Charles W. Bacon

Molecular phylogeny of Acremonium and its taxonomic implications.

Acremonium is generally considered to be a highly polyphyletic form genus containing distantly related fungi. Sectional divisions within Acremonium distinguish the clavicipitaceous grass endophytes of sect. Albolanosa from the generally saprobic species of sections Acremonium, Chaetomioides, Gliomastix, and Nectrioidea. In an effort to assess the possible number of lineages currently placed within Acremon- ium and to determine which groups of sexual asco- mycetes are phylogenetically affiliated with Acremon- ium species, maximum parsimony and neighborjoin- ing analyses were performed using partial sequences of the nuclear small subunit ribosomal DNA (18S rDNA). Acremonium was shown to be a polyphyletic taon with affiliations to at least three ascomycetous orders: 1) most of the examined species from the sections Acremonium, Gliomastix, and Nectrioidea showed a relationship to the Hypocreaceae even though many of these species have never been asso- ciated with any teleomorph; 2) the grass endophytes of sect. Albolanosa and other taxa from the Clavicip- itaceae formed a monophyletic group derived from within the Hypocreales; 3) the thermophilic A. ala- bamense of sect. Chaetomioides was derived from with- in the Sordariales. Acremonium alternatum, the tye species of the genus, was one of the species showing affiliation to the Hypocreaceae. In order to eliminate some of the heterogeneity within Acremonium while also emphasizing the unique biological, morpholog- ical, and ecological characteristics of the grass en do-

Fungal endophyte-infected grasses: Alkaloid accumulation and aphid response.

The occurrence of the alkaloidsN-formyl andN-acetyl loline, peramine, lolitrem B, and ergovaline and the response of aphids to plants containing these compounds were determined in species and cultivars ofFestuca,Lolium, and other grass genera infected with fungal endophytes (Acremonium spp., andEpichloe typhina). Twenty-nine of 34 host-fungus associations produced one or more of the alkaloids, most frequently peramine or ergovaline. Three alkaloids (lolines, peramine, and ergovaline) were found in tall fescue and in perennial ryegrass infected withA. coenophialum, while peramine, lolitrem B, and ergovaline were present in perennial ryegrass and in tall fescue infected withA. lolii and inF. longifolia infected withE. typhina. WhileA. coenophialum andA. lolii produced similar patterns of alkaloids regardless of the species or cultivar of grass they infected, isolates ofE. typhina produced either no alkaloids or only one or two different alkaloids in the grasses tested. Aphid bioassays indicated thatRhopalosiphum padi andSchizaphis graminum did not survive on grasses containing loline alkaloids and thatS. graminum did not survive on peramine-containing grasses. Ergovaline-containing grasses did not affect either aphid.

Biotechnology of endophytic fungi of grasses

Detailing current research on grass endophytes, this work presents procedures for isolation, inoculation, fungus and plant tissue culturing, staining and molecular methodology. Chapters on the ecology of grass hosts document the benefits of endophytes to grass hosts and discuss this topic in terms of a mathematical model. Chemical constituents of infected grasses and methods to alleviate toxic effects are identified. The current use of endophytes to increase plant hardiness in turf and forage grasses is explained. Techniques for screening and selecting endophytes and for genetic modification of endophytes are described. The text discusses the impact of endophyte-infected grasses on the environment, looks at the response of endophyte-infected grasses and grasslands to increased atmospheric CO2 and radiation, and provides techniques and procedures for studying endophytes.

Nomenclatural realignment of Neotyphodium species with genus Epichloë

Nomenclatural rule changes in the International Code of Nomenclature for algae, fungi and plants, adopted at the 18th International Botanical Congress in Melbourne, Australia, in 2011, provide for a single name to be used for each fungal species. The anamorphs of Epichloë species have been classified in genus Neotyphodium, the form genus that also includes most asexual Epichloë descendants. A nomenclatural realignment of this monophyletic group into one genus would enhance a broader understanding of the relationships and common features of these grass endophytes. Based on the principle of priority of publication we propose to classify all members of this clade in the genus Epichloë. We have reexamined classification of several described Epichloë and Neotyphodium species and varieties and propose new combinations and states. In this treatment we have accepted 43 unique taxa in Epichloë, including distinct species, subspecies, and varieties. We exclude from Epichloë the two taxa Neotyphodium starrii, as nomen dubium, and Neotyphodium chilense, as an unrelated taxon.

Abiotic stress tolerances (moisture, nutrients) and photosynthesis in endophyte-infected tall fescue

Abstract The ecological significance resulting from the association of each tall fescue (Festuca arundinacea Schreb.) genotype and its companion fungal endophyte (Acremonium coenophialum Morgan-Jones and Gams) is probably inherent in the nutritional interactions, and the resulting physiological and biochemical requirements of each. The colonization of this grass by the fungus follows the natural sequence of fescue seed germination, seedling and tiller growth. Infected grasses are natural and extensive, therefore tall fescue should be considered a symbiotic plant. The nature of this relationship at the population level is more appropriately described as an obligately biotrophic conjunctive mutualism. The use of this terminology at the population level describes the overall ecological effect; however, allowances must be made for infected tall fescue genotypes within the population that may not show any positive adaptive strategies. Genotypes of this later category may be categorized, possibly only transiently, as obligately neutral symbiotic. Infected genotypes of the earlier category offer adaptations to environmental stresses and may be exploited for these characteristics. Evidence from research is reviewed to indicate that selected genotypes within the population of tall fescue are more tolerant of environmental abiotic stresses than uninfected grasses. Infected tall fescue seed require more moisture to germinate than uninfected seed. Endophyte-infected seedlings require more nutrients than uninfected seedlings. Although infected tall fescue contains less soluble nitrogen which would encourage more predation, strains resulting from the stresses of insect herbivory are prevented because of an accumulation of an insect deterrent, toxins and their synergists. At the morphological level infected grasses show tolerance to water stress by early shedding of older leaves and rolling of younger leaves. Tolerance to water stress is further evidenced by low stomatal conductances and by development of an enhanced osmoregulatory system that produces increased cellular turgor pressure. One genotype of tall fescue contains polyols, some of which are absent in the uninfected clone. Infected tall fescue also shows increased efficiency to low soil nitrogen, possibly due to an increased level of glutamine synthetase which would enhance its competitive ability under low soil nitrogen. There is no endophyte effect of consequence on photosynthesis and associated processes in several genotypes of infected grasses.

Enterobacter cloacae is an endophytic symbiont of corn

The bacteriumEnterobacter cloacae is presently used for biocontrol of postharvest diseases of fruits and vegetables and as a preplant seed treatment for suppression of damping-off. This bacterium has apparent affinities for several grass species, but it is not considered to be an endophyte. While screening corn for fungi and bacteria with potential for biocontrol of various corn diseases, the surface-sterilized kernels of one unknown Italian corn cultivar produced fungus-free corn seedlings with roots endophytically infected byE. cloacae. This paper describes the microscopic nature ofE. cloacae RRC 101 with corn, and the in vitro control ofFusarium moniliforme and other fungi with this bacterium. Light and electron microscopy determined that this isolate ofE. cloacae was biologically associated with corn seedling roots, where it was distributed intercellularly within the cortex and stele. This is a first report of a strain of this bacterium as an endophytic symbiont of roots. Following a topical application ofE. cloacae to kernels, and upon germination this bacterium readily infected roots of two other corn cultivars. The bacterium was observed within the endosperm of germinating corn seedling, but germination was not affected. Further, the bacterium was isolated from leaves and stems of 3- to 6-week-old seedlings indicating that the above ground portions of corn were also colonized. There was no evidence of damage to cells of the root during a three to four week observation period. This bacterium was antagonistic to several isolates of the corn pathogenFusarium moniliforme, and to two other species of fungi, all of which produce mycotoxins on corn.

Hepatotoxicity and renal toxicity in rats of corn samples associated with field cases of equine leukoencephalomalacia

Currently there is no convenient bioassay to determine the potential toxicity of corn naturally contaminated with Fusarium moniliforme. A short-term bioassay would be useful for future investigations aimed at isolating as yet unidentified toxins produced by this fungus. Two groups of five male Sprague-Dawley rats were each fed one of two F. moniliforme contaminated corn samples, designated CS-1 and CS-2, that were associated with separate field cases of equine leukoencephalomalacia (ELEM). A control group, also consisting of five male rats, was fed uncontaminated seed corn. All animals survived to the end of the study and there were no apparent differences in appearance or behaviour among groups. Weight loss and irregular food consumption occurred in all groups and probably resulted from nutritional deficiencies inherent in the corn diets. Hepatocellular degeneration, necrosis and hyperplasia as well as biliary hyperplasia were found in the test groups only and were attributed to F. moniliforme. Serum transaminase and alkaline phosphatase activities in animals fed CS-1 and CS-2 for 4 wk were significantly increased compared with the controls, while serum bilirubin concentration was increased only in the CS-1 group. Tubular nephrosis was also present in the renal cortex of all animals fed CS-1 and CS-2. These effects may have been related to fumonisins B1 and B2, recently discovered metabolites of F. moniliforme, that were found in both CS-1 and CS-2. Short-term studies of this type may be useful in screening naturally-contaminated grains and other materials for hepatotoxic metabolites produced by F. moniliforme.

A Method of Detection of Fumonisins in Corn Samples Associated with Field Cases of Equine Leukoencephalomalacia

Fumonisin ft{ and B2, members ofa new class of mycotoxins, were measured in culture material of Fusarium moniliforme MRC826, and in two corn samples associated with field cases of equine leukoencephalomalacia. The compounds were detected by thin-layer chromatography (TLC) with confirmation by liquid secondary ion-mass spectrometry (SIMS) and by gas chromatography/mass spectrometry (GC/MS). Reference standards were isolated from cultures of F. moniliforme on corn. The level of fumonisin B! was about 600 mg/kg in the culture material and 150 and 20 mg/kg in the two naturally contaminated samples.

One fungus, one name

In this letter, we advocate recognizing the genus Fusarium as the sole name for a group that includes virtually all Fusarium species of importance in plant pathology, mycotoxicology, medicine, and basic research. This phylogenetically guided circumscription will free scientists from any obligation to use other genus names, including teleomorphs, for species nested within this clade, and preserve the application of the name Fusarium in the way it has been used for almost a century. Due to recent changes in the International Code of Nomenclature for algae, fungi, and plants, this is an urgent matter that requires community attention. The alternative is to break the longstanding concept of Fusarium into nine or more genera, and remove important taxa such as those in the F. solani species complex from the genus, a move we believe is unnecessary. Here we present taxonomic and nomenclatural proposals that will preserve established research connections and facilitate communication within and between research communities, and at the same time support strong scientific principles and good taxonomic practice.

One fungus, one name: defining the genus Fusarium in a scientifically robust way that preserves longstanding use.

In this letter, we advocate recognizing the genus Fusarium as the sole name for a group that includes virtually all Fusarium species of importance in plant pathology, mycotoxicology, medicine, and basic research. This phylogenetically guided circumscription will free scientists from any obligation to use other genus names, including teleomorphs, for species nested within this clade, and preserve the application of the name Fusarium in the way it has been used for almost a century. Due to recent changes in the International Code of Nomenclature for algae, fungi, and plants, this is an urgent matter that requires community attention. The alternative is to break the longstanding concept of Fusarium into nine or more genera, and remove important taxa such as those in the F. solani species complex from the genus, a move we believe is unnecessary. Here we present taxonomic and nomenclatural proposals that will preserve established research connections and facilitate communication within and between research communities, and at the same time support strong scientific principles and good taxonomic practice.