D. P. Belesky

Leaf endophyte Neotyphodium coenophialum modifies mineral uptake in tall fescue.

Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, a fungal endophyte found primarily in shoots of tall fescue (Festuca arundinacea Shreb.), can modify rhizosphere activity in response to phosphorus (P) deficiency. In a controlled environment experiment, two cloned tall fescue genotypes (DN2 and DN4) free (E-) and infected (E+) with their naturally occurring endophyte strains were grown in nutrient solutions at low P (3.1 ppm) or high P (31 ppm) concentrations for 21 d. Endophyte infection increased root dry matter (DM) of DN4 by 21% but did not affect root DM of DN2. Under P deficiency, shoot and total DM were not affected by endophyte but relative growth rate was greater in E+ than E- plants. In high P nutrient solution, E+ plants produced 13% less (DN2) or 29% more (DN4) shoot DM than E- plants. Endophyte affected mineral concentrations in roots more than in shoots. Regardless of P concentration in nutrient solution, E+ DN2 accumulated more P, Ca, Zn and Cu but less K in roots than E- plants. When grown in high P nutrient solution, concentrations of Fe and B in roots of E+ DN2 plants were reduced compared with those of E- plants. Concentrations of P, Ca and Cu in roots of DN4 were less, but K was greater in E+ than E- plants. In shoots, E+ DN2 had greater concentrations of Fe and Cu than E- DN2, regardless of P concentration in nutrient solution. Genotype DN4 responded to endophyte infection by reducing B concentration in shoots. Nutrient uptake rates were affected by endophyte infection in plants grown in low P nutrient solution. A greater uptake rate of most nutrients and their transport to shoots was observed in DN2, but responses of DN4 were not consistent. Results suggest that endophyte may elicit different modes of tall fescue adaptation to P deficiency.

Evidence for chemical changes on the root surface of tall fescue in response to infection with the fungal endophyte Neotyphodium coenophialum

Endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.) plants grown in phosphorus (P) deficient soils accumulate more P in roots and shoots than noninfected isolines. In a growth chamber experiment, four tall fescue genotypes DN2, DN4, DN7, and DN11, infected with their naturally occurring strains of Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon & Hanlin, and their noninfected isolines (E-), were cultivated in nutrient solution at two P levels: 31 ppm (P+) and 0 ppm (P-) for 4 wk. The Fe3+ reducing activity of extracellular reductants and intact root tissues, and total phenolic concentration in roots and shoots were measured. Endophyte infection significantly increased Fe3+ reducing activity rate of extracellular reductants (9.6 × 10-3 μmol Fe3+ h-1 g-1 root FW) when compared to E- plants (3.9 × 10-3) and Fe3+ reduction rate of intact root tissues (6.16 and 4.48 μmol Fe3+ h-1 g-1 root FW, respectively for E+ and E- plants). In response to P deficiency, Fe3+ reduction rate of intact root tissues increased in E+ plants by 375% when compared to E- plants, whereas no significant differences were observed when P was provided. Total phenolic concentration was 20% greater in shoots of E+ plants than in E- plants. In response to P deficiency, total phenolic concentration significantly increased in roots of E+ plants by 7%, and decreased in roots of E- plants by 10%. The most active Fe3+ reducing zones were located along branching of secondary and tertiary roots. The Fe3+ reducing activity on the root surface and total phenolic concentration in roots and shoots increased dramatically in response to endophyte infection, especially under P limiting conditions.

Neotyphodium coenophialum‐endophyte infection affects the ability of tall fescue to use sparingly available phosphorus

Abstract Neotyphodium coenophialum, (Morgan‐Jones & Gams) Glenn, Bacon & Hanlin, infected tall fescue (Festuca arundinacea Schreb.) plants perform better than non‐infected isolines on phosphorus (P)‐deficient soils. Our objective was to characterize growth and P uptake dynamics of tall fescue in response to endophyte infection and P source at low P availability in soil. Two tall fescue genotypes (DN2 and DN4) infected with their naturally occurring N. coenophialum strains (E+), and in noninfected (E‐) forms were grown in Lily soil (fine loamy siliceous, mesic Typic Hapludult) in a greenhouse for 20 weeks. Three soil P treatments were imposed: no P supplied (control) and P supplied as commercial fertilizer (PF) or as phosphate rock (PR) at the level of 25 mg P kg‐1 soil. Interaction of tall fescue genotype and endophyte status had a significant influence on mineral element uptake suggesting high specificity of endophyte‐tall fescue associations. Endophyte infection did not affect root dry matter (DM) when ...

Influence of phosphorus on the growth and ergot alkaloid content of Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.)

Tall fescue (Festuca arundinacea Schreb.) plants infected by the fungal endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) (Glenn et al., 1996) often perform better than noninfected plants, especially in marginal resource environments. There is a lack of information about endophyte related effects on the rhizosphere of grasses. In a greenhouse experiment, four endophyte-infected (E+) tall fescue clones (DN2, DN4, DN7, DN11) and their endophyte-free (E−) forms were grown in limed (pH 6.3) Porter soil (low fertility, acidic, high aluminum and low phosphorus content, coarse-loamy mixed mesic Umbric Dystrochrept) at three soil P levels (17, 50, and 96 mg P kg-1 soil) for five months. Excluding the genotype effect, endophyte infection significantly increased cumulative herbage DM yield by 8% at 17 mg P kg-1 soil but reduced cumulative herbage DM yield by 12% at 96 mg P kg-1 soil. With increased P availability in the soil, shoot and root DM, and root/shoot ratio in E+ plants were significantly less when compared to E− plants. Endophyte infection increased specific root length at 17 and 50 mg P kg-1soil. At soil P level of 17 mg P kg-1soil, E+ plants had significantly higher P concentrations both in roots and shoots. Similar relationships were found for Mg and Ca. E+ plants had significantly higher Zn, Fe, and Al concentration in roots, and lower Mn and Al concentration in shoots when compared to E− plants. Ergot alkaloid concentration and content in shoot of E+ plants increased with increasing P availability in the soil from 17 to 50 mg P kg-1 but declined again at 96 mg P kg-1 soil. Ergot alkaloid accumulation in roots increased linearly with P availability in the soil. Results suggest that endophyte infection affects uptake of phosphorus and other mineral nutrients and may benefit tall fescue grown on P-deficient soils. Phosphorus seems also to be involved in ergot alkaloid accumulation in endophyte-infected tall fescue.

Evidence for copper binding by extracellular root exudates of tall fescue but not perennial ryegrass infected withNeotyphodium spp. endophytes

Infection of tall fescue (Festuca arundinacea Schreb.) with its endemicNeotyphodium coenophialum-endophyte (Morgan-Jones and Gams) Glenn, Bacon and Hanlin appears to reduce copper (Cu) concentrations in forage and serum of grazing animals, contributing to a range of immune-related disorders. A greenhouse experiment was conducted to identify effects of novel endophyte strains on Cu acquisition by tall fescue (Festuca arundinacea Schreb.) varieties Grasslands Flecha and Jesup infected with a novel, non ergot producing endophyte strain AR542, and two perennial ryegrass (Lolium perenne L.) varieties Aries and Quartet infected with a novel, non lolitrem B producing strain AR1, and their noninfected (E−) forms. Individual endophyte/grass associations were cultivated in nutrient solutions at 1.0 (P+) and 0.0 mM (P−) phosphorus concentrations. The Cu2+-binding activity of extracellular root exudates, and concentrations of Cu and other heavy metals in roots and shoots were measured. Extracellular root exudates of AR542-infected vs. E− tall fescue had higher Cu2+-binding activity only in P− nutrient solution as shown by lower concentration of free Cu2+ (0.096 vs. 0.188 mmol Cu2+ g−1 root DM, respectively). The Cu2+-binding activity by root exudates of perennial ryegrass was not affected by endophyte infection, but was higher (i.e., lower concentration of free Cu2+) in P− vs. P+ nutrient solution (0.068 vs. 0.114 mmol Cu2+ g−1 root DM). In this hydroponic experiment, Cu concentrations in shoots of both grasses were not a function of Cu2+-binding activity and endophyte effects on heavy metal concentrations in shoots and roots were specific for each variety. The Cu2+-binding activity of extracellular root exudates may affect Cu accumulation by field-grown, endophyte-infected tall fescue under P-limiting growth conditions and warrants verification by more specific methods.

Tall fescue aluminum tolerance is affected by neotyphodium coenophialum endophyte

Abstract Roots of endophyte‐infected (E+) tall fescue (Festuca arundinacea Schreb.) exude more phenolic‐like reductants than roots of endophyte‐free (E‐) plants when mineral stressed. Phenolic compounds are efficient chelators of aluminum (Al) and may influence Al tolerance in many plant species. The objective of our study was to determine if enhanced release of phenolic compounds by roots of E+ plants contributes to Al tolerance in tall fescue. Two cloned genotypes (DN2 and DN11) of tall fescue infected with their naturally occurring fungal endophyte Neotyphodium coenophialum (Morgan‐Jones and Gams) Glenn, Bacon and Hanlin and their noninfected isolines were grown in nutrient solutions at 0 μM Al (Al‐) and at 640 μM Al (Al+) under controlled environment conditions. Root and shoot dry matter (DM) of endophyte‐infected tall fescue was greater in E+ than E‐ plants by 57% and 40%, respectively, when plants were grown without Al. Endophyte infection did not affect root and shoot DM of tall fescue grown with A...

Tall fescue and associated mutualistic toxic fungal endophytes in agroecosystems

For the past 35 years, a significant effort was devoted to identifying the cause of tall fescue toxicosis, a symptomless infection of tall fescue (Schedonorus phoenix [Scop.] Holub, formerly Lolium arundinaceum [Schreb.] S. J. Darbyshire, and formerly Festuca arundinacea Schreb.) by a fungal endophyte Neotyphodium coenophialum Glenn, Hanlin, and Bacon. This endophyte grows intercellularly in stems and leaf sheaths of the host plant. Among the cool-season perennial forages, only tall fescue tolerated the punishing weather, inhospitable soil, and performance demands of beef operations on a consistent basis in the southeastern portion of the United States. Consequently, tall fescue became the forage grass of choice, which led eventually to its production on about 14 million hectares nationwide. Weather and soil conditions place numerous environmental- and management-induced stresses on the plant–fungus association that influence plant persistence and nutritive value, including alkaloid production. Livestock performance on endophyte-free tall fescue was shown to be superior to that obtained on endophyte-infected tall fescue, establishing the role of fungus in the syndrome. The suite of symptoms presenting in grazing cattle resembled ergotism but much of the early research did not target mycotoxins related to this malady. After discovery of the endophyte inhabiting tall fescue, research documented production of several types of ergot and other classes of alkaloids. This led, eventually, to numerous experiments designed to develop management strategies that reduced the toxic effects of host–endophyte associations on livestock health. Accumulation patterns of biologically active alkaloids and their responses to management were defined, suggesting possible ecological value of host–endophyte associations, and ultimately led to genetic approaches that minimized production of mycotoxins, while maintaining persistence and other agronomic traits of this valuable forage grass. Keywords:

The effect of phosphate rock dissolution on soil chemical properties and wheat seedling root elongation

Soils of the Appalachian region of the United States are acidic and deficient in P. North Carolina phosphate rock (PR), a highly substituted fluoroapatite, should be quite reactive in these soils, allowing it to serve both as a source of P and a potential ameliorant of soil acidity. An experiment was conducted to evaluate the influence of PR dissolution on soil chemical properties and wheat (Triticum aestivum cv. Hart) seedling root elongation. Ten treatments including nine rates of PR (0, 12.5, 25, 50, 100, 200, 400, 800, and 1600 mg P kg-1) and a CaCO3 (1000 mg kg-1) control were mixed with two acidic soils, moistened to a level corresponding to 33 kPa moisture tension and incubated for 30 days. Pregerminated wheat seedlings were grown for three days in the PR treated soils and the CaCO3 control. Root length was significantly (P<0.05) increased both by PR treatments and CaCO3, indicating that PR dissolution was ameliorating soil acidity. The PR treatments increased soil pH, exchangeable Ca, and soil solution Ca while lowering exchangeable Al and 0.01 M CaCl2 extractable soil Al. Root growth in PR treatments was best described by an exponential equation (P<0.01) containing 0.01 M CaCl2 extractable Al. The PR dissolution did not reduce total soil solution Al, but did release Al complexing anions into soil solution, which along with increased pH, shifted Al speciation from toxic to nontoxic forms. These results suggest that North Carolina PR should contribute to amelioration of soil acidity in acidic, low CEC soils of the Appalachian region.

Effect of nitrogen fertilization and mild water stress on the distribution of nitrogen in tall fescue

SummaryAn investigation was designed to examine the nature and distribution of nitrogen in tall fescue (Festuca arundinacea Schreb.) as influenced by water regime and N fertility under controlled environment conditions. Three replicates of 10 ppm and 110 ppm N were prepared for both adequately watered and water stress treatments of vegetatively propagated tall fescue. Herbage samples were lyophilized and soluble protein extracted in aqueous buffer and separated from low molecular weight N compounds. Two insoluble fractions (RI, cellular and structural fragments; RII, organellar residue, primarily chloroplasts) and two soluble fractions (SI, soluble protein; SII, low molecular weight compounds) were characterized by Kjeldahl N and acid-hydrolyzable amino-acid analyses.Mild water stress increased the crude protein (CP) concentration of tall fescue, especially under limited N conditions. Nitrogen was redistributed among the fractions when tall fescue was water stressed, regardless of N level. Under adequate water conditions at both N levels, about 30% of the soluble plant N was found in SI but under water stress, SI accounted for 50% of the soluble N. This pattern indicates a conservation of intact, nitrogenous material possibly due to decreased proteolysis under mild water stress conditions. The greatest proportion of total N occurred in fraction RI, regardless of water level, 10 N being greater than 110 N. Organellar residue (RII) accounted for about 18.5% of the total N regardless of treatment. Non-protein, non amino acid N concentrations were greatest under 110 N water stress conditions. Nitrate N concentrations contributed to less than one percent of the non-protein non-amino acid nitrogen.Component analysis of N in tall fescue, empirically determined as CP, elucidated the redistribution of nitrogenous constituents in response to N fertilization and water regime which may alter nutritive quality and/or plant survival. Accumulation of low molecular weight N compounds under water stress conditions could relate to animal health and fungal endophyte problems associated with tall fescue.

Evaluation of switchgrass entries for acid soil tolerance

Abstract Crop and forage yields are significantly reduced by strong soil acidity throughout much of the northeastern United States. Switchgrass (Panicum virgatum L.) is a valuable perennial warm‐season pasture species generally regarded as tolerant to stress conditions, i.e., infertile, dry, or low pH soils; however, switchgrass has not been studied for variability in acid soil tolerance. The objectives of this study were (a) to compare the responses of different switchgrass entries to soil acidity, and (b) to identify selected agribotanical trait response to unlimed (‐L) and limed (+L) soil. Sixteen entries (cultivars, germplasms, and breeding populations) were studied in short‐ and meso‐term experiments. Unlimed (pH 4.9) and limed (pH 5.9) treatments of a sandy loam soil (Typic Dystrochrept) were used in both experiments. Switchgrass seedlings were exceptionally tolerant of soil acidity in the short‐term experiment. In the meso‐term experiment, acid soil stress significantly reduced all agribotanical tr...