Illinois Field Crop Applicators Practice Test

When a hybrid has no major defense mechanisms to a disease but the yield loss is less compared to a susceptible hybrid, what is this hybrid called?

1. Resistant

2. Tolerant

3. Susceptible

4. Immune

The correct answer is: Tolerant

The correct term for a hybrid that exhibits less yield loss compared to a susceptible hybrid, despite lacking major defense mechanisms to a disease, is referred to as tolerant. Tolerance in plants indicates that they can withstand the stress or damage caused by the disease without significant yield reduction, even though they may still be affected to some extent. In contrast, a resistant hybrid would have specific adaptations that protect it from the disease completely or significantly reduce infection rates. On the other hand, a susceptible hybrid would experience considerable yield loss when exposed to the disease due to its inability to cope with the pathogen. Lastly, an immune plant would not be affected by the disease at all, meaning that no symptoms would arise, and there would be no yield loss. Thus, in this context, tolerance describes the hybrid's ability to endure disease pressure while still maintaining better yield than the more susceptible counterpart.