Present day maize developed is resistance to stem borers due to

Options

A. Low sugar content
B. Low nitrogen content
C. High aspartic acid
D. More than two

Answer

**Step-by-Step Solution:**

1. **Understanding the Problem**: The question asks about how present-day maize has developed resistance to stem borers, which are insects that damage the maize plant by destroying its stem.

2. **Identifying Resistance Mechanisms**: Plants can develop resistance to pests through three main mechanisms:
- **Morphological**: Changes in structure to prevent insect attacks.
- **Biochemical**: Production of harmful chemicals that deter pests.
- **Physiological**: Alterations in physiological processes to enhance protection.

3. **Analyzing the Options**:
- **Option 1: Low Sugar Content**: Reducing sugar content can deter stem borers since these insects may rely on sugars for energy.
- **Option 2: Low Nitrogen Content**: Lower nitrogen levels can affect the nutritional quality of the plant, making it less appealing to pests.
- **Option 3: High Aspartic Acid**: Increasing aspartic acid can produce biochemical defenses that may be toxic or deterrent to stem borers.

4. **Conclusion**: Since all three conditions (low sugar content, low nitrogen content, and high aspartic acid) contribute to the resistance of maize against stem borers, the correct answer is **Option 4: More than 2**.

**Final Answer**: The present-day maize developed resistance to stem borers due to more than two factors, specifically low sugar content, low nitrogen content, and high aspartic acid.

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