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1.
Strains of Rhizobium trifolii incorporated into commercial peat inoculants were compared for their effect on the establishment and growth of oversown white clover (Trifolium repens) on soils devoid of infective rhizobia.There were marked differences in numbers of seedlings establishing and clover dry matter production per hectare with the various strains. However, when adjusted to a constant number of established seedlings, dry matter production from all strains, apart from one strain at one site, were similar indicating that the strains did not appear to influence the growth of individual clover plants.The marked differences in establishment of clover inoculated with the various strains could not be accounted for by differences in the number of rhizobia in the peat inoculant.Selecting strains of rhizobia for ability to increase establishment is considered important where clover is oversown onto soils devoid of rhizobia.  相似文献   

2.
Pinus radiata seedlings were inoculated with basidiospores of Rhizopogon roseolas and Suillus granulatus, and with chlamylospores of two unidentified but highly effective mycorrhizal fungi in undisturbed cores of natural soil fumigated with methyl bromide. Fumigation stimulated mycorrhizal infection rate and enhanced the response of seedlings to increasing concentrations of both inoculum types, but the effect of chlamydospore inoculum was more favoured by fumigation than that of basidio-spores. Chlamydospore inocula appear more sensitive to competitive and antagonistic soil microorganisms than basidiospores. Soil fumigation appears a necessary adjunct to the use of chlamydospores as inoculants in nurseries and is discussed in relation to nursery culture of pines.  相似文献   

3.
The most common method of inoculating legume crops in Australia is the application of peat slurry inoculant to seed. The recent introduction of granular (solid) formulations of inoculants into the Australian market has provided the potential to apply rhizobia with greater ease, but their efficacy has not been independently evaluated. Here, we compare the efficacy of a range of experimental and commercially-available granular inoculants on chickpea, faba bean, lentil, lupin and pea crops in comparison with un-inoculated treatments, and with conventional seed-applied peat slurry inoculants. Thirty-seven field experiments were established in Victoria, South Australia and southern New South Wales over five years. Peat slurry inoculants provided effective nodulation of all legumes. Granular inoculants varied markedly in their ability to improve grain legume nodulation. The size of response depended inversely on background nodulation from soil rhizobial populations. At sites with median background nodulation, peat granules and attapulgite clay granules placed with seed resulted in nodulation similar to peat-slurry-based inoculation, but treatments with bentonite clay granules did not increase nodule numbers much above those in un-inoculated treatments. The generally lower numbers of rhizobia g−1 in the bentonite granules, translated to lower rhizobia application rate to the soil. However, differences in number of rhizobia g−1 granule did not fully explain the nodulation differences between granules. Granule moisture content and granule particle size differed markedly between granule types but their influence on nodulation was not tested. Grain yields did not differ between attapulgite granules placed with seed, peat granules and peat slurry inoculants (all well-nodulated treatments), but were lower with bentonite granule inoculants. Yield differences within sites were related to nodulation and the differences between treatments attenuated as background nodulation increased. Overall, these studies demonstrate that certain granule types have the potential to be used in Australia with grain legumes, particularly in circumstances when seed-applied inoculants are problematic, such as where seed fungicides or insecticides need to be applied. However, granular inoculant formulations differ substantially in their potential to produce nodules on a range of grain legumes.  相似文献   

4.
A series of inoculation experiments was conducted in glasshouses in Senegal and Kenya to evaluate inoculation procedures designed to optimise nodulation and N2 fixation of Calliandra calothyrsus Meisn. seedlings. Nodulation and plant growth were used as indices of inoculation success. In an experiment carried out in sterile peat/vermiculite mixture, it was established that inoculation of C. calothyrsus with an effective rhizobial strain at the low rate of 1᎒2 rhizobia per seedling was satisfactory for nodulation and growth, but further response occurred at rates of up to 1᎒9. A second experiment in (unsterilised) Sangalkam soil (Senegal) containing indigenous rhizobia demonstrated that the most successful form of inoculation was liquid inoculant applied around the root collar immediately after transplanting. This method was more successful than seed inoculation or application of alginate bead inoculant. A third experiment was conducted using filtermud inoculant in Leonard jars and unsterilised Muguga nursery soil from Kenya, containing a large population of indigenous rhizobia. Application of liquid inoculant to seedlings was better than seed inoculation. On the basis of our study, we recommend that C. calothyrsus seedlings raised in the nursery should be inoculated with a liquid inoculant immediately or soon after germination.  相似文献   

5.
Fungal sporocarps of Hydnangium carneum Wallr., Laccaria laccata (Scop. ex Fr.) Berk. ex Br., Scleroderma spp, Hymenogaster spp., Hysterangium spp, Cortinarius spp, etc. were found to be associated with five species of eucalypts Eucalyptus delegatensis R.T. Bak., E. regnans F. Muell., E. nitens Maiden, E.fastigata Deane et Maiden, and E. saligna Sm.) in nurseries or stands in the North Island of New Zealand.A total of 5345 mycorrhizal pieces were plated out in isolation studies. More than 47% of these pieces remained free of fungal outgrowth, 16% yielded dark sterile mycelia, 7% yielded hyaline sterile fungi, 17% produced sporing Fungi Imperfecti, 5.8% were basidiomycetous fungi identified as H. carneum, Scleroderma spp, Paxillus sp. and Hymenogaster albus (Klotzsch) Berk. et Br., and 5.9% were unidentified basidiomycetes.Mycorrhizas were synthesized on eucalypt seedlings by 12 identified basidiomycetes which form sporocarps in eucalypt stands and 12 unidentified basidiomycetes isolated from the mycorrhizas. Under the test conditions two Cortinarius spp and one unidentified basidiomycete did not form mycorrhizas.The results indicate a possible importance of H. carneum as a mycorrhizal fungus of eucalypts in the North Island of New Zealand.  相似文献   

6.
Large scale experiments with inoculated and drill sown Trifolium subterraneum, T. hirtum, and T. cherleri showed that recent isolates of Rhizobium trifolii from healthy plants in problem pastures were superior to the strains used in commercially available inoculants. The new rhizobia are also shown to persist in the soil longer than the commercial strains. Evidence was obtained of different levels of performance by R. trifolii strains on different soils. Following the inclusion of one of the superior isolates in commercial peat inoculants, a number of farmer-sown pastures were examined for strain persistence. The new isolates showed much improved persistence over the older inoculant strains.  相似文献   

7.
Controls on the colonization and abundance of arbuscular mycorrhizal fungi (AMF) in ecosystems are little understood and may be related to host factors, the fungal community, and soil physio-chemical properties; and changes in these variables during soil development may affect succession between mycorrhizal groups. Here we investigated the effects of litter, litter leachates, and common soluble phenolic compounds on AMF colonization of roots. In previous studies, we observed a negative correlation between increases in black cottonwood (Populus trichocarpa) litter and AMF abundance and inoculum potential along a riparian chronosequence in northwest Montana. From this, we hypothesized that litter inputs negatively affect the native AMF community and may contribute to the shift between AMF and ectomycorrhizas. We tested the effects of cottonwood foliage and litter extract additions on the colonization of AMF of both cottonwood and Sudan grass (Sorghum sudanese) seedlings. Addition of 5% (v/v) dried cottonwood leaves completely inhibited AMF colonization of S. sudanese. AMF colonization of S. sudanese was significantly reduced by litter extract of P. trichocarpa foliage, and colonization was negatively correlated with litter extract concentrations. Additions of aqueous litter extract significantly reduced AMF colonization of cottonwood seedlings as well. The effect of the litter extract on AMF colonization of S. sudanese did not appear to be mediated by changes in soil pH or plant biomass. Available phosphorus was higher in soil receiving highest concentration of litter extract, but not at a level expected to be inhibitory to AMF colonization. Litter additions significantly increased total soil phenolics, but with a range similar to natural soils of the Nyack floodplain. We tested pure soluble phenolic compounds common to Populus for their effect on AMF colonization by native fungi from the Nyack floodplain. All tested compounds significantly reduced AMF colonization but did not affect colonization by non-AMF root-colonizing fungi. This suggests secondary compounds present in cottonwood litter can affect colonization ability of a native AMF community. The potential mechanisms of inhibition and the relevance of these findings to AMF succession within both a single host and soil are discussed.  相似文献   

8.
《Applied soil ecology》2007,35(1):174-183
An increasing amount of evidence shows the context dependent nature of various biotic interactions across terrestrial and aquatic ecosystems. We established a laboratory experiment to study whether the effects of Cognettia sphagnetorum (Enchytraeidae) and ectomycorrhizal fungi on Scots pine (Pinus sylvestris) seedling growth are influenced by wood ash application. Acidic coniferous forest soil was treated with wood ash at 5000 kg ha−1 or left as ash-free control and inoculated with soil saprotrophic microbes and nematodes. The microcosms were destructively sampled 26 and 51 weeks after initiation of the experiment. We measured enchytraeid and pine seedling biomass, abundance of nematodes and leaching of NH4+-N and NO3−-N at both samplings, and root length and N concentration of pine needles at the end of the experiment. On average enchytraeids and mycorrhizal fungi enhanced pine biomass production in the ash-free control soils, however, their impact was most pronounced when these organisms were alone in the systems. In fact, mycorrhizas tended to have a negative impact on the seedlings in the presence of enchytraeids. Wood ash had a clear negative impact on enchytraeid populations. Wood ash decreased pine growth when enchytraeids and EM-fungi were alone in the systems, but when together they apparently compensated for the negative effects of wood ash on the seedlings. It is concluded that interactions between soil fauna, mycorrhizal fungi and plants are context dependent, thereby rendering predictions of the outcome of species interactions in soil food webs a demanding task.  相似文献   

9.
The impact of plant growth-promoting rhizobacteria (PGPR) inoculants on the growth, yield and interactions of spring wheat with arbuscular mycorrhizal fungi (AMF) was assessed in field studies. The pseudomonad inoculants P. cepacia R55, R85, P. aeruginosa R80, P. fluorescens R92 and P. putida R104, which enhance growth and yield of winter wheat, were applied at a rate of ca. 107–108 cfu seed-1 and plots established on pea stubble or summer fallow at two different sites in Saskatchewan. Plant shoot and root biomass, yield and AMF colonization were determined at four intervals. Plant growth responses were variable and dependent on the inoculant strain, harvest date and growth parameter evaluated. Significant increases or decreases were measured at different intervals but these were usually transient and final seed yield was not significantly affected. Harvest index was consistently increased by all pseudomonad inoculants; responses to strain R55 and R104 were significant. Root biomass to 60 cm depth was not significantly affected by inoculants except strain R104, which significantly reduced root dry weight. However, root distribution, root length and AMF colonization of roots within the soil profile to 60 cm were significantly altered by inoculants. Most of these responses were reductions in the assessed parameter and occurred at depths below 15 cm; however, strains R85 and R92 significantly increased root dry weight in the 0- to 15-cm zone. These results indicate that some PGPR inoculants may adversely affect mutualistic associations between plants and indigenous soil microorganisms, and suggest a possible reason as to why spring wheat growth was not consistently enhanced by these pseudomonad PGPR.  相似文献   

10.
The objectives of this study were (1) to investigate effects of soil acidity on the formation of mycorrhizas in ash and sycamore, and (2) to elucidate if mycorrhization can improve the acquisition of Ca, Mg, and P by these tree species. Soil substrates with different Ca, Mg, and Al saturation were used in pot experiments with mycorrhizal ash and sycamore seedlings and various Ca and Mg fertilization treatments. The development of vesicular‐arbuscular‐mycorrhizas (VAM) in both species was considerably affected by the chemical soil properties and by the nutritional status of the plants. Mycorrhizal fungi developed well only in plants growing on basalt‐derived, Ca and Mg rich loam and in substrates fertilized with Ca and Mg carbonate. In these substrates, the pH value, Ca and Mg supply and growth of the plants were optimal. The mycorrhizas degenerated in an acid loam derived from phyllite, in tertiary sand and in all treatments receiving Ca and Mg sulfate. Ash and sycamore suffered from Ca and Mg (P) deficiency, and partly from Al antagonism against Ca and Mg uptake (sycamore) or Al toxicity (ash). The symbiosis between fungi and the plants was disrupted since the tree species and the VAM fungi (from fertile nursery soils) did not adapt to the acidic experimental soil substrates with high Al activity. Consequently, the fungi lost their function of supporting the plants by improved nutrient uptake and the plants likely did not produce enough organic substances for the fungi. In addition, N fertilization possibly suppressed the development of VA mycorrhizas and inhibited new colonization in acid substrates.  相似文献   

11.
Interactions between eight ectomycorrhizal fungi and eight bacteria were tested on five laboratory media and in the rhizoplane of Pinus radiata. Depression of growth of the fungi by the bacteria in laboratory media was dependent on the medium and bore little relation to effects in the rhizoplane. In the rhizoplane, different bacteria could depress, have no effect or even stimulate growth of mycorrhizal fungi. Competition and antagonism are suggested as mechanisms for depression of the fungi. Some bacteria gave protection against the depressive effects of other bacteria. Considerable differences occurred between ectomycorrhizal fungi in their colonization of the rhizoplane in the absence of bacteria and also in their presence. The common mycorrhizal fungi Rhizopogon luteolus and Thelephora terrestris generally colonized roots well but the strain of Pisolithus tinctorius studied colonized poorly. Direct microscopy showed the percentage cover of the root by microorganisms was usually only 10–20%.It is proposed that interactions of ectomycorrhizal fungi with soil organisms are important in determining the successful introduction and persistence of inoculated ectomycorrhizal fungi. Fungi should be selected for compatibility with a wide range of soil microflora as well as efficiency in plant stimulation.  相似文献   

12.
[目的]分析PT菌剂对陕北黄土区土壤性质和油松苗木的影响,为干旱和半干旱黄土高原植被恢复提供科学依据。[方法]在陕西黄土高原丘陵区采用完全随机区组试验(2013年3—10月),以常规施肥为对照,以上、中、下3个坡位为区组,研究施用PT菌剂对6年生油松苗木地径、树高、成活状况以及0—60cm这3个不同层次土壤主要养分含量的影响。[结果]施用PT菌剂油松地径平均生长量为4.5mm,是对照的2倍;树高总生长量达10cm,比对照高54%;油松死亡率比对照低9%。施用PT菌剂后土壤有机质含量平均达到7.8g/kg,是对照的2倍多;土壤全氮的含量平均为0.41g/kg,比对照高52%;速效钾的含量平均达到42.4mg/kg,比对照增加了26%;PT菌剂对有效磷提高不明显;坡位对油松地径和树高影响不显著,对各层次土壤养分性质有显著影响。[结论]PT菌剂能改善造林地土壤性质,促进油松成活和生长,建议在黄土高原地区油松造林实践中施用PT菌剂。  相似文献   

13.
Addition of superphosphate at 40 kgP/ha greatly increased yield in seedlings of Pinus radiata D. Don, and P. elliottii Little and Dorman on two soils lacking fungi capable of forming mycorrhizas with Pinus. P could be partially replaced by increasing inoculum density or avoiding delay in inoculation. Chlamydospores were less effective than basidiospores as inoculum, and there were highly significant differences in yield produced by different fungal species at high inoculum densities and in the presence of added P. These effects are discussed with respect to the intensity of mycorrhizal infection and postulated differences in sensitivity to microbial competition and antagonism.  相似文献   

14.
On two soils lacking fungi capable of forming mycorrhizas with Pinus, the addition of superphosphate at 40 kgP/ha greatly increased mycorrhiza formation in Pinus radiata D. Don and P. elliottii Little and Dorman. Phosphorus could be partially replaced by increasing inoculum density or avoiding delay in inoculation after sowing. Chlamydospores were less effective than basidiospores as inoculum except at the highest density and in the presence of added P. At low available P concn such as are common in Australian soils, the normal pattern of infection of new short roots is interrupted and re-infection from the soil is of greater importance. Survival of mycorrhizal fungi in the soil in the absence of the host may therefore be a critical factor in inoculation programs.  相似文献   

15.
粘土矿物中钾的生物活化: Ⅰ. 外生菌根   总被引：1，自引：0，他引：1  
A pot experiment was Carried out to in vestigate effect of ectomycorrhizal fungi on eucalyptus growth and K bio-mobilization from soils and clay minerals,In the experiment,sands mixed with soil,KCl-satureated vermiculate and mica,respectively,were used to nurse eucalypus seedings which were nonectomycorrhized or ectomycorrhized by an ectomycorrhizal fungus Pisolithus tinctorius strain XL1(Pt XC1) isolated from a forest soil from Xichang,Sichuan Province,China,and a worldwide well-know ectomycorrhial fungus Pioslithus tinctorius strain 2144(Pt 2144) obtained in Australia.More depletion of HCl-souluble K by mycorrhizas from the soil and minerals than nomycorrhizas suggested that mycorrhizas had a great ability to mobilize K present in the interlayer and feldspar.Mycorrhizal seedlings depressed greatly K digested with HF-HClO4 from substrates after consecutive extractions of soils and minerals by water,ammonium acetate and boiling HCl,while nonmycorrhizal seedlings reduced it little if any,shwing that the mycorrhizal seedlings could mobilize and then utilize the structureal K in mineral lattice,Ectomycorrhizal fungi played a very important role not only in promoting the growth of eucalyptus seedlings but also in mobilizing K in soils and minerals.The infection of Pt XC1 led to a better growth of eucalyptus seedlings and more K accumulation in the seedlings than that of Pt 2144.The large differeces in K accumulation by the seedlings might be due to different abilityes of the two ectomycorrhizal fungi to mobilize K in intelayer and lattice pools in the clay minerals.  相似文献   

16.
Abstract

The influence of the addition of Chinese peat and Canadian peat on arbuscular mycorrhizal colonization, mycorrhizal effectiveness and host-plant growth was investigated in a pot experiment. Chinese peat or Canadian peat was mixed with Masa soil (weathered granite soil) at different levels (0, 25, 50, 100, 150 or 200 g kg?1) into which an arbuscular mycorrhizal fungus (AMF) Gigaspora margarita Becker & Hall was inoculated, and seedlings of Miscanthus sinensis Anderess were planted. There was a significant increase in plant growth with increasing amounts of Chinese peat. The growth-promoting effect of the AMF on the host was enhanced when the addition of Chinese peat was increased from 25 to 100 g kg?1. Root colonization and the number of spores proliferating increased with increases at low levels of Chinese peat (from 25 to 100 g kg?1), and decreased gradually with higher Chinese peat increments. Although plant growth and root colonization with the addition of Canadian peat increased slightly, Canadian peat suppressed mycorrhizal effectiveness. In contrast to Canadian peat, the addition of Chinese peat improved considerably the physical and chemical properties of the soil, which might result in the promotion of AM formation and mycorrhizal effectiveness.  相似文献   

17.
Pre-inoculation of seedlings with commercial, typically non-indigenous, AMF inoculants is common practice in horticultural and land reclamation industries. How these practices influence AMF community composition in pre-inoculated seedlings after they are planted in soil containing a resident AMF community is almost completely unknown. However, there may be important implications regarding success of horticultural practices, as well as unexpected ecological consequences. In this study we exposed Leucanthemum vulgare seedlings to five different AMF treatments (pre-inoculation with a representative of Glomus group A and Glomus group B, one of two Gigaspora spp., or no AMF) prior to exposure to a whole-soil, mixed-AMF community inoculum. After a growth period of 75 additional for 28 days, AMF community composition within the roots was analyzed using an approach combining LSU rDNA sequencing and T-RFLP analysis. Our results indicate that the AMF communities that assemble within roots were strongly influenced by AMF pre-inoculant identity. Pre-inoculation with either Glomus spp., unlike what was found for Gigaspora, greatly restricted numbers of other AMF ribotypes able to subsequently colonize roots after exposure to our Glomeraceae-dominated field soil; this suggested that phylogenetic relatedness and life history strategies may play a role in AMF community assembly. Our results further revealed concurrent changes in AMF community functions, as indicated by differences in plant biomass and foliar nutrients. These results serve to highlight the importance of considering life history differences when designing AMF inoculants and may have important implications regarding the introduction of non-indigenous AMF.  相似文献   

18.
《Applied soil ecology》2007,35(1):10-20
Colonization by and diversity of arbuscular mycorrhizal (AM) fungi associated with five common ephemerals, Eremopyrum orientale (L.) Jaub. et Spach., Gagea sacculifera Regel., Plantago minuta Pall., Tragopogon kasahstanicus S. Nikit., and Trigonella arcuata C. A. Mey. were investigated in four typical desert plant communities in Junggar Basin, northwest China. All five ephemerals examined were found to be colonized and formed typical arbuscules or vesicles. The proportion of root length colonized ranged from 2 to 85% with an average of 19%. Spore density in soil near the roots of different ephemerals varied from 1 to 120 spores per 20 ml soil, with an average value of 33 spores. Species richness averaged 8.8 AM fungal species in soil near the roots and ranged from 2 to 21. Fifty-four AM fungal taxa belonging to the genera Acaulospora, Archaeospora, Entrophospora, Glomus and Paraglomus were isolated and identified from soil around the roots. Glomus was the dominant AM fungal genus with a frequency of 100% and relative abundance of 82.6%. The AM fungal species with the highest frequency of occurrence was Glomus aggregatum with a frequency of 75%. G. microaggregatum was present in the highest relative abundance (16%). G. sacculifera, P. minuta and T. arcuata formed Arum-type mycorrhizas. Arbuscular mycorrhizal fungi are ubiquitous and Arum-type mycorrhizas are especially prevalent in these important desert communities used for grazing and traditional medicine.  相似文献   

19.
While it is well established that plants are able to acquire nitrogen in inorganic form, there is less information on their ability to ‘short circuit’ the N cycle, compete with microbes, and acquire nitrogen in organic form. Mycorrhizal fungi, known to enhance nutrient uptake by plants, may play a role in organic N uptake, particularly ericoid mycorrhizas. We asked the question—Can mycorrhizal fungi increase the ability of plants to take up organic N, compared to inorganic N? Here, we report on the abilities of three plant species, ericoid mycorrhizal Rhododendron macrophyllum and Vaccinium ovatum and arbuscular mycorrhizal Cupressus goveniana ssp. pigmaea, to acquire C and/or N from an organic and an inorganic N source. All three species are native to a California coastal pygmy forest growing in acidic, low-fertility, highly organic soils. In a pot study, glycine-α13C, 15N and 15N-ammonium were applied to pygmy forest soil for 17 or 44 h. Ericoid mycorrhizal species did not demonstrate a preference for either inorganic or organic sources of N while Cupressus acquired more NH4-N than glycine-N. For all species, glycine-N uptake did not increase after 17 h suggesting glycine uptake and glycine immobilization occurred rapidly. Both glycine-N and glycine-C were recovered in shoots and in roots suggesting that all species acquired some N in organic form. Regression analyses of glycine-N and glycine-C recovery in root tissue indicate that much of the glycine was taken up intact and that the minimum proportion of glycine-N recovered in organic form was 85% (Cupressus) and 70% (Rhododendron). Regressions were non-significant for Vaccinium. For all species, glycine-N remained predominantly in roots while glycine-C was transferred to shoots. In contrast, NH4-N remained in roots of ericoid plants but was transferred to shoots of arbuscular mycorrhizal Cupressus. Since net N mineralization rates in pygmy forest soils are low, our results suggest that organic N may be an important N source for plants in this temperate coniferous ecosystem regardless of mycorrhizal type. Acquisition of amino acid C by these species also may partially offset the carbon cost to plants of hosting mycorrhizal fungi.  相似文献   

20.
Attempts were made to isolate mycorrhizal fungi of a timber species, Pseudotsuga menziesii (Mirb.) Franco which is exotic to New ZeaLond. Over 2000 pieces of mycorrhizal roots were plated out on Hagem medium and modified Melin-Norkrans medium; 14% of these yielded Rhizopogon vinicolor A. H. Smith, 6% gave rise to Amanita muscaria (L. ex Fr.) S.F. Gray, and 7% to unidentified basidiomycetes, 21% yielded dark sterile mycelia, 13% were sporing Fungi Imperfecti presumed to be contaminants, and 39% remained free of fungal growth.Eleven basidomycetous fungi were tested for their mycorrhiza-forming ability on P. menziesii seedlings. Under the test conditions R. vinicolor, Hebeloma crustuliniforme (Bull, ex St. Am) Quel., A. muscaria, Scleroderma bovista Fr., Laccaria laccata (Scop, ex Fr.) Berk. & Br., Inocybe corydalina (?), I. jurana (?), and I. maculata (?) formed mycorrhizas.  相似文献   

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