Dark Septate Endophytes Colonization Research Articles

©Relationship between endophytic fungal diversity and colonization and soil factors of cultured blueberry roots in Guizhou Province, Southwest China.

Dark septate endophytes (DSEs) inhabit plant roots and soil in ecosystems and host plants worldwide. DSE colonization is influenced by cultivars, soil factors, and specific habitat conditions. The regular diversity of DSEs in blueberries in Guizhou, China, is still unclear. In this study, four cultivars (Gardenblue, Powderblue, O'Neal, and Legacy) in three areas (Gaopo, Majiang, and Fenggang) in Guizhou were used to identify DSEs by morphological and molecular biological methods and to clarify the relationship between DSE diversity and DSE colonization and soil factors of cultivated blueberries in Guizhou. The DSEs isolated from cultivated blueberry roots in 3 areas in Guizhou Province were different, belonging to 17 genera, and the dominant genera were Penicillium, Phialocephala, and Thozetella. DSEs isolated from Majiang belonged to 12 genera and 16 species, those from Gaopo belonged to 7 genera and 15 species, and those from Fenggang belonged to 5 genera and 7 species. Among the different blueberry varieties, 11 genera were isolated from O'Neal, 12 genera were isolated from Powderblue, 11 genera were isolated from Legacy and 13 genera were isolated from Gardenblue. Coniochaeta is endemic to O'Neal, Chaetomium and Curvularia are endemic to Powderblue, and Thielavia is endemic to Legacy. Correlation analysis showed that DSE diversity was significantly correlated with DSE colonization and soil factors.

Pervasive associations between dark septate endophytic fungi with tree root and soil microbiomes across Europe

Trees interact with a multitude of microbes through their roots and root symbionts such as mycorrhizal fungi and root endophytes. Here, we explore the role of fungal root symbionts as predictors of the soil and root-associated microbiomes of widespread broad-leaved trees across a European latitudinal gradient. Our results suggest that, alongside factors such as climate, soil, and vegetation properties, root colonization by ectomycorrhizal, arbuscular mycorrhizal, and dark septate endophytic fungi also shapes tree-associated microbiomes. Notably, the structure of root and soil microbiomes across our sites is more strongly and consistently associated with dark septate endophyte colonization than with mycorrhizal colonization and many abiotic factors. Root colonization by dark septate endophytes also has a consistent negative association with the relative abundance and diversity of nutrient cycling genes. Our study not only indicates that root-symbiotic interactions are an important factor structuring soil communities and functions in forest ecosystems, but also that the hitherto less studied dark septate endophytes are likely to be central players in these interactions.

Temporal and spatial dynamics and functional metabolism of dark septate endophytes of Gymnocarpos przewalskii Maxim. in Northwest Desert, China

In extreme habitats, plants can survive mutually with their beneficial colony partners. How dark septate endophytes (DSE) assist the relict plant Gymnocarpos przewalskii survive in extremely desert environment and maintain the stability of the ecosystem remains unclear. Studying distribution, seasonal changes and functional physiological responses of DSE colonized in roots of G. przewalskii can help understand symbiosis mechanism of these endophytes associated to relict plants in extremely arid desert environments. DSE colonization, species diversity and soil properties of G. przewalskii were measured in Anxi and Minqin sites, Northwest China in July, September and December 2019. Subsequently, the functional metabolism of DSE strain was measured, and the response of DSE strain to drought stress was performed in vitro. DSE hyphal colonization (23.3 % - 39.2 %) and DSE isolation frequency (6.0 % - 27.6 %) varied sharply among seasons and sites. Soil alkaline phosphatase, nitrate nitrogen and total phosphorus were main factors affecting the DSE composition. Twenty-six DSE isolates produced indole-3-acetic acid (IAA) in the medium, while 50 % of DSE showed a potential for IAA production in L-tryptophan-dependent. Additionally, the composition of functional metabolites of DSE strains varied greatly with different drought levels and DSE isolates, which may indirectly reflect the complementarity between different strains in helping hosts cope with drought stress. This study confirmed the temporal and spatial dynamics and growth-promoting and drought-tolerant potential of DSE community in desert environment, and provided a new perspective for exploring the survival strategy and vegetation protection of desert relict plants.

A Dark Septate Endophyte Improves Cadmium Tolerance of Maize by Modifying Root Morphology and Promoting Cadmium Binding to the Cell Wall and Phosphate.

Dark septate endophytes (DSEs) can improve the performance of host plants grown in heavy metal-polluted soils, but the mechanism is still unclear. A sand culture experiment was performed to investigate the effects of a DSE strain (Exophiala pisciphila) on maize growth, root morphology, and cadmium (Cd) uptake under Cd stress at different concentrations (0, 5, 10, and 20 mg·kg-1). The results indicated that the DSE significantly improved the Cd tolerance of maize, causing increases in biomass, plant height, and root morphology (length, tips, branch, and crossing number); enhancing the Cd retention in roots with a decrease in the transfer coefficient of Cd in maize plants; and increasing the Cd proportion in the cell wall by 16.0-25.6%. In addition, DSE significantly changed the chemical forms of Cd in maize roots, resulting in decreases in the proportions of pectates and protein-integrated Cd by 15.6-32.4%, but an increase in the proportion of insoluble phosphate Cd by 33.3-83.3%. The correlation analysis revealed a significantly positive relationship between the root morphology and the proportions of insoluble phosphate Cd and Cd in the cell wall. Therefore, the DSE improved the Cd tolerance of plants both by modifying root morphology, and by promoting Cd binding to the cell walls and forming an insoluble phosphate Cd of lower activity. These results of this study provide comprehensive evidence for the mechanisms by which DSE colonization enhances Cd tolerance in maize in root morphology with Cd subcellular distribution and chemical forms.

Yields of Buckwheat and Alfalfa in an Intercropping System Inoculated with Dark Septate Endophytes in a Coal Mining Subsidence Dryland Area

Coal mining subsidence areas in north Shaanxi province in north China are commonly low-fertility drylands, and intercropping is a popular method locally of maximizing crop yields. Inoculation with dark septate endophytes (DSE) can increase the yields of conventional crops grown in monoculture, but the effects of DSE on the growth and yield of intercropped plants are unknown. Here, a field experiment was conducted in a coal mining subsidence area on the loess plateau in 2020 and 2021. The two crops were buckwheat and alfalfa, with four treatments for each crop: sole cropping control, sole cropping with DSE inoculation, intercropping control, and intercropping with DSE inoculation. The yields, land equivalent ratios, DSE colonization rates, and yield components of buckwheat and alfalfa were compared in the different treatments. Stepwise regression and path analysis was conducted to identify the factors that determined crop yields. Yields of intercropped buckwheat and alfalfa with DSE inoculation increased in two consecutive years compared with sole cropping control, with yields increasing in 2020 by 117 and 86%, respectively. In 2021, the yield of buckwheat in intercropping with DSE inoculation did not increase significantly, but the yield of alfalfa increased by 120% compared with the sole cropping control. Buckwheat-alfalfa intercropping has the advantage of increasing the yield. DSE inoculation significantly increased the yield of buckwheat-alfalfa intercropping in 2020, but there was no yield advantage in 2021. The yield components of buckwheat and alfalfa showed inconsistent differences among experimental treatments. Stepwise regression and path analysis shows that the DSE colonization rate played an important role in the yield, which was an increased in buckwheat and alfalfa in 2020 and 2021. DSE affected the buckwheat yield indirectly by increasing the grain weight per plant, plant phosphorus uptake, and plant nitrogen content. DSE indirectly affected alfalfa yields by increasing plant nitrogen uptake and plant height. DSE may therefore have some potential to increase yields in buckwheat-alfalfa intercropping systems in coal mining subsidence areas.

Complementary Effects of Dark Septate Endophytes and Trichoderma Strains on Growth and Active Ingredient Accumulation of Astragalus mongholicus under Drought Stress.

Drought is a major abiotic stress factor affecting plant growth and production, while utilizing beneficial endophytic fungi is one of the most promising strategies for enhancing plant growth and drought tolerance. In the current study, a pot experiment was conducted to investigate the beneficial effects of dark septate endophyte (DSE) (Macrophomina pseudophaseolina, Paraphoma radicina) and Trichoderma (Trichoderma afroharzianum, Trichoderma longibrachiatum) inoculum on Astragalus mongholicus grown in sterile soil under drought stress, alone, or in combination. The addition of Trichoderma enhanced the DSE colonization in roots regardless of the water condition. Under well-watered conditions, M. pseudophaseolina inoculation significantly enhanced the biomass and root length of A. mongholicus. The two DSE and Trichoderma inoculum significantly improved calycosin-7-O-β-D-glucoside content. However, M. pseudophaseolina + T. afroharzianum inoculation better promoted root growth, whereas co-inoculation had higher active ingredient contents compared with single inoculation, except for P. radicina + T. afroharzianum. Under drought stress, DSE and Trichoderma inoculum significantly improved root biomass, root length, calycosin-7-O-β-D-glucoside content, and activities of nitrate reductase and soil urease. P. radicina + T. afroharzianum and P. radicina + T. longibrachiatum better increased root length, and all combinations of DSE and Trichoderma had a greater impact on the increase in formononetin content compared with the single treatments. Additionally, Trichoderma relies on antioxidant enzymes, growth hormones, and the redox system (ascorbic acid–glutathione) to resist drought, while DSE strains have an additional osmotic regulation system in addition to the drought resistance function possessed by Trichoderma, and the effect of co-inoculation (especially M. pseudophaseolina + T. longibrachiatum and P. radicina + T. afroharzianum) on plant physiological parameters was greater than that of single inoculation. This study provides a new research direction for the effects of DSE and Trichoderma on medicinal plant cultivated in dryland.

Epichloë endophyte affects the root colonization pattern of belowground symbionts in a wild grass

Plants host multiple symbionts that interact with each other affecting plant performance and regulating their establishment. Here, we analyzed how the association with Epichloë endophytes affects belowground colonization by Dark Septate Endophytes (DSE) and arbuscular mycorrhizal fungi (AMF) in the grass Bromus auleticus . Epichloë -symbiotic (E+) and Epichloë -non symbiotic (E−) plants were sampled from a long-term experimental plot and colonization structures were analyzed in the roots. We also examined the influence of Epichloë exudates on the in vitro growth of DSE Microdochium bolleyi isolated from roots. Epichloë symbiosis increased AMF colonization, although differences were not significant. Despite the lack of differences in total DSE colonization, in concordance with in vitro findings, a higher significant abundance of microsclerotia was observed in E+ plants. A negative correlation between total mycorrhizal and DSE was found. Our findings show a more uniform root colonization pattern in E+ plants, suggesting a root symbiosis modulating role. • DSE microsclerotia was significantly more abundant in B . auleticus E+ plants than E−. • Arbuscules abundance was double in plants associated with Epichloë compared to E−. • Epichloë endophytes exudates did not affect DSE strain growth in vitro . • DSE negatively correlate with AMF colonization. • E+ plants presents a more uniform root colonization pattern than Eplichloë -free.

Relationship of root dark septate endophytes and soil factors to plant species and seasonal variation in extremely arid desert in Northwest China

Investigations on host affiliations, seasonal variation and physiological response to drought tolerance of dark septate endophytes (DSE) in extremely arid desert environments can help explain the adaptive mechanisms of these endophytes in desert ecosystems. The colonization and species diversity of DSE and the soil factors in the rhizospheres of five desert shrubs were therefore determined in Anxi extremely arid environment in Northwest China in July, September and December 2020. Subsequently, six DSE strains were selected to test the growth and metabolic response of DSE strains to drought stress in vitro. The sampled plants and seasons significantly influenced the morphology, colonization and species diversity of DSE. Of the 15 DSE species isolated in the roots of these plants, Triangularia allahabadensis was reported in desert ecosystems for the first time. DSE colonization was predominately affected by season and soil factors, while species composition was more corresponded to plant species. The composition of metabolites of DSE strains varied significantly due to levels of drought stress and DSE identity, which indirectly reflected the difference of their traits to respond to drought stress. This study confirmed the establishment of relationship between DSE and roots of xerophytic plants, and proved the drought tolerance of DSE in vitro, providing insight into the application of DSE to assist desert plants to resist drought.

Effects of the Dark Septate Endophyte (DSE) Exophiala pisciphila on the Growth of Root Cell Wall Polysaccharides and the Cadmium Content of Zea mays L. under Cadmium Stress.

This paper aims to investigate the mechanism by which dark septate endophytes (DSEs) enhance cadmium (Cd) tolerance in there host plants. Maize (Zea mays L.) was inoculated with a DSE, Exophiala pisciphila, under Cd stress at different concentrations (0, 5, 10, and 20 mg·kg−1). The results show that, under 20 mg/kg Cd stress, DSE significantly increased maize biomass and plant height, indicating that DSE colonization can be utilized to increase the Cd tolerance of host plants. More Cd was retained in DSE-inoculated roots, especially that fixed in the root cell wall (RCW). The capability of DSE to induce a higher Cd holding capacity in the RCW is caused by modulation of the total sugar and uronic acid of DSE-colonized RCW, mainly the pectin and hemicellulose fractions. The fourier-transform spectroscopy analysis results show that carboxyl, hydroxyl, and acidic groups are involved in Cd retention in the DSE-inoculated RCW. The promotion of the growth of maize and improvement in its tolerance to Cd due to DSEs are related to restriction of the translocation of Cd from roots to shoots; resistance of Cd uptake Cd inside cells; and the increase in RCW-integrated Cd through modulating RCW polysaccharide components.

Lotus tenuis and Schedonorus arundinaceus co-culture exposed to defoliation and water stress

The present study aimed to investigate the effect of defoliation frequency (low and high) and water stress (excess or deficit) on biomass production, P and N nutrition, and symbiosis with native soil microorganisms on a Lotus tenuis and Schedonorus arundinaceus co-culture in a pot experiment. Combined effects of defoliation frequency and water stress affected plant accumulated shoot biomass. L. tenuis root biomass decreased in response to defoliation and water stress, while S. arundinaceus root biomass was similar between non-defoliated and defoliated plants, at all water levels. Low and high frequencies of defoliation in a waterlogged soil can be considered the most stressful scenario for L. tenuis and S. arundinaceus co-culture. Colonization of arbuscular mycorrhizal fungi in L. tenuis roots and dark septate endophytes colonization in S. arundinaceus roots were affected by both factors, whereas arbuscular mycorrhizal colonization in S. arundinaceus was affected only by water stress. Both plants tolerated defoliation and water stress due to the interaction between the translocation of nutrients and carbon compounds from roots to shoots, and P and N absorption (plus N2 fixation in L. tenuis). Highlights: Both plants tolerated defoliation and water stress due to the interaction between the translocation of nutrients and carbon compounds from roots to shoots, and P and N absorption (plus N2 fixation in tenuis). Low and high frequencies of defoliation in a waterlogged soil can be considered the most stressful scenario for tenuis and S. arundinaceus co-culture. Defoliation frequency increased AM colonization in plant roots under well watered and water deficit conditions. arundinaceus roots were co-colonized by AM fungi and DSE. Promoting the presence of tenuis through low defoliation frequency would improve forage yield and quality with the maintenance of AM symbiosis in legume–grass communities.

Are lulworthioid fungi dark septate endophytes of the dominant Mediterranean seagrass Posidonia oceanica?

A previous study from Sicily, Italy, indicated that the dominant Mediterranean seagrass Posidonia oceanica forms a dark septate endophytic (DSE) association with a lulworthioid fungus ('Lulwoana sp.'). This conflicts with several other studies from the NW Mediterranean Sea that point at the recently described pleosporalean fungus Posidoniomyces atricolor. I collected P. oceanica roots at eight sites around Sicily and checked them for fungal colonization using light microscopy. At three sites, root fungal symbionts (mycobionts) were isolated into pure cultures and identified using ITS rDNA sequences. Posidoniomyces atricolor represented the most frequent mycobiont (56 isolates), closely followed by lulworthioid fungi (51). The obtained mycobiont spectrum also included Cladosporium (2), Alternaria (1), Corollospora (1), Fusarium (1), Penicillium (1) and Vishniacozyma (1) isolates. The characteristic DSE root colonization, similar to those occurring in terrestrial plants but not known from any other seagrass, was found in all investigated P. oceanica individuals. The microscopy screening suggests that P. atricolor is responsible for the observed DSE colonization. This study extends the known range of Pos. atricolor and the DSE association characteristic for P. oceanica to the southern Tyrrhenian Sea/Sicily. While lulworthioid fungi regularly occur in P. oceanica tissues, including terminal fine roots, their significance and functioning (e.g. parasitic, pathogenic, endophytic) are unknown and require further investigation. However, there is currently no proof that they belong among dark septate endophytes of this seagrass.

Arbuscular mycorrhizal and dark septate endophyte colonization in Artemisia roots responds differently to environmental gradients in eastern and central China

Arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) are two types of root symbiotic fungi that enhance nutrient uptake by host plants and their resistance to biotic and abiotic stresses. However, it remains unclear whether AMF and DSE are synergistic or antagonistic in the presence of host plants to environmental gradients, especially on large geographical scales. To determine the relationships between AMF and DSE and their adaptability on a regional scale, we measured AMF and DSE colonization in the roots of 1023 plants of different species within the Artemisia genus collected from 81 sites across central and eastern China. We used general linear mixed models to analyze the relationships between colonization, and temperature and precipitation conditions. We found no significant correlation between AMF and DSE. The AMF colonization rate followed a significant longitudinal trend, but there was no latitudinal pattern. DSE colonization did not follow any geographical pattern. The AMF colonization rate was positively correlated with temperature and precipitation, whereas it was not significantly correlated with soil. There was no significant correlation between DSE colonization and climate or soil. Our results suggest that AMF and DSE play independent roles in the response of Artemisia to the regional environment. Therefore, studies on mycorrhizal symbiosis should discern the differential responses between AMF and DSE to climate and soil when evaluating the adaptability of the two types of symbiosis on large geographical scales.

Temporal and Spatial Dynamics of Dark Septate Endophytes in the Roots of Lycium ruthenicum in the Desert Region of Northwest China

With the intensification of desertification in northwest China, drought has become a serious environmental problem restricting plant growth and ecological restoration. Recently, dark septate endophytes (DSEs) have attracted more attention because of their ability to improve plants’ resistance to drought. Here, we investigated DSE colonization and species diversity in roots of Lycium ruthenicum collected from Anxi and Minqin, in northwest China, during July, September, and December 2019. This study aimed to evaluate the influence of seasonality and sampling sites on DSEs. In different seasons, DSE colonization varied with the phenology of L. ruthenicum. At different sites, DSE colonization significantly differed. Four isolates were reported in desert ecosystems for the first time. The results showed microsclerotial colonization was directly affected by changing seasons, while hyphal colonization and species diversity were directly affected by sampling sites. The soil organic carbon, pH, alkaline phosphatase, and alkali-hydrolyzable nitrogen were the main predictors of DSE colonization and species diversity. We conclude that DSE colonization and diversity showed significant spatial–temporal heterogeneity and were closely related to soil factors. This research provides a basis for the further understanding of the ecological functions of DSEs and their application potential for vegetative restoration and agricultural cultivation in drylands.

Idiosyncratic responses to simulated herbivory by root fungal symbionts in a subarctic meadow

ABSTRACT Plant-associated fungi have elementary roles in ecosystem productivity. There is little information on the interactions between arbuscular mycorrhizal (AM) fungal symbiosis, fine endophytic (FE) and dark septate endophytic (DSE) fungi, and their host plants in cold climate systems. In particular, the environmental filters potentially driving the relative abundance of these root symbionts remain unknown. We investigated the interlinkage of plant and belowground fungal responses to simulated herbivory (clipping, fertilization, and trampling) in a subarctic meadow system. AM and FE frequency in the two target plant roots, Potentilla crantzii and Saussurea alpina, was unaffected by simulated herbivory, highlighting the importance and resilience of arbuscule forming mycorrhizas in a range of environmental conditions. Fertilization and trampling increased DSE colonization in P. crantzii roots although generally P. crantzii performance was reduced in these plots. The idiosyncratic responses by DSE fungal frequency in the two host plants in our experiment indicate that the host plant identity has a pivotal role in the DSE fungus–plant outcome. DSE fungal frequency did not respond to environmental manipulations in a manner similar to arbuscular mycorrhizas, suggesting that they have a different role in plant ecology.

Colonization by dark septate endophytes improves the growth of Hedysarum scoparium under multiple inoculum levels

Despite the abundance of studies on the interactions between dark septate endophytes (DSEs) and host plants, little is known about the effects elicited by different DSE species and inoculum levels, especially in desert plants. Here, we examined the colonization status and species composition of DSEs in roots of Hedysarum scoparium, a xerophyte plant endemic to arid desert, northwest China. Subsequently, we assessed the performance of host plants inoculated with Paraphoma chlamydocopiosa and Alternaria doliconidium under different inoculum levels. DSE colonization was characterized by spatial and interannual variability, and hyphal colonization was dominant (17.2%–76.7%). Alternaria doliconidium, Edenia gomezpompae, Paraphoma pye, Subramaniula flavipila and Herpotrichia striatispora are reported here in desert ecosystems for the first time. Both P. chlamydocopiosa and A. doliconidium established positive symbiosis with H. scoparium, however, the growth-promoting effects differed significantly depending on the DSE species and inoculum level (P < 0.05). Specifically, P. chlamydocopiosa promoted plant height and shoot biomass, whereas A. doliconidium enhanced stem branching and total biomass. The greatest benefits associated with DSEs occurred at 20-mL inoculum level. Variance partitioning analysis indicated inoculum level explained 13.7% of variation in plant growth, while substrate properties and enzymatic activity explained respectively 38.0% and 12.2% of variation in DSE–host associations. Total root length and root surface area were significantly correlated with substrate pH and phosphorus, whereas root diameter was affected by organic carbon and phosphatase. These data provide basis for evaluating the potential application of DSEs for vegetation restoration in arid ecosystems.

Influence of soil microbiota on Taxodium distichum seedling performance during extreme flooding events

Plant associations with soil microbiota can modulate tree seedling growth and survival via mutualistic or antagonistic interactions. It is uncertain, however, whether soil microbiota influence seedling growth of coastal trees when exposed to extreme flooding regimes. We evaluated the role of soil microbes in promoting baldcypress (Taxodium distichum) seedling performance under different inundation scenarios and determined the influence of flooding on the colonization of in planta beneficial microbes. Seedlings reared in sterile and non-sterile soil were exposed to three different flooding regimes historically experienced in Louisiana swamps. Seedling growth was assessed, and the colonization by beneficial symbionts such as arbuscular mycorrizhal fungi (AMF), and dark septate endophytes (DSE) was evaluated in harvested roots. Seedlings grown in sterile soil had six times higher growth than seedlings reared in non-sterile soil. As a result, we evaluated pathogen load in the roots by assessing oomycete colonization. Flooding influenced the in planta colonization of DSE and oomycetes, but did not affect the colonization of mutualist AMF fungi. DSE and oomycetes were rarer in flooded conditions, while AMF remained abundant. Seedling biomass production was not correlated with in planta fungal colonization or pathogen load. Soil microbiota can negatively influence baldcypress seedling growth, and no growth benefit was evidenced from the root colonization of mutualist fungi. Flooding can modify baldcypress-fungal interactions by diminishing colonization of DSE. Overall, baldycpress seedlings were more sensitive to the presence of microbiota than flooding, and thus restoration efforts should focus on having a better understanding of plant–microbe interactions in swamps.

Dark septate endophyte improves salt tolerance of native and invasive lineages of Phragmites australis

Fungal endophytes can improve plant tolerance to abiotic stress. However, the role of these plant–fungal interactions in invasive species ecology and their management implications remain unclear. This study characterized the fungal endophyte communities of native and invasive lineages of Phragmites australis and assessed the role of dark septate endophytes (DSE) in salt tolerance of this species. We used Illumina sequencing to characterize root fungal endophytes of contiguous stands of native and invasive P. australis along a salinity gradient. DSE colonization was assessed throughout the growing season in the field, and effects of fungal inoculation on salinity tolerance were investigated using laboratory and greenhouse studies. Native and invasive lineages had distinct fungal endophyte communities that shifted across the salinity gradient. DSE colonization was greater in the invasive lineage and increased with salinity. Laboratory studies showed that DSE inoculation increased P. australis seedling survival under salt stress; and a greenhouse assay revealed that the invasive lineage had higher aboveground biomass under mesohaline conditions when inoculated with a DSE. We observed that P. australis can establish mutualistic associations with DSE when subjected to salt stress. This type of plant–fungal association merits further investigation in integrated management strategies of invasive species and restoration of native Phragmites.

Freeze tolerance of poleward‐spreading mangrove species weakened by soil properties of resident salt marsh competitor

Abstract Increasing temperatures associated with climate change are shifting plant species to higher latitudes. Soil communities could aid the plants’ shift into novel areas by harbouring fewer soil‐borne antagonists or more mutualists that influence the fitness and stress tolerance of the shifting species. Alternatively, they could contain novel antagonists or fewer mutualists. Thus, soil communities could positively or negatively affect plant range expansion, particularly if they influence plants’ responses to climate, such as freeze tolerance, that feedback to affect expansion. We used the northward range expansion of the black mangrove, Avicennia germinans, into a system dominated by marsh cordgrass, Spartina alterniflora, in northern Florida, USA to study how the novel soil environment (i.e. S. alterniflora soil) affects mangrove fitness, susceptibility to cold stress and the colonization of mutualist fungi. We quantified abundance of root mutualistic fungi in mixed marsh‐mangrove habitat and conducted a laboratory experiment to test effects of steam‐sterilized and live soils from A. germinans and S. alterniflora on the growth, condition, fungal colonization and freeze tolerance of A. germinans seedlings. In the field, we found two times higher dark septate endophyte (DSE) colonization of A. germinans roots and three times higher fungal spore density in A. germinans soil compared to S. alterniflora roots and soil. In the laboratory experiment, seedlings in steamed S. alterniflora soil treatments had 50%–65% survival after freezing, compared to 0% survival in treatments with live S. alterniflora soil. A. germinans live soil mixed with S. alterniflora steamed soil yielded A. germinans roots with the highest DSE colonization and seedlings with greater shoot biomass and lower root:shoot ratios. S. alterniflora live soil lowered the freeze tolerance of A. germinans, decreased mangrove survival and depressed DSE colonization. Synthesis. S. alterniflora soil could impede A. germinans establishment in salt marsh communities. As climate warming gradually allows A. germinans to displace S. alterniflora, the rhizosphere could become increasingly hospitable to A. germinans. Our work suggests the soil community associated with resident species mediates climatic stressors to affect expansion success.

Endophytes associated with Himalayan silver birch (Betula utilis D. Don) roots in relation to season and soil parameters

Biological processes in soil are driven and mediated by root and soil microbiome (microbial communities) and are sensitive to many environmental variations. Soil microbial communities compete for nutrient and space and form mutualistic associations with host plants. Rhizosphere, the connecting site of plant roots with soil, influences the soil health and plant-microbe interactions. Soil enzyme activity, which is considered to be the biological indicator of soil health, is significantly influenced by microbial functioning. Betula utilis D. Don is a dominant treeline forming species that has been extensively studied for the impact of climate-mediated variations in sub-alpine Himalayan region. However, the microbial ecology of this species remains almost unexplored. Therefore, the present study aims to assess the endophytic communities associated with B. utilis roots along with the status of enzymes, nutrients, and microbial communities in rhizosphere soil in two seasons from three sites in North-Western Himalaya. Activity of soil enzymes (acid and alkaline phosphatase, aryl sulfatase, β-glucosidase, urease and dehydrogenase) varied statistically with respect to seasons. Except dehydrogenase, the soil enzymes activity correlated with pH, organic carbon, and phosphorus content in soil. High dehydrogenase activity is attributed to high microbial activity in dormant season. B. utilis roots were found to be colonized with a range of microbial communities namely, mycorrhizae, dark septate endophytes (DSE), bacterial endophytes and unidentified nematode like structures (NLS). While, in general, DSE colonization was higher during growing season, mycorrhizae dominated the roots during dormant season. Significant differences were obtained only in mycorrhizal colonization with respect to seasons and sites. Further, significant correlations were obtained among soil nutrients, enzyme activity, and microbial counts during growing season. B. utilis roots exerted negative rhizosphere effect on microbial communities. The study will have implications in understanding plant-microbe interactions under sub-alpine Himalayan region.

Selection of arbuscular mycorrhizal fungi for sugarcane in four soils with the presence of dark septate endophytes

The present study aimed to select efficient arbuscular mycorrhizal fungi (AMF) for sugarcane growth and P nutrition in four soils that spontaneously contained dark septate endophytes (DSE). The effect of nine AMF isolates was evaluated individually in sugarcane presprouted seedlings (SP81-3250) grown under greenhouse conditions for a 120-day period. The isolates that stimulated plant growth in the soils with low P availability were Acaulospora colombiana (ACOL), Claroideoglomus etunicatum (CETU), Gigaspora margarita (GMAR), Rhizophagus clarus (RCLA) and Scutellospora calospora (SCAL). Compared to the Yellow Argisol, which had the highest P level, the Red-Yellow Argisol, with an intermediate P content, increased plant height. Compared to the other treatments, inoculation with ACOL, RCLA, and SCAL resulted in higher foliar P content in plants grown in soils with high to intermediate P levels. Root colonization by AMF and DSE was verified in the plants, with the coexistence of both fungal groups in the same plant and/or root fragment. However, AMF colonization was low compared to DSE colonization. The cooccurrence of DSE and AMF was higher in the plants inoculated with ACOL, RCLA, SCAL, and Dentiscutata heterogama. ACOL, CETU, GMAR, RCLA, and SCAL are AMF isolates that have the potential to establish a mycorrhizal inoculant for sugarcane that would be effective in several soils.