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1.
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.  相似文献   

2.
Understanding the environmental factors that influence the rhizosphere and inner root colonization of the disease‐suppressive strains of fluorescent pseudomonads is an essential step towards improving the level and reliability of their biocontrol activity. Soil amendment with Zn at 0.8 or 1.6 mg/kg of soil alone or in combination with Pseudomonas aeruginosa IE‐6S+significantly reduced nematode penetration in tomato roots. Zn applied alone did not reduce root infection caused by Macrophomina phaseolina or Fusarium solani but did reduce when used in combination with IE‐6S+. Soil amendment with Zn at 0.8 or 1.6 mg/kg of soil alone or in conjunction with IE‐6S+ markedly suppressed Rhizoctonia solani infection. Plant height, fresh weight of shoot and protein contents of the leaves substantially improved when used with Zn, however, plants growing in the soil treated with 1.6 mg/kg of Zn in the absence of IE‐6S+ not only reduced plant growth but also showed necrotic symptoms on the leaves. Zn application in the soil decreased populations of IE‐6S+ both in the rhizosphere and root. A positive correlation between bacterial rhizosphere and inner root colonization was also observed. With an increase in nematode densities in the soil, nematode penetration and subsequent galling due to Meloidogyne javanica increased. Regardless of the nematode densities, Zn applied alone or in combination with IE‐6S+ caused marked suppression of M. javanica. At all the population densities of M. javanica, Zn enhanced the efficacy of IE‐6S+ to reduce nematode invasion and subsequent gall development. IE‐6S+ caused significant suppression of soil‐borne root‐infecting fungi both in Zn‐sufficient and Zn‐deficient soil although this suppressive effect accentuated in Zn‐sufficient soils. In the absence of IE‐6S+ and/or Zn, increased nematode densities in the soil significantly reduced plant height, fresh weight of shoot and protein contents of the shoots. With an increase in nematode densities, populations of IE‐6S+ in the rhizosphere and root increased regardless of the Zn application. However, Zn‐deficient soils supported larger populations of IE‐6S+ compared with those of Zn‐sufficient soils.  相似文献   

3.
Argemone mexicana L. is a widely used plant in Mexican traditional medicine to treat inflammatory and nervous medical conditions. It has been subjected to several pharmacological and chemical studies in which acute anti-inflammatory activity is indicated. This work aimed at finding an extract and fraction with anti-inflammatory activity by means of 2-O-tetradecanoylphorbol-13-acetate (TPA)-induced auricular edema. Afterward, the extract and the fraction were tested on neuroinflammation caused by lipopolysaccharides (LPS). Treatments obtained from A. mexicana included the methanolic extract (AmMeOH), a fraction extracted with ethyl acetate (AmAcOEt), and four sub-fractions (AmF-1 to AmF-4), which were evaluated in auricular edema with the TPA assay. Both treatments with the most significant inhibitory effect were employed to test these in the LPS neuroinflammation model. AmAcOEt and AmF-3 induced a higher inhibition of edema (%), and both diminished ear inflammation when viewed under a microscope. These treatments also raised an increase in spleen, but not in brain of mice with neuroinflammation. They were able to decrease the concentration of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) in both organs. Furthermore, the accumulation of amyloid-β (Aβ) in hippocampus was not visible. AmF-3 contains the flavonoids isoquercetin, luteolin, and rutin, the former being the most concentrated.  相似文献   

4.
The anti-fungal activity of a mixture of quaternary alkaloids of Argemone mexicana was observed at different concentrations (1000, 2000, 3000, 4000 and 5000 μl/ml) against 10 fungi, viz., Ustilago cynodontis, Cercospora cajani, Sphaerotheca sp., Cercospora sp., Alternaria solani, Bipolaris sp., Helminthosporium sp., Curvularia sp., Fusarium udum and Alternaria cajani. Spore germination was inhibited at 2000, 3000, 4000, 5000 μg/ml. Analysis of phenolics by high performance liquid chromatography (HPLC) recorded 11 peaks in the alkaloids but only three could be identified, viz., tannic, caffeic and ferulic acids. The significant efficacy of the alkaloid under in vitro conditions may open the possibility of its use by farmers under field conditions for controlling some crop diseases.  相似文献   

5.
The isomeric alkaloids jatrorrhizine and columbamine isolated from the whole plant of Argemone mexicana were assessed against spore germination of some fungi, e.g. Alternaria cajani, Bipolaris sp., Helminthosporium sp., Fusarium udum and Curvularia sp. Both the alkaloids were effective against most of the fungi tested. Jatrorrhizine was highly effective against spore germination of Bipolaris sp., Fusarium udum and Curvularia sp. at 5000 ppm concentration, whereas columbamine was highly effective against Alternaria cajani, Helminthosporium sp. and Fusarium udum at 5000 ppm.  相似文献   

6.
V. Sultana    J. Ara    S. Ehteshamul-Haque   《Journal of Phytopathology》2008,156(7-8):390-395
Solvent fractions (i.e. n -hexane, chloroform and methanol) of the ethanol extracts of the seaweeds Codium iyengarii , Jania capillacea , Stokeyia indica and Solieria robusta caused more than 50% mortality of Meloidogyne javanica juveniles within 24 h at 10 mg/ml. Nematode mortality increased with an increase in fraction concentration or exposure time. The n -hexane fractions from S. indica , J . capillacea and C . iyengarii and the chloroform fraction from S . robusta also resulted in more than 50% mortality within 48 h at 1.0 mg/ml. In a screen-house experiment application of S . indica and S . robusta as soil amendments alone or with Pseudomonas aeruginosa , a plant growth promoting rhizobacterium (PGPR), significantly suppressed infection of chili roots by root-infecting fungi Macrophomina phaseolina , Rhizoctonia solani , Fusarium solani and the root knot nematode Meloidogyne javanica . Seaweed alone or with PGPR also increased plant growth. Suppressive effect on root pathogens and growth enhancement potential of seaweeds and P . aeruginosa were also effective in field plots.  相似文献   

7.
Ethidium bromide, (0.1% solution in ethanol-water, 1:3, v/v) was used to stain nuclei in mycelia and spores of different fungi. Nuclei looked bright brick red under green excitation. This method is very efficient, specific, reproducible and cost-effective.  相似文献   

8.
Fusarium and Rhizoctonia genera are important pathogens of many field crops worldwide. They are constantly evolving and expanding their host range. Selecting resistant cultivars is an effective strategy to break their infection cycles. To this end, we screened a collection of Medicago truncatula accessions against Fusarium oxysporum, Fusarium solani, and Rhizoctonia solani strains isolated from different plant species. Despite the small collection, a biodiversity in the disease response of M. truncatula accessions ranging from resistant phenotypes to highly susceptible ones was observed. A17 showed relative resistance to all fungal strains with the lowest disease incidence and ratings while TN1.11 was among the susceptible accessions. As an initiation of the characterization of resistance mechanisms, the antioxidant enzymes’ activities, at the early stages of infections, were compared between these contrasting accessions. Our results showed an increment of the antioxidant activities within A17 plants in leaves and roots. We also analyzed the responses of a population of recombinant inbred lines derived from the crossing of A17 and TN1.11 to the infection with the same fungal strains. The broad-sense heritability of measured traits ranged from 0.87 to 0.95, from 0.72 to 0.96, and from 0.14 to 0.85 under control, F. oxysporum, and R. solani conditions, respectively. This high estimated heritability underlines the importance of further molecular analysis of the observed resistance to identify selection markers that could be incorporated into a breeding program and thus improving soil-borne pathogens resistance in crops.  相似文献   

9.
Thirty-two isolates of Pseudomonas aeruginosa and a Bacillus subtilis strain were isolated from rhizosphere and rhizoplane of four wild and 15 cultivated plants. Biocontrol and growth-promoting potentials of the bacterial isolates were tested under laboratory, greenhouse and field conditions. The bacterial isolates not only exhibited nematicidal activity by killing the second stage larvae of Meloidogyne javanica to a varying degree but also produced inhibition zones by inhibiting the radial growth of Macrophomina phaseolina, Fusarium solani and Rhizoctonia solani . Strain IE-2 and IE-6 of P. aeruginosa also lysed the fungal mycelium. P. aeruginosa and B. subtilis used as seed dressing or as soil drench significantly suppressed root rot–root knot infection and nematode population densities under greenhouse and field conditions and thereby enhanced plant growth and yield in mungbean.  相似文献   

10.
A stepwise screening strategy made it possible to identify five new Bacillus spp. strains for biocontrol of Rhizoctonia solani, Sclerotinia minor and Fusarium solani. In vitro and in vivo biocontrol activity and M13-PCR DNA-fingerprinting led to the selection of these valuable biological control agents (BCAs) from a wide collection of over 250 candidates. At the end of this selection, the highest potential antagonists were identified at species level by 16S-rRNA gene sequence analysis, and results assigned them to Bacillus subtilis group as Bacillus amyloliquefaciens- and Bacillus methylotrophicus-related strains. In the current study, spore-forming bacteria provided substantial biocontrol of telluric diseases on cress and other different host plants. The strains named 15S and 09C were effective in disease control on Brassica oleracea/R. solani pathosystem, whereas Sclerotinia drop of lettuce was reduced by treatments with the strains 17S and 08C. Finally, the strains 17S and 12S were equally effective to control potato Fusarium rot. The evident zone of inhibition seen in dual culture plates suggested antibiosis-like antagonisms as the main mechanisms used by these bacterial isolates in interaction with the pathogens. Additionally, the API-ZYM method revealed constitutive activity of certain extracellular enzymes that could be involved in plant fortification. Bacillus strains isolated from compost and compost-amended soils are promising BCAs that have potential for practical application as biofungicides.  相似文献   

11.
Non-pathogenic soil bacteria living in association with roots of higher plants enhance their adaptive potential and thus could be beneficial for their growth. Here, we present the current status of the use of Bacillus subtilis in biocontrol. Rhizobacteria are found in the rhizosphere. Plant growth promoting rhizobacteria (PGPR) strains, such as Bacillus and Pseudomonas, were isolated by using Nutreint dextrose Agar medium or Potato Dextrose Agar medium. The selection of PGPR strains was done by duel culture methods against the potato pathogens. The interaction of PGPR (Bacillus) with potato seeds or vegetative parts show promising antagonism by virtue of producing siderophore and antibiotics against black scurf and stem canker diseases of potato caused by Rhizoctonia solani, thereby resulting in increase of potato yield. The effectiveness of PGPR strain (Bacillus spp.) in improving the yield of potato in greenhouse conditions and in the field was observed.  相似文献   

12.
Formation of the methylenedioxy bridge is an integral step in the biosynthesis of benzo[c]phenanthridine and protoberberine alkaloids in the Papaveraceae family of plants. This reaction in plants is catalyzed by cytochrome P450-dependent enzymes. Two cDNAs that encode cytochrome P450 enzymes belonging to the CYP719 family were identified upon interrogation of an EST dataset prepared from 2-month-old plantlets of the Mexican prickly poppy Argemone mexicana that accumulated the benzo[c]phenanthridine alkaloid sanguinarine and the protoberberine alkaloid berberine. CYP719A13 and CYP719A14 are 58% identical to each other and 77% and 60% identical, respectively, to stylopine synthase CYP719A2 of benzo[c]phenanthridine biosynthesis in Eschscholzia californica. Functional heterologous expression of CYP719A14 and CYP719A13 in Spodoptera frugiperda Sf9 cells produced recombinant enzymes that catalyzed the formation of the methylenedioxy bridge of (S)-cheilanthifoline from (S)-scoulerine and of (S)-stylopine from (S)-cheilanthifoline, respectively. Twenty-seven potential substrates were tested with each enzyme. Whereas CYP719A14 transformed only (S)-scoulerine to (S)-cheilanthifoline (Km 1.9 ± 0.3; kcat/Km 1.7), CYP719A13 converted (S)-tetrahydrocolumbamine to (S)-canadine (Km 2.7 ± 1.3; kcat/Km 12.8), (S)-cheilanthifoline to (S)-stylopine (Km 5.2 ± 3.0; kcat/Km 2.6) and (S)-scoulerine to (S)-nandinine (Km 8.1 ± 1.9; kcat/Km 0.7). These results indicate that although CYP719A14 participates in only sanguinarine biosynthesis, CYP719A13 can be involved in both sanguinarine and berberine formation in A. mexicana.  相似文献   

13.
The necrotrophic fungus Thanatephorus cucumeris (anamorph Rhizoctonia solani) is among the most important soil‐borne pathogens which causes tomato foot and root rot worldwide. We investigated virulence and genetic relationships among and within different taxonomic groups of R. solani from the tomato‐growing regions in the north‐east of Iran. Characterization of R. solani taxonomic groups revealed that, of 56 isolates, four were AG‐2‐1, 16 were AG‐3 PT, 21 were AG‐4 HG‐I and 15 were AG‐4 HG‐II. Because interprimer binding site (iPBS), which is based on amplification of retrotransposons, is known as novel and powerful DNA fingerprinting technology, we selected four iPBS primers, which can detect polymorphisms of tomato foot root and root rot pathogen, for investigating genotypic variability of the isolates. The iPBS analyses separated various taxonomic groups of R. solani and showed great diversity among the isolates, demonstrating that the R. solani isolates obtained from tomato were not a clonal population. Crop rotation strategies and geographic location seem to be important factors affecting genetic structure of the isolates. Pathogenicity tests on tomato cultivar ‘Mobil’ showed significant differences in the virulence of various isolates. The overall results indicated that isolates of AG‐3 and AG‐4 were more virulent than AG‐2‐1. There was no significant correlation between genetic diversity and virulence of the isolates. This is the first report of R. solani AG‐4 HG‐II, causing tomato foot and root rot. Also, our research is the first in assessment of genetic diversity in fungal populations using iPBS molecular markers.  相似文献   

14.
Glomus mosseae and the two pod rot pathogens Fusarium solani and Rhizoctonia solani and subsequent effects on growth and yield of peanut (Arachis hypogaea L.) plants were investigated in a greenhouse over a 5-month period. At plant maturity, inoculation with F. solani and/or R. solani significantly reduced shoot and root dry weights, pegs and pod number and seed weight of peanut plants. In contrast, the growth response and biomass of peanut plants inoculated with G. mosseae was significantly higher than that of non-mycorrhizal plants, both in the presence and absence of the pathogens. Plants inoculated with G. mosseae had a lower incidence of root rot, decayed pods, and death than non-mycorrhizal ones. The pathogens either alone or in combination reduced root colonization by the mycorrhizal fungus. Propagule numbers of each pathogen isolated from pod shell, seed, carpophore, lower stem and root were significantly lower in mycorrhizal plants than in the non-mycorrhizal plants. Thus, G. mosseae protected peanut plants from infection by pod rot fungal pathogens. Accepted: 10 February 2000  相似文献   

15.
A root rot and wilt disease of Anigozanthos manglesii (Kangaroo Paw) grown in greenhouses in Israel, for exporting as cut flowers to Europe, was characterized. Pythium myriotylum (Drechs.) and Rhizoctonia solani (Kühn) were the prevalent pathogens in diseased plants collected from commercial greenhouses. Fusarium oxysporum, Fusarium spp. and Myrothecium sp. were also isolated, but P. myriotylum or R. solani were not detected in samples from symptomless plants in tissue cultures (Australian origin) or plants at different stages in the nursery; non‐pathogenic F. oxysporum and Fusarium spp. were detected in several samples. In pathogenicity tests carried out in pots, plant mortality occurred 7 days after inoculation with P. myriotylum. In a field experiment carried out in methyl bromide‐fumigated soil, the incidence of dead plants following inoculation with P. myriotylum alone was 22% 10 days after inoculation, increasing to 78% after an additional 25 days. The incidence of dead plants following inoculation with R. solani alone was only 5% and in plants inoculated simultaneously with both pathogens, disease incidence was 88% 35 days after inoculation. Mortality reached 90–100% in plants inoculated with P. myriotylum, either singly or combined with R. solani 60 days after inoculation, whereas in plants inoculated with R. solani it was 5%. The maximum mortality in plants inoculated with R. solani was 25%, 76 days after inoculation. These results clearly demonstrate that P. myriotylum was the dominant pathogen in the root rot and wilt of A. manglesii.  相似文献   

16.
The antifungal potentialities of three endophytic bacterial strains, Stenotrophomonas maltophila H8 (Xanthomonadales: Xanthomonadaceae), Pseudomonas aeruginosa H40 (Pseudomonadales: Pseudomonadaceae) and Bacillus subtilis H18 (Bacillales: Bacillaceae) were evaluated against the phytopathogenic fungus Rhizoctonia solani in cotton seedlings under greenhouse conditions. The bacterial strains were applied as a soil drench or talc-based bioformulation in R. solani-infested soil and non-infested soil. Results indicated that the soil drench treatment was more efficient than talc-based bioformulation. A significant increase of seed emergence and seedling survival with a clear reduction of disease severity was achieved with the endophytic bacterial treatments. At the same time, the fresh weight, dry weight, shoot length and root length of the treated plants were markedly enhanced. Moreover, there was an apparent induction of the antioxidant enzymes (peroxidase, polyphenol oxidase and catalase) of the treated seedlings. Gas chromatography–mass spectrometry revealed the presence of various bioactive compounds in the bacterial supernatant. The antagonistic activity of the bacterial strains against R. solani was attributed to their capability to produce a broad spectrum of antifungal compounds in addition to bioactive molecules that can trigger the systemic resistance in the infected seedlings.  相似文献   

17.
The individual and synergistic potentials of two Streptomyces strains and compost for growth promotion and biocontrol against dumping off caused by Rhizoctonia solani on pepper were evaluated. Results showed that the compost can greatly enhance pepper growth while the combination of the two strains and compost was most efficient for the disease suppression.  相似文献   

18.
In the present study, the effects of the arbuscular mycorrhizal fungus (AMF) Glomus intraradices Schenck & Smith and four rhizobacteria (RB; 58/1 and D/2: Pseudomonas fluorescens biovar II; 17: P. putida; 21: Enterobacter cloacae), which are the important members of the rhizosphere microflora and biological control agents against plant diseases, were examined in the pathosystem of Fusarium oxysporum f. sp. lycopersici [(Sacc) Syd. et Hans] (FOL) and tomato with respect to morphological parameters (fresh and dry root weight) and phosphorous (P) concentration in the roots. Treatments with single and dual inoculation with G. intraradices and RB strains reduced disease severity by 8.6–58.6%. Individual bacteria inoculations were more effective than both the single AMF and dual (G. intraradices + RB) inoculations. In addition, the RB and G. intraradices enhanced dry root weight effectively. Significant increases in root weights were recorded particularly in the triple inoculations compared with single or dual inoculations. Compared with the non‐treated controls all biological control agents increased P‐content of treated roots of plants. Colonization with RB increased especially in triple (FOL + G. intraradices + RB) inoculations whereas colonization of G. intraradices was significantly decreased in treatment of FOL + G. intraradices compared with triple inoculations. The results suggest that suitable combinations of these biocontrol agents may ameliorate plant growth and health.  相似文献   

19.
Soil-borne diseases are the major problems in mono cropping. A mixture (designated LTM-m) composed of agricultural wastes and a beneficial microorganism Streptomyces saraceticus SS31 was used as soil amendments to evaluate its efficacy for managing Rhizoctonia solani and root knot nematode (Meloidogyne incognita). In vitro antagonistic assays revealed that SS31 spore suspensions and culture broths effectively suppressed the growth of R. solani, reduced nematode egg hatching, and increased juvenile mortality. Assays using two Petri dishes revealed that LTM-m produced volatile compounds to inhibit the growth of R. solani and cause mortality to the root knot nematode eggs and juveniles. Pot and greenhouse tests showed that application of 0.08% LTM-m could achieve a great reduction of both diseases and significantly increase plant fresh weight. Greenhouse trials revealed that application of LTM-m could change soil properties, including soil pH value, electric conductivity, and soil organic matter. Our results indicate that application of LTM-m bio-organic amendments could effectively manage soil-borne pathogens.  相似文献   

20.
Fusarium oxysporum f. sp. lycopersici (Fol) and Fusarium oxysporum f. sp. cubense (Foc), are the causal agent of Fusarium wilt disease of tomato and banana, respectively, and cause significant yield losses worldwide. A cost-effective measure, such as biological control agents, was used as an alternative method to control these pathogens. Therefore, in this study, six isolates of the Streptomyces-like colony were isolated from soils and their antagonistic activity against phytopathogenic fungi and plant growth-promoting (PGP) activity were assessed. The results showed that these isolates could inhibit the mycelial growth of Fol and Foc. Among them, isolate STRM304 showed the highest percentage of mycelial growth reduction and broad-spectrum antagonistic activity against all tested fungi. In the pot experiment study, the culture filtrate of isolates STRM103 and STRM104 significantly decreased disease severity and symptoms in Fol inoculated plants. Similarly, the culture filtrate of the STRM304 isolate significantly reduced the severity of the disease and symptoms of the disease in Foc inoculated plants. The PGP activity test presents PGP activities, such as indole acetic acid production, phosphate solubilization, starch hydrolysis, lignin hydrolysis, and cellulase activity. Interestingly, the application of the culture filtrate from all isolates increased the percentage of tomato seed germination and stimulated the growth of tomato plants and banana seedlings, increasing the elongation of the shoot and the root and shoot and root weight compared to the control treatment. Therefore, the isolate STRM103 and STRM104, and STRM304 could be used as biocontrol and PGP agents for tomato and banana, respectively, in sustainable agriculture.  相似文献   

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