Involvement of Novel Neotyphodium-Endophytes in Copper Acquisition
in Tall Fescue and Perennial Ryegrass
Research Hypothesis
Recent evidence suggests reduced copper (Cu) concentration in forage of endophyte-infected (E+) when compared with noninfected (E-) tall fescue, lowered blood Cu status, and depression of Cu-related immune function in steers grazing E+ tall fescue. This phenomenon may be related to chemical changes in the rhizosphere of E+ tall fescue affecting mineral acquisition. Few studies examined the effects of endophyte infection on mineral uptake and concentration in grasses. One of the important findings was exudation of compounds with P-solubilizing activity by tall fescue roots in response to endophyte presence in shoots. Those exudates were identified as phenolic-like compounds with iron (Fe3+) reducing activity. These compounds are most likely involved in aluminum (Al) chelation on root surfaces of E+ tall fescue when compared with E– plants.
We hypothesized that increased exudation of phenolic or other compounds by roots of cool-season perennial grasses in response to endophyte infection might be the reason for Cu immobilization in the rhizosphere and thus, reduced Cu concentration in forage. This hypothesis is based on the fact that phenolic compounds can effectively chelate Cu. For example, resveratrol, a phenolic compound commonly found in E+ cool-season grasses, is one of the most potent known Cu chelators, but does not chelate Fe.
The objectives of our study were: 1) to determine the relationship between endophyte infection of tall fescue and perennial ryegrass and Cu2+-binding activity by extracellular root exudates; and 2) to determine the relationship between Cu2+-binding activity of extracellular root exudates and Cu concentration in shoot tissues as a function of endophyte infection.
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General view of the hydroponic system |
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Roots must be constantly areated to ensure normal growth |
Results
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