In vitro and in vivo antifungal properties of silver nanoparticles against Rhizoctonia solani, a common agent of rice sheath blight disease

Sheath blight disease in rice has caused major crop losses worldwide. Managing the causal agent of disease Rhizoctonia solani Kühn is difficult because of its broad host range and formation of sclerotia which can survive in harsh environmental conditions; therefore developing innovative disease management methods without application of hazardous chemicals has been considered as the main concern to maintain sustainable agriculture. This presented research has revealed the negative impact of Silver nanoparticles (SNPs) on R. solani and disease progress both in vitro and in vivo. The adverse effects of the SNPs on R. solani are significantly dependent on the quantity of SNPs, sprayed at different concentrations in vitro. The highest inhibition level against sclerotia formation and mycelia growth are 92 and 85%, respectively, at a SNPs concentration of 50 ppm. In vivo glasshouse experiments also showed that SNPs at the same concentration favorably affects both the fresh and dry weight of rice plants with a remarkable suppressive effect on the lesion development in leaves

Chitinolytic and microsclerostatic activity of iranian strains of streptomyces plicatus and Frankia sp. on Olive Isolate of verticillium dahliae

Among soil-borne fungi, cosmopolitan phytopathogen, Verticillium dahliae Klebahn is responsible for high yield losses in many plant species. Except for solarization in mediterranean countries and except in the few cases where disease-resistant cultivais are available, control of Verticillium wilt in commercial crops has been highly dependent on the application of preplant soil fumigants. Research to develop alternative control measurements should focus on biological approaches aimed at shifting the composition of soil microbial communities to suppress Verticillium. The merits of role of actinomycetes in biological control of soil-borne fungal-pathogens are known, however actinomycetes micioflora of the Iranian soils has not been very well explored in searching for biofungicide agents. At the present research, in vitro studies of some biological effects of two Iranian strains of actinomycetes, Streptomyces plicatus strain 101 and Frankia sp. strain 103, are presented. Both strains revealed enzymatic activity and inhibited production of microscleiotia in V. dahliae. Treating the crude extract with chloroform, denaturized enzymatic activity of both strains. Thermal inactivation point of active phases of S. plicatus was 70 and 90°C and in Frankia sp. was determined as 60°C. Antifungal active phases of S. plicatus tolerate wide range of pH (5-13) but in Frankia sp. active phase tolerates pH 7-9. These two strains may be useful candidates for involving in integrated control programs of Verticillium vascular wilting

Antifungal characterization of actinomycetes isolated from Kerman, Iran and their future prospects in biological control strategies in greenhouse and field conditions

Antifungal actinomycete strains were assayed for antagonistic activity against Verticillium dahliae, Alternaria solani, Fusarium solani and Geotrichum candidum, four worldwide phytopathogenic fungi. For better evaluation of the spectral activity of the isolated Actinomycetes, two yeasts, Saccharomyces cerevisiae and Candida albicans were also included in the survey. From 110 soil inhabitant strains that have been isolated from soil samples of Kerman province, southeast of Iran, 10 strains showed antifungal activities as determined through screening and bioassays by agar disk and well-diffusion methods. Active strains that have broad spectrum of antifungal activity were grown in submerged cultures and active crude was prepared upon which some preliminary characterizations conducted

First report of antifungal properties of a new strain of Streptomyces plicatus (Strain101) against four Iranian phytopathogenic isolates of Verticillium dahliae, a new horizon in biocontrol agents

This is the first report on antifungal activity of a new strain of Streptomyces plicatus (strain101) against four Iranian phytopathogenic isolates of Verticillium dahliae. In the recent decades, biological control of plant diseases has received more attention mainly as a response to public concern about the use of hazardous chemicals in the environment. Soil Actinomycetes particularly Streptomyces spp. enhance soil fertility and have antagonistic activity against wide range of soil-borne plant pathogens. In search for metabolites of soil Actinomycetes having antifungal activity against four isolates of the cosmopolitan pathogen, Verticillium dahliae Klebahn, 110 isolates were screened. Among all, strain101 that was identified as a new strain of S. plicatus, showed high level of activity in Agar disk and Well-diffusion methods. S. plicatus was propagated in submerged cultures and active crude was prepared upon which some biological characterizations performed. The active metabolite (s) is polar, soluble in H2O and methanol but insoluble in chloroform, dichloromethane or hexane. Antifungal activity composed of two types, mycelial inhibition, inhibition of microsclerotia and melanin production. Antifungal gene from S. plicatus Strain 101 may be a useful candidate for genetic engineering of agriculturally important crop plants for increased tolerance against V. dahliae

Antibacterial and antifungal survey in plants used in indigenous herbal-medicine of south east regions of Iran

Methanol plant-extracts of 221 species from 98 families which had documented uses in Iranian herbal-medicine were screened for antibacterial and antifungal activity against 11 standard bacterial strains and 3 fungal species at 20 mg mlG1. Eighty one samples in 39 families showed antibacterial and/or antifungal activity against at least on one of the tested microorganisms. Antimicrobial activities were evaluated by measuring the diameter of inhibition zones in agar well diffusion method. Dianthus coryophyllus was active against all tested G-ve and G+ve bacteria except Micrococcus luteus. Most susceptible G-ve bacteria were Klebsiella pneumoniae and Bordetella bronchiseptica and least susceptible was Escherichia coli. In G+ve bacteria, most and least susceptible were Staphylococcus aureus and Micrococcus luteus, respectively. Plants with high antifungal activity included Alpinia officinarum, Chrozophora verbasafalia, Cinnamomum zeylanicum, Dianthus coryophyllus, Helleborus nigra, Heracleum persicum, Myrtus communis, Terminalia chebula and Trachysermum copticum which were effective mostly against Candida albicans and C. utilis

Building microbial fuel cells, structure and components

Production of electricity by microorganisms is a new interesting subject which has received high attention by researchers, industries and NASA. In Microbial fuel cells (MFC) electricity is generated via microbial activities. It is proposed that waste materials as sewage, food leftovers and basically all sorts of biodegradable organic matters have the capability to be used in MFC. These devices are harmless to the environment. Basically wide range of bacteria can be used as candidates in MFC. Basic structure, mechanism of action, types of microorganisms and chemical reactions are discussed in this paper

Biological control potential of two Streptomyces isolates on Rhizoctonia solani, the causal agent of damping-off of sugar beet

Biological control of sugar beet damping-off of Rhizoctonia solani by two Streptomyces isolates (S2 and C) was evaluated in this study. The in vitro antagonism assays showed that active isolates had inhibitory effects on mycelium growth of the three R. solani AG-4 isolates (Rs1, Rs2 and Rs3). Soil treatment either with isolate S2 or C formulation inhibited the disease completely and increased seedling stand in infected and uninfected treatments significantly (p<0.05). Compared to controls, all treatments containing bacteria had enhanced shoot and root dry weight and root density. Both bacterial isolates maintained normal growth in pH ranges of 5.6, 7.2 and 8.0 at 29°C. Isolate C grew in pH ranges 5.6, 7.2 and 8.0 at 23-37°C, isolate S2 grew at 18-37°C in pH 5.6-8.0 but did not grow in acidic medium at 37°C. When pH decreased to 5.0, growth of C decreased and S2 inhibited. To elucidate the mode of antagonism, chitinase activity and siderophore production were evaluated. Both isolates showed chitinase activity on medium containing colloidal chitin. Biosynthesis of siderophore was detectable in isolate C but not in S2. The results of this study showed that these isolates had antifungal activities by production of siderophore and chitinase

First report of antifungal spectra of activity of Iranian actinomycetes strains against Alternaria solani, Alternaria alternate, Fusarium solani, Phytophthora megasperma, Verticillium dahliae and Saccharomyces cerevisiae

This is the first report of antifungal activity of Iranian Actinomycetes isolates against Alternaria solani Sorauer, Alternaria alternata (Fr.) Keissler, Fusarium solani (Mart.) Sacc., Phytophthora megasperma Drechsler, Verticillium dahliae Klebahn and Saccharomyces cerevisiae Meyen ex Hansen. Biological control of plant diseases has received worldwide attention in recent years mainly as a response to public concern about the use of hazardous chemicals in the environment. Soil Actinomycetes particularly Streptomyces spp. enhance soil fertility and have antagonistic activity against wide range of soil-borne plant pathogens. In search for soil Actinomycetes having antifungal activity against plant fungal-pathogens, 110 isolates were screened from which 14 isolates were found active at least against one of the tested fungi. Streptomyces plicatus strain101, Frankia sp. strain 103 and Streptomyces sp. strain 44 had the widest antifungal spectra of activity. Antifungal genes from these strains may be proper candidates for genetic engineering of plants for increased tolerance against the tested cosmopolitan fungal pathogens