Induction Of Defense Enzymes Research Articles

Exploring the potentiality of botanicals and phyllosphere microbiome for the management of anthracnose disease in Black gram (Vigna mungo L. Hepper)

Black gram (Vigna mungo L. Hepper) is the third most important pulse crop, and its yield is reduced due to many diseases. Among them, anthracnose is one of the devasting global fungal diseases which cause severe damage. Use of fungicide is highly effective in controlling this disease, but continuous use of fungicides is unsafe for environment, and it causes fungicidal resistance. To overcome these problems, effect of plant extracts viz., Anisomeles malabarica, Azadirachta indica leaf extracts, phyllosphere antagonist Bacillus amyloliquifaciens, and essential oils viz., peppermint oil and lemon grass oil were evaluated against black gram anthracnose disease caused by Colletotrichum lindimuthianum under pot culture. Among the different treatments tested, plants sprayed with standard chemical viz., Carbendazim @ 0.2 percent recorded the least percent disease index (PDI) of 13.39 followed by A. malabarica leaf extract (10%) treatments, which recorded a PDI of 16.62, whereas plants treated with B. amyloliquifaciens, lemongrass oil and peppermint oil recorded a PDI of 20.91, 21.23 and 24.0, respectively, compared to the inoculated control (77.33 PDI). The induction of defense enzymes viz., phenol, peroxidase (PO), polyphenol oxidase (PPO) was recorded more (21.25 µg of catechol/g of leaf tissue, 3.82 changes in absorbance/min/g leaf tissue, 3.32 changes in absorbance/min/g leaf tissue, respectively) in the plants sprayed with A. malabarica. GC-MS analysis of hexane and ethanol extract of A. malabarica showed the presence of 26 phytocompounds. Among them, phenol 2,4- bis (1,1- dimethylethyl) phosphite from ethanol extract was a predominant compound (100%). Formulation and standardization of dosage for phenol 2,4- bis (1,1- dimethylethyl) phosphite compound will be useful for managing the disease effectively.

Systematic induced resistance in Solanum lycopersicum (L.) against vascular wilt pathogen (Fusarium oxysporum f. sp. lycopersici) by Citrullus colocynthis and Trichoderma viride.

The antifungal effects of Citrullus colocynthis extract (Hexane, chloroform, methanol, and water) were tested in vitro on Fusarium oxysporum f. sp. lycopersici (Sacc.) W. C. Snyder & H. N. Hans (FOL), the causal agent of Fusarium wilt. Of these, methanol and water extract at 10% showed the highest inhibition of mycelial growth of FOL by 12.32 and 23.61 mm respectively. The antifungal compounds were identified through Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS). The methanol extract was compatible with the biocontrol agent Trichoderma viride. The antagonistic fungi were mass-cultured under laboratory conditions using sorghum seeds. Both T. viride and C. colocynthis methanol extract was also tested alone and together against FOL under both in vitro and in vivo conditions. The combination of T. viride and C. colocynthis showed the highest percentage of antifungal activity (82.92%) against FOL under in vitro conditions. This study revealed that induced systemic resistance (ISR) in enhancing the disease resistance in tomato plants against Fusarium wilt disease. The combined treatment of T. viride and C. colocynthis significantly reduced the disease incidence and index by 21.92 and 27.02% in greenhouse conditions, respectively. Further, the induction of defense enzymes, such as peroxidase (PO), polyphenol oxidase (PPO), β-1,3-glucanase, and chitinase were studied. The accumulation of defense enzyme was greater in plants treated with a combination of T. viride and C. colocynthis compared to the control. Reduction of wilt disease in tomato plants due to the involvement of defense-related enzymes is presumed through this experiment.

Harpin-loaded chitosan nanoparticles induced defense responses in tobacco

Phytopathogens entry into plant cell is restricted by several chemical substances which hamper the natural ecosystem and are expensive. Induction of defense responses in plants by elicitors is a better alternative approach to combat phytopathogens. Controlled and steady release of elicitors from nanoparticles core will improve the bioavailability and alleviate the repeated application of molecules that triggers the hypersensitive response (HR) in plants. Here we reported the efficacy of chitosan-harpin as nanoparticles in eliciting defense responses in tobacco wherein harpin (30 ng/mL) loaded chitosan nanoparticles (H-CSNPs) were prepared by ionotropic gelation method using chitosan and sodium tripolyphosphate (TPP). The nanoparticles were spherical and possess a size of about ∼160 nm with a zeta potential of 30.2 ± 0.7 mV. The FT-IR and XRD studies confirmed the formation of chitosan nanoparticles. The encapsulation efficiency of harpin was 85% and steady release was observed up to 4 h in releasing kinetics. Topical application of H-CSNPs resulted histopathological evidences which coincided with the induction HR specific marker genes viz., pathogenises related proteins and induction of defense enzymes. The harpin at nanogram concentrations with chitosan improved the bioavailability than the harpin or chitosan alone in the tobacco plant.

Synergistic Effect of Plant Defense Elicitors and Biocontrol Agents on Induction of Defense Enzymes in Pea against Downy Mildew

Background: Plant defense against the pathogens can be induced by using different defense inducers. Plants can be treated with elicitors for fast and more intense mobilization of defense responses which can enhance the resistance against biotic or abiotic stresses. Methods: The present study has been undertaken to evaluate the synergistic effect of different plant defense inducing chemical (Salicylic acid, Isonicotinic acid, Oxalic acid and Chitosan) and biological (Trichoderma harzianum and Pseudomonas fluorescens) elicitors. Enzyme activity was expressed as the increase in absorbance using spectrophotometer. Result: Among all the treatments the maximum PAL activity (35.58 mg/g of fresh weight) was found in case of oxalic acid but after 48 hrs its activity reduced drastically. Next to oxalic acid Pseudomonas fluorescens (31.38 mg/g of fresh weight), chitosan + Trichoderma harzianum (29.38 mg/g of fresh weight) and chitosan + Pseudomonas fluorescens (27.89 mg/g of fresh weight) showed the maximum enzyme activity. The PPO activity reached the highest at 96 hr after challenge inoculation in case of chitosan + Trichoderma harzianum (9.74 µmol/min/mg/protein) treated plants followed by Trichoderma harzianum (3.53 µmol/min/mg/protein) alone. the maximum PO activity (49.12 µmol/min/mg/protein) was found in case of chitosan + Pseudomonas fluorescens treated plants followed by chitosan (42.48 µmol/min/mg/protein) after 72 hrs. the maximum phenolics (27.53 mg/gm of fresh weight) was found in case of chitosan + Pseudomonas fluorescens after 48 hrs of treatment.

Upregulation of defense enzymes in groundnut (Arachishypogaea L.) by combined application of Trichoderma spp. and Mahua oil cake against Sclerotium rolfsii

Groundnut is one of the world's most popular edible legumes. Many soil-borne diseases were affected, among them, most notorious pathogen, Sclerotium rolfsii, which caused substantial constraints in groundnut production and productivity. Biological control offers wider treatment modalities than conventional chemical control. Under present study, induction of defense enzymes [PAL (phenylalanine ammonia lyase), PO (peroxidase), PPO (Polyphenol oxidase) and phenol] in groundnut treated with Trichoderma spp. and organic amendment (mahua oil cake) challenged with the S. rolfsii was studied. Highest PAL (0.298 changes in absorbance/minute/gram of leaf tissue), PO (0.291 changes in absorbance/minute/gram of leaf tissue /minute/gram), PPO (0.296µmole of transcinnamic acid/minute/gram) and Phenol (781µgram of catechol/g) activity was recorded in plants treated with sequential application of Trichoderma spp. and mahua oil cake. Inoculated control has shown minimum defense enzyme activity. Results suggest the role of Trichoderma spp. and mahua oil cake in inducing higher defense enzyme activity on groundnut against S. rolfsii.

ELICITATION OF PLANT DEFENSE AGAINST FUSARIUM OXYSPORUM F.SP. CICERIS IN CHICKPEA PLANT USING MARINE MICROCOCCUS SP.

Chickpea is produced as well as consumed highest in India amongst the whole world but, production is seriously curtailed by Fusarium wilt, caused by Fusarium oxysporum f.sp. ciceris (FOC). In stressful conditions, the reactive oxygen species (ROS) production increases in plants which cause significant damage. To reduce this ROS, plants have inbuilt antioxidants that can detoxify ROS and protect cells of plants. The present study aimed to investigate the effect of Micrococcus luteus on the induction of defense enzymes in the presence and absence of Fusarium in chickpea. Talc-based bio-formulation of marine M. luteus was employed under pot trials to scrutinize mechanism of induced resistance against Fusarium by the improvement of defense enzymes like SOD, POX as well as accumulation of L-proline, total phenolic and pigments like chlorophyll and carotenoids. Pot trials were done using four different conditions- T1 (control), T2 (M. luteus treated), T3 (FOC treated), and T4 (M. luteus + FOC treated). Defense enzymes were studied and a maximum increase in M. luteus treated plants as compared to control and pathogen treated plants were noted. The chlorophyll and carotenoid content were improved in M. luteus treated plants to pathogen treated plants. This study indicated that M. luteus helps the plant to protect itself from free radicals as it showed significant induction of enhanced plant defense response against soil-borne pathogen to protect chickpea plant.

Isolation and identification of a novel protein elicitor from a Bacillus subtilis strain BU412

Here, we report a novel protein elicitor from Bacillus subtilis BU412 which could cause hypersensitive response (HR) and systemic acquired resistance (SAR) in tobacco. The purification was executed by ion-exchange and size exclusion chromatography. The target band on SDS-PAGE was analyzed by mass spectrometry, and the peptide mass fingerprinting matched an uncharacterized protein (WP_017418614.1), which was then named AMEP412. AMEP412 could cause a clearly defined HR necrosis in tobacco leaves, which was less affected by thermal treatment. The sub-cellular localization assay revealed that AMEP412 localized on the cell surface. This protein could also trigger early defense events such as the generation of reactive oxygen species (H2O2 and O2−) and the induction of defense enzymes, including superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL). Moreover, AMEP412 could stimulate plant systemic resistance against Pseudomonas syringae pv. tomato DC3000.

Toxicity of Chlorpyrifos and and its Bioremediation using Pseudomonas putida

The toxicity of chlorpyrifos (CP) against the fish Ctenopharyngodon idella, (Grass carp), evaluated according to the OECD guidelines for testing of chemicals 203, showed its 96 h LC50 to be 12.387 μgL−1 at 95 per cent confidence limits. The toxicity was also evident from the degeneration of gill lamellae. A microcosm study in normal, CP amended and CP amended soil with Pseudomonas putida provided the microbial strength and dehydrogenase activity. Statistical significance of the calculated Karl Pearson correlation coefficient (r) using the t-test procedure revealed that all the treatments correlated at 0.05 level of significance. Effect of CP on germination of rice seed revealed that as the exposure concentration of CP increased, the germination percentage as well as the germination rate, decreased. Decrease in the plant growth parameters also confirmed the high toxic effect of CP on rice seed germination. Enzyme activity was found to be higher in CP treated rice plants whereas a significant decrease was seen in the induction of defense enzymes; poly phenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and peroxidase (PO) in plants being augmented with Pseudomonas putida.

Induction of defense enzymes and control of anthracnose in cucumber by Corymbia citriodora aqueous extract

ABSTRACT Secondary compounds of medicinal plants can activate defense mechanisms in plants against pathogens. The aqueous extract (AE) of Corymbia citriodora has shown that activity, but there is scarce information about the involved mechanisms of action. Therefore, this study aimed to evaluate the effect of AE on the induction of defense enzymes and protection of cucumber from Colletotrichum lagenarium. Thus, the AE, autoclaved or not, was evaluated for its capability of protecting and inducing peroxidases, polyphenoloxidases, chitinases and β-1.3-glucanases, and phenylalanine ammonia-lyase. Distilled water and acibenzolar-S-methyl (50 mg a.i. L-1) were used as controls. The effect of AE at the concentrations of 1, 5, 10, 15 and 20% was also evaluated, as well as its local and systemic effect, and the effect of one or two applications. Pathogen inoculation or sample collection for determination of enzyme activity was performed at 72 hours after treatments. The AE reduced the severity of C. lagenarium and induced peroxidases and β-1.3-glucanases by 37.6, 67.2 and 122.7%, respectively. There was a reduction in the disease severity and an increase in peroxidases from the concentration of 5% AE. The latter showed only local effect and greater reduction in severity when two applications were performed. These results suggest the effect of AE in inducing resistance in cucumber and inducing peroxidases and β-1.3-glucanases.

Quantitative proteomics analysis reveals the tolerance of wheat to salt stress in response to Enterobacter cloacae SBP-8.

Salinity stress adversely affects the plant growth and is a major constraint to agriculture. In the present study, we studied the role of plant growth promoting rhizobacterium (PGPR) Enterobacter cloacae SBP-8 possessing ACC deaminase activity on proteome profile of wheat (Triticum aestivum L.) under high salinity (200 mM NaCl) stress. The aim of study was to investigate the differential expressed protein in selected three (T-1, T-2, T-3) treatments and absolute quantification (MS/MS analysis) was used to detect statistically significant expressed proteins. In this study, we investigated the adaptation mechanisms of wheat seedlings exposed to high concentration of NaCl treatment (200 mM) for 15 days in response to bacterial inoculation based on proteomic data. The identified proteins were distributed in different cellular, biological and molecular functions. Under salt stress, proteins related to ion-transport, metabolic pathway, protein synthesis and defense responsive were increased to a certain extent. A broader comparison of the proteome of wheat plant under different treatments revealed that changes in some of the metabolic pathway may be involved in stress adaption in response to PGPR inoculation. Hierarchical cluster analysis identified the various up-regulated/down-regulated proteins into tested three treatments. Our results suggest that bacterial inoculation enhanced the ability of wheat plant to combat salt stress via regulation of transcription factors, promoting antioxidative activity, induction of defense enzymes, lignin biosynthesis, and acceleration of protein synthesis.

Control of Phytophthora melonis damping-off, induction of defense responses, and gene expression of cucumber treated with commercial extract from Ascophyllum nodosum

This study examined the effects of Marmarine, a marine plant extract formulation from Ascophyllum nodosum, on Phytophthora melonis. Greenhouse cucumber plants were sprayed and/or root drenched using Marmarine at 0.5 or 1 % concentration twice at 10-day intervals. Treatments also included application of fungicide (metalaxyl, 2 g L−1) alternating with Marmarine application. Treated plants were inoculated with P. melonis. Marmarine application resulted in a significant reduction in disease incidence of pathogen tested. Combined spray and root drenching with Marmarine was more effective than either spray or root drenching alone. The alternation of one fungicide application, alternated with Marmarine application, was highly effective and found to be the best treatment in reducing the disease ratings. Plants treated with Marmarine showed enhanced activities of various defense-related enzymes including β-1,3-glucanase, peroxidase, and polyphenol oxidase. Altered transcript levels of various defense genes, including cucumber pathogen-induced 4, lipoxygenase, phenylalanine ammonia lyase, and galactinol synthase, were observed in treated plants. Cucumber plants treated with Marmarine also accumulated higher level of phenolics compared to water controls. These results suggest that seaweed extracts enhance disease resistance in cucumber probably through induction of defense enzymes and genes.

In Vitro and Enzymatic Studies of Inhibitory Activities of Three Trichoderma Species against Pythium Aphanidermatum in Infected Sweet Pepper

This study investigated the antifungal activities of Trichoderma species against Pythium aphanidermatum; determined and measured the induction of defense enzymes (such as peroxidase, polyphenol oxidase and phenylalanine ammonia lyase) by Trichoderma species in seedlings inoculated with Pythium aphanidermatum. This was with a view to obtaining the best antagonist among the Trichoderma species. Inhibition percentages of the three Trichoderma species on Pythium aphanidermatum were determined via dual inoculation method and via production of volatile compounds. Fifteen day old seedlings of treated and untreated seeds were inoculated with 5 X 105 spores/ml of Pythium aphanidermatum. Extraction of enzymes was carried out at different time interval of 1, 3, 5, 7, 9 and 11 days after pathogenic inoculation and they were assayed. The phenolic content for each of the treatment was also determined. The in vitro results suggested that, Trichoderma harzianum and T. koningii inhibited the growth of Pythium aphanidermatum mainly through their higher competitive abilities for space (on the plate) and nutrients at the expense of P. aphanidermatum, while T. atroviride inhibited the growth of P. aphanidermatum on the third day before occupying the space and absorbing nutrients from the substrates. The peroxidase activities were higher in T. atroviride plus pathogen in comparison with its activities in T. atroviride alone, T. harzianum alone and pathogen alone, while higher accumulation of phenolic contents was recorded in dual inoculations with T. atroviride than with T. harzianum. The study confirmed the ability of T. atroviride to inhibit the infection of P. aphanidermatum through the induction of activities of oxidative enzymes, competition and mycoparasitism, which was found to be high in interactions with the pathogen at all levels.

Application of nano-glucan to turmeric rhizome induce defence response against Pythium aphanidermatum

Pythium aphanidermatum is the causal agent of rhizome rot disease in Curcuma longa (L.). We have isolated glucan from the mycelium of P. aphanidermatum and synthesised nano-glucan by ionic gelation method. The synthesised nano-glucan was tested for its efficacy on germination, plant growth and induction of defence enzymes in turmeric rhizomes. Turmeric rhizomes treated with nano-glucan showed enhanced germination and growth rate when compared to control. Application of nano-glucan also induced defence enzymes such as chitinase, chitosanase, protease inhibitors, β-1,3-glucanase, peroxidase and polyphenol oxidase in turmeric rhizomes. Gel electrophoresis revealed new polypeptides of defence enzymes in turmeric rhizomes treated with nano-glucan. Nano-glucan-treated plants also showed a reduced rhizome rot incidence when compared to control. Enhanced activities of defence enzymes may restrict the development of P. aphanidermatum and reduced the rot incidence in rhizomes treated with nano-glucan.

Induction of defence response against blister blight by calcium chloride in tea

Tea, the second most consumed beverage after water in the world, is produced from the processed tender leaves of tea plants (Camellia sinensis). Production of tea is hindered by various biotic and abiotic stresses. Among the biotic factors, blister blight disease caused by an obligate fungal pathogen, Exobasidium vexans Massee, is a serious problem to the tea industry. The present study was to evaluate the efficacy of elicitor calcium chloride (CaCl2) in inducing resistance in tea plants against blister blight disease. During the pick time of blister incidence at Darjeeling tea garden, the application of CaCl2 at a concentration of 1% resulted in disease inhibition around 71% over the control set. Treatment also resulted in the induction of defence enzymes like peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, β-1,3-glucanase and higher phenol accumulation. Furthermore, the increase in defence molecules also correlated with increase in nitric oxide (NO) generation, a potent defence molecule in plant defence. The result suggests that CaCl2 can used as a potential elicitor in the integrated disease management in organic tea cultivation.

Induction of systemic resistance in green gram against leaf blight caused by Macrophomina phaseolina (Tassi.) Goid

Studies were conducted to develop the sustainable plant protection strategies against leaf blight of green gram incited by Macrophomina phaseolina by using plant extracts and fungicides under in vitro and in vivo conditions. In vitro studies indicated that plant leaf extracts of Adenocalymma alliaceum (77.20%) and Allium sp. (74.71%) demonstrated the highest inhibition of mycelia growth of M. phaseolina at 10% concentration. The results revealed the significant performance by foliar spray of carbendazim (0.1%), mancozeb (0.2%) and leaf extracts of A. alliaceum (10%), Allium sp. (10%) was more effective in reducing leaf blight disease in mungbean plants under greenhouse conditions. Further, induction of defense enzymes, such as peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), phenols and also chlorophyll content were studied. The enzyme accumulation was greater in treated plants as compared to untreated control. The present study revealed the induced systemic resistance (ISR) in enhancing the disease resistance in green gram plants against leaf blight disease by the application of plant extracts and fungicides. Key words: Macrophomina phaseolina, induced systemic resistance (ISR),Adenocalymma alliaceum, Allium sp.

Changes in the activities of glutathione-S-transferases, glutathione reductase and catalase after exposure to different concentrations of cadmium in Australoheros facetus (Cichlidae, Pisces)

The goal of this work was to evaluate the response of the glutathione-S-transferases (GST), glutathione reductase (GR) and catalase (CAT) enzymes in different tissues of the fish Australoheros facetus exposed cadmium (Cd). In liver, a significant decrease of GST activity was observed at 0.031 mg L-1 (p<0.05), while, at higher concentrations, there were non-significant changes compared to controls. Neither the GR nor the CAT activity was different from control. Gills was the most sensitive organ, showing increased GST activity at 0.31 and 1.53 mg L-1 and GR at 3.06 mg L-1; while CAT activity was inhibited at 0.31, 3.06 and 6.13 mg L-1 (p<0.05). The brain GST activity was increased at 1.53 mg L-1 but inhibited at 3.06 and 6.13 mg L-1, meanwhile GR and CAT activities were inhibited at 1.2, 3.06 and 6.13 mg L-1 (p<0.05). The induction of defense enzymes as well as the inhibition of the antioxidant enzyme catalase, even at environmentally relevant concentrations used in this work (e.g. 0.31 mg L-1), denotes the toxic effect that cadmium exerts over the tissues of A. facetus and alerts over the need of doing biomonitoring in areas potentially polluted with metals.

NDUCTION OF SYSTEMIC RESISTANCE IN RICE BY PSEUDOMONAS FLUORESCENT AGAINST RICE ROOT KNOT NEMATODE MELOIDOGYNE GRAMINICOLA

Induction ofdefense enzymes phenol, peroxidase (PO), polyphenol oxidase (PPO),phenyl ammonia lyase (PAL), super oxide dismutase (SOD) and chitinase by Pseudomonasfluorescens isolate Pf1, against challenge inoculation of Meloidogynegraminicola in rice was studied in vitro. The activity of phenol,PO,PPO, PAL and chitinase was higher in the bacterized rice plants. Theanalysis of isoform profiles revealed unique PO, PPO and SOD isoforms inducedin plants treated with P. fluorescens. The present study implies earlierand higher accumulation of phenols and defense enzymes viz., PO, PPO,PAL and chitinase in rice root tissue resulting in significant reduction innematode infection.

Rhizobacterial-mediated induction of defense enzymes to enhance the resistance of turmeric (Curcuma longa L) to Pythium aphanidermatum causing rhizome rot

Rhizobacteria isolated from the rhizosphere soil were evaluated for their ability to control rhizome rot in turmeric (Curcuma longa L). These isolates were characterised as Pseudomonas fluorescens and Bacillus subtilis. Under in vitro condition, two isolates, namely P. chlororaphis (PcPA23) and B. subtilis (BsCBE4), showed maximum inhibition of mycelial growth of Pythium aphanidermatum, were found effective in reducing rhizome rot of turmeric both under greenhouse and field conditions and increased the plant growth and rhizome yield. Both the isolates were further tested for its ability to induce production of defense-related enzymes and chemicals in plants. Increased activities of phenylalanine ammonia lyase, peroxidase, polyphenol oxidase, chitinase and β-1,3-glucanase were observed in PcPA23 and BsCBE4 pre-treated turmeric plants challenged with P. aphanidermatum. Moreover, higher accumulation of phenolics was noticed in plants pre-treated with PcPA23 and BsCBE4 challenged with P. aphanidermatum. Thus, the present study shows that in addition to direct antagonism and plant growth promotion, induction of defense-related enzymes involved in the phenyl propanoid pathway collectively contributed to enhance resistance against invasion of Pythium in turmeric.

Screening of Pseudomonas fluorescens isolates for biological control of Macrophomina phaseolina root-rot of safflower

The aim of this study was to assess the potential bacterial antagonists to control Macrophomina phaseolinaroot-rot of safflower by using screening methods. In total, 38 fluorescent pseudomonads isolated from rhizosphere soil of healthy safflower plants were collected from major safflower growing areas, 13 were initially selected based on dual culture technique on potato dextrose agar media. Furthermore, these13 isolates were screened for reduction of percent incidence of M. phaseolina and to check their efficacy in seed germination and seedling growth in laboratory condition. Most of the isolates showed varying levels of antagonism againstM. phaseolina in both standard blotter method and paper towel method. In addition, few isolates increased percent germination, root-shoot lengths of safflower. Among them, CTPF31 showed the highest ability to reduce the root-rot disease severity in the greenhouse biological control test. The promised fluorescent pseudomonads (CTPF31 and CTPf36) enhanced the defense enzymes, peroxidase, PAL, β 1,3-glucanase, and chitinase after challenge inoculation with the target pathogen. These results indicated that the dual culture technique and seedling assay are more important for selection of promising biocontrol agents against M. phaseolina, besides they also increased the plant growth by controlling the disease as evidenced by induction of defense enzymes. Key words: Plant growth-promoting Rhizobacteria, safflower, root-rot, Macrophomina phaseolina, Pseudomonas fluorescens, biological control.

Biological control of sheath blight disease of rice by siderophore producing rhizobacterial strains and their role in efficient mobilisation of micronutrients from soil

Four siderophore producing rhizobacterial strains Bacillus cereus Z2-7, Enterobacter sp. B41 strain SPR7, Aeromonas hydrophila BPS10 and Enterobacter sp. BPS12 isolated from rice grown in saline soils were examined for induction of chitinases, glucanases and peroxideses (POX) in rice plants against sheath blight pathogen R. solani and mobilization of micronutrients from rice rhizosphere to straw and grain of rice plant. Atomic absorption studies indicated that rice plants preinoculated with Bacillus cereus Z2-7 have an increased uptake of zinc, copper and iron as compared to uninoculated control plants. High content of copper and iron were present in straw while high quantity of zinc was found in grains. Straw of rice plants inoculated with Enterobacter sp. B41 strain SPR7 contained highest Manganese content as compared to other treatments and uninoculated control plants. Gene expression analysis revealed enhanced levels of chitinase, peroxidase and glucanase expression in rice plants preinoclated with bacterial strains Z2-7 and SPR7 after 7 and 52 days of challenge inoculation with R. solani. Improved uptake of micronutrients and induction of defence enzymes in these plants resulted in an increase in yield of these plants as compared to rest of the treatments.