Fungal Endophyte Infection Research Articles

The role of fungal endophyte infection in the evolution of Lolium multiflorum resistance to diclofop‐methyl

Diclofop‐methyl resistance was evaluated in populations of Italian ryegrass (Lolium multiflorum Lam.) infected and uninfected with fungal endophyte (Neotyphodium). Survival was tested in susceptible populations using herbicide screening. The results served as inputs to a model for investigating the role of endophyte infection in the evolution of L. multiflorum resistance to herbicide. The tolerance of infected plants varied depending on the origin of the population and the herbicide dose. Only in some populations and at some diclofop‐methyl doses did plants infected with these endophytes have higher survivorship than endophyte‐free plants. The model demonstrated that endophytes might indeed play an important role in the evolution of herbicide‐resistant weeds, delaying the appearance of herbicide resistance.

Endophyte Infection Levels of Native and Naturalized Fescues in Illinois and England

SPYREAS, G., D.J. GIBSON, AND M.A. BASINGER. (Department of Plant Biology, Southern Illinois University at Carbondale, Carbondale, IL 62901). Endophyte infection levels of native and naturalized fescues in Illinois and England. J. Torrey Bot. Soc. 128:25-34. 2001.-Fungal endophytes are thought to play a major role in the ecology of many cool-season grasses. However, the frequency of endophyte infection in the wild remains poorly known. Populations of wild fescues were tested for systemic fungal endophyte infection by taking samples from four native or naturalized species throughout southern Illinois (Festuca arundinacea, F. rubra, F. obtusa, and F. paradoxa), and one of these species (F. arundinacea) from native populations in England. The two grasses native to southern Illinois (F. obtusa and F. paradoxa) were highly infected (mean infection of 91 % and 100 %, respectively). The introduced grass F. rubra was uninfected. Festuca arundinacea showed variable levels of infection among populations in both southern Illinois and England (71 % and 64 %, respectively). The role of endophytes in natural systems is contingent upon infection levels that appear to vary widely among these four species. Furthermore, the use of agricultural cultivars may differentially affect infection levels of naturalized plants.

Interaction between the endophytic fungus Epichloe bromicola and the grass bromus erectus: effects of endophyte infection, fungal concentration and environment on grass growth and flowering

Epichloe bromicola is an endophytic fungal species that systemically and perennially colonizes intercellular spaces of leaf blades, leaf sheaths and culms of Bromus grass species. E. bromicola causes choke disease in B. erectus, suppressing maturation of most, if not all, host inflorescences. In an investigation of the interaction between fungus and host, we used a quantitative polymerase chain reaction technique to estimate the amount of fungal DNA, and thereby fungal concentration, in host plants. Fungal concentration was directly correlated with vegetative vigour of the plant, as measured by longest leaf length, number of tillers and vegetative above-ground biomass, suggesting that, during vegetative growth, the endophytic fungus is most beneficial for the plant when present in high concentrations. In contrast, the reproduction of the plant, as measured by the number of functional inflorescences, was inversely correlated with fungal concentration: the majority of infected plants, and all that were associated with high concentrations of fungi, were diseased. Thus, the benefit of endophyte infection for the plant is coupled with the disadvantages of infertility. Fungal concentration was shown to be at least in part genetically determined because fungal concentration differed significantly in different plant-endophyte genotype combinations (symbiotum). In a field experiment with normal and CO2-enriched environments, elevated CO2 levels favoured fungal reproductive vigour over host reproductive vigour, suggesting that these plant endophytes would be at a selective advantage in a corresponding environmental-change scenario. We conclude that a dynamic and complex relationship between fungal endophyte infection, fungal concentration, genotype and environment affects growth and fecundity of B. erectus and should contribute to the evolution of these plant-fungal interactions.

Population Biology of Grasses

Contributors Preface Darwin revisited: approaches to the ecological study of grasses A. D. Bradshaw Part I. Population Variation and Life History Patterns: 1. Allozyme diversity in the grasses M. J. W. Godt and J. L. Hamrick 2. Ecology of seed dormancy and germination in grasses C. C. Baskin and J. M. Baskin 3. Seed dispersal and seedling establishment in grass populations G. P. Cheplick 4. Clonal biology of caespitose grasses D. D. Briske and J. D. Derner 5. Ecological aspects of sex expression in grasses J. A. Quinn 6. Interspecific variation in plasticity of grasses in response to nitrogen supply E. Garnier 7. Population biology of intraspecific polyploidy in grasses K. H. Keeler Part II. Ecological Interactions 8. Plant-plant interactions in grasses and grasslands W. K. Lauenroth and M. O. Aguilera 9. Competition between grasses and woody plants S. D. Wilson 10. Fungal endophyte infection and the population dynamics of grasses K. Clay 11. Arbuscular mycorrhizas and the population biology of grasses K. K. Newsham and A. R. Watkinson Part III. Population Biology of Specific Groups: 12. Population dynamics in the regeneration process of monocarpic dwarf bamboos, Sasa species A. Makita 13. Population dynamics of perennial grasses in African savanna and grassland T. G. O'Connor and T. M. Everson 14. A life cycle approach to the population ecology of two tropical grasses in Queensland, Australia D. M. Orr Index.

Endophytic fungal toxin effect on adrenergic receptors in lateral saphenous veins (cranial branch) of cattle grazing tall fescue.

The objective of this research was to characterize the adrenergic receptor response in veins of cattle that grazed tall fescue (Festuca arundinacea Schreb.), with (E+) and without (E-) fungal endophyte (Neotyphodium coenophialum) infection. Measurement of contractile response of lateral saphenous veins to selective adrenergic receptor agonists (alphal, phenylephrine; alpha2, BHT-920) revealed enhanced reactivity (greater contractile response) only for the alpha2 adrenergic receptor in E+ pastured cattle. This response was consistent over a 3-yr grazing period. Significant contractility differences in response to BHT-920 occurred at concentrations of 3x10(-6) M and greater. Early research has reasoned that the enhanced reactivity is due to endophyte toxin effect on intracellular signaling systems. The enhanced contractile effect would alter blood flow dynamics and contribute to clinical signs and pathologic change in animals. The alpha2-adrenergic receptor is also involved in the control of many metabolic reactions. Thus, for drug therapy to be successful in reversing the adverse effects of E+ tall fescue exposure in cattle, effects on the alpha2-adrenergic tissue receptors must be neutralized.

Physiological responses of Festuca arundinacea to fungal endophyte infection

summaryEnhanced growth rates of several grass species infected by fungal endophytes are known, but the underlying changes in plant physiology are not. Carbon exchange rates (CER) and leaf conductances (g) of 13 genotypes of tall fescue (Festuca arundinacea Schreb. var. KY 31) infected by the fungal endophyte Acremomum coenophialum Morgan‐Jones and Gams were measured at ambient conditions. Endophyte‐free ramets of the same genotypes were also measured. Correlations were calculated between environmental conditions at the time of measurement, and physiological responses. The only differential response of infected and uninfected ramets was to temperature. At low leaf temperatures no difference was seen between infected and uninfected plants. However, at leaf temperatures above 35°C infected tall fescue plants photosynthesized at a significantly greater rate (20–25%) than uninfected plants. This resulted from a decrease in the CER of uninfected plants, not an increase in the rate of infected plants, at high temperature. There were also significant infection × genotype interactions, indicating that the response to infection was specific to a given genotype. These results indicate that physiological responses of host plants to fungal endophyte infection depend both on the physical environment and the genotype of the plants.

Effects of Insect Herbivory and Fungal Endophyte Infection on Competitive Interactions among Grasses

Interactions among plants may be influenced by pests of parasites that differentially affect one competitor. The purpose of this study was to determine the effects of fungal parasitism and insect herbivory, alone in concert, on plant competitive interactions. The effects of fungal endophyte (Acermonium spp.) infection and fall armyworm (Spodoptera frugiperda) herbivory on competitive interactions in one— and two—species mixtures of the grasses tall fescue (Festuca arundinacea), red fescue (F. rubra), and perennial ryegrass (Lolium perenne) were examined in greehouse experiments. In general, herbivory reduced plant biomass whereas endophyte infection increased plant biomass. Endophyte infected (E+) plants were less damaged by herbivory than uninfected (E—) plants of the same species. Studies on fall armyworm larval feeding and choice tests with the five grass species were generally consistent with the outcome of the competition experiments; E+ plants were less nutritious and less preferred than E— plants of the same species. There were significant interactions among factors so that the outcome of competition depended on the species identities and the presence or absence of endophytes and herbivores. In competition with Kentucky bluegrass (Poa pratensis), E+ and E— perennial ryegrass produced similar biomass in the absence of herbivory, but E+ and E— perennial ryegrass had nearly twice the biomass of E— plants when herbivores were present. E+ and E— tall fescue were poor competitors with orchard grass (Dactylis glomerata) when herbivores were absent, but E+ tall fescue was a better competitors than E— plants and orchard grass when herbivores were present. This study indicates that competitive hierarchies among grasses are altered by interactions with insect herbivores and fungal endophytes, which have typically been ignored in past studies.

Effects of CO2 enrichment, nutrient addition, and fungal endophyte-infection on the growth of two grasses.

Increasing atmospheric carbon dioxide (CO2) concentration is expected to increase plant productivity and alter plant/plant interactions, but little is known about its effects on symbiotic interactions with microorganisms. Interactions between perennial ryegrass, Lolium perenne (a C3 plant), and purpletop grass, Tridens flavus (a C4 plant), and their clavicipitaceous fungal endophytes (Acremonium lolii and Balansia epichloe, respectively) were investigated by growing the grasses under 350 and 650 μl l- 1 CO2 at two nutrient levels. Infected and uninfected perennial ryegrass responded with increased growth to both CO2 enrichment and nutrient addition. Biomass and leaf area of infected and uninfected plants responded similarly to CO2 enrichment. When growth analysis parameters were calculated, there were significant increases in relative growth rate and net assimilation rate of infected plants compared to uninfected plants, although the differences remained constant across CO2 and nutrient treatments. Growth of purpletop grass did not increase with CO2 enrichment or nutrient addition and there were no significant differences between infected and uninfected plants. CO2 enrichment did not alter the interactions between these two host grasses and their endophytic-fungal symbionts.

Fungal Endophyte Infection in Italian Annual Ryegrass

Fungal Endophyte Infection in Italian Annual Ryegrass