Which best describes the role of endophytes in some tall fescues and how they influence pest resistance?

• A. Endophytes produce alkaloids that deter pests and herbivores, enhancing pest resistance; effects can vary by cultivar and may impact grazing animals if used on forage-type grasses
• B. Endophytes always harm grazing animals
• C. Endophytes have no effect on pest resistance
• D. Endophytes completely suppress root growth

Answer: (A)

Endophytes in tall fescue produce alkaloids that act as natural deterrents to insects and grazing herbivores, giving the grass added pest resistance. The presence and amount of these alkaloids depend on the specific endophyte strain and the cultivar, so some combinations offer strong pest defense while others can affect grazing animals if consumed in high levels. That balance is why breeders develop forage types with endophytes that reduce livestock risks while maintaining pest resistance. The other statements don’t fit: endophytes don’t always harm grazing animals, they do contribute to pest resistance, and they don’t merely suppress root growth.