Name any three factors for which crop variety improvement is done and explain each of them.

Explanation

**Step-by-Step Text Solution:**

1. **High Yield Varieties**: One of the primary factors for crop variety improvement is the development of high-yield varieties. This involves selecting and breeding plants that can produce a greater quantity of crops per unit area. High-yield varieties are often developed to be disease-resistant, which helps ensure that they can survive and thrive despite the presence of pests and diseases. Additionally, these plants may be enhanced to have higher levels of essential nutrients and proteins, making them more valuable in the market.

2. **Stress Tolerance**: Another important factor is the development of stress-tolerant varieties. This means breeding plants that can withstand adverse environmental conditions such as drought, high temperatures, or excessive sunlight. By enhancing the plant's ability to cope with these stressors, farmers can reduce crop losses and ensure stable production even in challenging climates. For example, crops that can survive with low rainfall are crucial in regions prone to drought.

3. **Desirable Agronomic Traits**: The third factor involves developing varieties with desirable agronomic traits. This includes selecting for characteristics that promote healthy growth and high production levels, such as semi-dwarf stature, which can lead to better yield stability and reduced lodging (falling over). These traits are often cultivated in controlled environments (in vitro conditions) to ensure that the plants exhibit the desired characteristics effectively.