Endophytes Of Grasses Research Articles

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.

The Interaction between Arbuscular Mycorrhizal Fungi (AMF) and Grass Endophyte (Epichloë) on Host Plants: A Review.

In nature, plants frequently experience concurrent colonization with arbuscular mycorrhizal fungi (AMF) and grass endophytes (Epichloë). These two fungi assist in mineral uptake and stress tolerance by the host. Despite the abundance of recent studies exploring the individual functions of these fungi in diverse ecosystems, research on the effects of the interaction between these two symbiotic fungi on the host, particularly in agricultural production and ecological conservation. This review provides an overview of the current knowledge regarding the interaction between AMF and grass endophytes and their synergistic effects on host plants in response to abiotic and biotic stress, while also outlining prospects for future research in this field. This knowledge not only enhances our comprehension of complex interaction effects between the two fungi, but also facilitates the optimal utilization of fungal resources, contributing to ecological construction and higher agricultural production.

Colonization dynamic and distribution of the endophytic fungus Microdochium bolleyi in plants measured by qPCR.

Microdochium bolleyi is a fungal endophyte of cereals and grasses proposed as an ideal model organism for studying plant-endophyte interactions. A qPCR-based diagnostic assay was developed to detect M. bolleyi in wheat and Brachypodium distachyon tissues using the species-specific primers MbqITS derived from the ITS of the ribosomal gene. Specificity was tested against 20 fungal organisms associated with barley and wheat. Colonization dynamics, endophyte distribution in the plant, and potential of the seed transmission were analyzed in the wheat and model plant B. distachyon. The colonization of plants by endophyte starts from the germinating seed, where the seed coats are first strongly colonized, then the endophyte spreads to the adjacent parts, crown, roots near the crown, and basal parts of the stem. While in the lower distal parts of roots, the concentration of M. bolleyi DNA did not change significantly in successive samplings (30, 60, 90, 120, and 150 days after inoculation), there was a significant increase over time in the roots 1 cm under crown, crowns and stem bases. The endophyte reaches the higher parts of the base (2-4 cm above the crown) 90 days after sowing in wheat and 150 days in B. distachyon. The endophyte does not reach both host species' leaves, peduncles, and ears. Regarding the potential for seed transmission, endophyte was not detected in harvested grains of plants with heavily colonized roots. Plants grown from seeds derived from parental plants heavily colonized by endophyte did not exhibit any presence of the endophyte, so transmission by seeds was not confirmed. The course of colonization dynamics and distribution in the plant was similar for both hosts tested, with two differences: the base of the wheat stem was colonized earlier, but B. distachyon was occupied more intensively and abundantly than wheat. Thus, the designed species-specific primers could detect and quantify the endophyte in planta.

Tripartite associations: A bacterial symbiont of fungi promotes plant growth without compromising the benefits conferred by an Epichloë endophyte

Few studies have evaluated the effects of bacteria that form associations with fungi on plant-microbial symbioses. We investigated the effects of a novel symbiotic bacterium (E226) of Epichloë, a well-researched mutualistic fungal endophyte of grasses, on perennial ryegrass (Lolium perenne) also associated with Epichloë. We hypothesised that E226 would promote plant growth but would not interfere with the in-planta growth of Epichloë and its production of antiherbivore alkaloids. E226, identified as Micrococcus luteus, formed an ectosymbiotic relationship with Epichloë when cultured on artificial media (i.e., bacterial cells were located on the hyphal surface) and possessed plant-growth promoting traits identified through whole genome analysis. Seeds of L. perenne, already colonised by an Epichloë strain, were inoculated with E226. The bacterium established within the seedlings, and the abundance of M. luteus populations initially increased with plant age. In agreement with our hypotheses, plant inoculation with E226 enhanced the production of leaves and did not affect the growth of Epichloë or the concentration of Epichloë-derived alkaloids. The putative abilities of E226 to solubilise phosphate and produce vitamins and metabolic cofactors may explain the observed plant growth promotion.

Identification of Cultured and Diazotrophic Bacterial Endophytes in Warm-Season Grasses

Endophytes can have positive effects on plant health and growth, but endophytes of warm-season grasses are largely understudied, and inocula are rarely applied to cultivated grasses. To identify endophytes in warm-season grasses, 35 endophytic bacterial isolates were cultured from the roots, rhizomes, and shoots of bermudagrass ( Cynodon dactylon), energy cane ( Saccharum spp.), Johnsongrass ( Sorghum halepense), napiergrass ( Cenchrus purpureus), perennial sorghum ( Sorghum bicolor × S. halepense), sorghum ( Sorghum bicolor), sorghum × sudangrass ( Sorghum × drummondii), and peanut (outgroup). Sequencing of the 16S rRNA fragment from the endophytes revealed that the bacterial sequences were similar to Bacillus spp. (19 isolates), Burkholderia spp. (4), Pantoea spp. (4), Pseudomonas spp. (3), Enterobacter spp. (2), Kosakonia spp . (2), and Sphingomonas sp. (1). To identify diazotrophic endophytes, DNA isolated from surface-disinfected tissue from warm-season grasses was used to amplify nifH. Bacteria containing nifH were similar to 13 genera, and sequences similar to Pseudolabrys sp. were present in the greatest number of warm-season grasses. Bacteria similar to Bradyrhizobium frederickii strain CNPSo 3447 were identified frequently from the leaves and roots of sorghum × sudangrass (and peanut roots). Using similarity to known nifH fragments, six genera were identified that had not been previously identified in grasses. Thus, a large number of endophytes were found in warm-season grasses and could enhance plant growth or grass nitrogen levels by using nitrogen fixation. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2023.

The fungus Clonostachys epichloë alters the influence of the Epichloë endophyte on seed germination and the biomass of Puccinellia distans grass.

The fungal grass endophyte Epichloë typhina (Pers.) Tul. & C. Tul. (Ascomycota: Clavicipitaceae) grows intercellulary in aerial plant parts and reproduces asexually by invading host seeds. In this phase, it enhances seed production and germination, which accelerates its vertical spread. This relationship may be distorted by other seed-born fungi, whose spread is not so directly dependent on the success of the grass. Recently, the fungus Clonostachys epichloë Schroers has been observed on Puccinellia distans (Jacq.) Parl seeds originating from grass clumps infested with stromata, sexual structures of Epichloë typhina that are formed in spring on some host culms, preventing flower and seed development ('choke disease'). C. epichloë shows mycoparasitic activity toward Epichloë stromata by reducing the production of ascospores, which are responsible for horizontal transmission of the fungus. The aim of this study was to investigate the effect of seed-borne C. epichloë on seed germination, as well as the size and weight of P. distans seedlings and to examine whether C. epichloë alters the influence of Epichloë in the early developmental stages of P. distans. The results showed that if C. epichloë acts on seeds together with E. typhina endophytes, the seeds were negatively affected due to the elimination of the positive effect of the latter in terms of both seed germination rate and seedling length. At the same time, C. epichloë increased the proportion of E. typhina-untreated germinated seeds. Additionally, only the joint action of the two fungi, E. typhina and C. epichloë, effectively stimulated seedling dry mass; the presence of E. typhina alone was not sufficient to noticeably affect seedling size. Based on the increasing commonality of C. epichloë on Epichloë stromata, as well as its potential to be used in biocontrol of 'choke disease', we should take a closer look at this fungus, not only in terms of its mycoparasitic ability, but also in terms of its cumulative impact on the whole Epichloë-grass system.

Microecosystem of yak rumen on the Qinghai-Tibetan Plateau is stable and is unaffected by soil or grass microbiota.

The rumen of livestock grazing on the Qinghai-Tibetan Plateau (QTP) acts as a transfer station for the circulation of soil, grass, faecal mineral elements and nutrients. Whether the microorganisms from the soil and grass could circulate through livestock rumen and excreted faeces. We studied the structural composition and interactive networks of microbiomes (bacteria and fungi) in soil, grass, and grazing yaks (rumen and faeces) on the QTP by using 16S rRNA gene and internally transcribed spacer (ITS)sequencing technology and to calculate the contribution rate of microorganisms from one habitat to another habitat using SourceTracker analysis. The meta-co-occurrence network revealed that soil, grass, rumen, and faeces comprise four independent habitats. The bacterial and fungal composition was significantly different in these four habitats. Soil microbiota showed the highest alpha diversity and microbial network complexity. Rumen microbiota demonstrated the highest microbial network stability and synergy, while grass endophytes showed the lowest microbial network complexity, stability, and synergy. According to the SourceTracker model, grass contributes 0.02% to the rumen microbes of yaks, while soil microorganisms do not circulate in the rumen. The soil and grass microbiota originating from faeces were 4.5% and 1.2%, respectively. The contribution of soil to grass was found to be 1.1%. Overall, the rumen microbiota of yaks is relatively stable and is only minimally influenced by the microbiota inhabiting the environment under natural grazing conditions. However, the contribution of yaks to soil and grass microbiota is relatively high when compared with the contribution of soil and grass to yaks microbiota.

Tolerance of 2-Benzoxazolinone and Interactions with Grass and Pine Hosts in a Population of Fusarium circinatum.

Fusarium circinatum, the causal agent of pitch canker in pines and a cryptic endophyte of grasses, was examined for heritable variation in tolerance of the grass defense compound 2-benzoxazolinone (BOA). A diverse population of F. circinatum progeny was assayed for growth rate on potato dextrose agar amended with BOA. Matings were conducted to allow for selection of progeny with lower and higher tolerance of BOA. The results confirmed heritable variation in BOA tolerance in F. circinatum. A subset of differentially tolerant progeny was used for inoculations of growth chamber-grown Zea mays and greenhouse-grown Pinus radiata. No differences were detected in the rate of infection or extent of colonization of Z. mays inoculated with F. circinatum progeny differing in tolerance of BOA. Pitch canker symptoms in inoculated P. radiata trees showed that high BOA-tolerating isolates induced significantly longer lesion lengths than those induced by low BOA-tolerating isolates. Results from this study were consistent with the proposition that F. circinatum evolved from grass-colonizing ancestors and that pathogenicity to pine is a relatively recent evolutionary innovation.

Interactions between silicon and alkaloid defences in endophyte‐infected grasses and the consequences for a folivore

AbstractGrasses have developed a wide range of morphological and physiological mechanisms to resist herbivory. For instance, they accumulate silicon (Si) in tissue, as physical defence, and associate symbiotically with foliarEpichloë‐endophytes that provide chemical defence via antiherbivore alkaloids. Recent evidence showed that someEpichloë‐endophytes increase foliar Si in forage grasses; however, whether this impacts insect herbivores is unknown. Furthermore, while Si is primarily a physical defence, it also affects production of plant defensive secondary metabolites; Si supply might therefore affectEpichloë‐alkaloids, although this remains untested.We grew endophyte‐free (Nil) andEpichloë‐infected tall fescue and perennial ryegrass in a factorial combination with or without Si supplementation, in the absence or presence ofHelicoverpa armigera.Epichloë‐endophyte strains were AR584 for tall fescue, and AR37, AR1 or Wild‐type (WT) for perennial ryegrass. We assessed how Si supply andEpichloë‐endophytes in interaction with herbivory affected foliar Si and mutualist‐derived alkaloid concentrations. Subsequently, their effects onH. armigerarelative growth rates (RGRs) were evaluated.Endophytes generally increased Si concentrations in Si‐supplied plants. In tall fescue AR584 and perennial ryegrass AR37, endophytes increased constitutive (herbivore‐free) and induced (herbivore‐inoculated) Si concentrations by at least 25%; in contrast, in perennial ryegrass, the AR1 endophyte only increased constitutive levels. Si supply did not affect alkaloids produced by AR584 or AR1/WT endophytes; however, in the presence of herbivory, Si supply decreased the induction of alkaloids produced by AR37 endophytes by 33%. For tall fescue, Si supply reducedH. armigeraRGR by at least 76%, regardless of endophytic status, whereas, endophyte‐alkaloids played a secondary role only reducing herbivore growth in the absence of Si supply. Conversely, in perennial ryegrass, both Si and endophyte‐alkaloids (regardless of Si supply) reduced herbivore RGR although not synergised.Novel interactions between constitutive and induced Si‐ and alkaloid‐based antiherbivore defences in grasses were observed. Overall, Si had a greater effect on the folivore than endophytes in both grasses. Endophyte defences contributed more to herbivore resistance in perennial ryegrass than tall fescue. We demonstrate that Si and endophytes were not antagonistic and highlight that the protective nature of their interaction varies with the grass‐endophyte species tested.A freePlain Language Summarycan be found within the Supporting Information of this article.

The role of Epichloë grass endophytes during pasture renewal

The literature on the importance of Epichloë grass endophytes during pasture renewal is reviewed. Perennial ryegrass endophyte strains such as AR1, NEA2, and Standard Endophyte (SE) as well as tall fescue and meadow fescue endophytes, significantly increase seedling survival at establishment under insect pressure, for example from adult Argentine stem weevil, grass grub, and African black beetle. However, in endophyte-infected ryegrass, insect-derived plant damage increases 10–43 days after sowing despite the presence of endophyte. Insecticidal seed treatments can mitigate the vulnerability to insect predation during this time.

Non-Transgenic CRISPR-Mediated Knockout of Entire Ergot Alkaloid Gene Clusters in Slow-Growing Asexual Polyploid Fungi.

The Epichloë species of fungi include seed-borne symbionts (endophytes) of cool-season grasses that enhance plant fitness, although some also produce alkaloids that are toxic to livestock. Selected or mutated toxin-free endophytes can be introduced into forage cultivars for improved livestock performance. Long-read genome sequencing revealed clusters of ergot alkaloid biosynthesis (EAS) genes in Epichloë coenophiala strain e19 from tall fescue (Lolium arundinaceum) and Epichloë hybrida Lp1 from perennial ryegrass (Lolium perenne). The two homeologous clusters in E. coenophiala—a triploid hybrid species—were 196 kb (EAS1) and 75 kb (EAS2), and the E. hybrida EAS cluster was 83 kb. As a CRISPR-based approach to target these clusters, the fungi were transformed with ribonucleoprotein (RNP) complexes of modified Cas9 nuclease (Cas9-2NLS) and pairs of single guide RNAs (sgRNAs), plus a transiently selected plasmid. In E. coenophiala, the procedure generated deletions of EAS1 and EAS2 separately, as well as both clusters simultaneously. The technique also gave deletions of the EAS cluster in E. hybrida and of individual alkaloid biosynthesis genes (dmaW and lolC) that had previously proved difficult to delete in E. coenophiala. Thus, this facile CRISPR RNP approach readily generates non-transgenic endophytes without toxin genes for use in research and forage cultivar improvement.

Antimicrobial activity and metabolite profiling of endophytic fungi in Digitaria bicornis (Lam) Roem. and Schult. and Paspalidium flavidum (Retz.) A. Camus.

Endophytic fungal occurrences were studied in aerial regions of Digitaria bicornis and Paspalidium flavidum by three isolation methods: potato dextrose agar (PDA), malt extract agar (MEA), and moist blotters. Seventy species of 29 genera of endophytic fungi in D. bicornis and 71 species of 30 genera in P. flavidum were documented. Endophytic fungal communities were grouped into 40 and 43 anamorphic ascomycetes (21 and 23 genera) and 20 teleomorphic ascomycetes (6 and 7 genera) in D. bicornis and P. flavidum, respectively. PDA supported the expression of larger number of fungal communities than MEA and MB; and P. flavidum hosted more number of endophytic fungi than D. bicornis. Seasons played an important role in supporting the assemblage of fungal endophytes. Endophytic fungal species richness and assemblages in plant regions were determined for alpha, beta, and gamma diversities. The ethyl acetate followed by methanolic extracts of certain fungal species showed good antagonistic and antibacterial activities. Among fungal endophytes, Curvularia protuberata and Penicillium citrinum exhibited high antagonistic and antibacterial activities. The high-resolution orbitrap liquid chromatography-mass spectrometry of ethyl acetate crude extracts of C. protuberata and P. citrinum revealed the presence of antifungal and antimicrobial, besides a host of compounds in the extracts. The present study indicated that grass endophytes are the sources of compounds with antimicrobial and other pharmacological activities.

Influence of Epichloë coenophiala, a seed-borne endophyte, on the micropropagation of tall fescue

Fil: Regalado Gonzalez, Jose Javier. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Micologia y Botanica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micologia y Botanica; Argentina

Arbuscular mycorrhizal fungus identity modulates growth effects of endophyte-infected grasses on neighboring plants.

Endophytes of grasses have been reported to affect the colonization by arbuscular mycorrhizal fungi (AMF) not only of their dual host plant but also of neighboring non-endophyte-infected plants. However, studies investigating the impact of AMF identity on the effects of endophyte-infected grasses on neighboring plants are rare. In this study, we investigated the influence of Leymus chinensis litter type (NL, no litter; E-, endophyte-free litter; E-E+, half E+ and half E- litter; E+, endophyte-infected litter) on Stipa krylovii growth with different AMF species (Claroideoglomus etunicatum, CE; Funneliformis mosseae, FM; Claroideoglomus claroideum, CC; Rhizophagus intraradices, RI). The results showed that the root biomass of S. krylovii tended to decrease with the increase of E+ litter in the mycorrhiza-free treatment. With AMF inoculation, the effects of E+ litter on the AMF colonization rate and root biomass of S. krylovii varied with AMF species. Structural equation modeling (SEM) showed E+ litter could modulate the growth of S. krylovii indirectly via changes in AMF colonization rate, but this effect was related to AMF species.

Insect oviposition preference between Epichloë-symbiotic and Epichloë-free grasses does not necessarily reflect larval performance.

Variation in plant communities is likely to modulate the feeding and oviposition behavior of herbivorous insects, and plant‐associated microbes are largely ignored in this context. Here, we take into account that insects feeding on grasses commonly encounter systemic and vertically transmitted (via seeds) fungal Epichloë endophytes, which are regarded as defensive grass mutualists. Defensive mutualism is primarily attributable to alkaloids of fungal origin. To study the effects of Epichloë on insect behavior and performance, we selected wild tall fescue (Festuca arundinacea) and red fescue (Festuca rubra) as grass–endophyte models. The plants used either harbored the systemic endophyte (E+) or were endophyte‐free (E−). As a model herbivore, we selected the Coenonympha hero butterfly feeding on grasses as larvae. We examined both oviposition and feeding preferences of the herbivore as well as larval performance in relation to the presence of Epichloë endophytes in the plants. Our findings did not clearly support the female's oviposition preference to reflect the performance of her offspring. First, the preference responses depended greatly on the grass–endophyte symbiotum. In F. arundinacea, C. hero females preferred E+ individuals in oviposition‐choice tests, whereas in F. rubra, the endophytes may decrease exploitation, as both C. hero adults and larvae preferred E− grasses. Second, the endophytes had no effect on larval performance. Overall, F. arundinacea was an inferior host for C. hero larvae. However, the attraction of C. hero females to E+ may not be maladaptive if these plants constitute a favorable oviposition substrate for reasons other than the plants' nutritional quality. For example, rougher surface of E+ plant may physically facilitate the attachment of eggs, or the plants offer greater protection from natural enemies. Our results highlight the importance of considering the preference of herbivorous insects in studies involving the endophyte‐symbiotic grasses as host plants.

Sarocladium graminicola, a new endophytic species from tropical grasses

Sarocladium species are common endophytes of tropical forage grasses and may offer benefits to host plants against biotic and abiotic stresses. We investigated a collection of 88 Sarocladium isolates previously obtained as endophytes from Panicum maximum, Pennisetum purpureum, Cynodon nlemfuensis, and Brachiaria spp. in Brazil. Multilocus phylogenetic analyses and morphological characterization were used for species delimitation. Sixty-eight isolates were identified as S. spinificis, and five as S. terricola; S. bactrocephalum, S. kiliense, S. spirale, and S. strictum were represented by one to three isolates. A well-supported clade containing eight endophytic isolates occupied a sister position to the clade containing S. bactrocephalum, S. mali, and S. strictum, and is described as a new taxon, Sarocladium graminicola. This work provides new insights on the distribution and diversity of endophytic Sarocladium species in the tropics.

Variation and plasticity in Epichloë alkaloid content of Festuca rubra across Europe

Abstract Many symbiotic microbes can aid their host plant's defense against herbivores and pathogens either directly or indirectly through plant-mediated mechanisms. Thus, microbes are of interest to agricultural research. In this study, we used vertically transmitted Epichloe species because these fungal endophytes of grasses produce alkaloids that have been shown to protect the host from herbivory. Depending on the amount, type, and profile of alkaloids, Epichloe species can promote the host's defense against invertebrate or vertebrate herbivores. Here, we used Festuca rubra colonized by Epichloe festucae from wild populations of different geographic origins in a reciprocal transplant experiment at three locations across Europe. We sought to determine whether genetic differences among Epichloe-colonized plants from different origins or phenotypic plasticity explained variations in alkaloid content and whether the alkaloid content was correlated with the growth and reproduction of the plants colonized by Epichloe. We found that the geographic origin of the Epichloe-colonized genotypes explained differences in ergovaline and peramine production. The ergovaline content also indicated chemotypic plasticity, as profiles changed when transplanted to a new environment, while the concentration of peramine was constant among the transplantation sites. The lack of a strong correlation between alkaloid content and plant performance (number of reproductive stems and total biomass) indicated that the costs of alkaloid production were too low to have consequences for fitness in terms of those parameters. Our findings emphasize the importance of estimating the fungal alkaloid content in multiple field environments in order to determine its potential toxicity and value for breeding programs that are aimed at the improvement of turfgrass and forage cultivars.

Impact of endophyte inoculation on the morphological identity of cultivars of Lolium perenne (L) and Festuca arundinacea (Schreb.)

Grass endophytes have been shown to confer enhanced environmental resilience to symbiont cultivars with reports of modified growth. If inoculating with an endophyte (E+) made an accession morphologically distinct from its registered endophyte free (E−) accession, there could be protection and ownership issues for testing authorities and breeders. This study investigated if, in official Plant Breeders Rights (PBR) field trials, the morphological characteristics of E+and E− accessions of perennial ryegrass and tall fescue cultivars were sufficiently modified to designate them as mutually distinct and also distinct from their definitive accessions (Def), held by the testing authorities. Testing perennial ryegrass on 17 characters at 2 sites generated 48,960 observations and for tall fescue on 9 characters at 1 site, 12,960 observations (each for 3 accessions of 4 cultivars × 60 plants × 2 growing cycles). Distinctness required a p < 0.01 difference in a single character from the combined over years analysis (COYD). A few significant differences were recorded between E− and E+accessions. Cultivar Carn E+ was smaller than Carn E− for Infloresence Length (p < 0.01) in both years but COYD analysis (p < 0.05) was insufficient to declare distinctiveness. Overall, the number of observed differences between E−/E+ accessions was less or similar to the number expected purely by chance. In contrast, comparisons between Def and E− or E+ accessions showed a number of significant differences that were substantially more numerous than expected by chance. These results showed no conclusive evidence of endophyte inclusion creating false PBR distinctions but unexpectedly, several E− and E+ accessions were distinguished from their official definitive stock.

Do Epichloë Endophytes and Their Grass Symbiosis Only Produce Toxic Alkaloids to Insects and Livestock?

Epichloë endophytes in forage grasses have attracted widespread attention and interest of chemistry researchers as a result of the various unique chemical structures and interesting biological activities of their secondary metabolites. This review describes the diversity of unique chemical structures of taxa from Epichloë endophytes and grass infected with Epichloë endophytes and demonstrates their reported biological activities. Until now, nearly 160 secondary metabolites (alkaloids, peptides, indole derivatives, pyrimidines, sesquiterpenoids, flavonoids, phenol and phenolic acid derivatives, aliphatic metabolites, sterols, amines and amides, and others) have been reported from Epichloë endophytes and grass infected with Epichloë endophytes. Among these, non-alkaloids account for half of the population of total metabolites, indicating that they also play an important role in Epichloë endophytes and grass infected with Epichloë endophytes. Also, a diverse array of secondary metabolites isolated from Epichloë endophytes and symbionts is a rich source for developing new pesticides and drugs. Bioassays disclose that, in addition to toxic alkaloids, the other metabolites isolated from Epichloë endophytes and symbionts have notable biological activities, such as antifungal, anti-insect, and phytotoxic activities. Accordingly, the biological functions of non-alkaloids should not be neglected in the future investigation of Epichloë endophytes and symbionts.

Effect of Epichloë gansuensis endophyte on rhizosphere bacterial communities and nutrient concentrations and ratios in the perennial grass species Achnatherum inebrians during three growth seasons

Achnatherum inebrians is an invasive perennial grass widespread in natural grasslands of north-west China and plays an important role in grassland ecological restoration. The presence of the seed-borne endophytic fungus Epichloë gansuensis in A. inebrians promotes grass growth, increases resistance to abiotic stress, and affects the rhizosphere microbial community of host plants. However, the relationships among E. gansuensis, rhizosphere bacteria and plant contents of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) during different growing seasons are not clear. We examined changes in the rhizosphere bacterial community and in nutrient contents and ratios in A. inebrians with (E+) and without (E−) E. gansuensis in May, August and December. The Shannon diversity index was higher for rhizosphere bacteria of E+ than E− plants in the three different seasons. Leaf C, N and P contents and root P and K contents were higher in E+ than E− plants in May, and leaf K and root C were higher in E+ than E− plants in August. Leaf C:N ratios were lower in E+ than E− plants in December, and leaf C:K ratios were lower in E+ than E− plants in August and December. In addition, our results indicate significant interactions among rhizosphere bacteria, C, N, P and K contents, and endophyte treatment in three different seasons. In conclusion, E. gansuensis enhanced the C, N, P and K contents of host plants, and affected nutrient ratios of A. inebrians probably by increasing rhizosphere bacterial diversity and altering rhizosphere bacterial community structure. This study provides new findings on the ecological function of the endophyte E. gansuensis, including its potential role in enhancing soil fertility. The improvements in soil fertility were utilised in extrapolating to forage grass–endophyte associations.