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1.
Summary Biological control visualizes a control of disease with the help of living organisms. In case of root disease, organisms occur in soil which suppress the activity of disease fungi. In the present investigation antagonists have been isolated and used in the control of root rot and wilt disease ofLens culinaris caused byS. rolfsii andF. oxysporum respectively.Isolation of antagonistic micro-organisms were done from the rhizosphere soil of Bombay 20 and local varieties and from field soil. Antagonists were screened against certain test organisms and pathogens. The selected antagonists were used for the control of the diseases of lentil crop by inoculating the antagonists in the soil and thereby to see the effect of decreased plant disease in sterilized and unsterilized soil.Amendments in the form of different organic materials were also given to control the diseases in natural soil.The most effective results were obtained withT. viride, Streptomyces gougeroti Streptomyces species 12 and 13, bacterial isolates no. 16 and 18 in case ofF. oxysporum f.lentis inoculated pots, where there was no disease. In case ofS. rolfsii inoculated pots not a single antagonist was able to eradicate the disease completely.Portion of the Ph. D. thesis accepted by the University of Saugor, Sagar, India.  相似文献   

2.
The effect of crop rotation and monocropping on the occurrence of bacteria with antagonistic activity toward Pythium debaryanum and Fusarium oxysporum was shown. Arthrobacter spp., fluorescent Pseudomonas spp. and actinomycetes were isolated from winter rape, sugar beet and winter barley rhizosphere and bulk soil from the plots of a long-term crop rotation experiment (18 years). The occurrence of mycoantagonistic isolates and their antibiosis level exhibited specificity for the site, crop and crop rotation. Mycoantagonistic activity was common among actinomycetes and fluorescent Pseudomonas spp. and less frequent among Arthrobacter spp. Antibiosis of fluorescent Pseudomonas spp. and Arthrobacter spp. was in general stronger against P. debaryanum than F. oxysporum. The highest percentage of antagonistic Pseudomonas spp. against P. debaryanum was in the plots of barley crop, while plots of winter rape showed higher frequency of antagonists against F. oxysporum. The highest antibiosis activity of Arthrobacter spp. against both pathogens occurred in isolates from barley and winter rape monoculture, and there were no F. oxysporum antagonists among these bacteria in sugar beet monoculture. Most of actinomycete isolates strongly inhibited growth of P. debaryanum and F. oxysporum. The percentage of mycoantagonistic actinomycetes and their antibiosis level were the highest in the 6-year crop rotation system.  相似文献   

3.
The aim of this study was to isolate and screen actinomycetes from solitary wasp and swallow bird mud nests for antimicrobial activity. The actinomycetes were isolated from soil of nests of solitary wasp and swallow bird, and identified on the basis of morphological characteristics and molecular biological methods. A total of 109 actinomycetal isolates were obtained from 12 soil samples (6 from each habitat) using two media. The highest number of actinomycetes were recovered on Humic acid vitamin agar media (65.13%, n = 71) as compared to actinomycetes isolation agar media (34.86%, n = 38). The antimicrobial activity of actinomycetes isolates was determined using the agar plug method. Among 109 isolates, 51 isolates (46.78%) showed antibacterial activity by agar plug assay. The morphological and molecular characteristics confirmed that the most of active isolates in both sample belonged to the genus Streptomyces, the other potential genera like Streptosporangium, Actinomadura, Saccharopolyspora, Thermoactinomycetes and Nocardia were also recovered, but in a low frequency. The isolates designated as 8(1)*, BN-6, MN 2(6), MN 2(7) and MN 9(V) showed most promising activity against various drug resistant bacterial pathogens. It seems that the promising isolates from these unusual/unexplored habitats may prove to be an important step in development of drug for treating multi-drug resistant bacterial pathogens.  相似文献   

4.
A total of 288 marine samples were collected from different locations of the Bay of Bengal starting from Pulicat lake to Kanyakumari, and 208 isolates of marine actinomycetes were isolated using starch casein agar medium. The growth pattern, mycelial coloration, production of exopolysaccharides and diffusible pigment and abundance of Streptomyces spp. were documented. Among marine actinomycetes, Streptomyces spp. were present in large proportion (88%). Among 208 marine actinomycetes, 111 isolates exhibited antimicrobial activity against human pathogens, and 151 showed antifungal activity against two plant pathogens. Among 208 isolates, 183, 157, 116, 72 and 68 isolates produced lipase, caseinase, gelatinase, cellulase and amylase, respectively. The results of diversity, antimicrobial activity and enzymes production have increased the scope of finding industrially important marine actinomycetes from the Bay of Bengal and these organisms could be vital sources for the discovery of industrially useful molecules/enzymes.  相似文献   

5.
By use of selective media, 267 actinomycete strains were isolated from four rhizosphere-associated and four non-rhizosphere-associated British soils. Organic media with low nutrient concentrations were found to be best for isolating diverse actinomycetes while avoiding contamination and overgrowth of isolation media by eubacteria and fungi. While all isolates grew well at pHs 6.5 to 8.0, a few were unable to grow at pH 6.0 and a significant number failed to grow at pH 5.5. Eighty-two selected isolates were screened for in vitro antagonism towards Pythium ultimum by use of a Difco cornmeal agar assay procedure. Five isolates were very strong antagonists of the fungus, four were strong antagonists, and ten others were weakly antagonistic. The remaining isolates showed no antagonism by this assay. Additional studies showed that several of the P. ultimum antagonists also strongly inhibited growth of other root-pathogenic fungi. Twelve isolates showing antifungal activity in the in vitro assay were also tested for their effects on the germination and short-term growth of lettuce plants in glasshouse pot studies in the absence of pathogens. None of the actinomycetes prevented seed germination, although half of the isolates retarded seed germination and outgrowth of the plants by 1 to 3 days. During 18-day growth experiments, biomass yields of some actinomycete-inoculated plants were reduced in comparison with untreated control plants, although all plants appeared healthy and well rooted. None of the actinomycetes significantly enhanced plant growth over these short-term experiments. For some, but not all, actinomycetes, some correlations between delayed seed germination and reduced 18-day plant biomass yields were seen. For others, plant biomass yields were not reduced despite an actinomycete-associated delay in seed germination and plant outgrowth. Preliminary glasshouse experiments indicated that some of the actinomycetes protect germinating lettuce seeds against damping-off caused by P. ultimum.  相似文献   

6.
Compost suppression of soil-borne diseases in horticultural crops has been attributed to the activities of antagonistic microorganisms. A great diversity of microorganisms, capable of suppressing pathogens naturally colonize compost. A large number of microbes appeared in microbiological analyses of grape marc compost. Most microorganisms were bacteria. Average percentages were 31% mesophilic and 28% thermophylic bacteria, 16% mesophilic actinomycetes and 20% thermophylic actinomycetes. Only a few mould and yeast morphologies were obtained, 4% and 1% respectively. Antagonist in vitro assays were performed with 432 microbial morphologies isolated from grape marc compost. The microbes isolated were extremely effective antagonists in in vitro assays against all the fungal pathogens tested. Seven microorganisms were selected for further bioassay with Rhizoctonia solani in radish, Fusarium oxysporum f. sp. radicis-cucumerinum in melon, and Phytophthora parasitica in tomato and two microorganisms with Pythium aphanidermatum in cucumber. Those experiments indicate that grape marc compost reduces the severity of Pythium damping-off in cucumber, but does not reduce the severity of Phytophthora root rot in tomato, Fusarium oxysporum f. sp. radicis-cucumerinum in melon and Rhizoctonia solani in radish. Better suppressive effects were not demonstrated by either compost or vermiculite amended with microbes selected from grape marc compost.  相似文献   

7.
Abstract

Among the seven fungal (Gliocladium virens, Trichoderma hamatum, T. harzianum, T. koningii, T. longibrachiatum, T. pseudokoningii and T. viride) and two bacterial (Bacillus subtilis and Pseudomonas fluorescens) antagonists screened against C. gloeosporioides under in vitro conditions, T. harzianum exhibited maximum inhibition followed by Pseudomonas fluorescens at 5 days after incubation. These fungal and bacterial antagonists were selected for application to fruits infected with pathogens. Fruits inoculated with C. gloeosporioides were dipped in spore/cell suspensions of fungal/bacterial antagonists and kept for different durations. The fungal antagonists T. harzianum and P. fluorescens were effective in checking the spread of pathogens on fruits compared with the pathogen-inoculated control.  相似文献   

8.
Arbuscular mycorrhiza reduces susceptibility of tomato to Alternaria solani   总被引:1,自引:0,他引:1  
Mycorrhiza frequently leads to the control of root pathogens, but appears to have the opposite effect on leaf pathogens. In this study, we studied mycorrhizal effects on the development of early blight in tomato (Solanum lycopersicum) caused by the necrotrophic fungus Alternaria solani. Alternaria-induced necrosis and chlorosis of all leaves were studied in mycorrhizal and non-mycorrhizal plants over time course and at different soil P levels. Mycorrhizal tomato plants had significantly less A. solani symptoms than non-mycorrhizal plants, but neither plant growth nor phosphate uptake was enhanced by mycorrhizas. An increased P supply had no effect on disease severity in non-mycorrhizal plants, but led to a higher disease severity in mycorrhizal plants. This was parallel to a P-supply-induced reduction in mycorrhiza formation. The protective effect of mycorrhizas towards development of A. solani has some parallels to induced systemic resistance, mediated by rhizobacteria: both biocontrol agents are root-associated organisms and both are effective against necrotrophic pathogens. The possible mechanisms involved are discussed.  相似文献   

9.
Tian  X.L.  Cao  L.X.  Tan  H.M.  Zeng  Q.G.  Jia  Y.Y.  Han  W.Q.  Zhou  S.N. 《World journal of microbiology & biotechnology》2004,20(3):303-309
The populations of endophytic fungi and actinomycetes from four rice cultivars in the Panyu district (Site 1) and Wushan district (Site 2) in Guangdong province, South China, were studied. The preponderant endophytic fungi and actinomycetes isolated belonged to Fusarium and Streptomyces respectively. The incidence of Streptomycetes griseofuscus ranged from 36.1 to 69% out of all the different rice cultivars from the two sites. It is the commonest population of endophytic actinomycetes, and constituted the greatest part of all the antagonistic communities. The distributions of endophytic fungi and actinomycetes in roots and leaves were different, endophytic fungi from leaves were diverse, some were organ-specific. More diverse endophytic actinomycetes were isolated from roots than from leaves. The endophytic fungi isolated from rice in Site 2 were more diverse than that in Site 1. The diversity of the endophytic actinomycetes, however, was less than that in Site 1. Acid soil in Site 2 is ideal for the growth and colonization of fungi while the alkaline soil in Site 1 is better for the growth and colonization of actinomycetes. The results suggested that differences in the chemical composition of soil could influence the endophytic microbial communities of rice plants. The endophytic fungi and actinomycetes isolated from poor-growing seedlings and susceptible rice cultivars were more abundant than that the disease-resistant counterparts. In the dual culture and activity detection of the metabolites, 41.2% of all the isolated endophytic fungi showed antagonism to rice pathogens. Fifty percent of all the isolated endophytic actinomycetes were antagonistic to those pathogens. The percentage of Streptomyces griseofuscus and hygroscopicus reached 55.4 and 21.4% of all the active actinomycetes. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

10.
Bacterial antagonists are bacteria that negatively affect the growth of other organisms. Many antagonists inhibit the growth of fungi by various mechanisms, e.g., secretion of lytic enzymes, siderophores and antibiotics. Such inhibition of fungal growth may indirectly support plant growth. Here, we demonstrate that small organic volatile compounds (VOCs) emitted from bacterial antagonists negatively influence the mycelial growth of the soil-borne phytopathogenic fungus Rhizoctonia solani Kühn. Strong inhibitions (99–80%) under the test conditions were observed with Stenotrophomonas maltophilia R3089, Serratia plymuthica HRO-C48, Stenotrophomonas rhizophila P69, Serratia odorifera 4Rx13, Pseudomonas trivialis 3Re2-7, S. plymuthica 3Re4-18 and Bacillus subtilis B2g. Pseudomonas fluorescens L13-6-12 and Burkholderia cepacia 1S18 achieved 30% growth reduction. The VOC profiles of these antagonists, obtained through headspace collection and analysis on GC-MS, show different compositions and complexities ranging from 1 to almost 30 compounds. Most volatiles are species-specific, but overlapping volatile patterns were found for Serratia spp. and Pseudomonas spp. Many of the bacterial VOCs could not be identified for lack of match with mass-spectra of volatiles in the databases.  相似文献   

11.
About 50 bacterial strains, each of Pseudomonas fluorescens, from different rhizospheric soil of different plants were screened for antagonistic activity against Curvularia lunata, Fusarium oxysporum, Alternaria padwickii, Rhizoctonia solani causing black kernel, kernel spotting, root rots, stackburn and sheath blight diseases of rice (Oryza sativa L.). Out of the 50 isolates, 15 isolates were found to be effective in lysing the cell wall of the above-mentioned putative pathogens tested in vitro. These Pseudomonas isolates produced mycolytic enzymes, viz. β-1,3-glucanases, β-1,4-glucanases and lipases. P. fluorescens PAK1 and PAK12 among the strains were more effective for the production of these enzymes while PAK12 produce good level of β-1,3-glucanases, β-1,4-glucanases and lipases against tested fungal pathogens. These findings demonstrate a mechanism of antagonism by P. fluorescens against different fungal plant pathogens.  相似文献   

12.
The present study was designed to investigate the Puducherry coast of the Bay of Bengal, India for the diversity of bioactive actinomycetes. A total of 50 actinomycete strains were isolated from the marine sediments and most of the strains were belongs to Streptomyces. These strains were identified by means of morphological physiological, biochemical and cultural characteristics. The isolates were subjected to shake flask fermentation and the secondary metabolites were extracted with ethyl acetate and screened for cytotoxicity, hemolytic activity and antimicrobial activity against selected bacterial and fungal pathogens. The cytotoxic activity was evaluated using HeLa cell lines by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole (MTT) assay, hemolytic activity on mouse erythrocytes and the antifungal activity was evaluated by MTT cytotoxic assay against Aspergillus niger, Aspergillus fumigatus and Candida albicans. The antibacterial activity was studied against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Klebsiella pneumoniae. The cytotoxicity and antimicrobial activity of secondary metabolite was found to be concentration dependent and nearly 24% of isolates showed significant antimicrobial, hemolytic and cytotoxic activity. The results of our study indicate the diversity and bioactive potential of marine actinomycetes isolated in the Puducherry coast.  相似文献   

13.
Button mushroom brown blotch disease is one of the most important and devastating diseases in Iran which is caused by Pseudomonas tolaasii. To screen antagonistic bacteria against this pathogen, major mushroom cultivation centres in Iran were surveyed and samples were taken from compost, soil cover and button caps with or without visible symptoms. In total, 120 bacteria were isolated on the basis of their morphology and pathology on excised tissue blocks of the fresh Agaricus bisporus. Among all tested bacteria, thirty-six isolates produced variable inhibition zones and reduced the symptom incidence on tissue blocks of A. bisporus. The most effective antagonistic bacteria caused almost 100% inhibition of pathogenic bacterium. To confirm the identification of antagonistic bacteria, RNA polymerase beta-subunit gene (rpoB) of five antagonistic strains (A1, A2, A3, A4 and A6) were amplified using primer sets of long amplicon primers (LAPS) and LAP27. The polymerase chain reaction products of the strains A1, A3 and A6 were sequenced. Based on phenotypic, biochemical and molecular characteristics, the bacterial antagonists were identified as P. putida (A1), P. reactants (A2 and A6), P. fluorescens (A3 and A4) and Bacillus subtilis (A5), respectively. In all four criteria including weight of the diseased and healthy caps, per cent disease severity and per cent disease incidence, the treatment 2 (P. fluorescens A4) was the most effective from among T1, T3, T4 and T5 treatments. Overall results of this study suggest that bacterial antagonists may be potential biocontrol agents for biological promotion of the health and growth of button mushroom.  相似文献   

14.
The aim of this study was to analyze microbial communities in/on sugar beet with special focus on antagonists toward plant pathogens. For this purpose, the composition of microorganisms isolated from the rhizosphere, phyllosphere, endorhiza, and endosphere of field-grown sugar beet plants was analyzed by a multiphasic approach at three different plant development stages at six locations in Europe. The analysis of microbial communities by Single Strand Conformation Polymorphism (SSCP) of 16S/18S rRNA clearly revealed the existence of discrete microenvironment- and site-specific patterns. A total of 1952 bacterial and 1344 fungal isolates screened by dual testing for antagonism toward the pathogens Aphanomyces cochlioides, Phoma betae, Pythium ultimum, and Rhizoctonia solani resulted in 885 bacterial (=45%) and 437 fungal (=33%) antagonists. In general, the indigenous antagonistic potential was very high and influenced by (a) the location, (b) the plant developmental stage, and (3) the microenvironment. Furthermore, we showed for the first time that the antagonistic potential was highly specific for each target pathogen. The majority of antagonistic microorganisms suppressed only one pathogen (bacteria: 664 = 75%; fungi: 256 = 59%), whereas the minority showed a broad host range (bacteria: 4 = 0.5%; fungi: 7 = 1.6%). The bacterial communities harbored the highest antagonistic potential against P. ultimum, whereas the fungal communities contained more antagonists against A. cochlioides and R. solani. In contrast to their high proportion, only a low diversity of antagonists at genotypic and species level was found. Novel antagonistic species, e.g., Subtercola pratensis or Microbacterium testaceum were found in the internal part of the sugar beet body.  相似文献   

15.
The baiting bag method was found to be useful for isolating antagonistic actinomycetes from terrestrial habitat. Out of total 110 actinomycetes isolated from rhizospheric and non-rhizospheric soil of Indo Gangetic Plains (IGP) of India, 9 isolates exhibited aggressive antagonism against Rhizoctonia solani, screened through dual culture, well diffusion and sealed plate technique. Maximum growth inhibition was recorded up to 50% under well diffusion (S. toxytricini vh22) and 52.6% in a direct confrontation (Actinomycetales bacterium vh41). Whereas maximum disease suppression (53.33%) under green house condition was achieved on seedling treated with S. tricolor vh85. Scanning electron microscopy of antagonists and pathogen interaction exhibited pore formation and hyphal degradation of test pathogen. Physiological and molecular characterization of selected isolates showed wide diversity and uncommon species has been encountered through the selective isolation technique.  相似文献   

16.
The aim of this study was to develop antagonistic strains specific for the coastal agricultural niche in Southern India. Indigenous Pseudomonas strains isolated from rhizosphere of rice cultivated in the coastal agri-ecosystem were screened for in vitro antibiosis against Xanthomonas oryzae pv. oryzaeand Rhizoctonia solani– the bacterial leaf blight (BB) and sheath blight (ShB) pathogens of rice (Oryza sativa) respectively. The strains exhibiting antibiosis were tested in the greenhouse under normal and saline soil conditions. The antagonists suppressed BB by 15 to 74% in an unamended soil. The efficient strains were tested under saline soil conditions and found to suppress disease by 46 to 82%. Similarly, incidence of ShB was also suppressed by 30 to 57% in the unamended soil by the efficient strains which, under saline soil conditions, were found to suppress ShB by 19 to 51%. Four strains of Pseudomonas tested suppressed both BB and ShB diseases in rice, of which three were efficient under both natural and saline soil conditions.  相似文献   

17.

The biocontrol rhizobacterium Pseudomonas chlororaphis is one of the bacterial species of the P. fluorescens group where insecticide fit genes have been found. Fit toxin, supported with other antimicrobial compounds, gives the bacterial the ability to repel and to fight against eukaryotic organisms, such as nematodes and insect larvae, thus protecting the plant host and itself. Pseudomonas chlororaphis PCL1606 is an antagonistic rhizobacterium isolated from avocado roots and show efficient biocontrol against fungal soil-borne disease. The main antimicrobial compound produced by P. chlororaphis PCL606 is 2-hexyl-5-propyl resorcinol (HPR), which plays a crucial role in effective biocontrol against fungal pathogens. Further analysis of the P. chlororaphis PCL1606 genome showed the presence of hydrogen cyanide (HCN), pyrrolnitrin (PRN), and homologous fit genes. To test the insecticidal activity and to determine the bases for such activity, single and double mutants on the biosynthetic genes of these four compounds were tested in a Galleria mellonella larval model using inoculation by injection. The results revealed that Fit toxin and HPR in combination are involved in the insecticide phenotype of P. chlororaphis PCL1606, and additional compounds such as HCN and PRN could be considered supporting compounds.

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18.
Recent and substantial yield losses of Styrian oil pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) are primarily caused by the ascomycetous fungus Didymella bryoniae but bacterial pathogens are frequently involved as well. The diversity of endophytic microbial communities from seeds (spermosphere), roots (endorhiza), flowers (anthosphere), and fruits (carposphere) of three different pumpkin cultivars was studied to develop a biocontrol strategy. A multiphasic approach combining molecular, microscopic, and cultivation techniques was applied to select a consortium of endophytes for biocontrol. Specific community structures for Pseudomonas and Bacillus, two important plant-associated genera, were found for each microenvironment by fingerprinting of 16S ribosomal RNA genes. All microenvironments were dominated by bacteria; fungi were less abundant. Of the 2,320 microbial isolates analyzed in dual culture assays, 165 (7%) were tested positively for in vitro antagonism against D. bryoniae. Out of these, 43 isolates inhibited the growth of bacterial pumpkin pathogens (Pectobacterium carotovorum, Pseudomonas viridiflava, Xanthomonas cucurbitae); here only bacteria were selected. Microenvironment-specific antagonists were found, and the spermosphere and anthosphere were revealed as underexplored reservoirs for antagonists. In the latter, a potential role of pollen grains as bacterial vectors between flowers was recognized. Six broad spectrum antagonists selected according to their activity, genotypic diversity, and occurrence were evaluated under greenhouse conditions. Disease severity on pumpkins of D. bryoniae was significantly reduced by Pseudomonas chlororaphis treatment and by a combined treatment of strains (Lysobacter gummosus, P. chlororaphis, Paenibacillus polymyxa, and Serratia plymuthica). This result provides a promising prospect to biologically control pumpkin diseases.  相似文献   

19.
This study was conducted to achieve biological control for the post-harvest onion bacterial rot diseases with the aid of Egyptian isolates of actinomycetes. In this respect, 45 actinomycetes strains were isolated from Egyptian soils and screened for their antagonistic effect against onion bacterial rot pathogens; Erwinia carotovora subsp. carotovora and Burkholderia cepacia. The most two active strains were identified based on their cultural, morphological and molecular properties as Streptomyces lavendulae HHFA1 and Streptomyces coelicolor HHFA2, the latter was most potent and so was used in vivo (pots and field) for controlling onion bacterial rot. S. coelicolor HHFA2 application resulted in enhancement in the photosynthetic pigments and some foliar growth parameters of onion plants confirming its growth promoting effect. The results of the post-harvest estimation of the disease incidence (DI) of the onion bacterial rot throughout storage revealed that, the application of S. coelicolor HHFA2 reduced the DI pronouncedly comparing with the untreated control and confirm its successful role in the biological control of onion bacterial rot diseases.  相似文献   

20.
Thirty-seven actinomycete species isolated from fertile cultivated soils in Egypt were screened for the production of antimicrobial compounds against a variety of test organisms. Most of the isolates exhibited antimicrobial activities against Gram-positive, Gram-negative, and acid-fast bacteria, yeasts and filamentous fungi, with special attention to fungal and bacterial pathogens of tomato. On starch-nitrate agar, 14 strains were active againstFusarium oxysporum f.sp.lycopersici (the cause ofFusarium wilt), 18 againstVerticillium albo-atrum (the cause ofVerticillium wilt), and 18 againstAlternaria solani (the cause of early blight). In liquid media, 14 isolates antagonizedPseudomonas solanacearum (the cause of bacterial wilt) and 20 antagonizedClavibacter michiganensis ssp.michiganensis (the cause of bacterial canker). The most active antagonists of the pathogenic microorganisms studied were found to beStreptomyces pulcher, S. canescens (syn.S. albidoflavus) andS. citreofluorescens (syn.S. anulatus). The antagonistic activities ofS. pulcher andS. citreofluorescens against pathogenic bacteria in liquid media under shaking conditions. The optimum culture conditions were determined.  相似文献   

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