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Kari Saikkonen - One of the best experts on this subject based on the ideXlab platform.
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geographic variation in festuca rubra l ploidy levels and systemic fungal endophyte frequencies
PLOS ONE, 2016Co-Authors: Serdar Dirihan, Pedro E. Gundel, Lucas A Garibaldi, Marjo Helander, Henry Vare, Gonzalo J N Irisarri, Irma Saloniemi, Kari SaikkonenAbstract:Polyploidy and symbiotic Epichloe fungal Endophytes are common and heritable characteristics that can facilitate environmental range expansion in grasses. Here we examined geographic patterns of polyploidy and the frequency of fungal endophyte colonized plants in 29 Festuca rubra L. populations from eight geographic sites across latitudes from Spain to northernmost Finland and Greenland. Ploidy seemed to be positively and negatively correlated with latitude and productivity, respectively. However, the correlations were nonlinear; 84% of the plants were hexaploids (2n = 6x = 42), and the positive correlation between ploidy level and latitude is the result of only four populations skewing the data. In the southernmost end of the gradient 86% of the plants were tetraploids (2n = 4x = 28), whereas in the northernmost end of the gradient one population had only octoploid plants (2n = 8x = 56). Endophytes were detected in 22 out of the 29 populations. Endophyte frequencies varied among geographic sites, and populations and habitats within geographic sites irrespective of ploidy, latitude or productivity. The highest overall endophyte frequencies were found in the southernmost end of the gradient, Spain, where 69% of plants harbored Endophytes. In northern Finland, Endophytes were detected in 30% of grasses but endophyte frequencies varied among populations from 0% to 75%, being higher in meadows compared to riverbanks. The Endophytes were detected in 36%, 30% and 27% of the plants in Faroe Islands, Iceland and Switzerland, respectively. Practically all examined plants collected from southern Finland and Greenland were endophyte-free, whereas in other geographic sites endophyte frequencies were highly variable among populations. Common to all populations with high endophyte frequencies is heavy vertebrate grazing. We propose that the detected endophyte frequencies and ploidy levels mirror past distribution history of F. rubra after the last glaciation period, and local adaptations to past or prevailing selection forces such as vertebrate grazing.
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fungal endophyte mediated occurrence of seminiferous and pseudoviviparous panicles in festuca rubra
Fungal Diversity, 2014Co-Authors: Pedro E. Gundel, Piippa R Wali, Lucas A Garibaldi, Marjo Helander, Serdar Dirihan, Kari SaikkonenAbstract:Fungal Endophytes are suggested to manipulate host grass reproduction. Using different grass-endophyte combinations in a four year common garden experiment, we show that endophyte can retain control over the reproductive functions of the host. Plants were collected as seeds from two different environments, meadows and riverbanks. Natural endophyte infection (E+) increased reproductive effort of plants; 13 and 15 % higher proportion of E+ plants produced panicles compared to naturally uninfected (E-) and manipulatively endophyte-infected (ME+) plants, respectively. Meadow-origin E+ plants produced also higher number of panicles compared to E- in the last two years, and both meadow- and riverbank-origin ME+ plants produced higher number of panicles compared to ME- plants in most of the years. Pseudovivipary was recorded in 5 % of the plants each year. Pollen limitation appears not to induce pseudovivipary. Both E+ and ME+ plants produced higher number of seminiferous panicles compared to E- and ME- plants. The higher proportion of pseudoviviparism in ME+ plants compared to E+, E- and ME- plants from meadows suggests specific genotype-genotype cross-talk between endophyte and grass. Pseudovivipary was affected by year and primarily explained by plant reproductive effort since most vigorous plants produced more pseudoviviparous panicles. We propose that Endophytes can promote host grass reproduction in a habitat-specific manner and depending on genetic compatibility between partners. However, reproductive behavior depended on maternal habitat and the annual environmental conditions highlighting the importance of long-term experiments to estimate the effects of Endophytes on host plant ecology.
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Chemical Ecology Mediated by Fungal Endophytes in Grasses
Journal of Chemical Ecology, 2013Co-Authors: Kari Saikkonen, Pedro E. Gundel, Marjo HelanderAbstract:Defensive mutualism is widely accepted as providing the best framework for understanding how seed-transmitted, alkaloid producing fungal Endophytes of grasses are maintained in many host populations. Here, we first briefly review current knowledge of bioactive alkaloids produced by systemic grass-Endophytes. New findings suggest that chemotypic diversity of the endophyte-grass symbiotum is far more complex, involving multifaceted signaling and chemical cross-talk between endophyte and host cells ( e.g. , reactive oxygen species and antioxidants) or between plants, herbivores, and their natural enemies ( e.g. , volatile organic compounds, and salicylic acid and jasmonic acid pathways). Accumulating evidence also suggests that the tight relationship between the systemic endophyte and the host grass can lead to the loss of grass traits when the lost functions, such as plant defense to herbivores, are compensated for by an interactive endophytic fungal partner. Furthermore, chemotypic diversity of a symbiotum appears to depend on the endophyte and the host plant life histories, as well as on fungal and plant genotypes, abiotic and biotic environmental conditions, and their interactions. Thus, joint approaches of (bio)chemists, molecular biologists, plant physiologists, evolutionary biologists, and ecologists are urgently needed to fully understand the endophyte-grass symbiosis, its coevolutionary history, and ecological importance. We propose that endophyte-grass symbiosis provides an excellent model to study microbially mediated multirophic interactions from molecular mechanisms to ecology.
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Symbiotic interactions as drivers of trade-offs in plants: effects of fungal Endophytes on tall fescue
Fungal Diversity, 2013Co-Authors: Pedro E. Gundel, Lucas A Garibaldi, Marjo Helander, Kari SaikkonenAbstract:Studying the controls on biomass allocation trade-offs in plants are important since they affect harvestable product yields and are critical to understanding symbiotic interactions. Epichloae fungal Endophytes associate with cool-season grasses, growing systemically within the plant inter-cellular spaces and are transmitted through seeds. We explore the Endophytes influence on the relationship between the plant reproductive and vegetative aboveground biomass (reproductive effort: RE) and on the trade-off between two components of the reproductive biomass, number and weight of panicles (RPN), using tall fescue as a model system. Naturally endophyte-colonized, manipulatively endophyte-free, and naturally endophyte-free plants from Northern European wild-populations together with the cultivar Kentucky-31 were grown under different environmental conditions (nutrients x water). The endophyte had an effect on the RPN (E+: 6.19, ME-: 4.68 and E-: 4.40) which indicates how reproductive biomass is partitioned into number and mass of panicles, but not on RE (≈0.06). As expected, wild plants showed higher reproductive effort (≈0.06) compared to the cultivar KY-31 (0.05), irrespective of endophyte presence. Endophyte-colonized plants had lighter panicles than endophyte-free plants, a pattern that was clear among low-yielding plants. Similarly, the trade-off between RPN and RE was higher for endophyte-colonized plants. This was again evident among plants with low RE indicating that colonized plants split the yield into either greater number of panicles and/or lighter panicles. The effect of vertically transmitted Endophytes has earlier been studied as ratios (e.g. RE); however, our study shows that this approach may hide size-dependent endophyte effects on these relationships. Our study reveals that Neotyphodium endophyte affects trade-offs in tall fescue plants in a complex manner, and is influenced by a number of biological and abiotic factors.
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Defensive mutualism between plants and endophytic fungi?
Fungal Diversity, 2010Co-Authors: Kari Saikkonen, S. Saari, Marjo HelanderAbstract:Endophyte-grass symbiosis is generally considered to be a classic example of microbe-plant symbiosis in which the fitness of the microbial symbiont and its host plant is closely linked, and thus, presumed to align the interests of partners toward mutually beneficial cooperation. Accumulating evidence seems to suggest that defensive mutualism provides the best framework for understanding plant-endophyte interactions in general. We conducted a meta-analysis of 99 published studies on 36 plant (inc. both grass and tree species), 62 herbivore and 17 predator or parasitoid taxons to test the importance of defensive mutualism in multitrophic interactions. In general, statistical perusal revealed that we still know little about these seemingly well-studied biological interactions. The conceptual framework for endophyte-grass interactions has largely been based on endophyte-plant-herbivore studies of two, economically important, artificially selected and introduced agricultural grass species, tall fescue and perennial ryegrass, and two generalist invertebrate pests. Only 10 original publications provided data of higher trophic levels. Consistent with the defensive mutualism hypothesis, the meta-analysis indicates that Endophytes slightly increase grass resistance to herbivores, and the defensive mutualism appears to be most commonly detected in systemic and vertically transmitted grass Endophytes compared to horizontally transmitted tree Endophytes. However, variation appears to increase when higher trophic levels are considered. In addition to taxonomical bias, the literature is strongly biased toward short-term laboratory and greenhouse experiments rather than field conditions. Thus, current literature is insufficient to capture the breadth of variability inherent in the wild grass-endophyte populations and communities, and the general importance of defensive mutualism remains to be solved in future studies.
Elizabeth A Arnold - One of the best experts on this subject based on the ideXlab platform.
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endohyphal bacterium enhances production of indole 3 acetic acid by a foliar fungal endophyte
PLOS ONE, 2013Co-Authors: Michele T Hoffman, Malkanthi K Gunatilaka, Kithsiri Wijeratne, Leslie Gunatilaka, Elizabeth A ArnoldAbstract:Numerous plant pathogens, rhizosphere symbionts, and endophytic bacteria and yeasts produce the important phytohormone indole-3-acetic acid (IAA), often with profound effects on host plants. However, to date IAA production has not been documented among foliar Endophytes -- the diverse guild of primarily filamentous Ascomycota that live within healthy, above-ground tissues of all plant species studied thus far. Recently bacteria that live within hyphae of Endophytes (endohyphal bacteria) have been detected, but their effects have not been studied previously. Here we show not only that IAA is produced in vitro by a foliar endophyte (here identified as Pestalotiopsis aff. neglecta, Xylariales), but that IAA production is enhanced significantly when the endophyte hosts an endohyphal bacterium (here identified as Luteibacter sp., Xanthomonadales). Both the endophyte and the endophyte/bacterium complex appear to rely on an L-tryptophan dependent pathway for IAA synthesis. The bacterium can be isolated from the fungus when the symbiotic complex is cultivated at 36°C. In pure culture the bacterium does not produce IAA. Culture filtrate from the endophyte-bacterium complex significantly enhances growth of tomato in vitro relative to controls and to filtrate from the endophyte alone. Together these results speak to a facultative symbiosis between an endophyte and endohyphal bacterium that strongly influences IAA production, providing a new framework in which to explore endophyte-plant interactions.
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geographic locality and host identity shape fungal endophyte communities in cupressaceous trees
Fungal Biology, 2008Co-Authors: Michele T Hoffman, Elizabeth A ArnoldAbstract:Abstract Understanding how fungal endophyte communities differ in abundance, diversity, taxonomic composition, and host affinity over the geographic ranges of their hosts is key to understanding the ecology and evolutionary context of endophyte–plant associations. We examined Endophytes associated with healthy photosynthetic tissues of three closely related tree species in the Cupressaceae ( Coniferales ): two native species within their natural ranges [ Juniperus virginiana in a mesic semideciduous forest, North Carolina (NC); Cupressus arizonica , under xeric conditions, Arizona (AZ)], and a non-native species planted in each site ( Platycladus orientalis ). Endophytes were recovered from 229 of 960 tissue segments and represented at least 35 species of Ascomycota . Isolation frequency was more than threefold greater for plants in NC than in AZ, and was 2.5 (AZ) to four (NC) times greater for non-native Platycladus than for Cupressus or Juniperus . Analyses of ITS rDNA for 109 representative isolates showed that endophyte diversity was more than twofold greater in NC than in AZ, and that Endophytes recovered in AZ were more likely to be host-generalists relative to those in NC. Different endophyte genera dominated the assemblages of each host species/locality combination, but in both localities, Platycladus harboured less diverse and more cosmopolitan Endophytes than did either native host. Parsimony and Bayesian analyses for four classes of Ascomycota ( Dothideomycetes , Sordariomycetes , Pezizomycetes , Eurotiomycetes ) based on LSU rDNA data ( ca 1.2 kb) showed that well-supported clades of Endophytes frequently contained representatives of a single locality or host species, underscoring the importance of both geography and host identity in shaping a given plant's endophyte community. Together, our data show that not only do the abundance, diversity, and taxonomic composition of endophyte communities differ as a function of host identity and locality, but that host affinities of those communities are variable as well.
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diversity and host range of foliar fungal Endophytes are tropical leaves biodiversity hotspots
Ecology, 2007Co-Authors: Elizabeth A Arnold, Francois LutzoniAbstract:Fungal Endophytes are found in asymptomatic photosynthetic tissues of all major lineages of land plants. The ubiquity of these cryptic symbionts is clear, but the scale of their diversity, host range, and geographic distributions are unknown. To explore the putative hyperdiversity of tropical leaf Endophytes, we compared endophyte communities along a broad latitudinal gradient from the Canadian arctic to the lowland tropical forest of central Panama. Here, we use molecular sequence data from 1403 endophyte strains to show that Endophytes increase in incidence, diversity, and host breadth from arctic to tropical sites. Endophyte communities from higher latitudes are characterized by relatively few species from many different classes of Ascomycota, whereas tropical endophyte assemblages are dominated by a small number of classes with a very large number of endophytic species. The most easily cultivated Endophytes from tropical plants have wide host ranges, but communities are dominated by a large number of rare species whose host range is unclear. Even when only the most easily cultured species are considered, leaves of tropical trees represent hotspots of fungal species diversity, containing numerous species not yet recovered from other biomes. The challenge remains to recover and identify those elusive and rarely cultured taxa with narrower host ranges, and to elucidate the ecological roles of these little-known symbionts in tropical forests.
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canopy cover and leaf age affect colonization by tropical fungal Endophytes ecological pattern and process in theobroma cacao malvaceae
Mycologia, 2003Co-Authors: Elizabeth A Arnold, Edward Allen HerreAbstract:Fungal Endophytes inhabit healthy tissues of all terrestrial plant taxa studied to date and are diverse and abundant in leaves of tropical woody an- giosperms. Studies have demonstrated that plant lo- cation and leaf age influence density of endophyte infection in leaves of tropical forest trees. However, ecological factors underlying these observations have not been explored in detail. Here, we establish that foliar Endophytes of a tropical tree (Theobroma cacao, Malvaceae) are transmitted horizontally and that en- dophyte-free seedlings can be produced for experi- mental manipulation by protecting aerial tissues from surface wetting. At Barro Colorado Island, Panama, we used transects of endophyte-free seedlings to de- termine the importance of several factors (canopy cover, abundance of aerial and epiphytic propagules, leaf age, leaf chemistry, leaf toughness and duration of exposure to viable air spora) in shaping coloniza- tion by endophytic fungi. Endophytes colonized leaves of T. cacao more rapidly beneath the forest canopy than in cleared sites, reflecting local abun- dance of aerial and epiphytic propagules. The dura- tion of exposure, rather than absolute leaf age, influ- enced endophyte infection, whereas leaf toughness and chemistry had no observed effect. Endophytes isolated from mature T. cacao grew more rapidly on media containing leaf extracts of T. cacao than on media containing extracts from other co-occurring tree species, suggesting that interspecific differences in leaf chemistry influence endophyte assemblages. Together, these data allow us to identify factors un- derlying patterns of endophyte colonization within healthy leaves of this tropical tree.
Marjo Helander - One of the best experts on this subject based on the ideXlab platform.
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geographic variation in festuca rubra l ploidy levels and systemic fungal endophyte frequencies
PLOS ONE, 2016Co-Authors: Serdar Dirihan, Pedro E. Gundel, Lucas A Garibaldi, Marjo Helander, Henry Vare, Gonzalo J N Irisarri, Irma Saloniemi, Kari SaikkonenAbstract:Polyploidy and symbiotic Epichloe fungal Endophytes are common and heritable characteristics that can facilitate environmental range expansion in grasses. Here we examined geographic patterns of polyploidy and the frequency of fungal endophyte colonized plants in 29 Festuca rubra L. populations from eight geographic sites across latitudes from Spain to northernmost Finland and Greenland. Ploidy seemed to be positively and negatively correlated with latitude and productivity, respectively. However, the correlations were nonlinear; 84% of the plants were hexaploids (2n = 6x = 42), and the positive correlation between ploidy level and latitude is the result of only four populations skewing the data. In the southernmost end of the gradient 86% of the plants were tetraploids (2n = 4x = 28), whereas in the northernmost end of the gradient one population had only octoploid plants (2n = 8x = 56). Endophytes were detected in 22 out of the 29 populations. Endophyte frequencies varied among geographic sites, and populations and habitats within geographic sites irrespective of ploidy, latitude or productivity. The highest overall endophyte frequencies were found in the southernmost end of the gradient, Spain, where 69% of plants harbored Endophytes. In northern Finland, Endophytes were detected in 30% of grasses but endophyte frequencies varied among populations from 0% to 75%, being higher in meadows compared to riverbanks. The Endophytes were detected in 36%, 30% and 27% of the plants in Faroe Islands, Iceland and Switzerland, respectively. Practically all examined plants collected from southern Finland and Greenland were endophyte-free, whereas in other geographic sites endophyte frequencies were highly variable among populations. Common to all populations with high endophyte frequencies is heavy vertebrate grazing. We propose that the detected endophyte frequencies and ploidy levels mirror past distribution history of F. rubra after the last glaciation period, and local adaptations to past or prevailing selection forces such as vertebrate grazing.
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Epichloe fungal Endophytes for grassland ecosystems
Sustainable Agriculture Reviews, 2016Co-Authors: David E. Hume, Anaïs Gibert, Geraldine D Ryan, Agha Fakhr Mirlohi, Marjo Helander, Mohammad R. SabzalianAbstract:The Epichloe fungal Endophytes that inhabit grasses have potentially large-scale consequences for macro- and micro-organisms and food chains in agriculture. Over 40 years of study on the benefits of symbiotic Epichloe fungal Endophytes for host grasses, investigations have focused on the major agricultural species, tall fescue and perennial ryegrass. However, many other grass species remain to be evaluated for the effects of Epichloe Endophytes. Animal toxicity due to accumulation of nitrogenous compounds, e.g. endophyte-dervived alkaloids, particularly in areas and periods under abiotic stress, still prevent widespread application of endophyte-infected grasses in agroecosystems.
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Nutritional niche overlap potentiates the use of Endophytes in biocontrol of a tree disease
BioControl, 2015Co-Authors: Kathrin Blumenstein, Juan A Martin, Benedicte R. Albrectsen, Marjo Helander, Malin Hultberg, Thomas N. Sieber, Johanna WitzellAbstract:Asymptomatic endophytic fungi are often regarded as potent biocontrol agents in plants, but the competitive interactions between Endophytes and other microbes within the same host plant are poorly understood. We tested a hypothesis that as compared to asymptomatic Endophytes, an aggressive pathogen inhabiting the same host is able to utilize carbon substrates more efficiently. Using phenotype microarray, we determined the carbon utilization profiles of the highly virulent Dutch elm disease (DED) pathogen Ophiostoma novo - ulmi , and four asymptomatic elm ( Ulmus spp.) endophyte isolates that were selected based on their differential association to the DED-susceptibility pattern of the host elms. The competitive interactions between isolates were evaluated using a niche overlap index. In contrast to our hypothesis, the studied Endophytes exhibited extensive niche overlap with the pathogen, suggesting that some endophyte strains might protect elms against DED-pathogen through competition for substrates and provide new tools for biocontrol of DED.
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fungal endophyte mediated occurrence of seminiferous and pseudoviviparous panicles in festuca rubra
Fungal Diversity, 2014Co-Authors: Pedro E. Gundel, Piippa R Wali, Lucas A Garibaldi, Marjo Helander, Serdar Dirihan, Kari SaikkonenAbstract:Fungal Endophytes are suggested to manipulate host grass reproduction. Using different grass-endophyte combinations in a four year common garden experiment, we show that endophyte can retain control over the reproductive functions of the host. Plants were collected as seeds from two different environments, meadows and riverbanks. Natural endophyte infection (E+) increased reproductive effort of plants; 13 and 15 % higher proportion of E+ plants produced panicles compared to naturally uninfected (E-) and manipulatively endophyte-infected (ME+) plants, respectively. Meadow-origin E+ plants produced also higher number of panicles compared to E- in the last two years, and both meadow- and riverbank-origin ME+ plants produced higher number of panicles compared to ME- plants in most of the years. Pseudovivipary was recorded in 5 % of the plants each year. Pollen limitation appears not to induce pseudovivipary. Both E+ and ME+ plants produced higher number of seminiferous panicles compared to E- and ME- plants. The higher proportion of pseudoviviparism in ME+ plants compared to E+, E- and ME- plants from meadows suggests specific genotype-genotype cross-talk between endophyte and grass. Pseudovivipary was affected by year and primarily explained by plant reproductive effort since most vigorous plants produced more pseudoviviparous panicles. We propose that Endophytes can promote host grass reproduction in a habitat-specific manner and depending on genetic compatibility between partners. However, reproductive behavior depended on maternal habitat and the annual environmental conditions highlighting the importance of long-term experiments to estimate the effects of Endophytes on host plant ecology.
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Chemical Ecology Mediated by Fungal Endophytes in Grasses
Journal of Chemical Ecology, 2013Co-Authors: Kari Saikkonen, Pedro E. Gundel, Marjo HelanderAbstract:Defensive mutualism is widely accepted as providing the best framework for understanding how seed-transmitted, alkaloid producing fungal Endophytes of grasses are maintained in many host populations. Here, we first briefly review current knowledge of bioactive alkaloids produced by systemic grass-Endophytes. New findings suggest that chemotypic diversity of the endophyte-grass symbiotum is far more complex, involving multifaceted signaling and chemical cross-talk between endophyte and host cells ( e.g. , reactive oxygen species and antioxidants) or between plants, herbivores, and their natural enemies ( e.g. , volatile organic compounds, and salicylic acid and jasmonic acid pathways). Accumulating evidence also suggests that the tight relationship between the systemic endophyte and the host grass can lead to the loss of grass traits when the lost functions, such as plant defense to herbivores, are compensated for by an interactive endophytic fungal partner. Furthermore, chemotypic diversity of a symbiotum appears to depend on the endophyte and the host plant life histories, as well as on fungal and plant genotypes, abiotic and biotic environmental conditions, and their interactions. Thus, joint approaches of (bio)chemists, molecular biologists, plant physiologists, evolutionary biologists, and ecologists are urgently needed to fully understand the endophyte-grass symbiosis, its coevolutionary history, and ecological importance. We propose that endophyte-grass symbiosis provides an excellent model to study microbially mediated multirophic interactions from molecular mechanisms to ecology.
Edward Allen Herre - One of the best experts on this subject based on the ideXlab platform.
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Fungal Endophytes limit pathogen damage in a tropical tree
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: A. E. Arnold, Zuleyka Maynard, Luis C. Mejía, Damond Kyllo, Enith I. Rojas, Nancy Robbins, Edward Allen HerreAbstract:Every plant species examined to date harbors endophytic fungi within its asymptomatic aerial tissues, such that Endophytes represent a ubiquitous, yet cryptic, component of terrestrial plant communities. Fungal Endophytes associated with leaves of woody angiosperms are especially diverse; yet, fundamental aspects of their interactions with hosts are unknown. In contrast to the relatively species-poor Endophytes that are vertically transmitted and act as defensive mutualists of some temperate grasses, the diverse, horizontally transmitted Endophytes of woody angiosperms are thought to contribute little to host defense. Here, we document high diversity, spatial structure, and host affinity among foliar Endophytes associated with a tropical tree (Theobroma cacao, Malvaceae) across lowland Panama. We then show that inoculation of endophyte-free leaves with Endophytes isolated frequently from naturally infected, asymptomatic hosts significantly decreases both leaf necrosis and leaf mortality when T. cacao seedlings are challenged with a major pathogen (Phytophthora sp.). In contrast to reports of fungal inoculation inducing systemic defense, we found that protection was primarily localized to endophyte-infected tissues. Further, endophyte-mediated protection was greater in mature leaves, which bear less intrinsic defense against fungal pathogens than do young leaves. In vitro studies suggest that host affinity is mediated by leaf chemistry, and that protection may be mediated by direct interactions of Endophytes with foliar pathogens. Together, these data demonstrate the capacity of diverse, horizontally transmitted Endophytes of woody angiosperms to play an important but previously unappreciated role in host defense.
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canopy cover and leaf age affect colonization by tropical fungal Endophytes ecological pattern and process in theobroma cacao malvaceae
Mycologia, 2003Co-Authors: Elizabeth A Arnold, Edward Allen HerreAbstract:Fungal Endophytes inhabit healthy tissues of all terrestrial plant taxa studied to date and are diverse and abundant in leaves of tropical woody an- giosperms. Studies have demonstrated that plant lo- cation and leaf age influence density of endophyte infection in leaves of tropical forest trees. However, ecological factors underlying these observations have not been explored in detail. Here, we establish that foliar Endophytes of a tropical tree (Theobroma cacao, Malvaceae) are transmitted horizontally and that en- dophyte-free seedlings can be produced for experi- mental manipulation by protecting aerial tissues from surface wetting. At Barro Colorado Island, Panama, we used transects of endophyte-free seedlings to de- termine the importance of several factors (canopy cover, abundance of aerial and epiphytic propagules, leaf age, leaf chemistry, leaf toughness and duration of exposure to viable air spora) in shaping coloniza- tion by endophytic fungi. Endophytes colonized leaves of T. cacao more rapidly beneath the forest canopy than in cleared sites, reflecting local abun- dance of aerial and epiphytic propagules. The dura- tion of exposure, rather than absolute leaf age, influ- enced endophyte infection, whereas leaf toughness and chemistry had no observed effect. Endophytes isolated from mature T. cacao grew more rapidly on media containing leaf extracts of T. cacao than on media containing extracts from other co-occurring tree species, suggesting that interspecific differences in leaf chemistry influence endophyte assemblages. Together, these data allow us to identify factors un- derlying patterns of endophyte colonization within healthy leaves of this tropical tree.
Trichur S. Suryanarayanan - One of the best experts on this subject based on the ideXlab platform.
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Fungal Endophytes: an untapped source of biocatalysts
Fungal Diversity, 2012Co-Authors: Trichur S. Suryanarayanan, Nagamani Thirunavukkarasu, Meenavalli B. Govindarajulu, Venkat GopalanAbstract:Horizontally transmitted Endophytes are an ecological group of fungi that infect living plant tissues and survive in them without causing any disease symptoms. Even as facets of the endophyte-plant symbiotic relationship are being uncovered, there is an increasing appreciation of the different growth substrates exploited by Endophytes and the vast repertoire of secreted enzymes of these fungi. These attributes exemplify the striking biodiversity of fungal Endophytes and should motivate bioprospecting these organisms to identify novel biocatalysts that might help address challenges in medicine, food security, energy production and environmental quality.
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Endophytic fungal communities in woody perennials of three tropical forest types of the Western Ghats, southern India
Biodiversity and Conservation, 2011Co-Authors: Trichur S. Suryanarayanan, T. S. Murali, M. B. Govinda Rajulu, Nagamani Thirunavukkarasu, G. Venkatesan, R SukumarAbstract:Fungal Endophytes of tropical trees are expected to be exceptionally species rich as a consequence of high tree diversity in the tropics and the purported host restriction among the Endophytes. Based on this premise, Endophytes have been regarded as a focal group for estimating fungal numbers because their possible hyperdiverse nature would reflect significantly global fungal diversity. We present our consolidated ten-year work on 75 dicotyledonous tree hosts belonging to 33 families and growing in three different types of tropical forests of the NBR in the Western Ghats, southern India. We conclude that endophyte diversity in these forests is limited due to loose host affiliations among Endophytes. Some Endophytes have a wide host range and colonize taxonomically disparate hosts suggesting adaptations in them to counter a variety of defense chemicals in their hosts. Furthermore, such polyphagous Endophytes dominate the endophyte assemblages of different tree hosts. Individual leaves may be densely colonized but only by a few endophyte species. It appears that the environment (the type of forest in this case) has a larger role in determining the endophyte assemblage of a plant host than the taxonomy of the host plant. Thus, different tropical plant communities have to be studied for their endophyte diversity to test the generalization that Endophytes are hyperdiverse in the tropics, estimate their true species richness, and use them as a predictor group for more accurate assessment of global fungal diversity.
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Fungal endophyte communities in two tropical forests of southern India: diversity and host affiliation
Mycological Progress, 2007Co-Authors: T. S. Murali, Trichur S. Suryanarayanan, G. VenkatesanAbstract:Fifteen tree species from a tropical dry thorn forest and fifteen tree species from a tropical dry deciduous forest in the Mudumalai Wildlife Sanctuary, Nilgiri Biosphere Reserve, southern India, were surveyed for their foliar endophyte communities during the dry and wet seasons. Surface sterilized leaf segments of uniform dimension were plated on nutrient agar and culturable Endophytes growing from the segments were identified. Endophyte diversity was greater in the dry thorn forest than in the dry deciduous forest in the dry season. Although the isolation frequency of culturable Endophytes increased for both forests during the wet season, the assemblages were represented not by any unique fungal species but by the commonly occurring ones. Furthermore, although individual leaves were densely colonized by Endophytes, only a few species of Endophytes colonized the whole leaves; and, only a few fungal species dominated the foliar endophytic communities and were common for both forests during both dry and wet seasons. Thus, even under wet conditions that favour dispersal and infection by fungi, the endophyte diversity increased only marginally, an indication that certain tropical forests are not hyperdiverse with reference to fungal Endophytes. This should be considered when using culturable endophyte diversity as a surrogate for estimating global fungal diversity.