Effects of the Fungal Endophyte Acremonium coenophialum on Nitrogen Accumulation and Metabolism in Tall Fescue

Abstract

Infection by the fungal endophyte Acremonium coenophialum affected the accumulation of inorganic and organic N in leaf blades and leaf sheaths of KY 31 tall fescue (Festuca arundinacea Schreb.) grown under greenhouse conditions. Total soluble amino acid concentrations were increased in either the blade or sheath of the leaf from infected plants. A number of amino acids were significantly increased in the sheath, but only asparagine increased in the blade. Infection resulted in higher sheath NH4+ concentrations, whereas N03-concentrations decreased in both leaf parts. The effects on amino acid, N03-, and NH4+ concentrations were dependent upon the level of N fertilization and were usually apparent only at the high rate (10 millimolar) of applica- feeding (2,4,5,11,21). Many effects similar to those in endophyte-infected tall fescue have also been demonstrated in other endophyte-infected species of fescue and in perennial ryegrass (Lolium perenne L.) ( 14, 21).The underlying physiological basis for the various effects on tall fescue which result from this endophyte infection, and the extent to which the grass and fungus are responsible, are largely unknown. Two lines of evidence suggest that at least N metabolism is one aspect that may be affected. The first is from greenhouse studies which show that high rates of N fertilization increased the concentrations of one class of endophyte-synthesized N bases, ergot alkaloids, in endophyteinfected tall fescue (16). Second, other classes of nitrogenous metabolites that are insect feeding deterrents are associated with endophyte infection. Furthermore, the expression of cattle toxicoses has been quantitatively related to rates of N fertilization (3,7,21). Thus, in tall fescue, both fungal and host N metabolism may be contributing factors to various characteristics which are peculiar to the infected plant.Because of the possible involvement of N metabolism in these important aspects of the tall fescue-endophyte association, comparative studies were made of infected and uninfected plants under greenhouse conditions to determine whether N metabolism is affected by the endophyte. Aspects considered in this study included the accumulation of inorganic and organic nitrogenous compounds, the activities of major enzymes of N assimilation, and the metabolism of amino acids. A

Effect of Neotyphodium Uncinatum Endophyte on Meadow Fescue Yielding, Health Status and Ergovaline Production in Host-Plants

“…As far as weather conditions are concerned, higher amounts of alkaloids are usually observed late in spring and early autumn. Higher nitrogen fertilisation also enhances an increase in the content of ergopeptine alkaloids in grasses (Lyons et al 1990;Belesky et al 1988). A three-fold increase in the nitrogen dose can increase the content of alkaloids by 60-80% in tall fescue, depending on the year.…”

Metabolic Profiles ofLolium perenneAre Differentially Affected by Nitrogen Supply, Carbohydrate Content, and Fungal Endophyte Infection

“…The impact of endophyte in reducing nitrate levels in grass leaves has also been shown by Lyons et al (1990), who used an N. coenophialum mutant strain that colonizes exclusively sheath tissues, and not blades, of tall fescue plants. Lyons et al (1990) saw infection by endophyte caused a reduction in nitrate levels in both sheaths and blades, in plants fertilized either with nitrate or ammonium.…”

“…The impact of endophyte in reducing nitrate levels in grass leaves has also been shown by Lyons et al (1990), who used an N. coenophialum mutant strain that colonizes exclusively sheath tissues, and not blades, of tall fescue plants. Lyons et al (1990) saw infection by endophyte caused a reduction in nitrate levels in both sheaths and blades, in plants fertilized either with nitrate or ammonium. It is known that both ectomycorrhizal and arbuscular mycorrhizal fungi can regulate plant N assimilation (Govindarajulu et al, 2005;Bailly et al, 2007), but as the foliar endophytes studied here are absent from the roots, their impacts on plant N uptake and transport are probably more indirect.…”

Enhancement of yield and persistence of perennial ryegrass inoculated with one endophyte isolate in France

“…The nitrogen deficiency tolerance of symbiotic tall fescue seems to be improved by an increased activity of glutamine synthetase regardless of nitrogen level or form favouring the utilisation of nitrogen [27].…”