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Title: EVIDENCE FOR COPPER BINDING BY EXTRACELLULAR ROOT EXUDATES OF TALL FESCUE BUT NOT PERENNIAL RYEGRASS INFECTED WITH NEOTYPHODIUM SPP. FUNGAL ENDOPHYTES

Author
item MALINOWSKI, D - TEXAS A&M UNIVERSITY
item ZUO, H - TEXAS A&M UNIVERSITY
item Belesky, David
item ALLOUSH, G - TISHREEN UNIVERSITY

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2004
Publication Date: 1/11/2005
Citation: Malinowski, D.P., Zuo, H., Belesky, D.P., Alloush, G.A. 2005. Evidence for copper binding by extracellular root exudates of tall fescue but not perennial ryegrass infected with neotyphodium spp. fungal endophytes. Plant and Soil Journal, 267:1-12.

Interpretive Summary: Tall fescue is a major forage grass grown throughout the southeastern US and is adapted over most of the US east of the Mississippi River. The grass is host to an endophytic fungus that has significant influence of the ecological function of host in natural and agricultural situations. Emergent evidence suggested that infection by endophyte (E+) provided host plants with means to grow and persist under conditions of marginal water and nutrient supply whereas plants lacking endophyte (E-) were likely to be at a competitive and adaptive disadvantage. Enhanced ecological fitness may involve grazing deterrence (through production of anti-herbivory compounds), which allows greater survival of plant storage tissues, primarily stem bases, growing points and roots. Responses indicate a complex relationship between the host plant and endophytic mutualist such that endophyte has both direct and indirect effects on plant production and persistence.

Technical Abstract: Copper (Cu) concentration in tall fescue (Festuca arundinacea Schreb.) herbage could be affected by N. coenophialum-endophyte infection, resulting in low serum Cu and immune-related disorders in grazing animals. We postulate that soil phosphorus (P) availability influences release and activity of root exudates of endophyte-infected (E+) grasses. The exudates immobilize Cu, restricting its availability to the plant. Tall fescue cultivars Grasslands Flecha and Jesup infected with a novel endophyte AR542 do not produce ergot alkaloids, perennial ryegrass (Lolium perenne L.) cultivars Aries and Quartet infected with a novel endophyte AR1 do not produce lolitrem B. These associations and their non-infected forms were grown in nutrient solution at P concentrations of 1.0 (P+) and 0.0 mM (P'). The Cu2+-binding activity of extracellular root exudates, concentrations of Cu and other heavy metals in roots and shoots were determined. Root exudates of AR542-infected tall fescue cultivars had higher Cu2+-binding activity, as shown by lower concentration of free Cu2+, than E- plants (0.096 vs. 0.188 'M Cu2+ g-1 root DM, respectively) when grown in P' nutrient solution. The Cu2+-binding activity of perennial ryegrass root exudates 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 'M Cu2+ g-1 root DM). Copper binding by root exudates did not influence Cu concentrations in shoots of either grass species grown in nutrient culture, but may influence Cu accumulation by field-grown, E+ tall fescue where P-limiting growth conditions occur.