In vitro effect of fermented maize slurry and ethanol extracts of five plants against Sclerotium rolfsii Sacc. of tomato (Lycopersicon esculentum Mill.)

Sclerotium rolfsii Sacc. is an important fungal pathogen affecting the production of tomato (Lycopersicon esculentum Mill.). Conventional control methods using chemicals are expensive, which constitute environmental hazards. This has necessitated the search for alternatives in botanicals. Ethanol and supernatant solution of fermented maize slurry extracts from Ocimum gratissimum, Cymbopogon citratus, Xylopia aethiopica, Aframomum melegueta and Allium sativum were evaluated. In vitro test was carried out at 1, 2, 3, 4 and 5% concentrations against the pathogen. Mycelial growth was significantly reduced in the following descending order: O. gratissimum?>?A. melegueta?>?A. sativum?>?X. aethiopica?>?C. citratus. Supernatant solution extracts of O. gratissimum and A. melegueta at 5% concentration gave highest mycelial reduction (0.00?mm), respectively, while O. gratissimum ethanol extract recorded highest mycelial reduction (0.23?mm) among the ethanol extracts. Supernatant solution of fermented maize slurry extracts of O. gratissimum and A. melegueta at 5% concentration was more effective in reducing mycelial growth of S. rolfsii.     

In vitro kinetics and antifungal activity of various extracts of Terminalia chebula seeds against plant pathogenic fungi

The aim of the present study was to examine the efficacy of various seed extracts of Terminalia chebula as an antifungal potential against certain important plant pathogenic fungi. The organic extracts of methanol, ethyl acetate and chloroform at the used concentration of 1500 ppm/disc revealed remarkable antifungal effect as a fungal mycelial growth inhibitor against Fusarium oxysporum, Fusarium solani, Phytophthora capsici and Botrytis cinerea, in the range of 41.6–61.3%, along with MIC values ranging from 62.5 to 500 μg/ml. Also, the extracts had a strong detrimental effect on spore germination of all the tested plant pathogens along with concentration as well as time-dependent kinetic inhibition of B. cinerea. The results obtained from this study suggest that the natural products derived from Terminalia chebula could become an alternative to synthetic fungicides for controlling such important plant pathogenic fungi.     

Antifungal and larvicidal activities of two acyclic monoterpenes; citral and geraniol against phytopathogenic fungi and insects

Abstract

Citral and geraniol are dominating constituents of lemon and rose scented essential oils of Cymbopogon spp. Here, we report their antifungal activity against some pathogenic fungi Drechslera oryzae, Fusarium oxysporum, Rhizoctonia solani and Sclerotium rolfsii and larvicidal activity against two insects Helicoverpa armigera and Spodoptera litura. Results revealed that both citral and geraniol exhibited strong fungicidal effects at concentrations > 0.2 µL mL^?1. Citral was found most active against F. oxysporum and S. rolfsii while geraniol against S. rolfsii at 0.2–2 µL mL^?1. Nanoemulsions of citral and geraniol caused 91 and 94% larval mortality of H. armigera and S. litura, respectively, at 1% concentration. Hence, the study revealed potential antifungal and larvicidal activities of citral and geraniol, which can be implicated in formulation of biocides for effective control of phytopathogenic fungal and insects.     

Evaluation of antifungal potential of Marchantia polymorpha L., Dryopteris filix-mas (L.) Schott and Ephedra foliata Boiss. against phyto fungal pathogens

Methanol and flavonoid extracts (free and bound) of Marchantia polymorpha L., Dryopteris filix-mas (L.) Schott and Ephedra foliata Boiss. were screened against three fungal plant pathogens: Alternaria solani, Fusarium oxysporum and Rhizoctonia solani. The extracts from D. filix-mas and E. foliata showed >80% of mycelial inhibition of A. solani whereas M. polymorpha and D. filix-mas (rhizome) completely inhibited the mycelial growth of R. solani when tested at highest concentration (5 mg/ml). Inhibition of spore germination of fungi (A. solani and F. oxysporum) was observed to be 100% by most of the extracts at 10 mg/ml. Moreover, plant extracts were found effective in increasing seed germination and seed vigour simultaneously thereby decreasing the percentage of pathogen infection. The results of the present study reveal that the plants screened possess the potential to inhibit the crop fungal pathogens and further investigation is required to explore the biologically active constituents of these plants and to use them as natural plant protectants for agriculture.     

Impact of salinity stress on soil-borne fungi of sugarbeet

The sugarbeet cultivar Kaumera was found to be highly susceptible to infection by the root-rot pathogens Rhizoctonia solani and Sclerotium rolfsii in the absence of salinity stress. Under this environmental condition, R. solani was more efficient than S. rolfsii in producing cell wall-degrading enzymes in infected hypocotyls. Xylanase and galactanase were most effective. The rate of cell wall degradation by R. solani was nearly 2.5 times that of S. rolfsii when cells walls of healthy hypocotyls were used as sole carbon substrate for the in vitro produced crude enzymes.Under salinity stress the pathogenicity and the performance of cell wall-degrading enzymes of R. solani and S. rolfsii varied profoundly. Pathogenicity studies showed that R. solani appeared to be more tolerant than S. rolfsii of the salinity stresses applied, and relatively more virulent to cv Kaumera. The activities of cell wall enzymes of R. solani decreased and those of S. rolfsii increased with increased salt concentration when cell wall material was used as a sole carbon source. The metabolic products produced under salinity stress by R. solani and R. solani in the cell wall amended culture media shifted the initial pH towards neutrality or slight alkalinity for R. solani and to high acidity for S. rolfsii.When model substrates were used, xyland and galactan were the most responsive substrates for degradation by the cell wall enzymes of the two fungi studied. The rate of degradation was higher for S. rolfsii than for R. solani. The excessive acidity in salt stressed S. rolfsii culture media suggested reduced activities of the enzymes involved in cell wall degradation in vivo. This may explain the decreased virulence potentialities.     

Broad spectrum action of phenazine against active and dormant structures of fungal pathogens and root knot nematode

Antifungal antibiotic from Pseudomonas chlororaphis isolate PA23 was identified as Phenazine using TLC and HPLC. Phenazine recorded the highest inhibition zone of 21?mm with 35.55% percent inhibition of mycelial growth of Pythium aphanidermatum over control. It had a significant effect on the hyphal morphology of P. aphanidermatum and on spore germination of Botryodiplodia theobromae and Alternaria solani. Disorganization of hyphal morphology of P. aphanidermatum includes vacuolization, cell content degeneration and hyphal lysis. Similarly interaction of phenazine with Rhizoctonia solani resulted in abnormal swelling of hyphal tips was noticed in the hyphal tips. Similarly the germination of sclerotia of Macrophomina phaseolina, R. solani and Sclerotium rolfsii were completely inhibited by phenazine at a concentration 50?μl. Incubation of the eggs of the root knot nematode Meloidogyne incognita in 30?μl concentration of phenazine, completely suppressed the hatching of juveniles.     

Fungitoxic activity of fruit extracts of Syzygium cumini (L.) Skeels against plant pathogenic fungi Alternaria alternata and Fusarium oxysporum

This study was aimed to evaluate the effectiveness of the aqueous and ethanolic extracts of fruits of Syzygium cumini, against the mycelial growth of Alternaria alternata and Fusarium oxysporum. The results showed that ethanolic extract at the concentrations of 7.5 and 9?mg/ml completely inhibited the mycelial growth of A. alternata and F. oxysporum, respectively. While the aqueous extract at a highest tested concentration (37.5?mg/ml) exhibited only 27.86 and 37.23% inhibition of mycelial growth of A. alternata and F. oxysporum, respectively. The spore germination assay also showed the complete inhibition of spore germination of A. alternata and F. oxysporum by ethanolic extract at 50 and 60?mg/ml concentrations, respectively. Minimum inhibitory concentration was recorded as 0.039 and 0.156?mg/ml in ethanolic extract and 20 and 6.25?mg/ml in aqueous extract against A. alternata and F. oxysporum, respectively. Phytochemical analysis also showed the presence of high amount of phenolics, tannins, flavonoids, alkaloids and saponins.     

Antifungal and antibacterial potential of methanol and chloroform extracts of Marchantia polymorpha L.

The methanol and chloroform extracts of Marchantia polymorpha were tested against three Gram-negative bacterial strains, viz. Xanthomonas oryzae pv. oryzae, Salmonella enterica and Pasturella multocida and four fungal strains, viz. Tilletia indica Mitra, Fusarium oxysporum f. sp. lini, Sclerotium rolfsii Sacc. and Rhizoctonia solani Kuhn. by using disc diffusion and micro broth dilution techniques. Both the extracts showed unique activity against X. oryzae and P.multocida [per cent inhibition (PI) 11.58 and 12.55, minimum inhibitory concentration (MIC) 2.50 and 1.25 μg/mL, minimum bactericidal concentration (MBC) 2.75 and 1.25 μg/mL, respectively] but for fungi, it was shown against S.rolfsii and F. oxysporum [PI 32.65 and 33.44, MIC 2.50 and 0.65 μg/mL, minimum fungicidal concentration (MFC) 4.50 and 0.65 μg/mL, respectively].The extracts possessed antimicrobial activity with different potency against variety of micro-organisms pathogenic to plants as well as animals. Some extracts were fungistatic and bacteriostatic (methanol extract against R. solani and chloroform extract against F. oxysporum and methanol extract for bacteria, respectively), while rest showed fungicidal/bactericidal potential. The results suggest the potential of M. polymorpha for developing a broad spectrum antimicrobial formulation in future.     

Inhibition of growth of Sclerotinia minor and other pathogens by citrinin in the filtrate of Penicillium citrinum

Penicillium citrinum Thom, isolated from the sclerotia of Sderotinia minor, was cultured in a broth of Czapek-Dox for 4 to 8 weeks. The filtrate obtained was incorporated into potato dextrose agar or Czapek-Dox agar at different concentrations (v/v). The amended media were tested for mycelial growth of S. minor and other pathogens. Mycelial growth of S. minor was completely inhibited on media amended with 20% (v/v) filtrate of P. citrinum, and considerable inhibition of S. minor occurred at 10 and 15% concentrations. Mycelial growth of S. major, Sclerotium rolfsii, Rhizoctonia solani (AG-4) was inhibited by similar concentrations of filtrate of P. citrinum. Inhibitor(s) in the filtrate were extracted with ethyl acetate and tentatively identified as citrinin. Citrinin was shown to be an active component in the filtrate against mycelial growth of S. minor, S. major and Sclerotium rolfsii.Cooperative investigation of U.S. Department of Agriculture, Agriculture Research Service and Oklahoma State University. Journal Article No. 4989, Oklahoma Agricultural Experiment Station, Oklahoma State University, Stillwater.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by USDA or by Oklahoma State University, or imply their approval to the exclusion of other products or vendors that may also be suitable.     

Antimicrobial activities of extracts of Cyperus rotundus L. rhizomes against some bacterial and fungal pathogens of strawberry and tomato

Antimicrobial activities of rhizome extracts of Cyperus rotundus were investigated on selected plant pathogenic bacteria and fungi. Ethyl acetate and hexane extracts showed antibacterial activity against three isolates of Clavibacter michiganensis subsp. michiganensis at concentrations of 900 and 1000 μg/ml. However, Gram-negative bacterial pathogens of tomato; Pseudomonas syringae pv. tomato and Ralstonia solanacearum were not inhibited from the extracts. Ethyl acetate extracts at 100 μg/ml inhibited mycelial growth and spore germination of the two strawberry isolates of Botrytis cinerea; however, no significant inhibition was found in tomato fungal pathogen, Fusarium oxysporum f. sp. radicis lycopersici. Minimum inhibitory concentrations were determined as 0.0625 and 0.125 mg/ml against C. michiganensis subsp. michiganensis for ethyl acetate and hexane extracts of rhizomes, respectively. This study shows the potentials of extracts of C. rotundus rhizomes as antimicrobial agents that are effective against the tested plant pathogenic bacteria and fungi.     

Optimization of the extraction of phenolic compounds from Cyclosorus extensa with solvents of varying polarities

The leaves of Cyclosorus extensa are used in the preparation of rice beer in Assam, India. The optimal conditions of time and temperature of fermentation for extraction of bioactive compounds from the dried leaves were obtained using response surface methodology. The central composite rotatable design was used and 13 experimental runs based on two-factor-five-level design were generated and performed for each of the solvents. The independent variables were extraction time (12 and 48?h) and temperature (25 and 55°C). The responses studied were total polyphenol content, radical scavenging activity, antibacterial activity, and antifungal activity. The analysis of variance of the test data was performed and the sequential sum of squares, F-value, R², and adjusted R² were deduced. The predicted models for all the response variables were adequately fitted to the observed experimental data (p?≤?0.001). The maximum extraction of bioactive compounds under the optimum conditions of extraction temperature and time for hexane, ethyl acetate, methanol, and distilled water were found to be 25°C for 29.43?h, 28.28°C for 41.27?h, 43.95°C for 29.61?h, and 55.00°C for 48.00?h, respectively. It was also observed that the solubility of the polyphenols was higher in methanol, followed by ethyl acetate, and the highest antibacterial activity against Escherichia coli was shown by the ethyl acetate extracts.     

Broad-spectrum antimicrobial activity of volatile organic compounds from endophytic Pseudomonas putida BP25 against diverse plant pathogens

ABSTRACT

Black pepper endophytic Pseudomonas putida BP25 produced diverse antimicrobial volatile organic compounds having potential for plant disease management. Chemically synthesised volatiles such as 2, 5-dimethyl pyrazine; 2-methyl pyrazine; dimethyl trisulphide; 2-ethyl 5-methyl pyrazine; and 2-ethyl 3, 6-dimethyl pyrazine showed inhibitory activity against oomycete pathogens, Phytophthora capsici & Pythium myriotylum; fungal pathogens, Rhizoctonia solani, Colletotrichum gloeosporioides, Athelia rolfsii, Gibberella moniliformis & Magnaporthe oryzae; bacterial pathogen, Ralstonia pseudosolanacearum and plant parasitic nematode, Radopholus similis. Among them, dimethyl trisulphide completely inhibited oomycete and fungal pathogens as well as R. similis at a concentration of 2.65?µg?cm^?3 under in vitro conditions. Pyrazines suppressed Phytophthora lesions on shoot cuttings of black pepper upon in planta volatile treatment. Dimethyl trisulphide was the only compound that exhibited soil fumigant activity against P. capsici, R. solani and A. rolfsii (6.25?µg?cm^?3), C. gloeosporioides and G. moniliformis (12.5?µg?cm^?3), and R. similis (50?µg?cm^?3). Altogether, endophytic Pseudomonas putida BP25 and its volatile organic compounds offer an alternative strategy for eco-friendly disease management in agriculture.     

<Emphasis Type="Italic">Exiguobacterium acetylicum</Emphasis> strain 1P (MTCC 8707) a novel bacterial antagonist from the North Western Indian Himalayas

Exiguobacterium acetylicum strain 1P (MTCC 8707) is a rhizospheric, Gram positive, rod shaped, yellow pigmented bacterium isolated from an apple orchard rhizospheric soil, on nutrient agar plates incubated at 4°C. The species level identification was arrived on the basis of 16S rRNA gene sequencing. The sequence showed 98% similarity with sequences of E. acetylicum available in the public domain. The strain was positive for siderophore and HCN production. In separate invitro assays it was found to inhibit the growth and development of Rhizoctonia solani, Sclerotium rolfsii, Pythium and Fusarium oxysporum. The volatile compound produced by the bacterium was found to be the most potent in inhibiting the hyphal development of R. solani, S. rolfsii, Pythium and F. oxysporum by 45.55, 41.38, 28.92 and 39.74% respectively. Commonly observed deformities caused by the diffusible and volatile compounds produced by the bacterium included hyphal inhibition, constriction and deformation. Under pot culture conditions the bacterium improved the germination and early growth parameters of pea (Pisum sativum) in the presence of R. solani and S. rolfsii.     

Combination of Pseudomonas aeruginosa and Pochonia chlamydosporia for Control of Root-Infecting Fungi in Tomato

A plant growth‐promoting rhizobacterium, Pseudomonas aeruginosa strain IE‐6, and a fungal antagonist, Pochonia chlamydosporia, were tested for their ability to inhibit mycelial growth of root‐infecting fungi under laboratory conditions including Macrophomina phaseolina, Fusarium oxysporum, F. solani and Rhizoctonia solani. Biocontrol effectiveness of the bacterium and the fungus alone or in combination was also determined for the control of root‐infecting fungi under field conditions. In a dual‐culture plate assay, the colonies of P. chlamydosporia and P. aeruginosa met each other and no further growth of either organism occurred. Against M. phaseolina, F. solani and R. solani, an ethyl acetate extract of the culture filtrates of P. aeruginosa inhibited fungal growth greater than the hexane extract, but against F. oxysporum the hexane extract caused greater inhibition of fungal growth. By contrast, against M. phaseolina, F. oxysporum and F. solani, the hexane extract of P. chlamydosporia was more effective in the inhibition of fungal growth than the ethyl acetate fraction. Ethyl acetate extracts of P. aeruginosa at 1.0 mg/ml not only inhibited the radial colony growth of R. solani but also lysed the fungal mycelium. P. aeruginosa produced siderophores and hydrogen cyanide under laboratory conditions. Field experiments conducted in 1997 and repeated in 1998 revealed that Pochonia chlamydosporia and P. aeruginosa significantly suppressed the root‐infecting fungi M. phaseolina, F. oxysporum, F. solani and R. solani and that the combination of the two caused greater inhibition of the fungal pathogens than either alone. Application of P. chlamydosporia and P. aeruginosa as a soil drench also resulted in enhanced growth of tomato plants.     

Trichoderma asperelloides antagonism to nine Sclerotinia sclerotiorum strains and biological control of white mold disease in soybean plants

Sclerotinia sclerotiorum is an important plant pathogen with worldwide distribution that causes severe economic losses of various agricultural crops such as soybean. This fungus is normally controlled with synthetic chemical fungicides that pose risks to the environment, and can be harmful to human health, and they can also induce resistance in pests. The aim of this study was to investigate the potential of Trichoderma asperelloides as a biocontrol agent towards white mold disease on soybeans crops. The antagonism of two strains of T. asperelloides (T25 and T42) isolated from soil samples was determined in-vitro by dual-culture confrontation testing on nine S. sclerotiorum strains obtained from sclerotia collected on diseased soybean plants. The mycelial growth and inhibition of carpogenic and ascospore germination by T. asperelloides extracts, as well as the efficacy of these on white mold control in soybeans were evaluated. Both strains of T. asperelloides exhibited high potential of antagonism. Methanolic and ethyl acetate extracts of the two T. asperelloides strains showed excellent growth inhibition (60–100%) on all of the pathogens tested. The ethyl acetate extracts of both T. asperelloides strains exhibited the highest efficacy against carpogenic germination, decreasing by 20–30% the number of ascospores per apothecium. Strains of T. asperelloides tested were more efficient in controlling white mold than two commercial products made from Trichoderma harzianum. The new strains of T. asperelloides have potential for successful biological control of white mold disease of soybean crops in the field.     

An ethyl acetate sensor utilizing cataluminescence on Y2O3 nanoparticles

A cataluminescence (CTL) sensor using Y₂O₃ nanoparticles as the sensing materials was proposed for the determination of ethyl acetate. This ethyl acetate sensor showed high sensitivity and specificity at the optimal temperature of 264°C. Quantitative analysis was performed at a wavelength of 425 nm. The linear ranges of CTL intensity vs ethyl acetate concentrations were 2.0–250 ppm (r = 0.9965) and 250–6500 ppm (r = 0.9997) with a detection limit (3σ) of 0.5 ppm. There was no response or weak response when foreign substances such as formic acid, n‐hexane, toluene, acetic acid, benzene, and formaldehyde passing through the surface of Y₂O₃ nanoparticles. The sensor had a long lifetime more than 80 h with 3600 ppm ethyl acetate. It had been applied successfully to determine ethyl acetate in artificial air samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Anti-fungal activity of essential oils of Ceylon Eucalyptus species for the control of Fusarium solani and Sclerotium rolfsii

The essential oils were extracted from the leaves of Eucalyptus microcorys, Eucalyptus grandis and Eucalyptus robusta which were grown in Sri Lanka and their major chemical compounds were determined. 1,8-Cineole and α-pinene were identified as major aroma compounds in these oils. In this study, the anti-fungal activity of essential oils of E. microcorys, E. grandis and E. robusta, ethanol extract of E. microcorys and 1,8-cineole were evaluated against Sclerotium rolfsii, a fungi responsible for leaf spot disease of indoor plants and Fusarium solani, a fungi responsible for dry rot diseases of potato by poisoned food technique, and minimum inhibitory concentrations (MICs) were determined. The essential oils from three Eucalyptus species showed significant inhibitory effect against S. rolfsii and F. solani than the ethanol extract of E. microcorys. Of treatments, the essential oil of E. grandis showed the best anti-fungal activity with the MIC values of less than 0.1% for S. rolfsii and 0.5% for F. solani. The MICs of the oils of E. microcorys and E. robusta were between 0.3–0.5% against S. rolfsii and 0.5–0.75% for F. solani. The 1,8-cineole did not exhibit inhibition activity as much of Eucalyptus essential oils and hence, it can be assumed that minor chemical components of the oils contribute to the growth inhibition of the tested fungi. This is the first report of anti-fungal activity of Sri Lankan oils of E. microcorys, E. grandis and E. robusta and ethanol extract of E. microcorys against S. rolfsii and F. solani. These findings would be useful for the designing of natural fungicide for agriculture- and food-based industries.     

Antifungal activity of several medicinal plants extracts against the early blight pathogen (Alternaria solani)

The antifungal activity for several medicinal plants against the early blight fungus (Alternaria solani) has been investigated. These plants were Syrian marjoram (Majorana syriaca), rosemary (Rosmarinus officinalis), Greek sage (Salvia fruticosa), roselle (Hibiscus sabdariffa) and cotton lavender (Santolina chamaecyparissus). The inhibitory effect of these extracts on the radial mycelial growth as well as on spore germination was measured in vitro at various concentrations of crude extract (0.5 g dry plant powder/ml medium). Extracts of M. syriaca and H. sabdariffa were most effective causing total inhibition of mycelial growth and spore germination at 8–10% concentration. Extract of R. officinalis also caused total inhibition of the above two parameters but at double the concentration (20%). Extracts of S. fructicosa and S. chamaecyparissus produced relatively moderate antifungal activity. At 25% concentration, these extracts showed an incomplete inhibition in mycelial growth being around 75–85% and 70–90%, respectively. However, at this same concentration both plant extracts produced total inhibition of spore germination. Results of this study indicated that both extracts of M. syriaca and H. sabdariffa were strong inhibitors of this fungus and to levels comparable to standard fungicides. Further studies are required to determine the effect of these extracts in vivo to evaluate their potential as natural treatments for this disease.     

Metabolic activities of the sugarbeet pathogens Fusarium solani (Mart.) Sacc. and Sclerotium rolfsii Sacc. under pyramin stress

Effects of different concentrations of active ingredient of the herbicide pyramin on metabolic activities of Fusarium solani and Sclerotium rolfsii were examined. High concentrations of this herbicide (1000 and 2000 g mL^-1 for F. solani and 100 and 200 g mL^-1 for S. rolfsii) had inhibitory effects on the metabolic activities of both fungi. These were demonstrated by significant decreases in growth, and increases in rates of CO₂ evolved, O₂ consumed and keto acids produced. These were accompanied by increased rates of sugar, nitrate and inorganic phosphorus absorption as well as lowered rates of synthesis of carbohydrates and insoluble nitrogenous (including protein) and phosphorus (including RNA-P and DNA-P) compounds. In addition, rates of excretion of both nitrogen and phosphorus fractions by the mycelial mats were increased.A concentration of 25 g mL^-1 exerted little or no effect on the metabolic activities of these fungi, although S. rolfsii was somewhat sensitive to this concentration.     

Pathogenic potential of root-knot nematode Meloidogyne incognita and root-rot fungus Fusarium solani on chilli (Capsicum annuum L.)

Damaging threshold levels of root-knot nematode Meloidogyne incognita and root-rot fungus Fusarium solani on plant growth parameters, viz., plant length, fresh and dry weight of chilli were determined by conducting their pathogenicity trials in pot experiments. The results revealed a significant reduction in the plant growth parameters at and above the inoculum level of about 1000?J₂ per plant of M. incognita and the highest reduction was recorded at 8000?J₂ per plant. Significant reduction in plant growth parameters was recorded at 1.00?g mycelial mat of F. solani per plant, while the highest reduction was observed at 8.00?g mycelial mat per plant. The damaging threshold level was 1000?J₂ per plant of M. incognita and 1.00?g mycelial mat of F. solani.