During which period is resistance from partially resistant varieties typically activated?

• A. Immediately after planting
• B. 10-14 days after emergence
• C. At the time of flowering
• D. During harvest

Answer: (B)

Resistance from partially resistant varieties is typically activated 10-14 days after emergence. This timeframe aligns with the critical growth stage when plants are interacting with potential pathogens in the soil and are beginning to establish their defenses.

During the early growth stages, the plants are primarily focused on establishing roots and foliage, and they may not yet have activated the mechanisms required to fend off diseases effectively. However, as the plants progress to around two weeks after emergence, they are more capable of activating their defense responses. This is when many alleles associated with partial resistance become more effective in deterring or managing pathogen attacks.

Timing is crucial in understanding plant resistance. Options suggesting that resistance activates immediately after planting do not account for the developmental lag in plants. Additionally, activation only at flowering or during harvest overlooks critical stages of plant growth where the activation of resistance mechanisms can play a significant role in overall plant health. Thus, the period of 10-14 days after emergence represents the right context for observing increased resistance in partially resistant varieties.