resistance during plant–pathogen interactions. Furthermore, Si alleviates the toxic effects of abiotic stresses such as salt stress, drought, and heavy metals. Silicon’s ability to manage various plant stressors, the mechanisms of silicon-enhanced resistance and silicon’s inhibitory effects on pathogens in vitro are also discussed in this review paper. By integrating the information presented, a clear relationship between silicon treatments and plant growth promotion can be established. This information is valuable for understanding the role of Si in agriculture and improving the utilization of Si fertilizers and sources for agricultural production.

To meet UN 2030’s agenda for Sustainable Development Goals (SDGs), the use of non-renewable bioresources is being campaigned globally to ensure food security and resource sustainability while minimizing environmental impact. Among oilseeds, soybean is the most important leading oilseed crop worldwide and being a high rich seed protein (40%) crop requires high N for its growth. Its requirement is largely met through biological nitrogen fixation (BNF) and to certain extent from native pool. BNF in soybean takes place via specific N fixing symbiotic bacteria (e.g., bradyrhizobia) inside the root nodules of the plant-soil rhizosphere (rhizobiome) wherein other microbes such as arbuscular mycorrhizal (AM) fungi are also actively involved in performing various soil functions. However, during crop growth, BNF activity is limited by number of environmental and ecological factors. Amongst all, drought and nutritional stress are the most limiting factors affecting the productivity of soybean. Hence to mitigate the adverse conditions, improve soil biological health and overall productivity there is need to have well adapted microbial symbionts such as super nodulating and moisture tolerant soybean rhizobia and AM fungi for sustaining the productivity of soybean.

Arbuscular mycorrhizal fungi (AMF) form a mutualistic symbiosis with the roots of more than 80% of plants. These fungi provide numerous benefits to the plants, viz., improved uptake of mineral nutrients, plant growth, soil carbon sequestration, and confers resistance to biotic and abiotic stresses in plants. AMF functioning and diversity is immensely altered by chemical fertilizers, soil disruption, and cropping pattern. Admittance of appropriate crop and soil management practices for maintaining a high population 54and functioning of indigenous resident AMF would help in sustaining plant productivity under different ecosystems. Studies have indicated that the application of organic fertilizers with reduced tillage practices under particular crop sequences and selecting the efficient AMF strain are acting as potential drivers for AMF functioning. This chapter focuses on: (i) the status of distribution of functional diversity of AMF in agroecosystems; (ii) crop and soil management practices as key drivers affect the AMF diversity; and (iii) cautions for commercial exploitation of AMF biodiversity for application in sustaining the plant productivity.

Endophytes trigger various defence mechanisms within their host plants, engaging primary and secondary protective pathways. This investigation primarily aimed to isolate bacterial endophytes from diverse agroecological regions in Karnataka. Subsequently, these endophytes were assessed for their inhibition against Colletotrichum truncatum using the in-vitro streak plate technique. A total of 43 bacteria isolated from soybean plants and key endophytes showing the inhibition against C. truncatum were in different zones namely, DHW-9(87%), BID-2(85%), BID-13(85%), BID-14(82.50%), DHW-15(80%), BID-15(75%),and BID-16(75%) exhibited notable efficacy against C. truncatum in decreasing order. Among these, the DHW-9 (Stenotrophomonas maltophilia strain P4-32) bacterial endophytes isolated from the North Transition Zone (Dharwad) were highly effective against the pathogen, possibly due to employing many direct and indirect mechanisms. Furthermore, the inhibition potential of the bacterial endophytes varies with and within the place of agroecological zones. In conclusion, it has been observed that the bacterial endophyte DHW-9 inhibited the progression of anthracnose disease caused by C. truncatum in controlled in vitro. Hence, it is imperative to conduct additional experiments, including pot and field studies, to explore its potential to enhance the growth and yield of soybean plants.

The study aims to understand the effect of UV exclusion and arbuscular mycorrhizal fungi (AMF) inoculation on the photosynthetic parameters of soybean. The study was conducted in nursery bags and plants were grown under iron mesh covered with UV cut-off filters. The plants grown under the exclusion of UV with AMF inoculation (I) showed higher photosynthetic pigments, carbonic anhydrase activity, reduced internal CO2 concentration, enhanced transpiration rate, and stomatal conductance as well as improved photosynthetic rate over uninoculated plants. Moreover, -UVB+I and -UVAB+I plants exhibited an increased performance index, the activity of the water-splitting complex on the donor side of PSII, and the concentration of active PSII reaction centers per excited cross-section. Overall, UV-excluded and AMF-inoculated plants showed the highest quantum yield of PSII and rate of photosynthesis. Our study will pave the way for future investigation to identify the possible role of UV exclusion and AMF in improving the photosynthetic performance for better yield of soybean.