Intraradical hyphae phosphatase of the arbuscular mycorrhizal fungus, Gigaspora margarita

An alkaline phosphatase in the intraradical hyphae of arbuscular mycorrhizal fungi was found to be closely related to an improvement of plant growth. To detect the phosphatase activity in a crude extract of mycorrhizal roots, phosphatase isozymes in mycorrhizal and non-mycorrhizal onion roots were compared with those in Gigaspora margarita by electrophoresis. A mycorrhiza-specific band was found when the phosphatase was stained under alkaline conditions. To clarify the origin of this phosphatase, the phosphatase extracted from intraradical hyphae was also compared with the phosphatase from mycorrhizal roots by electrophoresis. The intraradical hyphae was isolated from mycorrhizal roots by enzyme digestion followed by Percoll gradient centrifugation. The soluble protein was extracted from the hyphae by ultra-sonication after treatment with chitinase. A phosphatase in the hyphal soluble protein showed a similar, but slightly higher, relative mobility on the gel, compared with the mycorrhiza-specific phosphatase from roots. By adding the hyphal extract to the root extract, the relative mobility of the mycorrhiza-specific phosphatase was slightly changed and became identical to that of the phosphatase in the hyphae. This indicated that the specific band of phosphatase found in the crude extract from mycorrhizal roots was of intraradical hyphal origin. Received: 16 April 1997     

Effects of nitrogen feeding for extraradical mycelium of Rhizophagus irregularis maize symbiosis incorporated with phosphorus availability

In terrestrial ecosystems, plants are frequently in symbiosis with arbuscular mycorrhizal fungi (AMF) with mineral nutrients and photosynthesis carbon exchanges in between. This research sought to identify the effects of phosphorus (P) levels on the nitrogen (N) uptake via extraradical mycelium (ERM) and the mycorrhizal growth response (MGR) of maize plants within the AMF symbiosis. Pots were separated into root compartments and hyphae compartments (HCs) with two layers of a 30‐μm mesh membrane and an air gap in between, where only hyphae could pass through, to avoid both N diffusion and root growth effects. Maize plants were inoculated with Rhizophagus irregularis with different N fertilization in HCs under two different P fertilization levels. Our results indicated that a strong increase in MGR with low‐P fertilization. The same tendency was not observed with high‐P fertilization, although both had a large increase in P concentration as a potential source of growth in shoot tissue of mycorrhizal plants. Substantial effects (10.5% more N) were observed in the case of high‐P availability for the host plants from ERM fed with N, whereas under low‐P conditions ERM may prioritize P uptake rather than N uptake. The AM fungi increase the uptake of N and P, which are most limiting in the soil with fewer forces from soil resources. In addition, there was still more P accumulated than N due to the high N for ERM with high‐P supply. Low N in HCs corresponded with a lower colonization rate in roots but with high hyphae density in HCs; this result suggest that N and P availability might change the ratio of extraradical to intraradical hyphae length.     

丛枝菌根根外菌丝对铵态氮和硝态氮吸收能力的比较

采用空气隔板分室法并结合15N标记技术,以玉米为宿主植物并接种Glomus mosseae和Glomus intraradices,比较了这两种真菌根外菌丝对铵态氮和硝态氮吸收传递能力的差异。结果表明,丛枝菌根根外菌丝吸收传递氮的能力因菌种和氮素形态而异。两种真菌根外菌丝吸收传递NH4+-N能力均高于NO3--N;G. intraradices根外菌丝吸收传递氮的能力高于G. mosseae,这可能与两种真菌根外菌丝生长量有关。     

Use of specific phospholipid fatty acids for identifying and quantifying the external hyphae of the arbuscular mycorrhizal fungus Gigaspora rosea

The external hypha of arbuscular mycorrhizal (AM) fungi, extending from roots out into soil, is an important structure in the uptake of phosphate from the depletion zone around each root. In this paper, we analysed some phospholipid fatty acids (PLFAs) derived from external hyphae of four AM fungi (Glomus etunicatum, Glomus clarum, Gigaspora margarita and Gigaspora rosea) to find fatty acids which may be useful as specific markers for identifying and quantify the external hyphae of Gigaspora species. Leek (Allium porrum L.) seedlings inoculated with each AM fungus were grown in river sand. Sand samples were collected and four PLFAs (16:1ω5, 18:1ω9, 20:1ω9 and 20:4) in the sand were analysed. In addition, the hyphal biomass in the sand was determined by the direct microscopic method. PLFAs 18:1ω9 and 20:4 were found in all the AM-inoculated and non-inoculated sand samples. PLFA 16:1ω5 was detected in the sand inoculated with G. etunicatum, G. clarum and Gi. rosea. PLFA 20:1ω9 was detected only in the sand inoculated with Gi. rosea. PLFAs 16:1ω5 and 20:1ω9 were not found in the sand inoculated with Gi. margarita. The amount of PLFA 20:1ω9 was closely correlated with the amount of biomass of external hyphae of Gi. rosea (r=0.937, P<0.001), whereas no correlation was observed for PLFA 16:1ω5. The 20:1ω9 content of Gi. rosea was approximately 6.56 nmol mg⁻¹ hyphal biomass. We suggest that PLFA 20:1ω9 can be used as a specific marker for identifying and quantifying the external hyphae of Gi. rosea, at least in controlled experimental systems.     

Isolation and characterization of phosphate solubilizing bacteria from the rhizosphere of crop plants of Korea

Whole-cell fatty acids methyl ester (FAME) profile and 16S rDNA sequence analysis were employed to isolate and identify the bacterial groups that actively solubilized phosphates in vitro from rhizosphere soil of various crops of Korea. Out of several hundred colonies that grew on Pikovskaya's medium 13 best isolates were selected based on the solubilization of insoluble phosphates in liquid culture and further characterized and identified. They were clustered under the genera Enterobacter, Pantoea and Klebsiella and the sequences of three representative strains were deposited in the GenBank nucleotide sequence data library under the accession numbers AY335552, AY335553, AY335554.     

丛枝菌根真菌对金叶六道木镉吸收及根际真菌群落结构的影响

为明确丛枝菌根(AM)真菌对促进绿化苗木镉(Cd)吸收的影响,通过盆栽试验比较接种不同AM真菌对12种绿化苗木Cd吸收的差异,并进一步分析接种对金叶六道木根际微生物数量和AM真菌群落结构的影响.结果表明,12种绿化苗木,加Cd处理6个月后,其叶片浓度的变化范围为0.25～2.59 mg·kg–1.接种AM真菌处理组的叶...     

Enhancement of arbuscular mycorrhizal fungus (Glomus versiforme) on the growth and Cd uptake by Cd-hyperaccumulator Solanum nigrum

Arbuscular mycorrhizal fungus (AMF) can enhance plant growth and resistance to toxicity produced by heavy metals (HMs), affect the bioavailability of HMs in soil and the uptake of HMs by plants, and thus has been emerged as the most prominent symbiotic fungus for contribution to phytoremediation. A greenhouse pot experiment was conducted to assess the effect of Glomus versiforme BGC GD01C (Gv) on the growth and Cd accumulation of Cd-hyperaccumulator Solanum nigrum in different Cd-added soils (0, 25, 50, 100 mg Cd kg⁻¹ soil). Mycorrhizal colonization rates were generally high (from 71% to 82%) in Gv-inoculated treatments at all Cd levels. Gv colonization enhanced soil acid phosphatase activity, and hence elevated P acquisition and growth of S. nigrum at all Cd levels. Moreover, the presence of Gv significantly increased DTPA-extractable (phytoavailable) Cd concentrations in 25 and 50 mg Cd kg⁻¹ soils, but did not affect phytoavailable Cd in 100 mg Cd kg⁻¹ soil. Similarly, inoculation with Gv significantly increased Cd concentrations of S. nigrum in 25 and 50 mg Cd kg⁻¹ soils, but decreased Cd concentrations of the plants in 100 mg Cd kg⁻¹ soil. Overall, inoculation with Gv greatly improved the total Cd uptakes in all plant tissues at all Cd levels. The present results indicated that S. nigrum associated with Gv effectively improved the Cd uptake by plant and would be a new strategy in microbe-assisted phytoremediation for Cd-contaminated soils.     

施磷水平和接种AMF与解磷细菌对苜蓿产量及磷素利用效率的影响

为探讨不同施磷水平下接种丛枝菌根真菌(Arbuscular Mycorrhizae Fungi,AMF)与解磷细菌对苜蓿干物质产量及其磷素利用效率的影响,筛选出苜蓿最佳的施肥模式,为紫花苜蓿高效生产及高效复合型菌肥的研制提供理论依据。该研究试验采用双因素随机区组设计,AMF选用摩西管柄囊霉,解磷细菌选用巨大芽孢杆菌,设置4个施菌水平:分别为接种摩西管柄囊霉(Fm,J₁)、巨大芽孢杆菌(Bm,J₂)、混合菌种(Fm×Bm,J₃)和未接菌处理对照组(J₀)。施磷(P₂O₅)设置4个水平P0～P3分别为:0、50、100和150 mg/kg,菌磷互作共16个处理。结果表明:1)相同施菌条件下,苜蓿各茬次干物质产量、总干物质产量和植株磷含量均随施磷量的增加呈先增加后降低的趋势。除J₂条件下,J₂P₁处理下的苜蓿总干物质产量达到最大值外,其他施菌条件下,苜蓿的总干物质产量均在P₂...     

MES [2-(N-morpholine)-ethane sulphonic acid] buffer promotes the growth of external hyphae of the arbuscular mycorrhizal fungus Glomus intraradices in an alkaline sand

In this work we investigated the hypothesis, suggested by unpublished experiments carried out previously, that application of MES [2-(N-morpholino)-ethane sulphonic acid] buffer to the substrate of plants hosting the arbuscular mycorrhizal fungus Glomus intraradices might favour the growth of external hyphae. The substrate of Trifolium pratense plants, with or without G. intraradices inoculum, was treated twice weekly, between weeks 5 and 11 of growth, plant with distilled water, P-supplemented 10% Hewitt nutrient solution (H+P), 51mM in H+P or 1mM TRIS-HCl in H+P. MES buffer increased the length of external G. intraradices hyphae and the density of propagules in the substrate, but plant growth was not affected. Although both TRIS-HCl and MES caused substrate pH to fall (from 8.51 to 7.35 and 7.17, respectively), only MES induced a significant increase in external hypha length. We conclude that the effect of MES on external hypha length was not due to plant growth or to substrate pH per se. Received: 10 March 1996     

Influence of composite inoculations of phosphate solubilizing organisms and an arbuscular mycorrhizal fungus on yield,grain protein and phosphorus and nitrogen uptake by greengram

Abstract

The agronomic efficiency of nitrogen (N) fixing and phosphate solubilizing microorganisms and an arbuscular mycorrhizal (AM) fungus on vigour, photosynthetic pigments, seed yield, grain protein and nutrient uptake of greengram plants, were assessed in soils, deficient in phosphorous (P). The tripartite inoculation of Glomus fasciculatum + Bradyrhizobium sp. (vigna) + Bacillus subtilis, significantly increased dry matter, chlorophyll content and nutrient uptake of greengram plants. Generally, the number of nodules formed per plant was more at flowering stage, which decreased at podfill stage of plant growth. Seed yield increased significantly by 27% due to inoculation with Bradyrhizobium sp. (vigna) + B. subtilis + G. fasciculatum, relative to the control. Grain protein ranged from 17% (P. variabile) to 28% (Bradyrhizobium sp. (vigna) + B. subtilis + G. fasciculatum) in inoculated greengram. A negative effect occurred on some of the measured parameters when P. variabile was used alone or in combination treatments. The N and P contents in measured plant parts (e.g., roots, shoots, straw and grain) differed considerably among treatments. The populations of PSM, percentage of root infection and density of the AM fungal spore improved in some of the treatments.     

培养基质对丛枝菌根(AM)真菌生长发育的影响

温室条件下,以盆栽培养方法研究不同培养基质对丛枝菌根(Arbuscular Mycorrhizae,AM)真菌Glomus mosseae生长发育的影响。结果表明：不同理化性质的基质对菌根共生体生长发育的影响不同,综合考虑菌根长度、根外菌丝量及孢子数3项指标,以沙土混合物(体积比3∶1)对G. mosseae菌剂的生长发育最为有利。宿主植物菌根长度及根中的可溶性糖浓度与根外孢子数有正相关关系,而宿主植物中磷浓度与菌根真菌的生长发育也有类似的关系。说明培养基质的养分状况、水分状况、通气状况等诸多因素都会影响菌根共生体的建立和发展。宿主植物的菌根长度、根中可溶性糖浓度以及宿主植物磷浓度对菌根真菌的生长发育有显著影响。因此,工厂化AM菌剂生产中,应以沙土混合物(体积比3∶1)为生产G. mosseae菌剂的培养基质。     

土壤微生物溶磷分子机理研究进展

土壤中均含有大量的难溶性磷,而有效磷含量一般较低,土壤磷素供给不足常常是制约作物生长发育的重要因素之一。因此,活化土壤难溶性磷,增强土壤供磷能力,一直是人们普遍关注的重要问题。土壤中存在大量的溶磷微生物,这些微生物能够将难溶磷转化为植物能够吸收利用的有效磷。可见,了解这些微生物的溶磷机理,对于利用其溶磷功能、提高土壤磷素利用效率十分重要。本文对近年来微生物溶磷分子机理进行了综述。     

转Bt基因作物对丛枝菌根真菌的影响研究进展

在过去的十年里，世界范围内转基因作物尤其是抗虫性转Bt基因作物的品种和种植面积迅速增加。同时，转Bt基因作物的环境安全性评价问题成为人们关注和研究的热点。丛枝菌根真菌（AMF）是生态系统中普遍存在的土壤微生物，能与绝大多数植物种类形成共生关系，在农业生态系统中起重要作用。转Bt基因作物环境释放后，其与AMF问的共生关系是否受所转入Bt基因的影响，以及影响机制需要及时研究。为此，综述了转Bt基因作物与AMF共生特征方面的研究进展，并根据Bt毒素发生的空间和时间规律提出了危害机制以及转Bt基因植物的规模化种植将降低农田系统中的AMF的生物多样性的观点。     

Can the arbuscular mycorrhizal fungus Glomus intraradices actively mobilize P from rock phosphates?

Plants colonized by arbuscular mycorrhizal (AM) fungi have been shown to respond positively to the application of insoluble forms of inorganic phosphorus (P) such as rock phosphates (RPs). The mechanism(s) underlying such responses remain(s) unknown and although it has been hypothesized, there is no experimental support for the production of chelating agents by AM fungal hyphae. Here we investigate whether AM fungi can solubilize P from RPs and transfer it to plant roots. Using root-organ cultures of Daucus carrota L. inoculated or not with Glomus intraradices Schenk & Smith and containing P from different RP sources, we predicted that: (1) roots inoculated with G. intraradices would take up more P than those uninoculated; that (2) the amount of P taken up by roots through G. intraradices would be positively correlated with the RP reactivity; and that (3) G. intraradices would have access to RP through localized alterations of pH and/or by the production of organic acid anions that may act as chelating agents. The RP reactivity was positively correlated with P uptake. However, mycorrhizal roots grew initially slower and did not respond differently to any P treatment than those uninoculated. There was no evidence of localized changes in pH in proximity of G. intraradices hyphae, indicating that responses to RP by mycorrhizal plants observed in previous studies do not appear to result from the release of H⁺ ions alone or in combination with organic acid anions.     

Effect of peat on mycorrhizal colonization and effectiveness of the arbuscular mycorrhizal fungus Gigaspora margarita

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.     

Effects of arbuscular mycorrhizal fungus Rhizoglomus intraradices on active and passive pools of carbon in long-term soil fertility gradients of maize based cropping system

A potculture study was conducted in soils collected from long-term fertilizer experiment (LTFE) being kept up as far the past 40 years to determine whether arbuscular mycorrhizal fungus (AMF) Rhizoglomus intraradices colonization changes the active and passive pools of carbon in a maize (Zea mays) – finger millet (Eleusine crocana)- cowpea (Vigna sinensis) cropping sequence in the Experimental Farm of the Tamil Nadu Agricultural University, Coimbatore, India. Soil samples were processed, sterilized and maize plants were grown in various fertility gradients in the absence (M-) or presence (M+) of AMF (Rhizoglomus intraradices) inoculation. The data have clearly shown that M+ soils had consistently higher active pools such as water soluble carbon, hot water soluble carbon and biomass carbon (M- 189; M + 305 mg kg^?1), and passive pools such as soil organic carbon (M- 4.17; M + 4.31 mg g^?1) and total glomalin. Among the fertility gradients, 100% NPK + Farm Yard Manure (FYM) with or without mycorrhizal fungal inoculation registered higher values for both active and passive pools of C but the response was more pronounced in the presence AMF inoculation. Overall, the data suggest that mycorrhizal fungal inoculation assists in effective carbon sequestration in an intensive cereal-legume cropping system.Abbreviations: AMF: Arbuscular mycorrhizal fungi; DAS: Days After Sowing; LTFE: Long-Term Fertilizer Experiment; WSC: Water soluble organic carbon; HA: Humic acid; FA: Fulvic acid; HWSC: Hot water soluble carbon     

Subcritical soil hydrophobicity in the presence of native and exotic arbuscular mycorrhizal species at different soil salinity levels

Soil salinity and arbuscular mycorrhizal fungi (AMF) influence the soil hydrophobicity. An experiment was performed to determine the effects of soil salinity and AMF species on soil water repellency (SWR) under wheat (Triticum aestivum L.) crop. Six AMF treatments, including four exotic species (Rhizophagus irregularis, Funneliformis mosseae and Claroideoglomus claroideum, a mix of three species), one mix native AMF species treatment and an AMF-free soil in combination with four salinity levels (1, 5, 10, and 15 dS m^?1) were used. The soil repellency index (RI) increased with salinity increment ranging from 2.4 to 10.5. The mix of three exotic and native AMF treatments enhanced the RI significantly compared to AMF-free soil in all salinity levels with one exception for native treatment at 1 dS m^?1. Among individual AMF species, the C. claroideum treatment at 10 dS m^?1 increased the RI by 67% compared to AMF-free soil. The native AMF treatment was more efficient in root colonization, glomalin production and SWR development at 10 and 15 dS m^?1, compared to exotic species. In addition to the net positive effect of salinity on SWR, the AMF influences on the RI were greatly dependent on salinity levels.     

The influence of tillage on the structure of rhizosphere and root-associated arbuscular mycorrhizal fungal communities

Soil environmental factors affect the structure of arbuscular mycorrhizal (AM) fungal communities present in soil. However, it is not understood to which degree management practices such as tillage lead to dissimilarities between intra- and extraradical AM fungal communities. This study aims to assess the influence of two different soil management practices (conventional tillage and no-till) on the diversity of AMF communities, both in rhizosphere soil and inside corn roots. We hypothesized that under no-till, roots are colonized as they grow through the undisturbed fungal mycelia left from the previous crop whereas under conventional tillage they are colonized by those propagules that survived disturbance and can re-establish in their new relocated and mixed environment. We predicted that the degree of similarity of AM fungal communities inside versus outside the roots would be greater under no-till than under tillage. Using terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis we observed a different AM fungal community present in roots under no-till than under conventional tillage. Moreover, the communities present in the rhizosphere soil were different than in the roots of the corn plants. These results suggest that soil management does alter the diversity of AM fungal communities associated with corn roots and that plants influence the structure of the AMF community colonizing their roots. Sequencing results indicated that the majority of AMF species found in this agricultural soil was Glomus spp. However, further work is required to determine the extent to which AM fungal genotypic alterations by soil management influences competitive relationships.     

三种土壤上六种丛枝菌根真菌生长特征和接种效应

以分离于华北、华中和华南3个生态区及法国引进的丛枝菌根真菌为试验菌株,采用三室根箱培养的方法,研究了它们在华北、华中和华南3种典型土壤褐土、棕壤和红壤上的菌根形成、接种效应、磷吸收贡献和根外菌物量情况。结果表明,6种菌株在上述指标上存在显著的种间或生态型差异,土壤与菌株间存在显著的交互作用。6种菌株在3种土壤上都能与玉米形成菌根,在褐土和棕壤上大多数菌株在分离地所在地区土壤类型上的菌根侵染率较高,说明其对该土壤条件的适应性较强;在红壤强酸性土壤条件抑制了菌根真菌的侵染。菌株BEG168、BEG167、BEG151、BEG221和BEG141在褐土上,BEG151和BEG221在棕壤上,BEG168和BEG150在红壤上显著提高了玉米的生物量。在褐土和棕壤上,除BEG150外,BEG168、BEG167、BEG151、BEG221和BEG141能显著促进宿主吸磷;而在红壤上,BEG168和BEG141显著促进了宿主吸磷。若以真菌的根外菌物量作为衡量AM真菌菌株土壤生态适应性的指标,BEG141和BEG167是生态适应性强的菌株,为广幅生态型菌株;菌株BEG168和BEG151次之,前者在棕壤上适应性高,后者在红壤上适应性高。BEG150和BEG221生态适应性较窄,仅适应红壤或褐土,为窄幅生态型菌株。Glomus.etunicatum的两个生态型BEG168和BEG221在土壤生态适应性上差异很大,前者在两种土壤上收集到菌物量,而后者只在褐土上收集到菌物量。土壤条件可以决定丛枝菌根真菌的生长状况和功能。