The biggest constraint of plant breeding is

Options

A. Availbility of desirable gene crop and its wild relatives
B. infrastructure
C. Traned manpower
D. Transfer of genes from unelated sources

Explanation

### Step-by-Step Solution:

1. **Understanding Plant Breeding**:
- Plant breeding is the process of selecting and crossing plants to produce new varieties with desirable traits. This involves introducing genes from wild relatives or other species into cultivated plants.

2. **Identifying Constraints**:
- A constraint in plant breeding refers to the limitations or challenges that breeders face while trying to achieve their goals.

3. **Key Constraint**:
- The biggest constraint in plant breeding is the availability of desirable genes. Breeders often need specific genes that confer traits such as disease resistance, drought tolerance, or improved yield.

4. **Risks Involved**:
- When breeders source genes from wild varieties, there is a risk that these genes may carry undesirable traits, such as susceptibility to diseases. This can lead to unintended consequences in the cultivated plants.

5. **Conclusion**:
- Therefore, the biggest constraint in plant breeding is the challenge of finding and utilizing desirable genes that are not associated with negative traits, ensuring that the new plant varieties are healthy and productive.