Evaluation and first-year field testing of efficient vesicular arbuscular mycorrhizal fungi for inoculation of wetland rice seedlings

Grain yields of the rice cultivar Prakash were improved upon inoculation with Glomus intraradices and G. fasciculatum, by 11% and 8%, respectively, compared with an uninoculated control. The results indicate that the amount of phosphate fertilizer usually applied to rice may be decreased by 50%, without affecting yield, if G. intraradices is inoculated.The authors are with the Department of Agricultural Microbiology, University of Agricultural Sciences, GKVK Campus, Bangalore 560 065, India. ing author.     

Response of 11 eucalyptus species to inoculation with three arbuscular mycorrhizal fungi

 Numerous publications have reported growth stimulation of Eucalyptus following ectomycorrhizal inoculation in nursery or field conditions. Although Eucalyptus species can also form arbuscular mycorrhiza, their dependency on this type of mycorrhiza is still debatable. This paper presents information on the effect of inoculation of arbuscular mycorrhizal fungi on eucalypt growth. Twenty weeks after mycorrhizal inoculation, Eucalyptus seedlings' stem dry weight could be increased up to 49% compared to non-inoculated control plants. Intensity of root colonization by a given fungus depended on the host species, but it was not related to a plant growth response. Leaf phosphorus concentration of non-inoculated Eucalyptus seedlings varied greatly between species. Increases in leaf phosphorus concentration following mycorrhizal infection were not necessarily associated with plant growth stimulation. The most mycorrhiza-dependent Eucalyptus species tended to be those having the highest leaf phosphorus concentration in the absence of a fungal symbiont. These mycorrhiza-dependent Eucalyptus species seem to have greater phosphorus requirements and consequently to rely more on the symbiotic association. Accepted: 1 September 1995     

Influence of temperature on colonization of spring barleys by vesicular arbuscular mycorrhizal fungi

The effects of three soil temperatures on growth of spring barleys (Hordeum vulgare L.) and on their root colonization by vesicular arbuscular mycorrhizal (VAM) fungi from agricultural soils in Montana (USA) or Syria at different inoculum concentrations were tested in soil incubators in the greenhouse. The number of mycorrhizal plants as well as the proportion and intensity of roots colonized increased with higher soil temperatures. VAM fungi from Montana, primarily Glomus macrocarpum, were cold tolerant at 11°C while those from Syria, primarily G. hoi, were heat tolerant at 26°C. Inoculum potential of Montana VAM fungi was higher than Syrian VAM fungi in cool soils. Harmal, selected from Syrian barley land races, had the highest colonization by mycorrhizal fungi of the cultivars tested.Journal Series Paper: J-2532 Montana Agricultural Experiment Station.     

Improvement of Cupressus atlantica Gaussen growth by inoculation with native arbuscular mycorrhizal fungi

AIMS: The study aimed to determine whether inoculation with native arbuscular mycorrhizal (AM) fungi could improve survival and growth of seedlings in degraded soils of Morocco. METHODS AND RESULTS: Soil samples were collected from the rhizosphere of Cupressus atlantica trees in the N'Fis valley (Haut Atlas, Morocco). AM spores were extracted from the soil, identified and this mixture of native AM fungi was propagated on maize for 12 weeks on a sterilized soil to enrich the fungal inoculum. Then C. atlantica seedlings were inoculated with and without (control) mycorrhizal maize roots, cultured in glasshouse conditions and further, transplanted into the field. The experiment was a randomized block design with one factor and three replication blocks. The results showed that a high AM fungal diversity was associated with C. atlantica; native AM fungi inoculation was very effective on the growth of C. atlantica seedlings in glasshouse conditions and this plant growth stimulation was maintained for 1 year after outplanting. CONCLUSIONS: Inoculation of C. atlantica with AM fungi increased growth and survival in greenhouse and field. SIGNIFICANCE AND IMPACT OF THE STUDY: The data indicate that use of native species of AM fungi may accelerate reforestation of degraded soils. Further studies have to be performed to determine the persistence of these mycorrhizae for a longer period of plantation and to measure the effects of this microbial inoculation on soil biofunctioning.     

Impact of arbuscular mycorrhizal fungal inoculants on subsequent arbuscular mycorrhizal fungi colonization in pot-cultured field pea (Pisum sativum L.)

The use of commercial inoculants containing non-resident arbuscular mycorrhizal fungi (AMF) is an emerging technology in field crop production in Canada. The objective of this study was to assess the impact of AMF inoculants containing either a single species (Glomus irregulare) or mixed species (G. irregulare, Glomus mosseae, and Glomus clarum) on AMF root colonization and consequent plant growth parameters of field pea grown using pot cultures. Field pea was grown in both sterilized and non-sterile (i.e., natural) field-collected soil containing resident AMF and received three inoculation treatments: uninoculated control, G. irregulare only, and a mixture of AMF species of G. irregulare, G. mosseae, and G. clarum. After 42 days, the AMF community assembled in field pea roots was assessed by cloning and sequencing analysis on the LSU-ITS-SSU rDNA gene, together with a microscopic assessment of colonization, biomass production, nutrient uptake, and N₂ fixation. The identity of AMF inoculants had a significant effect on field pea performance. The mixed species AMF inoculant performed better than the single species G. irregulare alone by promoting mycorrhizal colonization, field pea biomass, N and P uptake, and N₂ fixation and did not result in a significant compositional change of the AMF community that subsequently assembled in field pea roots. In contrast, the single species G. irregulare inoculant did not significantly enhance field pea biomass, N and P uptake, and N₂ fixation, although a significant compositional change of the subsequent AMF community was observed. No significant interactions affecting these measurements were detected between the resident AMF and the introduced AMF inoculants. The observation that the mixed species AMF inoculant promoted plant growth parameters without necessarily affecting the subsequent AMF community may have important implications regarding the use of non-resident AMF inoculants in agricultural production.     

Response of endangered plant species to inoculation with arbuscular mycorrhizal fungi and soil bacteria

Three endangered plant species, Plantago atrata and Pulsatilla slavica, which are on the IUCN red list of plants, and Senecio umbrosus, which is extinct in the wild in Poland, were inoculated with soil microorganisms to evaluate their responsiveness to inoculation and to select the most effective microbial consortium for application in conservation projects. Individuals of these taxa were cultivated with (1) native arbuscular mycorrhizal fungi (AMF) isolated from natural habitats of the investigated species, (2) a mixture of AMF strains available in the laboratory, and (3) a combination of AMF lab strains with rhizobacteria. The plants were found to be dependent on AMF for their growth; the mycorrhizal dependency for P. atrata was 91%, S. umbrosus-95%, and P. slavica-65%. The applied inocula did not significantly differ in the stimulation of the growth of P. atrata and S. umbrosus, while in P. slavica, native AMF proved to be the less efficient. We therefore conclude that AMF application can improve the ex situ propagation of these three threatened taxa and may contribute to the success of S. umbrosus reintroduction. A multilevel analysis of chlorophyll a fluorescence transients by the JIP test permitted an in vivo evaluation of plant vitality in terms of biophysical parameters quantifying photosynthetic energy conservation, which was found to be in good agreement with the results concerning physiological parameters. Therefore, the JIP test can be used to evaluate the influence of AMF on endangered plants, with the additional advantage of being applicable in monitoring in a noninvasive way the acclimatization of reintroduced species in nature.     

Phenotypic plasticity in rice: responses to fertilization and inoculation with arbuscular mycorrhizal fungi

Aims Changes in the phenotype of crops (phenotypic plasticity) are known to play an important role in determining responses to nutrient availability, with the direction and magnitude of plasticity of individual traits being crucial for grain yields. Our study analysed the direction, magnitude and hierarchy of plastic responses of yield-related traits (i.e. biomass allocation and yield components) of rice (Oryza sativa L.) to nutrient availability. We estimated the effect of inoculation with arbuscular mycorrhizal fungi (AMF) on these characteristics of phenotypic plasticity.Methods A field experiment was carried out in northeast China, providing rice with six NPK fertilizer levels with or without inoculation with Glomus mosseae. At maturity, we quantified biomass allocation traits (shoot:root ratio and panicle:shoot ratio) and yield component traits (panicle number per hill, spikelet number per panicle, percentage of filled spikelets and seed weight). We also assessed the direction of change in each trait and the magnitude of trait plasticity.Important findings In non-inoculated plants, we found that biomass allocation and seed-number traits (i.e. panicle number per hill, spikelet number per panicle and percentage of filled spikelets) responded to fertilization in the same direction, increasing with rising fertilization. Panicle formation was the most plastic trait, while seed mass was the least plastic trait. AMF inoculation nullified the relationship between most biomass allocation and seed-number traits (except for that between panicle:shoot ratio and the percentage of filled spikelets) but increased the magnitude of plasticity in biomass allocation traits without altering the hierarchy of traits' plasticity. These results underscore the importance of plasticity of yield-related traits per se, and the impact of AMF on plasticity, for maintaining rice yields under low fertilization regimes.     

丛枝菌根真菌对不同番茄品种抗根结线虫病的影响

【背景】根结线虫病害严重制约我国设施蔬菜的生产。丛枝菌根真菌(Arbuscular Mycorrhizal Fungi,AMF)作为土壤中最重要的有益真菌之一,可以促进植物生长,提高植物抗病性,减轻土传真菌和线虫病害的发生。在蔬菜保护地栽培中,AMF对于植物线虫病防治作用的研究受到了广泛关注。【目的】针对番茄生产中危害最严重的南方根结线虫(Meliodogyne incognita)病害问题,研究AMF和番茄品种不同组合的抗线虫效应,以期为菌根真菌作为生物防治剂和生物菌肥应用于实际生产提供技术基础。【方法】在灭菌土壤中,人工接种根结线虫,比较不同菌种Rhizophagus intraradices(Ri)、Acaulosporamellea(Am)及菌种组合Rhizophagusintraradices+Acaulosporamellea(Ri+Am)在不同番茄品种(感病品种蒙特卡罗和抗线虫品种仙客1号)上对南方根结线虫侵染和繁殖的影响,研究AMF对根结线虫的拮抗效应。另外,采用南方根结线虫连作发病的土壤,在感病品种蒙特卡洛上接种AMF混合菌种Ri+Am,番茄苗移栽入连作土壤中,测定各生长指标和调查根结和卵块数量,评价接种AMF处理对根结线虫病的防治效果。【结果】在灭菌土壤中,普通番茄品种蒙特卡罗的菌根效应显著优于抗线虫番茄品种仙客1号,表现为前者单位根重的根结和卵块的数量均比对照显著降低,而后者仅降低了卵块数量;蒙特卡罗上接种Ri+Am混合菌种的效果优于接种单一菌种Am和Ri;而仙客1号上接种Ri的效果更好。接种线虫也显著影响了AMF的侵染,而且对抗性品种仙客1号的影响更为明显。但除了接种Am的处理,大多数处理收获时菌根侵染率仍维持较高的水平(70%以上)。在连作土壤中,感病品种蒙特卡罗接种混合菌种Ri+Am具有较好的抗/耐线虫效应,主要表现为促进植株生长,显著降低根结和卵块数量,但菌根侵染率较灭菌土壤低,约为40%。【结论】综合以上结果,表明菌根化苗能够在一定程度上减轻根结线虫病的危害。土壤灭菌条件下,在感病和抗线虫番茄品种上接种AMF能够减轻线虫的侵染和繁殖,而且在感病品种上的防治效果更加显著。在连作土壤中,在番茄感病品种上接种AMF也表现较好的抗线虫效果。     

Effect of arbuscular mycorrhizal fungi inoculation on root traits and root volatile organic compound emissions of Sorghum bicolor

Volatile organic compounds (VOCs) emitted by plant roots have important functions that can influence the rhizospheric environment. The aim of this study was to examine the effects of arbuscular mycorrhizal (AM) fungi on the profile of root VOCs. Sorghum (Sorghum bicolor) plants were grown in pots inoculated with either Glomus mosseae or Glomus intraradices, which formed mycorrhiza with the roots. Control plants were grown in pots inoculated with sterile inoculum and did not form mycorrhiza. Forty-four VOCs were determined using headspace solid-phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC-MS). Alkanes were the most abundant type of VOCs emitted by both mycorrhizal and non-mycorrhizal plants. Both the quantity and type of volatiles were dramatically altered by the presence of AM fungi, and these changes had species specificity. Compared with non-mycorrhizal plants, mycorrhizal plants emitted more alcohols, alkenes, ethers and acids but fewer linear-alkanes. The AM fungi also influenced the morphological traits of the host roots. The total root length and specific root length of mycorrhizal plants were significantly greater than those of non-mycorrhizal plants; however, both the incidence and length of root-hair were dramatically decreased. Our findings confirm that AM fungi can alter the profile of VOCs emitted by roots as well as the root morphology of sorghum plants, indicating that AM fungi have the potential to help plants adapt to and alter soil environments.     

Biolistic transformation of arbuscular mycorrhizal fungi

Gene transfer systems have proved effective for the transformation of a range of organisms for both fundamental and applied studies. Biolistic transformation is a powerful method for the gene transfer into various organisms and tissues that have proved recalcitrant to more conventional means. For fungi, the biolistic approach is particularly effective where protoplasts are difficult to obtain and/or the organisms are difficult to culture. This is particularly applicable to arbuscular mycorrhizal (AM) fungi, being as they are obligate symbionts that can only be propagated in association with intact plants or root explants. Furthermore, these fungi are aseptate and protoplasts cannot be released. Recent advancements in gene transformation systems have enabled the use of biolistic technology to introduce foreign DNA linked to molecular markers into these fungi. In this review we discuss the development of transformation strategies for AM fungi by biolistics and highlight the areas of this technology which require further development for the stable transformation of these elusive organisms.     

Microbial inoculation influences arbuscular mycorrhizal fungi community structure and nutrient dynamics in temperate tree restoration

Soil microbial communities have a profound influence on soil chemical processes and subsequently influence tree nutrition and growth. This study examined how the addition of a commercial inoculum or forest‐collected soils influenced nitrogen (N) and phosphorus (P) dynamics, soil microbial community structure, and growth in Liriodendron tulipifera and Prunus serotina tree saplings. Inoculation method was an important determinant of arbuscular mycorrhizal fungi (AMF) community structure in both species and altered soil N dynamics in Prunus and soil P dynamics in Liriodendron. Prunus saplings receiving whole forest soil transfers had a higher rhizosphere soil carbon/nitrogen ratio and ammonia content at the end of the first growing season when compared to unmanipulated control saplings. Inoculation with whole forest soil transfers resulted in increased inorganic phosphorus in Liriodendron rhizosphere soils. The number of AMF terminal restriction fragments was significantly greater in rhizosphere soils of Liriodendron saplings inoculated with whole forest soil transfers and Prunus saplings receiving either inoculum source than control saplings. Forest soil inoculation also increased AMF colonization and suppressed stem elongation in Liriodendron after 16 months; conversely, Prunus AMF colonization was unchanged and stem elongation was significantly greater when saplings were inoculated with whole forest soil transfers. Longer term monitoring of tree response to inoculation will be essential to assess whether early costs of AMF colonization may provide long‐term benefits. This study provides insight into how practitioners can use microbial inoculation to alter AMF community structure and functioning, subsequently influencing tree growth and nutrient cycling during the restoration of degraded lands.     

Use of sucrose-agar globule with root exudates for mass production of vesicular arbuscular mycorrhizal fungi

A sucrose-agar globule (SAG) was newly introduced to increase production of the vesicular arbuscular mycorrhizal (VAM) fungal spores, Gigaspora gigantea and Glomus fasciculatum. An SAG inoculum and a sucrose-agar globule with root exudates (SAGE) inoculum were prepared, and their spore productions were compared with a soil inoculum. When the SAGE was used as the inoculum on sucrose-agar medium plates the number of spores was increased (35% more than the soil inoculum). After the soil inoculum and SAGE were inoculated on an experimental plant, Zingiber officinale, the percentage root colonization, number of VAM spores, and dry matter content were analyzed. It was observed that the SAGE showed a higher percentage of root colonization (about 10% more), and increases in the number of spores (about 26%) and dry matter (more than 13%) for the two VAM fungal spores than the soil inoculum. The results of this study suggested that the SAGE inoculum may be useful for the mass production of VAM fungi and also for the large scale production of VAM fungal fertilizer.     

Genetic processes in arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi (Glomeromycota) colonize roots of the majority of land plants and facilitate their mineral nutrient uptake. Consequently, AM fungi play an important role in terrestrial ecosystems and are becoming a component of sustainable land management practices. The absence of sexual reproductive structures in modern Glomeromycota combined with their long evolutionary history suggest that these fungi may represent an ancient asexual lineage of great potential interest to evolutionary biology. However, many aspects of basic AM fungal biology, including genome structure, within-individual genetic variation, and reproductive mode are poorly understood. These knowledge gaps hinder research on the mechanisms of AM fungal interactions with individual plants and plant communities, and utilization of AM fungi in agricultural practices. I present here the current state of research on the reproduction in AM fungi and indicate what new findings can be expected in the future.     

Response of strawberry to inoculation with arbuscular mycorrhizal fungi under very high soil phosphorus conditions

A field study was done to assess the potential benefit of arbuscular mycorrhizal (AM) inoculation of elite strawberry plants on plant multiplication, under typical strawberry nursery conditions and, in particular, high soil P fertility (Mehlich-3 extractible P=498 mg kg⁻¹). Commercially in vitro propagated elite plants of five cultivars (‘Chambly,’ ‘Glooscap,’ ‘Joliette,’ ‘Kent,’ and ‘Sweet Charlie’) were transplanted in noninoculated growth substrate or in substrate inoculated with Glomus intraradices or with a mixture of species (G. intraradices, Glomus mosseae, and Glomus etunicatum) at the acclimation stage and were grown for 6 weeks before transplantation in the field. We found that AM fungi can impact on plant productivity in a soil classified as excessively rich in P. Inoculated mother plants produced about 25% fewer daughter plants than the control in Chambly (P=0.03), and Glooscap produced about 50% more (P=0.008) daughter plants when inoculated with G. intraradices, while the productivity of other cultivars was not significantly decreased. Daughter plant shoot mass was not affected by treatments, but their roots had lower, higher, or similar mass, depending on the cultivar–inoculum combination. Root mass was unrelated to plant number. The average level of AM colonization of daughter plants produced by noninoculated mother plants did not exceed 2%, whereas plants produced from inoculated mothers had over 10% of their root length colonized 7 weeks after transplantation of mother plants and ∼6% after 14 weeks (harvest), suggesting that the AM fungi brought into the field by inoculated mother plants had established and spread up to the daughter plants. The host or nonhost nature of the crop species preceding strawberry plant production (barley or buckwheat) had no effect on soil mycorrhizal potential, on mother plant productivity, or on daughter plant mycorrhizal development. Thus, in soil excessively rich in P, inoculation may be the only option for management of the symbiosis.     

Growth response of Atriplex nummularia to inoculation with arbuscular mycorrhizal fungi at different salinity levels

Chenopods are generally regarded as non-host plants for mycorrhizal fungi and are believed not to benefit from colonization by mycorrhizal fungi. Perennial Atriplex nummularia Lindl., growing under field conditions, showed a relatively high level of colonization by mycorrhizal fungi (10–30% of root length colonized) in spring and summer. Accordingly, two glasshouse experiments were designed to assess the effects of inoculation with mycorrhizal fungi (with a single species or a mixture of different species) on growth, nutrient uptake, and rhizosphere bacterial community composition of A. nummularia at high and low salinity levels (2.2 and 12 dSm^–1). Only low and patchy colonization by mycorrhizal fungi (1–2 of root length colonized) was detected in inoculated plants under glasshouse conditions which was unaffected by salinity. Despite the low colonization, inoculation increased plant growth and affected nutrient uptake at both salinity levels. The effects were higher at an early stage of plant development (6weeks) than at a later stage (9–10 weeks). Salinity affected the bacterial community composition in the rhizosphere as examined by ribosomal intergenic spacer amplification (RISA) of 16S rDNA, digitization of the band patterns and multivariate analysis. The effects of inoculation with mycorrhizal fungi on growth of A. nummularia may be attributed to (i) direct effects of mycorrhizal fungi on plant nutrient uptake and/or (ii) indirect effects via mycorrhizal-induced changes in the bacterial community composition.     

龙脑香科植物对丛枝菌根真菌的影响

在天然林地和温室盆栽条件下,比较研究了龙脑香科植物对丛枝菌根(Arbuscular mycorrhizas,AM)真菌孢子密度、相对多度、频度、属的组成、丰度和侵染状况等方面的影响.结果表明,用坡垒作盆栽寄主加富培养后,菌根侵染率、泡囊、丛枝和侵入点都低于原采样植物,以原坡垒土壤中栽植苗木的侵染率为最高,可达20.3%;而以望天树根围土壤栽植的苗木为最低,仅为10.6%;坡垒还不同程度地改变了原采样植物根围土壤中AM真菌孢子的密度、相对多度、频度、属的组成、丰度等.在4种土壤中,栽植坡垒苗木后,AM真菌的孢子密度都有不同程度的增长.采用与原采样相同种类的植物作为AM真菌加富培养的寄主更有利于促进AM真菌的生长发育、保持AM的多样性.     

接种后共培养时间对丛枝菌根喜树幼苗喜树碱含量的影响

在前期工作中利用蜜色无梗囊霉(Acaulospora mellea)和根内球囊霉(Glomus intraradices)从接种时期角度分析了喜树碱含量与菌根形成过程对应关系的基础上,通过温室盆栽接种试验,继续观察了这两种丛枝菌根真菌接种后与喜树(Camptothecaacuminata)幼苗的共培养时间对喜树幼苗喜树碱积累的影响。分别用两种菌根真菌每隔7d接种一批喜树幼苗,第5批接种7 d后采样,获得菌根真菌与喜树幼苗共培养时间分别为35、28、21、14、7 d的喜树幼苗样品,测定了菌根浸染状况和喜树碱含量。结果表明:(1)接种两种丛枝菌根真菌均促进了喜树幼苗喜树碱的积累,表现为喜树碱含量和产量(单株幼苗所含的喜树碱量,喜树碱含量与幼苗生物量的乘积)的显著提高。(2)从接种后共培养时间的效果看,两种菌根幼苗各器官(根、茎、叶)及全株喜树碱含量和产量均呈现随着丛枝菌根真菌与喜树幼苗共培养时间的增加而增加的趋势。两种菌根幼苗的根和茎、根内球囊霉菌根幼苗的叶片和全株的的喜树碱含量和产量,在共培养时间增加至21 d时趋于稳定,而蜜色无梗囊霉菌根幼苗的叶片和全株的喜树碱含量和产量在共培养时间增加至28 d时达到最高,其后略有降低。(3)两种丛枝菌根真菌的侵染率和侵染强度同样随共培养时间的增加而增加,至共培养28 d后无显著变化。在一定共培养时间范围内,喜树碱含量和产量的变化与丛枝菌根真菌的侵染及菌根形成之间具有对应性。     

Scale-dependent niche axes of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) are mutualistic with most species of plants and are known to influence plant community diversity and composition. To better understand natural plant communities and the ecological processes they control it is important to understand what determines the distribution and diversity of AMF. We tested three putative niche axes: plant species composition, disturbance history, and soil chemistry against AMF species composition to determine which axis correlated most strongly with a changing AMF community. Due to a scale dependency we were not able to absolutely rank their importance, but we did find that each correlated significantly with AMF community change at our site. Among soil properties, pH and NO₃ were found to be especially good predictors of AMF community change. In a similar analysis of the plant community we found that time since disturbance had by far the largest impact on community composition. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of crop rotation on native vesicular arbuscular mycorrhizal propagules in soil

The effect of crop rotation of native vesicular arbuscular mycorrhizal fungi was studied. Finger millet was grown as the first season crop in 15 plots. In the second season a mycorhizal host (cowpea) and a non-mycorrhizal host (mustard) were grown in 5 plots each, and the remaining 5 plots were left fallow. In the third season cowpea was grown in all the plots. Leaving the land fallow reduced the mycorrhizal propagules by 40% while growing a non-mycorrhizal host reduced it by 13%. Cowpea grown in the third season coincided with a slow build up of mycorrhizal propagules in soil. There was a slow build up of mycorrhizal propagules late in the season irrespective of the treatment in the preceding season.