Concept:
Grain storage structures are used to protect harvested grains from moisture, insects, rodents and other losses.
Step 1: Different varieties of grains should be stored separately to avoid mixing.
Step 2: Cylindrical grain bins are suitable for storing grains in separate compartments or units.
Step 3: Such bins are useful for organized storage of different grain lots.
Step 4: Silos are generally used for bulk storage, while Pusa bins are improved low-cost structures.
Step 5: Therefore, the correct answer is cylindrical grain bins.
\[
\boxed{\text{Cylindrical grain bins}}
\]