Presence Of Fungal Endophytes Research Articles

Stress tolerance activity and diversification of endophytic fungi from the medicinal plant Abutilon indicum

This study aimed to assess the diversity of endophytic fungi isolated from Abutilon indicum using morphological and molecular techniques. The isolates were exposed to various levels of salinity, temperatures, and heavy metals, including Ag2+ and Zn2+, at concentrations of 3.6 and 11.5 mM. Thirty root segments were isolated from each plant and cultured on potato dextrose agar plates. Four endophytic fungi were randomly isolated from infected root segments, belonging to the genera Aspergillus, Meyerozyma, and Penicillium. The phylogenetic analysis revealed significant diversity among the isolates of Aspergillus welwitschiae, Aspergillus indologenus, Meyerozyma carpophila, and Penicillium citrinum, with a 99% similarity in their sequences. Most isolates were able to thrive under salt stress conditions at NaCl concentrations of 200 mM (26%), 400 mM (24%), 600 mM (21%), 800 mM (13%), and 1000 mM (16%). Tolerant to temperature, endophytes could survive in the range of 25 °C to 35 °C but could not survive above 50 °C. Heavy metals tolerance of 89% of these isolates led to a significant decrease in biomass production when exposed to Ag2+. Endophytic fungal isolates showed decreased sensitivity to Zn2+, but between 33% and 60% showed strong growth in conditions with high levels of Zn2+. These findings revealed that endophytic fungi of A. welwitschiae enhanced growth when exposed to various stress conditions. Our findings indicate that the presence of fungal endophytes in different stress conditions leads to significant growth, and this could be useful for phytoremediation purposes.

Interactions between Epichloë endophyte and the plant microbiome impact nitrogen responses in host Achnatherum inebrians plants.

The clavicipitaceous fungus Epichloë gansuensis forms symbiotic associations with drunken horse grass (Achnatherum inebrians), providing biotic and abiotic stress protection to its host. However, it is unclear how E. gansuensis affects the assembly of host plant-associated bacterial communities after ammonium nitrogen (NH4+-N) treatment. We examined the shoot- and root-associated bacterial microbiota and root metabolites of A. inebrians when infected (I) or uninfected (F) with E. gansuensis endophyte. The results showed more pronounced NH4+-N-induced microbial and metabolic changes in the endophyte-infected plants compared to the endophyte-free plants. E. gansuensis significantly altered bacterial community composition and β-diversity in shoots and roots and increased bacterial α-diversity under NH4+-N treatment. The relative abundance of 117 and 157 root metabolites significantly changed with E. gansuensis infection under water and NH4+-N treatment compared to endophyte-free plants. Root bacterial community composition was significantly related to the abundance of the top 30 metabolites [variable importance in the projection (VIP) > 2 and VIP > 3] contributing to differences between I and F plants, especially alkaloids. The correlation network between root microbiome and metabolites was complex. Microorganisms in the Proteobacteria and Firmicutes phyla were significantly associated with the R00693 metabolic reaction of cysteine and methionine metabolism. Co-metabolism network analysis revealed common metabolites between host plants and microorganisms.IMPORTANCEOur results suggest that the effect of endophyte infection is sensitive to nitrogen availability. Endophyte symbiosis altered the composition of shoot and root bacterial communities, increasing bacterial diversity. There was also a change in the class and relative abundance of metabolites. We found a complex co-occurrence network between root microorganisms and metabolites, with some metabolites shared between the host plant and its microbiome. The precise ecological function of the metabolites produced in response to endophyte infection remains unknown. However, some of these compounds may facilitate plant-microbe symbiosis by increasing the uptake of beneficial soil bacteria into plant tissues. Overall, these findings advance our understanding of the interactions between the microbiome, metabolome, and endophyte symbiosis in grasses. The results provide critical insight into the mechanisms by which the plant microbiome responds to nutrient stress in the presence of fungal endophytes.

Seasonal diversity & spaciotemporal distribution of fungal endophytes associated with the medicinal plant Coleus forskohlii Briq.

Fungi that colonize the healthy tissues of the plants without showing any disease symptoms in the host plants are termed as fungal endophytes. The presence of fungal endophytes provides a positive effect on the host’s growth & development and also triggers the production of some essential bioactive compounds in the host. This study was undertaken to isolate, identify and understand the spaciotemporal distribution and seasonal diversity of fungal endophytes associated with the leaf, stem & root of Coleus forskohlii, an important and endangered medicinal plant. Sampling was done for a period of 12 months between May 2020–April 2021. A total of 950 fungal endophytes were isolated from a total of 1680 tissues of the leaf, stem & root of C. forskohlii. The fungi were identified based on their morphological features and some of them were identified by molecular identification by 18S rRNA sequencing. The endophytic isolates belonged to 10 different orders belonging to 3 different classes-Sordariomycetes (Hypocreales, Xylariales, Microascales, Trichosphaeriales, Glomerellales & Sordariales), Dothiomycetes (Pleosporales, Capnodiales, Botryosphaeriales) & Eurotiomyctes (Eurotiales). About 81.26% of the isolates belonged to Ascomycota & 2.63% of the isolates belonged to Mucoromycota. Chaetomium globosum, Collariella bostrychodes, C. robusta, Colletotrichum gloeosporioides, Fusarium chlamydosporum, Sterile hyaline mycelia, Aspergillus niger, Xylaria curta, X. grammica, Mucor circinelloides & Trichoderma harizianum were the frequently isolated species of fungi. C. globosum, C. bostrychodes, C. gloeosporioides, sterile hyaline mycelia & X. curta were found distributed in all the tissues of the plant. C. forskohlii has thus revealed a rich diversity of fungal endophytes that could be isolated & cultured to yield some pharmacologically important bioactive compounds.

Hardening Blueberry Plants to Face Drought and Cold Events by the Application of Fungal Endophytes

Harsh environmental conditions derived from current climate change trends are among the main challenges for agricultural production worldwide. In the Mediterranean climatic region of central Chile, sudden occurrence of spring cold temperatures in combination with water shortage for irrigation (drought) constitutes a major limitation to highbush blueberry (Vaccinium corymbosum) plantations, as flowering and fruiting stages are highly sensitive. Hardening crops may be achievable by boosting beneficial interactions of plants with microorganisms. Inoculation with symbiotic fungi isolated from plants adapted to extreme environments could be a good strategy, if they are able to maintain functional roles with non-original hosts. Here, we evaluated the effect of two Antarctic fungal endophytes (AFE), Penicillium rubens and P. bialowienzense, on the tolerance of V. corymbosum plants to cold events in combination with drought under controlled conditions. Inoculated and uninoculated plants were exposed for a month to one event of a cold temperature (2 °C/8 h) per week with or without drought and were evaluated in physiological, biochemical, and molecular variables. A complementary set of plants was kept under the same environmental conditions for two additional months to evaluate survival as well as fruit weight and size. There was an overall positive effect of AFE on plant performance in both environmental conditions. Endophyte-inoculated plants exhibited higher gene expression of the Late Embryogenesis Abundant protein (LEA1), higher photochemical efficiency (Fv/Fm), and low oxidative stress (TBARS) than uninoculated counterparts. On the other hand, plant survival was positively affected by the presence of fungal endophytes. Similarly, fruit diameter and fruit fresh weight were improved by fungal inoculation, being this difference higher under well-watered condition. Inoculating plants with fungal endophytes isolated from extreme environments represents a promising alternative for hardening crops. This is especially relevant nowadays since agriculture is confronting great environmental uncertainties and difficulties which could became worse in the near future due to climate change.

Sipha maydis sensitivity to defences of Lolium multiflorum and its endophytic fungus Epichloë occultans.

BackgroundPlants possess a sophisticated immune system to defend from herbivores. These defence responses are regulated by plant hormones including salicylic acid (SA) and jasmonic acid (JA). Sometimes, plant defences can be complemented by the presence of symbiotic microorganisms. A remarkable example of this are grasses establishing symbiotic associations with Epichloë fungal endophytes. We studied the level of resistance provided by the grass’ defence hormones, and that provided by Epichloë fungal endophytes, against an introduced herbivore aphid. These fungi protect their hosts against herbivores by producing bioactive alkaloids. We hypothesized that either the presence of fungal endophytes or the induction of the plant salicylic acid (SA) defence pathway would enhance the level of resistance of the grass to the aphid.MethodsLolium multiflorum plants, with and without the fungal endophyte Epichloë occultans, were subjected to an exogenous application of SA followed by a challenge with the aphid, Sipha maydis.ResultsOur results indicate that neither the presence of E. occultans nor the induction of the plant’s SA pathway regulate S. maydis populations. However, endophyte-symbiotic plants may have been more tolerant to the aphid feeding because these plants produced more aboveground biomass. We suggest that this insect insensitivity could be explained by a combination between the ineffectiveness of the specific alkaloids produced by E. occultans in controlling S. maydis aphids and the capacity of this herbivore to deal with hormone-dependent defences of L. multiflorum.

Hormonal and physiological changes driven by fungal endophytes increase Antarctic plant performance under UV-B radiation

Abstract Antarctic environments are amongst the most stressful habitats for life on Earth, with high intensities of solar UV-B radiation reaching the land surface. In this study, we evaluated how the photochemical efficiency, cell damage and reproductive biomass of Antarctic pearlwort (Colobanthus quitensis) were affected by different intensities of UV-B radiation in the absence and presence of fungal endophytes. In addition, we evaluated the hormonal content of plants at different UV-B radiation intensities and how hormonal content was affected by endophytes. Overall, plants exposed to UV-B radiation showed higher numbers of flowers, higher total biomass and lower lipid peroxidation in the presence of endophytes compared with plants without endophytes. Photochemical efficiency was unaffected. Fungal endophytes affected the content of salicylic acid, jasmonate, indole-3-acetate and abscisic acid in shoot tissue of plants exposed to UV-B radiation. These results suggest that endophytes could modulate the hormonal content of C. quitensis to improve its ecophysiological performance under high UV-B radiation.

Metabolism or behavior: explaining the performance of aphids on alkaloid-producing fungal endophytes in annual ryegrass (Lolium multiflorum).

Plant-herbivore interactions are often mediated by plant microorganisms, and the "defensive mutualism" of epichloid fungal endophytes of grasses is an example. These endophytes synthesize bioactive alkaloids that generally have detrimental effects on the performance of insect herbivores, but the underlying mechanisms are not well understood. Our objective was to determine whether changes in the physiology and/or behavior of aphids explain the changes in performance of insects feeding on endophytic plants. We studied the interaction between the aphid Rhopalosiphum padi and the annual ryegrass Lolium multiflorum symbiotic (E+) or not symbiotic (E-) with the fungus Epichloë occultans that can synthesize loline alkaloids. We hypothesized that aphids feeding on E+ plants have higher energetic demands for detoxification of fungal alkaloids, thereby negatively impacting the individual performance, population growth, and structure. Aphids growing on E+ plants had lower values in morphometric and functional variables of individual performance, displayed lower birth rate, smaller population size, and dramatic structural changes. However, aphids exhibited lower values of standard metabolic rate (SMR) on E+ plants, which suggests no high costs of detoxification. Behavioral variables during the first 8h of feeding showed that aphids did not change the phloem sap ingestion with the presence of fungal endophytes. We hypothesize that aphids may maintain phloem sap ingestion according to their fungal alkaloid tolerance capacity. In other words, when alkaloid concentrations overcome tolerance threshold, ingestion of phloem should decrease, which may explain the observed lower values of SMR in E+ feeding aphids.

Effect of fungal endophytes on morphological characteristics, nutrients content and longevity of plane trees (Platanus orientalis L.)

ABSTRACTThe plane tree is one of the most frequently used street trees in urban landscape in Iran and some Mediterranean countries and some age-old ones are found in these countries. Endophytes are microorganisms which associate with healthy plant tissues, persisting without causing diseases symptoms in the host and normally benefitting them through improving plant ability to withstand environmental stresses. In this contribution, the hypothesis of fungal endophytes existence in the plane trees as well as their relationship with morphological characteristics of trees and nutrient elements of leaves were studied in the central part of Iran. The experiment was performed according to an unbalanced completely randomized design. Approximate age and height of plane trees were recorded and then the greenness and visual appearance were evaluated. Healthy shoots and bark pieces were collected and surface sterilized then placed in petri dishes containing PDA. The results showed that endophytes frequency were significantly greater in age-old trees (60.04%) than young ones (39.96%). Endophytes existence had a positive correlation with iron (Fe) and potassium (K) concentrations of the leaves, and trees height and circumference. Also, there was a positive correlation between the presence of fungal endophytes and improved visual appearance of plane trees. The results suggest that fungal endophytes association enhanced nutrient elements assimilation in trees contributing at least partly to elevated survival of age-old plane trees.

Root-endophytes improve the ecophysiological performance and production of an agricultural species under drought condition.

Throughout many regions of the world, climate change has limited the availability of water for irrigating crops. Indeed, current models of climate change predict that arid and semi-arid zones will be places where precipitation will drastically decrease. In this context, plant root-associated fungi appear as a new strategy to improve ecophysiological performance and yield of crops under abiotic stress. Thus, use of fungal endophytes from ecosystems currently subjected to severe drought conditions could improve the ecophysiological performance and quantum yield of crops exposed to drought. In this study, we evaluated how the inoculation of fungal endophytes isolated from Antarctic plants can improve the net photosynthesis, water use efficiency and production of fresh biomass in a lettuce cultivar, grown under different water availability regimes. In addition, we assessed if the presence of biochemical mechanisms and gene expression related with environmental tolerance are improved in presence of fungal endophytes. Overall, those individuals with presence of endophytes showed higher net photosynthesis and maintained higher water use efficiency in drought conditions, which was correlated with greater fresh and dry biomass production as well as greater root system development. In addition, presence of fungal endophytes was correlated with a higher proline concentration, lower peroxidation of lipids and up-/down-regulation of ion homeostasis. Our results suggest that presence of fungal endophytes could minimize the negative effect of drought by improving drought tolerance through biochemical mechanisms and improving nutritional status. Thus, root-endophytes might be a successful biotechnological tool to maintain high levels of ecophysiological performance and productivity in zones under drought.

Endophytic fungi increase the processing rate of leaves by leaf‐cutting ants (Atta)

1. Fungal endophytes are microfungi that reside asymptomatically inside of leaf tissues, increasing in density and diversity through time after leaves flush. Previous studies have suggested that the presence of fungal endophytes in the harvest material of leaf‐cutting ants (Atta colombica, Guérin‐Méneville) may negatively affect the ants and their fungal cultivar.2. In the present study, it was tested whether the presence and diversity of fungal endophytes affected the amount of time necessary for leaf‐cutter ants to cut, process, and plant leaf material in their fungal garden. It was found that ants took 30–43% longer to cut, carry, clean, and plant leaf tissue with high relative to low endophyte abundance, and that the ants responded similarly to leaf tissue with high or low endophyte diversity.3. It was further investigated whether the fungal cultivars' colonisation rate was greater on leaf material without fungal endophytes. No difference in the ants' cultivar colonisation rate on leaf tissue with high or low endophyte abundance was observed.

Fungal endophytes of five medicinal plants prevalent in the traditionally preserved ‘Sacred forests’ of Meghalaya, India

Plants growing in unique habitats and having ethno-medicinal usage among the local ethnic populations of an area are often likely to harbour in them novel endophytic fungi. In the present study five ethno-medicinal plants of the traditionally preserved ‘Sacred forests’ of Meghalaya, India were studied for the presence of fungal endophytes in their roots and stems. Isolation in water agar as per standard procedures and subsequent pure culturing of the fungi in potato dextrose agar medium revealed the presence of a variety of endophytic fungal species. A total of 703 fungal isolates were obtained and classified into 16 taxonomic groups based upon their morphological characteristics. The highest diversity of endophytic fungal taxa was observed for Camellia caduca followed by Schima khasiana, Osbeckia chinensis, Potentilla fulgens and Osbeckia stellata.

Anti-Insect Secondary Metabolites from Fungal Endophytes of Conifer Trees

Choristoneura fumiferana is the most economically-important insect pest in eastern North America. Historically, strategies to control epidemics have relied on chemical pesticides that are no longer approved for use. The presence of fungal endophytes in cool area grass species and their role in reducing the impact of herbivorous insects is well understood. Recent work has demonstrated that foliar endophytes of conifers also produce anti-insect toxins. Field and nursery studies testing trees infected with the rugulosin producing endophyte Phialocephala scopiformis reduced the growth and development of C. fumiferana. The study of foliar endophytes from a variety of conifers including: Picea mariana, P. rubens and P. glauca as well as Abies balsamea and Larix laricina for the discovery of other anti-insect toxins are discussed. These endophytes are horizontally transmitted thus they are not present in nursery seedlings. Inoculating seedlings with toxigenic endophyte strains has been demonstrated to be effective in providing the tree with tolerance to herbivorous insects.

Penicillium species endophytic in coffee plants and ochratoxin A production

Tissues from Coffea arabica, C. congensis, C. dewevrei and C. liberica collected in Colombia, Hawaii and at a local plant nursery in Maryland were sampled for the presence of fungal endophytes. Surface sterilized tissues including roots, leaves, stems and various berry parts were plated on yeast-malt agar. DNA was extracted from a set of isolates visually recognized as Penicillium, and the internal transcribed spacer region and partial LSU-rDNA was amplified and sequenced. Comparison of DNA sequences with GenBank and unpublished sequences revealed the presence of 11 known Penicillium species: P. brevicompactum, P. brocae, P. cecidicola, P. citrinum, P. coffeae, P. crustosum, P. janthinellum, P. olsonii, P. oxalicum, P. sclerotiorum and P. steckii as well as two possibly undescribed species near P. diversum and P. roseopurpureum. Ochratoxin A was produced by only four isolates, one isolate each of P. brevicompactum, P. crustosum, P. olsonii and P. oxalicum. The role these endophytes play in the biology of the coffee plant remains enigmatic.

Allelopathic Effects on Germination and Seedling Growth of Clovers by Endophyte‐Free and ‐Infected Tall Fescue

Reports of allelopathy by tall fescue (Festucarundinacea Schreb.) on Trifolium species are inconsistent. Many tall fescue plants are infected with a fungal endophyte (Acremonium coenophialum Morgan‐Jones & Gams), which may account for some of the inconsistencies. My objective was to investigate the allelopathic effect of extracts of endophyte‐free (TF − E) and ‐infected (TF + E) tall fescue seeds the seed germination and seedling growth (shoot, root, and root‐hair length and root‐hair density) of five Trifolium species (ball clover, T. nigrescens Viv.; crimson clover, T. incarnatum L.; red clover, T. pratense L.; subterranean clover, T. subterraneum L.; and white clover, T. repens L.). Extracts were prepared by passing 50 g of seed through a pulverizing mill, soaking the milled seed in 500 mL of deionized water, filtering, and sterilizing the solution. Differences among allelopathic effects for seed germination were attributed to legume species. Although the presence of fungal endophyte had no effect on seed germination, germination of ball, crimson, and red clover seed was significantly reduced in extracts of tall fescue seed. Differences among allelopathic effects for shoot and root lengths were attributed to legume species. Seedling shoot length was significantly increased and root length was significantly decreased for clover seedlings grown in tall fescue extracts. Differences among allelopathic effects for root‐hair length and density were attributed to species and substrate (TF − E vs. TF + E) differences. There was a 34% reduction in root‐hair length and a 45% reduction in root‐hair density for clover seedlings grown in seed extracts compared with seedlings grown in water. Seed germination and seedling shoot and root lengths inadequately expressed the subtle allelopathic effects of the fungal endophyte. Micromorphological characters, such as root hairs, may be more sensitive in detecting allelopathic effects.

Barley yellow dwarf viruses in Japanese pasture grasses and lack of correlation with the presence of fungal endophytes

Pasture grasses from temperate Japan were tested for infection with barley yellow dwarf viruses (BYDVs) and fungal endophytes. BYDVs from both the MAV and RPV subgroups were detected, but no symptoms attributable to BYDV infection were observed. Not all isolates from the MAV subgroup could be clearly discriminated as MAV or PAV solely on ELISA results, and may have been intermediate serotypes or mixed infections. BYDVs were found to infect fescue (Festuca arundinacea: 17%), ryegrass (Lolium perenne: 41%), timothy (Phleum pratense: 94%) and Poa spp. (20%). Fescue and ryegrass were predominantly infected with RPV and PAV, respectively. The small collections of Poa spp. were only infected with PAV, while timothy was only tested for MAV subgroup viruses. In fescue 26% of tillers were infected with Acremonium coenophialum, and 60% of ryegrass tillers from an ecotype collection were infected with Acremonium lolii. There was no correlation between BYDV infection and the presence of endophytes for the above species or for Epichloe typhina‐infected (50%) timothy. An ELISA test for A. lolii did not detect A. coenophialum in fescue or E. typhina in timothy but showed good agreement with epidermal staining of A. lolii in ryegrass leaf sheaths.