Dark Septate Endophytes Colonization Research Articles

Mutualism-parasitism paradigm synthesized from results of root-endophyte models.

Plant tissues host a variety of fungi. One important group is the dark septate endophytes (DSEs) that colonize plant roots and form characteristic intracellular structures – melanized hyphae and microsclerotia. The DSE associations are common and frequently observed in various biomes and plant taxa. Reviews suggest that the proportion of plant species colonized by DSE equal that colonized by AM and microscopic studies show that the proportion of the root system colonized by fungi DSE can equal, or even exceed, the colonization by AM fungi. Despite the high frequency and suspected ecological importance, the effects of DSE colonization on plant growth and performance have remained unclear. Here, we draw from over a decade of experimentation with the obscure DSE symbiosis and synthesize across large bodies of published and unpublished data from Arabidopsis thaliana and Allium porrum model systems as well as from experiments that use native plants to better resolve the host responses to DSE colonization. The data indicate similar distribution of host responses in model and native plant studies, validating the use of model plants for tractable dissection of DSE symbioses. The available data also permit empirical testing of the environmental modulation of host responses to DSE colonization and refining the “mutualism-parasitism-continuum” paradigm for DSE symbioses. These data highlight the context dependency of the DSE symbioses: not only plant species but also ecotypes vary in their responses to populations of conspecific DSE fungi – environmental conditions further shift the host responses similar to those predicted based on the mutualism-parasitism-continuum paradigm. The model systems provide several established avenues of inquiry that permit more detailed molecular and functional dissection of fungal endophyte symbioses, identifying thus likely mechanisms that may underlie the observed host responses to endophyte colonization.

Colonization of dark septate endophytes in roots of Ammopiptanthus mongolicus and its associated plants as influenced by soil properties

Aims Dark septate endophytes (DSE) are commonly detected in plant roots in different ecosystems. However, so far our knowledge about the ecological significance of DSE in semiarid and arid lands is limited. The main objec- tive of this study was to compare the colonization status and ecological distribution of DSE in Ammopiptanthus mongolicus and its associated plants in desert habitats. Methods In July 2013, soil and root samples of A. mongolicus and its associated plants were collected from three sites, including Yinchuan, Shapotou and Minqin located in northwest China. At each sampling site, samples were collected at five depth intervals, 0-10, 10-20, 20-30, 30-40 and 40-50 cm, respectively. Important findings The roots of A. mongolicus and its associated plants were infected by DSE which could be characterized by typical septate hyphae and microsclerotia. Microsclerotia of A. mongolicus were compact lumps, while the associated plants had scattered microsclerotia. In the same site, microsclerotia colonization in A. mongo- licus and its associated plants showed no significant difference, but hyphal colonization, colonization intensity and total colonization of A. mongolicus were much higher than that of its associated plants. In different sites, the colo- nization intensity and total colonization of DSE in A. mongolicus exhibited a pattern as Shapotou > Yinchuan > Minqin, and these indexes in associated plants were Yinchuan > Minqin > Shapotou. Plant species and soil layer had significant effects on the colonization and distribution of DSE as well as soil properties. The path coefficient and principal component analysis indicated that soil organic matter, total extractable glomalin, phosphatase and available K are the main influencing factors, which directly affected the colonization of DSE in desert environ- ment, Northwest China.

Soil chemistry properties, translocation of heavy metals, and mycorrhizal fungi associated with six plant species growing on lead-zinc mine tailings

The aim of this study was to investigate the relationships between soil chemistry properties and mycorrhizal fungi in the rhizosphere soils and roots of six dominant plant species grown on Qiandongshan Pb-Zn mine tailings in China. Nested polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the community composition of arbuscular mycorrhizal fungi (AMF) in the rhizosphere soils and roots of six plant species, including Astragalus adsurgens, Artemisia brachyloba, Potentilla anserina, Phragmites australis, Macleaya cordata, and Gueldenstaedtia stenophylla. Pearson's correlation coefficients were calculated to determine the relationships between soil chemistry properties and AMF and dark septate endophytic (DSE) fungal colonization, glomalin-related soil protein (GRSP) content in soil, and AMF species richness and diversity. Correlation analysis showed that the mycorrhizal colonization rate and GRSP content had close relationships with some soil chemistry properties. AMF colonization had significant effects on the translocation of Zn (r = −0.85, P < 0.05), while DSE colonization was negatively correlated with the translocation of Pb (r = −0.88, P < 0.05). In addition, total Zn content in soil influenced the AMF species richness (r = −0.87, P < 0.05) and diversity index (r = −0.92, P < 0.05). However, no correlation was found between the measured soil chemistry properties and the AMF species richness and diversity in the plant roots. Redundancy analysis (RDA) revealed a significant effect of Pb content in soil on AMF community structure in soil samples (F = 1.382, P = 0.030), and canonical correspondence analysis (CCA) of DGGE profiles showed that soil organic matter had a significant relationship with AMF community structure in the roots (F = 1.582, P = 0.038).

Colonization of arbuscular mycorrhizal fungi and dark septate endophytes in roots of desert Salix psammophila

Aims Salix psammophila is an excellent shrub for afforestation and sand dune fixation and is mainly distributes in the arid zones in North China. The objective of this study was to determine the colonization of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE), and the relationships among AMF, DSE and soil factors in the rhizosphere of S. psammophila, in order to provide information guiding the recovery of desert vegetation and ecological reconstruction. Methods Soil and root samples were collected from different soil layers (0–10, 10–20, 20–30, 30–40 and 40–50 cm) in the rhizosphere of S. psammophila in June, August and October 2013 at Yuan Shangdu in Nei Mongol. The colonization and distribution of AMF and DSE were assessed, and the relationships among AMF, DSE and soil factors were determined and tested by variance analysis, correlation analysis and principal component analysis. Important findings The roots of S. psammophila could be highly infected by AMF and DSE, and the average colonization of AMF and DSE were 77% and 84%, respectively. Sampling time and soil depth significantly influenced the AMF and DSE colonization. The maximum colonization of AMF was found in the 0–20 cm soil layer and DSE in the 0–10 cm soil layer, respectively, and the effects of sampling time on colonization were in the order of October > August > June. Two-way ANOVA showed that sampling time and soil layer had significant interactive effects on the colonization and distribution of AMF and DSE as well as soil factors. Principal component analysis showed that soil humidity, pH value, alkaline phosphatase and easily extractable glomalin were the main factors of AMF and DSE colonization in desert environments.

Colonization Characteristics and Composition of Dark Septate Endophytes (DSE) in a Lead and Zinc Slag Heap in Southwest China

The colonization characteristics and diversity of dark septate endophytes (DSE) associated with plants growing in a lead and zinc slag heap with a more than 250-year history in southwestern China were assessed. A total of 117 plant samples belonging to 29 species and 19 families were examined, and 97% (28/29) were colonized by dark septate fungal hyphae or microsclerotia. DSE colonization intensity varied greatly across plant species and also across individuals of the same species, showing a hyphal colonization range of 0.0–35.7%. In total, 38 melanized root-associated fungi with various morphological characteristics were isolated and 82% (31/38) of fungi were closely related to well-known DSE fungi, such as Exophiala spp., Phialophora (= Cadophora) spp., Phialocephala spp., and Leptodontidium spp. Among these, Phialophora and Exophiala were the dominant genera. Our results showed that DSE dominantly colonized the roots of the pioneer plants growing in such an ancient Pb-Zn slag heap. By contributing to metal tolerance and nutrient acquisition, DSE may be integral to the function of metal mine ecosystems.

Arbuscular mycorrhizal and dark septate endophytic fungi at 5,500 m on a glacier forefront in the Qinghai-Tibet Plateau, China

Arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungi are rarely studied at extremely high elevations. Here, AM and DSE colonization in two dominant plant species (Melandrium apetalum and Poa litwinowiana) were microscopically observed on the forefront of Zhadang Glacier (5,500 m above sea level) in the Qinghai-Tibet Plateau, China. The AM fungal taxa were also identified by molecular methods. Both AM and DSE fungi synchronously colonized these two plant species, but AM dominated in M. apetalum and DSE dominated in P. litwinowiana. A total of five AM fungal spore morphotypes (Acaulospora capsicula, Diversispora sp., Glomus constrictum, G. eburneum and Glomus sp.) were found in the rhizosphere soils. Molecular identification revealed two AM fungal phylotypes: one Claroideoglomus phylotype from roots and one Diversispora phylotype from spores. These results extend the elevation at which both AM and DSE are known to occur.

Growth response, phosphorus content and root colonization of Polylepis australis Bitt. seedlings inoculated with different soil types

Polylepis forests are one of the most endangered high mountain ecosystems of South America and reforestation with native Polylepis species has been highly recommended. Greenhouse bioassays were set up to determine the influence of three different soils on growth and phosphorous nutrition of Polylepis australis seedlings. Soils were collected from a grassland, a rare mature forest and a forest degraded due to repeated fires. We identified the arbuscular mycorrhizal fungi (AMF) present in the three soils and after 12 months we harvested the seedlings to evaluate root and shoot biomass, plant P content and root colonization by native AMF and dark septate endophytes (DSE). The soil inocula contained 26 AMF morphospecies. Grassland inoculum showed the highest AMF richness, and mature forest showed a different AMF community assembly from grassland and degraded forest inocula. Root biomass and root colonization were highest in seedlings inoculated with mature forest soil, meanwhile shoot biomass and plant P content were similar between all treatments. AMF colonization correlated negatively with DSE and root biomass was negatively correlated with DSE colonization, thus these fungal symbionts could be competing for resources. Our results indicate that AMF inoculum from the mature forest stand has the potential to improve P. australis performance, probably due to the dominance of Glomeraceae and Acaulosporaceae families. However, other soil microorganisms could be together with AMF in the natural inocula, affecting the growth response of P. australis seedlings. Future studies evaluating the effect of these inocula under field conditions should be carried out.

Tree species as hosts for arbuscular mycorrhizal and dark septate endophyte fungi

A survey of 35 tree species (belonging to 28 genera in 19 families) in Aliyar, South India was carried out to ascertain their arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) fungal status. All the tree species examined had AM association. AM and DSE colonization is reported for the first time in 20 and 14 species respectively. Cooccurrence of AM and DSE was observed in 14 (40%) tree species. The extent of DSE colonization was inversely related to the extent of AM fungal colonization. Six tree species had Arum-type, 18 had intermediatetype and 11 had typical Paris-type AM morphology. AM fungal spore morphotypes belonging to 11 species in two genera were isolated from the rhizosphere soil. AM fungal spore numbers were not related to the extent of AM colonization and Glomus dominated spore diversity. AM association individually and along with DSE were found respectively in the 63% and 44% of the economically important tree species. The occurrence of AM and DSE fungal association in economically important indigenous tree species indicates the possibility of exploiting this association in future conservation programmes of these species.

Root Colonization by Ericoid Mycorrhizae and Dark Septate Endophytes in Organic and Conventional Blueberry Fields in Michigan

Ericoid mycorrhizae are interfaces for nutrient exchange between specialized fungi and roots of blueberries and other ericaceous plants. Dark septate endophytes also associate with roots of the Ericaceae and many other plant families, but the nature of the interaction is not well understood. We measured ericoid mycorrhizae and dark septate endophyte colonization in organic and conventional blueberry fields matched by soil series and, if possible, cultivar and field age. The percentage of hair root cells with ericoid mycorrhizae was generally higher in organic than conventional fields, while dark septate endophyte colonization was higher in sand than muck soils. Across both muck and sandy soil types, ericoid mycorrhizal colonization was negatively correlated with field age, and dark septate endophyte colonization was negatively correlated with soil carbon, total soil nitrogen, and soil ammonium levels. When only sandy soils were included in the analysis, ericoid mycorrhizal colonization was positively correlated with soil pH and hair-root diameter, and negatively correlated with field age, soil ammonium levels, and total soil nitrogen. On sandy soils, dark septate endophyte colonization was not correlated with any measured variable. The functions of ericoid mycorrhizae and dark septate endophytes in commercial blueberry fields require further investigation.

Forest fragment size and nutrient availability: complex responses of mycorrhizal fungi in native–exotic hosts

In the past few decades, it has been widely accepted that forest loss due to human actions alter the interactions between organisms. We studied the relationship between forest fragment size and arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) colonization, and the AMF spore communities in the rhizosphere of two congeneric Euphorbia species (native and exotic/invasive). We hypothesized that these fungal variables will differ with fragment size and species status, and predicted that (a) AMF and DSE colonization together with AMF spore abundance and diversity would be positively related to forest fragment size; (b) these relationships will differ between the exotic and the native species; and (c) there will be a negative relationship between forest fragment size and the availability of soil nutrients (NH4+, NO3−, and phosphorus). This study was performed in the eight randomly selected forest fragments (0.86–1000 ha), immersed in an agricultural matrix from the Chaquean region in central Argentina. AMF root colonization in the native and exotic species was similar, and was positively related with forest fragment size. Likewise, AMF spore diversity and spore abundance were higher in the larger fragments. While DSE root colonization in the native host was positively related with forest fragment size, DSE colonization in the exotic host showed no relationship. Soil nutrients contents were negatively related with forest fragment size. In addition, NH4+ and NO3− were negatively correlated with AMF spores abundance and root colonization and with DSE colonization in the native species. The results observed in this study show how habitat fragmentation might affect the interaction between key soil components, such as rhizospheric plant-fungal symbiosis and nutrient availability. These environmental changes may have important consequences on plant community composition and nutrient dynamics in this fragmented landscape.

Colonization of arbuscular mycorrhizal fungi and dark septate endophytes in Panax notoginseng

Arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) colonizing Panax notoginseng in three main producing areas in Wenshan Prefecture of Yunan province were investigated. The fungal colonization of 144 roots samples including healthy and rot roots of P. notoginseng with different age were observed by means of acid fuchsin stain. The results showed that P. notoginseng was the typical arbuscular mycorrhizal plant. Although there was no significant difference in AMF and DSE colonization among three sites, the total colonization of AMF was significantly higher than that of DSE. Statistical analysis demonstrated that the fresh weight of P. notoginseng root was positively significantly correlated with the colonization of AMF, but not with the colonization of DSE. These results suggest that AMF may play more important role than DSE in improving the yield and quality of P. notoginseng. Furthermore, AMF colonization of healthy P. notoginseng was higher than that of plant with root rot, which suggested that AMF could defend P. notoginseng against root rot pathogens. AMF have great potentiality and broad prospect to control root rot of P. notoginseng.

Root fungal symbionts interact with mammalian herbivory, soil nutrient availability and specific habitat conditions

Herbivory, competition and soil fertility interactively shape plant communities and exhibit an important role in modifying conditions for host-dependent fungal symbionts. However, field studies on the combined impacts of natural herbivory, competition and soil fertility on root fungal symbionts are rare. We asked how mammalian herbivory, fertilization, liming and plant-plant competition affect the root colonization of arbuscular mycorrhizal fungi (AMF) and dark septate endophytic (DSE) fungi of the dicot herb, Solidago virgaurea. The 2-year full-factorial experiment was conducted in two contrasting habitats: non-acidic and acidic mountain tundra. We found that herbivory increased arbuscular colonization (i.e. the site of resource exchange) at fertile non-acidic sites, where vegetation was rich in species having AMF symbionts, whereas at infertile acidic sites, where plants having AMF symbiont are scarce, the response was the opposite. Herbivory of the host plant negatively affected DSE hyphal and sclerotial colonization in unfertilized plots, possibly due to reduced carbon flow from the host plant while there was no effect of herbivory in fertilized plots. DSE colonization was highest in unfertilized exclosures where soil nutrient concentrations were also lowest. Liming had a negative effect on DSE hyphal colonization, and its effect also interacted with herbivory and the habitat. Biomass removal of the neighboring plants did not affect the root colonization percent of either arbuscules or DSE. Our results show that the impacts of aboveground mammalian herbivory, soil nutrient availability and specific habitat conditions on belowground root fungal symbionts are highly dependent on each other. Arbuscule response to herbivory appeared to be regulated by specific habitat conditions possibly caused by differences in the AMF availability in the soil while DSE response was associated with availability of host-derived carbon. Our result of the relationship between herbivory and soil nutrients suggests an important role of DSE in ecosystem processes.

Association of dark septate endophytes and arbuscular mycorrhizal fungi in potato under field conditions in the northeast region of India

Despite numerous studies on arbuscular mycorrhizal fungi (AMF) in potato (Solanum tuberosum L.), nothing is known about colonization by dark septate endophytes (DSE). In a study of DSE and AMF associations in a potato field at Meghalaya, northeast India, monthly DSE and AMF colonization ranged from 7.9±2.9–13.2±1.65 and 6.98±3.13–12.4±3.53%, respectively. There were no significant differences in monthly DSE and AMF colonization. AMF hyphal colonization had a significant negative correlation with pH and available phosphorus (p < 0.05). Total AMF colonization was negatively correlated with organic carbon (p < 0.05). DSE colonization showed a significant negative correlation with root hair density (p < 0.05). However, AMF colonization, although negatively correlated with root hairs, was not significant. Sixteen AMF morphotypes were identified from the genera Acaulospora, Gigaspora, Glomus, Pacispora and Scutellospora; a few remain unidentified. The results indicated that DSE and AMF colonization progressed synchronously with the dominance of Glomus tortuosum, Pacispora boliviana and Gigaspora margarita.

Erratum to: Mycorrhizal colonization and distribution of arbuscular mycorrhizal fungi associated with Michelia champaca L. under plantation system in northeast India

Arbuscular mycorrhizal fungi (AMF) and dark septate endophyte (DSE) colonization were investigated in three different plantation sites (Umdihar, Umsaw and Mawlein) of Meghalaya, northeast India. Isolation and identification of the AMF spore were conducted to evaluate the AMF diversity and host preference in terms of AMF species distribution and abundance in the plantation sites. Results showed that AMF colonization was significantly higher than dark septate endophyte colonization (p>0.05). AMF and DSE colonization had a narrow range of colonization, varying from 50.91%–58.95% and 1.84%–4.11%, respectively. Spore density varied significantly in all the sites (p>0.05). Out of 29 species identified from 7 genera, the species from Glomus was found to be highly abundant. Sorenson coefficient (Cs) ranged from 0.35–7.0. Species richness varied from 2.0–2.9 in the sites. Total species richness was significantly correlated with total relative abundance (p=0.001). The distribution, abundance and principal component analysis plot suggest that Glomus macrocarpum, G. multicaulis, G. constrictum and Acaulospora sp 1 were the most host preferred species which possibly may favour the host with proper nutrient acquisition and growth.

Arbuscular mycorrhizal fungi and dark septate endophyte colonization in bamboo from Northeast India

To address paucity of the mycorrhizal studies in bamboo, we have investigated arbuscular mycorrhizal fungal (AMF) distribution and dark septate endophyte (DSE) colonization on four species of bamboo from Northeast India. Bambusa tulda exhibits Arum type of AMF morphology, and other bamboo species have Paris type. AMF colonization was significantly higher than DSE colonization (P<0.05). Vesicular and DSE colonization exhibit a significant positive correlation with organic carbon and available phosphorus, respectively (P<0.05). Of 17 species isolated from Acaulospora, Ambispora and Glomus, 12 were isolated from Phyllostachys manii. Acaulospora tuberculata, A. rehmii, Glomus intraradices and G. tortuosum were the most frequently distributed species. Shannon diversity index was the highest in P. manii. Principal component analysis (PCA) plots and cluster analysis suggest that P. manii was the most dissimilar bamboo species in terms of mycorrhizal colonization and soil properties.

Do compensatory shoot growth and mycorrhizal symbionts act as competing above- and below-ground sinks after simulated grazing?

Since mycorrhizal symbionts are dependent on host carbon availability, shading and grazing of the host plant often decrease mycorrhizal colonization in host roots. We conducted field experiments on an intensively mycorrhizal host, Autumn gentian, Gentianella amarella to investigate the effects of neighbor removal and simulated grazing on host growth and reproduction as well as mycorrhizal colonization. In the neighbor removal experiment, we manually removed the above-ground parts of companion plants of gentians. Reduced competition tended to improve the performance of both the host and the symbionts. Total fungal as well as arbuscular, hyphal, and coiled hyphal colonizations were higher in gentians with neighbors removed. Simulated grazing (clipping off 50% of shoot height) reduced host shoot and seed biomass, whereas the responses of the root symbionts were most often positive or neutral. In the first experiment (with late-flowering plants), clipping increased arbuscular, hyphal, and total colonizations but decreased dark septate endophyte colonization. In the second experiment (with both early- and late-flowering plants), clipping did not affect total mycorrhizal colonization. Higher arbuscular, hyphal, and total colonizations were found in late-flowering gentians compared to early-flowering ones. Early-flowering plants, on the other hand, tolerated simulated grazing better compared to late-flowering plants, which may indicate a higher cost of the symbionts for the late-flowering plants. Above-ground herbivory tends to increase carbon limitation, and under these conditions, regrowing shoots and the fungal symbionts may appear as alternative, competing sinks for the host’s limited carbon reserves.

Mycorrhizal and dark septate fungal associations in gingers and spiral gingers

Associations of arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) fungi with 38 ginger species (Zingiberaceae) and two spiral gingers (Costaceae) were investigated. All species were mycorrhizal, and the status of 35 gingers and one spiral ginger has been investigated for the first time. The extent of AM colonization and the root length colonized by AM structures varied significantly among species. AM structures were also observed in non-root portions such as scale leaves. Arbuscular mycorrhizae were of either Arum-type or intermediate- type; AM-type is reported for the first time in 37 species. Spores of 16 morphotypes belonging to 4 genera ( Glomus , Acaulospora , Scutellospora , Racocetra ) were identified from the rhizosphere soil. DSE colonization was found in 22 gingers and 2 spiral gingers. Twenty-two plant species are reported as hosts of DSE fungi for the first time. The extent of total AM and DSE colonization was not correlated.

Mycorrhizal colonization and growth of Phragmites australis in an intermittent wetland

Arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungal colonization of Phragmites australis roots and its relation to plant productivity parameters was investigated in an intermittent karst wetland Lake Cerknica (Slovenia) with seasonal water level fluctuations. Mycorrhizal colonization was determined five times in 2008–from the beginning to the end of the growing season–in three reed stands with large differences in soil parameters and water level changes. AM and DSE colonization varied significantly between sampling plots and during the growing season (7% < frequency < 87%). The flooding of two of the three reed stands decreased mycorrhiza early in the growing season, but further flooding had no additional effect. Levels of DSE colonization were high in the beginning and the end of the growing season, while a peak in AM colonization was observed towards the end. The observed positive in situ correlation between mycorrhizal colonization and P. australis growth parameters does not allow final mechanistic conclusion: both P. australis and mycorrhiza could be beneficial.

Dark septate endophyte and arbuscular mycorrhizal status of vegetation colonizing a bottomland hardwood forest after a 100 year flood

Levels of arbuscular mycorrhizal (AM) colonization and dark septate endophyte (DSE) colonization were assessed in the vegetation recolonizing a remnant bottomland hardwood forest in north central Texas following a 100 year flood. Thirty seven plant species representing 21 dicotyledonous and 2 montocotyledonous families established following floodwater recession. AM and/or DSE were found in all species. AM colonization was found in 31 out of the 37 species assessed including both monocotyledonous families (Poaceae and Cyperaceae) and 17 out of 21 dicotyledonous families (Acanthaceae, Asteraceae, Boraginaceae, Cucurbitaceae, Euphorbiaceae, Lamiaceae, Loganiaceae, Lythraceae, Malvaceae, Onagraceae, Pedaliaceae, Ranunculaceae, Sapindaceae, Scrophulariaceae, Solanaceae, Verbanaceae and Violaceae). DSE were found in 31 out of 37 species assessed including both monocotyledonous families and 15 out of 21 dicotyledonous families (Amaranthaceae, Asteraceae, Boraginaceae, Brassicaceae, Cucurbitaceae, Euphorbiaceae, Lamiaceae, Lythraceae, Malvaceae, Pedaliaceae, Phytolaccaceae, Polygonaceae, Ranunculaceae, Sapindaceae, Scrophulariaceae and Violaceae). There were no detectable differences in AM or DSE colonization levels among wetland indicator groups ( p > 0.05). Levels of DSE colonization were negatively correlated with vesicular colonization and hyphal colonization for the obligate wetland species. There were no other significant relationships between AM and DSE colonization detected. Spearman rank order correlation coefficients did not differ significantly among wetland indicatory category for any level of AM or DSE colonization.

Coexistence of arbuscular mycorrhizae and dark septate endophytic fungi in an undisturbed and a disturbed site of an arid ecosystem

Effect of disturbance on root colonization and vertical distribution of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) was investigated at two adjacent sites of Lal Suhanra Biosphere Reserve, Pakistan. Disturbance clearly affected AMF and DSE colonization, vertical distribution of AMF and plant community structure. Mean colonization of AMF and DSE was slightly less at the disturbed site. Average spore densities, diversity and richness of AMF and DSE were higher at the undisturbed site. A study of the vertical distribution of AMF associated with the five plant species most common to each study site indicated that beside AMF and DSE colonization disturbance may affect AMF species composition. Correlation of AMF with DSE is also discussed.