Mycorrhizas Mitigate Soil Replant Disease of Peach Through Regulating Root Exudates,Soil Microbial Population,and Soil Aggregate Stability

Soil replant disease is the main bottleneck interfering with tree growth of peach in soils with poor traits. A potted study was conducted to evaluate the effects of inoculation with an arbuscular mycorrhizal fungus (AMF), Acauloapora scrobiculata, on plant growth, mineral nutrients, soil enzyme activities, soil microbial populations, and root exudate compositions of peach (Prunus persica L. Batsch) seedlings grown in replant soil and non-replant soil. After 15 weeks in AMF inoculation, replant soil heavily inhibited root mycorrhizal colonization. In replant soil, AMF inoculation significantly increased shoot biomass and root phosphorus, potassium, calcium, copper, zinc, iron, and boron concentrations. Mycorrhizal peach seedlings showed a higher number of soil bacteria and total microbes but a lower number of soil fungi under replant conditions, as well higher soil urease and acid phosphatase activity and lower soil sucrase and catalase activity. Greater soil aggregate stability was observed in mycorrhiza-inoculated replant soil than in non-mycorrhizal soil due to the increase of water-stable aggregates in 2–4 mm and 1–2 mm size. In addition, a total of 92 substances were identified in root exudates, and the mycorrhizosphere had considerably more root exudate compositions. AMF inoculation had a significantly inhibitive effect on the relative abundance of allelochemical substances, including benzoic acid, benzaldehyde, diisooctyl phthalate, phenols, and sterols, while there was an increase in diphenyl-ethanedione and à-(benzoyloxy)-benzeneacetonitrile in replanted peach. It was concluded that AMF inoculation could partly mitigate soil replant disease of peach through modulating soil microbe balance, improving soil aggregate stability, and changing root exudate compositions.     

Native Grass Facilitates Mycorrhizal Colonisation and P Uptake of Tree Seedlings in Two Anthropogenic Substrates

Two microcosm experiments were conducted to study the role of extraradical mycelium (ERM) of arbuscular mycorrhizal fungi (AMF) in establishment and growth of tree species used for revegetation in anthropogenic substrates. Inoculated or non-inoculated Acer pseudoplatanus, Alnus glutinosa or Salix purpurea seedlings were grown with Calamagrostis epigejos (a grass spontaneously colonising degraded ecosystems) in two substrates (fly ash and coal mine spoil) either in direct root contact or in rhizoboxes with interaction only via ERM network. In both experiments, inoculation with AMF mostly had a positive effect on the growth of trees and increased the aggregation of fly ash. When plants grew in direct root-to-root contact, grass presence negatively affected tree growth, but it significantly improved mycorrhizal development (colonization of tree seedlings, spore number and ERM length). When grass and tree roots interacted via the ERM network, tree seedlings were successfully colonised by the ERM spreading from the C. epigejos roots. Mechanical disturbance of the ERM links between plants reduced AMF development and tree height in both substrates, but tree shoot biomass was not affected. In fly ash, inoculated, non-disturbed treatments showed significant transfer of ³²P from the grass to the tree seedlings. It can be concluded that roots of A. pseudoplatanus, A. glutinosa or S. purpurea seedlings can be colonised from the ERM network radiating from quickly growing grasses, which can act as important agents for AMF distribution and facilitate mycorrhization of planted trees. In particular for willow, grass seems to be an essential nurse plant to achieve successful root colonisation.     

Bedeutung der arbuskulären Mykorrhiza (AM) für die Schwermetalltoleranz von Luzerne (Medicago Sativa L.) und Hafer (Avena sativa L.) auf einem klärschlammgedüngten Boden

Effect of arbuscular mycorrhizal fungi (AMF) on heavy metal tolerance of alfalfa (Medicago sativa L.) and oat (Avena sativa L.) on a sewage-sludge treated soil In pot experiments with a sewage sludge treated soil, the influence of two arbuscular mycorrhizal fungi (AMF) isolates of Glomus sp. (T6 and D13) on plant growth and on the uptake of heavy metals by alfalfa (Medicago sativa L.) and oat (Avena sativa L.) was investigated. Alfalfa showed an increase of biomass with mycorrhizal infection only to a small extent. In oat AMF inoculation increased the growth of both root and shoot by up to 70% and 55% respectively. Mycorrhization raised the P-content and -uptake in alfalfa, but not in oat, in both roots and shoots. Mycorrhizal alfalfa showed lower Zn-, Cd- and Ni-contents and uptake in roots and shoots. The root length was significantly decreased in mycorrhizal alfalfa plants (up to 38%). The translocation of heavy metals into the shoot of mycorrhizal alfalfa was slightly increased. Mycorrhizal infection of oat led to higher concentrations of Zn, Cd and Ni in the root but to less Zn in the shoot. The translocation of heavy metals to the oat shoot was clearely decreased by mycorrhizal colonisation. This may be based on the ability of fungal tissues to complex heavy metals at the cell walls, thus excluding metals from the shoot. This conclusion is supported by the enhanced root length (up to 78%) of mycorrhizal oat plants in this experiment. The mycorrhizal infection seemed to protect plants against heavy metal pollution in soils. It was obvious that different host plants reacted in different ways.     

接种菌根真菌影响青菜中铅镉的累积和迁移

Heavy metal(HM) contamination in soils is an environmental issue worldwide that threatens the quality and safety of crops and human health. A greenhouse experiment was carried out to investigate the growth, mycorrhizal colonization, and Pb and Cd accumulation of pakchoi(Brassica chinensis L. cv. Suzhou) in response to inoculation with three arbuscular mycorrhizal(AM) fungi(AMF), Funneliformis mosseae, Glomus versiforme, and Rhizophagus intraradices, aimed at exploring how AMF inoculation affected safe crop production by altering plant-soil interaction. The symbiotic relationship was well established between pakchoi and three AMF inocula even under Pb or Cd stress, where the colonization rates in the roots ranged from 24.5% to 38.5%. Compared with the non-inoculated plants, the shoot biomass of the inoculated plants increased by 8.7%–22.1% and 9.2%–24.3% in Pb and Cd addition treatments, respectively. Both glomalin-related soil protein(GRSP) and polyphosphate concentrations reduced as Pb or Cd concentration increased. Arbuscular mycorrhizal fungi inoculation significantly enhanced total absorbed Pb and Cd(except for a few samples) and increased the distribution ratio(root/shoot) in pakchoi at each Pb or Cd addition level. However, the three inocula significantly decreased Pb concentration in pakchoi shoots by 20.6%–67.5% in Pb addition treatments, and significantly reduced Cd concentration in the shoots of pakchoi in the Cd addition treatments(14.3%–54.1%), compared to the non-inoculated plants.Concentrations of Pb and Cd in the shoots of inoculated pakchois were all below the allowable limits of Chinese Food Safety Standard.The translocation factor of Pb or Cd increased significantly with increasing Pb or Cd addition levels, while there was no significant difference among the three AMF inocula at each metal addition level. Meanwhile, compared with the non-inoculated plants, AMF inocula significantly increased soil p H, electrical conductivity, and Pb or Cd concentrations in soil organic matter in the soils at the highest Pb or Cd dose after harvest of pakchoi, whereas the proportion of bioavailable Pb or Cd fraction declined in the AMF inoculated soil. Our study provided the first evidence that AM fungi colonized the roots of pakchoi and indicated the potential application of AMF in the safe production of vegetables in Pb or Cd contaminated soils.     

The symbiosis with arbuscular mycorrhizal fungi contributes to plant tolerance to serpentine edaphic stress

Serpentine soils represent stressful environment with low calcium to magnesium ratio, deficiencies of essential macronutrients, increased concentrations of heavy metals and a low water-holding capacity. A considerable potential of arbuscular mycorrhizal fungi (AMF) to promote plant growth and nutrition can be expected under these adverse conditions. We tested a hypothesis that both host plants and AMF have evolved edaphic tolerance, which enable them to cope with the conditions of serpentine habitats. A reciprocal transplant experiment with a full factorial design was conducted, involving serpentine and non-serpentine substrates, host plants (Knautia arvensis, Dipsacaceae) and AMF isolates. After three-month cultivation under greenhouse conditions, plant growth and nutrition and AMF development were assessed. Our results evidenced the edaphic differentiation and higher tolerance of both plants and fungi of serpentine origin to serpentine soil. The better performance of serpentine plants was likely based on their tolerance to magnesium accumulation in shoot tissues. The serpentine AMF isolate not only developed higher root colonisation in serpentine conditions, but it was also more efficient in the growth promotion of and phosphorus uptake by the serpentine plants. As it had only a slight impact on magnesium uptake and no influence on calcium and nickel uptake by the serpentine plants, the improved P nutrition seemed to be the crucial mechanism of the mycorrhizal promotion effect. In conclusion, our study proved the tolerance of a plant–mycobiont complex to specific conditions of serpentine soils, which may indicate that not only the individual components of serpentine communities but also their functional interactions are subjected to selective evolutionary forces.     

分室磷添加下菌根对滇池流域红壤间作玉米生长及磷素利用的影响

随着全球范围内磷矿资源短缺问题的日益严重,间作或菌根技术强化作物对土壤磷(P)的利用及增产增收的效应受到越来越多的关注。通过三室隔网盆栽模拟试验研究了分室磷处理[不添加磷(P0)、添加有机磷(OP50)、添加无机磷(IOP50)]和根室不接种(NM)、根室接种丛枝菌根真菌Glomus mosseae(GM)对与大豆间作的玉米的生长及磷素利用的影响。研究结果表明:所有复合处理中,以间作?GM?IOP50组合处理下的玉米根系最短和地上部生物量最高;OP50处理下,间作玉米的菌根侵染率显著高于单作处理。间作条件下,无论分室磷添加与否,接种GM处理的玉米地上部生物量明显高于NM处理;接种GM处理的玉米根系生物量和株高均显著高于NM处理,且根系生物量以间作?GM?OP50组合处理下最高。接种GM条件下,P0、IOP50、OP50处理下的间作植株生物量较单作处理分别提高45.98%、111.33%、33.56%。单作条件下,无论分室磷添加与否,接种GM处理的玉米地上部磷含量均显著高于NM处理;无论何种种植模式及分室磷添加与否,接种GM处理的植物根系磷含量均显著高于NM处理。无论磷添加与否,间作?GM组合条件下的玉米地上部磷吸收量均显著较高,其中IOP50处理下的地上部磷吸收量显著高于OP50处理。间作?GM组合条件下,IOP50处理玉米根系的磷吸收效率均显著高于OP50处理。可见,接种GM、分室磷添加和间作各自在一定程度上促进了玉米的生长。综合菌根侵染、生物量及磷含量与吸收量、磷吸收效率等指标,所有复合处理中以间作?GM?IOP50组合对玉米地上部的促生作用最好,玉米磷素吸收最多,可望有效强化滇池流域红壤坡耕地磷素的利用。     

Effect of inoculation with AM fungi on lead uptake,translocation and stress alleviation of Zea mays L. seedlings planting in soil with increasing lead concentrations

In this work, a greenhouse experiment, arranged in a randomized block design 2 × 6 factorial with six replicates, was conducted to estimate the effect of inoculation with arbuscular mycorrhizal fungi (AMF) on lead uptake, location and stress attenuation in mycorrhizal Zea mays L. seedlings. Treatments were the mycorrhizal inoculation (+M) or non-mycorrhizal inoculation (?M) and six lead concentrations (0, 50, 100, 200, 500 and 1000 μg/g) to soil. The results showed that AM fungal inoculation could attenuate the oxidative stress of lead to Z. mays seedlings. The higher height, basal diameter and biomass of seedlings were found in mycorrhizal Z. mays seedlings growing in the soil with increasing lead concentrations. Moreover, superoxide dismutase (SOD) activity was higher than that of non-inoculated seedlings. AMF increased accumulation of lead in the root system. In the presence of 200, 500 and 1000 μg/g lead, there were higher lead concentrations in roots of mycorrhizal seedlings than in non-mycorrhizal seedlings. Lead was identified to dominantly deposit in the hyphal wall, the hyphal inner chambers, the hyphal inner-chamber membranes and the vacuole inner-chambers membrane. It is, therefore, hypothesized that lead stress can be decreased through the AM fungal cell. The ability of arbuscular mycorrhiza immobilizing lead can alleviate the phytotoxicity of lead to Z. mays seedlings.     

菌根化育苗对玉米生长和养分吸收的影响

【目的】丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)侵染作物根系形成菌根共生体系对于作物吸收磷具有重要作用,但该结果大多来源于室内受控试验,有限的田间试验因环境条件、试验材料与接种技术等差异致使AMF菌剂应用效果不一。本研究通过玉米菌根化育苗和田间移栽,分析了接种AMF对玉米生长、养分吸收、籽粒产量及养分含量的影响,以期推进菌根技术的实际生产应用。【方法】以自交品系玉米B73为供试作物,于2018年5月至10月在北京市延庆区进行了田间试验。田间小区设置基施磷(+P)和不施磷(–P)处理。供试AMF为Rhizophagus irregularis Schenck&Smith BGC AH01。玉米种子催芽后,分别播入加入AMF菌剂(+M)和菌剂过滤液(–M)的育苗钵内,培养两周后移栽至田间。玉米在田间条件下生长至拔节期时,使用便携式光合仪测定叶片光合速率与气孔导度,取样测定地上部与根部干重和养分元素含量,同时测定菌根侵染率;在玉米完熟期取样,测定籽粒百粒重、籽粒产量及养分含量。【结果】无论田间施磷与否,接菌植株根系的菌根侵染强度和丛枝丰度均显著高于不接菌植株。不施磷情况下,+M处理显著提高了玉米根系干重,玉米生长的菌根依赖性(163.7%)显著高于施磷情形(124.1%)。–P–M处理玉米叶片的光合速率和气孔导度显著低于其他3个处理。–P+M处理玉米叶片的光合参数、玉米地上部和根部磷含量与+P+M均无显著差异。与–P–M处理相比,–P+M显著提高了玉米籽粒产量和百粒重,同时也提高了籽粒中锌、锰、镁等矿质养分的含量,且与+P+M处理相比均无显著差异。【结论】玉米幼苗接种AMF后再移栽到田间,可以显著提高拔节期玉米根系的菌根侵染率,促进玉米地上部和根部对磷及锌、锰和镁的吸收,进而促进玉米的生长,提高籽粒产量和养分含量。本试验条件下,菌根化育苗可以达到与施磷同样的效果,在保障作物不减产的前提下减少磷肥施用量。     

AM fungi effects on the growth and physiology of Zea mays seedlings under diesel stress

The effects of an arbuscular mycorrhizal fungus (AMF) (Glomus constrictum Trappe) on the growth and some physio-biochemical indexes of Zea mays L. seedlings under different levels of diesel stress were investigated in a pot study. Generally, the symbiotic relationship between corn and AMF can be well established under diesel stress. This was reflected by the better physio-biochemical index of the plants inoculated with G. constrictum whose colonization rates were between 47.30% and 91.50%. Compared with the non-inoculated ones, the heights and basal diameters of the inoculated seedlings increased by 0.08-47.20% and 6.74-35.71% respectively. The relative contents of chlorophyll and soluble proteins increased by 1.88-38.79% and 3.87-77.27% respectively, while the contents of malondialdehyde and free proline decreased by 2.74-52.74% and 24.69-32.86%. Three antioxidant enzymes reacted differently under the diesel stress. The activities of superoxide dismutase (SOD) and catalase (CAT) increased at low diesel concentration, but decreased at high concentration. In contrast, peroxidase (POD) had a decreased activity at low diesel concentration, but an increased activity at high concentration. On the whole, the activity of three antioxidant enzymes in the plants inoculated with AMF were higher than those without AMF inoculation. Our results support the view that antioxidant enzymes have great influence on the biomass of plants, and AMF can improve the capability of scavenging the reactive oxygen and alleviate Z. mays seedlings from diesel stress.     

接种菌根真菌对不同磷效率基因型大豆生长和磷吸收的影响

接种丛枝菌根真菌(AMF)能显著促进大豆生长和对磷的吸收,但不同磷效率基因型大豆对AMF接种的响应还少有报道。为探究接种AMF对不同磷效率基因型大豆生长和磷转运基因表达的影响,以磷高效大豆BX10和磷低效大豆BD2为试验材料进行盆栽试验,设置接菌和不接菌处理,对大豆干重、菌根侵染性状、氮磷养分含量、根系性状,以及菌根诱导的磷转运基因表达进行了分析。结果表明, AMF接种显著促进了大豆的磷吸收,并且接菌效果存在显著的基因型差异,接种AMF显著增加了BD2的地上部干重、磷含量以及植株总磷吸收量,但只增加了BX10的地上部磷含量和总磷吸收量,对植株地上部干重没有显著影响。无论接种与否,BD2的地上部磷含量均显著高于BX10,表明磷低效的BD2具有较高的植株体内磷转运能力。不接菌条件下,两个大豆基因型根系性状无显著差异;接种AMF后BX10的根系体积和根系平均直径均显著高于BD2。BD2的菌根生长反应(MGR)和菌根磷反应(MPR)均显著高于BX10,对菌根依赖性更高。此外,在接菌处理的BD2根系,代表菌根途径磷吸收的磷转运基因GmPT8、GmPT9和GmPT10表达均显著高于BX10;相应地,BD2的总磷吸收量也显著高于BX10。以上结果表明,接种AMF对促进磷低效大豆BD2生长和磷吸收的作用更大,这可能主要是由于BD2菌根途径的磷吸收量较高,体内磷转运效率较高。以上结果将为研究AMF接种对磷吸收的贡献提供理论依据。     

Effectiveness of two arbuscular mycorrhizal fungi on concentrations of essential oil and artemisinin in three accessions of Artemisia annua L.

A field experiment was conducted to study and compare the effectiveness of two arbuscular mycorrhizal fungi (AMF), Glomus macrocarpum (GM) and Glomus fasciculatum (GF) on three accessions of Artemisia annua. The AM inoculation significantly increased the production of herbage, dry weight of shoot, nutrient status (P, Zn and Fe) of shoot, concentration of essential oil and artemisinin in leaves as compared to non-inoculated plants. The extent of growth, nutrient concentration and production of secondary plant metabolites varied with the fungus–plant accession combination. The mycorrhizal dependency of the three accessions was related to the shoot: root ratio. Comparing the two fungal inoculants in regard to increase in essential oil concentration in shoot, the effectiveness of GF was more than that of GM. While in two accessions, GM was more effective in enhancing artemisinin concentration than GF. Increase in concentration of essential oil was found to be positively correlated to P-status of the plant. Conversely, no correlation was found between shoot-P and artemisinin concentration.     

丛枝菌根真菌(Glomus caledonium)对铜污染土壤生物修复机理初探

利用盆栽试验,研究了丛枝菌根真菌(Glomus.caledonium)在不同程度铜污染土壤上对玉米苗期生长的影响。结果表明,即使在土壤施铜量达150mg/kg时,菌根真菌对玉米仍有近55%的侵染率;接种菌根真菌,能显著促进玉米根系的生长。菌根玉米的根系生物量和根系长度,平均较未接种处理分别提高108.4%和58.8%;接种处理的植株地上部生物量达到每盆(3株)10.58g,显著高于不施铜的非菌根玉米。这些结果表明,丛枝菌根真菌对铜污染具有较好的抗性;并且由于菌根的形成,使宿主植物明显地改善了对磷的吸收和运输,并能通过抑制土壤酸化、降低土壤可溶态铜的浓度等机制,增强宿主植物对铜污染的抗(耐)性。在150mg/kg施铜水平时,与非菌根玉米相比,菌根玉米地上部和根系铜浓度分别降低24.3%和24.1%,吸铜量分别提高了28.2%和60.0%,表明菌根植物对铜污染土壤具有一定的生物修复作用。     

Effect of Arbuscular Mycorrhizal Fungi and Phosphate-Solubilizing Bacteria Consortia Associated with Phospho-Compost on Phosphorus Solubilization and Growth of Tomato Seedlings (Solanum lycopersicum L.)

ABSTRACT

The exploitation of phosphate mines generates an important quantity of phosphate sludge that remains accumulated and not valorized. In this context, composting with organic matter and rhizospheric microorganisms offers an interesting alternative and that is more sustainable for agriculture. This work aims to investigate the synergetic effect of arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PSB) and phospho-compost (PC), produced from phosphate-laundered sludge and organic wastes, and their combination on plant growth, phosphorus solubilization and phosphatase activities (alkaline and acid). Inoculated mycorrhizae and bacteria strains used in this study were selected from plant rhizosphere grown on phosphate-laundered sludge. Significant (p < .05) increases in plant growth was observed when inoculated with both consortia and PC (PC+ PSB+ AMF) similar to those recorded in plants amended with chemical fertilizer. Tripartite inoculated tomato had a significantly (p < .05) higher shoot height; shoot and root dry weight, root colonization and available P content, than the control. Co-inoculation with PC and AMF greatly increased alkaline phosphatase activity and the rate of mycorrhizal intensity. We conclude that PC and endophytic AMF and PSB consortia contribute to a tripartite inoculation in tomato seedlings and are coordinately involved in plant growth and phosphorus solubilization. These results open up promising prospects for using formulate phospho-compost enriched with phosphorus-solubilizing microorganisms (PSM) in crop cultivation as biofertilizers to solve problems of phosphate-laundered sludge accumulation.     

Responses of directly seeded wetland rice to arbuscular mycorrhizal fungi inoculation

The mycorrhizal enhancement of plant growth is generally attributed to increased nutrients uptake. A greenhouse experiment was conducted to investigate the effect of arbuscular mycorrhizal fungi (AMF) inoculation on the growth and nutrient uptake of directly seeded wetland rice. Seeds were germinated and inoculated with arbuscular mycorrhizal fungi or left uninoculated. The plants were grown at 60% of ‐0.03 MPa to establish the mycorrhizas. After 5 weeks, half of the pots were harvested and the rest were flooded with deionized water to maintain 3–5 cm of standing water until harvesting (122 days after sowing). Mycorrhizal fungal colonization of rice roots was 36.2% at harvest. Mycorrhizal fungi inoculated rice seedlings grew better compared to uninoculated seedlings and had increased grain yield (10%) at the harvesting stage. Shoot and root growth were effectively increased by AMF inoculation at the harvesting stage. The nitrogen (N) and phosphorus (P) acquisition of direct seeding wetland rice were significantly increased by AMF inoculation. The AMF enhanced N and P translocation through the hyphae from soils to roots/shoots to grains effectively.     

Dual plant host effects on two arbuscular mycorrhizal fungi

Mycorrhizal fungi may simultaneously associate with multiple plant hosts, and the implications of this for the fungi involved are not well understood. To address this question, two arbuscular mycorrhizal fungi (AMF), Glomus clairoideum (a treatment referred to as “Glo”) and Scutellospora fulgida (a treatment referred to as “Scut”), were grown separately in pots that each consisted of two plant compartments separated by a root-free-compartment (RFC). Fungi within each two-plant-compartment pot were exposed to either two individuals of indiangrass (Sorghastrum nutans), two individuals of big bluestem (Andropogon gerardii), or one of each. A non-inoculated treatment (“Non”) was included to help gauge the potential influence of greenhouse contaminant fungi, cross-contamination, or any misidentification of non-AMF hyphae. The two host species had additive effects on the growth of AM hyphae in plant compartments of Scut, Glo, and Non pots, and in the RFCs of Scut pots. In Glo RFCs, however, they were antagonistic in their effects. Synergism between hosts in Non RFCs suggested that any potential contaminants or misidentification could not explain this result. Underyielding was not seen in shoot weight, root weight, or root length in dual host pots, and also therefore could not explain the result. Hyphal growth in the Scut treatment was evenly distributed between the RFC and plant compartments (or marginally skewed toward the RFC), while hyphal growth in the Glo treatment was skewed toward plant compartments (nearer roots). However, hyphal lengths were more highly correlated across plant compartments within a common pot in the Glo treatment, suggesting that this AMF bridged the RFC to experience the entire two-host pot as a single environment to a greater extent than Scut did. These AMF differed in how they responded to both the species composition of the two-host environment and its spatial structure; potential implications for mycorrhizal community dynamics are discussed.     

Arbuscular mycorrhizal fungi pre-inoculant identity determines community composition in roots

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.     

四种AM真菌接种剂的田间效应及其分子检测研究

采用灭菌土壤生产了 4种AM真菌接种剂。在盆栽条件下测试了接种剂的质量 ,结果显示 ,4种接种剂促进玉米生长效果明显 ,地上部分生物量均显著高于对照 (p <0 .0 1 ) ;以MPN试验检测了接种剂的侵染能力 ,结果表明每克接种剂中真菌的繁殖体数在 95～ 1 4 0 0之间。将AM真菌的预接种技术和农业生产上的营养钵育苗技术相结合 ,进行了玉米的田间试验 ,结果显示 ,玉米根系的AM真菌感染率早期增长较快 ,然后趋于平稳 ;AM真菌接种剂A(Glomusconstrictum)、C (Glomus三种菌混合 )和D (G .intraradices)对玉米籽粒产量有显著的增产效果 (p <0 .0 5 ) ;玉米籽粒的淀粉含量和磷含量也高于对照。运用特异性分子探针和nest ed PCR技术 ,从田间接种AM真菌Glomusintraradices和G .mosseae的玉米根样中粗提DNA进行特异性扩增 ,成功地从感染根段中检测到特定的接种AM真菌。本工作从分子水平为评价高效AM真菌的应用潜力、研究AM真菌之间及其与其他微生物之间的相互关系奠定了基础。     

Growth Response and Nutrient Uptake of Eriobotrya japonica Plants Inoculated with Three Isolates of Arbuscular Mycorrhizal Fungi Under Water Stress Condition

Mycorrhizal technique is a promising biotechnology in horticultural industry, benefiting plants exposed to diverse abiotic stresses. In this study, the effects of three arbuscular mycorrhizal fungi (AMF), Acaulospora laevis, Glomus mosseae, and Glomus caledonium on plant growth and nutrient uptake of loquat (Eriobotrya japonica Lindl.) seedlings under three water regimes (well watered, water stressed-slight, water stressed-heavy) were investigated. Results showed that inoculated seedlings had higher dry biomass, plant height, and total leaf areas than those un-inoculated ones. AMF effect was the greatest for water stressed-heavy seedlings, followed by water stressed-slight seedlings and well watered seedlings. All AMF species increased the uptake of nitrogen (N) potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), and the mycorrhizal contributions to the nutrient uptake were positively related to that to the biomass. Data suggest that AMF inoculation increases the tolerance of loquat seedlings to drought stress, and the improved nutrient uptake by AMF contributes greatly to the tolerance.     

Additive and interactive effects of functionally dissimilar soil organisms on a grassland plant community

The productivity and diversity of plant communities are affected by soil organisms such as arbuscular mycorrhizal fungi (AMF), root herbivores and decomposers. However, it is unknown how interactions between such functionally dissimilar soil organisms affect plant communities and whether the combined effects are additive or interactive. In a greenhouse experiment we investigated the individual and combined effects of AMF (five Glomus species), root herbivores (wireworms and nematodes) and decomposers (collembolans and enchytraeids) on the productivity and nutrient content of a model grassland plant community as well as on soil microbial biomass and community structure. The effects of the soil organisms on productivity (total plant biomass), total root biomass, grass and forb biomass, and nutrient uptake of the plant community were additive. AMF decreased, decomposers increased and root herbivores had no effect on productivity, but in combination the additive effects canceled each other out. AMF reduced total root biomass by 18%, but decomposers increased it by 25%, leading to no net effect on total root biomass in the combined treatments. Total shoot biomass was reduced by 14% by root herbivores and affected by an interaction between AMF and decomposers where decomposers had a positive impact on shoot growth only in presence of AMF. AMF increased the shoot biomass of forbs, but reduced the shoot biomass of grasses, while root herbivores only reduced the shoot biomass of grasses. Interactive effects of the soil organisms were detected on the shoot biomasses of Lotus corniculatus, Plantago lanceolata, and Agrostis capillaris. The C/N ratio of the plant community was affected by AMF.In soil, AMF promoted abundances of bacterial, actinomycete, saprophytic and AMF fatty acid markers. Decomposers alone decreased bacterial and actinomycete fatty acids abundances but when decomposers were interacting with herbivores those abundances were increased. Our results suggests that at higher resolutions, i.e. on the levels of individual plant species and the microbial community, interactive effects are common but do not affect the overall productivity and nutrient uptake of a grassland plant community, which is mainly affected by additive effects of functionally dissimilar soil organisms.     

Effects of arbuscular mycorrhizal fungi on the growth of two turfgrasses grown under greenhouse conditions

ABSTRACT

The need for salinity resistance in turfgrass is increasing because of the enhanced use of effluent and other low-quality water for turfgrass irrigation. Although most turfgrasses form an arbuscular mycorrhizal fungus (AMF) symbiosis, there is little information on the mycorrhization of turfgrass species. Therefore, the aim of this study was to determine the effects of three AMF species, Glomus intraradices Schenck & Smith, Glomus etunicatum Becker & Gerdemann, and Glomus deserticola Trappe & John, and a mixture thereof on the growth, productivity, and nutrient uptake of two species of cool-season turfgrasses, Challenger Kentucky bluegrass (Poa pratensis L.) and Arid tall fescue (Festuca arundinacea Schreb.), and to relate the effects to colonization of the roots by mycorrhiza to assess the dependency of the plants (mycorrhizal dependency [MD]). Following the experimental period (4 months) and measurements, the mycorrhizal inoculated plants had significantly greater biomass production compared to that of non-inoculated plants. MD and shoot mineral contents (particularly P) differed among turfgrass hosting AMF, and the highest value (13%) occurred for P. pratensis and F. arundinacea seedlings colonized with G. intraradices and G. deserticola, respectively. The P content was highest for the F. arundinacea/mixed AMF combination compared to other treatments. We confirmed that mycorrhizal inoculation (P. pratensis/G. intraradices and F. arundinacea/mixed AMF combinations) enhanced plant productivity and nutrient uptake (especially P) even under non-optimum conditions.