Endophyte Symbiosis Research Articles

The Response of the Associations of Grass and Epichloë Endophytes to the Increased Content of Heavy Metals in the Soil.

The rapid development of civilization increases the area of land exposed to the accumulation of toxic compounds, including heavy metals, both in water and soil. Endophytic fungi associated with many species of grasses are related to the resistance of plants to biotic and abiotic stresses, which include heavy metals. This paper reviews different aspects of symbiotic interactions between grass species and fungal endophytes from the genera Epichloë with special attention paid to the elevated concentration of heavy metals in growing substrates. The evidence shows the high resistance variation of plant endophyte symbiosis on the heavy metals in soil outcome. The fungal endophytes confer high heavy metal tolerance, which is the key feature in its practical application with their host plants, i.e., grasses in phytoremediation.

The Response of Stevia (Stevia rebaudiana Bertoni) Photosystem II Photochemistry to Fungi Symbiosis and Spermidine Application under Saline Water Irrigation

Since the medicinal plants mainly are cultivated in marginal areas, are exposed to environmental stresses such as salinity, more than other plants. Salt stress causes damage to photosynthetic process, carbohydrates assimilation and photosystem I and II. However, recently, the role of fungi coexistence and polyamines in plants tolerance to saline conditions are pronounced. Therefore, the present study was conducted to evaluate the effects of endophyte symbiosis and spraying of polyamine spermidine (Spd) on chlorophyll fluorescence parameters of stevia (Stevia rebaudiana Bertoni) medicinal plant under irrigation with saline water. Treatments included non-inoculation (Control) or co-inoculation of Piriformospora indica + Trichoderma virens (Pi + Trich), foliar application of Spd (0 and 0.75) and three salinity levels of Caspian sea water (0, 6 and 12 dS m–1). Seedlings of stevia were transplanted in field conditions and were sprayed with Spd solutions after 9 weeks of planting. Seven days later, the plants were irrigated with three saline treatments for two weeks. The results showed that the foliar application of Spd had a positive effect on Fm, Fv and Fv/Fm and negative effect on Y(NO). Irrigation of plants with saline water had an adverse effect on fluorescence parameters. However, fungi inoculation markedly increased Fm, Fv, Fv/Fm and Y(II) while decreased Fo, Y(NPQ) and Y(NO) in all levels of salt stress. Fungal inoculation and Spd application with 0.75 mM remarkably enhanced Fm. Generally, inoculation of endophytic fungi and Spd spraying improved the chlorophyll fluorescence parameters and adjusted adverse effects of salinity stress in stevia plants.

Z-3-Hexenylacetate emissions induced by the endophyte Epichloë occultans at different levels of defoliation during the host plant's life cycle

Abstract Vertically transmitted fungal endophytes are common defensive symbionts of cool-season grasses. Protection against herbivores has been generally associated with alkaloids produced in the grass-endophyte symbiosis. However, many other changes occur in host metabolism like the release of VOCs. We aimed at characterizing the profile of volatile organic compounds (VOCs) induced by simultaneous fungal endophyte symbiosis and defoliation during the entire life cycle of the annual host grass and the asexual symbiont. We designed an outdoor factorial experiment with plots dominated by intact and damaged Lolium multiflorum plants with high and low infection levels with Epichloe occultans. After exploring the entire VOC profile, the green leaf volatile (Z)-3-hexenyl acetate (Z3-HAC) was found as the main compound emitted by the plants under field conditions. While in low-infected patches there were no differences in volatile emission during the plant life cycle, highly infected patches emitted more Z3-HAC in seedling and vegetative phases than in the reproductive phase. The role of Z3-HAC provided by symbiotic to neighbouring non-symbiotic plants in the associational protection against herbivores and fungal pathogens is discussed.

The symbioses of endophytic fungi shaped the metabolic profiles in grape leaves of different varieties.

Endophytic fungi produce many novel bioactive metabolites that are directly used as drugs or that function as the precursor structures of other chemicals. The metabolic shaping of endophytes on grape cells was reported previously. However, there are no reports on the interactions and metabolic impact of endophyte symbiosis on in vitro vine leaves, which may be examined under well-controlled conditions that are more representative of the natural situation of endophytes within grapevines. The present study used an in vitro leaf method to establish endophyte symbiosis of grapevines and analyze the effects on the metabolic profiles of grape leaves from two different cultivars, ‘Rose honey’ (RH) and ‘Cabernet sauvignon’ (CS). The effects of endophytic fungi on the metabolic profiles of grape leaves exhibited host selectivity and fungal strain specificity. Most of the endophytic fungal strains introduced novel metabolites into the two varieties of grape leaves according to the contents of the detected metabolites and composition of metabolites. Strains RH49 and MDR36, with high or moderate symbiosis rates, triggered an increased response in terms of the detected metabolites, and the strains MDR1 and MDR33 suppressed the detected metabolites in CS and RH leaves despite having strong or moderate symbiosis ability. However, the strain RH12 significantly induced the production of novel metabolites in RH leaves due to its high symbiosis ability and suppression of metabolites in CS leaves.

Maternal Exposure to Ozone Modulates the Endophyte-Conferred Resistance to Aphids in Lolium multiflorum Plants.

Simple SummaryGlobal change is driving the incidence of novel stress factors such as the tropospheric pollutant ozone. Plants can overcome the environmental challenges by adjusting their phenotypes that eventually, can be transmitted to the progeny. Plants also establish symbiotic interactions with beneficial fungal endophytes, some of which can be transmitted to the progeny through the seeds. We worked with the grass Lolium multiflorum and its common endophyte, Epichloë occultans that benefits the host by coffering resistance to herbivores. Specifically, we studied the effect of exposing endophyte-symbiotic and non-symbiotic plants to ozone on the level of resistance to herbivorous aphids in the progeny. The ozone history impaired the endophyte-conferred resistance to aphids in progeny. This was evident at individual weight level of aphids but not so at population level. Defensive compounds were higher in endophyte-symbiotic seeds but depressed by mother plants exposure to ozone. Despite the negative effect of maternal ozone on the resistance level of plants, symbiotic plants showed a superior biomass compared to endophyte-free plants. Our work illustrates how the environment explored by parent plants can persist transgenerationally and, depending on the symbiotic state, will affect the fate of the progeny.Plants are challenged by biotic and abiotic stress factors and the incidence of one can increase or decrease resistance to another. These relations can also occur transgenerationally. For instance, progeny plants whose mothers experienced herbivory can be more resistant to herbivores. Certain fungal endophytes that are vertically transmitted endow plants with alkaloids and resistance to herbivores. However, endophyte-symbiotic plants exposed to the oxidative agent ozone became susceptible to aphids. Here, we explored whether this effect persists transgenerationally. We exposed Lolium multiflorum plants with and without fungal endophyte Epichloë occultans to ozone (120 or 0 ppb), and then, challenged the progeny with aphids (Rhopalosiphum padi). The endophyte was the main factor determining the resistance to aphids, but its importance diminished in plants with ozone history. This negative ozone effect on the endophyte-mediated resistance was apparent on aphid individual weights. Phenolic compounds in seeds were increased by the symbiosis and diminished by the ozone. The endophyte effect on phenolics vanished in progeny plants while the negative ozone effect persisted. Independently of ozone, the symbiosis increased the plant biomass (≈24%). Although ozone can diminish the importance of endophyte symbiosis for plant resistance to herbivores, it would be compensated by host growth stimulation.

The negative effect of a vertically-transmitted fungal endophyte on seed longevity is stronger than that of ozone transgenerational effect

The transition from mother plant seed production to seedlings recruitment is critical for annual plant species but also for vertically transmitted microbial symbionts. Evidence indicates that microbial symbionts play important roles in plant response to environmental changes. However, their role in plant facing gaseous tropospheric pollutants such as the highly reactive and phytotoxic ozone, have been scarcely studied. Here, we experimentally tested the consequences of maternal plant exposure to ozone on the longevity of Lolium mutiflorum seeds mediated by a vertically-transmitted fungal endophyte (Epichloë occultans). Seeds were produced by mother plants exposed to contrasting levels of ozone (low and high concentrations) in two phases of the life cycle (vegetative and reproductive). We first characterized the consequences of plant exposure to ozone on the state of the antioxidant glutathione in the seeds. Then, we examined viability dynamics of the seeds through an accelerated ageing trial and followed the physiological variables seed water content (SWC) and electrical conductivity (EC). Irrespectively of maternal ozone, seeds produced by endophyte-symbiotic plants presented higher contents of the oxidised form of glutathione. In the same direction, the fungal endophyte presence was associated with a dramatic reduction in seed longevity. The SWC was higher in endophyte-symbiotic seeds that in endophyte-free seeds. As time under accelerated ageing condition advanced, EC increased more in endophyte-symbiotic seeds than in endophyte-free seeds. Mother plant exposure to ozone tended to have a negative synergistic effect with the endophyte symbiosis. Ozone transgenerational effect was not detected on endophyte-free seeds. Our work contributes to understand the transgenerational effects of vertically transmitted fungal endophytes in plants in response to a currently important factor of stress.

Endophytic Beauveria bassiana promotes drought tolerance and early flowering in corn.

Beauveria bassiana (Bals.) Vuillemin (B. bassiana) is an entomopathogenic fungus that establishes endophytic symbiosis with plants. In the present study, the effects of B. bassiana strains colonization in growing Zea mays L.(Z. mays), crop production, and drought tolerance were evaluated. Z. mays seeds were inoculated with B. bassiana strains (GHA, PTG4, and PTG6), using 1 × 106 blastospores/mL and methyl cellulose (MC) or cornstarch (CS) as adherents. Colonization was determined by B. bassiana recovery from plant tissues plated on PDA medium. Plant height, fresh and dry weight, and flowering time were analyzed to assess plant performance. Drought tolerance was evaluated by stopping watering for 10days, watering again, and determining vigor recovery after 24h. Results showed 100% endophytic roots colonization, regardless of adherent type or strain tested. Colonization was variable in shoots and leaves, but GHA strain achieved the highest inoculation rates, including 88% in stems and 50% in leaves, which did not depend on adherent type used; for PTG4 strain, adherent type had an important effect (MC = 100% stems and leaves; CS = 63% stems and 25% leaves). For PTG6 strain, the best adherent type was CS (71% stems and 75% leaves), whereas MC showed variable inoculation percentage (25% stems and 75% leaves). Interestingly, only MCPTG4 treatment showed consistent positive effects on germination percentage (day 5 = 46 ± 2%; day 14 = 87 ± 7%) compared with controls (CC = 63 ± 4%, CMC = 50 ± 3%, CCS = 47 ± 0%). In addition, the other treatments showed low germination percentages at day 5 (7 ± 7% to 46 ± 2%), which recovered at day 14 (53 ± 0% to 73 ± 8%), except for MCPTG6 treatment with 23 ± 10% germination. About plant performance, not significant effects on plant height andfresh/dry weight in all the treatments were observed. However, B. bassiana-treated plants, using either GHA, PTG4 or PTG6 strains, and MC as adherent, showed tolerance to drought and flowered one to two weeks earlier, providing evidence supporting further applications of these seed treatments in agricultural systems, for abiotic stress sustainable management practices.

Does Epichloë Endophyte Enhance Host Tolerance to Root Hemiparasite?

Epichloë endophytes have been shown to be mutualistic symbionts of cool-season grasses under most environmental conditions. Although pairwise interactions between hemiparasites and their hosts are heavily affected by host-associated symbiotic microorganisms, little attention has been paid to the effects of microbe-plant interactions, particularly endophytic symbiosis, in studies examining the effects of parasitic plants on host performance. In this study, we performed a greenhouse experiment to examine the effects of hereditary Epichloë endophyte symbiosis on the growth of two host grasses (Stipa purpurea and Elymus tangutorum) in the presence or absence of a facultative root hemiparasite (Pedicularis kansuensis Maxim). We observed parasitism of both hosts by P. kansuensis: when grown with a host plant, the hemiparasite decreased the performance of the host while improving its own biomass and survival rate of the hemiparasite. Parasitized endophyte-infected S. purpurea plants had higher biomass, tillers, root:shoot ratio, and photosynthetic parameters and a lower number of functional haustoria than the endophyte-free S. purpurea conspecifics. By contrast, parasitized endophyte-infected E. tangutorum had a lower biomass, root:shoot ratio, and photosynthetic parameters and a higher number of haustoria and functional haustoria than their endophyte-free counterparts. Our results reveal that the interactions between the endophytes and the host grasses are context dependent and that plant-plant interactions can strongly affect their mutualistic interactions. Endophytes originating from S. purpurea alleviate the host biomass reduction by P. kansuensis and growth depression in the hemiparasite. These findings shed new light on using grass-endophyte symbionts as biocontrol methods for the effective and sustainable management of this weedy hemiparasite.

Chemotaxis of Bacillus cereus YL6 and its colonization of Chinese cabbage seedlings

Phosphorus-solubilizing bacteria can colonize the surface of plant roots under natural conditions and may enter plant tissues to form endophytic symbiosis. They can convert unavailable phosphorus in the soil into available phosphorus, which can be utilized by plants. The aims of this study were to investigate the chemotaxis of Bacillus cereus YL6 and its migration and colonization sites in Chinese cabbage and to provide some technical support for the subsequent investigation of the physiological regulation mechanism of phosphate-dissolving bacteria in plants. This study demonstrated that the green fluorescent protein marker did not affect the physiological and biochemical properties of YL6. Through the chemotaxis test and pot experiment, the colonization and growth promoting mechanism of YL6 in Chinese cabbage was explored. YL6 showed a strong positive chemotactic response to cabbage roots. The addition of organic acids to the soil promotes the colonization of YL6 in Chinese cabbage roots. Colonization of YL6 in Chinese cabbage is a dynamic process that moves from the root surface to root tissues and then up to stems and leaves. Fluorescence microscopy showed that YL6 mainly colonized cortical cells and vascular bundles of various plant tissues and was also observed in mesophyll cells. The proliferative effect of YL6 resulted from the interaction of effective phosphorus, and exuded auxin and gibberellin in the rhizosheath. This study enhanced our understanding of the interaction mechanisms between phosphate-dissolving bacteria YL6 and Chinese cabbage. YL6 has the potential for future development into bio-fertilizer for agricultural production.

Greater genetic and regulatory plasticity of retained duplicates in Epichloë endophytic fungi.

Gene duplicates can act as a source of genetic material from which new functions arise. Most duplicated genes revert to single copy genes and only a small proportion are retained. However, it remains unclear why some duplicate genes persist in the genome for an extended time. We investigate this question by analysing retained gene duplicates in the fungal genus Epichloë, ascomycete fungi that form close endophytic symbioses with their host grasses. Retained duplicates within this genus have two independent origins, but both long pre‐date the origin and diversification of the genus Epichloë. We find that loss of retained duplicates within the genus is frequent and often associated with speciation. Retained duplicates have faster evolutionary rates (Ka) and show relaxed selection (Ka/Ks) compared to single copy genes. Both features are time‐dependent. Through comparison of conspecific strains, we find greater evolutionary rates in coding regions and sequence divergence in regulatory regions of retained duplicates than single copy genes, with this pattern more pronounced for strains adapted to different grass host species. Consistent with this sequence divergence in regulatory regions, transcriptome analyses show greater expression variation of retained duplicates than single copy genes. This suggest that cis‐regulatory changes make important contributions to the expression patterns of retained duplicates. Coupled with supporting observations from the model yeast Saccharomyces cerevisiae, these data suggest that genetic robustness and regulatory plasticity are common drivers behind the retention of duplicated genes in fungi.

Host Genotype and Precipitation Influence of Fungal Endophyte Symbiosis and Mycotoxin Abundance in a Locoweed.

Many plant endophytes produce mycotoxins, but how host genetic variation influences endophyte colonization and mycotoxin production under natural conditions is poorly understood. This interaction has not been fully considered in many previous studies which used controlled experiments with agronomic or model plant species. Here, we investigated this interaction in a naturally occurring forb (a locoweed species) Oxytropis ochrocephala, its symbiotic endophyte Alternaria oxytropis, and the mycotoxin swainsonine. Host genetic variation was characterized by microsatellite markers. Endophyte infection rate and swainsonine levels were determined by PCR and HPLC, respectively. Genetic markers defined two distinct host populations and revealed that host genetics were significantly correlated with geographical location, elevation, and precipitation. As the host diverged, symbiotic interactions were reduced or failed to produce detectable swainsonine in one host population. Host genotype and precipitation had a significant impact in shaping swainsonine production at the population level. This study highlights the effect of host genotype in influencing this interaction in locoweeds.

Physiological consequences of gamma ray irradiation in tall fescue with elimination potential of Epichloë fungal endophyte

Perennial plants and their associated microorganisms grow in the areas that may be contaminated with long-lived gamma-emitting radionuclides. This will induce gamma stress response in plants and their accompanying microorganisms. The present work investigated the growth and physiological responses of Epichloe endophyte infected tall fescue to gamma radiation, as well as whether the endophyte could persist and infect the host plant once exposed to gamma radiation. Seeds of Iranian native genotype of 75B+ of tall fescue were exposed to different doses, including 5.0, 10.0, 15.0, 20.0, 30.0 and 40.0 krad of gamma ray from a 60Co source. Irradiated and unirradiated seeds were sown in pots and grown under controlled conditions in the greenhouse. The growth and physiological parameters associated with plant tolerance to oxidative stress of host plants, as well as endophytic infection frequency (% of plants infected) and intensity (mean number of endophytic hyphae per the field of view), were examined in 3 months-old seedlings. The results indicated that all gamma radiation doses (except 5.0 kr) significantly reduced the height and survival percentage of the host plant. Days to the emergence of seedling increased gradually as gamma doses rose. A dose-rate dependent induction was seen for photosynthetic pigments and proline content. Malondialdehyde (MDA) content grew with elevation of irradiation doses. Depending on the dose and time, the activities of antioxidant enzymes in the host plant responded differently to gamma radiation. Gamma radiation altered the enzyme activities with sever decline in SOD and CAT activities. However, it had barely any effect on in APX and POD activities. The results also revealed that the persistence and intensity of endophyte were affected after gamma-ray irradiation. The initial percentage of tall fescue seeds infected with the endophyte was 91% in un-irradiated seeds. Presence of the viable endophyte started to decline significantly (23%) at 5.0 kr of gamma radiation. A dramatic reduction in the presence and intensity of endophyte occurred at 10.0 to 40.0 kr intensities. Gamma radiation × trait (GT)-biplot analysis indicated positive correlations between the endophyte symbiosis and antioxidant enzyme activities. Also, negative correlations were observed between the endophyte and MDA content in the host plant. Our results suggest that radiation stress (doses over 5.0 kr) caused reduction in the growth and antioxidant enzyme activities of the host plant that accompanied by a dramatic reduction in the persistence and intensity of endophyte fungi. Our findings have provided the basic information for future studies on the effect of gamma irradiation on the interaction between endophytic fungi and its host plant.

Contemporaneous radiations of fungi and plants linked to symbiosis

Interactions between fungi and plants, including parasitism, mutualism, and saprotrophy, have been invoked as key to their respective macroevolutionary success. Here we evaluate the origins of plant-fungal symbioses and saprotrophy using a time-calibrated phylogenetic framework that reveals linked and drastic shifts in diversification rates of each kingdom. Fungal colonization of land was associated with at least two origins of terrestrial green algae and preceded embryophytes (as evidenced by losses of fungal flagellum, ca. 720 Ma), likely facilitating terrestriality through endomycorrhizal and possibly endophytic symbioses. The largest radiation of fungi (Leotiomyceta), the origin of arbuscular mycorrhizae, and the diversification of extant embryophytes occurred ca. 480 Ma. This was followed by the origin of extant lichens. Saprotrophic mushrooms diversified in the Late Paleozoic as forests of seed plants started to dominate the landscape. The subsequent diversification and explosive radiation of Agaricomycetes, and eventually of ectomycorrhizal mushrooms, were associated with the evolution of Pinaceae in the Mesozoic, and establishment of angiosperm-dominated biomes in the Cretaceous.

Leaf endophytes mediate fertilizer effects on plant yield and traits in northern oat grass (Trisetum spicatum)

Symbiotic fungi commonly increase plant acquisition of soil nutrients. Because prior work has focused on root fungi, we examined how leaf endophytes (Epichloe) influenced plant responses to fertilization and altered plant traits that may cascade to food webs and ecosystem processes. We manipulated endophyte presence/absence in two populations of Trisetum spicatum, a wild relative of oat, under a 2 × 2 addition of soil nitrogen (N) and phosphorus (P) in the greenhouse. Endophyte symbiosis altered how plant biomass responded to soil N and how plant traits responded to soil P. Endophytes boosted the biomass gains from N-fertilization in one population. Plants from a second population had weak benefits of symbiosis, but the endophyte altered plant traits, by increasing specific leaf area under P-fertilization, root diameter under low P, and concentration of the fungal alkaloid AcAP under N fertilization. Endophyte presence suppressed the typically observed increase in root hair density in response to soil P limitation. Under low P, symbiotic plants from both populations had improved forage quality relative to symbiont-free plants, although N-fertilization had a larger effect size on forage quality than did symbiosis. Finally, the two populations differed in production of fungal alkaloids, which generally increased in response to fertilization. Predicting how microbial symbionts mediate plant acquisition of nutrients requires understanding how much their effects vary among plant and endophyte genotypes. Here, the magnitude and direction of leaf symbionts’ effects on plant yield and traits varied between populations and with soil nutrient availability.

Asexual Epichloë Endophytes Do Not Consistently Alter Arbuscular Mycorrhizal Fungi Colonization in Three Grasses

Abstract Plants commonly host multiple microbial symbionts that regulate productivity and other ecosystem processes, yet multi-symbiont interactions within hosts are rarely examined. We evaluated how the presence of aboveground Epichloe fungal endophytes (E+, symbiotic, and E−, endophyte experimentally removed) altered belowground colonization by arbuscular mycorrhizal fungi (AMF) in three grass species in a common environment. We sampled from E+ and E− populations of woodland bluegrass (Poa sylvestris A. Gray), grove bluegrass (Poa alsodes A. Gray), and tall fescue (Schedonorus arundinaceus Schreb.) in long-term experimental plots in woodlands near Nashville, Indiana. Endophyte symbiosis aboveground increased AMF colonization of roots in both Poa species, although this effect was only significant for hyphal colonization in P. sylvestris. Endophyte symbiosis did not significantly alter AMF colonization in S. arundinaceus, in contrast to prior findings for this species. Our results illustrate the effects o...

The Global Regulatory Protein VelA Is Required for Symbiosis Between the Endophytic Fungus Epichloë festucae and Lolium perenne.

Epichloë species fungi form bioprotective endophytic symbioses with many cool-season grasses, including agriculturally important forage grasses. Despite its importance, relatively little is known about the molecular details of the interaction and the regulatory genes involved. The conserved velvet-domain protein VelA (or VeA) is a global regulator of a number of cellular and developmental functions in fungi. In this study, the E. festucae velA gene was functionally characterized in vitro and during interaction with perennial ryegrass. The velA gene is required in E. festucae for resistance to osmotic and cell wall-damaging stresses, repression of conidiation, and normal hyphal morphology during nutrient-limited in-vitro conditions. Expression of velA in E. festucae is light- and nitrogen-dependent and is tissue-specific in mature infected plants. In-planta studies showed that velA is required in E. festucae for a compatible interaction. Inoculating seedlings with mutant ΔvelA induced callose deposition and H2O2 production, and a high level of seedling death was observed. In surviving plants infected with ΔvelA mutant fungi, plants were stunted and we observed increased biomass and invasion of vascular bundles. Overall, this work characterizes a key fungal regulatory factor in this increasingly important model symbiotic association.

Vertically transmitted symbionts as mechanisms of transgenerational effects.

A transgenerational effect occurs when a biotic or abiotic environmental factor acts on a parental individual and thereby affects the phenotype of progeny. Due to the importance of transgenerational effects for understanding plant ecology and evolution, their underlying mechanisms are of general interest. Here, we introduce the concept that inherited symbiotic microorganisms could act as mechanisms of transgenerational effects in plants. We define the criteria required to demonstrate that transgenerational effects are microbially mediated and review evidence from the well-studied, vertically transmitted plant-fungal symbiosis (grass-Epichloë spp.) in support of such effects. We also propose a basic experimental design to test for the presence of adaptive transgenerational effects mediated by plant symbionts. An increasingly large body of literature shows that vertically transmitted microorganisms are common in plants, with potential to affect the phenotypes and fitness of progeny. Transgenerational effects could occur via parental modification of symbiont presence/absence, symbiont load, symbiont products, symbiont genotype or species composition, or symbiont priming. Several of these mechanisms appear likely in the grass-Epichloë endophytic symbiosis, as there is variation in the proportion of the progeny that carries the fungus, as well as variation in concentrations of mycelia and secondary compounds (alkaloids and osmolytes) in the seed. Symbiont-mediated transgenerational effects could be common in plants and could play large roles in plant adaptation to changing environments, but definitive tests are needed. We hope our contribution will spark new lines of research on the transgenerational effects of vertically transmitted symbionts in plants.

Does a foliar endophyte improve plant fitness under flooding?

Although endophytic fungi are ubiquitous in plants, their full range of ecological effects has yet to be characterized, particularly in non-agronomic systems. In this study, we compared the responses of two congeneric bluegrass species to flooding. Both plant species co-occur in subalpine zones of the Rocky Mountains. Marsh bluegrass (Poa leptocoma) commonly hosts a vertically transmitted fungal endophyte (Epichloe sp.) and naturally grows in wetter conditions than does nodding bluegrass (Poa reflexa), which lacks an epichloid endophyte. We investigated the novel hypothesis that endophyte symbiosis promotes host fitness under flooded conditions, contributing to niche differentiation between the two bluegrass species. We used a factorial greenhouse experiment to test whether endophyte presence improved survival, growth, or reproduction of P. leptocoma under flooded versus non-flooded edaphic conditions by experimentally removing the endophyte from half of the plants. We compared P. leptocoma responses to those of the endophyte-free congener. In contrast to expectations generated from the natural distributions of the two plant species, endophyte presence was more beneficial to P. leptocoma under ambient soil moisture than under flooding. Increased benefits of symbiosis in drier soils are consistent with studies of other grass endophytes. Flooded soils also unexpectedly improved the growth of P. reflexa more than that of the wet habitat specialist, P. leptocoma. While our results demonstrate an overall benefit of fungal symbiosis in this system, ecological factors other than flooding per se likely underlie the observed geographical distributions of these congeneric grasses in nature.

Additive effects due to biochar and endophyte application enable soybean to enhance nutrient uptake and modulate nutritional parameters.

We studied the effects of hardwood-derived biochar (BC) and the phytohormone-producing endophyte Galactomyces geotrichum WLL1 in soybean (Glycine max (L.) Merr.) with respect to basic, macro- and micronutrient uptakes and assimilations, and their subsequent effects on the regulation of functional amino acids, isoflavones, fatty acid composition, total sugar contents, total phenolic contents, and 1,1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging activity. The assimilation of basic nutrients such as nitrogen was up-regulated, leaving carbon, oxygen, and hydrogen unaffected in BC+G. geotrichum-treated soybean plants. In comparison, the uptakes of macro- and micronutrients fluctuated in the individual or co-application of BC and G. geotrichum in soybean plant organs and rhizospheric substrate. Moreover, the same attribute was recorded for the regulation of functional amino acids, isoflavones, fatty acid composition, total sugar contents, total phenolic contents, and DPPH-scavenging activity. Collectively, these results showed that BC+G. geotrichum-treated soybean yielded better results than did the plants treated with individual applications. It was concluded that BC is an additional nutriment source and that the G. geotrichum acts as a plant biostimulating source and the effects of both are additive towards plant growth promotion. Strategies involving the incorporation of BC and endophytic symbiosis may help achieve eco-friendly agricultural production, thus reducing the excessive use of chemical agents.

二种交配型球孢白僵菌对亚洲玉米螟的生态控制作用

PDF HTML阅读 XML下载 导出引用 引用提醒 二种交配型球孢白僵菌对亚洲玉米螟的生态控制作用 DOI: 10.5846/stxb201508081673 作者: 作者单位: 哈尔滨师范大学,吉林省农业科学院植物保护研究所/农业部东北作物有害生物综合治理重点实验室/吉林省农业微生物重点实验室,吉林省农业科学院植物保护研究所/农业部东北作物有害生物综合治理重点实验室/吉林省农业微生物重点实验室,吉林省农业科学院植物保护研究所/农业部东北作物有害生物综合治理重点实验室/吉林省农业微生物重点实验室,吉林省农业科学院植物保护研究所/农业部东北作物有害生物综合治理重点实验室/吉林省农业微生物重点实验室,东北师范大学草地科学研究所,哈尔滨师范大学生命科学与技术学院,吉林省农业科学院/农业部东北作物有害生物综合治理重点实验室/吉林省农业微生物重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 黑龙江自然科学基金项目（C201307）；吉林省科技厅重大科技攻关项目（20140203006NY） Ecological control of the Asian corn borer, Ostrinia furnacalis (Guenée) by two cloned Beauveria bassiana strains Author: Affiliation: Harbin Normal University,,,,,,,Jilin Academy of Agricultural Sciences/Key Laboratory of Integrated Pest Management on Crops in Northeastern China, Ministry of Agriculture/Jilin Key Laboratory of Agricultural Microbiology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用生物种间互做关系抑制农业害虫的暴发是生物防治的重要手段。为探讨二种交配型内共生球孢白僵菌与玉米之间的互惠关系及其形成的共生体在亚洲玉米螟控制中的生态效应，以玉米为宿主植物，以球孢白僵菌孢子悬浮液进行灌根，在温室内构建了二种交配型（MAT1-1-1型，B5；MAT1-2-1型，B2）球孢白僵菌-玉米共生体，并研究了共生体对玉米的生长、对亚洲玉米螟的产卵选择和幼虫发育及其对球孢白僵菌生物学特性的影响。结果显示：通过叶片离体培养、ITS基因和交配型基因MAT检测，均能检测到白僵菌的内生定殖；MAT1-2-1型B2菌株定殖检出率高，MAT1-1-1型B5菌株在混合型接种中定殖有优势。回收后的球孢白僵菌菌落直径和毒力无显著性变化，但其产孢量都显著提高其中回收B5处理组来源菌株的产孢量提高最显著。接种过球孢白僵菌的玉米植株地上部生长速度、生物量和地下根系生物量均优于对照组，其中根系干重明显增加，而地上植株干重也相对增加。MAT1-1-1型菌株B5对共生体玉米植株地上高度促生长贡献明显；MAT1-2-1型菌株B2对共生体玉米植株地下干重增加贡献明显。总体上球孢白僵菌内生定殖对玉米地下根系生物量影响大于对地上植株生物量的影响。在产卵选择性试验中，各处理组亚洲玉米螟的产卵量显著少于对照组。共生体对亚洲玉米螟产卵具有明显的趋避作用，MAT1-2-1型菌株B2对产卵的趋避作用明显，而MAT1-2-1型菌株B5的趋避作用较弱。在人工接种幼虫的试验中，处理组回收的亚洲玉米螟幼虫存活率均显著低于对照组，其中，B5组回收幼虫的存活率最低，仅为38.33%；处理组的化蛹率与对照组差异不显著，但B5组的回收幼虫化蛹率显著低于B2组和对照组，仅为34.77%，这说明MAT1-1-1型B5菌株对玉米螟幼虫发育抑制最明显。上述结果表明，不同交配型球孢白僵菌内生定殖效率有差异，在经过内生定殖后在产孢量方面有显著性提高，两个交配型菌株在联合应用时具有协同增效作用；两个交配型菌株均能够通过内生定殖与玉米形成共生体并促进玉米植株的生长，这显示球孢白僵菌和玉米之间已经建立具有互惠关系的共生体。这种共生体通过趋避亚洲玉米螟产卵、抑制幼虫存活和降低化蛹率等方面的潜力虽然不一样，但都有助于对亚洲玉米螟的可持续生态防治，也证明了共生体的建成有效提高了玉米的生态适应性，为利用球孢白僵菌内共生性实施亚洲玉米螟防控提供了新思路。 Abstract:Ecological control methods are important for controlling agricultural pests. The Asian corn borer (ACB), Ostrinia furnacalis (Guenée), has been an extremely serious pest, that cause severe reduction in corn yields. The ubiquitous entomopathogenic fungus Beauveria bassiana has been used to suppress populations of the European corn borer (ECB), O. nubilalis, and ACB globally. Most studies have focused on the application of B. bassiana, with limited studies on the relationship between the fungus, corn, and insects. Our previous research indicated that B. bassiana with two mating-gene types, MAT1-1-1 and MAT1-2-1, could colonize corn. These mating-type genes had mutation sites cloned from endophytic fungal strains, which revealed corn plants and insects could impact fungal evolution. The purpose of the present study was to create endophytic symbiosis and determine the interaction among B. bassiana (entophytic fungus), corn plants, and ACB. We created a B. bassiana-corn endophytic symbiosis by inoculating two mating-gene type B. bassiana strains (MAT1-1-1 type B5 and MAT1-2-1 type B2) into corn plants in a suspension with a concentration of 1×107 spores/mL. The effect of endophytic symbiosis on the growth of corn plants, oviposition preference of ACB adults, development of ACB larvae, and biological variation of B. bassiana were evaluated in the greenhouse. The results showed that endophytic B. bassiana could be detected from corn leaves in vitro by culture. ITS and mating-type gene amplification and sequencing confirmed the successful creation of endophytic symbiosis. The MAT1-2-1 type B2 treatment group showed a higher endophytic detection rate than MAT1-1-1 type B5, whereas MAT1-1-1 type B5 was more successful during co-inoculation than MAT1-2-1 type B2. The variation of the colony diameter and virulence of the recovered B. bassiana were not significant, but the sporulation quantity improved significantly, and the EN-B5 strain (recovered from the B5 treatment) changed the most obviously. The height of corn plants and dried biomass of treatment groups were higher than the CK group, while the underground root biomass significantly improved. The B5 strain contributed more to above-ground plant height and the B2 strain contributed more to underground root biomass. ACB moths were released into nylon-meshed cages. Egg quantity showed a significant difference in all treatment groups, which was lower than that in the CK group. Egg fecundity rate in the B2 group was 3.33%, but 53.33% in the CK group; therefore, the B2-corn endophytic symbiosis group was not the preferred host for ACB egg laying. The ACB larval survival rate and weight in treatment groups were significantly lower than those in the CK group. The ACB pupation rate of treatment groups was not significantly lower than that of the CK group, but there was a significant difference between B5 and B2 groups; the B5 group had the lowest survival (38.33%) and pupation rates (34.77%). These results demonstrated that the sporulation quantity of the recovered B. bassiana strains significantly improved, and the synergism of the two strains with different mating-type genes was shown. The two B. bassiana mating-types could colonize in corn plants and mutualistic endophytic symbiosis was formed, which reinforced corn growth and improved the resistance against pests. B. bassiana-corn endophytic symbiosis is important for the sustainable management of pests by inhibiting oviposition and suppressing larval and pupal development. The results also proved that mutualistic symbiosis could improve the ecological adaptability of B. bassiana and corn, which offered a new strategy for ACB control using endophytic symbiosis through the application of B. bassiana. 参考文献 相似文献 引证文献