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1.
Two root-colonizing Fusarium strains, Ls-F-in-4-1 and Rs-F-in-11, isolated from roots of Brassicaceae plants, induced the resistance in Lepidium sativum seedlings against Pythium ultimum. These strains caused an increase in the content of benzyl isothiocyanate, and of its precursor glucotropaeolin, in the roots of the host plants. The increased isothiocyanate content is one of the factors contributing to the resistance of L. sativum against P. ultimum. To be transformed into the fungitoxic compound benzyl isothiocyanate, glucotropaeolin has to be hydrolyzed by myrosinase, which can be produced either by plants or microorganisms. The Fusarium strain Ls-F-in-4-1 has a myrosinase activity but the strain Rs-F-in-11 has not. These results suggest that both strains are able to trigger the metabolic pathway leading to benzyl isothiocyanate production in the plant. In the case of the myrosinase-negative strain Rs-F-in-11, hydrolyzation into isothiocyanate is only due to the myrosinase activity of the plant, and in the other case, the myrosinase produced by the strain Ls-F-in-11 also would contribute to the production of isothiocyanate. This paper reports a new mode of action of non-pathogenic Fusarium strains in controlling P. ultimum.  相似文献   

2.
Fertilizer costs are a major component of corn production. The use of biofertilizers may be one way of reducing production costs. In this study we present isolation and identification of three plant growth promoting bacteria that were identified as Enterobacter cloacae (CR1), Pseudomonas putida (CR7) and Stenotrophomonas maltophilia (CR3). All bacterial strains produced IAA in the presence of 100 mg l−1 of tryptophan and antifungal metabolites to several soilborne pathogens. S. maltophilia and E. cloacae had broad spectrum activity against most Fusarium species. The only strain that was positive for nitrogen fixation was E. cloacae and it, and P. putida, were also positive for phosphate solubilization. These bacteria and the corn isolate Sphingobacterium canadense CR11, and known plant growth promoting bacterium Burkholderia phytofirmans E24 were used to inoculate corn seed to examine growth promotion of two lines of corn, varieties 39D82 and 39M27 under greenhouse conditions. When grown in sterilized sand varieties 39M27 and 39D82 showed significant increases in total dry weights of root and shoot of 10-20% and 13-28% and 17-32% and 21-31% respectively. Plants of the two varieties grown in soil collected from a corn field had respective increases in dry weights of root and shoot of 10-30% and 12-35% and 11-19% and 10-18%. In sand, a bacterial mixture was highly effective whereas in soil individual bacteria namely P. putida CR7 and E. cloacae CR1 gave the best results with 39M27 and 39D82 respectively. These isolates and another corn isolate, Azospirillum zeae N7, were tested in a sandy soil with a 55 and 110 kg ha−1 of nitrogen fertility at the Delhi research Station of Agriculture and Agri-Food Canada over two years. Although out of seven bacterial treatments, no treatment provided a statistically significant yield increase over control plots but S. canadense CR11 and A. zeae N7 provided statistically significant yield increase as compared to other bacteria. The 110 kg rate of nitrogen provided significant yield increase compared to the 55 kg rate in both years.  相似文献   

3.
The effects of three Coniothyrium minitans isolates (Conio, IVT1 and Contans®), applied to soil as conidial suspensions or as maizemeal-perlite (MP) inocula (Conio), on apothecial production and infection of Sclerotinia sclerotiorum sclerotia were assessed in two soil pot bioassays and two novel box bioassays in the glasshouse at different times of the year. C. minitans isolate Conio applied as either MP or ground MP at full rate (106-107 cfu cm−3 soil) consistently decreased the carpogenic germination, recovery and viability of sclerotia and increased C. minitans infection of the sclerotia of S. sclerotiorum by in comparison with either MP or conidial suspension treatments applied at lower rates (103-104 cfu cm−3 soil). Additionally, when applied at the same rate, MP inoculum of C. minitans was consistently more effective at reducing carpogenic germination than a conidial suspension. The effect of MP and ground MP at full rate on carpogenic germination was expressed relatively early as those sclerotia recovered before apothecia appeared on the soil surface already had reduced numbers of apothecial initials. In general, there were few differences between the isolates of C. minitans applied as conidial suspensions. Box bioassays carried out at different times of the year indicated that temperature and soil moisture influenced both apothecial production and mycoparasitism. Inoculum concentration of C. minitans and time of application appear to be important factors in reducting apothecial production by S. sclerotiorum.  相似文献   

4.
The effect of the soil yeast, Rhodotorula mucilaginosa LBA, on Glomus mosseae (BEG n°12) and Gigaspora rosea (BEG n°9) was studied in vitro and in greenhouse trials. Hyphal length of G. mosseae and G. rosea spores increased significantly in the presence of R. mucilaginosa. Exudates from R. mucilaginosa stimulated hyphal growth of G. mosseae and G. rosea spores. Increase in hyphal length of G. mosseae coincided with an increase in R. mucilaginosa exudates. No stimulation of G. rosea hyphal growth was detected when 0.3 and 0.5 ml per petri dish of yeast exudates was applied. Percentage root length colonization by G. mosseae in soybean (Glycine max L. Merill) and by G. rosea in red clover (Trifolium pratense L. cv. Huia) was increased only when the soil yeast was inoculated before G. mosseae or G. rosea was introduced. Beneficial effects of R. mucilaginosa on arbuscular mycorrhizal (AM) colonization were found when the soil yeast was inoculated either as a thin agar slice or as a volume of 5 and 10 ml of an aqueous solution. R. mucilaginosa exudates (20 ml per pots) applied to soil increased significantly the percentage of AM colonization of soybean and red clover.  相似文献   

5.
The aim of this study was to investigate the potentials and limitations in restoring soil suppressiveness in disturbed soils. Soils from three sites in UK and Switzerland (STC, REC, THE) differing in their level of suppressiveness to soil-borne and air-borne diseases were γ-irradiated and this soil matrix was re-inoculated with 1% (w/w) of either parent native soil or native soil from the other sites (‘soil inoculum’). Suppressiveness to air-borne and soil-borne diseases was quantified by means of the host-pathogen systems Lepidium sativum (cress)-Pythium ultimum, an oomycete causing root rot and seedling damping-off, and Arabidopsis thaliana-Hyaloperonospora parasitica, an oomycete causing downy mildew. Soil microbial biomass, activity and community structure, as determined by phospholipid fatty acid (PLFA) profiles, were measured in native, γ-irradiated, and re-inoculated soils. Both, L. sativum and A. thaliana were highly susceptible to the pathogens if grown on γ-irradiated soils. Re-inoculation completely restored suppressiveness of soils to the foliar pathogen H. parasitica, independently of soil matrix or soil inoculum, whereas suppressiveness to P. ultimum depended on the soil matrix and, to a lesser extent, on the soil inoculum. However, the soil with the highest inherent suppressiveness did not reach the initial level of suppressiveness after re-inoculation. In addition, native microbial populations as defined by microbial biomass, activity and community structure, could not be fully restored in re-inoculated soils. As for suppressiveness to P. ultimum, the soil matrix, rather than the source of soil inoculum was identified as the key factor for re-establishing the microbial community structure. Our data show that soils do not or only slowly fully recover from sterilisation by γ-irradiation, indicating that agricultural soil management practices such as soil fumigation or heat treatments frequently used in vegetable cropping should be avoided.  相似文献   

6.
Enterobacter cloacae is a plant-beneficial bacterium that shows promise for suppression of damping-off of cucumber and other crops caused by Pythium ultimum. We have been using a mutational approach to determine the E. cloacae genes important in bacterial-plant and bacterial-pathogen interactions in the spermosphere and rhizosphere. E. cloacae M43 is a transposon mutant of E. cloacae 501R3 that was significantly impaired in colonization of seeds and roots of diverse crop plants. Strain M43 did not increase in population on cucumber, sunflower, and wheat seeds and was significantly reduced in growth on pea seeds relative to strain 501R3. Populations of M43 were also dramatically lower than those of strain 501R3 in cucumber, pea, sunflower, and wheat rhizosphere in 42 d experiments. Molecular characterization of M43 demonstrated that there was a single transposon insertion in the genome of this strain and that this insertion was in a region of the E. cloacae genome with a high degree of DNA sequence identity with aceF. aceF encodes the dihydrolipoamide acetyltransferase subunit of the pyruvate dehydrogenase complex (PDHC). Cell lysates from strain 501R3 grown on minimal medium plus 50 mM glycerol and 2 mM acetate contained 0.011±0.0036 U pyruvate dehydrogenase activity while cell lysates from M43 grown under identical conditions contained no detectable pyruvate dehydrogenase activity. Additionally, the nutritional use profile of M43 under aerobic and anaerobic conditions was as expected for an ace mutant. Experiments reported here strongly suggest a role for aceF and the PDHC in colonization of seeds and roots of diverse crop plants by E. cloacae.  相似文献   

7.
Plants of the Brassicaceae contain glucosinolates, the hydrolysis products of which inhibit the growth of many soil-borne fungi that cause plant disease. However, amending soil with green manures of these plants gives inconsistent control of several soil-borne diseases, including those caused by Rhizoctonia solani. To identify factors that contribute to this inconsistency we investigated, in the laboratory and in pot experiments in the glasshouse, the saprophytic behaviour of R. solani AG2-1 (ZG5) in a sandy soil amended with various green manures. Fresh material from either Brassica napus var. Karoo, B. napus B1, B. napus B2, B. nigra, Diplotaxis tenuifolia (a brassicaceous weed) and the non-Brassicaceae species, oat (Avena sativa) or lupin (Lupinus angustifolius) was used at 10 or 100 g of fresh material kg−1 of dry soil in Lancelin sand. At 100 g kg−1 the volatiles of all green manures reduced the hyphal growth of R. solani, except for B. napus B1. D. tenuifolia at 100 g kg−1 inhibited the growth and sclerotial formation of R. solani. Most green manures at 10 g kg−1, and at 40% water holding capacity, stimulated the growth of R. solani for up to 3 months and increased the activity of other microbes. R. solani infected the brassicaceous plants when growing and colonized the residues mixed with soil at 10 g kg−1. This inoculum increased the severity of damping-off in canola, by 27%. Disease was particularly severe when the green manure species, except D. tenuifolia and oat, were grown in situ and residues returned to the pot from which they came, before sowing canola. There is a potential hazard in applying green manures of Brassica species as their residues can, under certain conditions, support the saprophytic activity of R. solani which increases damping-off in canola sown in the amended soils.  相似文献   

8.
Two indole-producing Paenibacillus species, known to be associated with propagules of arbuscular mycorrhizal (AM) fungi, were examined for their mycorrhization helper bacteria activity at pre-symbiotic and symbiotic stages of the AM association. The effects were tested under in vitro and in vivo conditions using an axenically propagated strain of the AM fungus Glomus intraradices and Glycine max (soybean) as the plant host. The rates of spore germination and re-growth of intraradical mycelium were not affected by inoculation with Paenibacillus strains in spite of the variation of indole production measured in the bacterial supernatants. However, a significant promotion in pre-symbiotic mycelium development occurred after inoculation of both bacteria under in vitro conditions. The Paenibacillus rhizosphaerae strain TGX5E significantly increased the extraradical mycelium network, the rates of sporulation, and root colonization in the in vitro symbiotic association. These results were also observed in the rhizosphere of soybean plants grown under greenhouse conditions, when P. rhizosphaerae was co-inoculated with G. intraradices. However, soybean dry biomass production was not associated with the increased development and infectivity values of G. intraradices. Paenibacillus favisporus strain TG1R2 caused suppression of the parameters evaluated for G. intraradices during in vitro symbiotic stages, but not under in vivo conditions. The extraradical mycelium network produced and the colonization of soybean roots by G. intraradices were promoted compared to the control treatments. In addition, dual inoculation had a promoting effect on soybean biomass production. In summary, species of Paenibacillus associated with AM fungus structures in the soil, may have a promoting effect on short term pre-symbiotic mycelium development, and little impact on AM propagule germination. These findings could explain the associations found between some bacterial strains and AM fungus propagules.  相似文献   

9.
The effects of elevated CO2 supply on N2O and CH4 fluxes and biomass production of Phleum pratense were studied in a greenhouse experiment. Three sets of 12 farmed peat soil mesocosms (10 cm dia, 47 cm long) sown with P. pratense and equally distributed in four thermo-controlled greenhouses were fertilised with a commercial fertiliser in order to add 2, 6 or 10 g N m−2. In two of the greenhouses, CO2 concentration was kept at atmospheric concentration (360 μmol mol−1) and in the other two at doubled concentration (720 μmol mol−1). Soil temperature was kept at 15 °C and air temperature at 20 °C. Natural lighting was supported by artificial light and deionized water was used to regulate soil moisture. Forage was harvested and the plants fertilised three times during the basic experiment, followed by an extra fertilisations and harvests. At the end of the experiment CH4 production and CH4 oxidation potentials were determined; roots were collected and the biomass was determined. From the three first harvests the amount of total N in the aboveground biomass was determined. N2O and CH4 exchange was monitored using a closed chamber technique and a gas chromatograph. The highest N2O fluxes (on average, 255 μg N2O m−2 h−1 during period IV) occurred just after fertilisation at high water contents, and especially at the beginning of the growing season (on average, 490 μg N2O m−2 h−1 during period I) when the competition of vegetation for N was low. CH4 fluxes were negligible throughout the experiment, and for all treatments the production and oxidation potentials of CH4 were inconsequential. Especially at the highest rates of fertilisation, the elevated supply of CO2 increased above- and below-ground biomass production, but both at the highest and lowest rates of fertilisation, decreased the total amount of N in the aboveground dry biomass. N2O fluxes tended to be higher under doubled CO2 concentrations, indicating that increasing atmospheric CO2 concentration may affect N and C dynamics in farmed peat soil.  相似文献   

10.
Summary Damping-off of lettuce (Lactuca sativa) caused by Pythium ultimum was studied in pots containing a non-sterile potting mix in the glasshouse. Fifty P. ultimum sporangia g-1 compost reduced the plant stand to 15% and shoot dry weight to 18%, but this reduction was totally prevented by applying Trichoderma harzianum at 2×105 viable propagules g-1 potting mix. Gliocladium virens and Enterobacter cloacae also alleviated the damping-off. E. cloacae did not adversely affect the action of the fungal antagonists. The co-existence of the bacterial and fungal antagonists was revealed on the root surface and inner surface of the testa by scanning electron microscopy, indicating the compatibility of the biocontrol agents.  相似文献   

11.
The motility and efficacy of Pseudomonas oryzihabitans as a biocontrol agent against the potato cyst nematode Globodera rostochiensis were studied with respect to temperature. The influence of soil moisture on bacterial movement was also tested. In a closed container trial, P. oryzihabitans significantly reduced invasion of second stage juveniles (J2) of G. rostochiensis in potato roots, its effect being more marked at 25 and 21 °C than at 17 °C. P. oryzihabitans motility in vitro was optimal at 26 °C and inhibited at temperatures below 18 °C. In soil, both temperature and matric potential affected bacterial movement. At 16 °C its movement and survival were suppressed, but they were unaffected at 25 °C. At both temperatures the biocontrol agent moved faster in the wetter (−0.03 MPa) than in the drier soil (−0.1 MPa). These results suggest that temperature is a key factor in determining the potential of P. oryzihabitans as a biocontrol agent.  相似文献   

12.
A bacterium having strong chitinolytic activity was isolated from a coastal soil in Korea and identified as Paenibacillus illinoisensis KJA-424 on the basis of the nucleotide sequence of a 16S rRNA gene. By activity staining after SDS-PAGE, three major chitinase bands with chitinolytic activity, approximate molecular weight of 63, 54 and 38 kDa were detected. On co-culture Rhizoctonia solani with KJA-424, abnormal swelling and deformation of R. solani hyphae were observed, where the release of N-acetyl-d-glucosamine was detected. The bacterium suppressed the symptom of damping-off cucumber seedlings caused by R. solani, in greenhouse trial.  相似文献   

13.
Carbon isotopic composition of soils subjected to C3-C4 vegetation change is a suitable tool for the estimation of C turnover in soil organic matter (SOM) pools. We hypothesized that the biological availability of SOM pools is inversely proportional to their thermal stability. Soil samples from a field plot with 10.5 years of cultivation of the C4 plant Miscanthus×gigantheus and from a reference plot under C3 grassland vegetation were analysed by thermogravimetry coupled with differential scanning calorimetry (TG-DSC). According to differential weight losses (dTG) and energy release or consumption (DSC), five SOM pools with increasing thermal stability were distinguished: (I) 20-190 °C, (II) 190-310 °C, (III) 310-390 °C, (IV) 390-480 °C, and (V) 480-1000 °C. Their δ13C values were analysed by EA-IRMS. The weight losses in pool I were connected with water evaporation, since no significant C losses were measured and δ13C values remained unchanged. The δ13C of pools II and III in soil samples under Miscanthus were closer to the δ13C of the Miscanthus plant tissues (−11.8‰) compared to the thermally stable SOM pool V (−19.5‰). The portion of the Miscanthus-derived C4-C in total SOM in 0-5 cm reached 55.4% in the 10.5 years. The C4-C contribution in pool II was 60% and decreased down to 6% in pool V. The mean residence times (MRT) of SOM pools II, III, and IV were similar (11.6, 12.2, and 15.4 years, respectively), while pool V had a MRT of 163 years. Therefore, we concluded that the biological availability of thermal labile SOM pools (<480 °C) was higher, than that of the thermal stable pool decomposed above 480 °C. However, the increase of SOM stability with rising temperature was not gradual. Therefore, the applicability of the TG-DSC for the separation of SOM pools with different biological availability is limited.  相似文献   

14.
Colonization and survival of the inoculated bacteria in rhizosphere of maize were investigated in field and pot experiments conducted for 3 consecutive years under rainfed conditions of Himalayan region. The effect of bacterial inoculations on growth and yield related parameters of maize were also evaluated. While three bacterial species, viz. Bacillus megaterium, Bacillus subtilis and Pseudomonas corrugata were tested in 1st year experiments, P. corrugata (based on the 1st year results) was chosen for inoculation in the subsequent experiments. All the three bacterial inoculants showed good rhizosphere competence giving high inoculum numbers (log10 11.13-11.34 cfu g−1). The bacterial inoculations by B. megaterium, B. subtilis and P. corrugata resulted in an increment in grain yield of maize up to 122.4%, 135.2% and 194.3%, respectively, as compared to respective control. In 1st year, the antibiotic marked (Nalr Rifr) inoculant P. corrugata resulted in the highest increase in grain yield, statistically significant (P<0.05) as compared to control, B. megaterium and B. subtilis. In 2nd and 3rd year experiments, P. corrugata increased the grain yield up to 147.28% and 149.93%, respectively, as compared to control. The best performance and consistent trend of P. corrugata to increase plant yields was credited to its initial isolation from rhizosphere of maize growing under temperate conditions. The overall beneficial effects of bacterial inoculations on maize were contributed to (1) the colonization and survival of the introduced bacteria, and (2) stimulation of the indigenous microflora in the rhizosphere. Based on the comprehensive results obtained in this study, P. corrugata may be recommended as suitable bioinoculant for maize fields of temperate climate grown under rainfed conditions.  相似文献   

15.
Pseudomonas sp. 30-3, a toluene degrading microorganism isolated from oil-contaminated Antarctic soils, was shown to form aggregated flocs of cells when exposed to temperatures of 22 and 4 °C, with an increase in aggregation at 4 °C. This was speculated to be due to the secretion of an extracellular polymeric substance (EPS), thus protecting the organism from cold or frost damage. The flocs of cells were stained with the Live/Dead BacLight Bacterial Viability kit and found to be viable cells. The EPS was identified by lectin binding analysis to consist of N-acetyl-d-glucosamine and N-acetylneuraminic acid. An enzyme-linked lectinosorbent assay was also carried out to quantify the amount of EPS produced at 37, 22 and 4 °C. Results showed that at 37 °C the amount of EPS secreted was low, but there was little difference in the amount of EPS secreted at 22 and 4 °C by Pseudomonas sp. 30-3.  相似文献   

16.
Metal rich fly ash dumps may serve as repository of ecologically useful multi-functional rhizobacteria having potential use in the development of vegetation at the dumps. Therefore, in the present study bacteria from the rhizosphere of a wild perennial grass colonizing Indraprastha and Badarpur fly ash dumps of Delhi region were purified, identified and functionally characterized. The fly ash had low levels of nutrients, moisture and organic matter coupled with toxic levels of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn). Both the dumps were mostly barren except for a few patches of Saccharum ravennae and some weedy species. Sixty five dominant, morphologically distinct rhizobacteria were purified, which belonged to 18 genera and 38 species. Gram-positive bacteria were dominating in the fly ash environment. Bacillus spp. and Paenibacillus spp. were common at both the dumps. Multi-metal tolerance was shown by diverse bacterial taxa. The minimum inhibitory concentration (MIC) was highest for As (12.5-20.0 mM) and Pb (7.5-10.0 mM), although many rhizobacteria also possessed significant tolerance to Cr, Zn, Ni, Cu, Co and Cd. The tolerance profiles of rhizobacteria to different metals may be ranked in the decreasing order as As > Pb > Cr > Zn > Ni > Cu > Co > Cd > Hg. Majority of rhizobacteria showed good siderophore activity. Multiple-metal tolerance was also coupled with high siderophore production in some of the isolates (Microbacterium barkeri IPSr74, Serratia marcescens IPSr90 and IPSr82, Enterococcus casseliflavus BPSr32, Bacillus sp. IPSr80, Pseudomonas aeruginosa BPSr43 and Brochothrix campestris BPSr3). Most of the bacteria could grow on nitrogen-deficient medium. However, the dominant nitrogen-fixers reported from the rhizosphere of other Saccharum species were not detected. S. marcescens IPSr90 was the only rhizobacterium, which showed ACC-deaminase (ACCD) activity. Proportion of phosphate-solubilizing bacteria was high. Considerable improvement in the seedling establishment, plant weight and shoot length in rhizobacterial inoculated plants of S. ravennae in fly ash environment indicated the significance of rhizobacteria in its colonization and spread to the dumps. Representative rhizobacteria, with high MIC (for most of the metals) and good plant growth promoting (PGP) traits comparable to commercially useful bacterial inoculants were identified as S. marcescens IPSr82 and IPSr90, P. aeruginosa BPSr43, Paenibacillus larvae BPSr106, Arthrobacter ureafaciens BPSr55, Paenibacillus azotofixans BPSr107 and E. casseliflavus BPSr32. S. ravennae and some of these rhizobacteria may be potentially useful for the development of inoculation technologies for conversion of barren fly ash dumps into ecologically and economically productive habitats.  相似文献   

17.
The biocontrol agents Coniothyrium minitans and Bacillus subtilis MBI 600 were added separately to three soil types that had been either sterilised, pasteurised or left non-sterile. Applied as a conidial suspension of 1×106 cfu g−1 soil, C. minitans showed good survival in all sterilised, pasteurised and non-sterile soils, remaining at the numerical level at which it was applied for the duration of the 30 d experiment. Applied at a lower rate of 1×103 cfu g−1 soil, C. minitans proliferated in sterilised soil to numbers slightly over 1×106 cfu g−1 soil, whereas no increase was seen in pasteurised or non-sterile soils from this lower application rate. However, although C. minitans was not easily recovered on plates from non-sterile soil, it did survive at the lower numerical level in pasteurised soil, and was recoverable throughout the experiment at the rate at which it was applied. B. subtilis MBI 600 survived well following introduction as a cell suspension into sterilised soil at a rate of 1×106 cfu g−1 soil. Spores were formed rapidly and, after 14 d, the introduced microorganism survived in this form rather than as vegetative cells. However, in non-sterile soil, the introduced microorganism did not compete well and decreased in number, with spores being formed in low numbers. Survival of B. subtilis MBI 600 in pasteurised soil was variable, but resembled the survival seen in non-sterile soil more than that seen in sterilised soil. More B. subtilis MBI 600 spores were formed in pasteurised soil than in non-sterile soil, however, and may have been important for survival in pasteurised soil. In conclusion, this work has shown that the biocontrol agent C. minitans can survive well in soil irrespective of whether the soil has been pasteurised or not and shows good promise as a soil inoculant for control of Sclerotinia sclerotiorum. Although soil pasteurisation does improve establishment of B. subtilis MBI 600 compared to non-sterile soil, survival is relatively poor when applied as cells. The best survival of B. subtilis MBI 600 occurred as spores in sterilised soil, and spore applications to pasteurised soil in an integrated control strategy may allow sufficient establishment of the biocontrol agent to target pathogens causing damping-off.  相似文献   

18.
The capability of native bacterial strains isolated from Lolium perenne rhizosphere to behave as plant growth promoting bacteria and /or biocontrol agents was investigated. One strain (BNM 0357) over 13 isolates from the root tips of L. perenne resulted proved to be nitrogenase positive (ARA test) and an IAA producer. Conventional tests and the API 20E diagnostic kit indicated that BNM 0357 behaves to the Enterobacteriaceae family and to the Enterobacter genus. Molecular identification by 16S rRNA sequence analysis indicated that BNM 0357 had the highest similarity to Enterobacter ludwigii (EN-119). Isolate BNM 0357 had the capability to solubilize calcium triphosphate and to antagonize Fusarium solani mycelial growth and spore germination. Strain BNM 0357 also showed the ability to improve the development of the root system of L. perenne. This study disclosed features of E. ludwigii BNM 0357 that deserve further studies aimed at confirming its putative importance as a PGPR.  相似文献   

19.
Vermicomposts are produced through interactions between earthworms and microorganisms in the breakdown of organic wastes. Aqueous extracts were prepared in commercial brewing equipment from vermicomposts produced from super-market food wastes. The ratio of vermicompost to water was one to five v:v, to produce a 20% aqueous solution which could be diluted to 5% and 10% concentrations. The effects of soil drenches applied at dilutions of 20%, 10%, and 5% vermicompost aqueous extracts, were compared with those of deionized water, in the suppression of cucumber beetles (Acalymna vittatum) attacking cucumbers and tobacco hornworms (Manduca sexta) attacking tomatoes, in greenhouse cage experiments. Tomatoes and cucumber seedlings were germinated and grown for 4 weeks in 25 cm diameter pots containing a soil-less growth medium - Metro-Mix 360 - and thinned to four plants per pot. They were placed under 0.2 mm mesh cages (40 cm×40 cm×40 cm), with one pot containing four plants in each treatment cage. At germination, plants were treated with soil drenches of 5%, 10%, or 20% vermicompost extract or a deionized water control to field capacity and thereafter at weekly intervals. A complete nutrient solution was applied weekly to all plants. In each experiment, eight cucumber beetles or eight tobacco hornworms were released onto the leaves of the appropriate plant species in each cage (four pests per test plant). All treatments were replicated four times per pest experiment, in a randomized complete block design. Numbers of pests were counted and damage rated (0-none to 5-total) on days 1, 3, 5, 7, 9, 11, 13 and 14 after the release of pests into the cages.All of the concentrations of vermicompost extracts significantly suppressed the establishment of and the damage caused by the two pests on the plants. The higher the rate of aqueous extract application the greater was the suppression of the pests. We concluded that the most likely cause for the unpalatability of the plants to pests was the uptake of soluble phenolic compounds from the vermicompost aqueous extracts into the plant tissues. These compounds are known to make plants unattractive to pests and to affect pest reproduction and survival rates.  相似文献   

20.
There is now clear evidence for a prolonged increase in atmospheric CO2 concentrations and enrichment of the biosphere with N. Understanding the fate of C in the plant-soil system under different CO2 and N regimes is therefore of considerable importance in predicting the environmental effects of climate change and in predicting the sustainability of ecosystems. Swards of Lolium perenne were grown from seed in a Eutric Cambisol at either ambient (ca. 350 μmol mol−1) or elevated (700 μmol mol−1) atmospheric pCO2 and subjected to two inorganic N fertilizer regimes (no added N and 70 kg N ha−1 month−1). After germination, soil solution concentrations of dissolved organic C (DOC), dissolved inorganic N (DIN), dissolved organic N (DON), phenolics and H+ were measured at five depths down the soil profile over 3 months. The exploration of soil layers down the soil profile by roots caused transient increases in soil solution DOC, DON and phenolic concentrations, which then subsequently returned to lower quasi-stable concentrations. In general, the addition of N tended to increase DOC and DON concentrations while exposure to elevated pCO2 had the opposite effect. These treatment effects, however, gradually diminished over the duration of the experiment from the top of the soil profile downwards. The ambient pCO2 plus added N regime was the only treatment to maintain a notable difference in soil solution solute concentration, relative to other treatments. This effect on soil solution chemistry appeared to be largely indirect resulting from increased plant growth and a decrease in soil moisture content. Our results show that although plant growth responses to elevated pCO2 are critically dependent upon N availability, the organic chemistry of the soil solution is relatively insensitive to changes in plant growth once the plants have become established.  相似文献   

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