Mycorrhizal associations in woody plant species at the Mt. Usu volcano,Japan

We investigated the association between ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) fungi and pioneer woody plant species in areas devastated by the eruption of Mt. Usu, Japan, in 2000. We observed eight woody plant species at the research site, most of which were associated with ECM and/or AM fungi. In particular, dominant woody plant species Populus maximowiczii, Salix hultenii var. angustifolia and Salix sachalinensis were consistently associated with ECM fungi and erratically associated with AM fungi. We found one to six morphotypes in the roots of each ECM host and, on average, two in the roots of each seedling, indicating low ECM fungal diversity. ECM colonization ranged from 17 to 42% of root tips. Using morphotyping and molecular analyses, 15 ECM fungi were identified. ECM fungi differed greatly between hosts. However, Laccaria amethystea, Hebeloma mesophaeum, Thelephora terrestris and other Thelephoraceae had high relative colonization, constituting the majority of the ECM colonization in the roots of each plant species. These ECM fungi may be important for the establishment of pioneer woody plant species and further revegetation at Mt. Usu volcano.     

How are plant and fungal communities linked to each other in belowground ecosystems? A massively parallel pyrosequencing analysis of the association specificity of root-associated fungi and their host plants

In natural forests, hundreds of fungal species colonize plant roots. The preference or specificity for partners in these symbiotic relationships is a key to understanding how the community structures of root‐associated fungi and their host plants influence each other. In an oak‐dominated forest in Japan, we investigated the root‐associated fungal community based on a pyrosequencing analysis of the roots of 33 plant species. Of the 387 fungal taxa observed, 153 (39.5%) were identified on at least two plant species. Although many mycorrhizal and root‐endophytic fungi are shared between the plant species, the five most common plant species in the community had specificity in their association with fungal taxa. Likewise, fungi displayed remarkable variation in their association specificity for plants even within the same phylogenetic or ecological groups. For example, some fungi in the ectomycorrhizal family Russulaceae were detected almost exclusively on specific oak (Quercus) species, whereas other Russulaceae fungi were found even on “non‐ectomycorrhizal” plants (e.g., Lyonia and Ilex). Putatively endophytic ascomycetes in the orders Helotiales and Chaetothyriales also displayed variation in their association specificity and many of them were shared among plant species as major symbionts. These results suggest that the entire structure of belowground plant–fungal associations is described neither by the random sharing of hosts/symbionts nor by complete compartmentalization by mycorrhizal type. Rather, the colonization of multiple types of mycorrhizal fungi on the same plant species and the prevalence of diverse root‐endophytic fungi may be important features of belowground linkage between plant and fungal communities.     

Resistance of pea roots to endomycorrhizal fungus or Rhizobium correlates with enhanced levels of endogenous salicylic acid

The analysis of SA accumulation in roots of plant symbiotic mutants revealed two independent phenomena associated with the inability of either the plant or the microsymbiont to form a compatible symbiosis. SA accumulation in roots of the wild type and symbiosis-resistant P2 (Nod^-, MYC^-) Pisum sativum genotypes was induced upon interaction with Glomus mosseae. The amplitude of this accumulation was higher in P2 plants and increased with time, an effect that was not observed in roots of the wild-type, an effect that was not observed in roots of the wild-type P. sativum genotype. Likewise, Rhizobium leguminosarum wild type or a mutant blocked in Nod factor biosynthesis induced SA accumulation in P2, whereas SA accumulation in roots of the wild-type plant was dependent on the inability of the bacterium to produce Nod factors. These results suggest that the sym30 gene, which is mutated in P2 plants, could be implicated in a common pathway that leads to the suppression of an SA-dependent defence mechanism in legume plants against Rhizobium and endomycorrhizal fungi, thus allowing establishment of symbiosis.     

Mycena species can be opportunist-generalist plant root invaders

Traditional strict separation of fungi into ecological niches as mutualist, parasite or saprotroph is increasingly called into question. Sequences of assumed saprotrophs have been amplified from plant root interiors, and several saprotrophic genera can invade and interact with host plants in laboratory growth experiments. However, it is uncertain if root invasion by saprotrophic fungi is a widespread phenomenon and if laboratory interactions mirror field conditions. Here, we focused on the widespread and speciose saprotrophic genus Mycena and performed (1) a systematic survey of their occurrences (in ITS1/ITS2 datasets) in mycorrhizal roots of 10 plant species, and (2) an analysis of natural abundances of ¹³C/¹⁵N stable isotope signatures of Mycena basidiocarps from five field locations to examine their trophic status. We found that Mycena was the only saprotrophic genus consistently found in 9 out of 10 plant host roots, with no indication that the host roots were senescent or otherwise vulnerable. Furthermore, Mycena basidiocarps displayed isotopic signatures consistent with published ¹³C/¹⁵N profiles of both saprotrophic and mutualistic lifestyles, supporting earlier laboratory-based studies. We argue that Mycena are widespread latent invaders of healthy plant roots and that Mycena species may form a spectrum of interactions besides saprotrophy also in the field.     

Hyphae of waxcap fungi colonise plant roots

The trophic strategy of the globally distributed waxcaps (Hygrophoraceae) is uncertain. Some clues point to a biotrophic mode, particularly the ¹³C and ¹⁵N (stable isotopes) signatures. The observation of dense basal hyphae of Hygrocybe fruit bodies being tightly attached to live fine roots may be indicative of a plant-derived nutritional habit. To further scrutinize this fungus–plant association, stipe base samples and attached plant fragments were examined histologically. Waxcap hyphae were found growing inside live fine roots of associated vegetation. Amplification and sequencing of waxcap DNA from living root tissues using species-specific PCR primers also confirmed their presence in live plant roots. We therefore conclude that this group of fungi has a biotrophic lifestyle with plants.     

Symbiotic fungi in roots of Artemisia annua with special reference to endophytic colonizers

Abstract

Advances on plant–fungal interactions reveal that root symbiotic fungi actively modulate host growth, resistance response and secondary metabolism. Artemisia annua has been widely recognized as an important medicinal plant for artemisinin production, yet little is known about the fungal consortium associated with roots of A. annua. In this article, microscopic and culture-dependant methods were used to evaluate the identity and taxonomic affinities of root symbiotic fungi. Morphological evidence confirmed that arbuscular mycorrhizal fungi were dominant fungal group in naturally regenerated roots, but low colonization frequency in planted roots. Dark septate endophytes (DSEs) were easily found, which were characterized with dark pigmented hypha and a sclerotium-like structure in root cortex, and other endophytic fungi also occurred. A total of 36 isolates were recovered. Combined morphological and molecular identification (based on ITS sequences) determined 21 fungal taxa (genotype), which were placed into numerous lineages of Ascomycota. The best BLAST match indicated that almost half of total taxa were closely related to undescribed fungi, some of them may act as novel DSEs but experimental data were warranted. Interestingly, remarkable difference of fungal community associated with two types of roots was examined and no culturable fungi overlapped. Our findings provide some additional evidence that DSEs and other root endophytes may be as common as mycorrhizal fungi. Recovered fungi as raw materials for bioassay of endophytes-mediated promotion of artemisinin content in A. annua will be conducted in further research.     

濒危药用植物掌裂兰根部内生真菌和根际土真菌多样性分析

【背景】植物内生真菌对宿主植物促生长、抗旱和增强抗病能力等方面有着重大的研究和利用价值,尤其对兰科植物的生长起到重要的作用。【目的】通过对掌裂兰根部内生真菌和根际土真菌多样性进行系统分析,掌握掌裂兰根部内生真菌与根际土真菌群落结构,为进一步探究掌裂兰植物与真菌共生规律提供参考。【方法】采用Illumina MiSeq高通量测序技术分析掌裂兰根部内生真菌和根际土真菌多样性。【结果】掌裂兰根部内生真菌隶属于7门89属,优势菌属为瘤菌根菌属(Epulorhiza)(16.93%)、头梗霉属(Cephaliophora)(10.41%)、酵母属(Saccharomyces)(5.73%)、角担菌属(Ceratobasidium)(5.32%)和镰刀菌属(Fusarium)(5.12%),其中Epulorhiza和Ceratobasidium为兰科植物菌根真菌;根际土真菌隶属于11门269属,优势菌属为镰刀菌属(Fusarium)(8.09%)、丛赤壳属(Neonectria)(6.79%)、Plectosphaerella (3.39%)和被孢霉属(Mortierella)(3.01%)。通过...     

Phosphorus uptake by a community of arbuscular mycorrhizal fungi in jarrah forest

Communities of indigenous arbusuclar mycorrhizal (AM) fungi are expected to alter phosphorus uptake and biomass productivity of plants according to characteristics of the life cycles of the fungi present and the way they interact with each other inside roots and with host plants. Differences in the relative abundance of AM fungi inside roots could influence P uptake if the fungi present differ in effectiveness at accessing P and transferring it to the plant. However, it is difficult to assess the contribution of AM fungi under field conditions. We investigated P uptake, from point sources of P placed 2, 4 and 6 cm from roots, by plants colonised by a community of AM fungi in jarrah forest soil. Roots were retained within a mesh bag to prevent them from growing towards the point source of P. The relative abundance of morphotypes of fungi inside roots and the P status of plants were assessed after 12 and 16 weeks. First, a bioassay was carried out in undisturbed forest soil cores using two host plants, a forest understorey plant Phyllanthus calycinus Labill and the annual pasture species subterranean clover (Trifolium subterraneaumL.), to assess the infectivity of the indigenous community of AM fungi. Roots of both bioassay host plants were colonised in similar proportions by morphotypes of AM fungi resembling Glomus, Acaulospora, Scutellospora and fine endophytes. In this bioassay, there were positive correlations between the proportion of root length colonised and plant biomass and P uptake for P. calycinus, but not for subterranean clover. In the experiment assessing the capacity of P. calycinus to access P placed at increasing distances from the root, shoot P content and concentration in P. calycinus were greater when P was placed 2 cm compared with 4 and 6 cm from roots. The length of hyphae in the vicinity of the point source of P decreased with increasing distance from the plant. The extent to which the individual AM fungi were involved in P uptake is not known. The Glomus morphotype was dominant at both times of sampling.     

Trade-offs between arbuscular mycorrhizal fungal competitive ability and host growth promotion in Plantago lanceolata

In this study we tested for trade-offs between the benefit arbuscular mycorrhizal (AM) fungi provide for hosts and their competitive ability in host roots, and whether this potential trade-off shifts in the presence of a plant stress (herbivory). We used three species of AM fungi previously determined to vary in host growth promotion and spore production in association with host plants. We found that these AM fungal species competed for root space, and the best competitor, Scutellospora calospora, was the worst mutualist. In addition, the worst competitor, Glomus white, was the best mutualist. Competition proved to have stronger effects on fungal infection patterns than herbivory, and competitive dominance was not altered by herbivory. We found a similar pattern in a previous test of competition among AM fungi, and we discuss the implications of these results for the persistence of the mutualism and feedbacks between AM fungi and their plant hosts.     

Context‐dependent effects of mycorrhizae on herbivore density and parasitism in a tritrophic coastal study system

1. Stressful abiotic conditions and mycorrhizal fungi have both been shown to influence plant quality significantly, yet the interactive effects of these factors on relationships among plants, herbivores, and natural enemies remain unclear. 2. In this study, the results of a factorial field experiment are reported in which the effects of plant stress and mycorrhizae on density and parasitism of three herbivores of Baccharis halimifolia L. were examined. 3. Plant stress was increased by adding salt to the soil, and association with mycorrhizal fungi was increased by inoculating plant roots. 4. Inoculation with mycorrhizal fungi resulted in increased density of all three herbivore species, but the effects of mycorrhizae on parasitism varied by species and with soil salinity levels. For the gall maker Neolasioptera lathami Gagne, mycorrhizae decreased parasitism regardless of soil salinity levels. For the leaf miners Amauromyza maculosa Malloch and Liriomyza trifolii Burgess, mycorrhizae effectively negated the decrease in parasitism resulting from increased salinity. 5. The results of this study show that the effects of mycorrhizae on parasitism may be context dependent, and can be positive or negative depending upon species and environmental conditions.     

Boron uptake by ectomycorrhizas of silver birch

Boron (B) is an essential micronutrient for plants but it is thought not to be essential for fungi. We studied whether the extraradical mycelia of Paxillus involutus in symbiosis with silver birch (Betula pendula) take up B and transport it to the host plant. We grew mycorrhizal plants in flat microcosms with a partitioning wall, below which there was only extraradical mycelium. A boric acid solution enriched in ¹⁰B was applied to these mycelia. Increased ¹⁰B/¹¹B isotope ratios were subsequently measured in birch leaves, stems, and roots plus mycorrhizas in the upper compartment. Boron was therefore taken up by the mycorrhizal mycelia and transported to the host plant in this species combination.     

Molecular diversity of fungi from ericoid mycorrhizal roots

In order to investigate the diversity of fungal endophytes in ericoid mycorrhizal roots, about 150 mycelia were isolated from surface-sterilized roots of 10 plants of Calluna vulgaris. Each mycelium was reinoculated to C. vulgaris seedlings under axenic conditions, and the phenotype of the plant-fungus association assessed by light and electron microscopy. Many isolates that were able in vitro to produce typical ericoid mycorrhizae did not form reproductive structures under our culture conditions, whereas others could be identified as belonging to the species Oidiodendron maius. Morphological and molecular analysis of the fungal isolates showed that the root system of a single plant of C. vulgaris is a complex mosaic of several populations of mycorrhizal and non mycorrhizal fungi. PCR-RFLP techniques, used to investigate the mycorrhizal endophytes, revealed up to four groups of fungi with different PCR-RFLP patterns of the ITS ribosomal region from a single plant. Some of the mycorrhizal fungi sharing the same PCR-RFLP pattern showed high degree of genetic polymorphism when analysed with the more sensitive RAPD technique; this technique may prove a useful tool to trace the spread of individual mycorrhizal mycelia, as it has allowed us to identify isolates with identical RAPD fingerprints on different plants.     

Differential strategies of two species of arbuscular mycorrhizal fungi in the protection of maize plants grown in chromium-contaminated soils

Chromium (Cr) is a nonessential element for plants that is extremely toxic at high concentrations. Zea mays L. is a species of plant that has developed adaptive mechanisms to increase its tolerance and absorption capacity for this metal. One effective mechanism is to form associations with arbuscular mycorrhizal fungi (AMF), which help the plant cope with stress from heavy metals such as Cr. However, it is still not clear which species of AMF are more efficient as bioremediating agents for plants of agricultural importance. Here, we evaluated the effect of Gigaspora gigantea and Rhizophagus irregularis as protective agents of maize plants in soils contaminated with Cr at concentrations of 0, 48.5, 97 and 194 mg kg^?1 under greenhouse conditions. Maize tolerance to Cr was corroborated, as well as increased absorption of this element by plants associated with both species of AMF. G. gigantea caused an increase in nitrogen content and greater translocation of Cr to the aerial part of the plant; R. irregularis registered an increase in the formation of arbuscules and vesicles with increasing metal concentration and greater retention of Cr in the roots of the plants. Based on these results, we can conclude that the analyzed species of fungi use different strategies, with similar effectiveness, to enhance the absorption capacity of Cr by the plant and influence the differential deposition of this metal in various parts of the plant.

     

Studies on fungi in the root region

Summary Tabulated information on the colonization of roots of barley, cabbage and dwarf bean by fungi during the first 10 days of root development is given. These data, obtained by isolation and direct observation studies, are discussed in relation to previous observations on the association of fungi with the roots of healthy crop plants.The results indicate that initial root colonization may be by any of a wide range of soil fungi, but that this mixed population rapidly gives way to a stable and typical root-surface mycoflora (dominated by such fungi asFusarium spp.,Cylindrocarpon radicicola, Gliocladium spp., andPenicillium spp.     

Nested multiplex PCR—A feasible technique to study partial community of arbuscular mycorrhizal fungi in field-growing plant root

Plant can be infected by different arbuscular mycorrhizal fungi, but little is known about the interaction between them within root tissues mainly because different species cannot be distinguished on the basis of fungal structure. Accurate species identification of Arbuscular mycorrhizal fungi (AMF) colonized in plant roots is the comerstone of mycorrhizal study, yet this fundamental step is impossible through its morphological character alone. For accurate, rapid and inexpensive detection of partial mycorrhizal fungal community in plant roots, a nested multiplex polymerase chain reaction (PCR) was developed in this study. Five discriminating primers designed based on the variable region of the 5′ end of the large ribosomal subunit were used in the experiment for testing their specificity and the sensitivity in nested PCR by using spores from Glomus mosseae (BEG12), Glomus intraradices (BEG141), Scutellospora castaneae (BEG1) and two unidentified Glomus sp. HAUO3 and HAUO4. The feasibility assay of nested multiplex PCR was conducted by use of spore mixture, Astragalus sinicum roots co-inoculated with 4 species of arbuscular mycorrhizal fungi from pot cultures and 15 different field-growing plant roots respectively after analyses of the compatibility of primers. The result indicated that the sensitivity was in the same range as that of the corresponding single PCR reaction. Overall accuracy was 95%. The efficiency and sensitivity of this multiplex PCR procedure provided a rapid and easy way to simultaneously detect several of arbuscular mycorrhizal fungal species in a same plant root system.     

Strigolactones stimulate arbuscular mycorrhizal fungi by activating mitochondria

The association of arbuscular mycorrhizal (AM) fungi with plant roots is the oldest and ecologically most important symbiotic relationship between higher plants and microorganisms, yet the mechanism by which these fungi detect the presence of a plant host is poorly understood. Previous studies have shown that roots secrete a branching factor (BF) that strongly stimulates branching of hyphae during germination of the spores of AM fungi. In the BF of Lotus, a strigolactone was found to be the active molecule. Strigolactones are known as germination stimulants of the parasitic plants Striga and Orobanche. In this paper, we show that the BF of a monocotyledonous plant, Sorghum, also contains a strigolactone. Strigolactones strongly and rapidly stimulated cell proliferation of the AM fungus Gigaspora rosea at concentrations as low as 10 ⁻¹³ M. This effect was not found with other sesquiterperne lactones known as germination stimulants of parasitic weeds. Within 1 h of treatment, the density of mitochondria in the fungal cells increased, and their shape and movement changed dramatically. Strigolactones stimulated spore germination of two other phylogenetically distant AM fungi, Glomus intraradices and Gl. claroideum. This was also associated with a rapid increase of mitochondrial density and respiration as shown with Gl. intraradices. We conclude that strigolactones are important rhizospheric plant signals involved in stimulating both the pre-symbiotic growth of AM fungi and the germination of parasitic plants.     

Nested multiplex PCR——A feasible technique to study partial community of arbuscular mycorrhizal fungi in field-growing plant root

Plant can be infected by different arbuscular mycorrhizal fungi, but little is known about the interaction between them within root tissues mainly because different species cannot be distinguished on the basis of fungal structure. Accurate species identification of Arbuscular mycorrhizal fungi (AMF) colonized in plant roots is the comerstone of mycorrhizal study, yet this fundamental step is impossible through its morphological character alone. For accurate, rapid and inexpensive detection of partial mycorrhizal fungal community in plant roots, a nested multiplex polymerase chain reaction (PCR) was developed in this study. Five discriminating primers designed based on the variable region of the 5′ end of the large ribosomal subunit were used in the experiment for testing their specificity and the sensitivity in nested PCR by using spores from Glomus mosseae (BEG12), Glomus intraradices (BEG141), Scutellospora castaneae (BEG1) and two unidentified Glomus sp. HAUO3 and HAUO4. The feasibility assay of nested multiplex PCR was conducted by use of spore mixture, Astragalus sinicum roots co-inoculated with 4 species of arbuscular mycorrhizal fungi from pot cultures and 15 different field-growing plant roots respectively after analyses of the compatibility of primers. The result indicated that the sensitivity was in the same range as that of the corresponding single PCR reaction. Overall accuracy was 95%. The efficiency and sensitivity of this multiplex PCR procedure provided a rapid and easy way to simultaneously detect several of arbuscular mycorrhizal fungal species in a same plant root system.     

Use of strontium isotopes and foliar K content to estimate weathering of biotite induced by pine seedlings colonised by ectomycorrhizal fungi from two different soils

Pinus sylvestris seedlings, colonised by ectomycorrhizal (EM) fungi from either of two different soils (untreated forest soil and a limed soil from a clear cut area), were grown with or without biotite as a source of K. The biotite was naturally enriched in ⁸⁷Sr and the ratio of ⁸⁷Sr/ ⁸⁶Sr in the plant biomass was estimated and used as a marker for biotite weathering and compared to estimates of weathering based on foliar content of K. Different nutrient regimes were used to expose the seedlings to deficiencies of K with and without an application of nitrogen (NH₄NO₃) in excess of seedling demand. The seedlings were grown for 220 days and the elemental composition of the shoots were analysed at harvest. The EM colonisation was followed by analysing the concentration of ergosterol in the roots and the soils. Bacterial activity of the soil was estimated by the thymidine incorporation technique. The concentration of organic acids in the soil solution was measured in the soil in which seedlings colonised by EM fungi from the untreated forest soil were grown. It was found that seedlings colonised by EM fungi from untreated forest soil had taken up more K in treatments with biotite addition compared to seedlings colonised by EM fungi from the limed forest soil (p<0.05). Seedlings from untreated forest soil had larger shoots and contained more K when grown with biotite compared to KCl as K source, indicating that biotite had a stimulatory effect on the growth of these seedlings which was not related to K uptake. Seedlings from the limed soil, on the other hand, had similar foliar K content when grown with either biotite or KCl as K source. The larger uptake of K in seedlings from untreated forest soil was not an effect of a more developed EM colonisation of the roots since seedlings from the limed soil had a higher ergosterol concentration both in the soil and in the roots. Nutrient regimes had no significant influence on the total uptake of K but the ⁸⁷Sr/ ⁸⁶Sr isotope ratio in the plant biomass indicated that seedlings grown with excess nitrogen supply had taken up proportionally less Sr from the biotite (1.8% of total Sr content) compared to seedlings grown with a moderate nitrogen supply (5.0%). Furthermore, seedlings grown with excess nitrogen supply had a reduced fungal colonisation of roots and soil and bacterial activity was lower in these soils. The ⁸⁷Sr/ ⁸⁶Sr ratio in the plant biomass was positively correlated with fungal colonisation of the roots (r ²=0.98), which may indicate that the fungus was involved in releasing Sr from the biotite. Uptake of K from biotite was not related to the amount of organic acids in the soil solution. Oxalic acid was positively related to the amount of ergosterol in the root, suggesting that oxalic acid in the soil solution originates from the EM symbionts. The accuracy of the estimations of biotite weathering based on K uptake by the seedlings in comparison with the ⁸⁷Sr/⁸⁶Sr isotope ratio measured in the shoots is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

The survival and development of inoculant ectomycorrhizal fungi on roots of outplanted Eucalyptus globulus Labill

The survival and development of two inoculant ectomycorrhizal fungi (Hebeloma westraliense Bough. Tom. and Mal. and Setchelliogaster sp. nov.) on roots of outplanted Eucalyptus globulus Labill. was examined at two expasture field sites in the south-west of Western Australia. Site 1 was a gravelly yellow duplex soil, and Site 2 was a yellow sandy earth. Plants were grown in steamed or unsteamed soil, in root bags designed as field containers for young growing trees. Three, 6 and 12 months after outplanting, plants were removed from these bags and assessed for dry weights of shoots and ectomycorrhizal colonization of roots.The inoculant ectomycorrhizal fungi (identified on the basis of the colour and morphology of their mycorrhizas) survived on roots of E. globulus for at least 12 months after outplanting at both field sites. At Site 1, however, colonization of new fine roots by the inoculant fungi was low (less than 20% of fine root length). Inoculation had no effect on the growth of E. globulus at this site. In contrast, at Site 2 the inoculant ectomycorrhizal fungi colonized up to 30–50% of new fine root length during the first 6 months after outplanting. There was a corresponding growth response to ectomycorrhizal inoculation at this site, with a close relationship (r²=0.82^**) between plant growth at 12 months and root colonization at 3 months. Plant growth at 12 months was related less closely with root colonization at 6 or 12 months. Root colonization by resident ectomycorrhizal fungi increased with time at both field sites. At Site 2, this increase appeared to be at the expense of colonization by the inoculant fungi, which was reduced to less than 10% of fine root length at 12 months. Steaming the soil had little effect on colonization by the inoculant ectomycorrhizal fungi at either field site, but decreased colonization by the resident ectomycorrhizal fungi.     

Genetically Transformed Plant Roots as a Model for Studying Specific Metabolism and Symbiotic Contacts of the Root System

Genetic transformation of plants mediated by Ri plasmid ofAgrobacterium rhizogenes occupies a special place in plant cell engineering, since this technique based on a natural phenomenon allows cultivation of isolated growing plant roots on hormone-free media. Application of wild-type unmodified agrobacterial strains allows us to obtain root cultures capable of long-term growth in vitro due to an increased sensitivity of the cells to auxins while other biochemical properties remain unaltered. A collection of pRi T-DNA transformed roots of certain dicotyledons was made; some strains in it are used to study synthesis of secondary metabolites in root cells. Thein vitro cultivated roots could synthesize root-specific metabolites, which makes possible their application for large-scale biotechnological production of ecologically pure crude drugs. Cocultivation of pRi T-DNA transformed roots with arbuscular mycorrhizal fungi makes possible vital study of all stages of obligate symbiont development and interaction with plant roots. Dual axenic culture of AM fungi and pRi T-DNA transformed plants can be used to make a collection of the most valuable endomycorrhizal fungal species and to produce considerable quantities of homogeneous fungal inoculums.