Tall Fescue Online Monograph

Copper concentrations were less in E+ than in E- plants (Dennis et al., 1998), with deficiency expressed as decreased Cu-related immune function (Saker et al., 1998). Cattle grazing E+ tall fescue showed symptoms of deficiency (coat condition and hair color) by the end of the grazing season in Kansas (Coffey et al., 1992). Copper concentrations in KY-31 tall fescue grown in Virginia and Mississippi differed as a function of endophyte infection (Allen et al., 1997). Steers consuming E+ tall fescue grown in Virginia had lower serum Cu concentrations than steers fed E- plants, while no differences in serum Cu were observed for steers fed tall fescue grown in Mississippi. Apparently, Cu uptake is influenced by endophyte and soil composition (see Chapter 12 and Chapter 16). Endophyte infected plants seem to restrict translocation of potentially toxic metal ions to aboveground tissues. However, low concentrations of essential micronutrients and bioavailability factors could raise concerns about nutritive quality in extensively managed tall fescue pasture.

Tall fescue typically harbors endophyte genotypes (strains) whose alkaloids elicit toxicoses in grazers; however, the presence of endophyte could confer adaptive benefits to the plant‒endophyte association. Some endophytes do not cause toxicity or produce toxic alkaloids when removed from their natural host and grown in a different plant genotype. One such novel endophyte strain, AR542, when inserted into Jesup tall fescue increased Cu²⁺ binding activity by root exudates of tall fescue when grown in a P deficient nutrient solution. Under experimental conditions, the phenomenon did not appear to interfere with Cu accumulation in shoot tissues, but under field conditions, where Cu concentrations in soil are much lower and P may easily limit growth, the novel endophyte may have reduced Cu availability to the plant (Malinowski et al., 2003). This process may interfere with Cu uptake under field conditions and diminish concentrations of minerals antagonistic to Cu, such as Mo, thereby reducing Cu absorption from forage by grazing animals.