Step 1: Understanding the Desert Development Program.
The Desert Development Program (DDP) was initiated by the Government of India in 1977-78 with the goal of addressing desertification, land degradation, and ecological restoration in arid and semi-arid regions, particularly in Rajasthan.
Step 2: Conclusion.
The Desert Development Program was initiated in 1977-78.
Final Answer:
\[
\boxed{2. 1977-78}
\]