Novel moisture retaining dustable powder containing Steinernema abbasi effectively controls damage of subterranean termite in wheat and chickpea

The application of biocontrol agents in farm operations for pest control programs is gaining priority and preference globally. Effective delivery, infectivity of the biocontrol agents, and quality shelf-life products containing these bioagents are vital parameters responsible for the success of biopesticides under field conditions. In the present study, moisture-retaining bio-insecticidal dustable powder formulation (SaP) of Steinernema abbasi (Sa) infective juveniles (IJs) was developed and assessed for its shelf life, physicochemical profile, and bio-efficacy against subterranean termite under field conditions. Formulation exhibited free-flowing character, with pH of 6.50-7.50, and apparent density in the range 0.50-0.70 g cm-3. The bioefficacy study for two rabi seasons (2020-2021, and 2021-2022) in wheat and chickpea grown in an experimental farm heavily infested with subterranean termites (Odontotermes obesus) revealed a significant reduction in plant damage due to pest attack in formulation-treated plots, monitored in terms of relative number of infested tillers in wheat and infested plants in chickpea fields. The reduced damage to the crop caused by termite was reflected in the relative differences in the growth and yield attributes as well. The study establishes the potential of the developed product as a biopesticide suitable for organic farming and integrated pest management operations.

Performance appraisal of Trichoderma viride based novel tablet and powder formulations for management of Fusarium wilt disease in chickpea

In developing a Trichoderma viride-based biocontrol program for Fusarium wilt disease in chickpea, the choice of the quality formulation is imperative. In the present study, two types of formulations i.e. powder for seed treatment (TvP) and tablet for direct application (TvT), employing T. viride as the biocontrol agent, were evaluated for their ability to control chickpea wilt under field conditions at three dosages i.e. recommended (RD), double of recommended (DD) and half of recommended (1/2 RD). A screening study for the antagonistic fungi strains based on volatile and non-volatile bioassays revealed that T. viride ITCC 7764 has the most potential among the five strains tested (ITCC 6889, ITCC 7204, ITCC 7764, ITCC 7847, ITCC 8276), which was then used to develop the TvP and TvT formulations. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of volatile organic compounds (VOCs) of T. viride strain confirmed the highest abundance of compositions comprising octan-3-one (13.92%), 3-octanol (10.57%), and 1-octen-3-ol (9.40%) in the most potential T. viride 7764. Further Physico-chemical characterization by standard Collaborative International Pesticides Analytical Council (CIPAC) methods revealed the optimized TvP formulation to be free flowing at pH 6.50, with a density of 0.732 g cm^-3. The TvT formulation showed a pH value of 7.16 and density of 0.0017 g cm^-3 for a complete disintegration time of 22.5 min. The biocontrol potential of TvP formulation was found to be superior to that of TvT formulation in terms of both seed germination and wilt incidence in chickpea under field conditions. However, both the developed formulations (TvP and TvT) expressed greater bioefficacy compared to the synthetic fungicide (Carbendazim 50% WP) and the conventional talc-based formulation. Further research should be carried out on the compatibility of the developed products with other agrochemicals of synthetic or natural origin to develop an integrated disease management (IDM) schedule in chickpea.

Biopolymeric superabsorbent hydrogels enhance crop and water productivity of soybean-wheat system in Indo-Gangetic plains of India

Environmental crises, declining factor productivity, and shrinking natural resource is a threat to global agricultural sustainability. The task is much more daunting in the Indo-Gangetic northern plains of India, where depletion of the underground water table and erratic rains due to the changing climate pose a major challenge to agriculture. To address these challenges a field investigation was carried out during 2016-2018 to test the efficacy of biopolymeric superabsorbent hydrogels namely Pusa Hydrogel (P-hydrogel: a semi-synthetic cellulose derivative-based product) and kaolin derivative of Pusa Hydrogel (K-hydrogel: semi-synthetic cellulose derivative) to assess their effect on crop and water productivity, soil moisture, root dynamics, and economics of soybean (Glycine max L.)-wheat (Triticum aestivum L.) system under three irrigation regimes namely full irrigation, limited irrigation and rainfed. The results revealed that the full irrigation along with P-hydrogel led to enhanced grain yield, biomass yield, and water productivity (WP) of soybean (1.61-10.5%, 2.2-9.5%, and 2.15-21.8%, respectively) and wheat (11.1-18.3%, 12-54% and 11.1-13.1%, respectively) over control plots. Likewise, under water stressed plots of rainfed conditions with P-hydrogel exhibited 52.7 and 20.6% higher system yields (in terms of wheat equivalent yield) over control and other combinations during the respective study years. Whereas the magnitude of increase in system yield under limited irrigation with P-hydrogel was ~ 15.1% and under full irrigation with P-hydrogel was 8.0-19.4%. Plots treated with P-hydrogel retained 3.0-5.0% higher soil moisture compared to no-hydrogel plots, while K-hydrogel treated plots held the lower moisture (4.0-6.0%) than the control. In terms of profitability, full irrigation along with P-hydrogel plots registered 12.97% higher economic returns over control. The results suggested that P-hydrogel (2.5 kg ha-1) reduces runoff water loss in full irrigation applied plots and retained more water, where loss of water is more thus reduces number of irrigations. Hence P-hydrogel with irrigation water is a viable option for sustainable production of soybean-wheat systems in the Indo-Gangetic plains of India and other similar eco-regions of the world.

Brassica nigra essential oil: In-vitro and in-silico antibacterial efficacy against plant pathogenic and nitrifying bacteria

The present study was aimed to examine the antibacterial potential of Brassica nigra essential oil (BNEO) against Ralstonia solanacearum, causal agent of bacterial wilt and Nitrosomonas sp., the nitrifying bacteria. In poisoned food assay, BNEO showed 100% growth inhibition of R. solancearum at ≥ 125 µg mL^-1. Revalidation of findings by volatile assay employing inverted Petri plate technique exhibited 100% bacterial growth inhibition caused by vapors of BNEO, even at 50 µg mL^-1 concentration. In the broth microdilution assay, the BNEO exhibited significant antibacterial activity only at higher concentrations (>500 µg mL^-1). At 500 µg mL^-1, BNEO showed 80% bacterial growth inhibition over control, which was at par with that of streptomycin (5 µg mL^-1). In resazurin microtitre-plate assay, the maximum concentration of BNEO, at which color change occurred was 512 µg mL^-1 (T9), and thus 512 µg mL^-1 was concluded as the minimum inhibitory concentration (MIC). BNEO effectively inhibited the activity of Nitrosomonas spp. with 30-65% nitrification inhibition at the dose of 400 mkg^-1 of Urea-N. Homology modeled protein targets assisted computational tool-based novel analysis helped to understand that the antibacterial potency of BNEO is due to preferable binding efficiency of allyl isothiocyanate (AITC), the major active ingredient of BNEO.

Development of a QuEChERS-LCMS/MS method for simultaneous estimation of tebuconazole and chlormequat chloride in wheat crop

Tebuconazole (TBZ) and Chlormequat chloride (CCC) combination has been established as highly effective in reducing plant height of lodging prone wheat varieties. In this work, a novel analytical method employing the quick, easy, cheap, effective, rugged and safe (QuEChERS) cleanup technique and LC-MS/MS (liquid chromatography-tandem mass spectroscopy) was developed for simultaneous estimation of TBZ and CCC in wheat grains and harvest stage plant leaves. A total of 10 mL of acetonitrile and 50 mg of primary secondary amine (PSA) sorbent was consumed in the optimized QuEChERS process for leaves and grain samples. The LC-MS/MS analysis was performed using a C-18 column operating under electrospray ionization in positive mode. The QuEChERS approach achieved extraction recoveries in the acceptable range of 70%-120%, for both the compounds and was validated in terms of accuracy, precision, sensitivity and linearity. Persistence study was conducted using Lihocin (CCC 50% SL), Folicur (TBZ 25.9% EC) and their combination tank mix (Lihocin + Folicur-50% SL + 25.9% EC) applied as foliar spray twice in wheat crop (tester tall variety C-306). The results demonstrated that the developed QuEChERS-LCMS/MS is rapid and confirmatory for simultaneous quantification of both the test analytes in wheat crop.

Deciphering the Behavioral Response of Meloidogyne incognita and Fusarium oxysporum Toward Mustard Essential Oil

Environmental concerns related to synthetic pesticides and the emphasis on the adoption of an integrated pest management concept as a cardinal principle have strengthened the focus of global research and development on botanical pesticides. A scientific understanding of the mode of action of biomolecules over a range of pests is key to the successful development of biopesticides. The present investigation focuses on the in silico protein-ligand interactions of allyl isothiocyanate (AITC), a major constituent of black mustard (Brassica nigra) essential oil (MEO) against two pests, namely, Meloidogyne incognita (Mi) and Fusarium oxysporum f. sp. lycopersici (Fol), that cause severe yield losses in agricultural crops, especially in vegetables. The in vitro bioassay results of MEO against Mi exhibited an exposure time dependent on the lethal concentration causing 50% mortality (LC₅₀) values of 47.7, 30.3, and 20.4 μg ml^-1 at 24, 48, and 72 h of exposure, respectively. The study revealed short-term nematostatic activity at lower concentrations, with nematicidal activity at higher concentrations upon prolonged exposure. Black mustard essential oil displayed excellent in vitro Fol mycelial growth inhibition, with an effective concentration to cause 50% inhibition (EC₅₀) value of 6.42 μg ml^-1. In order to decipher the mechanism of action of MEO, its major component, AITC (87.6%), which was identified by gas chromatography-mass spectrometry (GC-MS), was subjected to in silico docking and simulation studies against seven and eight putative target proteins of Mi and Fol, respectively. Allyl isothiocyanate exhibited the highest binding affinity with the binding sites of acetyl cholinesterase (AChE), followed by odorant response gene-1 (ODR1) and neuropeptide G-protein coupled receptor (nGPCR) in Mi, suggesting the possible suppression of neurotransmission and chemosensing functions. Among the target proteins of Fol, AITC was the most effective protein in blocking chitin synthase (CS), followed by 2,3-dihydroxy benzoic acid decarboxylase (6m53) and trypsinase (1try), thus inferring these as the principal molecular targets of fungal growth. Taken together, the study establishes the potential of MEO as a novel biopesticide lead, which will be utilized further to manage the Mi-Fol disease complex.

Preparation of Nanofungicides Based on Imidazole Drugs and Their Antifungal Evaluation

In spite of modern crop protection measures, the overall crop losses due to pests and pathogens are huge. Rhizoctonia solani, Macrophomina phaseolina, Sclerotium rolfsii, and Fusarium oxysporum are one of the most devastating soil-borne fungi and cause numerous plant diseases. Therefore, the present study aimed to systematically design and develop new nanofungicides based on imidazole drugs, clotrimazole, econazole nitrate, and miconazole nitrate, for effective and efficient management of plant diseases. The assessment of these antifungal medicines for their fungicide likeness using Hao's rule and their enzyme inhibitory potential by molecular docking was helpful in ensuring their utility as antifungal agents in managing phytopathogenic fungi. Nanotechnological strategies were used to develop nanoformulations of test compounds in poly(ethylene glycol) 300 for further augmenting their bioactivity. Transmission electron microscopy studies confirmed the nanosize of the prepared products. Analysis of their in vitro and in vivo antifungal properties revealed their usefulness in controlling the test fungi, R. solani, M. phaseolina, S. rolfsii, and F. oxysporum. Excellent in vitro antifungal activities were displayed by the clotrimazole nanoformulation with a median effective dose (ED₅₀) of 1.18 μg/mL against R. solani, the econazole nitrate nanoformulation with an ED₅₀ of 5.25 μg/mL against S. rolfsii, and the miconazole nitrate nanoformulation with an ED₅₀ of 1.49 and 1.82 μg/mL against M. phaseolina and F. oxysporum. Furthermore, in vivo studies against test fungi demonstrated the antifungal potency of all the nanoformulations with disease incidences ranging from 11.11 to 27.38% in plants treated with nanoformulations of test chemicals as compared to the inoculated control (39.68-72.38%).

A Comprehensive in vitro and in silico Analysis of Nematicidal Action of Essential Oils

Nematicidal potential of essential oils (EOs) has been widely reported. Terpenoids present in most of the essential oils have been reported responsible for their bioactivity though very less is known about their modes of action. In the present study, an in vitro screening of nine Eos, namely, Citrus sinensis (OEO), Myrtus communis (MTEO), Eucalyptus citriodora (CEO), Melaleuca alternifolia (TEO), Acorus calamus (AEO), Commiphora myrrha (MREO), Cymbopogon nardus (CNEO), Artemisia absinthium (WEO), and Pogostemon cablin (PEO) against Meloidogyne incognita revealed OEO, CNEO, and TEO as most effective with LC₅₀ 39.37, 43.22, and 76.28 μg ml^-1 respectively. EOs had varying compositions of mono- and sesquiterpenes determined by gas chromatography-mass spectrometry (GC-MS) analysis. The in silico molecular interactions screening of major EO constituents and the seven selected target proteins of the nematode indicated highest binding affinity of geraniol-ODR1 (odorant response gene 1) complex (ΔG = -36.9 kcal mol^-1), due to extensive H-bonding, hydrophobic and π-alkyl interactions. The relative binding affinity followed the order: geraniol-ODR1 > β-terpineol-ODR1 > citronellal-ODR1 > l-limonene-ODR1 > γ-terpinene-ODR1. Taken together, the cumulative in vitro and computational bioefficacy analysis related to the chemoprofiles of EOs provides useful leads on harnessing the potential of EOs as bionematicides. The insight on biochemical ligand-target protein interactions described in the present work will be helpful in logical selection of biomolecules and essential oils for development of practically viable bionematicidal products.

Neurological deficit following stereotactic radiosurgery for trigeminal neuralgia

We report a unique case of neurological deficit from late onset multiple sclerosis (MS), in a 65-year-old woman, after stereotactic radiosurgery (SRS) for trigeminal neuralgia (TN). At 3.5months post-SRS for TN, the patient developed ataxia and left leg paraesthesiae and brain MRI showed altered signal and enhancement in the vicinity of the right trigeminal root entry zone (REZ). The symptoms remitted following treatment with intravenous methylprednisolone, however, 10months post-SRS, the patient developed gait ataxia and left lower limb weakness. MRI showed persistent T2 changes at the REZ and multiple new non-enhancing white matter lesions in the cerebrum and spinal cord; and oligoclonal bands were present in the cerebrospinal fluid but not serum. A diagnosis of multiple sclerosis (MS) was made. This report raises the issue of whether the risk of radiation-induced toxicity is increased in patients with MS treated with SRS. We hypothesise that breakdown in the blood brain barrier secondary to the radiosurgery may have triggered a vigorous local inflammatory response.