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1.
The infection and survival of sclerotia of Sclerotinia minor and the production ofmacroconidia of the mycoparasite, Sporidesmium sclerotivorum, were studied in vitro when each fungus was added to soil at various initial inoculum densities. The rate at which S. sclerotivorum invaded host sclerotia and caused their decay varied with the amount of the mycoparasite added to soil. The results suggest that approximately 5 macroconidia of the mycoparasite g?1 of soil are needed to successfully infect sclerotia and bring about their decay, when soils are sampled and mixed every 2 weeks. The rate at which S. sclerotivorum infects sclerotia of S. minor and causes their decay is also dependent on the initial inoculum density of the host. Each infected sclerotium supports the production of about 15,000 new macroconidia in soil regardless of the initial inoculum density of the host. It is concluded that successful biological control by S. sclerotivorum is dependent on the soil population of both the host and the mycoparasite.  相似文献   

2.
Bacteria, Pseudomonas paucimobilis, were inoculated at two concentrations (6.56 × 104 g?1 and 6.56 × 106g?1) into sterilized soil amended with 700 μg glucose-C g?1. Two levels of NH+4-N (11.0μg g?1 and 81.0 μg g?1) were used. The subsequent development was followed for three days by measurement of several biological, chemical and physiological parameters.The amount of bacterial biomass-C (μg g?1 soil) became twice as great in high as in low N treatments, and significantly decreased between 39.5 and 63.5 h for the high inoculum, high N level treatment due to decreasing cell size. By the end of the experiment the cumulative respired carbon was twice as great and more inorganic P was immobilized for high compared to low N treatments and all available NH+4-N was taken up by the final sample time. Soil ATP concentrations were twice as large in high N treatments but the turnover times were twice as long compared to low N systems. The yield coefficient (Y), calculated from respiration and biomass-C values, equalled 0.61 while substrate was plentiful. Nitrogen limitation did not alter the efficiencey with which glucose was transformed into biomass, but rather controlled the total amount of glucose used and biomass produced.  相似文献   

3.
Isolates of Trichoderma spp grew and produced chlamydospores as well as conidia in molasses-corn steep liquor (M-CSL), sucrose nitrate (SN), and glucose tartrate (GT) media. In M-SCL, isolates of T. hamatum, T. viride, and T. harzianum formed 10.4, 5.9 and 1.1 × 108 chlamydospores g?1 dry weight of mycelium. Fewer chlamydospores formed in SN and GT. Although T. harzianum formed the least number of chlamydospores, it produced the highest number of conidia in all three media. Molasses-corn steep liquor was superior to SN or GT in supporting development of both spore types. Spore production was not influenced by initial pH of the media or by continuous maintenance of the media at pH 4 or 7. Equal numbers of chlamydospores were formed in liquid media incubated in shake or static culture. Conidia formation, however, was stimulated in static culture. Chlamydospores and conidia of several naturally occurring isolates and induced biotypes of Trichoderma spp were abundantly produced on a variety of solid substrates moistened with liquid nutrients or water, preferably at pH 4. Bran, cornmeal, and peanut hull meal were better than eight other solid substrates for production of chlamydospores and conidia. A u.v.-induced, benomyl-resistant biotype of T. viride (T-1-R9) formed 22 × 107 and 18 × 108 chlamydospores and conidia, respectively, g?1 of bran-SN. The ratio of conidia to chlamydospores was always greater in solid than liquid media. In solid media, 10 times more conidia than chlamydospores were formed, whereas in liquid only two or three times more were formed. Chlamydospores from liquid and solid fermentations were viable (ca 80%) and fresh chlamydospores germinated well (ca 75%) on nutrient agar. Although dried chlamydospores were viable, as determined with tetrazolium bromide, their germination on agar was poor (ca 8%).  相似文献   

4.
The development and survival of the mycoparasite Coniothyrium minitans associated with sclerotia of the plant pathogen Sclerotinia sclerotiorum was studied in pasteurised and non-sterile (untreated) soil. Using scanning electron microscopy, developing pycnidia were first seen within the sclerotial medulla at 7 days post-inoculation with the mycoparasite in pasteurised soil. However, by 14 days post-inoculation, pycnidia had developed fully in both pasteurised and non-pasteurised treatments, and conidial droplets were exuded onto the outer surface of the infected sclerotia. Thirty days post-inoculation, irrespective of soil treatment, the majority of the sclerotial medulla had been converted to pycnidia, with the sclerotial rind remaining largely intact. The pycnidia and dried intact droplets were still observed 6 months post-inoculation with C. minitans, although the conidia on the outer surface of the dried droplets had largely collapsed by this stage. Germinability studies at 10 months post-inoculation showed that approximately 13% of the conidia in dried droplets were still viable. This work shows the potential for infected sclerotia of S. sclerotiorum to provide a unique reservoir for the survival of C. minitans.  相似文献   

5.
The mycelial biomass of fungi decomposing plant materials may be estimated by use of a chitin (hexosamine) assay technique. A method is described together with a discussion of its limitations; whatever the sensitivity of the chemical analysis the validity of the biomass estimate rests on the reliability of the conversion from chitin determination to mycelial dry weight. Estimates made on mycelium of Coriolus versicolor during decay of sawdust from Castanea sativa show a constant increase in biomass. The economic coefficient derived is 47 per cent which is similar to that for the utilization of glucose in liquid culture. Estimates of production are not possible due to lack of information concerning rates of hyphal death and autolysis. The estimated extents of mineral nutrient immobilization are 39% for N, 37% for P and 95% for K.  相似文献   

6.
Nocardiae were isolated from 15 out of 47 soils using Diagnostic Sensitivity Test Agar supplemented with antibiotics. Up to 7.3 × 104 g?1 dry wt. soil were counted, indicating that these bacteria might be more widespread and important than previously thought. Study of randomly selected isolates showed that they formed fragmenting mycelium, contained arabinose, galactose, meso-diaminopimelic acid and nocardomycolic acids. They clustered with Nocardia asteroides markers in a numerical taxonomic analysis.  相似文献   

7.
Mulching of Macrophomina phaseolina-inksted soil (moist or dry) with transparent polyethylene sheets during the hot days of May increased temperature of wet soil at 5 cm from 37°C (unmulched) to 52°C (mulched) and of dry soil from 52°C (unmulched) to 65°C (mulched). At 20 cm mulching increased temperature from 30°C to 41°C (wet) and from 38°C to 42°C (dry). In artificially-infested soil. the sclerotia of M. phaseolina were eradicated at 5 cm by a mulch treatment for 1 week and at 20 cm depth 50% sclerotia lost viability in wet soil but were not affected in dry soil. In a naturally infested soil (5–7 sclerotia g?1), which gave 20% infection on Vigna, the sclerotia were reduced to such an extent that after 1 week mulching no disease was observed on Vigna.  相似文献   

8.
The population and distribution of sclerotia of Rhizoctonia solani Kühn in two sugar beet field soils was determined at harvest by a sieving-flotation method. In rhizosphere soil (RS) and non-rhizosphere soil (NRS) from the most heavily infected roots of sugar beets, 1.43–2.5 and 0.83–1.0 sclerotia g?1 dry soil were detected, respectively. In the soil around healthy sugar beet, these values were 0.04–0.12 and 0.03–0.04 sclerotia g?1 dry soil. More sclerotia were always obtained from RS than from NRS. More than 80% of the sclerotia were in the upper 10 cm of soil and within 10 cm of diseased roots. Therefore, there is a non-uniform distribution of sclerotia of R. solani in soil.The sclerotial population in soil increased significantly with disease severity and a good correlation was obtained between the number of sclerotia and the disease severity on infected plants. Most of the sclerotia collected from the field soil ranged in size from 0.5 to 2.0 mm diameter.Viability of sclerotia increased as severity of crown rot increased and as the size of the sclerotia increased. Conversely, there was a progressive decrease in sclerotial germination with increasing depth in soil and increasing distance from the infected root.  相似文献   

9.
Cr(III) ions sorption onto sawdust of spruce (Picea smithiana) has been studied thoroughly using radiotracer technique. Maximum sorption (94%) of Cr(III) ions (8.98×10?5 M) onto sorbent surface is achieved from deionized water in 20 min agitation time using 200 mg of sawdust. The sorption data followed the Freundlich, Dubinin-Radushkevich (D-R) and Langmuir isotherms. Freundlich constants l/n = 0.86 ± 0.07 and C e = 85.0 ± 25.8 mmole g?1 have been estimated. Sorption capacity, X m = 0.82± 0.3 mmole g?1, β = ?0.00356± 0.00017 kJ2 mole?2 and energy, E = 11.9± 0.3 kJ mole?1 have been evaluated using D-R isotherm. The Langmuir constants Q = 5.8± 0.2 μmole g?1 and b = (7.4± 0.5)×104 dm3 mole?1 have been calculated. The variation of sorption with temperature yields thermodynamic parameters Δ H = ?11.6± 0.3 kJ mole?1, Δ S = ?16.2± 0.9 J mole?1 K?1 and Δ G = ?6.8± 0.3 kJ mole?1 at 298 K. The negative value of enthalpy and free energy reflect the exothermic and spontaneous nature of sorption respectively. Among the anions studied oxalate, citrate, carbonate and borate have reduced the sorption. The cations Y(III), Ce(II) and Ca(II) suppressed sorption. The sawdust column can be used to separate Cr(III) ion from Cs(I), I(I),Tc (VII) and Se (IV).  相似文献   

10.
The side effects of fluazifop-butyl on soil fungal populations and oxygen uptake were studied by incubating soil samples with a range of fluazifop-butyl concentrations (0, 0.6, 3 and 6 μg g?1) over 8 weeks. Cellulose decomposition in soil was also studied in laboratory experiments with the herbicide which was either incorporated in soil or sprayed onto calico squares which were buried in soil. The mycelial dry weight of six fungal species under the effect of the herbicide was also examined. Fluazifop-butyl had no significant effect on total fungal propagule populations at 0.6 μg g?1. At 3 and 6 μg g?1, it caused temporary reduction in fungal populations observed after 1 and 2-wk of incubation. The herbicide had no significant effect on OZ uptake. The decay of calico buried in herbicide-treated soil was generally stimulated, while the decomposition of herbicide-treated calico, buried in untreated soil, was temporary delayed. The mycelial dry weight yields of Aspergillus favus (at 2 and 12 μg mL?1 of fluazifop-butyl) and Cunninghamella echinulata (at 12 μg mL?1) were significantly increased. At 24 μg mL?1 the mycelial dry weight of A. flavus and Alternaria alternata was significantly reduced.  相似文献   

11.
The weight of mycelium of Stereum hirsutum has been estimated by the hexosamine-assay method for 15 branches of oak. The branches showed states of decay varying between 20 and 70% weight loss. Up to about 40% weight loss the mycelial weight per unit volume increased but the later stages were typified by a decrease presumed to be due to the predominance of mycelial decay in this phase. Nutrient limitation may have been responsible for the change in kinetics. The estimated yield coefficient for the early stages of decay was 0.32 g-g?1.  相似文献   

12.
We examined collembolan food preference for fungal mycelium grown on copper-contaminated medium, and the relationship between copper content, food selectivity and collembolan fitness when fed contaminated mycelium.To clarify whether collembolan food selectivity is related to fitness parameters, Folsomia candida were fed mycelium of the dark-pigmented fungus Alternaria alternata grown on medium with different copper concentrations. Copper-contaminated food (fungus grown on 50, 125, 250 and 500 μg Cu g?1 medium, fresh wt.) was offered together with untreated food for 4 weeks. F. candida fed selectively on the provided mycelium and discriminated clearly between mycelium grown on high and low levels of contamination, distinctly preferring fungus grown on medium with a total copper concentration of 50 and 125 μg g?1. In contrast, fungus grown on highly contaminated medium (250 and 500 μg g?1) was avoided. Collembolan food preference generally matched fitness parameters. Reproduction was significantly affected by the total copper concentration of the fungal growth medium. When fed their preferred mycelium, collembolan reproduction was enhanced, whereas a diet of highly contaminated mycelium (250 or 500 μg g?1) resulted in a strong decrease in reproduction. Adult survival was affected only marginally. Even though heavy metal contamination is a potential stress factor for many soil microarthropods, F. candida is able to discriminate between high and low quality food sources, and even benefits from moderately elevated copper concentrations.  相似文献   

13.
Numbers of microorganisms in litters, soils and cryptogamic crusts are reported for deserts and semi-arid woodlands in Arizona. Bacteria numbered from 1 to 5 × 108 cells, fungi from 10 to 30m of mycelium, and protozoa from 2 to 10 × 103 cells g?1 dry wt in soils. Microbial populations were 2–3 times more abundant in litters, which were concentrated around the bases of plants and in depressions and rock crevices. Most of the protozoa were highly edaphic species, capable of passing rapidly between active and inactive metabolic states.  相似文献   

14.
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   

15.
A total of 65 surface (0–20 cm) soil samples were collected in an effort to estimate the arsenic background values in Kavala area, Northern Greece. Arsenic was extracted by HNO3 from the <200?µm grain size fraction, and its concentrations were determined in all samples by inductively coupled plasma–mass spectrometry. Arsenic concentrations were log-transformed, and log-normal probability plots (Q–Q plots) were generated. The geochemical background was calculated as the values that lie between g/d and g?×?d (g, geometric mean; d, geometric standard deviation), which are 3.5 and 25.8 mg kg?1, respectively. The baseline value (g) was 9.5 mg kg?1. With the aid of GIS software, arsenic geochemical maps of the study area were created. The majority of the arsenic elevated concentrations were found in the proximity of the industrialized zone of Kavala.  相似文献   

16.

Purpose

The dynamics and uncertainties in wetland methane budgets affected by the introduction of Alnus trabeculosa H. necessitate research on production of methane by methanogenic archaea and consumption by methane-oxidizing microorganisms simultaneously.

Materials and methods

This study investigated methane emission in situ by the closed chamber method, and methanogenic and methanotrophic communities using denatured gradient gel electrophoresis (DGGE) and quantitative PCR based on mcrA (methyl coenzyme M reductase), pmoA (particulate methane monooxygenase) genes in the rhizosphere and non-rhizosphere soils in the indigenous pure Phragmites australis T., and A. trabeculosa–P. australis mixed communities in Chongxi wetland.

Results and discussion

Methane flux rate from the pure P. australis community was 2.4 times larger than that of A. trabeculosa–P. australis mixed community in the rhizosphere and 1.7 times larger in the non-rhizosphere, respectively. The abundance of methanogens was lower in the mixed community soils (3.56?×?103–6.90?×?103 copies g?1 dry soil) compared with the P. australis community (1.47?×?104–1.89?×?104 copies g?1 dry soil), whereas the methanotrophs showed an opposite trend (2.08?×?106–1.39?×?106 copies g?1 dry soil for P. australis and 6.20?×?106–1.99?×?106 copies g?1 dry soil for mixed community soil). A liner relationship between methane emission rates against pmoA/mcrA ratios (R 2?=?0.5818, p?<?0.05, n?=?15) was observed. The community structures of the methane-cycling microorganism based on mcrA and pmoA suggested that acetoclastic methanogens belonging to Methanosarcinaceae and a particular type II methanotroph, Methylocystis, were dominant in these two plant communities.

Conclusions

The introduction of A. trabeculosa would promote the proliferation of methanotrophs, especially the dominant Methylocystis, but not methanogens, ultimately diminishing methane emission in the wetland.
  相似文献   

17.
Land-use conversion can affect the soil microbial community diversity, soil organic matter and nutrient cycling. In this study, soils within a representative land-use sequence were sampled in a subtropical region of China, including four natural forests, Altingia gracilipes Hemsl. (ALG), Cinnamomum chekiangense Nakai (CIC), Castanopsis fargesii Franch. (CAF), and Tsoongiodendron odorum Chun (TSO), and two plantations, Cunninghamia lanceolata (Lamb.) Hook. (CUL) and a citrus orchard (Citrus reticulata Blanco). The soil microbial diversity was investigated by phospholipid fatty acid (PLFA) analysis, denaturing gradient gel electrophoresis (DGGE) and real-time quantitative polymerase chain reaction (PCR). Results showed that microbial community diversity exhibited distinct patterns among land-use types. After conversion of natural forests to plantations, the amount of PLFA and the number of bacterial 16?S rRNA gene copies were reduced significantly, as well as the number of DGGE bands. The average quantity of PLFA was lower by 31% in the CUL plantation and 57% in the citrus orchard, respectively, than in natural forests. Simultaneously, the average copy numbers of the bacterial 16?S rRNA gene were significantly decreased from 8.1?×?1010?g?1?dry weight (DW) in natural forest to 4.9?×?1010?g?1 DW in CUL plantation, and 3.1?×?1010?g?1 DW in the citrus orchard. Such negative responses of soil microbes to conversion of natural forests to plantations could mainly result from decreases in soil organic carbon and necessary elements for growth during land-use conversion, as revealed by statistical analysis. Our results suggested that the soil microbial diversity was indirectly in?uenced by land-use types in the mid-subtropical mountainous area of southern China. Changes in the amount of litterfall and the soil nutrient status that resulted from land-use conversion drove these indirect changes. Furthermore, deliberate management brought negative effects on soil microbes, which is not beneficial to the sustainability of the ecosystem.  相似文献   

18.
Amending soils with glucose (5 mg g?1) resulted in an immediate increase in microbial activity and within 30 min the rates of heat output and respiration at 22° C were increased by up to 17.8 and 23.4 times, respectively. The increased rate of heat output remained stable for up to 6 h and there was good correlation with the amount of CO2 respired. The soil biomass was calculated by the method of Anderson and Domsch (1978). The rate of heat output of the biomass varied in different soils and ranged from 11.5 to 83.7 Jh?1 g?1 biomass C. In glucose-amended soils, however, the rate of heat output was much more consistent; the soils were in two groups having between 169–265 Jh?1g?1 biomass C or 454–482 J h?1 g?1 biomass C, both the latter two soils were from pasture. The increased rate of heat output from the amended soils was lower than expected from the respiration rate and the heat of oxidation of glucose, suggesting that a proportion of the CO2 respired was from catabolism of substrates other than glucose. Use of 14C-glucose confirmed that between 57–91% of the CO2 was derived from the glucose substrate.  相似文献   

19.
Soil-inhabiting fungal pathogen Fusarium oxysporum often causes severe yield losses in many crops. We investigated the effect of a plant growth-promoting fungus, Penicillium sp. EU0013 on Fusarium wilt disease. In dual culture experiments, EU0013 inhibited the growth of Fusarium wilt pathogens by producing an inhibition zone. In experiments using sterile potting medium under controlled conditions, EU0013 significantly reduced the severity of Fusarium wilt on tomato (Solanum lycopersicum L.) and cabbage (Brassica oleracea L. var. capitata). In non-sterile soil, benomyl-resistant mutants of EU0013 were selected by exposing the conidial solution of EU0013 to ultraviolet light. The selected mutant EU0013_90S isolate did not show any distinct differences from EU0013 in colony characteristics, growth rate or antifungal activity against Fusarium wilt pathogens in dual culture. The effect of EU0013_90S on tomato wilt was studied under greenhouse conditions using non-sterile soil. Two-weeks old tomato seedlings were dipped in four different concentrations of EU0013_90S conidial suspension (1?×?103, 1?×?104, 1?×?105, and 1?×?106 conidia mL–1). Seedlings were then planted in soil inoculated with either F. oxysporum f. sp. lycopersici race 1 CU1 or race 2 JCM 12575 (1?×?106 bud-cells g–1). We found the greatest disease suppression occurred when seedlings were dipped in the highest concentration of EU0013_90S conidia. This same inoculum concentration of EU0013_90S also resulted in the highest disease reduction in soil infested with JCM 12575. Higher root colonization with EU0013_90S showed a significant reduction in Fusarium wilt disease, suggesting that colonization by Penicillium sp. EU0013_90S is important for efficient biocontrol of these diseases.  相似文献   

20.
A study was made of several factors affecting the production of chlamydospores by Fusarium solani f. cucurbitae in pure culture. Lysis of macroconidia and chlamydospore formation is favoured by the absence of glucose in liquid culture media. Both low pH and addition of ammonium chloride to the culture medium reduces lysis of macroconidia and inhibits chlamydospore formation. Chlamydospores formed in media lacking glucose were produced from macroconidia in a manner resembling their formation in soil. They were examined by light and electron microscopy. When placed into natural soil, they acted as survival structures.  相似文献   

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