Incorporation of zinc sulfide nanoparticles, Acinetobacter pittii and Bacillus velezensis to improve tomato plant growth, biochemical attributes and resistance against Rhizoctoniasolani.

Green nanobiotechnology and beneficial bacterial strains as biofertilizers are crucial in agriculture to achieve food security. Both these strategies have been individually studied in improving plant resistance against phytopathogens along with enhancing plant productivity. Therefore, objective of this study was to explore the eco-friendly and cost-effective approach of utilizing plant growth promoting and disease suppressing bacterial strains and nanoparticles, individually as well as in combination, as bio-stimulants to improve plant growth, antioxidant defense system, nutrition and yield of tomato. A pot experiment was conducted to investigate the zinc sulfide nanoparticles (ZnS NPs) synthesized by using Jacaranda mimosifolia flower extracts (JFE), Acinetobacter pittii and Bacillus velezensis either individually or in combinations to check their potential against Rhizoctonia solani in tomato to suppress root rot infection and improve growth and yield. Among all the combinations the JFE-ZnS NPs + B. velezensis compared to untreated infected plants showed minimum disease incidence and maximum significant protection (66%) against R. solani instigated root rot that was followed by JFE-ZnS NPs + A. pittii and individual application of JFE-ZnS NPs by 58%. The same treatment showed maximum significant increase in plant fresh and dry biomass. B. velezensis significantly increased the photosynthetic pigments when applied individually. However, JFE-ZnS NPs alone and in mixed treatments with B. velezensis efficiently improved total soluble protein, sugar and phenolic contents. The same interactive application of JFE-ZnS NPs + B. velezensis improved the tomato plant nutrition (silicon (Si), magnesium (Mg), calcium (Ca) and potassium (K)) and redox quenching status by improving the activity of antioxidant defense enzymes. Overall, the interactive use of JFE-ZnS NPs with A. pittii and B. velezensis very appropriately prepared the host plant to fight against the negative effects of root rot pathogen in tomato. Advancements in interactively investigating the nanoparticles with beneficial plant growth promoting bacterial strains importantly can contribute in resolving the challenges of food security. According to our information, this is a pioneer report for implying JFE-ZnS NPs in synergism with A. pittii and B. velezensis to hinder the root rot in tomatoes.

Biocontrol of Rhizoctonia solani in basmati rice by the application of Lactobacillus and Weissella spp.

Rice is a staple food crop and is a major source of employment and income in the world. However, the attack of fungal disease poses a serious threat to the crop growth and productivity and leads toward yield loses. Therefore, current study was performed to evaluate the biocontrol potential of Lactobacillus and Weissella spp. on basmati rice against Rhizoctonia solani. Agar disc method was performed to evaluate the antifungal activity of both bacteria against R. solani. Petri plate and pot experiments were conducted to evaluate the growth promotion and biocontrol potential of both bacteria in Basmati rice under R. solani stress. Results indicated that maximum antifungal activity (82%) was recorded by Lactobacillus sp. Maximum phosphate solubilization and siderophore production was recorded by Weissella sp. In petri plate experiment, maximum root length, root fresh and dry weight (36%, 40% and 13%) was recorded by Weissella sp. and maximum shoot length and shoot fresh weight (99% and 107%) by Lactobacillus sp. In pot experiment, both bacteria enhanced the growth parameters of Basmati rice including root and shoot length, fresh and dry weight as well as no. of lateral roots. Application of Weissella sp. resulted in maximum increase (332% and 134%) in chlorophyll a and b content while Lactobacillus sp. + R. solani showed maximum (42%) carotenoid contents. Lactobacillus sp. + R. solani showed maximum increase in the proline (54%) and sugar contents (100%) while Lactobacillus sp. alone showed maximum (35%) soluble protein contents. Plant defense enzymes i-e SOD (400%), POD (25%), CAT (650%), PPO (14%) and PAL (124%) were notably increased by Weissella sp. + R. solani and Lactobacillus sp + R. solani. The Lactobacillus sp showed the best results in antifungal activity against R. solani and Weissella sp. showed the best results in production of defense enzymes in basmati rice against R. solani stress and can be suggested as the potent biocontrol agents for the rice crop.

Zinc oxide nanoparticles mediated biostimulant impact on cadmium detoxification and in silico analysis of zinc oxide-cadmium networks in Zea mays L. regulome.

Cadmium (Cd) toxicity can significantly limit plant growth and development. To eliminate the toxic effects of Cd stress, we intended to evaluate the biochemical mediated physiological responses in maize treated with biostimulant and zinc oxide nanoparticles (ZnPs). In silico analysis exhibited that the maize treated with Cd stress (200 µM) had an adverse impact on CAT1, CAT2, CAT3 and gor1 proteins, which are influential in managing the machinery of redox homeostasis. While maize inoculated with bacteria-based biostimulant and ZnPs (10 ppm) showed prominently improved biomass, chlorophyll a, b and carotenoid content. We found a significant increase in the total sugar, protein, proline content and antioxidants under the effect of Cd stress. However, these parameters are further enhanced by applying biostimulants and ZnPs. Declined lipid peroxidation and membrane solubilization index under the effect of biostimulant and ZnPs was observed. Furthermore, these treatments improved maize's zinc, copper, sodium, magnesium, iron, potassium and calcium content. Based on these results, an antagonistic relationship between Zn and Cd uptake that triggered efficient Cd detoxification in maize shoot was found. Scanning electron micrography showed distorted leaf structure of the Cd stressed plants while the biostimulant and ZnPs reduced the structural cell damage of maize leaves. In silico study showed that ZnO positively regulates all protein interactors, including GRMZM2G317386_P01 (Metallo endo proteinase 1-MMP), GRMZM2G110220_P01 (Metallo endo proteinase 5-MMP), GRMZM2G103055_P01 (Alpha-amylase) and GRMZM2G006069_P01 (Zn-dependent exo peptidase superfamily) proteins which are involved in energy generating processes, channels formation, matrix re-localization and stress response. This suggests that ZnO offers an ideal role with protein interactors in maize. Our findings depict that these treatments, i.e., biostimulant and ZnPs alone, are efficient enough to exhibit Cd remediation potential in maize; however, their combination showed synergistic effects.

Rhizosphere bacteria associated with Chenopodium quinoa promote resistance to Alternaria alternata in tomato.

Microorganisms can interact with plants to promote plant growth and act as biocontrol agents. Associations with plant growth-promoting rhizobacteria (PGPR) enhance agricultural productivity by improving plant nutrition and enhancing protection from pathogens. Microbial applications can be an ideal substitute for pesticides or fungicides, which can pollute the environment and reduce biological diversity. In this study, we isolated 68 bacterial strains from the root-adhering soil of quinoa (Chenopodium quinoa) seedlings. Bacterial strains exhibited several PGPR activities in vitro, including nutrient solubilization, production of lytic enzymes (cellulase, pectinase and amylase) and siderophore synthesis. These bacteria were further found to suppress the mycelial growth of the fungal pathogen Alternaria alternata. Nine bacterial strains were selected with substantial antagonistic activity and plant growth-promotion potential. These strains were identified based on their 16S rRNA gene sequences and selected for in planta experiments with tomato (Solanum lycopersicum) to estimate their growth-promotion and disease-suppression activity. Among the selected strains, B. licheniformis and B. pumilus most effectively promoted tomato plant growth, decreased disease severity caused by A. alternata infection by enhancing the activities of antioxidant defense enzymes and contributed to induced systemic resistance. This investigation provides evidence for the effectiveness and viability of PGPR application, particularly of B. licheniformis and B. pumilus in tomato, to promote plant growth and induce systemic resistance, making these bacteria promising candidates for biofertilizers and biocontrol agents.

Titanium Oxide and Zinc Oxide Nanoparticles in Combination with Cadmium Tolerant Bacillus pumilus Ameliorates the Cadmium Toxicity in Maize.

The efficiency of Cd-tolerant plant growth-promoting bacteria (PGPB), zinc oxide nanoparticles (ZnO NPs), and titanium dioxide nanoparticles (TiO2) in maize growing in Cd-rich conditions was tested in the current study. The best Cd-tolerant strain, Bacillus pumilus, exhibited plant growth stimulation in vivo and in vitro experiments. We determined the toxic concentrations (30 (ppm)) of both NPs for plant growth. B. pumilus, ZnO NPs (20 (ppm)), and TiO2 NPs (10 (ppm)) had a synergistic effect on plant growth promotion in Cd-contaminated soil (120 (ppm)) in a pot experiment. Both alone and in combination, these therapies reduced Cd toxicity, resulting in improved stress metabolism and defense responses. The combined treatments showed increased relative water content, photosynthetic pigments, proline, total sugars, and proteins and significantly reduced lipid peroxidation. Moreover, this combination increased the levels of minerals and antioxidants and reduced Cd bioaccumulation in shoots and roots by 40-60%. Our in silico pipeline presented a novel picture of the participation of ZnO-TiO2 protein interaction in both B. pumilus and maize. These findings provide fresh insights on the use of B. pumilus, ZnO, and TiO2 NPs, both separately and in combination, as a viable and environmentally benign strategy for reducing Cd stress in maize.

Phosphate solubilizing bacteria enhanced growth, oil yield, antioxidant properties and biodiesel quality of Kasumbha.

Biodiesel is considered as a potential alternative energy source, but problem exists with the quantity and quality of feedstock used for it. To improve the feedstock quality of biodiesel, a field experiment was conducted under natural conditions. Cultivar Thori of kasumbha was used in the experiment. Commercialized biofertilizers were applied at the rate of 20 kg per acre and chemical fertilizer (diammonium phosphate) was applied as half dose (15 kg/ha). Results indicated that number of leaf plant-1, leaf area, number of seeds capitulum-1 was significantly increased by biofertilizer treatment alone (BF) and combine treatment of biofertilizer and chemical fertilizer (BFCF). Agronomic traits such as plant height, no. of branches of a plant, no. of capitulum/plant was improved significantly by BF treatment over the control. Maximum 1000 seed weight (41%) and seed yield (23%) were recorded in half dose of chemical fertilizers treatment (CFH). Seed oil content and seed phenolics were significantly improved by BF and CF treatments while maximum biodiesel yield was recorded by BF treatment. Maximum oleic acid was recorded by BF treatment while other fatty acids being maximum in control except linoleic acid in BFCF treatment. Results for specific gravity were non-significant while acid value and free fatty acid contents were substantially reduced by BF treatment as compared to other treatments. Maximum value of iodine number was recorded in BFCF treatment while tocopherol contents were improved by BF treatment. It is inferred that biofertilizer treatment alone perform better as compared to other treatments and 50% chemical fertilizer can be replaced using biofertilizer which is a good approach for sustainable environmental-friendly agriculture.

Ameliorative effects of plant growth promoting bacteria, zinc oxide nanoparticles and oxalic acid on Luffa acutangula grown on arsenic enriched soil.

Arsenic (As) contamination and bioaccumulation are a serious threat to agricultural plants. To address this issue, we checked the efficacy of As tolerant plant growth promoting bacteria (PGPB), zinc oxide nanoparticles (ZnO NPs) and oxalic acid (OA) in Luffa acutangula grown on As rich soil. The selected most As tolerant PGPB i.e Providencia vermicola exhibited plant growth promoting features i.e solubilzation of phosphate, potassium and siderophores production. Innovatively, we observed the synergistic effects of P. vermicola, ZnO NPs (10 ppm) and OA (100 ppm) in L. acutangula grown on As enriched soil (150 ppm). Our treatments both as alone and in combination alleviated As toxicity exhibited by better plant growth and metabolism. Results revealed significantly enhanced photosynthetic pigments, proline, relative water content, total sugars, proteins and indole acetic acid along with As amelioration in L. acutangula. Furthermore, upregulated plant resistance was manifested with marked reduction in the lipid peroxidation and electrolyte leakage and pronounced antagonism of As and zinc content in leaves under toxic conditions. These treatments also improved level of nutrients, abscisic acid and antioxidants to mitigate As toxicity. This marked improvement in plants' defense mechanism of treated plants under As stress is confirmed by less damaged leaves cell structures observed through the scanning electron micrographs. We also found substantial decrease in the As bioaccumulation in the L. acutangula shoots and roots by 40 and 58% respectively under the co-application of P. vermicola, ZnO NPs and OA in comparison with control. Moreover, the better activity of soil phosphatase and invertase was assessed under the effect of our application. These results cast a new light on the application of P. vermicola, ZnO NPs and OA in both separate and combined form as a feasible and ecofriendly tool to alleviate As stress in L. acutangula.

Drought-tolerant Bacillus megaterium isolated from semi-arid conditions induces systemic tolerance of wheat under drought conditions.

KEY MESSAGE: A detailed study of the response of wheat plants, inoculated with drought-tolerant PGPR is studied which would be beneficial to achieve genetic improvement of wheat for drought tolerance. Drought stress, a major challenge under current climatic conditions, adversely affects wheat productivity. In the current study, we observed the response of wheat plants, inoculated with drought-tolerant plant growth-promoting rhizobacteria (PGPR) Bacillus megaterium (MU2) and Bacillus licheniformis (MU8) under induced drought stress. In vitro study of 90 rhizobacteria exhibited 38 isolates showed one or more plant growth-promoting properties, such as solubilization of phosphorus, potassium, and exopolysaccharide production. Four strains revealing the best activities were tested for their drought-tolerance ability by growing them on varying water potentials (- 0.05 to - 0.73 MPa). Among them, two bacterial strains Bacillus megaterium and Bacillus licheniformis showed the best drought-tolerance potential, ACC deaminase activities, IAA production, and antagonistic activities against plant pathogens. Additionally, these strains when exposed to drought stress (- 0.73 MPa) revealed the induction of three new polypeptides (18 kDa, 35 kDa, 30 kDa) in Bacillus megaterium. We determined that 106 cells/mL of Bacillus megaterium and Bacillus licheniformis were enough to induce drought tolerance in wheat under drought stress. These drought-tolerant strains increased the germination index (11-46%), promptness index (16-50%), seedling vigor index (11-151%), fresh weight (35-192%), and dry weight (58-226%) of wheat under irrigated and drought stress. Moreover, these strains efficiently colonized the wheat roots and increased plant biomass, relative water content, photosynthetic pigments, and osmolytes. Upon exposure to drought stress, Bacillus megaterium inoculated wheat plants exhibited improved tolerance by enhancing 59% relative water content, 260, 174 and 70% chlorophyll a, b and carotenoid, 136% protein content, 117% proline content and 57% decline in MDA content. Further, activities of defense-related antioxidant enzymes were also upregulated. Our results revealed that drought tolerance was more evident in Bacillus megaterium as compared to Bacillus licheniformis. These strains could be effective bioenhancer and biofertilizer for wheat cultivation in arid and semi-arid regions. However, a detailed study at the molecular level to deduce the mechanism by which these strains alleviate drought stress in wheat plants needs to be explored.

Drought-tolerant Pseudomonas sp. showed differential expression of stress-responsive genes and induced drought tolerance in Arabidopsis thaliana.

The growth and persistence of rhizobacteria in soils are highly impacted by moisture stress. In this study, we report the first transcript analysis of four Pseudomonas strains (PS1, PS2, PS3, and PS4) isolated from the root-soil interface of rice and maize associated with different moisture levels during water deprivation. Filtered Pseudomonas sp. cells incubated at low (RH10%) and high (RH85%) relative humidity showed decreased survival of all Pseudomonas sp. at RH10% when compared with RH85%. RT-PCR showed differential expression of treS (trehalose synthase), rpoS (sigma factor), mucA (alginate regulatory gene), and fliM (flagellar motor switch protein gene) in response to exposure to RH10%. However, molecular fingerprinting and nutrient assimilation profile of Pseudomonas strains demonstrated genetic and physiological variation between the four strains irrespective of water regime and host. In vitro testing of these strains showed ACC deaminase activity and gibberellic acid, abscisic acid, indole acetic acid, and exopolysaccharide production. We determined that 50 µl of 1.2 × 103 CFU ml-1 of these Pseudomonas strains was enough to protect Arabidopsis plants against drought stress in a pot experiment. Inoculated plants increased their root colonization ability and biomass; however, PS2 showed higher survival (95%), relative water content (59%), chlorophyll (30%), glycine betaine (38%), proline (23%), and reduced MDA (43%) in shoots than irrigated control under induced water deprivation. It can be concluded that all Pseudomonas strains were effective in mitigating drought stress, however, PS2 appears to impart more resistance to drought than the other strains by upregulating key defense mechanisms.

Comparative analysis of iron oxide nanoparticles synthesized from ginger (Zingiber officinale) and cumin seeds (Cuminum cyminum) to induce resistance in wheat against drought stress.

In the present study, iron oxide nanoparticles (Fe3O2-NPs) synthesized from ginger (Zingiber officinale) and cumin seeds (Cuminum Cyminum L.) extracts were investigated to reveal their potential to enhance the growth and drought resistance of wheat plants under drought stress. In an In Vitro experiment, four different concentrations for Fe3O2-NPs (0.3 mM, 0.6 mM, 0.9 mM, and 1.2 mM) of ginger and cumin seeds were tested. Among all the concentrations tested, ginger Fe3O2-NPs (0.6 mM) and cumin seeds Fe3O2-NPs (1.2 mM) were more effective to enhance wheat germination, biomass, and survival percentage under drought stress and irrigated conditions than the non-treated control plant. In a pot experiment, wheat plants under induced water stress showed marked up-regulation in the biochemical resistance mechanisms when treated with ginger Fe3O2-NPs (0.6 mM) and cumin seeds Fe3O2-NPs (1.2 mM) than the non-treated control. Cumin seeds Fe3O2-NPs (1.2 mM) were more effective than ginger Fe3O2-NPs (0.6 mM) in ameliorating adverse effects of drought stress in wheat. Results demonstrated that cumin seeds Fe3O2-NPs (1.2 mM) exhibited a higher increase in chlorophyll a, b and carotenoids (72%, 265% and 96% respectively), proline (127%), superoxide dismutase (115%), peroxidase (43.8%), ascorbate peroxidase (44.6%). This also showed higher reduction in lipid peroxidation, electrolyte leakage and increased soluble sugars and total Fe content in the roots and shoots than non-treated plants under drought. Hence, nano-priming can be considered an effective strategy for sustainable food production in marginal soils.

A strategy for mitigating avian colibacillosis disease using plant growth promoting rhizobacteria and green synthesized zinc oxide nanoparticles.

Avian colibacillosis caused by the zoonotic pathogen Escherichia coli is a common bacterial infection that causes major losses in the poultry sector. Extracts of different medicinal plants and antibiotics have been used against poultry bacterial pathogens. However, overuse of antibiotics and extracts against pathogenic strains leads to the proliferation of multi-drug resistant bacteria. Due to their environmentally friendly nature, nanotechnology and beneficial bacterial strains can be used as effective strategies against poultry infections. Green synthesis of zinc oxide nanoparticles (ZnO-NPs) from Eucalyptus globulus leaves was carried out in this study. Their characterization was done by UV-vis spectroscopy, X-ray diffraction (XRD), and Fourier transmission infrared spectroscopy (FT-IR) which confirmed their synthesis, structure, and size. In vitro, antimicrobial activities of plant leaf extract, ZnO-NPs, and plant growth-promoting rhizobacteria (PGPR) were checked against E. coli using well diffusion as well as disc diffusion method. Results proved that the antimicrobial activity of ZnO-NPs and PGPR strains was more enhanced when compared to eucalyptus leaf extract at 36 h. The maximum relative inhibition shown by ZnO-NPs, PGPR strains and eucalyptus leaf extracts was 88%, 67% and 58%, respectively. The effectiveness of ZnO-NPs was also increased with an increase in particle dose and treatment time. The 90 mg/ml of ZnO-NPs was more effective. PGPR strains from all over the tested strains, Pseudomonas sp. (HY8N) exhibited a strong antagonism against the E. coli strain as compared to other PGPR strains used in this study. However, combined application of PGPR (Pseudomonas sp. (HY8N)) and ZnO-NPs augment antagonistic effects and showed maximum 69% antagonism. The study intends to investigate the binding affinity of ZnO-NPs with the suitable receptor of the bacterial pathogen by in silico methods. The binding site conformations showed that the ligand ZnO binds with conserved binding site of penicillin-binding protein 6 (PBP 6) receptor. According to the interactions, ZnO-NPs form the same interaction pattern with respect to other reported ligands, hence it can play a significant role in the inhibition of PBP 6. This research also found that combining ZnO-NPs with Pseudomonas sp. (HY8N) was a novel and effective technique for treating pathogenic bacteria, including multidrug-resistant bacteria.

Exogenous silicon and hydrogen sulfide alleviates the simultaneously occurring drought stress and leaf rust infection in wheat.

Silicon (Si) and hydrogen sulfide (H2S) are known to enhance plant defense against multiple stresses. Current study was conducted to investigate the application of Si and H2S alone as well as in combination, improved physiological resilience of wheat plants to drought stress (DS) and pathogen-Puccinia triticina (Pt) infection. We aimed to increase the wheat plant growth and to enhance the DS tolerance and Pt resistance with the concurrent applications of H2S and Si. In the first experiment, we selected the best growth enhancing concentration of H2S (0.3 mM) and Si (6 mM) to further investigate their tolerance and resistance potential in the pot experiment under DS and pathogen infection conditions. The obtained results reveal that DS has further increased the susceptibility of wheat plants to leaf rust pathogen infection while, the sole application of Si and the simultaneous exogenous treatments of H2S + Si enhanced the plant growth, decreased disease incidence, and significantly improved tolerance and defense mechanisms of wheat under individual and interactive stress conditions. The exogenous treatment of H2S + Si improved the growth criteria, photosynthetic pigments, osmoprotectants, and defense related enzyme activities. The same treatment also reinforced the endogenous H2S, Si, ABA and SA contents while decreased the disease incidence and oxidative stress indicators under individual and combined stress conditions. Overall, results from this study presents the influence of combined drought and P. triticina stress in wheat and reveal the beneficial impacts of concurrent exogenous treatment of H2S + Si to mitigate the drought and pathogen (P. triticina) induced adverse effects.

Combined application of zinc oxide nanoparticles and biofertilizer to induce salt resistance in safflower by regulating ion homeostasis and antioxidant defence responses.

Salinity is a key devastating abiotic factor that hinders the development and yield of safflower. The sole and combined application of zinc oxide nanoparticles (ZnO-NPs) and a biofertilizer (BF) to improve salt tolerance in safflower has not been thoroughly explored. The response of safflower plants in a pot experiment to the foliar spray of ZnO-NPs alone and in combination with a BF was thus detected. We determined that a ZnO-NP concentration of 17 mg/L was sufficient to protect safflower against salinity (250 mM NaCl) by increasing the plant productivity, percent water content, and osmolyte levels. Coapplication of ZnO-NPs and Phytoguard protected safflower plants from salinity stress by improving the activities of antioxidant enzymes and decreasing the levels of proline (leaves (61%) and roots (63%)) and malondialdehyde (MDA) (leaves (54%) and roots (65%)). Under salt stress, the Na+ content increased, while seed coating with biofertilizer and ZnO-NP spray significantly decreased the Na+ concentration (74% in leaves and 60% in roots). For the K+ concentration, however, antagonistic outcomes were observed. Additionally, the combined treatment significantly enhanced agronomic parameters such as the number of leaves and pods per plant, capitulum weight, and the number of yellow and wilted leaves per plant under salinity stress. Thus, ZnO-NPs could be an effective bio-source for the protection of safflower plants under salinity stress. Our findings showed that in the combined treatment of ZnO-NPs and biofertilizer, the salinity tolerance was more pronounced than in the single treatment and untreated control. A thorough analysis at the molecular level, however, is still required to understand the mechanism by which ZnO-NPs and BF in safflower plants alleviate salt stress.

Combined ability of salicylic acid and spermidine to mitigate the individual and interactive effects of drought and chromium stress in maize (Zea mays L.).

Application of the growth regulator salicylic acid (SA) and the polyamine spermidine (Spd) can be used to manage various plant abiotic stresses. We aimed to evaluate the sole and combined effects of SA and Spd on maize (Zea mays) under individual and combined drought and chromium (Cr) stress. Drought, Cr, and drought + Cr treatments caused oxidative stress by inducing higher production of reactive oxygen species (H2O2, O2-), enhanced malondialdehyde content and increased relative membrane permeability. Increased oxidative stress and higher Cr uptake in the host plant reduced the content of carotenoids, other photosynthetic pigments and protein, and changed carbohydrate metabolism. Combined drought + Cr stress was more damaging for the growth of maize plants than the individual stresses. Exogenous treatments of SA and Spd alleviated the adverse effects of drought and Cr toxicity, reflected by accumulations of osmolytes, antioxidants and endogenous polyamines. Single applications of Spd (0.1 mM) increased plant height, shoot fresh weight, leaf area, above-ground dry matter accumulation and polyamine content under drought, Cr, and drought + Cr stress conditions. However, the combined treatment SA + Spd (0.25 mM + 0.05 mM) was more effective in increasing protein and water contents, photosynthetic pigments, and carotenoids. The same treatment increased Cr tolerance in the maize plants by decreasing uptake of this heavy metal from root to shoot. The SA + Spd treatment also decreased oxidative stress by promoting antioxidant enzyme activities, and enhanced levels of proline, soluble sugars, and carbohydrate contents under individual and combined stress conditions. Results indicate that the combined half-dose application of SA + Spd may be utilized to boost the tolerance in maize under individual as well as combined drought and Cr stress conditions.

Induction of defense-related enzymes and enhanced disease resistance in maize against Fusarium verticillioides by seed treatment with Jacaranda mimosifolia formulations.

Fusarium verticillioides is an important fungal pathogen of maize, causing stalk rot and severely affecting crop production. The aim of this study was to characterize the protective effects of formulations based on Jacaranda mimosifolia leaf extracts against F. verticillioides in maize. We compared different seed treatments comprising J. mimosifolia extracts, chemical fungicide (mefenoxam) and salicylic acid to modulate the defense system of maize host plants. Both aqueous and methanolic leaf extracts of J. mimosifolia (1.2% w/v) resulted in 96-97% inhibition of mycelial growth of F. verticillioides. While a full-dose (1.2%) extract of J. mimosifolia provided significant protective effects on maize plants compared to the inoculated control, a half-dose (0.6% w/v) application of J. mimosifolia in combination with half-strength mefenoxam was the most effective treatment in reducing stalk rot disease in pot and field experiments. The same seed treatment significantly upregulated the expression of genes in the leaves encoding chitinase, glucanase, lipid transfer protein, and pathogenesis-related proteins PR-1, PR-5 and PR-10, 72 h after inoculation. This treatment also induced the activities of peroxidase, polyphenol oxidase, protease, acid invertase, chitinase and phenylalanine ammonia lyase. We conclude that seed pre-treatment with J. mimosifolia extract with half-strength chemical mefenoxam is a promising approach for the management of stalk rot in maize.

Volatile organic compounds produced by Pseudomonas pseudoalcaligenes alleviated drought stress by modulating defense system in maize (Zea mays L.).

Research on plant growth-promoting bacteria (PGPR) revealed an effective role of bacterial volatile organic compounds (VOCs) in stress alleviation. Out of 15 PGPR strains, infection with VOCs from Pseudomonas pseudoalcaligenes' resulted in maximum germination, growth promotion, and drought tolerance in maize plants. The VOCs of P. pseudoalcaligenes caused induced systemic tolerance in maize plants during 7 days of drought stress. The VOCs exposed plants displayed resistance to drought stress by reducing electrolyte leakage and malondialdehyde content and increasing the synthesis of photosynthetic pigments, proline, and phytohormones contents. Maize plants revealed enhanced resistance by showing higher activities of antioxidant defense enzymes both in shoots and roots under drought stress. Activities of antioxidant enzymes were more pronounced in shoots than roots. Gas chromatography and mass spectrophotometric (GC-MS) analysis comparing VOCs produced by the most efficient P. pseudoalcaligenes strain and inefficient strains of Pseudomonas sp. grown in culture media revealed nine compounds that they had in common. However, dimethyl disulfide, 2,3-butanediol, and 2-pentylfuran were detected only in P. pseudoalcaligenes, indicating these compounds are potential candidates for drought stress induction. Further studies are needed to unravel the molecular mechanisms of VOCs-mediated systemic drought tolerance in plants related to each identified VOC.

Co-application of bio-fertilizer and salicylic acid improves growth, photosynthetic pigments and stress tolerance in wheat under drought stress.

Drought stress hampers the growth and productivity of wheat crop worldwide. Thus far, different strategies have been proposed to improve drought tolerance in wheat but the combined application of plant growth-promoting rhizobacteria formulated bio-fertilizer (BF) and salicylic acid (SA) has not been thoroughly explored yet. Therefore, a pot experiment was conducted to observe the effect of SA, BF, and their combination on wheat plants under optimal and drought stress conditions. Seeds priming was done with BF (107 CFU mL-1). After 2 weeks of germination, SA (one mM) was applied as a foliar spray. Drought stress was applied by withholding water supply at three-leaf stage (30 d old plants) for the next 15 d until soil moisture dropped to 10%. Foliar application of SA increased the bacterial population of BF significantly compared to the sole application of BF under irrigated as well as drought stress conditions. Co-application of BF and foliar spray of SA induced drought tolerance in wheat plants by enhancing plant biomass, photosynthetic pigments, relative water content and osmolytes, and activities of the defense-related system. Plants treated with SA and BF together under drought stress had significantly increased leaf water status, Chl a, Chl b, and carotenoids synthesis by 238%, 125%, 167%, and 122%, respectively. Moreover, the co-application of SA and BF showed maximum SOD, POD, APX, and CAT activities by 165%, 85%, 156%, and 169% in the leaves while 153%, 86%, 116% and 200% in roots under drought stress. Similarly, the combined treatment exhibited a pronounced decrease in MDA content by 54% while increased production of proteins and proline by 145% and 149%, respectively. Our results showed that the co-application of SA and BF induced better drought tolerance as compared with the sole application of SA or BF. The results obtained herein suggest that combined application of BF and SA can be applied to the wheat crop to greatly improve drought tolerance in field conditions.

GC-MS analysis, antimicrobial, antioxidant, antilipoxygenase and cytotoxic activities of Jacaranda mimosifolia methanol leaf extracts and fractions.

Jacaranda mimosifolia trees are grown in frost-free regions globally. The aim of this study was to evaluate the methanol crude extract and various fractions of increasing polarity of J. mimosifolia leaves for bioactive metabolites, as well as antimicrobial, antioxidant and anticancer activities. The anti-inflammatory potential of the various fractions of J. mimosifolia leaf extract was studied via the lipoxygenase (LOX) inhibitory assay. Methanol crude extract (ME), derived fractions extracted with chloroform (CF) and ethyl acetate (EAF), and residual aqueous extract (AE) of dried J. mimosifolia leaves were assayed for polyphenolic compounds, their antioxidant, antimicrobial and lipoxygenase (LOX) inhibitory activities, and anticancer properties. Polyphenolic compounds were determined via HPLC while phytochemicals (total phenolics, flavonoids, tannins and ortho-diphenol contents), antioxidant activities (DPPH, hydrogen peroxideperoxide, hydroxyl and superoxide radical anions) and LOX were measured via spectrophotometry. Methanol extracts and various fractions were evaluated for antibacterial activities against Bacillus subtilis, Klebsiella pneumonia, Pseudomonas aeruginosa and Staphylococcus aureus. Antifungal potential of the fractions was tested against three species: Aspergillus flavus, Aspergillus fumigatus and Fusarium oxysporum. The highest values for total phenolic content (TPC), total flavonoid content (TFC), flavonols, tannins and ortho-diphenols were in the ME, followed by CF > EAF > AE. ME also had the highest antioxidant activity with EC50 values 48±1.3, 45±2.4, 42±1.3 and 46±1.3 µg/mL based on the DPPH, hydrogen peroxide, hydroxyl radical and superoxide radical assays, respectively. TPC and TFC showed a significant, strong and positive correlation with the values for each of these antioxidant activities. ME exhibited anti-inflammatory potential based on its LOX inhibitory activity (IC50 = 1.3 µg/mL). ME also had the maximum antibacterial and antifungal potential, followed by EAF > CF > AE. Furthermore, ME showed the strongest cytotoxic effect (EC50 = 10.7 and 17.3 µg/mL) against human hormone-dependent prostate carcinoma (LnCaP) and human lung carcinoma (LU-1) cell lines, respectively. Bioactive compounds present in leaf methanol extracts of J. mimosifolia were identified using gas chromatography-mass spectrometry (GC-MS). Fifteen compounds were identified including phenolic and alcoholic compounds, as well as fatty acids. Our results suggest that J. mimosifolia leaves are a good source of natural products with antioxidant, anti-inflammatory and anti-cancer properties for potential therapeutic, nutraceutical and functional food applications.

Deciphering carbohydrate metabolism during wheat grain development via integrated transcriptome and proteome dynamics.

Grain development of Triticum aestivum is being studied extensively using individual OMICS tools. However, integrated transcriptome and proteome studies are limited mainly due to complexity of genome. Current study focused to unravel the transcriptome-proteome coordination of key mechanisms underlying carbohydrate metabolism during whole wheat grain development. Wheat grains were manually dissected to obtain grain tissues for proteomics and transcriptomics analyses. Differentially expressed proteins and transcripts at the 11 stages of grain development were compared. Computational workflow for integration of two datasets related to carbohydrate metabolism was designed. For CM proteins, output peptide sequences of proteomic analyses (via LC-MS/MS) were used as source to search corresponding transcripts. The transcript that turned out with higher number of peptides was selected as bona fide ribonucleotide sequence for respective protein synthesis. More than 90% of hits resulted in successful identification of respective transcripts. Comparative analysis of protein and transcript expression profiles resulted in overall 32% concordance between these two series of data. However, during grain development correlation of two datasets gradually increased up to ~ tenfold from 152 to 655 °Cd and then dropped down. Proteins involved in carbohydrate metabolism were divided in five categories in accordance with their functions. Enzymes involved in starch and sucrose biosynthesis showed the highest correlations between proteome-transcriptome profiles. High percentage of identification and validation of protein-transcript hits highlighted the power of omics data integration approach over existing gene functional annotation tools. We found that correlation of two datasets is highly influenced by stage of grain development. Further, gene regulatory networks would be helpful in unraveling the mechanisms underlying the complex and significant traits such as grain weight and yield.

Combined seed and foliar pre-treatments with exogenous methyl jasmonate and salicylic acid mitigate drought-induced stress in maize.

Susceptibility of plants to abiotic stresses, including extreme temperatures, salinity and drought, poses an increasing threat to crop productivity worldwide. Here the drought-induced response of maize was modulated by applications of methyl jasmonate (MeJA) and salicylic acid (SA) to seeds prior to sowing and to leaves prior to stress treatment. Pot experiments were conducted to ascertain the effects of exogenous applications of these hormones on maize growth, physiology and biochemistry under drought stress and well-watered (control) conditions. Maize plants were subjected to single as well as combined pre-treatments of MeJA and SA. Drought stress severely affected maize morphology and reduced relative water content, above and below-ground biomass, rates of photosynthesis, and protein content. The prolonged water deficit also led to increased relative membrane permeability and oxidative stress induced by the production of malondialdehyde (from lipid peroxidation), lipoxygenase activity (LOX) and the production of H2O2. The single applications of MeJA and SA were not found to be effective in maize for drought tolerance while the combined pre-treatments with exogenous MeJA+SA mitigated the adverse effects of drought-induced oxidative stress, as reflected in lower levels of lipid peroxidation, LOX activity and H2O2. The same pre-treatment also maintained adequate water status of the plants under drought stress by increasing osmolytes including proline, total carbohydrate content and total soluble sugars. Furthermore, exogenous applications of MeJA+SA approximately doubled the activities of the antioxidant enzymes catalase, peroxidase and superoxide dismutase. Pre-treatment with MeJA alone gave the highest increase in drought-induced production of endogenous abscisic acid (ABA). Pre-treatment with MeJA+SA partially prevented drought-induced oxidative stress by modulating levels of osmolytes and endogenous ABA, as well as the activities of antioxidant enzymes. Taken together, the results show that seed and foliar pre-treatments with exogenous MeJA and/or SA can have positive effects on the responses of maize seedlings to drought.