Showing papers on "Epichloë published in 1997"

Bioprotective Alkaloids of Grass-Fungal Endophyte Symbioses

Abstract: Symbiotic interactions of C3 grasses with fungal endophytes, Epichloe species and their asexual relatives Neotypkodium, often provide the grass hosts with major fitness enhancements (for review, see Siegel and Bush [1994]). The endophytes protect host plants from both biotic and abiotic environmental stresses. Documented enhancements to host fitness include greater resistance to mammalian and insect herbivores, pathogens, and nematodes, as well as increased drought tolerance and competitiveness. Our understanding of the mechanisms responsible for a11 of these effects on host fitness is not well established. However, the antiherbivore fitness enhancements are largely attributable to the accumulation of four groups of alkaloids: lolines, peramine, ergot alkaloids, and lolitrems. The objective of this Update is to present the current status of knowledge on these alkaloids, focusing on their biological activities and the potential for genetically manipulating their expression in grasslendophyte symbiota.

Protective Grass Endophytes: Where are they from and where are they going?

Abstract: erhaps the most widely used agents of biological plant protection are endophytic fungal symbionts (endophytes) of forage and turfgrasses. These are fungi of the family Clavicipitaceae, which grow between host cells in vegetative tissues, ovules, and seeds of systemically infected grass plants. The existence of these endophytes was not fully appreciated until recent years, although the protection they provide against insect damage (Fig. 1) and drought contributes to the superior agronomic qualities of favorite pasture grasses in North America, Australia, and New Zealand. Unfortunately for livestock farmers, these endophytes also provide a degree of protection from grazing mammals. In 1977, Bacon et al. (2) reported that the grass Festuca arundinacea var. genuina Schreb. (hexaploid tall fescue) had a fungal endophyte related to Epichloe typhina (Pers.:Fr.) Tul., and that this endophyte— now known as Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon, & Hanlin—was responsible for toxicosis suffered by livestock grazing the grass. Epichloe species were known for many decades (44), but reports relating that nonpathogenic endophytes could be detrimental to livestock provided new impetus for intensive studies, making the grass–endophyte associations among the best characterized symbioses in biology. Less than two decades of research have yielded a rich body of knowledge about these symbioses: their secondary product chemistry, ecology, evolution, genetics, and molecular biology; their ecological roles as protectants from insect and vertebrate herbivores, pathogenic fungi and nematodes, and drought; and their effects on host growth and competitiveness. The endophytes produce numerous alkaloids, some of which are unrelated to any known from plants or other fungi. Their genetic and evolutionary complexity is extraordinary. They were the first fungi genetically documented as interspecific hybrids (47,53). Meanwhile, molecular genetic techniques were applied to the endophytes of tall fescue and other grasses, bringing us closer to the prospect of reducing or eliminating their toxicosis to livestock while continuing to employ their bioprotective qualities.

Molecular systematics of Clavicipitaceae supporting monophyly of genus Epichloe and form genus Ephelis

Abstract: The family Clavicipitaceae (Ascomycota) is comprised of fungi with perithecia borne on stro- mata, unitunicate asci, and filamentous, multiseptate ascospores. All are biotrophic symbionts, either mu- tualistic with plant hosts or pathogenic to plants, in- vertebrate animals or other fungi. Genera of plant- associated Clavicipitaceae (tribes Balansieae and Clavicipieae) are distinguished, in part, by stromal and ascus morphology, ascospore germination pat- terns, whether sclerotia are formed, and host inter- actions. Their anamorphs include enteroblastic mi- croconidial states, classified in anamorphic genera Neotyphodium and Sphacelia (for teleomorphs Atkin- sonella, Claviceps, Echinodothis, and Epichloe), and ho- loblastic macroconidia, classified in the anamorphic genus Ephelis (teleomorphs Atkinsonella, Balansia, and Myriogenospora). Epichloe' species often are mu- tualistic with grass hosts, and are ancestral to asexual, seed transmitted endophytes symbiotic with many cool-season grasses. Partial 28S nuclear rDNA se- quences were determined from isolates of five species and two undescribed mating populations of Epichloe, one asexual Epichloe hybrid (Neotyphodium coeno- phialum), and representatives of six other genera in the family. Results from phylogenetic analysis of the sequences supported monophyly of plant-associated Clavicipitaceae, with insect-pathogenic Cordyceps spe- cies more deeply rooted. Four clades were distin-

Ecological diversity in neotyphodium-infected grasses as influenced by host and fungus characteristics

Abstract: Neotyphodium is the newly proposed name for the asexual state of the clavicipitaceous genus Epichloe (Glenn et al. 1996). The members of this endophytic genus form systemic, long-term associations with numerous cool season grasses (Leuchtmann 1992, White 1987). In these associations, the two partners have developed an intimate relationships over evolutionary time which in most cases can be regarded as mutualistic. The symbiosis may be more antagonistic in endophyte species which, during their sexual reproduction, profoundly affect the reproductive system of the host.

Distribution of Ergot Alkaloids within the Family Clavicipitaceae

Abstract: In the twenty years since the first report of an ergot alkaloid-producing endophytic fungus being the causal agent of grass-associated toxicoses in livestock (Bacon et al., 1977), the production of these alkaloids are now well documented among several grass endophytes of the family Clavicipitaceae (Porter, 1994). These endophytes have been shown to convey to the host grasses certain advantageous physiological and ecological characteristics such as increased vigor, tolerance, and resistance to drought and pests (West, 1994; Rowan and Latch, 1994). Research interests have begun to focus on the potential manipulation of the fungi to retain the beneficial qualities communicated to the plant but to down-regulate or eliminate the production of toxicosis-inducing ergot alkaloids (Schardl, 1994). However, little attention has been given to the distribution of these alkaloids within the Clavicipitaceae. While select species of grass endophytes within the genera Neotyphodium, Epichloe, and Balansia have been assayed for alkaloid production, a broad sampling of the entire family is lacking, especially among the entomopathogenic species. We have undertaken such a sampling within a phylogenetic construct and have assayed ergot alkaloid production by certain grass associates and by several species of entomopathogenic Cordyceps with the objective of more clearly defining the evolutionary history, derivation, and biological significance of ergot alkaloids within the family.

Interactions of Grasses with Endophytic Epichloë Species and Hybrids

Abstract: Symbioses of Epichloe-type endophytic fungi (e-endophytes) in grasses have been known for many decades,1 but their ecological and agronomic importance came to light only recently. In 1977, Bacon et al.2 associated antimammalian activity with a common endophyte of the forage grass, hexaploid tall fescue (Festuca arundinacea var. genuino). In 1985 Stewart3 recognized the protective effect of a perennial ryegrass (Lolium perenne) endophyte against Argentine stem weevil (Listronotis bonariensis), a major insect pest in New Zealand. Since then, numerous mutualistic characteristics of e-endophytes have been described4,5 and intense research has been conducted by groups concerned with many aspects of endophyte biology and symbiosis.6

Occurrence of fungal endophytes in forage grasses of south india

Abstract: Data on the distribution of fungal endophytes of grasses are confined only to a few species of temperate grasses such as Lolium and Festuca (White and Cole, 1985; Clay, 1987) There is a need to survey forage grasses of tropics for the presence of fungal endophytes and hence we screened seeds, leaf sheaths and roots of some of the principal forage grasses of South India