Step 1: Recall the fact needed:
Popular titles are given to fodder crops for their quality. Lucerne (alfalfa) is the one known as the queen of fodder because it gives many cuts and is rich in protein.
Step 2: Test the choice numbered 1.
Choice 1, berseem, is well known as the king of fodders, a different title.
Step 3: Test the choice numbered 2.
Choice 2, lucerne, stays green for years, gives many cuts and is rich in protein. It is named queen of fodder. This is the match.
Step 4: Test the choice numbered 3.
Choice 3, cowpea, is a rainy season legume fodder with no royal title.
Step 5: Test the choice numbered 4.
Choice 4, stylo, is a pasture legume for poor soils and has no royal title.
Final Answer:
Lucerne is the correct answer.
\[\boxed{2}\]