Endophytic Association Research Articles

Micorrizas arbusculares y endófitos septados en tres especies de Thelypteridaceae de ambientes riparios de las Yungas (Tucumán, Argentina)

Background and aims: The status of the presence of arbuscular mycorrhizal fungi (AMF) in lycophytes and ferns has been analysed in 11% of them. This work aims to characterise and quantify the AMF colonisation and to characterise septate endophytes present on the roots of the Thelypteridaceae: Amauropelta jujuyensis, A. nubicola, and Pelazoneuron patens. M&M: Ten individuals per species were collected in August 2022. Conventional staining and techniques were used to estimate colonisation. Results: The root of Amauropelta jujuyensis, A. nubicola, and Pelazoneuron patens showed AMF with Arum and Paris morphological types simultaneously. The hyphal colonization showed no significant difference among species, arbuscular colonization was significantly higher in A. jujuyensis, while vesicular colonization was considerably higher in A. nubicola. In addition, septate endophytes were evident in the species of the genus Amauropelta. Conclusion: The association of AMF and other fungal endophytes with the native Argentine Thelypteridaceae Amauropelta jujuyensis, A. nubicola, and Pelazoneuron patens is evidenced for the first time in riparian environments of the Yungas. The coexistence of Arum and Paris morphological types in the three studied fern species is demonstrated.

Hongos micorrícicos arbusculares y endófitos septados oscuros en raíces de helechos nativos de uso medicinal de las Sierras Centrales de San Luis, centro-oeste de Argentina

Background and aims: The plant´s roots and fungi establish symbiotic endophytic associations that can coexist: arbuscular mycorrhizae and “dark septate” endophytes. Ferns and lycophytes are vascular plants that can form both fungal symbioses. The objective of this work is to detect the presence of fungal root endosymbiosis, know the mycorrhizal status, and analyze the type of colonizationin in native and ornamental ferns from the “Sierras Centrales de San Luis”. M&M: In three sites in the “Sierras Centrales de San Luis”, 9-10 individuals of each studied species were collected, their roots were processed to study these fungal. Characterization and quantification of their root colonization was evaluated. Results: In the three sites studied, Anemia tomentosa var. anthriscifolia formed mycorrhizal associations, the colonization presented abundant hyphal and arbusculated intracellular coils. In addition, glomoid spores of mycorrhizal fungi were found in their rhizospheres. Dark septate endophytes were absent in all species analyzed, none hyphae neither microsclerotia were recorded in roots of these native medicinal ferns. Conclusions: The mycorrhizal status of Anemia tomentosa var. anthriscifolia, one of the five medicinal fern species from the Sierras Centrales de San Luis studied, is presented. The arbuscular mycorrhizal colonization is described and quantified, and its type is determined as Paris. None of the fern species studied was associated with dark septate endophytes.

Novel epiphytic root-fungus symbiosis in the Indo-Pacific seagrass Thalassodendron ciliatum from the Red Sea.

Symbioses with fungi are important and ubiquitous on dry land but underexplored in the sea. As yet only one seagrass has been shown to form a specific root-fungus symbiosis that resembles those occurring in terrestrial plants, namely the dominant long-lived Mediterranean speciesPosidonia oceanica (Alismatales: Posidoniaceae) forming a dark septate (DS) endophytic association with the ascomycetePosidoniomyces atricolor (Pleosporales: Aigialaceae). Using stereomicroscopy, light and scanning electron microscopy, and DNA cloning, here we describe a novel root-fungus symbiosis in the Indo-Pacific seagrass Thalassodendron ciliatum (Alismatales: Cymodoceaceae)from a site in the Gulf of Aqaba in the Red Sea. Similarly to P. oceanica, the mycobiont of T. ciliatum occurs more frequently in thinner roots that engage in nutrient uptake from the seabed and forms extensive hyphal mantles composed of DS hyphae on the root surface. Contrary to P. oceanica, the mycobiont occurs on the roots with root hairs and does not colonize its host intraradically. While the cloning revealed a relatively rich spectrum of fungi, they were mostly parasites or saprobes of uncertain origin and the identity of the mycobiont thus remains unknown. Symbioses of seagrasses with fungi are probably more frequent than previously thought, but their functioning and significance are unknown. Melanin present in DS hyphae slows down their decomposition and so is true for the colonized roots. DS fungi may in this way conserve organic detritus in the seagrasses'rhizosphere, thus contributing to blue carbon sequestration in seagrass meadows.

Response of sod webworm Chrysoteuchia topiaria Zeller (Lepidoptera: Crambidae) to endophyte infection and mycotoxin profiles of cool‐season turfgrass species grown for seed in Oregon

AbstractThe subterranean sod webworm, also known as cranberry girdler (Chrysoteuchia topiaria), is one of the most damaging insect pests in cool‐season grass grown for seed crops in Oregon. Chemical control options are limited and require irrigation or rainfall for adequate insecticide incorporation to control C. topiaria larvae. Epichloë endophytes associated with cool‐season turfgrass species and their mycotoxin profiles are well‐documented in offering plant protection against invertebrates; these fungi may offer sustainable pest management tools. Our objectives were to characterize endophyte‐mediated resistance to C. topiaria in 19 commercially available cultivars of tall fescue, perennial ryegrass, and fine fescue grown for seed in Oregon. Endophyte status (presence and viability) of fungal endophytes and their mycotoxin profiles were measured using polymerase chain reaction, and liquid chromatography‐tandem mass spectrometry, respectively. No‐choice assays were conducted in the laboratory to measure the impact of endophyte status on C. topiaria larvae in two separate no‐choice experiments. Our results suggested that increased mortality of C. topiaria larvae (R2 = 0.8526, Experiment 1; R2 = 0.6628, Experiment 2) in tall fescue cultivars was most influenced by total peramine and ergot alkaloid, and total ergoline concentrations in Experiment 1 and 2, respectively. However, no significant effect on insect mortality was found in the perennial ryegrass and fine fescue cultivars included in this study. Overall, these findings suggest a viable grass–endophyte association can be utilized as a sustainable alternative to foliar insecticides for C. topiaria management in tall fescue seed crops.

Recent progress in the role of seed endophytic bacteria as plant growth-promoting microorganisms and biocontrol agents.

The importance of microorganisms residing within the host plant for their growth and health is increasingly acknowledged, yet the significance of microbes associated with seeds, particularly seed endophytic bacteria, remains underestimated. Seeds harbor a wide range of bacteria that can boost the growth and resilience of their host plants against environmental challenges. These endophytic associations also offer advantages for germination and seedling establishment, as seed endophytic bacteria are present during the initial stages of plant growth and development. Furthermore, plants can selectively choose bacteria possessing beneficial traits, which are subsequently transmitted through seeds to confer benefits to future generations. Interestingly, even with the ongoing discovery of endophytes in seeds through high-throughput sequencing methods, certain endophytes remain challenging to isolate and culture from seeds, despite their high abundance. These challenges pose difficulties in studying seed endophytes, making many of their effects on plants unclear. In this article, a framework for understanding the assembly and function of seed endophytes, including their sources and colonization processes was outlined in detail and available research on bacterial endophytes discovered within the seeds of various plant species has also been explored. Thus, this current review aims to provide valuable insights into the mechanism of underlying seed endophytic bacteria-host plant interactions and offers significant recommendations for utilizing the seed endophytic bacteria in sustainable agriculture as plant growth promoters and enhancers of environmental stress tolerance.

Epichloë fungal endophyte interactions in perennial ryegrass (Lolium perenne L.) modified to accumulate foliar lipids for increased energy density

BackgroundCommercial cultivars of perennial ryegrass infected with selected Epichloë fungal endophytes are highly desirable in certain pastures as the resulting mutualistic association has the capacity to confer agronomic benefits (such as invertebrate pest deterrence) largely due to fungal produced secondary metabolites (e.g., alkaloids). In this study, we investigated T2 segregating populations derived from two independent transformation events expressing diacylglycerol acyltransferase (DGAT) and cysteine oleosin (CO) genes designed to increase foliar lipid and biomass accumulation. These populations were either infected with Epichloë festucae var. lolii strain AR1 or Epichloë sp. LpTG-3 strain AR37 to examine relationships between the introduced trait and the endophytic association. Here we report on experiments designed to investigate if expression of the DGAT + CO trait in foliar tissues of perennial ryegrass could negatively impact the grass-endophyte association and vice versa. Both endophyte and plant characters were measured under controlled environment and field conditions.ResultsExpected relative increases in total fatty acids of 17–58% accrued as a result of DGAT + CO expression with no significant difference between the endophyte-infected and non-infected progeny. Hyphal growth in association with DGAT + CO expression appeared normal when compared to control plants in a growth chamber. There was no significant difference in mycelial biomass for both strains AR1 and AR37, however, Epichloë-derived alkaloid concentrations were significantly lower on some occasions in the DGAT + CO plants compared to the corresponding null-segregant progenies, although these remained within the reported range for bioactivity.ConclusionsThese results suggest that the mutualistic association formed between perennial ryegrass and selected Epichloë strains does not influence expression of the host DGAT + CO technology, but that endophyte performance may be reduced under some circumstances. Further investigation will now be required to determine the preferred genetic backgrounds for introgression of the DGAT + CO trait in combination with selected endophyte strains, as grass host genetics is a major determinant to the success of the grass-endophyte association in this species.

Bacterial Products and Their Effect on the Shrubby Legume Calicotome villosa (Poir.) Link

Calicotome villosa is a eurioic legume with broad distribution in the south of Europe. It can grow in almost any type of soil as well as in humid and dry and nutrient-deficient ecosystems. The broad distribution and eurioic nature of C. villosa may be attributed to its ability to establish endophytic associations with plant-growth-promoting (PGP) bacteria housed in the nodules and rootlets. This study examined the legume–microbe interaction of C. villosa growing in two contrasting locations: a hilltop with high sun irradiance and drought, and a valley bottom with a low level of radiation and sufficient soil humidity for plant growth. Calicotome villosa adult plants established endophytic interactions with bacteria in six genera: Pseudomonas, Stenotrophomonas, Bacillus, Paenibacillus, Brevicacterium, and Rhizobium. Plants growing on the hilltop had associated lower bacterial richness than those grown on the valley bottom. All strains were drought-tolerant and produced siderophores, IAA, HCN, and NH3 that stimulated plant performance in C. villosa plants and the other four legumes commonly present in the understory of the shrub communities. The legumes’ capacity to selectively host symbiotic bacteria that enhance plant survival in harsh conditions partly accounts for the diverse partnerships between C. villosa plants and their symbionts, ultimately explaining the wide distribution of this plant species.

Positive effects of Cordyceps cateniannulata colonization in tobacco: Growth promotion and resistance to abiotic stress.

Entomopathogenic fungi can live in insects to cause disease and death and are the largest group of entomopathogenic microorganisms. Therefore, these fungi are best known for their microbial control potential. Importantly, they also have other beneficial effects, including promoting plant growth and development by colonizing plant. Here, the study sought to identify specific strains of the entomopathogenic fungus, Cordyceps cateniannulata that would form endophytic associations with tobacco, thus benefiting plant growth and resistance to abiotic stresses, thereby highlighting the application of entomopathogenic fungi in tobacco. The C. cateniannulata-tobacco symbiont was constructed by root irrigation. The effects of C. cateniannulata on tobacco growth were evaluated by measuring the maximum leaf length, maximum leaf width, number of leaves, plant height, stem thickness, stem circumference, dry and fresh shoot weight 7, 14, 21, and 28 days after colonization. The peroxidase, catalase, superoxide dismutase, and malondialdehyde were measured to observe the impact of C. cateniannulata on tobacco defense enzyme activity. Finally, high-throughput sequencing was used to access microbial communities in the rhizosphere, with data subsequently linked to growth indicators. After tobacco was inoculated with C. cateniannulata X8, which significantly promoted growth and related enzyme activity, malondialdehyde was decreased. The most significant impact was on peroxidase, with its activity being upregulated by 98.20, 154.42, 180.65, and 170.38% in the four time periods, respectively. The high throughput sequencing results indicated that C. cateniannulata had changed the rhizosphere microbial relative abundances, such as increasing Acidobacteria and Ascomycetes, and decreasing Actinomycetes and Basidiomycetes. The redundancy analysis showed that C. cateniannulata significantly boosted tobacco growth by reducing the abundance of specific dominant genera such as Stachybotrys, Cephalotrichum, Streptomyces, Isoptericola, and Microbacterium. Specific strains of C. cateniannulata can be introduced into host plants as endophytes, resulting in promotion of host plant growth and increased resistance to abiotic stress and microbial pathogens. The study provides a foundation for future studies of C. cateniannulata as an ecological agent.

Global Change Factors Influence Plant-Epichloë Associations.

There is an increasing interest in determining the influence of global change on plant-microorganism interactions. We review the results of experiments that evaluated the effects of the global change factors carbon dioxide, ozone, temperature, drought, flooding, and salinity on plant symbioses with beneficial Epichloë endophytes. The factors affected the performance of both plants and endophytes as well as the frequency of plants symbiotic with the fungus. Elevated carbon dioxide levels and low temperatures differentially influenced the growth of plants and endophytes, which could compromise the symbioses. Furthermore, we summarise the plant stage in which the effects of the factors were quantified (vegetative, reproductive, or progeny). The factors ozone and drought were studied at all plant stages, but flooding and carbon dioxide were studied in just a few of them. While only studied in response to ozone and drought, evidence showed that the effects of these factors on symbiotic plants persisted trans-generationally. We also identified the putative mechanisms that would explain the effects of the factors on plant-endophyte associations. These mechanisms included the increased contents of reactive oxygen species and defence-related phytohormones, reduced photosynthesis, and altered levels of plant primary metabolites. Finally, we describe the counteracting mechanisms by which endophytes would mitigate the detrimental effects of the factors on plants. In presence of the factors, endophytes increased the contents of antioxidants, reduced the levels of defence-related phytohormones, and enhanced the plant uptake of nutrients and photosynthesis levels. Knowledge gaps regarding the effects of global change on plant-endophyte associations were identified and discussed.

Chaetomium albiziae, a new endophytic species from Albizia lebbeck in Iran

The silk tree (Albizia lebbeck (L.) Benth) is one of the ornamental plants in Ahvaz (southwest of Iran). Two endophytic fungal strains, isolated from the leaves of this plant, were characterized. Molecular phylogenetic analyses based on a combined matrix of the internal transcribed spacer regions 1 and 2 including the intervening 5.8S nuclear ribosomal DNA (ITS), and partial regions of the β-tubulin (tub2) and RNA polymerase II second largest subunit (rpb2) indicated that both strains represent a new Chaetomium species, C. albiziae sp. nov. in the family Chaetomiaceae. Chaetomium albiziae formed a sister lineage with sterile species C. cucumericola. This new species can be characterized by ostiolate perithecia with septate lateral and terminal setae, clavate asci and aseptate ellipsoidal to ovoid ascospores with an apical germ pore. In addition, this is the first report of the endophytic association of the genus Chaetomium with Albizia lebbeck worldwide.

Screening of Native Trichoderma Species for Nickel and Copper Bioremediation Potential Determined by FTIR and XRF

Soil pollution with heavy metals is a serious threat to the environment. However, soils polluted with heavy metals are considered good sources of native metal-resistant Trichoderma strains. Trichoderma spp. are free-living fungi commonly isolated from different ecosystems, establishing endophytic associations with plants. They have important ecological and biotechnological roles due to their production of a wide range of secondary metabolites, thus regulating plant growth and development or inducing resistance to plant pathogens. In this work we used indigenous Trichoderma strains that were previously isolated from different soil types to determine their tolerance to increased copper and nickel concentrations as well as mechanisms of metal removal. The concentrations of bioavailable metal concentrations were determined after extraction with diethylene-triamine pentaacetate (DTPA)-extractable metals (Cd, Cr, Co, Cu, Pb, Mn, Ni, and Zn) from the soil samples by inductively coupled plasma-optical emission spectrometry (ICP-OES). Two indigenous T. harzianum strains were selected for copper tolerance, and three indigenous T. longibrachiatum strains were selected for nickel tolerance tests. Strains were isolated from the soils with the highest and among the lowest DTPA-extractable metal concentrations to determine whether the adaptation to different concentrations of metals affects the mechanisms of remediation. Mechanisms of metal removal were determined using Fourier-transform infrared spectroscopy (FTIR) and X-ray fluorescence spectroscopy (XRF), non-destructive methods characterized by high measurement speed with little or no need for sample preparation and very low costs. Increased DTPA-extractable metal content for nickel and copper was detected in the soil samples above the target value (TV), and for nickel above the soil remediation intervention values (SRIVs), for total metal concentrations which were previously determined. The SRIV is a threshold of metal concentrations indicating a serious soil contamination, thus confirming the need for soil remediation. The use of FTIR and XRF methods revealed that the presence of both biosorption and accumulation of metals in the Trichoderma cells, providing good bioremediation potential for Ni and Cu.

Pathways of glyphosate effects on litter decomposition in grasslands

AbstractGrasslands store a third of global terrestrial carbon but are vulnerable to carbon loss due to inappropriate livestock grazing. Grasslands management can be improved with a mechanistic understanding of biogeochemical processes that determine carbon storage, such as plant litter decomposition.Herbicides, such as glyphosate, are used to improve the quantity and quality of the forage. In the Flooding Pampa, the most extensive cattle grazed natural grassland and one of the few remnants' temperate grasslands in South America—glyphosate is applied to promoteLolium multiflorum, a forage grass associated with a fungal endophyte nontoxic for cattle.We studied five mechanistic pathways in which the application of glyphosate can alter litter decomposition. We grouped them into single application pathways, through effects on living plants (1), leaf litter (2) and bare soil (3), and repeated annual application pathways, through legacies on ecosystem properties (4) and through the growth of an annual forage grass with a fungal endophyte (5). Single application pathways were tested in a greenhouse experiment using leaf litter ofL. multiflorumand of a native dominant grass. Repeated annual application pathways were tested through a field experiment with 3‐year annual glyphosate application using leaf and root litter ofL. multiflorumwith and without endophyte association.Glyphosate application on living plants produced leaf litter with 70% higher nitrogen content and 140% higher decomposition constant than naturally senesced litter. In contrast, glyphosate application on naturally senesced leaf litter reduced decomposition constant by 20%. Glyphosate application on the soil did not affect the decomposition of naturally senesced leaf litter but accelerated the decomposition of the glyphosate‐killed plants even more.Legacies of repeated annual application of glyphosate resulted in a notable reduction in plant cover (45%) and potential soil respiration (57%), with a consistent acceleration of leaf (53%) and root (18%) litter decomposition. Furthermore, endophytes inL. multiflorumplants reduced leaf litter decomposition by 22%. On the contrary, endophytes did not alter root litter decomposition.Glyphosate application on living plants and legacies of repeated application on the ecosystem stimulate litter decomposition, which can result in a net carbon loss from grasslands. In other ecosystems, the net result on decomposition would depend on the relative cover of vegetation, above‐ground litter and bare soil. This study highlights that glyphosate application should be considered when evaluating sustainable management to preserve and enhance soil carbon storage in grasslands.Read the freePlain Language Summaryfor this article on the Journal blog.

Negative effects on the development of Chrysodeixis includens and Spodoptera cosmioides fed by peanut plants inoculated with entomopathogenic fungi.

Recent studies have shown that entomopathogenic fungi, as endophytes, can have beneficial effects on plants, protecting them from defoliating insects. The potential of endophytic association by entomopathogenic fungi with the peanut crop has been little explored. In our study, we conducted experiments by inoculation of peanut seeds through a soil drench method with nine strains/species of entomopathogenic fungi of the genera Metarhizium, Beauveria and Cordyceps, subsequently these plants were consumed by two larval pests, Chrysodeixis includens and Spodoptera cosmioides. The parameters of larval growth rates, mortality, foliar consumption and larval period were observed during the development of larvae. In addition, the endophytic capacity of these fungi in peanut plants and their persistence in soil were investigated. In two replicate greenhouse trials for each larva, peanut plants were inoculated with fungi by the soil-drench method. We evaluated the performance of C. includens and S. cosmioides feeding on inoculated peanut plants starting at the 2nd larval instar. The larval and pupal weights of C. includens and S. cosmioides were significantly different among the fungal treatment groups, where insects feeding on control plants exhibited higher larval and pupal weights than insects feeding on treated plants. The differences in larval period showed that Control larvae pupated faster than the larvae fed on fungal-inoculated plants, fungal treatments had a larval period of 3 to 5 days more than the control. The mortality rates of C. includens and S. cosmioides were significantly different among the fungal treatment groups, insects fed on Control plants exhibited higher survival than insects fed on fungal-inoculated plants. The persistence of all Metarhizium fungi was higher in the soil compared to other fungi, and only Metarhizium and B. bassiana IBCB215 emerged from the phyllosphere of peanut plants. Although the fungus Cordyceps presented the worst performance among the fungal treatments. Overall, our results demonstrate the negative effects on the development of C. includens and S. cosmioides that were fed on fungal-inoculated peanut plants, the best results recorded were for Metarhizium strains and the fungus B. bassiana IBCB215.

Translocation of Loline Alkaloids in Epichloë-Infected Cereal and Pasture Grasses: What the Insects Tell Us.

Aphids are major pests of cereal and pasture grasses throughout the world, vectoring disease and reducing plant production. There are few control options other than insecticides. Epichloë endophytes that produce loline alkaloids in their hosts provide a possible mechanism of control, with both meadow fescue and tall fescue naturally infected with loline-producing endophytes showing a resistance to Rhopalosiphum padi. We screened Elymus spp. naturally infected with endophytes that produced loline alkaloids at concentrations known to affect aphids on fescue but found no effect on these insects infesting Elymus. A synthetic loline-producing endophyte association with rye also had no effect on the aphids. After hypothesizing that the lolines were being translocated in the xylem in Elymus and rye rather than the phloem, we tested the rye and meadow fescue infected with loline-producing endophytes against a xylem feeding spittlebug. The endophyte in rye inhibited the feeding of the insect and reduced its survival, whereas the endophyte-infected meadow fescue had no effect on the spittlebug but reduced the number of aphids. Lolines applied to the potting medium of endophyte-free and endophyte-infected rye, ryegrass, and tall fescue resulted in a decrease in the aphid populations on the endophyte-free pasture grasses relative to the untreated controls but had no effect on aphid numbers on the rye. We tentatively conclude that lolines, produced in both natural and synthetic association with Elymus and rye, are partitioned in the xylem rather than the phloem, where they are inaccessible to aphids.

Epichloë bromicola from wild barley improves salt-tolerance of cultivated barley by altering physiological responses to salt stress.

Epichloë bromicola is a cultivable fungal endophyte that lives in symbiosis with wild barley (Hordeum brevisubulatum) to which it confers salt tolerance. This study tested the hypothesis that E. bromicola derived from wild barley has the potential to increase salt tolerance in cultivated barley under salt stress. To test this hypothesis, the growth response, physiological parameters, and metabolic profiles of barley plants inoculated with E. bromicola (E+) and those not inoculated with E. bromicola (E-) were compared under salt stress. Compared with E- barley plants, E+ barley plants had significantly increased plant height, shoot biomass, total biomass, chlorophyll content, osmotic synthesis, and accumulation of stress adaptation metabolites. E. bromicola increased the salt stress tolerance of cultivated barley, and the positive effects correlated with different salt stress conditions. These results suggest that E. bromicola has promising potential for enhancing the salt tolerance of barley. New insights into the mechanisms underlying this barley-fungal endophyte association are provided, and interesting questions regarding the role of E. bromicola in fungus-enhanced tolerance to salt stress in this symbiosis are raised.

Host generalists dominate fungal communities associated with alpine knotweed roots: a study of Sebacinales.

Bistorta vivipara is a widespread herbaceous perennial plant with a discontinuous pattern of distribution in arctic, alpine, subalpine and boreal habitats across the northern Hemisphere. Studies of the fungi associated with the roots of B. vivipara have mainly been conducted in arctic and alpine ecosystems. This study examined the fungal diversity and specificity from root tips of B. vivipara in two local mountain ecosystems as well as on a global scale. Sequences were generated by Sanger sequencing of the internal transcribed spacer (ITS) region followed by an analysis of accurately annotated nuclear segments including ITS1-5.8S-ITS2 sequences available from public databases. In total, 181 different UNITE species hypotheses (SHs) were detected to be fungi associated with B. vivipara, 73 of which occurred in the Bavarian Alps and nine in the Swabian Alps–with one SH shared among both mountains. In both sites as well as in additional public data, individuals of B. vivipara were found to contain phylogenetically diverse fungi, with the Basidiomycota, represented by the Thelephorales and Sebacinales, being the most dominant. A comparative analysis of the diversity of the Sebacinales associated with B. vivipara and other co-occurring plant genera showed that the highest number of sebacinoid SHs were associated with Quercus and Pinus, followed by Bistorta. A comparison of B. vivipara with plant families such as Ericaceae, Fagaceae, Orchidaceae, and Pinaceae showed a clear trend: Only a few species were specific to B. vivipara and a large number of SHs were shared with other co-occurring non-B. vivipara plant species. In Sebacinales, the majority of SHs associated with B. vivipara belonged to the ectomycorrhiza (ECM)-forming Sebacinaceae, with fewer SHs belonging to the Serendipitaceae encompassing diverse ericoid–orchid–ECM–endophytic associations. The large proportion of non-host-specific fungi able to form a symbiosis with other non-B. vivipara plants could suggest that the high fungal diversity in B. vivipara comes from an active recruitment of their associates from the co-occurring vegetation. The non-host-specificity suggests that this strategy may offer ecological advantages; specifically, linkages with generalist rather than specialist fungi. Proximity to co-occurring non-B. vivipara plants can maximise the fitness of B. vivipara, allowing more rapid and easy colonisation of the available habitats.

Endophytic Beauveria bassiana can protect the rice plant from sheath blight of rice caused by Rhizoctonia solani and enhance plant growth parameters.

Beauveria bassiana, a potential entomopathogenic biocontrol agent, has recently drawn attention worldwide for its other additional beneficial roles such as plant disease antagonist, beneficial rhizosphere colonizer, plant growth promoter and an endophyte. In the present study, endophytic colonizing behaviour of five (5) B. bassiana isolates viz., Bb4, Bb16, Bb25, Bb44 and Bb53 were studied in rice following three (3) artificial inoculation techniques viz., seed treatment, root inoculation and foliar spray and the endophytic colonizing ability were determined by culture-based assay. After B. bassiana inoculation, rice plants were challenged with Rhizoctonia solani and disease incidence and plant growth promotion were assessed. Per cent colonization of rice stems, leaves and roots were influenced by inoculation technique, post-inoculation time (7th, 14th, 21st and 28th dpi) and plant growth medium (sterile soil, non-sterile soil), recorded maximum on 14th-day post-inoculation (dpi) i.e., 96% in stems, 92% in leaves and 28% in roots, whereas, lower colonization was recorded on 7th, 21st and 28th dpi. Whereas, the foliar spray was found best as compared to seed and root inoculation techniques, and maximum fungal recovery was observed in stems and leaves and least in roots. Upon colonization, the physical presence of B. bassiana in rice was localized by light microscopy-based studies. Potential B. bassiana strains with endophytic ability were re-isolated and their identity was determined based on morphometric and PCR-based techniques. Further, the present study also identified several virulent genes viz., BbChit1, Cdep1, Bbhog1 and Bbjen1 and extracellular hydrolytic enzymes viz., α-amylase, cellulase, lipase, pectinase and xylanase secreted by endophytic B. bassiana strains as determinants responsible for establishing the endophytic association in rice. On the other hand, a significant reduction in disease incidence was observed in the endophytic B. bassiana Bb4-, Bb16- and Bb44-inoculated plants as compared to the non-endophytic B. bassiana Bb25- and Bb53-inoculated plants along with enhanced plant growth promotion. This is one of the few studies investigating the colonization of B. bassiana in rice and its promising role as a plant disease antagonist and plant growth promoter in rice.

Improvement in the physiological and biochemical performance of strawberries under drought stress through symbiosis with Antarctic fungal endophytes.

Strawberry is one of the most widely consumed fruit, but this crop is highly susceptible to drought, a condition strongly associated with climate change, causing economic losses due to the lower product quality. In this context, plant root-associated fungi emerge as a new and novel strategy to improve crop performance under water-deficiency stress. This study aimed to investigate the supplementation of two Antarctic vascular plant-associated fungal endophytes, Penicillium brevicompactum and Penicillium chrysogenum, in strawberry plants to develop an efficient, effective, and ecologically sustainable approach for the improvement of plant performance under drought stress. The symbiotic association of fungal endophytes with strawberry roots resulted in a greater shoot and root biomass production, higher fruit number, and an enhanced plant survival rate under water-limiting conditions. Inoculation with fungal endophytes provokes higher photosynthetic efficiency, lower lipid peroxidation, a modulation in antioxidant enzymatic activity, and increased proline content in strawberry plants under drought stress. In conclusion, promoting beneficial symbiosis between plants and endophytes can be an eco-friendly strategy to cope with drought and help to mitigate the impact of diverse negative effects of climate change on crop production.

Diazotrophic endophytic bacterium Alcaligenes sp. KA31 and its role in promoting the growth of wheat (Triticum aestivum L.) under saline conditions

Intensification of food production with an increasing world population, to achieve food security has become one of the major agricultural challenges for a sustainable future. Salinity is the second most abundant threat after drought which causes disturbance in the symbiotic performance of plants and increases their susceptibility to detrimental soil-borne pathogens. In the present study, endophytic diazotroph KA31 isolated from roots of wheat plant was characterized and identified as Alcaligenes faecalis . The bacterial endophytic isolate produced indole acetic acid (IAA), and siderophore along with the potential to solubilize phosphorous (P). KA31 was also able to fix nitrogen (N) as evaluated through acetylene reduction assay and nifH -PCR assay. Recolonization ability of A. faecalis in the wheat seedlings was studied under laboratory conditions and it was demonstrated that KA31 was able to establish an endophytic association with the host plant. Furthermore, in the pot experimental study, A. faecalis KA31 significantly improved the growth parameters of wheat plants under saline conditions as compared to untreated control plants. Presumably this is the first study that reports A. faecalis as salt tolerant diazotrophic plant growth promoting endophyte (PGPE) and overall the work depicts that novel bioformulations developed using them can be effective for wheat crops grown in saline soils.

Multifarious pigment producing fungi of Western Ghats and their potential

Concerns about the negative impacts of synthetic colorants on both consumers and the environment have sparked a surge of interest in natural colorants. This has boosted the global demand for natural colorants in the food, cosmetics and textile industries. Pigments and colorants derived from plants and microorganisms are currently the principal sources used by modern industry. When compared to the hazardous effects of synthetic dyes on human health, natural colors are quickly degradable and have no negative consequences. In fact, fungal pigments have multidimensional bioactivity spectra too. Western Ghats, a biodiversity hotspot has a lot of unique ecological niches known to harbor potential endophytic pigment-producing fungi having enumerable industrial and medical applications. Most of the fungi have coevolved with the plants in a geographical niche and hence the endophytic associations can be thought to bring about many mutually beneficial traits. The current review aims to highlight the potential of fungal pigments found in the Western ghats of India depicting various methods of isolation and screening, pigment extraction and uses. There is an urgent need for bioprospecting for the identification and characterization of extremophilic endophytic fungi to meet industry demands and attain sustainability and balance in nature, especially from geographic hotspots like the Western Ghats.