A disease resistant cultivar may still become infected when

• A. Plants become physically stressed by overwatering or nutrient deficiencies.
• B. There is no disease present.
• C. The cultivar is grown under ideal conditions.
• D. It is treated with broad-spectrum pesticides.

Answer: (A)

A disease-resistant cultivar can still get infected when the plant is stressed. When plants are under abiotic stress—like overwatering that robs roots of oxygen or nutrient deficiencies that weaken growth—their defenses are compromised and resources are diverted to coping with the stress. This reduction in vigor and defense makes it easier for pathogens to invade and establish infection, even though the cultivar carries resistance traits. In contrast, under no disease presence or ideal conditions, infection is unlikely, and broad-spectrum pesticides don’t inherently cause or prevent infection—the key factor is the plant’s stressed state that allows a pathogen to take hold.