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1.
A plant growth-promoting isolate of a fluorescent Pseudomonas sp. EM85 and two bacilli isolates MR-11(2) and MRF, isolated from maize rhizosphere, were found strongly antagonistic to Fusarium moniliforme, Fusarium graminearum and Macrophomina phaseolina, causal agents of foot rots and wilting, collar rots/stalk rots and root rots and wilting, and charcoal rots of maize, respectively. Pseudomonas sp. EM85 produced antifungal antibiotics (Afa+), siderophore (Sid+), HCN (HCN+) and fluorescent pigments (Flu+) besides exhibiting plant growth promoting traits like nitrogen fixation, phosphate solubilization, and production of organic acids and IAA. While MR-11(2) produced siderophore (Sid+), antibiotics (Afa+) and antifungal volatiles (Afv+), MRF exhibited the production of antifungal antibiotics (Afa+) and siderophores (Sid+). Bacillus spp. MRF was also found to produce organic acids and IAA, solubilized tri-calcium phosphate and fixed nitrogen from the atmosphere. All three isolates suppressed the diseases caused by Fusarium moniliforme, Fusarium graminearum and Macrophomina phaseolina in vitro. A Tn5:: lacZ induced isogenic mutant of the fluorescent Pseudomonas EM85, M23, along with the two bacilli were evaluated for in situ disease suppression of maize. Results indicated that combined application of the two bacilli significantly (P = 0.05) reduced the Macrophomina-induced charcoal rots of maize by 56.04%. Treatments with the MRF isolate of Bacillus spp. and Tn5:: lacZ mutant (M23) of fluorescent Pseudomonas sp. EM85 significantly reduced collar rots, root and foot rots, and wilting of maize caused by Fusarium moniliforme and F. graminearum (P = 0.05) compared to all other treatments. All these isolates were found very efficient in colonizing the rhizotic zones of maize after inoculation. Evaluation of the population dynamics of the fluorescent Pseudomonas sp. EM85 using the Tn5:: lacZ marker and of the Bacillus spp. MRF and MR-11(2) using an antibiotic resistance marker revealed that all the three isolates could proliferate successfully in the rhizosphere, rhizoplane and endorhizosphere of maize, both at 30 and 60 days after seeding. Four antifungal compounds from fluorescent Pseudomonas sp. EM85, one from Bacillus sp. MR-11(2) and three from Bacillus sp. MRF were isolated, purified and tested in vitro and in thin layer chromatography bioassays. All these compounds inhibited R. solani, M. phaseolina, F. moniliforme, F. graminearum and F. solani strongly. Results indicated that antifungal antibiotics and/or fluorescent pigment of fluorescent Pseudomonas sp. EM85, and antifungal antibiotics of the bacilli along with the successful colonization of all the isolates might be involved in the biological suppression of the maize root diseases.  相似文献   

2.
In tomato soilless culture, slow filtration allows one to control the development of diseases caused by pathogenic microorganisms. During the disinfecting process, microbial elimination is ensured by mechanical and biological factors. In this study, system efficacy was enhanced further to a biological activation of filter by inoculating the pozzolana grains contained in the filtering unit with 5 selected bacteria. Three strains identified as Pseudomonas putida and 2 as Bacillus cereus came from a filter whose high efficiency to eliminate pathogens has been proven over years. These 5 bacteria displayed either a plant growth promoting activity (P. putida strains) or antagonistic properties (B. cereus strains). Over the first months following their introduction in the filter, the bacterial colonisation of pozzolana grains was particularly high as compared to the one observed in the control filter. Conversely to Bacillus spp. populations, Pseudomonas spp. ones remained abundant throughout the whole cultural season. The biological activation of filter unit very significantly enhanced fungal elimination with respect to the one displayed by the control filter. Indeed, the 6-month period needed by the control filter to reach its best efficacy against Fusarium oxysporum was shortened for the bacteria-amended filter; in addition, a high efficacy filtration was got as soon as the first month. Fast colonization of pozzolana grains by selected bacteria and their subsequent interaction with F. oxysporum are likely responsible for filter efficiency. Our results suggest that Pseudomonas spp. act by competition for nutrients, and Bacillus spp. by antibiosis and (or) direct parasitism. Elimination of other fungal pathogens, i.e., Pythium spp., seems to differ from that of Fusarium since both filters demonstrated a high efficacy at the experiment start. Pythium spp. elimination appears to mainly rely on physical factors. It is worth noting that a certain percentage of the 5 pozzolana-inoculated bacteria failed to colonise the filter unit and were, thus, driven to the plants by the nutrient solution. Their contribution to the establishment of a beneficial microbial community in the rhizosphere is discussed.  相似文献   

3.
Suppression of soilborne diseases by biocontrol agents involves complex interactions among biocontrol agents and the pathogen and between these microorganisms and the plant. In general, these interactions are not well characterized. In this work, we studied (i) the diversity among strains of fluorescent Pseudomonas spp., Bacillus spp., and Paenibacillus sp. for their sensitivity to fusaric acid (FAc) and phytoanticipins from different host plants, (ii) the diversity of pathogenic and nonpathogenic Fusarium oxysporum isolates for their sensitivity to phytoanticipins, and (iii) the influence of FAc on the production of pyoverdine by fluorescent Pseudomonas spp. tolerant to this compound. There was a great diversity in the response of the bacterial strains to FAc; however, as a group, Bacillus spp. and Paenibacillus macerans were much more sensitive to FAc than Pseudomonas spp. FAc also affected production of pyoverdine by FAc-tolerant Pseudomonas spp. strains. Phytoanticipins differed in their effects on microbial growth, and sensitivity to a phytoanticipin varied among bacterial and fungal strains. Biochanin A did not affect growth of bacteria, but coumarin inhibited growth of Pseudomonas spp. strains and had no effect on Bacillus circulans and P. macerans. Conversely, tomatine inhibited growth of B. circulans and P. macerans. Biochanin A and tomatine inhibited growth of three pathogenic isolates of F. oxysporum but increased growth of three nonpathogenic F. oxysporum isolates. Coumarin inhibited growth of all pathogenic and nonpathogenic F. oxysporum isolates. These results are indicative of the complex interactions that can occur among plants, pathogens, and biological control agents in the rhizosphere and on the root surface. Also, these results may help to explain the low efficacy of some combinations of biocontrol agents, as well as the inconsistency in achieving disease suppression under field conditions.  相似文献   

4.
The fungal species isolated from Korean cereals (barley, polished barley, wheat, rye, and malt) were Alternaria spp., Aspergillus spp., Chaetomium spp., Drechslera spp., Epicoccum sp., Fusarium spp., and Penicillium spp., etc. The number of Fusarium strains isolated was 36, and their ability to produce Fusarium mycotoxins on rice was tested. Nivalenol (NIV) was produced by Fusarium graminearum (7 of 9 isolates), Fusarium oxysporum (3 of 10 isolates), and Fusarium spp. (7 of 15 isolates). Of 15 isolates of Fusarium spp., 6 formed deoxynivalenol (DON). Fusarenon-X and 3-acetyl-DON were produced by most NIV- and DON-forming isolates, respectively. Zearalenone was produced by 3 isolates of F. graminearum, 1 isolate of Fusarium equiseti, and 11 isolates of Fusarium spp. T-2 toxin was not produced by any Fusarium isolates. The highest concentrations of mycotoxins produced by Fusarium isolates were 77.4 (NIV), 5.3 (DON), 138.3 (fusarenon-X), 40.6 (3-acetyl-DON), and 23.2 (zearalenone) micrograms/g.  相似文献   

5.
Abstract Nitrogenase activity (C2H2 reduction) in root-associated Azospirillum lipoferum, Klebsiella pneumoniae, Enterobacter agglomerans and Pseudomonas sp. isolated from roots of Finnish grasses was assayed in the presence of glyphosate, the phenoxy acid herbicides 2-methyl-4-chlorophenoxy acetic acid (MCPA), 2,4-dichlorophenoxy acetic acid (2,4-D), (±)-2-(2-methyl-4-chlorophenoxy)propionic acid (mecoprop) and (±)-2-(2,4-dichlorophenoxy)propionic acid (dichlorprop), and the commercial products Roundup, Nurmikko-Hedonal, Mepro, and Dipro. In the presence of the phenoxy acid herbicides the nitrogenase activity of K. pneumoniae was significantly inhibited, but that of E. agglomerans was stimulated. With the exception of Mepro and mecoprop no phenoxy acid herbicides inhibited the nitrogenase activity of A. lipoferum and none that of Pseudomonas sp. Nurmikko-Hedonal considerably stimulated the nitrogenase activity of E. agglomerans , and Pseudomanas sp. On the other hand, the nitrogenase activity of both K. pneumoniae and E. agglomerans was considerably repressed by glyphosate and Roundup, which also inhibited the growth of the bacteria. These chemicals had no effect on the growth of A. lipoferum and Pseudomonas sp., but stimulated their nitrogenase activity.  相似文献   

6.
The fungal species isolated from Korean cereals (barley, polished barley, wheat, rye, and malt) were Alternaria spp., Aspergillus spp., Chaetomium spp., Drechslera spp., Epicoccum sp., Fusarium spp., and Penicillium spp., etc. The number of Fusarium strains isolated was 36, and their ability to produce Fusarium mycotoxins on rice was tested. Nivalenol (NIV) was produced by Fusarium graminearum (7 of 9 isolates), Fusarium oxysporum (3 of 10 isolates), and Fusarium spp. (7 of 15 isolates). Of 15 isolates of Fusarium spp., 6 formed deoxynivalenol (DON). Fusarenon-X and 3-acetyl-DON were produced by most NIV- and DON-forming isolates, respectively. Zearalenone was produced by 3 isolates of F. graminearum, 1 isolate of Fusarium equiseti, and 11 isolates of Fusarium spp. T-2 toxin was not produced by any Fusarium isolates. The highest concentrations of mycotoxins produced by Fusarium isolates were 77.4 (NIV), 5.3 (DON), 138.3 (fusarenon-X), 40.6 (3-acetyl-DON), and 23.2 (zearalenone) micrograms/g.  相似文献   

7.
Changes in the microbial flora of pork packed in laminated plastic bags and stored at 4 °C were studied in an initial atmosphere of carbon dioxide, nitrogen or air. The time needed for the total aerobic count at 28 °C to reach 5 × 106 organisms/cm2 was about 7 times longer in carbon dioxide than in air, whilst in nitrogen it was about twice as long.
The predominant organisms on fresh pork taken directly from the processing line were: Acinetobacter calcoaceticus , non-fluorescent Pseudomonas spp. and Flavobacterium spp. After storage in air for 7 d, more than 90% of the flora consisted of non-fluorescent Pseudomonas spp. After storage in nitrogen for 10 d, 70% of the flora consisted of non-fluorescent Pseudomonas spp. with lower levels of fluorescent Pseudomonas spp., Kurthia zopfii, Aeromonas hydrophila and Lactobacillus plantarum. The non-fluorescent Pseudomonas spp. could be divided into three different groups, on proteolytic and lipolytic ability; the distribution of the groups was markedly different between pork loins stored in air and nitrogen.
On pork stored in carbon dioxide for 21 d the flora consisted of L. plantarum together with lower levels of heterofermentative lactic acid bacteria. When the storage time in carbon doxide was prolonged to 35 d, the proportion of heterofermentative lactic acid bacteria increased to about 50% of the flora.  相似文献   

8.
Abstract In soilless cropping systems, soil-borne plant pathogens, especially Fusarium oxysporum , are responsible for severe damage in vegetable and flower cultures. Non-pathogenic Fusarium and fluorescent Pseudomonas are able to control fusarium diseases, thereby increasing the yield. The association of the non-pathogenic Fusarium strain Fo47 and of the fluorescent Pseudomonas strain C7R12 gave a better control of fusarium diseases compared to single inoculations of each antagonistic microorganism. So far, no data have been available on the survival of these two microorganisms in soilless growing substrate. The results of this study indicate that both microorganisms survive well in rockwool when inoculated alone or together as well as in the absence or the presence of plants. Under the present experimental conditions, a single application of the antagonists appears to be enough to get a significant control of fusarium wilts.  相似文献   

9.
Fluorescent Pseudomonad spp. were isolated from the rhizosphere of potato plants (Algeria) by serial dilutions of rhizosphere soils on Kings B medium and were tested for their antifungal activity. The antifungal activity of the Pseudomonas isolated from Potatoes rhizosphere was tested against Pythium ultimum, Rhizoctonia solani and Fusarium oxysporum in dual culture with bacteria on PDA. The Petri dish was divided into tow, on one the bacteria was spread and on the opposite side fungal plugs were inoculated and incubated for one week. Fourteen bacteria were isolated; only one isolate inhibited the growth of Pythium ultimum, Rhizoctonia solani, Fusarium solani; Fusarium oxysporum f.sp. albedinis and Fusarium oxysporum f. sp. Lycopersici with inhibition zones of 39.9, 33.7, 30.8, 19.9 and 22.5 mm respectively.  相似文献   

10.
In 1998–2000 a monitoring of the spectrum of Fusarium species on winter wheat was carried out in the Rhineland. The epidemic spread ofFusarium spp. on wheat plants during growing season was investigated as well as the grain contamination after harvest.F avenaceum was the Fusarium species isolated most frequently followed byF culmorum, F poae andF graminearum. Microdochium nivale occurred considerably only in 1998. Both, susceptibility and plant height of the cultivars were correlated to the incidence of Fusarium species /M nivale on harvested kernels; interactions with cropping intensities were detected. The incidence ofF poae seemed to be independent of the cultivar-specific Fusarium susceptibility. Despite the lack of disease symptoms, between growth stages 45–85 mycelium ofFusarium spp. was detectable in the leaves as well as conidia on the leaf surfaces.  相似文献   

11.
Fusarium spp. isolated from diseased Euphorbia spp. in Europe were assessed for pathogenicity to North American accessions of leafy spurge ( Euphorbia esula/virgata ). Of the nine strains of Fusarium spp. isolated from diseased E. stepposa or E. virgata in the Caucasus region of Russia and E. esula/virgata in southern France, all were pathogenic to leafy spurge. There were significant differences in virulence among strains. Four strains, including the two that were most virulent, were identified as F. oxysporum . Four of the five other strains were identified as F. solani and one was identified as F. proliferatum . Three of the four most virulent strains to leafy spurge were isolated from E. stepposa . The most virulent strain was associated with root damage caused by insect biological control agents, as found earlier with domestic strains of Fusarium spp. pathogenic to leafy spurge. Two strains identified as F. solani were vegetatively compatible. It was concluded that further screening of a larger set of strains of foreign Fusarium spp. under quarantine conditions in the US or in limited overseas facilities would be justified, and could yield promising biological control agents for leafy spurge.  相似文献   

12.
Populations of aerobic heterotrophic bacteria, mycelial fungi and yeasts occurring in malting barley were estimated by a plate technique and scanning electron microscopy. There was an increase in the total number of micro-organisms during germination, although populations declined after kilning. Bacteria dominated on all samples, with progressively lower populations of yeasts and filamentous fungi. There was no obvious spatial distribution of micro-organisms on the samples although there appeared to be high populations of bacteria and fungal hyphae on the inner surface of the kernels. The dominant groups of aerobic heterotrophic bacteria were presumptively identified as Alcaligenes sp., Arthrobacter globiformis, Clavibacter iranicum, Erwinia herbicola, Lactobacillus spp. and Pseudomonas fluorescens. The principal filamentous fungi were identified as Aiternaria alternata, Aspergillus glaucus (group), Cladosporium macrocarpum, Epicoccum purpurascens, Fusarium avenaceum, Geotrichum candidum and Penicillium spp. The yeasts isolated most frequently were Candida catenulata, C. vini, Debaryomyces hansenii, Hansenula polymorpha, Kloeckera apiculata, Rhodotorula mucilaginosa, Sporobolomyces roseus and Trichosporon beigelii.  相似文献   

13.
Cylindrocarpon, Cylindrocladium and Fusarium spp. were often isolated from the woody roots, stem-base and lower foliage of diseased container-grown Calluna vulgaris and Erica spp. plants collected from English and Scottish nurseries. The highest isolation frequencies were obtained for Cylindrocarpon destructans, Cylindrocladium scoparium, Cylindrocladium ilicicola. Fusarium tricinctum, Fusarium avenaceum and Fusarium sporotrichioides . Isolations of these fungi were made more frequently from diseased plants that were at least 1-year-old. The percentage incidence of Cylindrocarpon, Cylindrocladium and Fusarium spp. did not differ between Scottish and English nurseries. Cylindrocarpon destructans. Cylindrocladium ilicicola and C. scoparium were more pathogenic to rooted C. vulgaris cuttings than F. tricinctum. F. avenaceum or F. sporotrichioides in laboratory and glasshouse tests. The high isolation frequency of Cylindrocarpon. Cylindrocladium and Fusarium spp., and their pathogenicity in tests, suggests that these fungi are involved in root, stem-base and lower foliage diseases in crops of C. vulgaris and Erica spp. The importance of these findings for the integrated control of diseases on ericaceous plant nurseries is discussed.  相似文献   

14.
镰刀菌真菌毒素产生与调控机制研究进展   总被引:4,自引:0,他引:4  
张岳平 《生命科学》2011,(3):311-316
镰刀菌是一种重要的植物病原菌,给世界范围内农作物生产带来巨大破坏。除导致产量下降外,由其产生的镰刀菌真菌毒素能够污染农产品品质,给动物和人类食物安全造成严重隐患。单端孢霉烯族毒素(Trichothecenes)、伏马菌素(Fumonisin)和玉米赤霉烯酮(Zearalenone)是三种最重要的镰刀菌真菌毒素。镰刀菌真菌毒素的生物合成与生产受到体内一系列相关功能基因的调控;此外,pH值、碳氮比等环境条件也能影响真菌毒素的产量。本文简述了镰刀菌真菌毒素在产生机理、主要分类、致病性以及调控因素等方面的研究进展。  相似文献   

15.
The effect of inorganic nutrients (sulfate, phosphate, and ammonium chloride) on the aerobic biodegradation of benzene, toluene, and xylene (BTX) by Pseudomonas spp. was studied in the laboratory using a glass sand tank. The increase of nutrient levels resulted in enhanced bacterial growth and BTX degradation. Sulfate and phosphate serve as key electron acceptors in the microbiological processes degrading BTX. The observed bacterial morphological changes during BTX degradation reveal that the filamentous bacteria were the dominant species at low temperatures about 20 degrees C. The spherical and rod-shaped cells became dominant at higher temperatures ranging from 25 degrees C to 28 degrees C. When the BTX mixture was allowed to be biodegraded for longer incubation periods of 21-42 h at high phosphate concentrations, large amounts of rod-shaped cells were clustered. The morphological adaptation appears to be controlled by the temperature and nutrient levels in the sandy medium where Pseudomonas spp. thrives.  相似文献   

16.
An unstructured mathematical model was developed and used in the evaluation of biochemical activities of four Azospirillum spp. strains grown in batch cultures in a high C/N-ratio medium. The strains were evaluated for their ability to grow on fructose and produce exo-polysaccharide, and to sustain nitrogenase activity by using fructose or polysaccharides. Quantitative expression of the regulation of polysaccharide synthesis and nitrogenase (acetylene reduction) activity from the mineral nitrogen and sugar concentration in the culture medium was achieved. It was found that, during growth, Azospirillum spp. produced significant quantities of exocellular and capsular polysaccharide, whereas after depletion of the carbon source from the culture medium polysaccharides were consumed, especially in A. lipoferum strains. Significant nitrogenase activity was detected during polysaccharide degradation. Oxygen uptake was high during assimilation of fructose and low during polysaccharide degradation.  相似文献   

17.
Fusarium spp. and Scedosporium spp. have emerged as important fungal pathogens that are frequently resistant to antifungal compounds. We investigated the effects of human interleukin-15 (IL-15) on human polymorphonuclear leukocyte (PMNL) activity against Fusarium solani and Fusarium oxysporum as well as Scedosporium prolificans and Scedosporium apiospermum. IL-15 (100 ng/ml) significantly enhanced PMNL-induced hyphal damage of both Fusarium spp. and S. prolificans after incubation for 22 h (P < 0.01) but not S. apiospermum. In addition, IL-15 enhanced PMNL oxidative respiratory burst evaluated as superoxide anion production in response to S. prolificans but not to the other fungi after 2 h incubation. IL-15 increased interleukin-8 (IL-8) release from PMNLs challenged with hyphae of F. solani and S. prolificans (P< or = 0.04). Release of tumor necrosis factor-alpha was not affected. The species-dependent enhancement of hyphal damage and induction of IL-8 release suggest that IL-15 plays an important role in the immunomodulation of host response to these emerging fungal pathogens.  相似文献   

18.
Nitrogenase activity exhibits a dilution effect. Evidence is presented that the reason for the dilution effect is that one of the component proteins of nitrogenase is limiting in preparations of this enzyme. The limiting component appears to be the non-haem-iron-containing protein (also called fraction II, iron protein, azoferredoxin), which is equivalent to the enhancement factor for nitrogenase activity present in extracts of nitrogenaseless mutant 22R1. A mathematical function of specific activity is described that is useful in describing nitrogenase. It takes into account the dilution effect and the exponential nature of the relationship between nitrogenase activity and enzyme protein concentration.  相似文献   

19.
Hydrogen cyanide (HCN) is a broad-spectrum antimicrobial compound involved in biological control of root diseases by many plant-associated fluorescent pseudomonads. The HCN synthase is encoded by three biosynthetic genes (hcnA, hcnB, and hcnC), but little is known about the diversity of these genes in fluorescent Pseudomonas spp. and in other bacteria. Here, the partial hcnBC sequence was determined for a worldwide collection of biocontrol fluorescent Pseudomonas spp. Phylogenies based on hcnBC and deduced protein sequences revealed four main bacterial groups, but topological incongruences were found between hcnBC and rrs-based phylogenies, suggesting past lateral transfer of hcnBC among saprophytic root-colonizing pseudomonads. Three of the four groups included isolates from different countries and host plants. Yet, these groups corresponded to distinct, ecologically-adapted populations of HCN-producing biocontrol fluorescent pseudomonads, as indicated by high hcnBC distinctness ratio values and the differences in production levels of HCN in vitro found between groups. This is in accordance with previous results on catabolic properties and biocontrol abilities of these strains. HCN synthase gene diversity may thus reflect the adaptive radiation of HCN+ biocontrol fluorescent pseudomonads. Positive correlations were found between HCN production in vitro and plant protection in the cucumber/Pythium ultimum and tomato/Fusarium oxysporum f. sp. radicis-lycopersici pathosystems.  相似文献   

20.
C. CHAPUIS AND J.-P. FLANDROIS. 1994. The interactions between six different Micrococcus species and two strains of Pseudomonas aeruginosa were studied on an agar surface. This type of interaction on solid surface could act as a model of situations occurring either in the environment, in food or in man. The hypothesis of an amensalistic relationship between a Micrococcus spp. and Pseudomonas aeruginosa , due essentially to Ps. aeruginosa bacteriolytic enzymes, is retained as the basis for a mathematical model of the variations of the colony surface of Micrococcus spp. ( S ) with respect to the distance ( d ) from Ps. aeruginosa cells. The diffusion of the bacteriolytic substance in agar explains the limitation of the growth of the Micrococcus spp. This model S = S max (1 - e-md***2) is shown to be adapted to all the interactions studied.  相似文献   

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