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Bacillus subtilis and Vermicompost Suppress Damping-off Disease in Psyllium through Nitric Oxide-Dependent Signaling System
Abstract
Fusarium oxysporum is one of pathogens causing the damping-off disease of Plantago psyllium in Iran. A greenhouse experiment was conducted to assess the effect of Bacillus subtilis and vermicompost singly and in combination on control of Fusarium–induced damping-off in psyllium. The results showed that vermicompost or B. subtilis, significantly increased the growth of psyllium seedlings and both were effective biocontrol agents against F. oxysporum. Among treatments at least damping-off incidence was recorded in combination of 50% vermicompost and B. subtilis. Results for the first time exhibited that vermicompost as well as B. subtilis induced systemic resistance through nitric oxide (NO) signaling and their combined application further than their individual treatments induced development of plant defense related enzymes including β-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and the activities of antioxidant enzymes (ascorbate peroxidase, catalase, superoxide dismutase and peroxidase) and also more effectively reduced lipid peroxidation in psyllium leaves. These findings suggested potential of B. subtilis in promoting plant growth as well as inducing systemic resistance in the host plants, was enhanced by vermicompost application.
... Farming is the backbone of Indian economy. Currently, in the world, India is one of the top growers [3]. This sector has seen a steep rise in the recent years. ...
... Enzyme dehydrogenase is involved in oxidative phosphorylation. It is also a measure of the functions of microbes in the soil [3]. Vermicompost prepared from biodegradable wastes has more total microbial count and enzyme activity than traditional compost [11]. ...
... Our findings are in agreement with the studies conducted on suppression of damping off diseases in psyllium by Bacillus subtilis and vermicompost. Amooaghaie et al. (2018) reported that vermicompost and B. subtilis induced systemic resistance through nitric oxide (NO) signaling. Their combined application triggered the accumulation of defense related enzymes including β-1,3-glucanase, PAL, PPO and also effectively reduced lipid peroxidation in psyllium leaves. ...
... However, in other experiments, soil amendment with TG vermicompost, derived from various substrates, demonstrated the inhibition of damping-off disease caused by Phytophthora nicotianae on tomato [23], Rhizoctonia solani on cucumber [24], and F. oxysporum f. sp. lycopersici on Psyllium [35]. ...
Vermicompost is applied as a soil amendment to promote plant growth and yield. It also helps to significantly reduce the incidence of soil-borne diseases. However, its efficiency depends on the type of earthworm from which it is formed. The current study aims to compare the effects of two vermicompost types derived from African nightcrawler (AF) and Tiger worm (TG) as a soil amendment to evaluate its potential for suppressing damping-off disease both in vitro and in vivo. It also aims to determine the effects of both vermicompost types on the growth and yield-related traits of potted Thai vegetable soybean [Glycine max (L.) Merrill] variety “Chiang Mai 84–2” grown under greenhouse conditions when amended to the soil at various application rates (1%, 2%, 3% w/w). AF vermicompost exhibited better suppression of damping-off disease than TG vermicompost in vitro and under greenhouse conditions. AF vermicompost performed significantly greater suppressive efficacy on the mycelial growth of Athelia rolfsii in vitro than TG vermicompost, indicated by 50% and 16% inhibition, respectively. Damping-off incidence on vegetable soybean seedlings grown in soil amended with AF vermicompost was significantly lower (21%) than in soil amended with TG vermicompost (32%) under greenhouse conditions. With an increased application rate of 1% to 2% or 3% for each vermicompost type, plant yields significantly enhanced, with no significant variations among the 2% and 3% rates. Applying vermicompost at 2% w/w through soil amendment was the appropriate rate for promoting the growth and yield of potted vegetable soybeans. The results can be used to guide the application of vermicompost to control soil-borne plant diseases, promote plant growth, and enhance yields, especially in terms of organic crop production. Further research is needed to evaluate its potential for other potted crops and protect against soil-borne diseases.
... Sodium nitroprusside (SNP) serves as a nitric oxide (NO) donor and NO play a fundamental role in plant growth (Khurana et al. 2011), signaling, regulating plant defense or stress responses (Amooaghaie and Korrani 2018), increasing alkaloid accumulation (Xu and Dong 2005), and antioxidant genes (Khan et al. 2017). Mahendran et al. (2021) reported a significant increase in deacylgymnemic acid, gymnemagenin, and gymnemic acid XVII in Gymnema sylvestre cell suspensions exposed to 20 µM SNP treatment. ...
Plant secondary metabolites production is increased in response to both biotic and abiotic elicitors. This study investigates the impact of sodium nitroprusside (SNP) and Trichoderma harzianum on the molecular and biochemical characteristics of Catharanthus roseus cell suspensions. A leaf cell suspension cultured on a medium supplemented with 8 µM 2,4-D and 2 µM BAP was exposed to Trichoderma harzianum (1% v/v) and SNP (150 µM), and subsequently harvested at 12, 24, 48, and 72 h intervals. The highest catalase, ascorbate peroxidase, β (1–3) glucanase, and chitinase activities were recorded 48-hours after elicitation, and coincided with the highest expression levels of G10H (2.5-fold), T16H (1.5-fold), D4H (1.1-fold), DAT (1.9-fold), STR (5-fold), and CrPRX (2-fold) genes. A positive correlation was established between enzyme activities, Terpenoid Indole Alkaloid (TIAs) biosynthesis pathway genes, and the accumulation of vinblastine and vincristine. HPLC analyses showed that the amount of vinblastine and vincristine increased 1.84 and 1.93-fold, respectively, confirming that fungal extracts and SNP elicitors for 48 h significantly increased the vinblastine and vincristine accumulation and related biosynthesis gene in C. roseus plant.
... The treatments, including SiO 2 NPs, significantly enhanced the basil growth traits across the two seasons, with some exceptions relative to the control. Similarly, Si is beneficial for plant growth as it improves the photosynthetic rate and helps fight against various biotic and abiotic stresses [26,27,47]. Therefore, the increased growth potential observed in the aerial parts of basil plants could be attributed to the advantageous impact of SiO 2 NPs on plant metabolism. ...
The reduction in mineral fertilizer usage is crucial to the production of medicinal and aromatic products for safety and health purposes. Presently, nanotechnology and the utilization of natural extracts have been extensively studied due to their significant contribution. Ocimum basilicum is commonly employed for various medicinal and aromatic applications. Therefore, randomized complete block design field experiments containing 10 treatments were conducted during the 2021 and 2022 seasons to investigate the effect of nanoparticles (NPs) of ZnO (1.5 and 2.0 g/L) and SiO2 (100 and 150 mg/L) and date palm pollen extract (DPPE) at 10 and 20 g/L either alone or in combination with the ¾ or ½ NPK recommended dose (RD). The NPK RD was served as a control treatment on basil plant production in each season. The effectiveness of ZnO NPs, SiO2 NPs, and DPPE for the decrease in NPK utilization was evaluated. Meanwhile, the most effective treatment for vegetative traits (except for plant height), essential oil %, and yield was ½ NPK RD + 20 g/L DPPE + 2.0 g/L ZnO NPs. Such a treatment increased the branch number/plant, main stem diameter, relevant chlorophyll content, fresh weight/plant, dry weight/plant, essential oil %, and essential oil yield/plant by 21.00 and 9.94%, 58.70 and 40.00%, 20.69 and 15.83%, 68.83 and 58.28%, 48.70 and 56.16%, 45.71 and 35.53%, and 113.22 and 110.32% over the control in the two seasons, respectively. For total phenol and antioxidant activity, the most effective treatments were the ¾ NPK +1.5 g/L ZnO NPs and ½ NPK +2.0 g/L ZnO NPs, respectively. Simultaneously, essential oil composition (with their compound numbers identified (11–29 for control and ¾ NPK RD + 1.5 g/L ZnO NPs)) and the percentage of total compounds, monoterpene hydrocarbons, sesquiterpene hydrocarbons, and oxygenated hydrocarbons were varied among the used applications. The major observed compounds (>8%) estragole, methyl eugenol, linalool, cineole, and caryophyllene were found in different treatments. Thus, the findings of this study indicate the favorable utilization of ZnO NPs, SiO2 NPs, and DPPE in reducing the application of NPK, which may present a novel strategy and beneficial approach.
... Over the past few decades, it has been demonstrated that silicon (Si) and nitric oxide (NO) can be applied to increase growth and crop production, as well as strengthen plant tolerance against diseases and abiotic stresses (Amooaghaie and Nikzad 2013; Amooaghaie and Roohollahi 2017; Amooaghaie and Korrani 2018;Khator and Shekhawat 2020b;Mohasseli and Sadeghi 2019;Farouk and Omar 2020). Numerous studies showed that both Si (Ashfaque et al. 2017;Wu et al. 2018;Bhat et al. 2019;Vega et al. 2019;El-Beltagi et al. 2020) and NO Khator et al. 2021;Amooaghaie 2019, 2020;Saxena and Shekhawat 2013;Verma et al. 2013) trigger defensive responses and alleviate oxidative damages induced by various heavy metals in many plant species. ...
The individual impact of silicon (Si) and nitric oxide (NO) on secondary metabolism in several plant species has been reported, but their combined effect has never been evaluated yet. Therefore, in this study, single and combined impacts of NO and Si on the biosynthesis of rosmarinic acid (RA) and essential oil (EO) content in leaves of Salvia officinalis were investigated under both non-stress and Cu stress conditions. The results indicated that high Cu concentration decreased biomass and the content of polyphenols, but elevated electrolyte leakage, while lower Cu concentrations, especially 200 μM Cu, increased the content of polyphenols, EO, and antioxidant capacity in leaves of S. officinalis. The foliar application of sodium silicate (1 mM Si) and sodium nitroprusside (200 μM SNP as a NO donor) alone and particularly in combination improved shoot dry biomass, restored chlorophyll and carotenoids, increased EO content, the amounts of flavonoids, and phenolic compounds especially RA, and enhanced antioxidant capacity in the leaves of S. officinalis under both non-stress and Cu stress conditions. Copper treatment increased NO content, upregulated expression of PAL, TAT, and RAS genes, and enhanced phenylalanine ammonia-lyase activity in the leaves, which were responsible for improving the production of phenolic compounds, particularly rosmarinic acid. Foliar spraying with Si and SNP intensified these attributes. All responses were more pronounced when NO and Si were simultaneously applied under Cu stress. These findings suggest that NO and Si synergistically modulate secondary metabolism through upregulation of related gene expression and enzyme activities under both non-stress and Cu stress conditions.
... Significant reduction of nematode infestation in cauliflower was observed after the application of vermicomposts prepared from different combinations of animal/kitchen or agro-waste and biopesticides such as neem oil, extracts of garlic, custard apple (bulb and leaves) (Nath and Singh, 2011). A combination of vermicompost and the antagonistic bacteria B. subtilis suppressed damping-off disease in Plantago psyllium caused by Fusarium oxysporum (Amooaghaie and Korrani, 2018). ...
Agriculture plays a critical role in the growth, development, and sustainability of any nation’s economy. It is the central key in world merchandise. As per the report of the Food and Agriculture Organization (FAO), 60% of the global population depends on agriculture for their survival on Earth. Agricultural practices trace back to ancient times. Since then, many strategies were followed to improve the yield while increasing disease resistance. Disease management strategies varied globally based on cultural and traditional practices. There also occurred evolution in the management strategies in accordance with the socio-economic development. The history traces from crop rotation, use of cow’s urine, application of chemical pesticides such as streptomycin and copper-mancozeb to phage therapy, each method has occupied its prime role in the ascent of agricultural era. The emergence of many phytopathogens has paved the way towards the introduction of many resistant strategies. Genetically engineered plants that are highly disease resistant are developed but are not extremely acceptable because of the monotony. In the continuum, they have also become susceptible to new pathogens. Researchers now are on the highway looking for a promising and more potential source for disease management. This article summarizes various disease management strategies practiced by farmers and the application of bacterial viruses in controlling plant pathogenic bacteria. It also highlights other possible methods for plant disease control in the near future for sustainable organic agricultural practices.
... Nitric oxide also is an endogenous signal molecule involved in a variety of developmental processes and the plant adaptive responses against environmental stresses (Sahay and Gupta 2017;Amooaghaie and Roohollahi 2017;Amooaghaie and Mardani Korrani 2018). Many studies have shown that cadmium stress is increasing NO levels in various plant species and application of NO donors, such as sodium nitruprosside (SNP), alleviating Cd toxicity via activation of the antioxidant system (see Arasimowicz-Jelonek et al. 2011). ...
In this study, a pot experiment was performed to evaluate the effects of foliar spray with sodium nitroprusside (200 μM SNP) and melatonin (100 μM) singly and in combination on tolerance and accumulation of cadmium (Cd) in Catharanthus roseus (L.) G. Don plants exposed to different levels of cadmium (0, 50, 100, and 200 mg Cd kg−1 soil). The results showed that 50 mg kg−1 Cd had no significant effect on the fresh and dry weight of roots and shoots and content of chlorophyll (Chl) a and b, but the higher levels of Cd (100 and 200 mg kg−1) significantly reduced these attributes and induced an increase in the level of leaf electrolyte leakage and disrupted nutrient homeostasis. The activities of catalase (CAT) and peroxidase (POD) in leaves were increased under lower Cd concentrations (50 and 100 mg kg−1) but decreased under 200 mg kg−1 Cd. However, foliar spray with melatonin and/or SNP increased shoot biomass and the content of Chl a and b, augmented activities of POD and CAT, lowered electrolyte leakage (EL), and improved essential cations homeostasis in leaves. Cadmium content in shoots of C. roseus was less than roots and TF (transfer factor) was < 1. Interestingly, foliar spray with SNP and/or melatonin increased Cd accumulation and bioconcentration factor (BCF) in both roots and shoots and elevated the Cd transport from roots to shoot, as TF values increased in these treatments. The co-application of melatonin and SNP further than their separate usage augmented Cd tolerance through increasing activities of antioxidant enzymes and regulating mineral homeostasis in C. roseus. Furthermore, co-treatment of SNP and melatonin increased Cd phytoremediation efficiency in C. roseus through increasing biomass and elevating uptake and translocation of Cd from root to shoot.
... Significant reduction of nematode infestation in cauliflower was observed after the application of vermicomposts prepared from different combinations of animal/kitchen or agro-waste and biopesticides such as neem oil, extracts of garlic, custard apple (bulb and leaves) (Nath and Singh, 2011). A combination of vermicompost and the antagonistic bacteria B. subtilis suppressed damping-off disease in Plantago psyllium caused by Fusarium oxysporum (Amooaghaie and Korrani, 2018). ...
Agriculture plays a critical role in the growth, development, and sustainability of any nation's economy. It is the central key in world merchandise. As per the report of the Food and Agriculture Organization (FAO), 60% of the global population depends on agriculture for their survival on Earth. Agricultural practices trace back to ancient times. Since then, many strategies were followed to improve the yield while increasing disease resistance. Disease management strategies varied globally based on cultural and traditional practices. There also occurred evolution in the management strategies in accordance with the socio-economic development. The history traces from crop rotation, use of cow's urine, application of chemical pesticides such as streptomycin and copper-mancozeb to phage therapy, each method has occupied its prime role in the ascent of agricultural era. The emergence of many phytopathogens has paved the way towards the introduction of many resistant strategies. Genetically engineered plants that are highly disease resistant are developed but are not extremely acceptable because of the monotony. In the continuum, they have also become susceptible to new pathogens. Researchers now are on the highway looking for a promising and more potential source for disease management. This article summarizes various disease management strategies practiced by farmers and the application of bacterial viruses in controlling plant pathogenic bacteria. It also highlights other possible methods for plant disease control in the near future for sustainable organic agricultural practices.
... Nitric oxide is a labile gaseous messenger molecule that not only orchestrates a wide range of physiological processes in plants (Domingos et al. 2015), but also promotes plant defence responses against pathogens (Amooaghaie and Mardani Korrani 2018) and various abiotic stresses such as cold (Amooaghaie and Nikzad 2013), alkaline stress (Amooaghaie and Roohollahi 2017), nanoparticle toxicity , and the toxicity of heavy metals (Alemayehu et al. 2015;Wang et al. 2016;Sun et al. 2018). reported that after short-term exposure to Cd (3 h), NO enhanced the expression of genes related to signaling pathways, including transcription factors of DOF1, MYBZ2, and MAPKK2. ...
Nitric oxide (NO) and melatonin are two biostimulant molecules in plants that not only modulate the growth and development of plants but also confer enhanced tolerance to abiotic stresses. Therefore, in this study, the interactive effects of melatonin and nitric oxide (NO) on seedlings of Catharanthus roseus (L.) G. Don was evaluated under both control and conditions of stress due to Cd. Our results show that both melatonin and sodium nitroprusside (SNP, as an NO donor) significantly improved seedling growth, which was associated with the enhanced concentration of photosynthetic pigments in both the control plants and under Cd-stress conditions. Impacts of both melatonin and SNP were more pronounced in the Cd-stressed plants than control seedlings. The Cd stress increased H2O2 and lipid peroxidation levels in roots. Melatonin, as well as SNP, increased endogenous NO concentration in roots. Both melatonin and SNP enhanced the concentration of proline and the activities of antioxidant enzymes (SOD, POD, APX, CAT) and lowered H2O2 and lipid peroxidation levels in roots of C. roseus plants under Cd stress. These melatonin-induced responses in the roots were suppressed by 4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO; a specific scavenger of NO), but inhibition of melatonin biosynthesis by p–chlorophenylalanine, could not reverse the protective effects conferred by NO. These outcomes suggest that NO, as a downstream signaling molecule, is implicated in the melatonin-promoted antioxidant responses in roots of C. roseus plants.
The effects of autumn sowing and chemical, organic, and biological fertilizer sources were explored on yield components and physiological traits of dragon’s head (Lallemantia iberica Fisch. & C.A.Mey). The study was conducted as a factorial experiment based on a randomized complete block design with three replications in a field experiment in the 2017-2018 crop year. The fertilizer treatments included organic fertilizers (vermicompost, manure, and humic acid), biofertilizer (Thiobacillus mixed with sulfur), chemical fertilizer (macro NPK), and control (no fertilizer). The studied traits included seed yield per ha, harvest index, biological yield per ha, chlorophyll a, chlorophyll b, carotenoid, proline, and dissolved carbohydrate. The results of the comparison of the means revealed that the winter sowing outperformed the spring sowing evidently and increased traits like seed yield per ha, biological yield per ha, and harvest index significantly. The fertilization of the plants in both sowing seasons, especially in the winter sowing, increased seed yield per ha, biological yield per ha, and harvest index so that the vermicompost-fertilized winter-sown plants produced the highest seed yield per ha (0.91 g), whereas the application of manure was related to the highest harvest index in the winter sowing (27.9%). The highest biological yield (8797 kg ha-1) was related to the treatment of Thiobacillus of the winter-sown plants. Proline content was higher in the spring sowing plants, and the control treatment in the spring sowing had the highest proline content (0.120 mg g-1). Concerning dissolved carbohydrates, the spring sowing and the unfertilized plants had the highest content (20.3 mg g-1). On the other hand, chlorophyll a, chlorophyll b, and carotenoid were higher in the treatments of Thiobacillus and vermicompost, which resulted in achieving higher yields due to the increase in photosynthesis rate. According to the results, the winter sowing of the dragon’s head in the Azerbaijan region of Iran and the use of Thiobacillus and vermicompost could be recommended for obtaining plants with optimum quality parameters.
Arsenic (As) is a hazardous metalloid, and mycorrhizal inoculation and vermicompost amendment can influence As bioremediation. However, the studies concerning the sole and joint effects of arbuscular mycorrhizal fungi (AMF) and vermicompost on the phytoremediation efficacy are limited. In the present study at first, the impact of various levels of vermicompost (0, 2, 4, and 8% w/w) was investigated on As mobility in soil and safflower (Carthamus tinctorius L.) plants grown in soils of spiked with 0, 40, and 80 mg kg−1 As. Results revealed that with increasing dose of vermicompost, bioavailable As in soil decreased which resulted in a lower bioaccumulation factor and translocation factor (TF) and led to a significant increase of tolerance index (TI) and total chlorophyll content in plants. The highest effect on TI and total As accumulation per plant was obtained in the dosage of 8% vermicompost. Therefore, in the second experiment, the sole and joint effects of 8% vermicompost and inoculation with Rhizophagus intraradices were assessed on the tolerance and accumulation of As in safflower. The addition of vermicompost aggravated mycorrhizal colonization but did not significantly influence mycorrhizal dependency under As stress. The joint effects of AMF and vermicompost improved the dry weight of roots and shoots, increased P concentration and P:As ratio in shoots, reduced malondialdehyde content, and moderated ascorbate peroxidase activity in leaves of As-stressed plants. Interestingly, co-application of AMF and vermicompost more than their sole usage decreased As concentration in shoots and TF and more strongly increased total As accumulation per plant. These findings suggest that mycorrhizal inoculation and vermicompost have a synergistic effect on As tolerance and phytostabilization efficacy of safflower plants, and their combined application may be a new option to remediate As-contaminated soils.
Biotic and abiotic elicitors induce the production of plant secondary metabolites. In this study the effects of Trichoderma harzianum and sodium nitroprusside (SNP) as a biotic and abiotic elicitor on biochemical and molecular features of Catharanthus roseous cell suspension were investigated. Leaf explant and medium amended with concentration of 8 µM 2,4-D and 2 µM BAP were used for obtain cell suspension. Cell suspension exposed to T. harzianum . (%1 v/v) and SNP (150 µM) and after 12, 24, 48 and 72 hours harvested. The highest activity of catalase, ascorbate peroxidase, β (1–3) glucanase and chitinase were found 48 hours after application of treatments. Also, the highest level of G10H (2.5-fold), T16H (1.5-fold), D4H (1.1-fold), DAT (1.9-fold), STR (5-fold) and CrPRX (2-fold) were observed 48-hours after elicitor application. A positive correlation was observed between enzymes activities, TIAs biosynthesis pathway genes and vinblastine and vincristine accumulation. These results confirmed that fungus and SNP elicitors in C. roseous led to increase secondary metabolites production and gene expression related to biosynthesis of vinblastine and vincristine pathway 1.84 and 1.93-fold, 48-hours after elicitor application, respectively. All these results suggest that fungus and SNP elicitors after 48-houres exposure, effectively improve the pharmaceutical value of C. roseous.
In this study, the role of nitric oxide (NO) burst in modulating Si-induced defensive responses in leaves and roots of Salvia officinalis under copper (Cu) stress were investigated. The result showed that 400 μM Cu markedly reduced shoot dry weight, but increased electrolyte leakage (EL) in leaves and both Si and sodium nitroprusside (SNP as the NO donor) improved these attributes in a dose-dependent manner. Interestingly, Cu toxicity systemically boosted a NO burst in both roots and shoots and applying Si and SNP markedly intensified it. The application of Si and SNP alone as well as their combination improved growth parameters and systemically alleviated Cu-induced lipid peroxidation and H2O2 accumulation through lowering Cu accumulation, increasing proline content, enhancing the activities of catalase (CAT) and superoxide dismutase (SOD) in both roots and leaves and up-regulating expression of SOD gene in leaves of S. officinalis. NO generation was substantially arrested and the responses induced by Si were significantly suppressed by pretreatment with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy l-3-oxide (cPTIO) as a NO scavenger, Nx-Nitro- L-arginine methyl ester hydrochloride (L-NAME) as a nitric oxide synthase inhibitor, and tungstate as a nitrate reductase inhibitor. These novel results indicate that Si can induce Cu tolerance through triggering NO generation which systemically modulates defensive reactions in both roots and leaves of Salvia officinalis.
In this study 50 mg/l Ni stress reduced plant growth, induced oxidative stress, increased proline accumulation and H2S content in roots and leaves of zucchini. Indeed, Ni toxicity up-regulated calmodulin (CaM) gene expression in leaves. Root pretreatment with calcium and NaHS (as hydrogen sulfide donor) singly or in combination reduced SOD activity but enhanced activities of CAT, POD and lowered accumulation of proline and Ni element not only in root, but also in untreated leaves, suggesting a systemic mitigating effect of Ca²⁺/H2S pretreatment on Ni-evoked oxidative damage in both roots and leaves. Importantly, Ni-induced H2S accumulation was markedly strengthened by application of exogenous Ca²⁺ and this effect was weakened by addition of H2S scavenger, hypotaurine (HT), in roots and leaves, suggesting H2S acts downstream of Ca²⁺. On the other hand, root pretreatment with NaHS, amplified Ni-induced CaM gene expression in leaves and mediated antioxidant defense in both roots and leaves and addition of ethylene glycol tetra acetic acid (EGTA) as a Ca²⁺ chelator, verapamil (VPL) as a plasma membrane channel blocker, and trifluoperazine(TFP) as a calmodulin (CaM) antagonist, reversed these impacts. These results suggested that root pretreatment with H2S could induce systemic Ni tolerance not only in the site of application, but also in untreated distant parts in Ni-stressed zucchini seedlings and the acquisition of this Ni tolerance requires the entry of extracellular Ca²⁺ into cells across the plasma membrane and the mediation of intracellular CaM. Taken together, it seems that Ca²⁺/CaM complex functions both upstream and downstream of H2S and crosstalk of Ca²⁺ and H2S is essential for inducing systemic acquired acclimation in Ni-stressed zucchini seedlings.
Nitric oxide (NO) is a gaseous diatomic molecule with a wide variety of physiological and pathological implications in plants. Presence of unpaired electron in its molecular orbital makes it highly reactive; it can react directly with metal complexes, radicals, DNA, proteins, lipids and other biomolecules. Nitric oxide (NO) and reactive oxygen species (ROS) are known to play essential role in a number of important plant physiological processes. Tis manuscript reviews the role of NO on these processes during various biotic and abiotic stresses.
Systemic acquired resistance (SAR) is a form of broad-spectrum disease resistance that is induced in response to primary infection and that protects uninfected portions of the plant against secondary infections by related or unrelated pathogens. SAR is associated with an increase in chemical signals that operate in a collective manner to confer protection against secondary infections. These include, the phytohormone salicylic acid (SA), glycerol-3-phosphate (G3P), azelaic acid (AzA) and more recently identified signals nitric oxide (NO) and reactive oxygen species (ROS). NO, ROS, AzA and G3P function in the same branch of the SAR pathway, and in parallel to the SA-regulated branch. NO and ROS function upstream of AzA/G3P and different reactive oxygen species functions in an additive manner to mediate chemical cleavage of the C9 double bond on C18 unsaturated fatty acids to generate AzA. The parallel and additive functioning of various chemical signals provides important new insights in the overlapping pathways leading to SAR.
The review considers the mechanisms underlying the ability of plant growth�promoting bacteria (PGPB) to enhance plant tolerance to biotic and abiotic stresses. The improved tolerance is determined by a number of microbiological factors; such as supply of mineral nutrients; production of hormones and signaling metabolites; syntheses of antibiotics, biosurfactants, siderophores, chitinases, glucanases, proteases and lipases; and induction of systemic resistance to pathogens and herbivores. Possible mechanisms of interac�tions in the plant–PGPB–pathogen (pest) system are considered. The PGPB may exert their role either directly, through elimination of harmful organisms by antimicrobial substances and hydrolytic enzymes, or indirectly, through activation of host defense systems and the induction of systemic resistance. New approaches to the design of broad�spectrum biopesticides on the basis of PGPB are considered.
Bacillus subtilis IAGS174 has been previously shown to induce systemic resistance in tomato plants against Fusarium wilt disease. In the present investigation, the resistance-inducing determinant was isolated from cell-free culture filtrates (CFCF) of this bacterium. For this purpose, CFCF was extracted by a series of organic solvents, and the fraction that showed induced systemic resistance (ISR) activity was further partitioned into sub-fractions by column chromatography by using a stepwise elution method. Gas chromatography/mass spectrometry analysis identified four compounds in the ISR-active sub-fraction viz. eugenol, 3-methoxy butyl acetate, pentachloroaniline and phthalic acid methyl ester (PAME). Subsequent bioassays proved that PAME is the potential ISR determinant that significantly ameliorated Fusarium wilt disease of tomato at concentrations of 0.01 and 0.1 mM. Furthermore, compared to the respective controls, tomato plants treated with PAME showed increased activities of defense-related enzymes such as phenylalanine ammonia-lyase, polyphenol oxidase, and peroxidase. Our research indicates that B. subtilis IAGS174 has great potential for use as a biological control agent, and PAME is the ISR determinant secreted by this bacterium into the rhizosphere. This determinant can effectively trigger defense responses in tomato plants.
Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum J. H. Owen, results in considerable yield losses for cucumber plants. A bio-organic fertilizer (BIO), which was a combination of manure composts with antag-onistic microorganisms, and an organic fertilizer (OF) were evaluated for their efficiencies in controlling Fusarium wilt. Application of the BIO suppressed the disease incidence by 83% and reduced yield losses threefold compared with the application of OF. Analysis of microbial communities in rhizosphere soils by high-throughput pyrosequencing showed that more complex community structures were pres-ent in BIO than in OF treated soils. The dominant taxonomic phyla found in both samples were Proteobacteria, Firmi-cutes, Actinobacteria and Acidobacteria among bacteria and Ascomycota among fungi. Abundance of beneficial bacteria or fungi, such as Trichoderma, Hypoxylon, Tritir-achium, Paenibacillus, Bacillus, Haliangium and Strepto-myces, increased compared to the OF treatment, whereas the soil-borne pathogen, Fusarium, was markedly decreased. Overall, the results of this study demonstrate that the appli-cation of the BIO was a useful and effective approach to suppress Fusarium wilt and that the high-throughput 454 pyrosequencing was a suitable method for the characteriza-tion of microbial communities of rhizosphere soil of cucumber.
Collar rot of chickpea (Cicer arietinum) is caused by the soil-borne pathogen Sclerotium rolfsii and management of this ubiquitous pathogen is not possible through a single approach. An integrated approach was adopted by using vermicompost and an antagonistic strain of Pseudomonas syringae (PUR46) possessing plant growth-promoting characteristics. Treatments with vermicompost (10%, 25%, and 50% v/v) and PUR46 alone and in combination reduced seedling mortality in chickpea under glasshouse conditions. The combined effect of 25% vermicompost substitution along with seed bacterization with PUR46 was the most effective treatment, which not only increased the availability and uptake of minerals like P, Mn, and Fe in chickpea seedlings, resulting in an increase in plant growth, but also reduced plant mortality. These effects are correlated with improvement in soil physical conditions and enhanced nutritional factors due to vermicompost substitution as well as plant growth promotion and the antagonistic activity of PUR46 against the pathogen. Dual cultures of PUR46 with the S. rolfsii isolate revealed a high degree of antagonism by PUR46 against the pathogen. Performance of PUR46 was enhanced in the presence of 25% vermicompost compared with its application alone and therefore this combination may be a useful tool to manage S. rolfsii under field conditions.
The study was aimed to search out the probable molecule behind the activation of a broad spectrum resistance during Pseudomonas aeruginosa WS-1 mediated induced systemic resistance (ISR) in Capsicum annuum where plants were challenged inoculated with its pathogen Colletotrichum capsici 24 h after induction of ISR. On the fourth day after pathogen inoculation a significant increase of pathogenesis-related (PR) proteins, other defence enzymes and phenolics as well as a two-fold increase of nitric oxide (NO) a potent defence signalling molecule were observed. Treatment of the host with NO donor also induced the same defence molecule in a similar manner. Results suggest the possible signalling role of NO in ISR during crosstalk between ISR inducing agent and pathogen within the host system.
Fusarium wilt of watermelon commonly occurs in locations where the crop has been grown for many seasons. Its occurrence results
in a severely decreased watermelon crop. The goal of this study was to assess the capability of a new product (bio-organic
fertilizer) to control the wilt in Fusarium-infested soil. Pot experiments were conducted under growth chamber and greenhouse
conditions. The results showed that the fertilizer controlled the wilt disease. Compared with control pots, the incidence
rates of Fusarium wilt at 27 and 63days following treatment of the plants with the bio-organic fertilizer at a rate of 0.5%
(organic fertilizer+antagonistic microorganisms, including 3×109CFUg−1
Paenibacillus polymyxa and 5×107CFUg−1
Trichoderma harzianum) were reduced by 84.9 and 75.0%, respectively, in both the growth chamber and greenhouse settings. The activities of antioxidases
(catalase, superoxide dismutase and peroxidase) in watermelon leaves increased by 38.9, 150 and 250%, respectively. In the
roots, stems and leaves, the activity of β-1,3-glucanase (pathogenesis-related proteins) increased by 80, 1140 and 100% and
that of chitinase increased by 240, 80, and 20%, respectively, while the contents of malondialdehyde fell by 56.8, 42.1 and
45.9%, respectively. These results indicate that this new fertilizer formula is capable of protecting watermelon from Fusarium oxysporum f.sp. niveum. The elevated levels of defense-related enzymes are consistent with the induction and enhancement of systemic acquired resistance
of plant.
Low molecular weight phenolic compounds have been identified in fresh leaves and in soils in which leaves of five varieties of Capsicum annuum L. were decomposing. Six phenolic compounds were tested in laboratory bioassays for their allelopathic effects on germination and seedling growth of six weeds. Ferulic acid, gallic acid, p-coumaric acid, p-hydroxybenzoic acid, vanillic acid, and p-vanillin were bioassayed in concentrations of 10, 1, 0.1, and 0.01 mM. Equimolar mixtures containing all these phenolics were prepared at the final total concentration of 10, 1, 0.1, and 0.01 mM to test for possible interactive effects. Chenopodium album L., Plantago lanceolata L., Amaranthus retroflexus L., Solanum nigrum L., Cirsium sp. and Rumex crispus L. were the selected target weeds. The highest concentration of the compounds inhibited the germination of all these weeds, but lower concentrations had no effect or were stimulatory. However, effects varied with the weed species, the concentration of the compound tested and the compound itself. In assays with the mixture of phenolics we found evidence of some additive effects.
Vermicompost preparations are increasingly used in agricultural practice. There is a possibility, that crop plants are sensitive
to negative effect of vermicompost at early stages of development. The aim of the present study was to test the effects of
vermicompost on seed germination and seedling growth of different vegetable crop species. Vermicompost substitution inhibited
seed germination and seedling growth with almost linear decrease of growth with increasing concentration of vermicopost in
the substrate. However, both leaf chlorophyll content and photochemical activity of photosynthesis increased in all crop species
with the exception of pea seedlings. Vermicompost extract as a watering solution showed positive effect on growth of bean
and pea seedlings. Germination response of vermicompost extract-imbibed seeds was clearly crop species-dependent. Hypocotyl
growth was stimulated by low and moderate vermicompost extract concentrations. Radicle growth was more sensitive to negative
effect of vermicompost extract. It is reported that both solid vermicompost and vermicompost extract contain number of active
substances of both phenolic and humic nature, each with own dose- and genotype-dependent effect of seed germination and early
stages of seedling development. Findings of this study suggests that vermicompost must be used cautiously for practical purposes
of plant propagation.
KeywordsCrop plants–Chlorophyll–Chlorophyll a fluorescence–Germination–Growth–Physiological status–Vermicast
Bacterial isolates having antifungal and good plant growth-promoting attributes were isolated from chir-pine (Pinus roxburghii) rhizosphere. An isolate, Bacillus subtilis BN1 exhibited strong antagonistic activity against Macrophomina phaseolina, and other phytopathogens including Fusarium oxysporum and Rhizoctonia solani. It was characterized and selected for the present studies. BN1 resulted in vacuolation, hyphal squeezing, swelling, abnormal
branching and lysis of mycelia. The cell-free culture filtrate of BN1 inhibited the growth of M. phaseolina. Pot trial study resulted in statistically significant increase in seedling biomass besides reduction in root rot symptoms
in chir-pine seedlings. BN1 treatment resulted in 43.6% and 93.54% increases in root and shoot dry weights respectively, as
compared to control. Also, 80–85% seed viability was recorded in treatments receiving BN1 either alone or in the presence
of M. phaseolina, compared to 54.5% with M. phaseolina. Bioinoculant formulation study suggested that maximum viability of bacteria was in a sawdust-based carrier. B. subtilis BN1 produced lytic enzymes, chitinase and β-1,3-glucanase, which are known to cause hyphal degradation and digestion of the
cell wall component of M. phaseolina. In the presence of M. phaseolina, population of B1 was 1.5×104c.f.u.g−1 root after one month, which increased to 4.5×104c.f.u.g−1 root in three months. Positive root colonization capability of B. subtilis BN1 proved it as a potent biocontrol agent.
Inducible defense-related proteins have been described in many plant species upon infection with oomycetes, fungi, bacteria, or viruses, or insect attack. Several types of proteins are common and have been classified into 17 families of pathogenesis-related proteins (PRs). Others have so far been found to occur more specifically in some plant species. Most PRs and related proteins are induced through the action of the signaling compounds salicylic acid, jasmonic acid, or ethylene, and possess antimicrobial activities in vitro through hydrolytic activities on cell walls, contact toxicity, and perhaps an involvement in defense signaling. However, when expressed in transgenic plants, they reduce only a limited number of diseases, depending on the nature of the protein, plant species, and pathogen involved. As exemplified by the PR-1 proteins in Arabidopsis and rice, many homologous proteins belonging to the same family are regulated developmentally and may serve different functions in specific organs or tissues. Several defense-related proteins are induced during senescence, wounding or cold stress, and some possess antifreeze activity. Many defense-related proteins are present constitutively in floral tissues and a substantial number of PR-like proteins in pollen, fruits, and vegetables can provoke allergy in humans. The evolutionary conservation of similar defense-related proteins in monocots and dicots, but also their divergent occurrence in other conditions, suggest that these proteins serve essential functions in plant life, whether in defense or not.
Hypercholesterolemia is a major risk factor for coronary heart disease and nutrition management is the initial therapeutic approach.
This multicenter study evaluated the long-term effectiveness of psyllium husk fiber as an adjunct to diet in the treatment of persons with primary hypercholesterolemia.
Men and women with hypercholesterolemia were recruited. After following an American Heart Association Step I diet for 8 wk (dietary adaptation phase), eligible subjects with serum LDL-cholesterol concentrations between 3.36 and 4.91 mmol/L were randomly assigned to receive either 5.1 g psyllium or a cellulose placebo twice daily for 26 wk while continuing diet therapy.
Serum total and LDL-cholesterol concentrations were 4.7% and 6.7% lower in the psyllium group than in the placebo group after 24-26 wk (P < 0.001). Other outcome measures did not differ significantly between groups.
Treatment with 5.1 g psyllium twice daily produces significant net reductions in serum total and LDL-cholesterol concentrations in men and women with primary hypercholesterolemia. Psyllium therapy is an effective adjunct to diet therapy and may provide an alternative to drug therapy for some patients.
H2S and NO are two important gasotransmitters that modulate stress responses in plants. There are the contradictory data on crosstalk between NO and H2S in the studies. Hence, in the present study, the role of interplay between NO and H2S was assessed on the Pb tolerance of Sesamum indicum using pharmacological and biochemical approaches. Results revealed that Pb stress reduced the plant growth and the content of photosynthetic pigments and Fv/Fm ratio, increased the lipid peroxidation and the H2O2 content, elevated the endogenous contents of nitric oxide (NO), H2S and enhanced the activities of antioxidant enzymes (except APX). Additionally, concentrations of most mineral ions (K, P, Mg, Fe, Mn and Zn) in both shoots and roots decreased. Pb accumulation in roots was more than it in shoots. Both sodium hydrosulfide (NaHS as a donor of H2S) and sodium nitroprusside (SNP as an NO donor) improved the plant growth, the chlorophyll and carotenoid contents and PSII efficiency, reduced oxidative damage, increased the activities of antioxidant enzymes and reduced the proline content in Pb-stressed plants. Furthermore, both NaHS and SNP significantly restricted the uptake and translocation of Pb, thereby minimizing antagonistic effects of Pb on essential mineral contents in sesame plants. NaHS increased the NO generation and many NaHS-induced responses were completely reversed by cPTIO, as the specific NO scavenger. Applying SNP also enhanced H2S release levels in roots of Pb-stressed plants and only some NO-driven effects were partially weakened by hypotuarine (HT), as the scavenger of H2S.These findings proposed for the first time that two-sided interplay between H2S and NO might confer an increased tolerance to Pb stress via activating the antioxidant systems, reducing the uptake and translocation of Pb, and harmonizing the balance of mineral nutrient.
In this study, the effect of various vermicompost substitutions (0, 25, 50, and 75%) was investigated on germination, growth and development, photosynthetic parameters, the essential oil content, and disease resistance of Thymus vulgaris. Results showed that 25% vermicompost substitution promoted the best seedling emergence indices, whereas maximum length, fresh and dry weight of aerial parts and root, chlorophyll and carotenoid contents, photosynthetic efficiency, and the highest essential oil content were observed in 50% vermicompost substitution. Vermicompost was an effective biocontrol agent against Fusarium oxysporum and Phytophthora infestans. Suppression of pathogens by vermicompost was enhanced progressively with increasing rates of substitution of vermicompost, and the highest suppression obtained in 75% vermicompost substitution. The disease protection correlated to development of activities of defense-related enzymes including β-1,3-glucanase, phenylalanine ammonialyase, polyphenol oxidase and peroxidase, and total phenolics content. These results suggest the potential of vermicompost in promoting of plant yield as well as inducing systemic resistance in Thymus vulgaris.
In our study, one-month-old Melissa officinalis plants were subjected to Fe-deficiency treatments, such as 10 μM Fe (as direct iron deficiency, DD), and 30 μM Fe + 10 mM NaHCO3 + 0.5 g l−1 CaCO3 (as indirect iron deficiency, ID), and 30 μM Fe (as control) for 14 days. Both Fe-deficiency types decreased plant growth, photosynthetic pigment contents, an active Fe content in roots and leaves, root Fe(III)-reducing capacity, Fe-use efficiency, maximal quantum yield of PSII photochemistry, a ratio of variable to basic fluorescence, and activities of antioxidant enzymes, while Fe deficiency increased lipid peroxidation and a H2O2 content in leaves. These effects were more pronounced in plants exposed to ID with bicarbonate than those of DD plants. We showed that sodium nitroprusside (SNP), as NO donor, could ameliorate the adverse effects of bicarbonate on above traits. The methylene blue, as NO blocker, reversed the protective effects conferred by SNP in the ID-treated plants as well as DD plants. These findings suggests that NO protects photosynthesis and growth of ID-treated plants as well as DD plants by contribution in availability and/or delivery of metabolically active iron or by changing activities of reactive oxygen species-scavenging enzymes.
Vermicompost (VC) is a nutritionally rich natural organic fertilizer, which releases nutrients relatively slowly in the soil. It improves quality of the plants along with physical and biological properties of soil, i. e., soil aeration, water-holding capacity and ecological balance of microbial soil biota. Aqueous extracts of vermicompost (AVC) inhibited spore germination of several fungi. They also affected the development of powdery mildews on balsam (Impatiens balsamina) and pea (Pisum sativum) caused by Erysiphe cichoracearum and Erysiphe pisi, respectively, in the field at very low concentrations (0.1-0.5 %). Soil amendment with VC (1-5%) induced synthesis of phenolic acids in pea. Maximum phenolic acids were detected in pea plants treated with 4% VC followed by 3% as compared to control. The induction of phenolic acids in plants was correlated with the degree of resistance in treated as compared to non-treated (control) pea plants. The growth of plants grown in VC-amended soil was much better than the growth of plants raised in non-amended soil.
Agrochemicals which ushered in the ‘green revolution’ in the 1950-60’s, boosted food productivity, but at the cost of environment and society. It increased food production but also destroyed the ‘physical, chemical and the biological properties’ of soil over the years of use. It killed the beneficial soil organisms and also impaired the power of ‘biological resistance’ in crops making them more susceptible to pests and diseases. No farmland of world is free of toxic pesticides today. Over the years it has worked like a ‘slow poison’ for the soil and society. According to UNEP and WHO nearly 3 million people suffer from ‘acute pesticide poisoning’ and some 10 to 20 thousand people die every year from it in both the developed and the developing countries. Organic farming by earthworms (Sir Charles Darwin’s ‘friends of farmers’) can provide a sustainable and also highly economical solution to the various problems created by the destructive agrochemicals in farm production. Earthworms vermicompost are scientifically proving to be an ‘extraordinary powerful growth promoters and protectors’ for crops (5-7 times over other bulky organic fertilizers and 20-40 % higher over chemical fertilizers). They are rich in NKP, micronutrients, beneficial soil microbes like ‘nitrogen-fixing’ and ‘phosphate solubilizing’ bacteria, ‘mycorrhizal fungi’, humus and growth hormones – auxins, gibberlins and cytokinins. It has very high ‘porosity’, ‘aeration’, ‘drainage’ and ‘water
Rhizoctonia solani damping-off and root rot diseases are frequent in impatiens crops in Buenos Aires. Their control is based in fungicide use. In a sustainable nursery production, beneficial microorganisms that develop in organic amendments may suppress diseases and promote plant growth. The aim of this work was to evaluate the effect of different proportions of vermicompost on the growth and health of patience-plant (Impatiens wallerana). The experiment was carried out in a polyethylene greenhouse. Treatments were defined as follows: infested substrate, substrate, sterilized substrate, vermicompost, and vermicompost mixed with infested substrate at 75, 50 and 25% by volume. Seeds of I. wallerana were sown in plugs containing the different substrates. Percentage of healthy seedlings was evaluated since emergence, and growth parameters were recorded at day 51. The concentration of pathogen in the different treatments was estimated at the beginning and end of the experiment. Treatments with 100-75% of vermicompost showed important increases of leaf area, plant height and fresh and dry weight of aerial and subterranean organs. Root length was not modified by compost addition. Vermicompost at 75% provided slight control of damping-off caused by R. solani.
Vermicomposting is a process in which earthworms are used to convert organic materials into humus-like material known as vermicompost. A number of researchers throughout the world found that the nutrient profile in the vermicompost is generally higher than traditional compost. In fact, vermicompost can enhance soil fertility physically, chemically and biologically. Physically, vermicompost-treated soil has better aeration, porosity, bulk density and water retention. The chemical properties such as pH, electrical conductivity and organic matter content are also improved for better crop yield. Nevertheless, the enhanced plant growth could not be satisfactorily explained by improvements in the nutrient content of the soil, which means that other plant growth influencing materials are available in the vermicomposts. Although vermicomposts have been shown to improve plant growth significantly, the application of vermicomposts at high concentrations could impede the growth due to the high concentrations of soluble salts available in the vermicomposts. Therefore, vermicomposts should be applied at moderate concentrations in order to obtain maximum plant yield. This review paper discussed in detail the effects of vermicompost on soil fertility physically, chemically and biologically. Future prospects and economy on the use of organic fertilizers in agriculture sector were also examined.
Muskmelon (Cucumis melo L.) wilt caused by Fusarium oxysporum f. sp. melonis leads to severe economic losses. A bio-organic fertilizer (BIO) fortified with an antagonistic strain of Bacillus subtilis Y-IVI was used to control this disease. Pot experiments were carried out to investigate the efficacy and to elucidate biocontrol mechanisms for the disease. BIO significantly reduced the disease incidence. Population of F. oxysporum in plant shoots of the BIO treatment were about 1000-fold lower than the control. Population of Y-IVI remained high in muskmelon rhizosphere of the BIO treatment during the experiment. Concentration of antifungal lipopeptides, iturin A, in the BIO treatment was significantly higher than other treatments. Ten days after transplantation, the salicylic acid content in BIO-treated plant leaves was significantly higher than control. In conclusion, BIO effectively controlled muskmelon wilt, possibly because the antagonistic microbes effectively colonize the plant rhizosphere and shoots to preclude pathogen invasion. Furthermore, Y-IVI produces antifungal lipopeptides in the rhizosphere.
Four Pseudomonad strains were used with or without vermicompost amendment to see their performance on potato plant growth and yield along with suppression of common scab of potato. Two locations in the Varanasi district of India were selected as they had been under potato cultivation for the past one decade and the scab pathogen was well established. Among the various treatments, the Pseudomonad strain R1 when applied with vermicompost gave the best plant growth and yield along with maximum reduction in scab incidence and scab index. The strain R1 was later identified as Pseudomonas mosselii. The treatment also showed maximum activities of the antioxidant enzyme peroxidase (POX) and the first enzyme of the phenylpropanoid pathway phenylalanine ammonia lyase (PAL) in a pot experiment till 72 h after pathogen challenge and then declined thereafter. Interestingly the activities of both POX and PAL were higher in the potato tuber peels, the active site of pathogen interaction, than in the potato leaves. The results revealed the potential of P. mosselii strain R1 in promoting plant growth as well as inducing antimicrobial mechanisms systemically in the host plants facilitated by the organic amendment in the form of vermicompost.Graphical abstractResearch highlights► Pseudomonas mosselii reduced common scab incidence and index in potato. ► P. mosselii increased peroxidase and PAL activities in tuber peel. ► Performance of P. mosselii enhanced by vermicompost. ► P. mosselii and vermicompost in combination increased tuber yield.
Antifungal compounds in the culture filtrate from Bacillus subtilis NSRS 89-24 that inhibited the growth of Pyricularia grisea and Rhizoctonia solani were mainly heat stable as the filter sterilized culture filtrate showed higher activity than an autoclaved one. The heat stable and labile components were due to an antibiotic and a β-1,3-glucanase, respectively. This β-1,3-glucanase was purified and characterized. Glucanase activity in the culture medium of B. subtilis NSRS 89-24 was inducible in the presence of 0.3% chitin, reaching a maximum on day 5. After purification, activity was associated with a protein of molecular mass of approximately 95.5 kDa by both gel filtration and native PAGE. Two major bands of Mr 64.6 and 32.4 kDa were revealed by SDS–PAGE. The enzyme had a Km of 0.9 mg/ml, and Vmax of 0.11 U, the optimal pH was 6.5–9.5 and was stable up to 50 °C. Both the pure enzyme and the antibiotic extract from the culture filtrate of the B. subtilis separately inhibited R. solani and P. grisea with MIC values of 12.5 and 6.25 mU/ml and 3.13 and 1.56 μg/ml, respectively. The glucanase enzyme in combination with the antibiotic showed a strong synergistic inhibitory effect on the hyphal growth of both fungi.
Biological control of soil-borne pathogens comprises the decrease of inoculum or of the disease producing activity of a pathogen through one or more mechanisms. Interest in biological control of soil-borne plant pathogens has increased considerably in the last few decades, because it may provide control of diseases that cannot or only partly be managed by other control strategies. Recent advances in microbial and molecular techniques have significantly contributed to new insights in underlying mechanisms by which introduced bacteria function. Colonization of plant roots is an essential step for both soil-borne pathogenic and beneficial rhizobacteria. Colonization patterns showed that rhizobacteria act as biocontrol agents or as growth-promoting bacteria form microcolonies or biofilms at preferred sites of root exudation. Such microcolonies are sites for bacteria to communicate with each other (quorum sensing) and to act in a coordinated manner. Elicitation of induced systemic resistance (ISR) by plant-associated bacteria was initially demonstrated using Pseudomonas spp. and other Gram-negative bacteria. Several strains of the species Bacillus amyloliquefaciens, B. subtilis, B. pasteurii, B. cereus, B. pumilus, B. mycoides, and B. sphaericus elicit significant reductions in the incidence or severity of various diseases on a diversity of hosts. Elicitation of ISR by these strains has been demonstrated in greenhouse or field trials on tomato, bell pepper, muskmelon, watermelon, sugar beet, tobacco, Arabidopsis sp., cucumber, loblolly pine, and two tropical crops (long cayenne pepper and green kuang futsoi). Protection resulting from ISR elicited by Bacillus spp. has been reported against leaf-spotting fungal and bacterial pathogens, systemic viruses, a crown-rotting fungal pathogen, root-knot nematodes, and a stem-blight fungal pathogen as well as damping-off, blue mold, and late blight diseases. This progress will lead to a more efficient use of these strains which is worthwhile approach to explore in context of biocontrol strategies.
A photo-induced cyclic peroxidation in isolated chloroplasts is described. In an osmotic buffered medium, chloroplasts upon illumination produce malondialdehyde (MDA)—a decomposition product of tri-unsaturated fatty acid hydroperoxides—bleach endogenous chlorophyll, and consume oxygen. These processes show (a) no reaction in the absence of illumination; (b) an initial lag phase upon illumination of 10–20 minutes duration; (c) a linear phase in which the rate is proportional to the square root of the light intensity; (d) cessation of reaction occurring within 3 minutes after illumination ceases; and (e) a termination phase after several hours of illumination. The kinetics of the above processes fit a cyclic peroxidation equation with velocity coefficients near those for chemical peroxidation.The stoichiometry of MDA/O2 = 0.02, and O2Chlbleached = 6.9 correlates well with MDA production efficiency in other biological systems and with the molar ratio of unsaturated fatty acids to chlorophyll. The energies of activation for the lag and linear phases are 17 and 0 kcal/mole, respectively, the same as that for autoxidation. During the linear phase of oxygen uptake the dependence upon temperature and O2 concentration indicates that during the reaction, oxygen tension at the site of peroxidation is 100-fold lower than in the aqueous phase.It is concluded that isolated chloroplasts upon illumination can undergo a cyclic peroxidation initiated by the light absorbed by chlorophyll. Photoperoxidation results in a destruction of the chlorophyll and tri-unsaturated fatty acids of the chloroplast membranes.
Recognition of an avirulent pathogen triggers the rapid production of the reactive oxygen intermediates superoxide (O2-) and hydrogen peroxide (H2O2). This oxidative burst drives crosslinking of the cell wall, induces several plant genes involved in cellular protection and defence, and is necessary for the initiation of host cell death in the hypersensitive disease-resistance response. However, this burst is not enough to support a strong disease-resistance response. Here we show that nitric oxide, which acts as a signal in the immune, nervous and vascular systems, potentiates the induction of hypersensitive cell death in soybean cells by reactive oxygen intermediates and functions independently of such intermediates to induce genes for the synthesis of protective natural products. Moreover, inhibitors of nitric oxide synthesis compromise the hypersensitive disease-resistance response of Arabidopsis leaves to Pseudomonas syringae, promoting disease and bacterial growth. We conclude that nitric oxide plays a key role in disease resistance in plants.
Reactive oxygen species are believed to perform multiple roles during plant defense responses to microbial attack, acting in the initial defense and possibly as cellular signaling molecules. In animals, nitric oxide (NO) is an important redox-active signaling molecule. Here we show that infection of resistant, but not susceptible, tobacco with tobacco mosaic virus resulted in enhanced NO synthase (NOS) activity. Furthermore, administration of NO donors or recombinant mammalian NOS to tobacco plants or tobacco suspension cells triggered expression of the defense-related genes encoding pathogenesis-related 1 protein and phenylalanine ammonia lyase (PAL). These genes were also induced by cyclic GMP (cGMP) and cyclic ADP-ribose, two molecules that can serve as second messengers for NO signaling in mammals. Consistent with cGMP acting as a second messenger in tobacco, NO treatment induced dramatic and transient increases in endogenous cGMP levels. Furthermore, NO-induced activation of PAL was blocked by 6-anilino-5,8-quinolinedione and 1H-(1,2,4)-oxadiazole[4,3-a]quinoxalin-1-one, two inhibitors of guanylate cyclase. Although 6-anilino-5,8-quinolinedione fully blocked PAL activation, inhibition by 1H-(1,2,4)-oxadiazole[4, 3-a]quinoxalin-1-one was not entirely complete, suggesting the existence of cGMP-independent, as well as cGMP-dependent, NO signaling. We conclude that several critical players of animal NO signaling are also operative in plants.
Nitric oxide functions as a signal in plant disease resistance
- M Delledonne
- Y Xia
- R A Dixon
- M. Delledonne
Searching ISR determinants from
- V Akram
- T Anjum
Effect of sodium nitroprusside on responses of
- R Amooaghaie
- Roohollahi
- Sh
Effect of vermicompost on growth
- R Amooaghaie
- Golmohammadi
- Sh
Searching ISR determinants from Bacillus subtilis IAGS174 against Fusarium wilt of tomato
- V Akram
- T Anjum
- V. Akram